Multimessenger Signatures of Massive Black Holes in Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Bellovary, Jillian; Cleary, Colleen; Tremmel, Michael; Munshi, Ferah

2018-01-01

Inspired by the recent discovery of several nearby dwarf galaxies hosting active galactic nuclei, we present results from a series of cosmological hydrodynamic simulations focusing on dwarf galaxies which host supermassive black holes (SMBHs). Cosmological simulations are a vital tool for predicting SMBH populations and merger events which will eventually be observed by LISA. Dwarf galaxies are the most numerous in the universe, so even though the occupation fraction of SMBHs in dwarfs is less than unity, their contribution to the gravitational wave background could be non-negligible. We find that electromagnetic signatures from SMBH accretion are not common among most SMBH-hosting dwarfs, but the gravitational wave signatures can be substantial. The most common mass ratio for SMBH mergers in low-mass galaxy environments is ~1:20, which is an unexplored region of gravitational waveform parameter space. We discuss the occupation fraction of SMBHs in low-mass galaxies as well as differences in field and satellite populations, providing clues to search for and characterize these elusive giants lurking in the dwarfs.

GALAXY EVOLUTION. An over-massive black hole in a typical star-forming galaxy, 2 billion years after the Big Bang.

PubMed

Trakhtenbrot, Benny; Urry, C Megan; Civano, Francesca; Rosario, David J; Elvis, Martin; Schawinski, Kevin; Suh, Hyewon; Bongiorno, Angela; Simmons, Brooke D

2015-07-10

Supermassive black holes (SMBHs) and their host galaxies are generally thought to coevolve, so that the SMBH achieves up to about 0.2 to 0.5% of the host galaxy mass in the present day. The radiation emitted from the growing SMBH is expected to affect star formation throughout the host galaxy. The relevance of this scenario at early cosmic epochs is not yet established. We present spectroscopic observations of a galaxy at redshift z = 3.328, which hosts an actively accreting, extremely massive BH, in its final stages of growth. The SMBH mass is roughly one-tenth the mass of the entire host galaxy, suggesting that it has grown much more efficiently than the host, contrary to models of synchronized coevolution. The host galaxy is forming stars at an intense rate, despite the presence of a SMBH-driven gas outflow. Copyright © 2015, American Association for the Advancement of Science.

POWERFUL RADIO EMISSION FROM LOW-MASS SUPERMASSIVE BLACK HOLES FAVORS DISK-LIKE BULGES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, J.; Xu, Y.; Xu, D. W.

The origin of spin of low-mass supermassive black holes (SMBHs) is still a puzzle at present. We report here a study on the host galaxies of a sample of radio-selected nearby ( z < 0.05) Seyfert 2 galaxies with a BH mass of 10{sup 6–7} M{sub ⊙}. By modeling the SDSS r -band images of these galaxies through a two-dimensional bulge+disk decomposition, we identify a new dependence of SMBH's radio power on host bulge surface brightness profiles, in which more powerful radio emission comes from an SMBH associated with a more disk-like bulge. This result means low-mass and high-mass SMBHsmore » are spun up by two entirely different modes that correspond to two different evolutionary paths. A low-mass SMBH is spun up by a gas accretion with significant disk-like rotational dynamics of the host galaxy in the secular evolution, while a high-mass one by a BH–BH merger in the merger evolution.« less

Preferential Accretion in the Supermassive Black Holes of Milky Way-size Galaxies Due to Direct Feeding by Satellites

NASA Astrophysics Data System (ADS)

Sanchez, N. Nicole; Bellovary, Jillian M.; Holley-Bockelmann, Kelly; Tremmel, Michael; Brooks, Alyson; Governato, Fabio; Quinn, Tom; Volonteri, Marta; Wadsley, James

2018-06-01

Using a new, high-resolution cosmological hydrodynamic simulation of a Milky Way-type (MW-type) galaxy, we explore how a merger-rich assembly history affects the mass budget of the central supermassive black hole (SMBH). We examine a MW-mass halo at the present epoch whose evolution is characterized by several major mergers to isolate the importance of merger history on black hole (BH) accretion. This study is an extension of Bellovary et al. (2013), which analyzed the accretion of high mass, high-redshift galaxies and their central BHs, and found that the gas content of the central BH reflects what is accreted by the host galaxy halo. In this study, we find that a merger-rich galaxy will have a central SMBH preferentially fed by gas accreted through mergers. Moreover, we find that the gas composition of the inner ∼10 kpc of the galaxy can account for the increase of merger-accreted gas fueling the SMBH. Through an investigation of the angular momentum of the gas entering the host and its SMBH, we determine that gas accreted through mergers enters the galaxy halo with lower angular momentum compared to smooth accretion, partially accounting for the preferential fueling witnessed in the SMBH. In addition, the presence of mergers, particularly major mergers, also helps funnel low angular momentum gas more readily to the center of the galaxy. Our results imply that galaxy mergers play an important role in feeding the SMBH in MW-type galaxies with merger-rich histories.

The Megamaser Cosmology Project. X. High-resolution Maps and Mass Constraints for SMBHs

NASA Astrophysics Data System (ADS)

Zhao, W.; Braatz, J. A.; Condon, J. J.; Lo, K. Y.; Reid, M. J.; Henkel, C.; Pesce, D. W.; Greene, J. E.; Gao, F.; Kuo, C. Y.; Impellizzeri, C. M. V.

2018-02-01

We present high-resolution (submas) Very Long Baseline Interferometry maps of nuclear H2O megamasers for seven galaxies. In UGC 6093, the well-aligned systemic masers and high-velocity masers originate in an edge-on, flat disk and we determine the mass of the central supermassive black holes (SMBH) to be M SMBH = 2.58 × 107 M ⊙ (±7%). For J1346+5228, the distribution of masers is consistent with a disk, but the faint high-velocity masers are only marginally detected, and we constrain the mass of the SMBH to be in the range (1.5–2.0) × 107 M ⊙. The origin of the masers in Mrk 1210 is less clear, as the systemic and high-velocity masers are misaligned and show a disorganized velocity structure. We present one possible model in which the masers originate in a tilted, warped disk, but we do not rule out the possibility of other explanations including outflow masers. In NGC 6926, we detect a set of redshifted masers, clustered within a parsec of each other, and a single blueshifted maser about 4.4 pc away, an offset that would be unusually large for a maser disk system. Nevertheless, if it is a disk system, we estimate the enclosed mass to be M SMBH < 4.8 × 107 M ⊙. For NGC 5793, we detect redshifted masers spaced about 1.4 pc from a clustered set of blueshifted features. The orientation of the structure supports a disk scenario as suggested by Hagiwara et al. We estimate the enclosed mass to be M SMBH < 1.3 × 107 M ⊙. For NGC 2824 and J0350‑0127, the masers may be associated with parsec- or subparsec-scale jets or outflows.

Visibility of Active Galactic Nuclei in the Illustris Simulation

NASA Astrophysics Data System (ADS)

Hutchinson-Smith, Tenley; Kelley, Luke; Moreno, Jorge; Hernquist, Lars; Illustris Collaboration

2018-01-01

Active galactic nuclei (AGN) are the very bright, luminous regions surrounding supermassive black holes (SMBH) located at the centers of galaxies. Supermassive black holes are the source of AGN feedback, which occurs once the SMBH reaches a certain critical mass. Almost all large galaxies contain a SMBH, but SMBH binaries are extremely rare. Finding these binary systems are important because it can be a source of gravitational waves if the two SMBH collide. In order to study supermassive black holes, astronomers will often rely on the AGN’s light in order to locate them, but this can be difficult due to the extinction of light caused by the dust and gas surrounding the AGN. My research project focuses on determining the fraction of light we can observe from galactic centers using the Illustris simulation, one of the most advanced cosmological simulations of the universe which was created using a hydrodynamic code and consists of a moving mesh. Measuring the fraction of light observable from galactic centers will help us know what fraction of the time we can observe dual and binary AGN in different galaxies, which would also imply a binary SMBH system. In order to find how much light is being blocked or scattered by the gas and dust surrounding the AGN, we calculated the density of the gas and dust along the lines of sight. I present results including the density of gas along different lines of sight and how it correlates with the image of the galaxy. Future steps include taking an average of the column densities for all the galaxies in Illustris and studying them as a function of galaxy type (before merger, during merger, and post-merger), which will give us information on how this can also affect the AGN luminosity.

SPOON-FEEDING GIANT STARS TO SUPERMASSIVE BLACK HOLES: EPISODIC MASS TRANSFER FROM EVOLVING STARS AND THEIR CONTRIBUTION TO THE QUIESCENT ACTIVITY OF GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacLeod, Morgan; Ramirez-Ruiz, Enrico; Grady, Sean

2013-11-10

Stars may be tidally disrupted if, in a single orbit, they are scattered too close to a supermassive black hole (SMBH). Tidal disruption events are thought to power luminous but short-lived accretion episodes that can light up otherwise quiescent SMBHs in transient flares. Here we explore a more gradual process of tidal stripping where stars approach the tidal disruption radius by stellar evolution while in an eccentric orbit. After the onset of mass transfer, these stars episodically transfer mass to the SMBH every pericenter passage, giving rise to low-level flares that repeat on the orbital timescale. Giant stars, in particular,more » will exhibit a runaway response to mass loss and 'spoon-feed' material to the black hole for tens to hundreds of orbital periods. In contrast to full tidal disruption events, the duty cycle of this feeding mode is of order unity for black holes M{sub bh} ∼> 10{sup 7} M{sub ☉}. This mode of quasi-steady SMBH feeding is competitive with indirect SMBH feeding through stellar winds, and spoon-fed giant stars may play a role in determining the quiescent luminosity of local SMBHs.« less

Gas Cloud Accretion onto the SMBH SgrA* and Formation of Jet 4

NASA Astrophysics Data System (ADS)

Nishiyama, Shogo

2015-06-01

A dense gas cloud was detected to be rapidly approaching the Galactic supermassive black hole (SMBH) Sgr A*, and was 1,600 Schwarzschild radii from the SMBH at the pericenter of its eccentric orbit in Mar 2014. Ongoing tidal disruption has been observed, and cloud fragments are expected to accrete onto the SMBH on dynamical timescales, suggesting a jet formation in the following years. So we are carrying out daily monitoring observations of Sgr A* in near-infrared and radio wavelengths, and we propose quick follow-up observations with Subaru/Gemini. Br-gamma line emission maps obtained with Gemini/NIFS will be used to fine tune our 3D simulation to estimate how much mass accretes, and when the fragments accrete onto the SMBH. Polarimetric and astrometric signals from a jet taken with Subaru/HiCIAO and KaVA will be compared with the finely tuned simulation to understand the timescale of jet formation, and to investigate the correlation between the accreted mass of the cloud fragments and a luminosity of the newly-formed jet. Spectroscopic and imaging observations from 1.6 - 11 mum (Subaru/IRCS, COMICS) will also be conducted to understand processes responsible for near to mid-infrared emission during the accretion event.

Off the beaten path: a new approach to realistically model the orbital decay of supermassive black holes in galaxy formation simulations

NASA Astrophysics Data System (ADS)

Tremmel, M.; Governato, F.; Volonteri, M.; Quinn, T. R.

2015-08-01

We introduce a sub-grid force correction term to better model the dynamical friction experienced by a supermassive black hole (SMBH) as it orbits within its host galaxy. This new approach accurately follows an SMBH's orbital decay and drastically improves over commonly used `advection' methods. The force correction introduced here naturally scales with the force resolution of the simulation and converges as resolution is increased. In controlled experiments, we show how the orbital decay of the SMBH closely follows analytical predictions when particle masses are significantly smaller than that of the SMBH. In a cosmological simulation of the assembly of a small galaxy, we show how our method allows for realistic black hole orbits. This approach overcomes the limitations of the advection scheme, where black holes are rapidly and artificially pushed towards the halo centre and then forced to merge, regardless of their orbits. We find that SMBHs from merging dwarf galaxies can spend significant time away from the centre of the remnant galaxy. Improving the modelling of SMBH orbital decay will help in making robust predictions of the growth, detectability and merger rates of SMBHs, especially at low galaxy masses or at high redshift.

The Supermassive Black Hole—Galaxy Connection

NASA Astrophysics Data System (ADS)

King, Andrew

2014-09-01

The observed scaling relations imply that supermassive black holes (SMBH) and their host galaxies evolve together. Near-Eddington winds from the SMBH accretion discs explain many aspects of this connection. The wind Eddington factor should be in the range ˜1-30. A factor give black hole winds with velocities v˜0.1 c, observable in X-rays, just as seen in the most extreme ultrafast outflows (UFOs). Higher Eddington factors predict slower and less ionized winds, observable in the UV, as in BAL QSOs. In all cases the wind must shock against the host interstellar gas and it is plausible that these shocks should cool efficiently. There is detailed observational evidence for this in some UFOs. The wind sweeps up the interstellar gas into a thin shell and propels it outwards. For SMBH masses below a certain critical ( M- σ) value, all these outflows eventually stall and fall back, as the Eddington thrust of the wind is too weak to drive the gas to large radii. But once the SMBH mass reaches the critical M- σ value the global character of the outflow changes completely. The wind shock is no longer efficiently cooled, and the resulting thermal expansion drives the interstellar gas far from the black hole, which is unlikely to grow significantly further. Simple estimates of the maximum stellar bulge mass M b allowed by self-limited star formation show that the SMBH mass is typically about 10-3 M b at this point, in line with observation. The expansion-driven outflow reaches speeds v out≃1200 km s-1 and drives rates in cool (molecular) gas, giving a typical outflow mechanical energy L mech≃0.05 L Edd, where L Edd is the Eddington luminosity of the central SMBH. This is again in line with observation. These massive outflows may be what makes galaxies become red and dead, and can have several other potentially observable effects. In particular they have the right properties to enrich the intergalactic gas with metals. Our current picture of SMBH-galaxy coevolution is still incomplete, as there is no predictive theory of how the hole accretes gas from its surroundings. Recent progress in understanding how large-scale discs of gas can partially cancel angular momentum and promote dynamical infall offers a possible way forward.

Classification of Stellar Orbits in Axisymmetric Galaxies

NASA Astrophysics Data System (ADS)

Li, Baile; Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood

2015-09-01

It is known that two supermassive black holes (SMBHs) cannot merge in a spherical galaxy within a Hubble time; an emerging picture is that galaxy geometry, rotation, and large potential perturbations may usher the SMBH binary through the critical three-body scattering phase and ultimately drive the SMBH to coalesce. We explore the orbital content within an N-body model of a mildly flattened, non-rotating, SMBH-embedded elliptical galaxy. When used as the foundation for a study on the SMBH binary coalescence, the black holes bypassed the binary stalling often seen within spherical galaxies and merged on gigayear timescales. Using both frequency-mapping and angular momentum criteria, we identify a wealth of resonant orbits in the axisymmetric model, including saucers, that are absent from an otherwise identical spherical system and that can potentially interact with the binary. We quantified the set of orbits that could be scattered by the SMBH binary, and found that the axisymmetric model contained nearly six times the number of these potential loss cone orbits compared to our equivalent spherical model. In this flattened model, the mass of these orbits is more than three times that of the SMBH, which is consistent with what the SMBH binary needs to scatter to transition into the gravitational wave regime.

CLASSIFICATION OF STELLAR ORBITS IN AXISYMMETRIC GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Baile; Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood, E-mail: baile.li@vanderbilt.edu, E-mail: k.holley@vanderbilt.edu, E-mail: khanfazeel.ist@gmail.com

2015-09-20

It is known that two supermassive black holes (SMBHs) cannot merge in a spherical galaxy within a Hubble time; an emerging picture is that galaxy geometry, rotation, and large potential perturbations may usher the SMBH binary through the critical three-body scattering phase and ultimately drive the SMBH to coalesce. We explore the orbital content within an N-body model of a mildly flattened, non-rotating, SMBH-embedded elliptical galaxy. When used as the foundation for a study on the SMBH binary coalescence, the black holes bypassed the binary stalling often seen within spherical galaxies and merged on gigayear timescales. Using both frequency-mapping andmore » angular momentum criteria, we identify a wealth of resonant orbits in the axisymmetric model, including saucers, that are absent from an otherwise identical spherical system and that can potentially interact with the binary. We quantified the set of orbits that could be scattered by the SMBH binary, and found that the axisymmetric model contained nearly six times the number of these potential loss cone orbits compared to our equivalent spherical model. In this flattened model, the mass of these orbits is more than three times that of the SMBH, which is consistent with what the SMBH binary needs to scatter to transition into the gravitational wave regime.« less

Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rantala, Antti; Pihajoki, Pauli; Johansson, Peter H.

We present KETJU, a new extension of the widely used smoothed particle hydrodynamics simulation code GADGET-3. The key feature of the code is the inclusion of algorithmically regularized regions around every supermassive black hole (SMBH). This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving the dynamics of SMBHs, SMBH binaries, and surrounding stellar systems at subparsec scales. The KETJU code includes post-Newtonian terms in the equations of motions of the SMBHs, which enables a new SMBH merger criterion based on the gravitational wave coalescence timescale, pushing the merger separation of SMBHs down to ∼0.005 pc. Wemore » test the performance of our code by comparison to NBODY7 and rVINE. We set up dynamically stable multicomponent merger progenitor galaxies to study the SMBH binary evolution during galaxy mergers. In our simulation sample the SMBH binaries do not suffer from the final-parsec problem, which we attribute to the nonspherical shape of the merger remnants. For bulge-only models, the hardening rate decreases with increasing resolution, whereas for models that in addition include massive dark matter halos, the SMBH binary hardening rate becomes practically independent of the mass resolution of the stellar bulge. The SMBHs coalesce on average 200 Myr after the formation of the SMBH binary. However, small differences in the initial SMBH binary eccentricities can result in large differences in the SMBH coalescence times. Finally, we discuss the future prospects of KETJU, which allows for a straightforward inclusion of gas physics in the simulations.« less

Supermassive black holes and their feedback effects in the IllustrisTNG simulation

NASA Astrophysics Data System (ADS)

Weinberger, Rainer; Springel, Volker; Pakmor, Rüdiger; Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Marinacci, Federico; Naiman, Jill; Torrey, Paul; Hernquist, Lars

2018-06-01

We study the population of supermassive black holes (SMBHs) and their effects on massive central galaxies in the IllustrisTNG cosmological hydrodynamical simulations of galaxy formation. The employed model for SMBH growth and feedback assumes a two-mode scenario in which the feedback from active galactic nuclei occurs through a kinetic, comparatively efficient mode at low accretion rates relative to the Eddington limit, and in the form of a thermal, less efficient mode at high accretion rates. We show that the quenching of massive central galaxies happens coincidently with kinetic-mode feedback, consistent with the notion that active supermassive black cause the low specific star formation rates observed in massive galaxies. However, major galaxy mergers are not responsible for initiating most of the quenching events in our model. Up to black hole masses of about 108.5 M⊙, the dominant growth channel for SMBHs is in the thermal mode. Higher mass black holes stay mainly in the kinetic mode and gas accretion is self-regulated via their feedback, which causes their Eddington ratios to drop, with SMBH mergers becoming the main channel for residual mass growth. As a consequence, the quasar luminosity function is dominated by rapidly accreting, moderately massive black holes in the thermal mode. We show that the associated growth history of SMBHs produces a low-redshift quasar luminosity function and a redshift zero black hole mass - stellar bulge mass relation in good agreement with observations, whereas the simulation tends to over-predict the high-redshift quasar luminosity function.

Galaxy Rotation and Rapid Supermassive Binary Coalescence

NASA Astrophysics Data System (ADS)

Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood

2015-09-01

Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolution in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy.

GALAXY ROTATION AND RAPID SUPERMASSIVE BINARY COALESCENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holley-Bockelmann, Kelly; Khan, Fazeel Mahmood, E-mail: k.holley@vanderbilt.edu

2015-09-10

Galaxy mergers usher the supermassive black hole (SMBH) in each galaxy to the center of the potential, where they form an SMBH binary. The binary orbit shrinks by ejecting stars via three-body scattering, but ample work has shown that in spherical galaxy models, the binary separation stalls after ejecting all the stars in its loss cone—this is the well-known final parsec problem. However, it has been shown that SMBH binaries in non-spherical galactic nuclei harden at a nearly constant rate until reaching the gravitational wave regime. Here we use a suite of direct N-body simulations to follow SMBH binary evolutionmore » in both corotating and counterrotating flattened galaxy models. For N > 500 K, we find that the evolution of the SMBH binary is convergent and is independent of the particle number. Rotation in general increases the hardening rate of SMBH binaries even more effectively than galaxy geometry alone. SMBH binary hardening rates are similar for co- and counterrotating galaxies. In the corotating case, the center of mass of the SMBH binary settles into an orbit that is in corotation resonance with the background rotating model, and the coalescence time is roughly a few 100 Myr faster than a non-rotating flattened model. We find that counterrotation drives SMBHs to coalesce on a nearly radial orbit promptly after forming a hard binary. We discuss the implications for gravitational wave astronomy, hypervelocity star production, and the effect on the structure of the host galaxy.« less

WISDOM Project - III. Molecular gas measurement of the supermassive black hole mass in the barred lenticular galaxy NGC4429

NASA Astrophysics Data System (ADS)

Davis, Timothy A.; Bureau, Martin; Onishi, Kyoko; van de Voort, Freeke; Cappellari, Michele; Iguchi, Satoru; Liu, Lijie; North, Eve V.; Sarzi, Marc; Smith, Mark D.

2018-01-01

As part of the mm-Wave Interferometric Survey of Dark Object Masses project we present an estimate of the mass of the supermassive black hole (SMBH) in the nearby fast-rotating early-type galaxy NGC4429, that is barred and has a boxy/peanut-shaped bulge. This estimate is based on Atacama Large Millimeter/submillimeter Array (ALMA) cycle-2 observations of the 12CO(3-2) emission line with a linear resolution of ≈13 pc (0.18 arcsec × 0.14 arcsec). NGC4429 has a relaxed, flocculent nuclear disc of molecular gas that is truncated at small radii, likely due to the combined effects of gas stability and tidal shear. The warm/dense 12CO(3-2) emitting gas is confined to the inner parts of this disc, likely again because the gas becomes more stable at larger radii, preventing star formation. The gas disc has a low velocity dispersion of 2.2^{+0.68}_{-0.65} km s-1. Despite the inner truncation of the gas disc, we are able to model the kinematics of the gas and estimate a mass of (1.5 ± 0.1^{+0.15}_{-0.35}) × 108 M⊙ for the SMBH in NGC4429 (where the quoted uncertainties reflect the random and systematic uncertainties, respectively), consistent with a previous upper limit set using ionized gas kinematics. We confirm that the V-band mass-to-light ratio changes by ≈30 per cent within the inner 400 pc of NGC4429, as suggested by other authors. This SMBH mass measurement based on molecular gas kinematics, the sixth presented in the literature, once again demonstrates the power of ALMA to constrain SMBH masses.

Hunting a wandering supermassive black hole in the M31 halo hermitage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miki, Yohei; Mori, Masao; Kawaguchi, Toshihiro

2014-03-10

In the hierarchical structure formation scenario, galaxies enlarge through multiple merging events with less massive galaxies. In addition, the Magorrian relation indicates that almost all galaxies are occupied by a central supermassive black hole (SMBH) of mass 10{sup –3} times the mass of its spheroidal component. Consequently, SMBHs are expected to wander in the halos of their host galaxies following a galaxy collision, although evidence of this activity is currently lacking. We investigate a current plausible location of an SMBH wandering in the halo of the Andromeda galaxy (M31). According to theoretical studies of N-body simulations, some of the manymore » substructures in the M31 halo are remnants of a minor merger occurring about 1 Gyr ago. First, to evaluate the possible parameter space of the infalling orbit of the progenitor, we perform numerous parameter studies using a graphics processing unit cluster. To reduce uncertainties in the predicted position of the expected SMBH, we then calculate the time evolution of the SMBH in the progenitor dwarf galaxy from N-body simulations using the plausible parameter sets. Our results show that the SMBH lies within the halo (∼20-50 kpc from the M31 center), closer to the Milky Way than the M31 disk. Furthermore, the predicted current positions of the SMBH were restricted to an observational field of 0.°6 × 0.°7 in the northeast region of the M31 halo. We also discuss the origin of the infalling orbit of the satellite galaxy and its relationships with the recently discovered vast thin disk plane of satellite galaxies around M31.« less

The near-IR Mbh-L and Mbh-n relations

NASA Astrophysics Data System (ADS)

Vika, Marina; Driver, Simon P.; Cameron, Ewan; Kelvin, Lee; Robotham, Aaron

2012-01-01

We present near-infrared (near-IR) surface photometry (2D profiling) for a sample of 29 nearby galaxies for which supermassive black hole (SMBH) masses are constrained. The data are derived from the UKIDSS-LAS representing a significant improvement in image quality and depth over previous studies based on Two Micron All Sky Survey data. We derive the spheroid luminosity and spheroid Sérsic index for each galaxy with GALFIT3 and use these data to construct SMBH mass-bulge luminosity (Mbh-L) and SMBH-Sérsic index (Mbh-n) relations. The best-fitting K-band relation for elliptical and disc galaxies is log (Mbh/M⊙) =-0.36(±0.03)(MK+ 18) + 6.17(±0.16), with an intrinsic scatter of 0.4+0.09-0.06 dex, whilst for elliptical galaxies we find log (Mbh/M⊙) =-0.42(±0.06)(MK+ 22) + 7.5(±0.15), with an intrinsic scatter of 0.31+0.087-0.047 dex. Our revised Mbh-L relation agrees closely with the previous near-IR constraint by Graham. The lack of improvement in the intrinsic scatter in moving to higher quality near-IR data suggests that the SMBH relations are not currently limited by the quality of the imaging data but is either intrinsic or a result of uncertainty in the precise number of required components required in the profiling process. Contrary to expectation, a relation between SMBH mass and the Sérsic index was not found at near-IR wavelengths. This latter outcome is believed to be explained by the generic inconsistencies between 1D and 2D galaxy profiling which are currently under further investigation.

Gravitational wave sources from inspiralling globular clusters in the Galactic Centre and similar environments

NASA Astrophysics Data System (ADS)

Arca-Sedda, Manuel; Gualandris, Alessia

2018-07-01

We model the inspiral of globular clusters (GCs) towards a galactic nucleus harbouring a supermassive black hole (SMBH), a leading scenario for the formation of nuclear star clusters. We consider the case of GCs containing either an intermediate-mass black hole (IMBH) or a population of stellar-mass black holes (BHs), and study the formation of gravitational wave (GW) sources. We perform direct summation N-body simulations of the infall of GCs with different orbital eccentricities in the live background of a galaxy with either a shallow or steep density profile. We find that the GC acts as an efficient carrier for the IMBH, facilitating the formation of a bound pair. The hardening and evolution of the binary depends sensitively on the galaxy's density profile. If the host galaxy has a shallow profile, the hardening is too slow to allow for coalescence within a Hubble time, unless the initial cluster orbit is highly eccentric. If the galaxy hosts a nuclear star cluster, the hardening leads to coalescence by emission of GWs within 3-4 Gyr. In this case, we find an IMBH-SMBH merger rate of ΓIMBH-SMBH = 2.8 × 10-3 yr-1 Gpc3. If the GC hosts a population of stellar BHs, these are deposited close enough to the SMBH to form extreme mass ratio inspirals with a merger rate of ΓEMRI = 0.25 yr-1 Gpc3. Finally, the SMBH tidal field can boost the coalescence of stellar black hole binaries delivered from the infalling GCs. The merger rate for this merging channel is ΓBHB = 0.4-4 yr-1 Gpc3.

Stars with relativistic speeds in the Hills scenario

NASA Astrophysics Data System (ADS)

Dremova, G. N.; Dremov, V. V.; Tutukov, A. V.

2017-07-01

The dynamical capture of a binary system consisting of a supermassive black hole (SMBH) and an ordinary star in the gravitational field of a central (more massive) SMBH is considered in the three-body problem in the framework of a modified Hills scenario. The results of numerical simulations predict the existence of objects whose spatial speeds are comparable to the speed of light. The conditions for and constraints imposed on the ejection speeds realized in a classical scenario and the modified Hills scenario are analyzed. The star is modeled using an N-body approach, making it possible to treat it as a structured object, enabling estimation of the probability that the object survives when it is ejected with relativistic speed as a function of the mass of the star, the masses of both SMBHs, and the pericenter distance. It is possible that the modern kinematic classification for stars with anomalously high spatial velocities will be augmented with a new class—stars with relativistic speeds.

Major galaxy mergers and the growth of supermassive black holes in quasars.

PubMed

Treister, Ezequiel; Natarajan, Priyamvada; Sanders, David B; Urry, C Megan; Schawinski, Kevin; Kartaltepe, Jeyhan

2010-04-30

Despite observed strong correlations between central supermassive black holes (SMBHs) and star formation in galactic nuclei, uncertainties exist in our understanding of their coupling. We present observations of the ratio of heavily obscured to unobscured quasars as a function of cosmic epoch up to z congruent with 3 and show that a simple physical model describing mergers of massive, gas-rich galaxies matches these observations. In the context of this model, every obscured and unobscured quasar represents two distinct phases that result from a massive galaxy merger event. Much of the mass growth of the SMBH occurs during the heavily obscured phase. These observations provide additional evidence for a causal link between gas-rich galaxy mergers, accretion onto the nuclear SMBH, and coeval star formation.

2MASS J00423991+3017515: An Interacting Oddball or a Recoiling AGN?

NASA Astrophysics Data System (ADS)

Hogg, J. Drew; Blecha, Laura; Reynolds, Christopher S.

2017-06-01

We present deep, multiband Hubble imaging and two epochs of optical spectroscopic monitoring of a peculiar nearby (z=0.14) AGN, 2MASS J00423991+3017515. The host galaxy containing the AGN is morphologically disturbed and interacting with an unmerged companion galaxy, suggesting it has had a rich merger history. The AGN itself is spatially displaced from the apparent center of its host galaxy and the symmetric broad Hα and Hβ lines are consistently blueshifted from the narrow line emission and host galaxy absorption by Δv = 1530 km/s. The investigation is ongoing, but we put forward two hypotheses to explain the odd features of this system. First, the abnormalities could be due to separate, independent causes. Projection effects from the interaction of the two galaxies could give the appearance of a spatial offset, while complex wind dynamics from the AGN accretion disk could give rise to the kinematic shift in the broad line emission. Second, this could be a recoiling AGN. This system fits the template of an accreting supermassive black hole (SMBH) that has recently received a “kick” from the asymmetric emission of gravitational waves (GWs) following the merger of two progenitor SMBHs. SMBH mergers are a likely end-product of hierarchical structure formation and are the supermassive cousins of the stellar-mass BH mergers observed with LIGO in the GW150914 and GW151226 events. However, a SMBH merger has yet to be unambigously detected. If confirmed as a recoiling AGN, 2MASS J00423991+3017515 will provide the first evidence of this growth pathway acting in the SMBH regime.

Exploring possible relations between optical variability time scales and broad emission line shapes in AGN

NASA Astrophysics Data System (ADS)

Bon, Edi; Jovanović, Predrag; Marziani, Paola; Bon, Nataša; Otašević, Aleksandar

2018-06-01

Here we investigate the connection of broad emission line shapes and continuum light curve variability time scales of type-1 Active Galactic Nuclei (AGN). We developed a new model to describe optical broad emission lines as an accretion disk model of a line profile with additional ring emission. We connect ring radii with orbital time scales derived from optical light curves, and using Kepler's third law, we calculate mass of central supermassive black hole (SMBH). The obtained results for central black hole masses are in a good agreement with other methods. This indicates that the variability time scales of AGN may not be stochastic, but rather connected to the orbital time scales which depend on the central SMBH mass.

On the Star Formation-AGN Connection at zeta (is) approximately greater than 0.3

NASA Technical Reports Server (NTRS)

LaMassa, Stephanie M.; Heckman, T. M.; Ptak, Andrew; Urry, C. Megan

2013-01-01

Using the spectra of a sample of approximately 28,000 nearby obscured active galaxies from Data Release 7 of the Sloan Digital Sky Survey (SDSS), we probe the connection between active galactic nucleus (AGN) activity and star formation over a range of radial scales in the host galaxy. We use the extinction-corrected luminosity of the [O iii] 5007A line as a proxy of intrinsic AGN power and supermassive black hole (SMBH) accretion rate. The star formation rates (SFRs) are taken from the MPA-JHU value-added catalog and are measured through the 3 inch SDSS aperture. We construct matched samples of galaxies covering a range in redshifts. With increasing redshift, the projected aperture size encompasses increasing amounts of the host galaxy. This allows us to trace the radial distribution of star formation as a function of AGN luminosity. We find that the star formation becomes more centrally concentrated with increasing AGN luminosity and Eddington ratio. This implies that such circumnuclear star formation is associated with AGN activity, and that it increasingly dominates over omnipresent disk star formation at higher AGN luminosities, placing critical constraints on theoretical models that link host galaxy star formation and SMBH fueling. We parameterize this relationship and find that the star formation on radial scales (is) less than 1.7 kpc, when including a constant disk component, has a sub-linear dependence on SMBH accretion rate: SFR in proportion to solar mass(sup 0.36), suggesting that angular momentum transfer through the disk limits accretion efficiency rather than the supply from stellar mass loss.

THE MEGAMASER COSMOLOGY PROJECT. IX. BLACK HOLE MASSES FOR THREE MASER GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, F.; Zhao, W.; Braatz, J. A.

As part of the Megamaser Cosmology Project, we present VLBI maps of nuclear water masers toward five galaxies. The masers originate in sub-parsec circumnuclear disks. For three of the galaxies, we fit Keplerian rotation curves to estimate their supermassive black hole (SMBH) masses, and determine (2.9 ± 0.3) × 10{sup 6} M {sub ⊙} for J0437+2456, (1.7 ± 0.1) × 10{sup 7} M {sub ⊙} for ESO 558–G009, and (1.1 ± 0.2) × 10{sup 7} M {sub ⊙} for NGC 5495. In the other two galaxies, Mrk 1029 and NGC 1320, the geometry and dynamics are more complicated and preclude robust black hole mass estimates. Including our new results, we compiled amore » list of 15 VLBI-confirmed disk maser galaxies with robust SMBH mass measurements. With this sample, we confirm the empirical relation of R {sub out} ∝ 0.3 M {sub SMBH} reported in Wardle and Yusef-Zadeh. We also find a tentative correlation between maser disk outer radii and Wide-Field Infrared Survey Explorer luminosity. We find no correlations of maser disk size with X-ray 2–10 keV luminosity or [O iii] luminosity.« less

Formation of massive black holes in galactic nuclei: runaway tidal encounters

NASA Astrophysics Data System (ADS)

Stone, Nicholas C.; Küpper, Andreas H. W.; Ostriker, Jeremiah P.

2017-06-01

Nuclear star clusters (NSCs) and supermassive black holes (SMBHs) both inhabit galactic nuclei, coexisting in a range of bulge masses, but excluding each other in the largest or smallest galaxies. We propose that the transformation of NSCs into SMBHs occurs via runaway tidal captures, once NSCs exceed a certain critical central density and velocity dispersion. The bottleneck in this process is growing the first e-fold in black hole mass. The growth of a stellar mass black hole past this bottleneck occurs as tidally captured stars are consumed in repeated episodes of mass transfer at pericentre. Tidal captures may deactivate as a growth channel once the black hole mass ≳102-3 M⊙, but tidal disruption events will continue and can grow the seed SMBH to larger sizes. The runaway slows (becomes subexponential) once the seed SMBH consumes the core of its host NSC. While most of the cosmic mass density in SMBHs is ultimately produced by episodic gaseous accretion in very massive galaxies, the smallest SMBHs have probably grown from strong tidal encounters with NSC stars. SMBH seeds that grow for a time t entirely through this channel will follow simple power-law relations with the velocity dispersion, σ, of their host galaxy. In the simplest regime, it is M_\\bullet ˜ σ ^{3/2}√{M_\\star t / G} ˜ 106 M_{⊙} (σ / 50 {km s}^{-1})^{3/2}(t/10^{10} yr)^{1/2}, but the exponents and pre-factor can differ slightly depending on the details of loss cone refilling. Current tidal disruption event rates predicted from this mechanism are consistent with observations.

2MASS J00423991+3017515: An AGN On The Run?

NASA Astrophysics Data System (ADS)

Hogg, James

2016-10-01

We have discovered a peculiar AGN, 2MASS J00423991+3017515, in a local (z=0.14), disturbed galaxy whose optical spectrum has multiple broad lines that are consistently offset from the narrow line emission and host galaxy absorption by 1530 km/s. The morphology of the host galaxy and spectral properties thus suggest this AGN may be a recoiling supermassive black hole (SMBH). Gravitational-wave recoil kicks result from the coalescence of two SMBHs and have implications for the early growth of high-redshift quasars and SMBH-galaxy co-evolution. We propose high-resolution imaging in the NIR, optical, and UV with the WFC3 camera on Hubble and high-resolution X-ray imaging and spectral follow-ups with the ACIS camera on Chandra to determine if the source of the kinematically-offset broad line emission is also spatially offset from the nucleus of the host galaxy. We request 3 orbits with Hubble and 8 ksec with Chandra to conduct these follow-up observations. If a single, spatially offset AGN is detected, this source will be strongest candidate for a recoiling AGN candidate discovered to date, providing a new, indirect constraint on SMBH spin evolution and merger rates.

High-Resolution Millimeter-VLBI Imaging of the super-massive black hole candidate at the Galactic center - Sgr A*

NASA Astrophysics Data System (ADS)

Shen, Zqs

Sagittarius A* (Sgr A*), the extremely compact radio source at the Galactic center (GC), is the best candidate for the single super-massive black hole (SMBH). The accurate measurements of its mass (as a gravitational source) and size (as a radiative source) are of great importance in testing its SMBH hypothesis. Great progress has been made on determining its central dark mass of 3.7 million solar masses. Here, we will present the highest resolution VLBI imaging observations of Sgr A* made at both 7.0 and 3.5 millimeters with the Very Long Baseline Array (VLBA) plus the Green Bank Telescope (GBT) and the VLBA, respectively. Both the imaging and the model-fitting with the closure amplitudes show a consistent East-West elongated elliptical Gaussian emission. The inferred possible intrinsic emitting region is less than 1 AU at the distance of 8 kpc to GC.

Infrared-faint radio sources: a cosmological view. AGN number counts, the cosmic X-ray background and SMBH formation

NASA Astrophysics Data System (ADS)

Zinn, P.-C.; Middelberg, E.; Ibar, E.

2011-07-01

Context. Infrared-faint radio sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5σ sensitivities as low as 1 μJy. Aims: Spectral energy distribution (hereafter SED) modelling and analyses of their radio properties indicate that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3 ≤ z ≤ 6. We demonstrate some astrophysical implications of this population and compare them to predictions from models of galaxy evolution and structure formation. Methods: We compiled a list of IFRS from four deep extragalactic surveys and extrapolated the IFRS number density to a survey-independent value of (30.8 ± 15.0) deg-2. We computed the IFRS contribution to the total number of AGN in the Universe to account for the cosmic X-ray background. By estimating the black hole mass contained in IFRS, we present conclusions for the SMBH mass density in the early universe and compare it to relevant simulations of structure formation after the Big Bang. Results: The number density of AGN derived from the IFRS density was found to be ~310 deg-2, which is equivalent to a SMBH mass density of the order of 103 M⊙ Mpc-3 in the redshift range 3 ≤ z ≤ 6. This produces an X-ray flux of 9 × 10-16 W m-2 deg-2 in the 0.5-2.0 keV band and 3 × 10-15 W m-2 deg-2 in the 2.0-10 keV band, in agreement with the missing unresolved components of the Cosmic X-ray Background. To address SMBH formation after the Big Bang we invoke a scenario involving both halo gas accretion and major mergers.

HYDROSTATIC GAS CONSTRAINTS ON SUPERMASSIVE BLACK HOLE MASSES: IMPLICATIONS FOR HYDROSTATIC EQUILIBRIUM AND DYNAMICAL MODELING IN A SAMPLE OF EARLY-TYPE GALAXIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Humphrey, Philip J.; Buote, David A.; Brighenti, Fabrizio

2009-10-01

We present new mass measurements for the supermassive black holes (SMBHs) in the centers of three early-type galaxies. The gas pressure in the surrounding, hot interstellar medium (ISM) is measured through spatially resolved spectroscopy with the Chandra X-ray Observatory, allowing the SMBH mass (M {sub BH}) to be inferred directly under the hydrostatic approximation. This technique does not require calibration against other SMBH measurement methods and its accuracy depends only on the ISM being close to hydrostatic, which is supported by the smooth X-ray isophotes of the galaxies. Combined with results from our recent study of the elliptical galaxy NGCmore » 4649, this brings the number of galaxies with SMBHs measured in this way to four. Of these, three already have mass determinations from the kinematics of either the stars or a central gas disk, and hence join only a handful of galaxies with M {sub BH} measured by more than one technique. We find good agreement between the different methods, providing support for the assumptions implicit in both the hydrostatic and the dynamical models. The stellar mass-to-light ratios for each galaxy inferred by our technique are in agreement with the predictions of stellar population synthesis models assuming a Kroupa initial mass function (IMF). This concurrence implies that no more than {approx}10%-20% of the ISM pressure is nonthermal, unless there is a conspiracy between the shape of the IMF and nonthermal pressure. Finally, we compute Bondi accretion rates (M-dot{sub bondi}), finding that the two galaxies with the highest M-dot{sub bondi} exhibit little evidence of X-ray cavities, suggesting that the correlation with the active galactic nuclei jet power takes time to be established.« less

Chasing the observational signatures of seed black holes at z > 7: candidate observability

NASA Astrophysics Data System (ADS)

Valiante, Rosa; Schneider, Raffaella; Zappacosta, Luca; Graziani, Luca; Pezzulli, Edwige; Volonteri, Marta

2018-05-01

Observing the light emitted by the first accreting black holes (BHs) would dramatically improve our understanding of the formation of quasars at z > 6, possibly unveiling the nature of their supermassive black hole (SMBH) seeds. In previous works, we explored the relative role of the two main competing BH seed formation channels, Population III remnants (low-mass seeds) and direct collapse BHs (high-mass seeds), investigating the properties of their host galaxies in a cosmological context. Building on this analysis, we predict here the spectral energy distribution and observational features of low- and high-mass BH seeds selected among the progenitors of a z ˜ 6 SMBH. We derive the processed emission from both accreting BHs and stars by using the photoionization code CLOUDY, accounting for the evolution of metallicity and dust-to-gas mass ratio in the interstellar medium of the host galaxies, as predicted by the cosmological data-constrained model GAMETE/QSODUST. We show how future missions like James Webb Space Telescope (JWST) and Advanced Telescope for High Energy Astrophysics (ATHENA) will be able to detect the light coming from SMBH progenitors already at z ˜ 16. We build upon previous complementary studies and propose a method based on the combined analysis of near-infrared colours, IR excess (IRX), and UV continuum slopes (i.e. colour-colour and IRX-β diagrams) to distinguish growing seed BH host galaxies from starburst-dominated systems in JWST surveys. Sources selected through this criterion would be the best target for follow-up X-ray observations.

THE OBSERVED M-{sigma} RELATIONS IMPLY THAT SUPER-MASSIVE BLACK HOLES GROW BY COLD CHAOTIC ACCRETION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nayakshin, Sergei; King, Andrew R.; Power, Chris

We argue that current observations of M-{sigma} relations for galaxies can be used to constrain theories of super-massive black holes (SMBHs) feeding. In particular, assuming that SMBH mass is limited only by the feedback on the gas that feeds it, we show that SMBHs fed via a planar galaxy-scale gas flow, such as a disk or a bar, should be much more massive than their counterparts fed by quasi-spherical inflows. This follows from the relative inefficiency of active galactic nucleus feedback on a flattened inflow. We find that even under the most optimistic conditions for SMBH feedback on flattened inflows,more » the mass at which the SMBH expels the gas disk and terminates its own growth is a factor of several higher than the one established for quasi-spherical inflows. Any beaming of feedback away from the disk and any disk self-shadowing strengthen this result further. Contrary to this theoretical expectation, recent observations have shown that SMBHs in pseudobulge galaxies (which are associated with barred galaxies) are typically under- rather than overmassive when compared with their classical bulge counterparts at a fixed value of {sigma}. We conclude from this that SMBHs are not fed by large (100 pc to many kpc) scale gas disks or bars, most likely because such planar flows are turned into stars too efficiently to allow any SMBH growth. Based on this and other related observational evidence, we argue that most SMBHs grow by chaotic accretion of gas clouds with a small and nearly randomly distributed direction of angular momentum.« less

ON THE FATE OF THE MATTER REINSERTED WITHIN YOUNG NUCLEAR STELLAR CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hueyotl-Zahuantitla, Filiberto; Palous, Jan; Wuensch, Richard

2013-04-01

This paper presents a hydrodynamical model describing the evolution of the gas reinserted by stars within a rotating young nuclear star cluster (NSC). We explicitly consider the impact of the stellar component on the flow by means of a uniform insertion of mass and energy within the stellar cluster. The model includes the gravity force of the stellar component and a central supermassive black hole (SMBH), and accounts for the heating from the central source of radiation and the radiative cooling of the thermalized gas. By using a set of parameters typical for NSCs and SMBHs in Seyfert galaxies, ourmore » simulations show that a filamentary/clumpy structure is formed in the inner part of the cluster. This 'torus' is Compton-thick and covers a large fraction of the sky (as seen from the SMBH). In the outer parts of the cluster a powerful wind is produced that inhibits the infall of matter from larger scales and thus the NSC-SMBH interplay occurs in isolation.« less

Black Hole Masses for Type I Active Galactic Nuclei in the Chandra Cosmos Legacy Survey

NASA Astrophysics Data System (ADS)

Nagaraj, Gautam; Fornasini, Francesca; Civano, Francesca Maria

2018-01-01

Tight local relations between SMBH masses and galaxy properties have established the fundamental connection between SMBHs and their host galaxies. However, in order to better understand the coevolution of SMBHs and their host galaxies over cosmic time, we need measurements of black hole masses, AGN luminosities, and galaxy stellar masses from sizable samples of AGN covering lower luminosities than the brightest quasars spanning a wide redshift range. In this study, we report masses of the SMBHs of 224 Type I AGNs from the Chandra COSMOS Legacy Survey as determined by the line widths of Mg II 2798, Hb 4862, and Ha 6564 via scaling relations derived from reverberation mapping. Preliminary comparison with host galaxy luminosities and stellar masses suggests an increase in Eddington ratio with redshift, consistent with previous studies. In addition, our derived SMBH masses fall above the local AGN MBH--M* (galactic stellar mass) relation from Reines & Volonteri (2015), but it is still not clear whether this results from redshift evolution of the MBH--M* relation or from the incompleteness of the spectroscopic surveys available. The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

Periodic Accretion-powered Flares from Colliding EMRIs as TDE Imposters

NASA Astrophysics Data System (ADS)

Metzger, Brian D.; Stone, Nicholas C.

2017-07-01

When a main-sequence star undergoes Roche lobe overflow onto a supermassive black hole (SMBH) in a circular extreme mass ratio inspiral (EMRI), a phase of steady mass transfer ensues. Over millions of years, the binary evolves to a period minimum before reversing course and migrating outward as a brown dwarf. Because the time interval between consecutive EMRIs is comparable to the mass-transfer timescale, the semimajor axes of two consecutive mass-transferring EMRIs will cross on a radial scale of less than a few au. We show that such EMRI crossing events are inevitably accompanied by a series of mildly relativistic, grazing physical collisions between the stars. Each collision strips a small quantity of mass, primarily from the more massive star, which generally increases their radial separation to set up the next collision after a delay of decades to centuries (or longer) set by further gravitational radiation. Depending on the mass of the SMBH, this interaction can result in {N}{{c}}˜ 1{--}{10}4 gas production events of mass ˜ {M}⊙ /{N}{{c}}, thus powering a quasi-periodic sequence of SMBH accretion-powered flares over a total duration of thousands of years or longer. Although the EMRI rate is 2-3 orders of magnitude lower than the rate of tidal disruption events (TDEs), the ability of a single interacting EMRI pair to produce a large number of luminous flares—and to make more judicious use of the available stellar fuel—could make their observed rate competitive with the TDE rate, enabling them to masquerade as “TDE imposters.” Gas produced by EMRI collisions is easier to circularize than the highly eccentric debris streams produced in TDEs. We predict flares with bolometric luminosities that decay both as power laws shallower than {t}-5/3 and as decaying exponentials in time. Viscous spreading of the gaseous disks produced by the accumulation of previous mass-stripping events will place a substantial mass of gas on radial scales ≳ 10{--}100 {au} at the time of a given flare, providing a possible explanation for the “reprocessing blanket” required to explain the unexpectedly high optical luminosities of some candidate TDE flares.

X-ray emission from high-redshift miniquasars: self-regulating the population of massive black holes through global warming

NASA Astrophysics Data System (ADS)

Tanaka, Takamitsu; Perna, Rosalba; Haiman, Zoltán.

2012-10-01

Observations of high-redshift quasars at z ≳6 imply that supermassive black holes (SMBHs) with masses M≳109 M were in place less than 1 Gyr after the big bang. If these SMBHs assembled from 'seed' BHs left behind by the first stars, then they must have accreted gas at close to the Eddington limit during a large fraction (>rsim 50 per cent) of the time. A generic problem with this scenario, however, is that the mass density in M ˜ 106 M⊙ SMBHs at z ˜ 6 already exceeds the locally observed SMBH mass density by several orders of magnitude; in order to avoid this overproduction, BH seed formation and growth must become significantly less efficient in less massive protogalaxies through some form of feedback, while proceeding unabated in the most massive galaxies that formed first. Using Monte Carlo realizations of the merger and growth history of BHs, we show that X-rays from the earliest accreting BHs can provide such a feedback mechanism, on a global scale. Our calculations paint a self-consistent picture of BH-made climate change, in which the first miniquasars - among them the ancestors of the z ˜ 6 quasar SMBHs - globally warm the intergalactic medium and suppress the formation and growth of subsequent generations of BHs. We present two specific models with global miniquasar feedback that provide excellent agreement with recent estimates of the z = 6 SMBH mass function. For each of these models, we estimate the rate of BH mergers at z > 6 that could be detected by the proposed gravitational-wave observatory eLISA/NGO.

Forming supermassive black holes by accreting dark and baryon matter

NASA Astrophysics Data System (ADS)

Hu, Jian; Shen, Yue; Lou, Yu-Qing; Zhang, Shuangnan

2006-01-01

Given a large-scale mixture of self-interacting dark matter (SIDM) particles and baryon matter distributed in the early Universe, we advance here a two-phase accretion scenario for forming supermassive black holes (SMBHs) with masses around ~109Msolar at high redshifts z(>~6). The first phase is conceived to involve a rapid quasi-spherical and quasi-steady Bondi accretion of mainly SIDM particles embedded with baryon matter on to seed black holes (BHs) created at redshifts z<~ 30 by the first generation of massive Population III stars; this earlier phase rapidly gives birth to significantly enlarged seed BH masses of during z~ 20-15, where σ0 is the cross-section per unit mass of SIDM particles and Cs is the velocity dispersion in the SIDM halo referred to as an effective `sound speed'. The second phase of BH mass growth is envisaged to proceed primarily via baryon accretion, eventually leading to SMBH masses of MBH~ 109Msolar such SMBHs may form either by z~ 6 for a sustained accretion at the Eddington limit or later at lower z for sub-Eddington mean accretion rates. In between these two phases, there is a transitional yet sustained diffusively limited accretion of SIDM particles which in an eventual steady state would be much lower than the accretion rates of the two main phases. We intend to account for the reported detections of a few SMBHs at early epochs, e.g. Sloan Digital Sky Survey (SDSS) 1148+5251 and so forth, without necessarily resorting to either super-Eddington baryon accretion or very frequent BH merging processes. Only extremely massive dark SIDM haloes associated with rare peaks of density fluctuations in the early Universe may harbour such early SMBHs or quasars. Observational consequences are discussed. During the final stage of accumulating a SMBH mass, violent feedback in circumnuclear environs of a galactic nucleus leads to the central bulge formation and gives rise to the familiar empirical MBH-σb correlation inferred for nearby normal galaxies with σb being the stellar velocity dispersion in the galactic bulge; in our scenario, the central SMBH formation precedes that of the galactic bulge.

Galaxy Formation from the Primordial Black Holes

NASA Astrophysics Data System (ADS)

Morikawa, Masahiro

2017-12-01

Supermassive black hole (SMBH) of size MBH = 106-10M⊙ is common in the Universe and it defines the center of the galaxy. A galaxy and the SMBH are generally thought to have co-evolved. However, the SMBH cannot evolve so fast as commonly observed even at redshift z > 6. Therefore, we explore a natural hypothesis that the SMBH has been already formed mature at z ⪆ 10 before stars and galaxies. The SMBH forms energetic jets and out-flows which trigger massive star formation in the ambient gas. They eventually construct globular clusters and classical bulge as well as the body of elliptical galaxies. We propose simple models which implement these processes. We point out that the globular clusters and classical bulges have a common origin but are in different phases. The same is true for the elliptical and spiral galaxies. Physics behind these phase division is the runaway star formation process with strong feedback to SMBH. This is similar to the forest-fire model that displays self-organized criticality.

Multi-phase outflows as probes of AGN accretion history

NASA Astrophysics Data System (ADS)

Nardini, Emanuele; Zubovas, Kastytis

2018-05-01

Powerful outflows with a broad range of properties (such as velocity, ionization, radial scale and mass loss rate) represent a key feature of active galactic nuclei (AGN), even more so since they have been simultaneously revealed also in individual objects. Here we revisit in a simple analytical framework the recent remarkable cases of two ultraluminous infrared quasars, IRAS F11119+3257 and Mrk 231, which allow us to investigate the physical connection between multi-phase AGN outflows across the ladder of distance from the central supermassive black hole (SMBH). We argue that any major deviations from the standard outflow propagation models might encode unique information on the past SMBH accretion history, and briefly discuss how this could help address some controversial aspects of the current picture of AGN feedback.

Dynamical Processes Near the Super Massive Black Hole at the Galactic Center

NASA Astrophysics Data System (ADS)

Antonini, Fabio

2011-01-01

Observations of the stellar environment near the Galactic center provide the strongest empirical evidence for the existence of massive black holes in the Universe. Theoretical models of the Milky Way nuclear star cluster fail to explain numerous properties of such environment, including the presence of very young stars close to the super massive black hole (SMBH) and the more recent discovery of a parsec-scale core in the central distribution of the bright late-type (old) stars. In this thesis we present a theoretical study of dynamical processes near the Galactic center, strongly related to these issues. Using different numerical techniques we explore the close environment of a SMBH as catalyst for stellar collisions and mergers. We study binary stars that remain bound for several revolutions around the SMBH, finding that in the case of highly inclined binaries the Kozai resonance can lead to large periodic oscillations in the internal binary eccentricity and inclination. Collisions and mergers of the binary elements are found to increase significantly for multiple orbits around the SMBH. In collisions involving a low-mass and a high-mass star, the merger product acquires a high core hydrogen abundance from the smaller star, effectively resetting the nuclear evolution clock to a younger age. This process could serve as an important source of young stars at the Galactic center. We then show that a core in the old stars can be naturally explained in a scenario in which the Milky Way nuclear star cluster (NSC) is formed via repeated inspiral of globular clusters into the Galactic center. We present results from a set of N -body simulations of this process, which show that the fundamental properties of the NSC, including its mass, outer density profile and velocity structure, are also reproduced. Chandrasekhar's dynamical friction formula predicts no frictional force on a test body in a low-density core, regardless of its density, due to the absence of stars moving more slowly than the local circular velocity. We have tested this prediction using large-scale N -body experiments. The rate of orbital decay never drops precisely to zero, because stars moving faster than the test body also contribute to the frictional force. When the contribution from the fast-moving stars is included in the expression for the dynamical friction force, and the changes induced by the massive body on the stellar distribution are taken into account, Chandrasekhar's theory is found to reproduce the rate of orbital decay remarkably well. However, this rate is still substantially smaller than the rate predicted by Chandrasekhar's formula in its most widely-used forms, implying longer time scales for inspiral. Motivated by recent observations that suggest a parsec-scale core around the Galactic center SMBH, we investigated the evolution of a population of stellar-mass black holes (BHs) as they spiral in to the center of the Galaxy. After ˜ 10 Gyr, we find that the density of BHs can remain substantially less than the density in stars at all radii; we conclude that it would be unjustified to assume that the spatial distribution of BHs at the Galactic center is well described by steady-state models.

MIGRATION TRAPS IN DISKS AROUND SUPERMASSIVE BLACK HOLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellovary, Jillian M.; Low, Mordecai-Mark Mac; McKernan, Barry

Accretion disks around supermassive black holes (SMBHs) in active galactic nuclei (AGNs) contain stars, stellar mass black holes, and other stellar remnants, which perturb the disk gas gravitationally. The resulting density perturbations exert torques on the embedded masses causing them to migrate through the disk in a manner analogous to planets in protoplanetary disks. We determine the strength and direction of these torques using an empirical analytic description dependent on local disk gradients, applied to two different analytic, steady-state disk models of SMBH accretion disks. We find that there are radii in such disks where the gas torque changes sign,more » trapping migrating objects. Our analysis shows that major migration traps generally occur where the disk surface density gradient changes sign from positive to negative, around 20–300R{sub g}, where R{sub g} = 2GM/c{sup 2} is the Schwarzschild radius. At these traps, massive objects in the AGN disk can accumulate, collide, scatter, and accrete. Intermediate mass black hole formation is likely in these disk locations, which may lead to preferential gap and cavity creation at these radii. Our model thus has significant implications for SMBH growth as well as gravitational wave source populations.« less

Eddington-limited Accretion in z ∼ 2 WISE-selected Hot, Dust-obscured Galaxies

NASA Astrophysics Data System (ADS)

Wu, Jingwen; Jun, Hyunsung D.; Assef, Roberto J.; Tsai, Chao-Wei; Wright, Edward L.; Eisenhardt, Peter R. M.; Blain, Andrew; Stern, Daniel; Díaz-Santos, Tanio; Denney, Kelly D.; Hayden, Brian T.; Perlmutter, Saul; Aldering, Greg; Boone, Kyle; Fagrelius, Parker

2018-01-01

Hot, dust-obscured galaxies, or “Hot DOGs,” are a rare, dusty, hyperluminous galaxy population discovered by the WISE mission. Predominantly at redshifts 2–3, they include the most luminous known galaxies in the universe. Their high luminosities likely come from accretion onto highly obscured supermassive black holes (SMBHs). We have conducted a pilot survey to measure the SMBH masses of five z∼ 2 Hot DOGs via broad Hα emission lines, using Keck/MOSFIRE and Gemini/FLAMINGOS-2. We detect broad Hα emission in all five Hot DOGs. We find substantial corresponding SMBH masses for these Hot DOGs (∼ {10}9 {M}ȯ ), and their derived Eddington ratios are close to unity. These z∼ 2 Hot DOGs are the most luminous active galactic nuclei for their BH masses, suggesting that they are accreting at the maximum rates for their BHs. A similar property is found for known z∼ 6 quasars. Our results are consistent with scenarios in which Hot DOGs represent a transitional, high-accretion phase between obscured and unobscured quasars. Hot DOGs may mark a special evolutionary stage before the red quasar and optical quasar phases, and they may be present at other cosmic epochs.

Millimetre-wave emission from an intermediate-mass black hole candidate in the Milky Way

NASA Astrophysics Data System (ADS)

Oka, Tomoharu; Tsujimoto, Shiho; Iwata, Yuhei; Nomura, Mariko; Takekawa, Shunya

2017-10-01

It is widely accepted that black holes with masses greater than a million solar masses (M⊙) lurk at the centres of massive galaxies. The origins of such `supermassive' black holes (SMBHs) remain unknown1, although those of stellar-mass black holes are well understood. One possible scenario is that intermediate-mass black holes (IMBHs), which are formed by the runaway coalescence of stars in young compact star clusters2, merge at the centre of a galaxy to form a SMBH3. Although many candidates for IMBHs have been proposed, none is accepted as definitive. Recently, we discovered a peculiar molecular cloud, CO-0.40-0.22, with an extremely broad velocity width, near the centre of our Milky Way galaxy. Based on the careful analysis of gas kinematics, we concluded that a compact object with a mass of about 105M⊙ is lurking in this cloud4. Here we report the detection of a point-like continuum source as well as a compact gas clump near the centre of CO-0.40-0.22. This point-like continuum source (CO-0.40-0.22*) has a wide-band spectrum consistent with 1/500 of the Galactic SMBH (Sgr A*) in luminosity. Numerical simulations around a point-like massive object reproduce the kinematics of dense molecular gas well, which suggests that CO-0.40-0.22* is one of the most promising candidates for an intermediate-mass black hole.

Event Rates of Gravitational Waves from merging Intermediate mass Black Holes: based on a Runaway Path to a SMBH

NASA Astrophysics Data System (ADS)

Shinkai, Hisaaki

2018-01-01

Based on a dynamical formation model of a supermassive black hole (SMBH), we estimate the expected observational profile of gravitational wave at ground-based detectors, such as KAGRA or advanced LIGO/VIRGO. Noting that the second generation of detectors have enough sensitivity from 10 Hz and up, we are able to detect the ring-down gravitational wave of a BH with the mass M < 2 × 103M⊙. This enables us to check the sequence of BH mergers to SMBHs via intermediate-mass BHs. We estimate the number density of galaxies from the halo formation model and estimate the number of BH mergers from the giant molecular cloud model assuming hierarchical growth of merged cores. At the designed KAGRA (and/or advanced LIGO/VIRGO), we find that the BH merger of its total mass M ˜ 60M⊙ is at the peak of the expected mass distribution. With its signal-to-noise ratio ρ = 10(30), we estimate the event rate R ˜ 200(20) per year in the most optimistic case, and we also find that BH mergers in the range M < 150M⊙ are R > 1 per year for ρ = 10. Thus, if we observe a BH with more than 100M⊙ in future gravitational-wave observations, our model naturally explains its source.

360-degree video and X-ray modeling of the Galactic center's inner parsec

NASA Astrophysics Data System (ADS)

Russell, Christopher Michael Post; Wang, Daniel; Cuadra, Jorge

2017-08-01

360-degree videos, which render an image over all 4pi steradian, provide a unique and immersive way to visualize astrophysical simulations. Video sharing sites such as YouTube allow these videos to be shared with the masses; they can be viewed in their 360° nature on computer screens, with smartphones, or, best of all, in virtual-reality (VR) goggles. We present the first such 360° video of an astrophysical simulation: a hydrodynamics calculation of the Wolf-Rayet stars and their ejected winds in the inner parsec of the Galactic center. Viewed from the perspective of the super-massive black hole (SMBH), the most striking aspect of the video, which renders column density, is the inspiraling and stretching of clumps of WR-wind material as they makes their way towards the SMBH. We will brielfy describe how to make 360° videos and how to publish them online in their desired 360° format. Additionally we discuss computing the thermal X-ray emission from a suite of Galactic-center hydrodynamic simulations that have various SMBH feedback mechanisms, which are compared to Chandra X-ray Visionary Program observations of the region. Over a 2-5” ring centered on Sgr A*, the spectral shape is well matched, indicating that the WR winds are the dominant source of the thermal X-ray emission. Furthermore, the X-ray flux depends on the SMBH feedback due to the feedback's ability to clear out material from the central parsec. A moderate outburst is necessary to explain the current thermal X-ray flux, even though the outburst ended ˜100 yr ago.

Bow shocks as tracers of the environment and stellar outflows near the supermassive black hole.

NASA Astrophysics Data System (ADS)

Stofanova, L.; Zajaček, M.; Karas, V.

2017-10-01

Bow shocks develop near stars in the supersonic motion with respect to the surrounding interstellar environment. In particular, extended shocks emerge due to the interaction of stars with strong winds. We discuss the expected shape and orientation of bow shocks in the context of fast moving stars near a supermassive black hole (SMBH) embedded within Bondi-type accretion flow (Zajaček et al. 2016, MNRAS; Štofanová 2016, BSc. Thesis). We present models which take into account different velocities of the probe star and also consider various scenarios for the ambient medium near the vicinity of the black hole such as an inflow/outflow of the material towards/outwards SMBH or a model which considers inflow and outflow at the same time. Under suitable circumstances, a bow shock structure can be detected in infrared domain and their properties can trace the environment of the Galactic center. On the other hand, if density of the ambient medium is determined from mm/radio observations, bow shocks can be used to constrain mass-loss rates of massive OB/WR stars. X-rays can supplement the spectral evidence, though, the structures are below the angular resolution of the current instruments even in the most favourable case of the Milky Way's SMBH (Sgr A*).

A UNIFIED FRAMEWORK FOR THE ORBITAL STRUCTURE OF BARS AND TRIAXIAL ELLIPSOIDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valluri, Monica; Abbott, Caleb; Shen, Juntai

We examine a large random sample of orbits in two self-consistent simulations of N-body bars. Orbits in these bars are classified both visually and with a new automated orbit classification method based on frequency analysis. The well-known prograde x1 orbit family originates from the same parent orbit as the box orbits in stationary and rotating triaxial ellipsoids. However, only a small fraction of bar orbits (∼4%) have predominately prograde motion like their periodic parent orbit. Most bar orbits arising from the x1 orbit have little net angular momentum in the bar frame, making them equivalent to box orbits in rotatingmore » triaxial potentials. In these simulations a small fraction of bar orbits (∼7%) are long-axis tubes that behave exactly like those in triaxial ellipsoids: they are tipped about the intermediate axis owing to the Coriolis force, with the sense of tipping determined by the sign of their angular momentum about the long axis. No orbits parented by prograde periodic x2 orbits are found in the pure bar model, but a tiny population (∼2%) of short-axis tube orbits parented by retrograde x4 orbits are found. When a central point mass representing a supermassive black hole (SMBH) is grown adiabatically at the center of the bar, those orbits that lie in the immediate vicinity of the SMBH are transformed into precessing Keplerian orbits that belong to the same major families (short-axis tubes, long-axis tubes and boxes) occupying the bar at larger radii. During the growth of an SMBH, the inflow of mass and outward transport of angular momentum transform some x1 and long-axis tube orbits into prograde short-axis tubes. This study has important implications for future attempts to constrain the masses of SMBHs in barred galaxies using orbit-based methods like the Schwarzschild orbit superposition scheme and for understanding the observed features in barred galaxies.« less

Black Hole Growth Is Mainly Linked to Host-galaxy Stellar Mass Rather Than Star Formation Rate

NASA Astrophysics Data System (ADS)

Yang, G.; Chen, C.-T. J.; Vito, F.; Brandt, W. N.; Alexander, D. M.; Luo, B.; Sun, M. Y.; Xue, Y. Q.; Bauer, F. E.; Koekemoer, A. M.; Lehmer, B. D.; Liu, T.; Schneider, D. P.; Shemmer, O.; Trump, J. R.; Vignali, C.; Wang, J.-X.

2017-06-01

We investigate the dependence of black hole accretion rate (BHAR) on host-galaxy star formation rate (SFR) and stellar mass (M *) in the CANDELS/GOODS-South field in the redshift range of 0.5≤slant z< 2.0. Our sample consists of ≈ {{18,000}} galaxies, allowing us to probe galaxies with 0.1{M}⊙ {{yr}}-1≲ {SFR}≲ 100 {M}⊙ {{yr}}-1 and/or {10}8{M}⊙ ≲ {M}* ≲ {10}11 {M}⊙ . We use sample-mean BHAR to approximate long-term average BHAR. Our sample-mean BHARs are derived from the Chandra Deep Field-South 7 Ms observations, while the SFRs and M * have been estimated by the CANDELS team through spectral energy distribution fitting. The average BHAR is correlated positively with both SFR and M *, and the BHAR-SFR and BHAR-M * relations can both be described acceptably by linear models with a slope of unity. However, BHAR appears to be correlated more strongly with M * than SFR. This result indicates that M * is the primary host-galaxy property related to supermassive black hole (SMBH) growth, and the apparent BHAR-SFR relation is largely a secondary effect due to the star-forming main sequence. Among our sources, massive galaxies ({M}* ≳ {10}10{M}⊙ ) have significantly higher BHAR/SFR ratios than less massive galaxies, indicating that the former have higher SMBH fueling efficiency and/or higher SMBH occupation fraction than the latter. Our results can naturally explain the observed proportionality between {M}{BH} and M * for local giant ellipticals and suggest that their {M}{BH}/{M}* is higher than that of local star-forming galaxies. Among local star-forming galaxies, massive systems might have higher {M}{BH}/{M}* compared to dwarfs.

Investigating the Binarity of S0-2: Implications for Its Origins and Robustness as a Probe of the Laws of Gravity around a Supermassive Black Hole

NASA Astrophysics Data System (ADS)

Chu, Devin S.; Do, Tuan; Hees, Aurelien; Ghez, Andrea; Naoz, Smadar; Witzel, Gunther; Sakai, Shoko; Chappell, Samantha; Gautam, Abhimat K.; Lu, Jessica R.; Matthews, Keith

2018-02-01

The star S0-2, which orbits the supermassive black hole (SMBH) in our Galaxy with a period of 16 years, provides the strongest constraint on both the mass of the SMBH and the distance to the Galactic center. S0-2 will soon provide the first measurement of relativistic effects near a SMBH. We report the first limits on the binarity of S0-2 from radial velocity (RV) monitoring, which has implications for both understanding its origin and robustness as a probe of the central gravitational field. With 87 RV measurements, which include 12 new observations that we present, we have the requisite data set to look for RV variations from S0-2‧s orbital model. Using a Lomb–Scargle analysis and orbit-fitting for potential binaries, we detect no RV variation beyond S0-2‧s orbital motion and do not find any significant periodic signal. The lack of a binary companion does not currently distinguish different formation scenarios for S0-2. The upper limit on the mass of a companion star ({M}{comp}) still allowed by our results has a median upper limit of {M}{comp} sin i ≤ 1.6 M ⊙ for periods between 1 and 150 days, the longest period to avoid tidal break-up of the binary. We also investigate the impact of the remaining allowed binary system on the measurement of the relativistic redshift at S0-2‧s closest approach in 2018. While binary star systems are important to consider for this experiment, we find that plausible binaries for S0-2 will not alter a 5σ detection of the relativistic redshift.

The Infrared Medium-deep Survey. IV. The Low Eddington Ratio of A Faint Quasar at z ∼ 6: Not Every Supermassive Black Hole is Growing Fast in the Early Universe

NASA Astrophysics Data System (ADS)

Kim, Yongjung; Im, Myungshin; Jeon, Yiseul; Kim, Minjin; Hyun, Minhee; Kim, Dohyeong; Kim, Jae-Woo; Taak, Yoon Chan; Yoon, Yongmin; Choi, Changsu; Hong, Jueun; Jun, Hyunsung David; Karouzos, Marios; Kim, Duho; Kim, Ji Hoon; Lee, Seong-Kook; Pak, Soojong; Park, Won-Kee

2018-03-01

To date, most of the luminous quasars known at z ∼ 6 have been found to be in maximal accretion with the Eddington ratios, {λ }Edd}∼ 1, suggesting enhanced nuclear activities in the early universe. However, this may not be the whole picture of supermassive black hole (SMBH) growth, since previous studies have not reached faint quasars that are more likely to harbor SMBHs with low {λ }Edd}. To gain a better understanding of the accretion activities in quasars in the early universe, we obtained a deep near-infrared (NIR) spectrum of a quasar, IMS J220417.92+011144.8 (hereafter IMS J2204+0112), one of the faintest quasars that has been identified at z ∼ 6. From the redshifted C IV λ1549 emission line in the NIR spectrum, we find that IMS J2204+0112 harbors a SMBH with a solar mass of about a billion and {λ }Edd}∼ 0.1, but with a large uncertainty in both quantities (0.41 dex). IMS J2204+0112 has one of the lowest Eddington ratios among quasars at z ∼ 6, but a common value among quasars at z ∼ 2. Its low {λ }Edd} can be explained with two scenarios; the SMBH growth from a stellar-mass black hole through short-duration super-Eddington accretion events or from a massive black hole seed (∼ {10}5 {M}ȯ ) with Eddington-limited accretion. NIR spectra of more faint quasars are needed to better understand the accretion activities of SMBHs at z ∼ 6.

Connecting traces of galaxy evolution: the missing core mass-morphological fine structure relation

NASA Astrophysics Data System (ADS)

Bonfini, P.; Bitsakis, T.; Zezas, A.; Duc, P.-A.; Iodice, E.; González-Martín, O.; Bruzual, G.; González Sanoja, A. J.

2018-01-01

Deep exposure imaging of early-type galaxies (ETGs) are revealing the second-order complexity of these objects, which have been long considered uniform, dispersion-supported spheroidals. `Fine structure' features (e.g. ripples, plumes, tidal tails, rings) as well as depleted stellar cores (i.e. central light deficits) characterize a number of massive ETG galaxies, and can be interpreted as the result of galaxy-galaxy interactions. We discuss how the time-scale for the evolution of cores and fine structures are comparable, and hence it is expected that they develop in parallel after the major interaction event which shaped the ETG. Using archival data, we compare the `depleted stellar mass' (i.e. the mass missing from the depleted stellar core) against the prominence of the fine structure features, and observe that they correlate inversely. This result confirms our expectation that, while the supermassive black hole (SMBH) binary (constituted by the SMBHs of the merger progenitors) excavates the core via three-body interactions, the gravitational potential of the newborn galaxy relaxes, and the fine structures fade below detection levels. We expect the inverse correlation to hold at least within the first Gyr from the merger which created the SMBH binary; after then, the fine structure evolves independently.

AGN jet-driven stochastic cold accretion in cluster cores

NASA Astrophysics Data System (ADS)

Prasad, Deovrat; Sharma, Prateek; Babul, Arif

2017-10-01

Several arguments suggest that stochastic condensation of cold gas and its accretion on to the central supermassive black hole (SMBH) is essential for active galactic nuclei (AGNs) feedback to work in the most massive galaxies that lie at the centres of galaxy clusters. Our 3-D hydrodynamic AGN jet-ICM (intracluster medium) simulations, looking at the detailed angular momentum distribution of cold gas and its time variability for the first time, show that the angular momentum of the cold gas crossing ≲1 kpc is essentially isotropic. With almost equal mass in clockwise and counterclockwise orientations, we expect a cancellation of the angular momentum on roughly the dynamical time. This means that a compact accretion flow with a short viscous time ought to form, through which enough accretion power can be channeled into jet mechanical energy sufficiently quickly to prevent a cooling flow. The inherent stochasticity, expected in feedback cycles driven by cold gas condensation, gives rise to a large variation in the cold gas mass at the centres of galaxy clusters, for similar cluster and SMBH masses, in agreement with the observations. Such correlations are expected to be much tighter for the smoother hot/Bondi accretion. The weak correlation between cavity power and Bondi power obtained from our simulations also matches observations.

Subaru adaptive-optics high-spatial-resolution infrared K- and L'-band imaging search for deeply buried dual AGNs in merging galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Imanishi, Masatoshi; Saito, Yuriko, E-mail: masa.imanishi@nao.ac.jp

2014-01-01

We present the results of infrared K- (2.2 μm) and L'-band (3.8 μm) high-spatial-resolution (<0.''2) imaging observations of nearby gas- and dust-rich infrared luminous merging galaxies, assisted by the adaptive optics system on the Subaru 8.2 m telescope. We investigate the presence and frequency of red K – L' compact sources, which are sensitive indicators of active galactic nuclei (AGNs), including AGNs that are deeply buried in gas and dust. We observed 29 merging systems and confirmed at least one AGN in all but one system. However, luminous dual AGNs were detected in only four of the 29 systems (∼14%),more » despite our method's being sensitive to buried AGNs. For multiple nuclei sources, we compared the estimated AGN luminosities with supermassive black hole (SMBH) masses inferred from large-aperture K-band stellar emission photometry in individual nuclei. We found that mass accretion rates onto SMBHs are significantly different among multiple SMBHs, such that larger-mass SMBHs generally show higher mass accretion rates when normalized to SMBH mass. Our results suggest that non-synchronous mass accretion onto SMBHs in gas- and dust-rich infrared luminous merging galaxies hampers the observational detection of kiloparsec-scale multiple active SMBHs. This could explain the significantly smaller detection fraction of kiloparsec-scale dual AGNs when compared with the number expected from simple theoretical predictions. Our results also indicate that mass accretion onto SMBHs is dominated by local conditions, rather than by global galaxy properties, reinforcing the importance of observations to our understanding of how multiple SMBHs are activated and acquire mass in gas- and dust-rich merging galaxies.« less

A model for periodic blazars

NASA Astrophysics Data System (ADS)

Sobacchi, Emanuele; Sormani, Mattia C.; Stamerra, Antonio

2017-02-01

We describe a scenario to explain blazar periodicities with time-scales of ˜ few years. The scenario is based on a binary supermassive black hole (SMBH) system in which one of the two SMBHs carries a jet. We discuss the various mechanisms that can cause the jet to precess and produce corkscrew patterns through space with a scale of ˜ few pc. It turns out that the dominant mechanism responsible for the precession is simply the imprint of the jet-carrying SMBH orbital speed on the jet. Gravitational deflection and Lense-Thirring precession (due to the gravitational field of the other SMBH) are second-order effects. We complement the scenario with a kinematical jet model which is inspired to the spine-sheath structure observed in M87. One of the main advantages of such a structure is that it allows the peak of the synchrotron emission to scale with frequency according to νF ∝ νξ as the viewing angle is changed, where ξ is not necessarily 3 or 4 as in the case of jets with uniform velocity, but can be ξ ˜ 1. Finally, we apply the model to the source PG1553+113, which has been recently claimed to show a Tobs = (2.18 ± 0.08) yr periodicity. We are able to reproduce the optical and gamma-ray light curves and multiple synchrotron spectra simultaneously. We also give estimates of the source mass and size.

The Hunt for Low-Mass Black Holes in the JWST Era

NASA Astrophysics Data System (ADS)

Cann, Jenna; Satyapal, Shobita; Abel, Nicholas; Ricci, Claudio; Gliozzi, Mario; Blecha, Laura; Secrest, Nathan

2018-01-01

Most, if not all, massive galaxies have a central supermassive black hole (SMBH) millions to billions of times the mass of the Sun. While the properties of SMBHs and their host galaxies have been well-studied in massive galaxies, very few SMBHs have been found in galaxies with low masses and those with small bulges. This is a significant deficiency, because the study of this population allows us to gain an understanding of merger-free pathways to black hole growth, and to gain insight into the origin and growth of SMBH ‘seeds’, thought to have formed at high redshift. Most studies aimed at finding SMBHs have been conducted using optical spectroscopic studies, where active SMBHs (active galactic nuclei or AGNs) display distinctive optical emission lines indicative of accreting SMBHs. However, in low mass (dwarf) galaxies, the SMBHs will likely be less massive, and can be energetically weak and possibly deeply embedded in their host galaxies. As a result, the optical emission lines may be dominated by star formation regions, severely limiting the diagnostic power of optical surveys in finding and characterizing the properties of the AGN in dwarf galaxies. In such galaxies, infrared coronal lines provide a robust method of finding AGNs. Furthermore, as the black hole mass decreases, the Schwarzschild radius of the black hole decreases, and in response, the temperature of the surrounding accretion disk increases. The shape of the ionizing radiation spectral energy distribution therefore changes with black hole mass, which will affect the emission line spectrum from the surrounding gas. In this work, we investigate the diagnostic power of infrared coronal lines and the effect of black hole mass on the emission line spectra from AGNs, with a particular focus on the emission lines accessible by JWST.

Hidden Pair of Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-08-01

Could a pair of supermassive black holes (SMBHs) be lurking at the center of the galaxy Mrk 231? A recent study finds that this may be the case and the unique spectrum of this galaxy could be the key to discovering more hidden binary SMBH systems.Where Are the Binary Supermassive Black Holes?Its believed that most, if not all, galaxies have an SMBH at their centers. As two galaxies merge, the two SMBHs should evolve into a closely-bound binary system before they eventually merge. Given the abundance of galaxy mergers, we would expect to see the kinematic and visual signatures of these binary SMBHs among observed active galactic nuclei yet such evidence for sub-parsec binary SMBH systems remains scarce and ambiguous. This has led researchers to wonder: is there another way that we might detect these elusive systems?A collaboration led by Chang-Shuo Yan (National Astronomical Observatories, Chinese Academy of Sciences) thinks that there is. The group suggests that these systems might have distinct signatures in their optical-to-UV spectra, and they identify a system that might be just such a candidate: Mrk 231.A Binary CandidateProposed model of Mrk 231. Two supermassive black holes, each with their own mini-disk, orbit each other in the center of a circumbinary disk. The secondary black hole has cleared gap in the circumbinary disk as a result of its orbit around the primary black hole. [Yan et al. 2015]Mrk 231 is a galaxy with a disturbed morphology and tidal tails strong clues that it might be in the final stages of a galactic merger. In addition to these signs, Mrk 231 also has an unusual spectrum for a quasar: its continuum emission displays an unexpected drop in the near-UV band.Yan and her collaborators propose that the odd behavior of Mrk 231s spectrum can be explained if the center of the galaxy houses a pair of SMBHs each with its own mini accretion disk surrounded by a circumbinary accretion disk. As the secondary SMBH orbits the primary SMBH (with a period of 1.2 years and a mass ratio of 38:1, according to the teams models), it clears a gap in the circumbinary disk. The collaborators showed that this gap in the disk will cause a decrease in the continuum emission of the system consistent with the observed drop in Mrk 231s UV spectrum.If the collaborations models of Mrk 231 are confirmed, this would demonstrate the feasibility of finding other active binary SMBH systems by looking for similar deficits in the optical-to-UV spectra.CitationChang-Shuo Yan et al.2015 ApJ 809 117. doi:10.1088/0004-637X/809/2/117

The Post-starburst Evolution of Tidal Disruption Event Host Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

French, K. Decker; Zabludoff, Ann; Arcavi, Iair

We constrain the recent star formation histories of the host galaxies of eight optical/UV-detected tidal disruption events (TDEs). Six hosts had quick starbursts of <200 Myr duration that ended 10–1000 Myr ago, indicating that TDEs arise at different times in their hosts’ post-starburst evolution. If the disrupted star formed in the burst or before, the post-burst age constrains its mass, generally excluding O, most B, and highly massive A stars. If the starburst arose from a galaxy merger, the time since the starburst began limits the coalescence timescale and thus the merger mass ratio to more equal than 12:1 inmore » most hosts. This uncommon ratio, if also that of the central supermassive black hole (SMBH) binary, disfavors the scenario in which the TDE rate is boosted by the binary but is insensitive to its mass ratio. The stellar mass fraction created in the burst is 0.5%–10% for most hosts, not enough to explain the observed 30–200× boost in TDE rates, suggesting that the host’s core stellar concentration is more important. TDE hosts have stellar masses 10{sup 9.4}–10{sup 10.3} M {sub ☉}, consistent with the Sloan Digital Sky Survey volume-corrected, quiescent Balmer-strong comparison sample and implying SMBH masses of 10{sup 5.5}–10{sup 7.5} M {sub ☉}. Subtracting the host absorption line spectrum, we uncover emission lines; at least five hosts have ionization sources inconsistent with star formation that instead may be related to circumnuclear gas, merger shocks, or post-AGB stars.« less

Black Hole Foraging: Feedback Drives Feeding

NASA Astrophysics Data System (ADS)

Dehnen, Walter; King, Andrew

2013-11-01

We suggest a new picture of supermassive black hole (SMBH) growth in galaxy centers. Momentum-driven feedback from an accreting hole gives significant orbital energy, but little angular momentum to the surrounding gas. Once central accretion drops, the feedback weakens and swept-up gas falls back toward the SMBH on near-parabolic orbits. These intersect near the black hole with partially opposed specific angular momenta, causing further infall and ultimately the formation of a small-scale accretion disk. The feeding rates into the disk typically exceed Eddington by factors of a few, growing the hole on the Salpeter timescale and stimulating further feedback. Natural consequences of this picture include (1) the formation and maintenance of a roughly toroidal distribution of obscuring matter near the hole; (2) random orientations of successive accretion disk episodes; (3) the possibility of rapid SMBH growth; (4) tidal disruption of stars and close binaries formed from infalling gas, resulting in visible flares and ejection of hypervelocity stars; (5) super-solar abundances of the matter accreting on to the SMBH; and (6) a lower central dark-matter density, and hence annihilation signal, than adiabatic SMBH growth implies. We also suggest a simple subgrid recipe for implementing this process in numerical simulations.

Non-stationary emission of the blazar S4 0954+658 over a wide range of wavelength

NASA Astrophysics Data System (ADS)

Volvach, A. E.; Bychkova, V. S.; Larionov, M. G.; Kardashev, N. S.; Volvach, L. N.; Vlasyuk, V. V.; Spiridonova, O. I.; Lähteenmäki, A.; Tornikoski, M.; Aller, M. F.; Aller, H. D.; Pooley, G.; Carrasco, L.; Porras, A.; Recillas, E.

2016-12-01

Data from long-term multi-frequency monitoring are used to analyze variations in the flux density of the active galactic nucleus S4 0954+658. These data were obtained at the CrimeanAstrophysical Observatory, the Metsähovi Radio Observatory of Aalto University, the University of Michigan Radio Astronomy Observatory, the Cavendish Laboratory of Cambridge University, the Special Astrophysical Observatory, and the National Institute of Astrophysics, Optics, and Electronics; 0.1-300-GeV data from the Fermi space gamma-ray observatory were also used. Radio data at 4.8, 8, 14.5, 15, 22.2, and 36.8 GHz are considered together with optical and near-infrared data in the R, J, H, and K filters. In the framework of a model in which binary supermassive black holes (SMBHs) are present in active galactic nuclei, harmonic and structural analyses are carried out to establish the orbital ( T orb ≈ 780 yrs) and precessional ( T pr ≈ 7800 yrs) periods in the rest frame of the source. The development of the most powerful flare ever observed in this object, which occurred in February 2015, is considered. The delay in the flare's development in different wavelength ranges from the gamma-ray to the radio is determined. both the magnitude of the delays and the durations of the flares themselves suggest that the physical characteristics of S4 0954+658 are similar to those of the blazar S5 0716+714, which displays evidence of a high γ factor for the jet motion and high superluminal speeds in the jet. The masses of the components of the binary SMBH ( M and m), the dimensions of their orbit, and the velocity of the lower-mass SMBH about the central SMBH are estimated. The derived physical characteristics are subject to a comparative analysis.

Update on the X-Ray Variability Plane for Active Galactic Nuclei: The Role of the Obscuration

NASA Astrophysics Data System (ADS)

González-Martín, Omaira

2018-05-01

Scaling relations are the most powerful astrophysical tools to set constraints on the physical mechanisms of astronomical sources and to infer properties that cannot be accessed directly. We reinvestigate here one of these scaling relations in active galactic nuclei (AGNs); the so-called X-ray variability plane (or mass–luminosity timescale relation). This relation links the power-spectral density (PSD) break frequency with the super-massive black hole (SMBH) mass and the bolometric luminosity. We used the available XMM-Newton observations of a sample of 22 AGNs to study the PSD and spectra in short segments within each observation. This allows us to report for the first time that the PSD break frequency varies for each object, showing variations in 19 out of the 22 AGNs analyzed. Our analysis of the variability plane confirms the relation between the break frequency and the SMBH mass and finds that the obscuration along the line of sight N H (or the variations on the obscuration using its standard deviation, ΔN H) is also a required parameter, at least for the range of frequencies analyzed here (∼ 3 × {10}-5-5× {10}-2 {Hz}). We constrain a new variability plane of the following form: {log}({ν }Break})=(-0.589 +/- 0.005) {log}({{{M}}}BH})+(0.10+/- 0.01) {log}({{{N}}}{{H}})-(1.5+/- 0.3) (or {log}({ν }Break})=(-0.549+/- 0.009) {log}({{{M}}}BH}) +(0.56+/- 0.06) {{Δ }}{N}{{H}}+(0.19+/- 0.08)). The X-ray variability plane found by McHardy et al. is roughly recovered when we use unobscured segments. We speculate that this behavior is well explained if most of the reported frequencies are related to inner clouds (within 1 pc), following Kepler orbits under the gravitational field of the SMBH.

Growth problems of stellar black holes in early galaxies

NASA Astrophysics Data System (ADS)

Orofino, M. C.; Ferrara, A.; Gallerani, S.

2018-06-01

The nature of the seeds of the observed high-z super-massive black holes (SMBH) is unknown. Although different options have been proposed, involving e.g. intermediate mass direct collapse black holes, BH remnants of massive stars remain the most natural explanation. To identify the most favorable conditions (if any) for their rapid growth, we study the accretion rate of a M• = 100M⊙ BH formed in a typical z = 10 galaxy under different conditions (e.g. galaxy structure, BH initial position and velocity). We model the galaxy baryonic content and follow the BH orbit and accretion history for 300 Myr (the time span in 10 > z > 7), assuming the radiation-regulated accretion model by Park & Ricotti (2013). We find that, within the limits of our model, BH seeds cannot grow by more than 30%, suggesting that accretion on light-seed models are inadequate to explain high-z SMBH. We also compute the X-ray emission from such accreting stellar BH population in the [0.5 - 8] keV band and find it comparable to the one produced by high-mass X-ray binaries. This study suggests that early BHs, by X-ray pre-heating of the intergalactic medium at cosmic dawn, might leave a specific signature on the HI 21 cm line power spectrum potentially detectable with SKA.

Outflow and Accretion Physics in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

McGraw, Sean Michael

2016-09-01

This dissertation focuses on placing observational constraints on outflows and accretion disks in active galactic nuclei (AGN) for the purpose of better understanding the physics of super-massive black holes (SMBHs) and their evolution with the host galaxy over cosmic time. Quasar outflows and their importance in SMBH-host galaxy co-evolution can be further understood by analyzing broad absorption lines (BALs) in rest-frame UV spectra that trace a range of wind conditions. We quantify the properties of the flows by conducting BAL variability studies using multiple-epoch spectra acquired primarily from MDM Observatory and from the Sloan Digital Sky Survey. Iron low-ionization BALs (FeLoBALs) are a rare type of outflow that may represent a transient phase in galaxy evolution, and we analyze the variations in 12 FeLoBAL quasars with redshifts between 0.7 ≤ z ≤ 1.9 and rest frame timescales between ˜10 d to 7.6 yr. We investigate BAL variability in 71 quasar outflows that exhibit P V absorption, a tracer of high column density gas (i.e. NH ≥ 1022 cm -2), in order to quantify the energies and momenta of the flows. We also characterize the variability patterns of 26 quasars with mini-BALs, an interesting class of absorbers that may represent a distinct phase in the evolution of outflows. Low-luminosity AGN (LLAGN) are important objects to study since their prominence in the local Universe suggest a possible evolution from the quasar era, and their low radiative outputs likely indicate a distinct mode of accretion onto the SMBH. We probe the accretion conditions in the LLAGN NGC 4203 by estimating the SMBH mass, which is obtained by modeling the 2-dimensional velocity field of the nebular gas using spectra from the Hubble Space Telescope. We detect significant BAL and mini-BAL variability in a subset of quasars from each of our samples, with measured rest-frame variability time-scales from days to years and over multiple years on average. Variable wavelength intervals are associated with high-ionization species such as C IV and N V, low-ionization lines including Mg II and Al III, and ground and excited states from Fe II multiplets. The detected BAL and mini-BAL variations in a subset of sources provide evidence supporting scenarios involving either transverse motions of gas or ionization changes within the absorbers. We conclude that some outflows in our samples likely exist on the order of 0.01-1 pc from the SMBH, and the possibility remains that we are tracing outflowing gas on larger scales within limits ranging from ≤10 pc to ≤1 kpc from the central source. We estimate outflow kinetic luminosities between ˜10 6 and 1 times the bolometric luminosity of the quasar, indicating that the BAL outflows we probe likely possess a range of energies and only some absorber energies are likely sufficient for AGN feedback processes. We estimate the SMBH mass in the LLAGN in NGC 4203 to be ˜1.1x10 7 solar masses within a factor of ˜2. This mass estimate in conjunction with theoretical predictions is consistent with the existence of a two-component accretion flow in the nucleus of NGC 4203, consisting of a hot, advection-dominated torus at small radii connected with a thin, radiatively efficient disk at larger scales. These results provide a significant increase in the information available for quasar outflow properties and the conditions in low-luminosity accretion disks, and will inform future observational and theoretical studies that attempt to construct a more complete picture of AGN and their effects on the surrounding environments.

BAL QSOs AND EXTREME UFOs: THE EDDINGTON CONNECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zubovas, Kastytis; King, Andrew, E-mail: kastytis.zubovas@ftmc.lt

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to {approx}10-50 times this in BAL QSOs. For UFOs this implies black holemore » accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-{sigma} relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.« less

BAL QSOs and Extreme UFOs: The Eddington Connection

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis; King, Andrew

2013-05-01

We suggest a common physical origin connecting the fast, highly ionized winds (UFOs) seen in nearby active galactic nuclei (AGNs), and the slower and less ionized winds of broad absorption line (BAL) QSOs. The primary difference is the mass-loss rate in the wind, which is ultimately determined by the rate at which mass is fed toward the central supermassive black hole (SMBH) on large scales. This is below the Eddington accretion rate in most UFOs, and slightly super-Eddington in extreme UFOs such as PG1211+143, but ranges up to ~10-50 times this in BAL QSOs. For UFOs this implies black hole accretion rates and wind mass-loss rates which are at most comparable to Eddington, giving fast, highly ionized winds. In contrast, BAL QSO black holes have mildly super-Eddington accretion rates, and drive winds whose mass-loss rates are significantly super-Eddington, and so are slower and less ionized. This picture correctly predicts the velocities and ionization states of the observed winds, including the recently discovered one in SDSS J1106+1939. We suggest that luminous AGNs may evolve through a sequence from BAL QSO through LoBAL to UFO-producing Seyfert or quasar as their Eddington factors drop during the decay of a bright accretion event. LoBALs correspond to a short-lived stage in which the AGN radiation pressure largely evacuates the ionization cone, but before the large-scale accretion rate has dropped to the Eddington value. We show that sub-Eddington wind rates would produce an M-σ relation lying above that observed. We conclude that significant SMBH mass growth must occur in super-Eddington phases, either as BAL QSOs, extreme UFOs, or obscured from direct observation.

Masses, Dimensionless Kerr Parameters, and Emission Regions in GeV Gamma-Ray-loud Blazars

NASA Astrophysics Data System (ADS)

Xie, G.-Z.; Ma, L.; Liang, E.-W.; Zhou, S.-B.; Xie, Z.-H.

2003-11-01

We have compiled sample of 17 GeV γ-ray-loud blazars, for which rapid optical variability and γ-ray fluxes are well observed, from the literature. We derive estimates of the masses, the minimum Kerr parameters amin, and the size of the emission regions of the supermassive black holes (SMBHs) for the blazars in the sample from their minimum optical variability timescales and γ-ray fluxes. The results show that (1) the masses derived from the optical variability timescale (MH) are significantly correlated with the masses from the γ-ray luminosity (MKNH); (2) the values of amin of the SMBHs with masses MH>=108.3 Msolar (three out of 17 objects) range from ~0.5 to ~1.0, suggesting that these SMBHs are likely to be Kerr black holes. For the SMBHs with MH<108.3 Msolar, however, amin=0, suggesting that a nonrotating black hole model cannot be ruled out for these objects. In addition, the values of the size of the emission region, r*, for the two kinds of SMBHs are significantly different. For the SMBHs with amin>0, the sizes of the emission regions are almost within the horizon (2rG) and marginally bound orbit (4rG), while for those with amin=0 they are in the range (4.3-66.4)rG, extending beyond the marginally stable orbit (6rG). These results may imply that (1) the rotational state, the radiating regions, and the physical processes in the inner regions for the two kinds of SMBH are significantly different and (2) the emission mechanisms of GeV γ-ray blazars are related to the SMBHs in their centers but are not related to the two different kinds of SMBH.

Turbovelocity Stars: Kicks Resulting from the Tidal Disruption of Solitary Stars

NASA Astrophysics Data System (ADS)

Manukian, Haik; Guillochon, James; Ramirez-Ruiz, Enrico; O'Leary, Ryan M.

2013-07-01

The centers of most known galaxies host supermassive black holes (SMBHs). In orbit around these black holes are a centrally concentrated distribution of stars, both in single and in binary systems. Occasionally, these stars are perturbed onto orbits that bring them close to the SMBH. If the star is in a binary system, the three-body interaction with the SMBH can lead to large changes in orbital energy, depositing one of the two stars on a tightly-bound orbit, and its companion into a hyperbolic orbit that may escape the galaxy. In this Letter, we show that the disruption of solitary stars can also lead to large positive increases in orbital energy. The kick velocity depends on the amount of mass the star loses at pericenter, but not on the ratio of black hole to stellar mass, and are at most the star's own escape velocity. We find that these kicks are usually too small to result in the ejection of stars from the Milky Way, but can eject the stars from the black hole's sphere of influence, reducing their probability of being disrupted again. We estimate that {\\mathord {\\sim }} 10^5 stars, {\\mathord {\\sim }} 1% of all stars within 10 pc of the galactic center, are likely to have had mass removed by the central black hole through tidal interaction, and speculate that these "turbovelocity" stars will at first be redder, but eventually bluer, and always brighter than their unharassed peers.

Hard X-ray luminosity function of tidal disruption events: First results from the MAXI extragalactic survey

NASA Astrophysics Data System (ADS)

Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Hori, Takafumi; Kawai, Nobuyuki; Negoro, Hitoshi; Mihara, Tatehiro

2016-08-01

We derive the first hard X-ray luminosity function (XLF) of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs), which gives an occurrence rate of TDEs per unit volume as a function of peak luminosity and redshift, utilizing an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI). On the basis of the light curves characterized by a power-law decay with an index of -5/3, a systematic search using the MAXI data detected four TDEs in the first 37 months of observations, all of which have been found in the literature. To formulate the TDE XLF, we consider the mass function of SMBHs, that of disrupted stars, the specific TDE rate as a function of SMBH mass, and the fraction of TDEs with relativistic jets. We perform an unbinned maximum likelihood fit to the MAXI TDE list and check the consistency with the observed TDE rate in the ROSAT all-sky survey. The results suggest that the intrinsic fraction of the jet-accompanying events is 0.0007%-34%. We confirm that at z ≲ 1.5 the contamination of the hard X-ray luminosity functions of active galactic nuclei by TDEs is not significant and hence that their contribution to the growth of SMBHs is negligible at the redshifts.

Central stellar mass deficits of early-type galaxies

NASA Astrophysics Data System (ADS)

Tsige Dullo, Bililign; Graham, Alister

2016-01-01

The centers of giant galaxies display stellar mass deficits (Mdef) which are thought to be a signature left by inspiraling supermassive black holes (SMBHs) from pre-merged galaxies. We quantify these deficits using the core-Sérsic model for the largest ever sample of early-type galaxies and find Mdef ˜ 0.5 to 4 MBH (SMBH mass). We find that lenticular disc galaxies with bulge magnitudes MV ≤ -21.0 mag also have central stellar deficits, suggesting that their bulges may have formed from major merger events while their surroundingdisc was subsequently built up, perhaps via cold gas accretion scenarios. Interestingly, these bulges have sizes and mass densities comparable to the compact galaxies found at z ˜ 1.5 to 2.

The combined effect of AGN and supernovae feedback in launching massive molecular outflows in high-redshift galaxies

NASA Astrophysics Data System (ADS)

Biernacki, Pawel; Teyssier, Romain

2018-04-01

We have recently improved our model of active galactic nucleus (AGN) by attaching the supermassive black hole (SMBH) to a massive nuclear star cluster (NSC). Here, we study the effects of this new model in massive, gas-rich galaxies with several simulations of different feedback recipes with the hydrodynamics code RAMSES. These simulations are compared to a reference simulation without any feedback, in which the cooling halo gas is quickly consumed in a burst of star formation. In the presence of strong supernovae (SN) feedback, we observe the formation of a galactic fountain that regulates star formation over a longer period, but without halting it. If only AGN feedback is considered, as soon as the SMBH reaches a critical mass, strong outflows of hot gas are launched and prevent the cooling halo gas from reaching the disc, thus efficiently halting star formation, leading to the so-called `quenching'. If both feedback mechanisms act in tandem, we observe a non-linear coupling, in the sense that the dense gas in the supernovae-powered galactic fountain is propelled by the hot outflow powered by the AGN at much larger radii than without AGN. We argue that these particular outflows are able to unbind dense gas from the galactic halo, thanks to the combined effect of SN and AGN feedback. We speculate that this mechanism occurs at the end of the fast growing phase of SMBH, and is at the origin of the dense molecular outflows observed in many massive high-redshift galaxies.

DYNAMICS OF TIDALLY CAPTURED PLANETS IN THE GALACTIC CENTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trani, Alessandro A.; Bressan, Alessandro; Mapelli, Michela

2016-11-01

Recent observations suggest ongoing planet formation in the innermost parsec of the Galactic center. The supermassive black hole (SMBH) might strip planets or planetary embryos from their parent star, bringing them close enough to be tidally disrupted. Photoevaporation by the ultraviolet field of young stars, combined with ongoing tidal disruption, could enhance the near-infrared luminosity of such starless planets, making their detection possible even with current facilities. In this paper, we investigate the chance of planet tidal captures by means of high-accuracy N -body simulations exploiting Mikkola's algorithmic regularization. We consider both planets lying in the clockwise (CW) disk andmore » planets initially bound to the S-stars. We show that tidally captured planets remain on orbits close to those of their parent star. Moreover, the semimajor axis of the planetary orbit can be predicted by simple analytic assumptions in the case of prograde orbits. We find that starless planets that were initially bound to CW disk stars have mild eccentricities and tend to remain in the CW disk. However, we speculate that angular momentum diffusion and scattering by other young stars in the CW disk might bring starless planets into orbits with low angular momentum. In contrast, planets initially bound to S-stars are captured by the SMBH on highly eccentric orbits, matching the orbital properties of the clouds G1 and G2. Our predictions apply not only to planets but also to low-mass stars initially bound to the S-stars and tidally captured by the SMBH.« less

Clarification of the formation process of the super massive black hole by Infrared astrometric satellite, Small-JASMINE

NASA Astrophysics Data System (ADS)

Yano, Taihei; JASMINE-WG

2018-04-01

Small-JASMINE (hearafter SJ), infrared astrometric satellite, will measure the positions and the proper motions which are located around the Galactic center, by operating at near infrared wave-lengths. SJ will clarify the formation process of the super massive black hole (hearafter SMBH) at the Galactic center. In particular, SJ will determine whether the SMBH was formed by a sequential merging of multiple black holes. The clarification of this formation process of the SMBH will contribute to a better understanding of merging process of satellite galaxies into the Galaxy, which is suggested by the standard galaxy formation scenario. A numerical simulation (Tanikawa and Umemura, 2014) suggests that if the SMBH was formed by the merging process, then the dynamical friction caused by the black holes have influenced the phase space distribution of stars. The phase space distribution measured by SJ will make it possible to determine the occurrences of the merging process.

Influence of toroidal magnetic field in multiaccreting tori

NASA Astrophysics Data System (ADS)

Pugliese, D.; Montani, G.

2018-06-01

We analysed the effects of a toroidal magnetic field in the formation of several magnetized accretion tori, dubbed as ringed accretion discs (RADs), orbiting around one central Kerr supermassive black hole (SMBH) in active galactic nuclei (AGNs), where both corotating and counterotating discs are considered. Constraints on tori formation and emergence of RADs instabilities, accretion on to the central attractor and tori collision emergence, are investigated. The results of this analysis show that the role of the central BH spin-mass ratio, the magnetic field and the relative fluid rotation and tori rotation with respect the central BH, are crucial elements in determining the accretion tori features, providing ultimately evidence of a strict correlation between SMBH spin, fluid rotation, and magnetic fields in RADs formation and evolution. More specifically, we proved that magnetic field and discs rotation are in fact strongly constrained, as tori formation and evolution in RADs depend on the toroidal magnetic fields parameters. Eventually, this analysis identifies specific classes of tori, for restrict ranges of magnetic field parameter, that can be observed around some specific SMBHs identified by their dimensionless spin.

Central structures of Seyfert galaxy NGC 1672

NASA Astrophysics Data System (ADS)

Firpo, V.; Díaz, R.; Dottori, H.; Aguero, M. P.; Bosch, G.; Hagele, G.; Cardaci, M.; Dors, O.

2017-10-01

We present the velocity field of the inner 4"(350 pc) of NGC1672, observed with Gemini GMOS/IFU with a spatial sampling of 0.2", spatial resolution of 0.4", and spectral resolution 6000. We determine an upper limit for the mass of the SMBH in the LINER core using the ionized gas radial velocity field, and we confirmed that the active galactic nucleus is located off-center respect to the circumnuclear disk rotation symmetry center.

Making Supermassive Black Holes Spin

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

Where does the angular momentum come from that causes supermassive black holes (SMBHs) to spin on their axes and launch powerful jets? A new study of nearby SMBHs may help to answer this question.High-mass SMBHs are thought to form when two galaxies collide and the SMBHs at their centers merge. [NASA/Hubble Heritage Team (STScI)]High- vs. Low-Mass MonstersObservational evidence suggests a dichotomy between low-mass SMBHs (those with 106-7 M) and high-mass ones (those with 108-10 M). High-mass SMBHs are thought to form via the merger of two smaller black holes, and the final black hole is likely spun up by the rotational dynamics of the merger. But what spins up low-mass SMBHs, which are thought to build up very gradually via accretion?A team of scientists led by Jing Wang (National Astronomical Observatories, Chinese Academy of Sciences) have attempted to address this puzzle by examining the properties of the galaxies hosting low-mass SMBHs.A Sample of Neighboring SMBHsWang and collaborators began by constructing a sample of radio-selected nearby Seyfert 2 galaxies: those galaxies in which the stellar population and morphology of the host galaxy are visible to us, instead of being overwhelmed by continuum emission from the galaxys active nucleus.An example of a galaxy with a concentrated, classical bulge (M87; top) and a one with a disk-like pseudo bulge (Triangulum Galaxy; bottom). The authors find that for galaxies hosting low-mass SMBHs, those with more disk-like bulges appear to have more powerful radio jets. [Top: NASA/Hubble Heritage Team (STScI), Bottom: Hewholooks]From this sample, the authors then selected 31 galaxies that have low-mass SMBHs at their centers, as measured using the surrounding stellar dynamics. Wang and collaborators cataloged radio information revealing properties of the powerful jets launched by the SMBHs, and they analyzed the host galaxies properties by modeling their brightness profiles.Spin-Up From Accreting GasBy examining this sample, the authors discovered an intriguing relationship: the radio power of jets launched by an SMBH appears to be dependent upon its host galaxys bulge surface brightness. Specifically, Wang and collaborators found that more powerful radio emission comes from SMBHs associated with less-concentrated bulges, i.e. those that are more disk-like.The authors findings allow them to rule out many common explanations for the radio-loudness of such galaxies with small SMBH masses. Instead, they argue that the tendency for galaxies with more disk-like bulges to host SMBHs with more powerful jets is evidence that low-mass SMBHs are spun up by the accretion of surrounding gas.In this scenario, the angular momentum of gas with significant disk-like rotational dynamics provides the spin to the SMBH, and this rotational energy can then be extracted to launch the powerful jets. If this explanation is correct, it strengthens the dichotomy between low-mass and high-mass SMBHs, supporting the idea that the two categories of black holes are indeed formed and spun up via completely different mechanisms.CitationJ. Wang et al 2016 ApJL 833 L2.doi:10.3847/2041-8205/833/1/L2

Bondi or not Bondi: the impact of resolution on accretion and drag force modelling for Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Beckmann, R. S.; Slyz, A.; Devriendt, J.

2018-04-01

Whilst in galaxy-size simulations, supermassive black holes (SMBH) are entirely handled by sub-grid algorithms, computational power now allows the accretion radius of such objects to be resolved in smaller scale simulations. In this paper, we investigate the impact of resolution on two commonly used SMBH sub-grid algorithms; the Bondi-Hoyle-Lyttleton (BHL) formula for accretion onto a point mass, and the related estimate of the drag force exerted onto a point mass by a gaseous medium. We find that when the accretion region around the black hole scales with resolution, and the BHL formula is evaluated using local mass-averaged quantities, the accretion algorithm smoothly transitions from the analytic BHL formula (at low resolution) to a supply limited accretion (SLA) scheme (at high resolution). However, when a similar procedure is employed to estimate the drag force it can lead to significant errors in its magnitude, and/or apply this force in the wrong direction in highly resolved simulations. At high Mach numbers and for small accretors, we also find evidence of the advective-acoustic instability operating in the adiabatic case, and of an instability developing around the wake's stagnation point in the quasi-isothermal case. Moreover, at very high resolution, and Mach numbers above M_∞ ≥ 3, the flow behind the accretion bow shock becomes entirely dominated by these instabilities. As a result, accretion rates onto the black hole drop by about an order of magnitude in the adiabatic case, compared to the analytic BHL formula.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; Berczik, Peter, E-mail: khan@ari.uni-heidelberg.de, E-mail: k.holley@vanderbilt.edu

Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the largemore » SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC 1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production.« less

THE PROPERTIES OF HYPERVELOCITY STARS AND S-STARS ORIGINATING FROM AN ECCENTRIC DISK AROUND A SUPERMASSIVE BLACK HOLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Šubr, Ladislav; Haas, Jaroslav, E-mail: subr@sirrah.troja.mff.cuni.cz, E-mail: haas@sirrah.troja.mff.cuni.cz

2016-09-01

Hypervelocity stars (HVSs), which are observed in the Galactic halo, are believed to be accelerated to large velocities by a process of tidal disruption of binary stars passing close to the supermassive black hole (SMBH) which resides in the center of the Galaxy. It is, however, still unclear where these relatively young stars were born and what dynamical process pushed them to nearly radial orbits around the SMBH. In this paper we investigate the possibility that the young binaries originated from a thin eccentric disk, similar to the one currently observed in the Galactic center. By means of direct Nmore » -body simulations, we follow the dynamical evolution of an initially thin and eccentric disk of stars with a 100% binary fraction orbiting around the SMBH. Such a configuration leads to Kozai–Lidov oscillations of orbital elements, bringing a considerable number of binaries to the close vicinity of the black hole. Subsequent tidal disruption of these binaries accelerates one of their components to velocities well above the escape velocity from the SMBH, while the second component becomes tightly bound to the SMBH. We describe the main kinematic properties of the escaping and tightly bound stars within our model, and compare them qualitatively to the properties of the observed HVSs and S-stars, respectively. The most prominent feature is strong anisotropy in the directions of the escaping stars, which is observed for Galactic HVSs but has not yet been explained.« less

Probing Strong-field General Relativity with Gravitational Waves

NASA Astrophysics Data System (ADS)

Pretorius, Frans

We are on the verge of a new era in astrophysics as a world-wide effort to observe the universe with gravitational waves takes hold---ground based laser interferometers (Hz to kHz), pulsar timing (micro to nano Hz), measurements of polarization of the cosmic microwave background (sub-nano Hz), and the planned NASA/ESA mission LISA (.1 mHz to .1 Hz). This project will study the theoretical nature of gravitational waves (GWs) emitted by two sources in the LISA band, namely supermassive-black-hole (SMBH) binary mergers, and extreme-mass-ratio-inspirals (EMRI's)---the merger of a stellar mass black hole, neutron star, or white dwarf with a SMBH. The primary goal will be to ascertain how well LISA, by observing these sources, could answer the following related questions about the fundamental nature of strong-field gravity: Does Einstein's theory of general relativity (GR) describe the geometry of black holes in the universe? What constraints can GW observations of SMBH mergers and EMRIs place on alternative theories of gravity? If there are deviations from GR, are there statistics that could give indications of a deviation if sources are detected using a search strategy based solely on GR waveforms? The primary reasons for focusing on LISA sources to answer these questions are (a) binary SMBH mergers could be detected by LISA with exquisitely high signal-to- noise, allowing enough parameters of the system to be accurately extracted to perform consistency checks of the underlying theory, (b) EMRIs will spend numerous orbits close to the central black hole, and thus will be quite sensitive to even small near-horizon deviations from GR. One approach to develop the requisite knowledge and tools to answer these questions is to study a concrete, theoretically viable alternative to GR. We will focus on the dynamical variant of Chern-Simons modified gravity (CSMG), which is interesting for several reasons, chief among which are (1) that CSMG generically arises in both string theory and loop quantum gravity, and (2) that although CSMG is consistent with all present day tests of GR, it still allows for significant, near-horizon deformations in the geometry of rotating (Kerr) black holes. Here is a brief list of the steps and research methodology we will employ:
(i) Obtain the equivalent of the full Kerr solution in CSMG using numerical methods. (ii) Explore the structure of GWs emitted by EMRIs about the CS rotating black hole solution. Given simulated LISA noise curves, we can then address the questions posed above within the context of CSMG. (iii) Simulate the latter stages of comparable mass SMBH binary mergers in CSMG by numerically solving the full CSMG field equations to learn about highly dynamical, non- linear GR deformations. We can then repeat the analysis of (ii). (iv) Study whether CSMG GWs fit in the recently proposed parameterized post- Einsteinian (ppE) framework, to study generic deviations from GR in a statistical fashion. One can then repeat the analysis of (ii) but within the ppE scheme. We believe this proposed work is of significance and import to both the objectives of this solicitation, and the interests of NASA---knowing the nature of strong-field gravity will be one of the keys to unraveling the origin of the universe, and will tell us how black holes behave and interact with their environs, the details of which are important in understanding the formation and evolution of structure in the universe. Furthermore, these questions are best suited to be answered by LISA, a planned joint NASA-ESA mission. The ultimate success of LISA is very much dependent on (amongst other things) how well the community understands the complete nature of gravitational wave sources.

Radiative Hydrodynamic Simulations of In Situ Star Formation in the Galactic Center

NASA Astrophysics Data System (ADS)

Frazer, Chris; Heitsch, Fabian

2018-01-01

Many stars observed in the Galactic Center (GC) orbit the supermassive black hole (SMBH), Sagittarius A*, in a region where the extreme gravitational field is expected to inhibit star formation. Yet, many of these stars are young which favors an in situ formation scenario. Previous numerical work on this topic has focused on two possible solutions. First, the tidal capture of a > 10^4 Msun infalling molecular cloud by an SMBH may result in the formation of a surrounding gas disk which then rapidly cools and forms stars. This process results in stellar populations that are consistent with the observed stellar disk in the GC. Second, dense gas clumps of approximately 100 Msun on highly eccentric orbits about an SMBH can experience sparks of star formation via orbital compressions occurring during pericenter passage. In my dissertation, I build upon these models using a series of grid-based radiative hydrodynamic simulations, including the effects of both ionizing ultraviolet light from existing stars as well as X-ray radiation emanating from the central black hole. Radiation is treated with an adaptive ray-tracing routine, including appropriate heating and cooling for both neutral and ionized gas. These models show that ultraviolet radiation is sufficiently strong to heat low mass gas clouds, thus suppressing star formation from clump compression. Gas disks that form from cloud capture become sufficiently dense to provide shielding from the radiation of existing central stars, thus allowing star formation to continue. Conversely, X-rays easily penetrate and heat the potentially star forming gas. For sufficiently high radiation fields, this provides a mechanism to disrupt star formation for both scenarios considered above.

Nustar Reveals the Extreme Properties of the Super-Eddington Accreting Supermassive Black Hole in PG 1247+267

NASA Technical Reports Server (NTRS)

Lanzuisi, G.; Perna, M.; Comastri, A.; Cappi, M.; Dadina, M.; Marinucci, A.; Masini, A.; Matt, G.; Vagnetti, F.; Vignali, C.;

The Compton-thick Growth of Supermassive Black Holes constrained

NASA Astrophysics Data System (ADS)

Buchner, Johannes; Georgakakis, Antonis; Nandra, Kirpal; Brightman, Murray; Menzel, Marie-Luise; Liu, Zhu; Hsu, Li-Ting; Salvato, Mara; Rangel, Cyprian; Aird, James

2017-08-01

A heavily obscured growth phase of supermassive black holes (SMBH) is thought to be important in the co-evolution with galaxies. X-rays provide a clean and efficient selection of unobscured and obscured AGN. Recent work with deeper observations and improved analysis methodology allowed us to extend constraints to Compton-thick number densities. We present the first luminosity function of Compton-thick AGN at z=0.5-4 and constrain the overall mass density locked into black holes over cosmic time, a fundamental constraint for cosmological simulations. Recent studies including ours find that the obscuration is redshift and luminosity-dependent in a complex way, which rules out entire sets of obscurer models. A new paradigm, the radiation-lifted torus model, is proposed, in which the obscurer is Eddington-rate dependent and accretion creates and displaces torus clouds. We place observational limits on the behaviour of this mechanism.

The Compton-thick Growth of Supermassive Black Holes constrained

NASA Astrophysics Data System (ADS)

Buchner, J.; Georgakakis, A.; Nandra, K.

2017-10-01

A heavily obscured growth phase of supermassive black holes (SMBH) is thought to be important in the co-evolution with galaxies. X-rays provide a clean and efficient selection of unobscured and obscured AGN. Recent work with deeper observations and improved analysis methodology allowed us to extend constraints to Compton-thick number densities. We present the first luminosity function of Compton-thick AGN at z=0.5-4 and constrain the overall mass density locked into black holes over cosmic time, a fundamental constraint for cosmological simulations. Recent studies including ours find that the obscuration is redshift and luminosity-dependent in a complex way, which rules out entire sets of obscurer models. A new paradigm, the radiation-lifted torus model, is proposed, in which the obscurer is Eddington-rate dependent and accretion creates and displaces torus clouds. We place observational limits on the behaviour of this mechanism.

Indirect (source-free) integration method. I. Wave-forms from geodesic generic orbits of EMRIs

NASA Astrophysics Data System (ADS)

Ritter, Patxi; Aoudia, Sofiane; Spallicci, Alessandro D. A. M.; Cordier, Stéphane

2016-12-01

The Regge-Wheeler-Zerilli (RWZ) wave-equation describes Schwarzschild-Droste black hole perturbations. The source term contains a Dirac distribution and its derivative. We have previously designed a method of integration in time domain. It consists of a finite difference scheme where analytic expressions, dealing with the wave-function discontinuity through the jump conditions, replace the direct integration of the source and the potential. Herein, we successfully apply the same method to the geodesic generic orbits of EMRI (Extreme Mass Ratio Inspiral) sources, at second order. An EMRI is a Compact Star (CS) captured by a Super-Massive Black Hole (SMBH). These are considered the best probes for testing gravitation in strong regime. The gravitational wave-forms, the radiated energy and angular momentum at infinity are computed and extensively compared with other methods, for different orbits (circular, elliptic, parabolic, including zoom-whirl).

Central Stellar Mass Deficits in the Bulges of Local Lenticular Galaxies

NASA Astrophysics Data System (ADS)

Dullo, B. T.

2014-03-01

The centers of giant galaxies display stellar mass deficits (Mdef) which are thought to be a signature left by inspiraling supermassive black hole (SMBH) binaries that are formed in post-merger galaxies. We quantify these deficits for a sample of five luminous lenticular galaxies with bulge magnitude MV ≲ -21 mag and find Mdef ≍ 0.5 - 2MBH (black hole mass). Contrary to the traditionally proposed lenticular galaxy formation mechanisms such as ram-pressure stripping and galaxy harassment, the mass deficits in these galaxies suggest a two stage inside-out process for their assembly. That is, their bulges may have formed through “dry” major-merger events involving SMBHs while their disk was subsequently built up via cold gas accretion scenarios. Interestingly, these bulges have sizes and mass densities comparable to the compact massive galaxies found at z ˜ 2.

Astrophysics of Super-Massive Black Hole Mergers

NASA Technical Reports Server (NTRS)

Schnittman, Jeremy D.

2013-01-01

We present here an overview of recent work in the subject of astrophysical manifestations of super-massive black hole (SMBH) mergers. This is a field that has been traditionally driven by theoretical work, but in recent years has also generated a great deal of interest and excitement in the observational astronomy community. In particular, the electromagnetic (EM) counterparts to SMBH mergers provide the means to detect and characterize these highly energetic events at cosmological distances, even in the absence of a space-based gravitational-wave observatory. In addition to providing a mechanism for observing SMBH mergers, EM counterparts also give important information about the environments in which these remarkable events take place, thus teaching us about the mechanisms through which galaxies form and evolve symbiotically with their central black holes.

Dark-matter haloes and the M-σ relation for supermassive black holes

NASA Astrophysics Data System (ADS)

Larkin, Adam C.; McLaughlin, Dean E.

2016-10-01

We develop models of two-component spherical galaxies to establish scaling relations linking the properties of spheroids at z = 0 (total stellar masses, effective radii Re and velocity dispersions within Re) to the properties of their dark-matter haloes at both z = 0 and higher redshifts. Our main motivation is the widely accepted idea that the accretion-driven growth of supermassive black holes (SMBHs) in protogalaxies is limited by quasar-mode feedback and gas blow-out. The SMBH masses, MBH, should then be connected to the dark-matter potential wells at the redshift zqso of the blow-out. We specifically consider the example of a power-law dependence on the maximum circular speed in a protogalactic dark-matter halo: M_{BH}∝ V^4_{d,pk}, as could be expected if quasar-mode feedback were momentum-driven. For haloes with a given Vd,pk at a given zqso ≥ 0, our model scaling relations give a typical stellar velocity dispersion σap(Re) at z = 0. Thus, they transform a theoretical MBH-Vd,pk relation into a prediction for an observable MBH-σap(Re) relation. We find the latter to be distinctly non-linear in log-log space. Its shape depends on the generic redshift evolution of haloes in a Λ cold dark matter cosmology and the systematic variation of stellar-to-dark matter mass fraction at z = 0, in addition to any assumptions about the physics underlying the MBH-Vd,pk relation. Despite some clear limitations of the form we use for MBH versus Vd,pk, and even though we do not include any SMBH growth through dry mergers at low redshift, our results for MBH-σap(Re) compare well to data for local early types if we take zqso ˜ 2-4.

BLACK HOLE MASS AND EDDINGTON RATIO DISTRIBUTION FUNCTIONS OF X-RAY-SELECTED BROAD-LINE AGNs AT z {approx} 1.4 IN THE SUBARU XMM-NEWTON DEEP FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nobuta, K.; Akiyama, M.; Ueda, Y.

2012-12-20

In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z {approx} 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 A monochromatic luminosity. We supplement the Mg II FWHM values with the H{alpha} FWHM obtained from our NIRmore » spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V{sub max} method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF at z = 1.4 has a higher number density above 10{sup 8} M{sub Sun} but a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.« less

Monsters on the move: A search for supermassive black holes undergoing gravitational wave recoil

NASA Astrophysics Data System (ADS)

Jadhav, Yashashree; Robinson, Andrew; Lena, Davide

2018-01-01

There is compelling evidence that supermassive black holes (SMBH) reside at the centers of all large galaxies and are the gravitational ‘engines’ of Active Galactic Nuclei (AGN). Furthermore, galaxy mergers are thought to have played a fundamental role in the growth and evolution of the largest galaxies in the nearby universe. A galaxy merger is expected to lead to the formation of an SMBH binary, which itself eventually coalesces through the emission of gravitational waves. Such events fall outside the frequency range accessible to the LIGO/VIRGO gravitational wave detectors, but they can be detected via electromagnetic signatures. Numerical relativity simulations show that, depending on the initial spin-orbit configuration of the binary, the merged SMBH receives a gravitational recoil kick that may reach several 1000km/s. This recoil in turn causes the merged SMBH to oscillate for up to ~1 Gyr in the gravitational potential well of the galaxy. During this time, the recoiling SMBH may be observed as a ‘displaced’ AGN. Such events provide a strong test of gravitational physics and the formation and merger frequencies of binary SMBH. As a result of residual oscillations, displacements ~10 – 100pc may be expected even in nearby elliptical galaxies and can be measured as spatial offsets in high resolution optical or infrared images. We present the results of a preliminary study, in which isophotal analysis was conducted for a sample of 96 galaxies to obtain the photocenter of the galaxies using Hubble Space Telescope (HST) archival optical or infrared WFC2/PC, ACS or NICMOS images. The position of the nuclear point source (AGN) was also measured to obtain a displacement vector. This initial sample reveals 18 candidates that show a significant displacement. Of these, 14 are hosted by core ellipticals, while the rest have a cuspy light profile. As galactic and nuclear dust structures may interfere with the isophotal analysis, we are currently obtaining new WFC3 NIR images for selected candidates, in order to confirm the measured displacements. Preliminary results from these new images will also be presented.

SDSS J1056+5516: A Triple AGN or an SMBH Recoil Candidate?

NASA Astrophysics Data System (ADS)

Kalfountzou, E.; Santos Lleo, M.; Trichas, M.

2017-12-01

We report the discovery of a kiloparsec-scale triple supermassive black hole system at z = 0.256: SDSS J1056+5516, discovered by our systematic search for binary quasars. The system contains three strong emission-line nuclei, which are offset by < 250 {km} {{{s}}}-1 and by 15-18 kpc in projected separation, suggesting that the nuclei belong to the same physical structure. The system includes a tidal arm feature spanning ˜100 kpc in projected distance at the systems’ redshift, inhabiting an ongoing or recent galaxy merger. Based on our results, such a structure can only satisfy one of the three scenarios; a triple supermasive black hole (SMBH) interacting system, a triple AGN, or a recoiling SMBH. Each of these scenarios is unique for our understanding of the hierarchical growth of galaxies, AGN triggering, and gravitational waves.

The Potential for Cubesats to Determine Black Holes Masses in Nearby Active Galactic Nuclei and Contribute to Other Time Domain Science

NASA Astrophysics Data System (ADS)

Gorjian, Varoujan; Ardila, David R.; Barth, Aaron J.; Janson, Siegfried; Kochanek, Christopher S.; Malkan, Matthew Arnold; Peterson, Bradley M.; Rowen, Darren; Seager, Sara; Shkolnik, Evgenya L.

2016-01-01

A 3U (30cmx10cmx10cm) CubeSat with a 9cm diameter aperture telescope can deliver unprecedented time domain coverage in the ultraviolet (UV) for the purposes of Active Galactic Nucleus (AGN) reverberation mapping to determine supermassive black hole (SMBH) masses. SMBH's reside at the centers of most, if not all, massive galaxies and accretion onto those black holes generates a great deal of emission peaking in the UV. These accretion disks are also surrounded by a nearby, fast moving gas region called the Broad Line Region (BLR). As light pulses generated near the black hole spread out, they first illuminate the accretion disk, and then the BLR. For a sample of bright AGN, a dedicated cubesat can follow these changes in brightness on a daily basis for up to 100 days from low Earth orbit. With such monitoring of changes in the accretion disk and then the BLR, an accurate distance between the two regions can be determined. Combining this UV coverage with optical emission-line spectroscopy from the ground allows for a direct measurement of the mass of the central black hole. This exchange of time resolution for spatial resolution can also be used to determine the structure of the central region of the AGN. Ground-based photometric and spectroscopic measurements will complement the UV by tracing the optically emitting and hence cooler regions of the AGN to provide one of the best measurements of supermassive black hole masses.In addition to the primary science mission, the long observing campaigns and the large field of view required to get comparison stars for relative photometry allow for other competitive science. We have identified UV activity in M dwarfs as ancillary science that can be addressed with such a cubesat. This activity will have a strong impact on the habitability of any possible planet around the star.

A Particular Appetite: Cosmological Hydrodynamic Simulations of Preferential Accretion in the Supermassive Black Holes of Milky Way Size Galaxies

NASA Astrophysics Data System (ADS)

Sanchez, Natalie; Bellovary, Jillian M.; Holley-Bockelmann, Kelly

2016-01-01

With the use of cosmological hydrodynamic simulations of Milky Way-type galaxies, we identify the preferential source of gas that is accreted by the supermassive black holes (SMBHs) they host. We examine simulations of two Milky Way analogs, each distinguished by a differing merger history. One galaxy is characterized by several major mergers and the other has a more quiescent history. By examining and comparing these two galaxies, which have a similar structure at z=0, we asses the importance of merger history on black hole accretion. This study is an extension of Bellovary et. al. 2013, which studied accretion onto SMBHs in massive, high redshift galaxies. Bellovary found that the fraction of gas accreted by the galaxy was proportional to that which was accreted by its SMBH. Contrary to Bellovary's previous results, we found that though the gas accreted by a quiescent galaxy will mirror the accretion of its central SMBH, a galaxy that is characterized by an active merger history will have a SMBH that preferentially accretes gas gained through mergers. We move forward by examining the angular momentum of the gas accreted by these Milky Way-type galaxies to better understand the mechanisms fueling their central SMBH.

On the possibility that ultra-light boson haloes host and form supermassive black holes

NASA Astrophysics Data System (ADS)

Avilez, Ana A.; Bernal, Tula; Padilla, Luis E.; Matos, Tonatiuh

2018-07-01

Several observations suggest the existence of supermassive black holes (SMBH) at the centres of galaxies. However, the mechanism under which these objects form remains non-completely understood. In this work, we review an alternative mechanism of formation of galactic SMBHs from the collapse of a fraction of a dark matter (DM) halo made of an ultra-light scalar field (SF) whose critical mass of collapse is ˜1013 M⊙. Once the BH is formed, a long-living quasi-resonant SF configuration survives and plays the role of a central fraction of the galactic DM halo. In this work, we construct a model with an ultra-light SF configuration laying in a Schwarzschild space-time to describe the centre of the DM halo hosting an SMBH in equilibrium, in the limit where self-gravitating effects can be neglected. We compute the induced stellar velocity dispersion in order to investigate the influence of the BH on to the velocity field of visible matter at the central galactic regions. We fit the empirical correlation between stellar velocity dispersions and masses of SMBHs considering two instances: the idealized case of DM-dominated (DMD) systems, where the gravitational influence of baryons is neglected, and cases of real luminous galaxies (LGAL). In the DMD case, we found it is possible to reproduce the observed stellar velocity dispersions at the effective radius of systems hosting SMBHs of at most 108 M⊙. In the LGAL case, we found that the baryons are crucial to reproduce the observed velocity dispersion.

Spectral features of tidal disruption candidates and alternative origins for such transient flares

NASA Astrophysics Data System (ADS)

Saxton, Curtis J.; Perets, Hagai B.; Baskin, Alexei

2018-03-01

UV and optically selected candidates for stellar tidal disruption events (TDEs) often exhibit broad spectral features (He II emission, H α emission, or absorption lines) on a blackbody-like continuum (104 K≲ T≲ 105 K). The lines presumably emit from TDE debris or circumnuclear clouds photoionized by the flare. Line velocities however are much lower than expected from a stellar disruption by supermassive black hole (SMBH), and are somewhat faster than expected for the broad line region (BLR) clouds of a persistently active galactic nucleus (AGN). The distinctive spectral states are not strongly related to observed luminosity and velocity, nor to SMBH mass estimates. We use exhaustive photoionization modelling to map the domain of fluxes and cloud properties that yield (e.g.) an He-overbright state where a large He II(4686 Å)/H α line ratio creates an illusion of helium enrichment. Although observed line ratios occur in a plausible minority of cases, AGN-like illumination cannot reproduce the observed equivalent widths. We therefore propose to explain these properties by a light-echo photoionization model: the initial flash of a hot blackbody (detonation) excites BLR clouds, which are then seen superimposed on continuum from a later, expanded, cooled stage of the luminous source. The implied cloud mass is substellar, which may be inconsistent with a TDE. Given these and other inconsistencies with TDE models (e.g. host-galaxies distribution) we suggest to also consider alternative origins for these nuclear flares, which we briefly discuss (e.g. nuclear supernovae and starved/subluminous AGNs).

Extragalactic circuits, transmission lines, and CR particle acceleration

NASA Astrophysics Data System (ADS)

Kronberg, Philipp P.; Lovelace, Richard V. E.

2015-08-01

A non-negligible fraction of a Supermassive Black Hole's (SMBH) rest mass energy gets transported into extragalactic space by a remarkable process in jets which are incompletely understood. What are the physical processes which transport this energy? It is likely that the energy flows electromagnetically, rather than via a particle beam flux. The deduced electromagnetic fields may produce particles of energy as high as ˜ 1020 eV. The energetics of SMBH accretion disk models and the electromagnetic energy transfer imply that a SMBH should generate a 1018 - 1019 Ampères current close to the black hole and its accretion disk. We describe the so far best observation-based estimate of the magnitude of the current flow along the axis of the jet extending from the nucleus of the active galaxy in 3C303. The current is measured to be I ˜ 1018 Ampères at ˜ 40 kpc away from the AGN. This indicates that organised current flow remains intact over multi-kpc distances. The electric current I transports electromagnetic power into free space, P = I2Z, where Z ˜ 30 Ohms is related to the impedance of free space, and this points to the existence of cosmic electric circuit. The associated electric potential drop, V = IZ, is of the order of that required to generate Ultra High Energy Cosmic Rays (UHECR). We also explore further implications, including disruption/deflection of the power flow and also why such measurements, exemplified by those on 3C303, are currently very difficult to make and to unambiguously interpret. This naturally leads to the topic of how such measurements can be extended and improved in the future. We describe the analogy of electromagnetically dominated jets with transmission lines. High powered jets in vacuo can be understood by approximate analogy with a waveguide. The importance of inductance, impedance, and other laboratory electrical concepts are discussed in this context.

Investigating Supermassive Black Hole Spin at Different Redshift

NASA Astrophysics Data System (ADS)

Sinanan-Singh, Jasmine

2018-01-01

Supermassive black hole (SMBH) spin encodes vital information about the history of SMBH growth. High spins indicate a history of growth through large mass accretion events, which spin-up the black hole; Intermediate spins indicate a history of galactic mergers, which don't tend to systemcatically spin-up or spin-down black holes; low spins are attributed to successive, small accretion events with random orientations. Examining spin over different redshifts will help us understand the relative growth of SMBHs by mergers or accretion over cosmic time, an important part of understanding how SMBHs and their host galaxies co-evolved over time. To study spin, we compute the Fe K alpha emission line from the X-ray spectra of AGN sources in the Chandra-COSMOS Legacy Survey. We stack rest frame AGN spectra to improve the signal-to-noise ratio since the photon counts are low for individual spectra, and then average the spectra using an unwieghted mean. Our method is derived from Corral et al. (2008). We test our method on the two brightest sources in the COSMOS Survey and compute the rest frame average Fe K alpha emission line for different redshift bins. The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

The star-forming properties of an ultra-hard x-ray selected sample of active galactic nuclei

NASA Astrophysics Data System (ADS)

Shimizu, Thomas Taro

This thesis provides a comprehensive examination of star formation in the host galaxies of active galactic nuclei or AGN. AGN are bright, central regions of galaxies that are powered through accretion onto a supermassive black hole (SMBH). Through accretion and the loss of gravitational potential energy, AGN emit powerful radiation over all wavelengths of the electromagnetic spectrum. This radiation can influence the AGN's host galaxy through what is known as AGN ``feedback'' and is thought to suppress star formation as well as stop accretion onto the SMBH leading to a co-evolution between the SMBH and its host galaxy. Theoretical models have long invoked AGN feedback to be able reproduce the galaxy population we see today but observations have been unclear as to whether AGN actually have an effect on star formation. To address this question, we selected a large sample of local ( z < 0.05) AGN based on their detection at ultra-hard X-ray energies (14-195 keV) with the Swift Burst Alert Telescope (BAT). Ultra-hard X-ray selection frees our sample from selection effects and biases due to obscuration and host galaxy contamination that can hinder other AGN samples. With these 313 BAT AGN we conducted a far-infrared survey using the HerschelSpace Observatory. We use the far-infrared imaging to probe the cold dust that traces recent star formation in the galaxy and construct spectral energy distributions (SEDs) from 12-500 \\micron. We decompose the SEDs to remove the AGN contribution and measure infrared luminosity which provides us with robust estimates of the star formation rate (SFR). Through a comparison with a stellar-mass matched non-AGN sample, we find that AGN host galaxies have larger dust masses, dust temperatures, and SFRs, confirming the results of previous studies that showed the optical colors of the BAT AGN are bluer than non-AGN. We find that the AGN luminosity as probed by the 14-195 keV luminosity is not related to the SFR of the host galaxy suggesting global, large scale star formation on an individual basis is not affected by the AGN. However, after a thorough analysis comparing our AGN to star-forming main sequence, a tight relationship between the SFR and stellar mass of a galaxy, we discover that our AGN as a whole show systematically lower specific SFRs (SFR/stellar mass). We confirm that AGN host galaxies, as a population, are transitioning between the star-forming and quiescent populations. This result supports the theory that AGN feedback has suppressed star formation, but we also consider other models that could reproduce our observations. Finally we conclude with a summary of this thesis and describe several ongoing and future projects that will push forward the exciting field of AGN research.

Formation of Offset and Dual Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Barrows, Scott; Comerford, Julia M.; Greene, Jenny E.

2018-06-01

Galaxy mergers are effective mechanisms for triggering accretion onto supermassive black holes (SMBHs) and thereby powering active galactic nuclei (AGN). In the merger scenario, when the SMBH from only one galaxy is accreting we observe a spatially offset AGN, and when the SMBHs from both galaxies are accreting we observe a dual AGN. Understanding the merger conditions that lead to the formation of offset AGN versus dual AGN is fundamental to informing models of hierarchical SMBH growth and the physics leading to the accretion of matter onto SMBHs. However, while the role of galaxy mergers for AGN triggering has been well-studied, the efficiency with which these events trigger offset AGN versus dual AGN is currently unclear. One reason for this gap in knowledge can be attributed to the observational difficulties in distinguishing between offset and dual AGN since doing so requires high spatial resolution, especially in the small separation regime where merger-driven AGN triggering is most likely to occur. To overcome this hurdle, we have utilized the spatial resolution of the Chandra X-ray Observatory to develop a unique sample of AGN hosted by late-stage galaxy mergers. Moreover, we have recently acquired Hubble Space Telescope imaging for a subset of these systems to examine the role that their merger morphologies play in SMBH growth and the formation of offset and dual AGN. We find that offset AGN are predominately found in minor mergers, whereas dual AGN are usually hosted by major mergers and galaxies with large morphological asymmetries. Furthermore, in both offset and dual AGN, the rate of SMBH growth increases toward more major mergers and larger morphological asymmetries. These results are in agreement with numerical simulations predicting that merger morphology is a relevant parameter governing SMBH merger-driven growth, and these results are the first to observationally confirm these trends at small pair separations.

2MASS J00423991+3017515: An AGN On The Run?

NASA Astrophysics Data System (ADS)

Hogg, James

2016-09-01

We have discovered a peculiar AGN, 2MASS J00423991+3017515, in a local (z=0.14), disturbed galaxy whose optical spectrum has multiple broad lines that are consistently offset from the narrow line emission and host galaxy absorption by 1530 km/s. The morphology of the host galaxy and spectral properties thus suggest this AGN may be a recoiling supermassive black hole (SMBH). We propose high-resolution X-ray imaging and spectral follow-ups with the ACIS camera on Chandra to determine if the source of the kinematically-offset broad line emission is also spatially offset from the nucleus of the host galaxy. If a single, spatially offset AGN is detected, this source will be strongest candidate for a recoiling AGN candidate discovered to date.

Influence of conservative corrections on parameter estimation for extreme-mass-ratio inspirals

NASA Astrophysics Data System (ADS)

Huerta, E. A.; Gair, Jonathan R.

2009-04-01

We present an improved numerical kludge waveform model for circular, equatorial extreme-mass-ratio inspirals (EMRIs). The model is based on true Kerr geodesics, augmented by radiative self-force corrections derived from perturbative calculations, and in this paper for the first time we include conservative self-force corrections that we derive by comparison to post-Newtonian results. We present results of a Monte Carlo simulation of parameter estimation errors computed using the Fisher matrix and also assess the theoretical errors that would arise from omitting the conservative correction terms we include here. We present results for three different types of system, namely, the inspirals of black holes, neutron stars, or white dwarfs into a supermassive black hole (SMBH). The analysis shows that for a typical source (a 10M⊙ compact object captured by a 106M⊙ SMBH at a signal to noise ratio of 30) we expect to determine the two masses to within a fractional error of ˜10-4, measure the spin parameter q to ˜10-4.5, and determine the location of the source on the sky and the spin orientation to within 10-3 steradians. We show that, for this kludge model, omitting the conservative corrections leads to a small error over much of the parameter space, i.e., the ratio R of the theoretical model error to the Fisher matrix error is R<1 for all ten parameters in the model. For the few systems with larger errors typically R<3 and hence the conservative corrections can be marginally ignored. In addition, we use our model and first-order self-force results for Schwarzschild black holes to estimate the error that arises from omitting the second-order radiative piece of the self-force. This indicates that it may not be necessary to go beyond first order to recover accurate parameter estimates.

ALMA Observations Show Major Mergers Among the Host Galaxies of Fast-growing, High-redshift​ Supermassive​ Black Holes

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Lira, Paulina; Netzer, Hagai; Cicone, Claudia; Maiolino, Roberto; Shemmer, Ohad

2017-02-01

We present new ALMA band-7 data for a sample of six luminous quasars at z≃ 4.8, powered by fast-growing supermassive black holes (SMBHs) with rather uniform properties: the typical accretion rates and black hole masses are L/{L}{Edd}≃ 0.7 and {M}{BH}≃ {10}9 {M}⊙ . Our sample consists of three “FIR-bright” sources, which were individually detected in previous Herschel/SPIRE observations, with star formation rates of {SFR}> 1000 {M}⊙ {{yr}}-1, and three “FIR-faint” sources for which Herschel stacking analysis implies a typical SFR of ˜400 {M}⊙ {{yr}}-1. The dusty interstellar medium in the hosts of all six quasars is clearly detected in the ALMA data and resolved on scales of ˜2 kpc, in both continuum ({λ }{rest}˜ 150 μ {{m}}) and [{{C}} {{II}}] λ 157.74 μ {{m}} line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the quasar hosts. Importantly, we detect companion sub-millimeter galaxies (SMGs) for three sources—one FIR-bright and two FIR-faint, separated by ˜ 14{--}45 {kpc} and < 450 {km} {{{s}}}-1 from the quasar hosts. The [{{C}} {{II}}]-based dynamical mass estimates for the interacting SMGs are within a factor of ˜3 of the quasar hosts’ masses, while the continuum emission implies {{SFR}}{quasar}˜ (2{--}11)× {{SFR}}{SMG}. Our ALMA data therefore clearly support the idea that major mergers are important drivers for rapid early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs and the gas kinematics as observed by ALMA suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.

AGN contribution to the total IR luminosity in Herschel selected galaxies out to z~1.5

NASA Astrophysics Data System (ADS)

Baronchelli, Ivano; Scarlata, Claudia; Rodighiero, Giulia; Berta, Stefano; Sedgwick, Christopher; Vaccari, Mattia; Franceschini, Alberto; Urrutia, Tanya; Malkan, Matthew Arnold; Salvato, Mara; Bonato, Matteo; Serjeant, Stephen; Pearson, Chris; Marchetti, Lucia

2016-01-01

In the past decade, a growing amount of evidence suggests a tight link between the growth of Active Galactic Nuclei (AGN) and that of their host galaxies. X-ray studies on the Super Massive Black Holes (SMBHs) activity indicate the existence of a Black Hole Accretion Rate (BHAR) "main sequence", similar to the "main sequence" observed in star-forming galaxies, between the star-formation rate (SFR) and stellar mass (M*). We use the multi wavelength data from the SIMES survey to study the optical to sub-mm spectral energy distribution (SED) of galaxies identified at 250 μm by the Herschel Space Observatory. In particular, for galaxies in the 0.2-1.5 redshift range, we explore the relations among galaxy's stellar mass, SFR, and SMBH accretion rate. The deep Spitzer-IRAC/MIPS (3.6, 4.5 and 24 μm) together with the deep AKARI-IRC observations (7, 11 and 15 μm) allow us to constrain the critical spectral region where the dusty torus emission of AGNs is more prominent. Thanks to the Herschel-SPIRE observations, we can also precisely measure the SFR from the bolometric (i.e. 8-1000 μm) far-IR emission. Using this multi-wavelength approach we confirm the existence, at z<0.5, of the M*-BHAR "main sequence". The measured average ratio between BHAR and SFR is close to the value required to maintain the SMBH-to-M* ratio of ˜103 and decreases at higher specific SFRs (SSFR=SFR/M*). Finally, combining our observations with literature results, we show that the slope of the BHAR main sequence is evolving with redshift between z~0 and z~2.

Cosmic evolution of stellar quenching by AGN feedback: clues from the Horizon-AGN simulation

NASA Astrophysics Data System (ADS)

Beckmann, R. S.; Devriendt, J.; Slyz, A.; Peirani, S.; Richardson, M. L. A.; Dubois, Y.; Pichon, C.; Chisari, N. E.; Kaviraj, S.; Laigle, C.; Volonteri, M.

2017-11-01

The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Λ cold dark matter paradigm. In this paper, we investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M* ≥ 1011 M⊙) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 M⊙ ≤ M* ≤ 1011 M⊙, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M* ≥ 1011 M⊙, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the MSMBH-M* relation with redshift, particularly for galaxies with M* ≤ 1010 M⊙. MSMBH/M* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.

Revisiting hypervelocity stars after Gaia DR2

NASA Astrophysics Data System (ADS)

Boubert, D.; Guillochon, J.; Hawkins, K.; Ginsburg, I.; Evans, N. W.; Strader, J.

2018-06-01

Hypervelocity stars are intriguing rare objects traveling at speeds large enough to be unbound from the Milky Way. Several mechanisms have been proposed for producing them, including the interaction of the Galaxy's super-massive black hole (SMBH) with a binary; rapid mass-loss from a companion to a star in a short-period binary; the tidal disruption of an infalling galaxy and finally ejection from the Large Magellanic Cloud. While previously discovered high-velocity early-type stars are thought to be the result of an interaction with the SMBH, the origin of high-velocity late type stars is ambiguous. The second data release of Gaia (DR2) enables a unique opportunity to resolve this ambiguity and determine whether any late-type candidates are truly unbound from the Milky Way. In this paper, we utilize the new proper motion and velocity information available from DR2 to re-evaluate a collection of historical data compiled on the newly-created Open Fast Stars Catalog. We find that almost all previously-known high-velocity late-type stars are most likely bound to the Milky Way. Only one late-type object (LAMOST J115209.12+120258.0) is unbound from the Galaxy. Performing integrations of orbital histories, we find that this object cannot have been ejected from the Galactic centre and thus may be either debris from the disruption of a satellite galaxy or a disc runaway.

The Growth of Stellar Mass Black Hole Binaries Trapped in the Accretion Disks of Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Yi, Shu-Xu; Cheng, K. S.; Taam, Ronald E.

2018-06-01

Among the four black hole (BH) binary merger events detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), six progenitor BHs have masses greater than 20 M ⊙. The existence of such massive BHs suggests that extreme metal-poor stars are the progenitors. An alternative possibility, that a pair of stellar mass BHs each with mass ∼7 M ⊙ increases to >20 M ⊙ via accretion from a disk surrounding a supermassive BH (SMBH) in an active galactic nucleus (AGN), is considered. The growth of mass of the binary and the transfer of orbital angular momentum to the disk accelerates the merger. Based on the recent numerical work of Tang et al., it is found that, in the disk of a low-mass AGN with mass ∼106 M ⊙ and Eddington ratio >0.01, the mass of an individual BH in the binary can grow to >20 M ⊙ before coalescence, provided that accretion takes place at a rate more than 10 times the Eddington value. This mechanism predicts a new class of gravitational wave (GW) sources involving the merger of two extreme Kerr black holes associated with AGNs and a possible electromagnetic wave counterpart.

Gravitational Waves From The Hierarchical Buildup Of Intermediate Mass Black Holes

NASA Astrophysics Data System (ADS)

Micic, Miroslav; Sigurdsson, S.; Holley-Bockelmann, K.; Abel, T.

2006-12-01

Using high-resolution N-body simulations in LambdaCDM universe, we have constructed dark matter structure's merger tree that traces evolution of dark matter halos, their subhalos and massive black holes (MBH) formed from Population III stars. Such early black holes, formed at redshifts z > 10, could be the seed black holes for the many SMBH found in galaxies in the local universe. Mergers of MBH may be a prime signal for long wavelength gravitaional wave detectors. We study trajectories of MBH, formation of MBH binaries and calculate gravitational strain amplitude as a function of redshift. We also explore the implications of kick velocities conjectured by some formation models. The central concentration of early black holes in present day galaxies is reduced if they are born even with moderate kicks of tens km/s. The modest kicks allow the black holes to leave their parent halo, which consequently leads to dynamical friction being less effective on the lower mass black holes as compared to those still embedded in their parent halos. Therefore, merger rates may be reduced by more then an order of magnitude. We quantify the role of kicks on black hole merger rates. Our results also apply to black holes ejected by the gravitational slingshot mechanism.

The Milky Way's Supermassive Black Hole: How Good a Case Is It?

NASA Astrophysics Data System (ADS)

Eckart, Andreas; Hüttemann, Andreas; Kiefer, Claus; Britzen, Silke; Zajaček, Michal; Lämmerzahl, Claus; Stöckler, Manfred; Valencia-S, Monica; Karas, Vladimir; García-Marín, Macarena

2017-05-01

The compact and, with {˜ }4.3± 0.3× 10^6 M_{\\odot }, very massive object located at the center of the Milky Way is currently the very best candidate for a supermassive black hole (SMBH) in our immediate vicinity. The strongest evidence for this is provided by measurements of stellar orbits, variable X-ray emission, and strongly variable polarized near-infrared emission from the location of the radio source Sagittarius A* (SgrA*) in the middle of the central stellar cluster. Simultaneous near-infrared and X-ray observations of SgrA* have revealed insights into the emission mechanisms responsible for the powerful near-infrared and X-ray flares from within a few tens to one hundred Schwarzschild radii of such a putative SMBH. If SgrA* is indeed a SMBH it will, in projection onto the sky, have the largest event horizon and will certainly be the first and most important target for very long baseline interferometry observations currently being prepared by the event horizon telescope (EHT). These observations in combination with the infrared interferometry experiment GRAVITY at the very large telescope interferometer and other experiments across the electromagnetic spectrum might yield proof for the presence of a black hole at the center of the Milky Way. The large body of evidence continues to discriminate the identification of SgrA* as a SMBH from alternative possibilities. It is, however, unclear when the ever mounting evidence for SgrA* being associated with a SMBH will suffice as a convincing proof. Additional compelling evidence may come from future gravitational wave observatories. This manuscript reviews the observational facts, theoretical grounds and conceptual aspects for the case of SgrA* being a black hole. We treat theory and observations in the framework of the philosophical discussions about "(anti)realism and underdetermination", as this line of arguments allows us to describe the situation in observational astrophysics with respect to supermassive black holes. Questions concerning the existence of supermassive black holes and in particular SgrA* are discussed using causation as an indispensable element. We show that the results of our investigation are convincingly mapped out by this combination of concepts.

Filling a SMBH accretion disk atmosphere at small and intermediate radii

NASA Astrophysics Data System (ADS)

Karas, Vladimir; Czerny, Bozena; Kunneriath, Devaky

2017-08-01

The medium above an accretion disk is highly diluted and hot. An efficient mechanism to deliver particles and dust grains is an open question; apparently, different processes must be in operation. We discuss an interplay of two different scenarios, where the material is elevated from the plane of an equatorial accretion disk into a corona near a supermassive black hole: (i) an electromagnetically induced transport, which can be driven by magnetic field of stars passing across an accretion disk (Karas et al., 2017); and (ii) radiatively driven acceleration by radiation emerging from the disk (Czerny et al 2015), which can launch a dusty wind near above the dust sublimation radius. The former process can operate in the vicinity of a supermassive black hole (SMBH) surrounded by a dense nuclear star-cluster. The latter process involves the effect of radiation pressure from various sources - stars, accretion disc, and the central accreting SMBH; it can help filling the Broad-Line Region against the vertical component of the black hole gravitational attraction and the accretion disk self-gravity at radius about a few $\\times 10^3 R_g$.

Modeling spatially and spectrally resolved observations to diagnose the formation of elliptical galaxies

NASA Astrophysics Data System (ADS)

Snyder, Gregory Frantz

2013-03-01

In extragalactic astronomy, a central challenge is that we cannot directly watch what happens to galaxies before and after they are observed. This dissertation focuses on linking predictions of galaxy time-evolution directly with observations, evaluating how interactions, mergers, and other processes affect the appearance of elliptical galaxies. The primary approach is to combine hydrodynamical simulations of galaxy formation, including all major components, with dust radiative transfer to predict their observational signatures The current paradigm implies that a quiescent elliptical emerges following a formative starburst event. These trigger accretion onto the central supermassive black hole (SMBH), which then radiates as an active galactic nucleus (AGN). However, it is not clear the extent to which SMBH growth is fueled by these events nor how important is their energy input at setting the appearance of the remnant. This thesis presents results drawing from three phases in the formation of a typical elliptical: 1) I evaluate how to disentangle AGN from star formation signatures in mid-infrared spectra during a dust-enshrouded starburst, making testable predictions for robustly tracing SMBH growth with the James Webb Space Telescope; 2) I develop a model for the rate of merger-induced post-starburst galaxies selected from optical spectra, resolving tension between their observed rarity and merger rates from other estimates; and 3) I present results from Hubble Space Telescope imaging of elliptical galaxies in galaxy clusters at 1 < z < 2, the precursors of present-day massive clusters with M ~ 1015 solar masses, demonstrating that their stars formed over an extended period and ruling out the simplest model for their formation history. These results lend support to a stochastic formation history for ellipticals driven by mergers or interactions. However, significant uncertainties remain in how to evaluate the implications of galaxy appearance, in particular their morphologies across cosmic time. In the final chapter, I outline an approach to build a "mock observatory" from cosmological hydrodynamical simulations, with which observations of all types, including at high spatial and spectral resolutions, can be brought to bear in directly constraining the physics of galaxy formation and evolution.

The nature of massive transition galaxies in CANDELS, GAMA and cosmological simulations

NASA Astrophysics Data System (ADS)

Pandya, Viraj; Brennan, Ryan; Somerville, Rachel S.; Choi, Ena; Barro, Guillermo; Wuyts, Stijn; Taylor, Edward N.; Behroozi, Peter; Kirkpatrick, Allison; Faber, Sandra M.; Primack, Joel; Koo, David C.; McIntosh, Daniel H.; Kocevski, Dale; Bell, Eric F.; Dekel, Avishai; Fang, Jerome J.; Ferguson, Henry C.; Grogin, Norman; Koekemoer, Anton M.; Lu, Yu; Mantha, Kameswara; Mobasher, Bahram; Newman, Jeffrey; Pacifici, Camilla; Papovich, Casey; van der Wel, Arjen; Yesuf, Hassen M.

2017-12-01

We explore observational and theoretical constraints on how galaxies might transition between the 'star-forming main sequence' (SFMS) and varying 'degrees of quiescence' out to z = 3. Our analysis is focused on galaxies with stellar mass M* > 1010 M⊙, and is enabled by GAMA and CANDELS observations, a semi-analytic model (SAM) of galaxy formation, and a cosmological hydrodynamical 'zoom in' simulation with momentum-driven AGN feedback. In both the observations and the SAM, transition galaxies tend to have intermediate Sérsic indices, half-light radii, and surface stellar mass densities compared to star-forming and quiescent galaxies out to z = 3. We place an observational upper limit on the average population transition time-scale as a function of redshift, finding that the average high-redshift galaxy is on a 'fast track' for quenching whereas the average low-redshift galaxy is on a 'slow track' for quenching. We qualitatively identify four physical origin scenarios for transition galaxies in the SAM: oscillations on the SFMS, slow quenching, fast quenching, and rejuvenation. Quenching time-scales in both the SAM and the hydrodynamical simulation are not fast enough to reproduce the quiescent population that we observe at z ∼ 3. In the SAM, we do not find a clear-cut morphological dependence of quenching time-scales, but we do predict that the mean stellar ages, cold gas fractions, SMBH (supermassive black hole) masses and halo masses of transition galaxies tend to be intermediate relative to those of star-forming and quiescent galaxies at z < 3.

Gravitational interactions of stars with supermassive black hole binaries. I. Tidal disruption events

NASA Astrophysics Data System (ADS)

Darbha, Siva; Coughlin, Eric R.; Kasen, Daniel; Quataert, Eliot

2018-04-01

Stars approaching supermassive black holes (SMBHs) in the centers of galaxies can be torn apart by strong tidal forces. We study the physics of tidal disruption by a circular, binary SMBH as a function of the binary mass ratio q = M2/M1 and separation a, exploring a large set of points in the parameter range q ∈ [0.01, 1] and a/rt1 ∈ [10, 1000]. We simulate encounters in which field stars approach the binary from the loss cone on parabolic, low angular momentum orbits. We present the rate of disruption and the orbital properties of the disrupted stars, and examine the fallback dynamics of the post-disruption debris in the "frozen-in" approximation. We conclude by calculating the time-dependent disruption rate over the lifetime of the binary. Throughout, we use a primary mass M1 = 106M⊙ as our central example. We find that the tidal disruption rate is a factor of ˜2 - 7 times larger than the rate for an isolated BH, and is independent of q for q ≳ 0.2. In the "frozen-in" model, disruptions from close, nearly equal mass binaries can produce intense tidal fallbacks: for binaries with q ≳ 0.2 and a/rt1 ˜ 100, roughly ˜18 - 40% of disruptions will have short rise times (trise ˜ 1 - 10 d) and highly super-Eddington peak return rates (\\dot{M}_{peak} / \\dot{M}_{Edd} ˜ 2 × 10^2 - 3 × 10^3).

Gravitational interactions of stars with supermassive black hole binaries - I. Tidal disruption events

NASA Astrophysics Data System (ADS)

Darbha, Siva; Coughlin, Eric R.; Kasen, Daniel; Quataert, Eliot

2018-07-01

Stars approaching supermassive black holes (SMBHs) in the centres of galaxies can be torn apart by strong tidal forces. We study the physics of tidal disruption by a circular, binary SMBH as a function of the binary mass ratio q = M2/M1 and separation a, exploring a large set of points in the parameter range q ∈ [0.01, 1] and a/rt1 ∈ [10, 1000]. We simulate encounters in which field stars approach the binary from the loss cone on parabolic, low angular momentum orbits. We present the rate of disruption and the orbital properties of the disrupted stars, and examine the fallback dynamics of the post-disruption debris in the `frozen-in' approximation. We conclude by calculating the time-dependent disruption rate over the lifetime of the binary. Throughout, we use a primary mass M1 = 106 M⊙ as our central example. We find that the tidal disruption rate is a factor of ˜2-7 times larger than the rate for an isolated BH, and is independent of q for q ≳ 0.2. In the `frozen-in' model, disruptions from close, nearly equal mass binaries can produce intense tidal fallbacks: for binaries with q ≳ 0.2 and a/rt1 ˜ 100, roughly {˜ } 18-40 per cent of disruptions will have short rise times (trise ˜ 1-10 d) and highly super-Eddington peak return rates (\\dot{M}_peak / \\dot{M}_Edd ˜ 2 × 10^2-3 × 10^3).

Co-evolution of Massive Black Holes and Their Host Galaxies

NASA Astrophysics Data System (ADS)

Chen, Y. M.

2010-07-01

A scenario of co-evolution of supermassive black holes (SMBHs) and galaxies has been clearly conducted by the important evidence from observational results of quasar host galaxies and the relation between spheroid and SMBH mass. There are a plenty of unresolved problems and questions, some being basic, to be addressed in this scenario. The main goal of the present thesis is focusing on the mysterious scenario including growth of primordial black holes, cosmological evolution of spins and duty cycle of SMBHs, and interaction between the SMBH activity and star formation in galaxies from low to high redshifts. We review the main progress of this field over the past decade since the discovery of Magorrian relation and present comments on some questions in light of our view of points. The key questions to be addressed in this thesis work are: (1) how does the fast growth of primordial black holes influence their evolution? (2) what is the equation to describe the co-evolution of SMBHs and galaxies? (3) what is the mechanism to control the co-evolution? (4) how to transport the fueling gas from kpc scale to the center? It has been suggested that fast growth of primordial black holes via super-Eddington accretion is a promising way to form SMBHs in high redshift universe. Neutrino cooling has been employed and expedites the growth. We consider the Compton heating of the surroundings of the primordial black holes. We find that the realistic accretion rate is only a few percent of the Eddington rate, and the accretion is episodic. It implies that the fast growth via super-Eddington is not feasible. These conclusions have been confirmed by the detailed numerical simulations of Milosavljevic et al. (2008). The difficulties of the fast growth via accretion of baryon particles make the formation of SMBHs elusive in high redshift universe. We developed a new formulation to calculate the duty cycle of SMBHs based on the Soltan argument. We show it can be expressed by the mass density ratio of active SMBHs to the total. This not only makes the calculation of the duty cycle independent of the assumption of cosmological evolution of Eddington ratios, but also allows us to set a totally new equation - the so-called η-equation to describe the co-evolution of SMBHs and galaxies. Applying the equations to SDSS (Sloan Digital Sky Survey) and other related survey data, we find that: (1) cosmological evolution of the duty cycle tightly follows the history of star formation rate (SFR) density in z<2 universe; (2) they just show opposite trends in higher redshift universe; (3) the radiative efficiency dramatically decreases with z, showing η≈0.3 at z =2 and down to η≈0.05 at z =0. It shows for the first time a history of random accretion of SMBH growth from high to low redshift universe. Chapter 3 is devoted to develop a new method to estimate the specific star formation rates (SSFR) for DEEP2 data. Using the series of Balmer absorption lines in rest-frame 3750~4150 Å, we develop a new method to estimate the SSFR. Applying this new method to both SDSS and DEEP2 data, we find the SSFR derived from Balmer absorption lines is consistent with that from emission lines at local universe, while there is a 100.3~100.4 discrepancy at z&≈1. This result implies the initial mass function changes with redshift, and it tends to form more massive stars at higher redshift. We pay much attention to the interaction between AGN and star formation in Chapter 4 through investigations of the Seyfert galaxies and type II AGNs. We obtain the SFR in about 50 Seyfert galaxies and compare with the SFR predicted by Kennicutt-Schmidt's law. We find that they are lower than the predicted by a factor of 10~100, clearly showing the evidence of suppressing the star formation in the 100 pc region around nuclei. 10848 type II AGNs are selected from SDSS data for the study of starburst and AGN connection. We find the young stars are playing an important role in triggering SMBH activities. A very tight correlation Λ≅SSFR1.5 between the Eddington ratio λ and SSFR has been found in the sample. This nonlinear relation stresses the role of supernova explosion, which could excite strong turbulent viscosity to transport the angular momentum of the fueling gas to the SMBHs. We set up a modified model by including the role of supernova explosion to account for the starburst-AGN connection. Indeed, we find that the model can be nicely consistent with the correlation. In this thesis, we demonstrate a self-adjusted system of galaxies and SMBHs - the SMBHs are triggered via star formation, which would get suppressed by SMBH activities. As a summary of the present thesis, we draw a conclusion that we poorly understand the issues as to formation of SMBHs, evolution of galaxies and SMBHs. There are a plenty of issues to be addressed in future. The solved questions are much less than the bringing out ones.

THE BRIGHTEST CLUSTER GALAXY IN A85: THE LARGEST CORE KNOWN SO FAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

López-Cruz, O.; Añorve, C.; Ibarra-Medel, H. J.

2014-11-10

We have found that the brightest cluster galaxy (BCG) in A85, Holm 15A, displays the largest core known so far. Its cusp radius, r {sub γ} = 4.57 ± 0.06 kpc (4.''26 ± 0.''06), is more than 18 times larger than the mean for BCGs and ≳ 1 kpc larger than A2261-BCG, hitherto the largest-cored BCG. Holm 15A hosts the luminous amorphous radio source 0039-095B and has the optical signature of a LINER. Scaling laws indicate that this core could host a supermassive black hole (SMBH) of mass M {sub •} ∼ (10{sup 9}-10{sup 11}) M {sub ☉}. We suggestmore » that cores this large represent a relatively short phase in the evolution of BCGs, whereas the masses of their associated SBMH might be set by initial conditions.« less

A 200-second quasi-periodicity after the tidal disruption of a star by a dormant black hole.

PubMed

Reis, R C; Miller, J M; Reynolds, M T; Gültekin, K; Maitra, D; King, A L; Strohmayer, T E

2012-08-24

Supermassive black holes (SMBHs; mass is greater than or approximately 10(5) times that of the Sun) are known to exist at the center of most galaxies with sufficient stellar mass. In the local universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, which often comes in the form of long-term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a ~200-second x-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local universe.

Chandra and VLA Observations of Supermassive Black Hole Outbursts in M87

NASA Astrophysics Data System (ADS)

Forman, William; Jones, C.; Churazov, Eugene

2013-07-01

We discuss the effects of supermassive black hole (SMBH) outbursts on the hot atmospheres surrounding the central massive galaxies in groups and clusters, as observed with X-ray and radio observations. We focus on a detailed study of the supermassive black hole in M87 at the center of the Virgo cluster using Chandra and VLA observations. We summarize the outburst history and describe the clearly observed energy input from buoyant bubbles of relativistic plasma produced by the central SMBH, uplifted filaments of X-ray emitting gas, and the Mach 1.2 shock together balance the energy lost as gas radiatively cools.

Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Pei-Ying; Koch, Patrick M.; Ho, Paul T. P.

The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS( J = 2 − 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward themore » nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.« less

Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

NASA Astrophysics Data System (ADS)

Hsieh, Pei-Ying; Koch, Patrick M.; Ho, Paul T. P.; Kim, Woong-Tae; Tang, Ya-Wen; Wang, Hsiang-Hsu; Yen, Hsi-Wei; Hwang, Chorng-Yuan

2017-09-01

The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS(J = 2 - 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.

Triggering and Quenching: simulations and mock observations of Active Galactic Nuclei and their hosts

NASA Astrophysics Data System (ADS)

Choi, Ena

2015-10-01

The lives of galaxies and their supermassive black holes (SMBH) are probably intimately linked. Deep multi-wavelength surveys with HST are now providing detailed imaging of a statistically robust sample of obscured and unobscured AGN hosts, along with control samples of inactive galaxies, giving us an unprecedented opportunity to study the relationship between AGN and their hosts. However, so far these observations have uncovered more puzzles than they have resolved. Although mergers are considered a promising triggering mechanism for AGN activity, numerous studies have shown that AGN hosts are no more likely to appear morphologically disturbed than inactive galaxies. Studies of whether AGN hosts exhibit enhanced or suppressed star formation have also yielded conflicting results. We propose to run a suite of state-of-the-art simulations to study the AGN-host galaxy connection. These simulations will be post-processed with a radiative transfer code, a sub-grid model for torus-scale obscuration, and short timescale AGN variability. Using mock images created from the simulations, we will study the predicted morphologies and stellar populations of AGN hosts and normal galaxies with similar stellar masses. We will use our simulations to address two major science questions: (1) how is SMBH growth fueled and fed, and what triggers rapid feeding, and (2) how does AGN feedback regulate BH growth and the growth of the host galaxy? In addition, we will release our simulation outputs and mock images and catalogs to the community through MAST.

Fast-growing SMBHs in Fast-growing Galaxies, at High Redshifts: the Role of Major Mergers as Revealed by ALMA

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Lira, Paulina; Netzer, Hagai; Cicone, Claudia; Maiolino, Roberto; Shemmer, Ohad

2017-11-01

We present a long-term, multi-wavelength project to understand the epoch of fastest growth of the most massive black holes by using a sample of 40 luminous quasars at z 4.8. These quasars have rather uniform properties, with typical accretion rates and black hole masses of L/L_Edd 0.7 and M_BH 10^9 M_sun. The sample consists of ``FIR-bright'' sources with a previous Herschel/SPIRE detection, suggesting SFR>1000 M_sun/yr, as well as of ``FIR-faint'' sources for which Herschel stacking analysis implies a typical SFR of 400 M_sun/yr. Six of the quasars have been observed by ALMA in [C II] 157.74 micron line emission and adjacent rest-frame 150 □micron continuum, to study the dusty cold ISM. ALMA detected companion, spectroscopically confirmed sub-mm galaxies (SMGs) for three sources – one FIR-bright and two FIR-faint. The companions are separated by 14-45 kpc from the quasar hosts, and we interpret them as major galaxy interactions. Our ALMA data therefore clearly support the idea that major mergers may be important drivers for rapid, early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs, and their ordered gas kinematics observed by ALMA, suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth.

Do some AGN lack X-ray emission?

NASA Astrophysics Data System (ADS)

Simmonds, C.; Bauer, F. E.; Thuan, T. X.; Izotov, Y. I.; Stern, D.; Harrison, F. A.

2016-12-01

Context. Intermediate-mass black holes (IMBHs) are thought to be the seeds of early supermassive black holes (SMBHs). While ≳100 IMBH and small SMBH candidates have been identified in recent years, few have been robustly confirmed to date, leaving their number density in considerable doubt. Placing firmer constraints both on the methods used to identify and confirm IMBHs/SMBHs, as well as characterizing the range of host environments that IMBHs/SMBHs likely inhabit is therefore of considerable interest and importance. Additionally, finding significant numbers of IMBHs in metal-poor systems would be particularly intriguing, since such systems may represent local analogs of primordial galaxies, and therefore could provide clues of early accretion processes. Aims: Here we study in detail several candidate active galactic nuclei (AGN) found in metal-poor hosts. Methods: We utilize new X-ray and optical observations to characterize these metal-poor AGN candidates and compare them against known AGN luminosity relations and well-characterized IMBH/SMBH samples. Results: Despite having clear broad optical emission lines that are long-lived (≳10-13 yr), these candidate AGN appear to lack associated strong X-ray and hard UV emission, lying at least 1-2 dex off the known AGN correlations. If they are IMBHs/SMBHs, our constraints imply that they either are not actively accreting, their accretion disks are fully obscured along our line-of-sight, or their accretion disks are not producing characteristic high energy emission. Alternatively, if they are not AGN, then their luminous broad emission lines imply production by extreme stellar processes. The latter would have profound implications on the applicability of broad lines for mass estimates of massive black holes. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/596/A64

DISK ASSEMBLY AND THE M {sub BH}-{sigma} {sub e} RELATION OF SUPERMASSIVE BLACK HOLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Debattista, Victor P.; Kazantzidis, Stelios; Van den Bosch, Frank C., E-mail: vpdebattista@gmail.com, E-mail: stelios@mps.ohio-state.edu, E-mail: frank.vandenbosch@yale.edu

2013-03-01

Recent Hubble Space Telescope observations have revealed that a majority of active galactic nuclei (AGNs) at z {approx} 1-3 are resident in isolated disk galaxies, contrary to the usual expectation that AGNs are triggered by mergers. Here we develop a new test of the cosmic evolution of supermassive black holes (SMBHs) in disk galaxies by considering the local population of SMBHs. We show that substantial SMBH growth in spiral galaxies is required as disks assemble. SMBHs exhibit a tight relation between their mass and the velocity dispersion of the spheroid within which they reside, the M {sub .}-{sigma} {sub e}more » relation. In disk galaxies the bulge is the spheroid of interest. We explore the evolution of the M {sub .}-{sigma} {sub e} relation when bulges form together with SMBHs on the M {sub .}-{sigma} {sub e} relation and then slowly re-form a disk around them. The formation of the disk compresses the bulge, raising its {sigma} {sub e}. We present evidence for such compression in the form of larger velocity dispersion of classical bulges compared with elliptical galaxies at the same mass. This compression leads to an offset in the M {sub .}-{sigma} {sub e} relation if it is not accompanied by an increased M {sub .}. We quantify the expected offset based on photometric data and show that, on average, SMBHs must grow by {approx}50%-65% just to remain on the M {sub .}-{sigma} {sub e} relation. We find no significant offset in the M {sub .}-{sigma} {sub e} relations of classical bulges and of ellipticals, implying that SMBHs have been growing along with disks. Our simulations demonstrate that SMBH growth is necessary for the local population of disk galaxies to have remained on the M {sub .}-{sigma} {sub e} relation.« less

Very high energy observations of the Galactic Centre: recent results and perspectives with CTA

NASA Astrophysics Data System (ADS)

Terrier, Regis

2016-07-01

The central 300 pc of our Galaxy are a major laboratory for high energy astrophysics. They harbor the closest supermassive black hole (SMBH) and are the site of a sustained star formation activity. The energy released by the supernovae on the ambient medium must be very strong. Similarly, albeit extremely faint nowadays, the SMBH must have experienced episodes of intense activity in the past which can influence significantly the central regions and beyond, e.g. powering the Fermi bubbles. I review observational results at very high energies from the central region and discuss their implications and the questions they leave open. I discuss the perspectives CTA offers for Galactic Centre astrophysics.

Variability Selected Low-Luminosity Active Galactic Nuclei in the 4 Ms Chandra Deep Field-South

NASA Technical Reports Server (NTRS)

Young, M.; Brandt, W. N.; Xue, Y. Q.; Paolillo, D. M.; Alexander, F. E.; Bauer, F. E.; Lehmer, B. D.; Luo, B.; Shemmer, O.; Schneider, D. P.;

Chasing the observational signatures of seed black holes at z > 7: candidate statistics

NASA Astrophysics Data System (ADS)

Valiante, Rosa; Schneider, Raffaella; Graziani, Luca; Zappacosta, Luca

2018-03-01

Supermassive black holes (SMBHs) of 109-1010 M⊙ were already in place ˜13 Gyr ago, at z > 6. Super-Eddington growth of low-mass BH seeds (˜100 M⊙) or less extreme accretion on to˜105 M⊙ seeds have been recently considered as the main viable routes to these SMBHs. Here, we study the statistics of these SMBH progenitors at z ˜ 6. The growth of low- and high-mass seeds and their host galaxies are consistently followed using the cosmological data constrained model GAMETE/QSODUST, which reproduces the observed properties of high-z quasars, like SDSS J1148+5251. We show that both seed formation channels can be in action over a similar redshift range 15 < z < 18 and are found in dark matter haloes with comparable mass, ˜5 × 107 M⊙. However, as long as the systems evolve in isolation (i.e. no mergers occur), noticeable differences in their properties emerge: At z ≥ 10 galaxies hosting high-mass seeds have smaller stellar mass and metallicity, the BHs accrete gas at higher rates and star formation proceeds less efficiently than in low-mass seeds hosts. At z < 10 these differences are progressively erased, as the systems experience minor or major mergers and every trace of the BH origin gets lost.

Accreting SMBH in the COSMOS field: the connection to their host galaxies .

NASA Astrophysics Data System (ADS)

Merloni, A.; Bongiorno, A.

Using the rich multi-band photometry in the COSMOS field we explore the host galaxy properties of a large, complete, sample of X-ray and spectroscopically selected AGN. Based on a two-components fit to their Spectral Energy Distribution (SED) we derive rest-frame magnitudes, colours, stellar masses and star formation rates up to z˜ 3. The probability for a galaxy to host a black hole growing at any given specific accretion rate (the ratio of X-ray luminosity to the host stellar mass) is independent of the galaxy mass and follows a power-law distribution in L_X/M. By looking at the normalisation of such a probability distribution, we show how the incidence of AGN increases with redshift as rapidly as (1+z)4.2, in close resemblance with the overall evolution of the specific star formation rate. Although AGN activity and star formation appear to have a common triggering mechanism, we do not find any 'smoking gun' signalling powerful AGN influence on the global properties of their host galaxies.

Supermassive black holes with higher Eddington ratios preferentially form in gas-rich galaxies

NASA Astrophysics Data System (ADS)

Izumi, Takuma

2018-06-01

The Eddington ratio (λEdd) of supermassive black holes (SMBHs) is a fundamental parameter that governs their cosmic growth. Although gas mass accretion onto SMBHs is sustained when they are surrounded by large amounts of gas, little is known about the molecular content of galaxies, particularly those hosting super-Eddington SMBHs (λEdd > 1: the key phase of SMBH growth). Here, we have compiled reported optical and 12CO(1-0) data of local quasars to characterize their hosts. We found that higher-λEdd SMBHs tend to reside in gas-rich (i.e., high gas mass to stellar mass fraction = fgas) galaxies. We used two methods to make this conclusion: one uses black hole mass as a surrogate for stellar mass by assuming a local co-evolutionary relationship, and the other directly uses stellar masses estimated from near-infrared observations. The fgas-λEdd correlation we found concurs with the cosmic decreasing trend in λEdd, as cold molecular gas is primarily consumed by star formation. This correlation qualitatively matches predictions of recent semi-analytic models of the cosmic downsizing of SMBHs as well. As the gas mass surface density would eventually be a key parameter controlling mass accretion, we need high-resolution observations to identify further differences in the molecular properties around super-Eddington and sub-Eddington SMBHs.

Supermassive black holes with higher Eddington ratios preferentially form in gas-rich galaxies

NASA Astrophysics Data System (ADS)

Izumi, Takuma

2018-05-01

The Eddington ratio (λEdd) of supermassive black holes (SMBHs) is a fundamental parameter that governs their cosmic growth. Although gas mass accretion onto SMBHs is sustained when they are surrounded by large amounts of gas, little is known about the molecular content of galaxies, particularly those hosting super-Eddington SMBHs (λEdd > 1: the key phase of SMBH growth). Here, we have compiled reported optical and 12CO(1-0) data of local quasars to characterize their hosts. We found that higher-λEdd SMBHs tend to reside in gas-rich (i.e., high gas mass to stellar mass fraction = fgas) galaxies. We used two methods to make this conclusion: one uses black hole mass as a surrogate for stellar mass by assuming a local co-evolutionary relationship, and the other directly uses stellar masses estimated from near-infrared observations. The fgas-λEdd correlation we found concurs with the cosmic decreasing trend in λEdd, as cold molecular gas is primarily consumed by star formation. This correlation qualitatively matches predictions of recent semi-analytic models of the cosmic downsizing of SMBHs as well. As the gas mass surface density would eventually be a key parameter controlling mass accretion, we need high-resolution observations to identify further differences in the molecular properties around super-Eddington and sub-Eddington SMBHs.

DISCOVERY OF NUCLEAR WATER MASER EMISSION IN CENTAURUS A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ott, Juergen; Meier, David S.; Walter, Fabian

2013-07-10

We report the detection of a 22 GHz water maser line in the nearest (D {approx} 3.8 Mpc) radio galaxy Centaurus A (Cen A) using the Australia Telescope Compact Array (ATCA). The line is centered at a velocity of {approx}960 km s{sup -1}, which is redshifted by about 415 km s{sup -1} from the systemic velocity. Such an offset, as well as the width of {approx}120 km s{sup -1}, could be consistent with either a nuclear maser arising from an accretion disk of the central supermassive black hole (SMBH), or with a jet maser that is emitted from the materialmore » that is shocked near the base of the jet in Cen A. The best spatial resolution of our ATCA data constrains the origin of the maser feature within <3 pc of the SMBH. The maser exhibits an isotropic luminosity of {approx}1 L{sub Sun }, which classifies it as a kilomaser, and appears to be variable on timescales of months. A kilomaser can also be emitted by shocked gas in star-forming regions. Given the small projected distance from the core, the large offset from systemic velocity, and the smoothness of the line feature, we conclude that a jet maser line emitted by shocked gas around the base of the active galactic nucleus is the most likely explanation. For this scenario we can infer a minimum density of the radio jet of {approx}> 10 cm{sup -3}, which indicates substantial mass entrainment of surrounding gas into the propagating jet material.« less

Supernova kicks and dynamics of compact remnants in the Galactic Centre

NASA Astrophysics Data System (ADS)

Bortolas, Elisa; Mapelli, Michela; Spera, Mario

2017-08-01

The Galactic Centre (GC) is a unique place to study the extreme dynamical processes occurring near a supermassive black hole (SMBH). Here, we investigate the role of supernova (SN) explosions occurring in massive binary systems lying in a disc-like structure within the innermost parsec. We use a regularized algorithm to simulate 3 × 104 isolated three-body systems composed of a stellar binary orbiting the SMBH. We start the integration when the primary member undergoes an SN explosion and analyse the impact of SN kicks on the orbits of stars and compact remnants. We find that SN explosions scatter the lighter stars in the pair on completely different orbits, with higher eccentricity and inclination. In contrast, stellar-mass black holes (BHs) and massive stars retain memory of the orbit of their progenitor star. Our results suggest that SN kicks are not sufficient to eject BHs from the GC. We thus predict that all BHs that form in situ in the central parsec of our Galaxy remain in the GC, building up a cluster of dark remnants. In addition, the change of neutron star (NS) orbits induced by SNe may partially account for the observed dearth of NSs in the GC. About 40 per cent of remnants stay bound to the stellar companion after the kick; we expect up to 70 per cent of them might become X-ray binaries through Roche lobe filling. Finally, the eccentricity of some light stars becomes >0.7 as an effect of the SN kick, producing orbits similar to those of the G1 and G2 dusty objects.

A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jia; Halpern, Jules P.; Eracleous, Michael

2016-01-20

One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocitymore » can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.« less

Dynamics of supernova remnants in the Galactic centre.

NASA Astrophysics Data System (ADS)

Bortolas, E.; Mapelli, M.; Spera, M.

The Galactic centre (GC) is a unique place to study the extreme dynamical processes occurring near a super-massive black hole (SMBH). Here we simulate a large set of binaries orbiting the SMBH while the primary member undergoes a supernova (SN) explosion, in order to study the impact of SN kicks on the orbits of stars and dark remnants in the GC. We find that SN explosions are efficient in scattering neutron stars and other light stars on new (mostly eccentric) orbits, while black holes (BHs) tend to retain memory of the orbit of their progenitor star. SN kicks are thus unable to eject BHs from the GC: a cusp of dark remnants may be lurking in the central parsec of our Galaxy.

The Formation of Supermassive Black Holes from Population III.1 Seeds. I. Cosmic Formation Histories and Clustering Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banik, Nilanjan; Tan, Jonathan C.; Monaco, Pierluigi

We calculate the cosmic distributions in space and time of the formation sites of the first, "Pop III.1" stars, exploring a model in which these are the progenitors of all supermassive black holes (SMBHs). Pop III.1 stars are defined to form from primordial composition gas in dark matter minihalos withmore » $$\\sim10^6\\:M_\\odot$$ that are isolated from neighboring astrophysical sources by a given isolation distance, $$d_{\\rm{iso}}$$. We assume Pop III.1 sources are seeds of SMBHs, based on protostellar support by dark matter annihilation heating that allows them to accrete a large fraction of their minihalo gas, i.e., $$\\sim 10^5\\:M_\\odot$$. Exploring $$d_{\\rm{iso}}$$ from 10--$$100\\:\\rm{kpc}$$ (proper distances), we predict the redshift evolution of Pop III.1 source and SMBH remnant number densities. The local, $z=0$ density of SMBHs constrains $$d_{\\rm{iso}}\\lesssim 100\\:\\rm{kpc}$$ (i.e., $$3\\:\\rm{Mpc}$$ comoving distance at $$z\\simeq30$$). In our simulated ($$\\sim60\\:\\rm{Mpc}$$)$^3$ comoving volume, Pop III.1 stars start forming just after $z=40$. Their formation is largely complete by $$z\\simeq25$$ to 20 for $$d_{\\rm{iso}}=100$$ to $$50\\:\\rm{kpc}$$. We follow source evolution to $z=10$, by which point most SMBHs reside in halos with $$\\gtrsim10^8\\:M_\\odot$$. Over this period, there is relatively limited merging of SMBHs for these values of $$d_{\\rm{iso}}$$. We also predict SMBH clustering properties at $z=10$$: feedback suppression of neighboring sources leads to relatively flat angular correlation functions. Finally, we consider a simple "Str\\"omgren" model for $$d_{\\rm iso}$, based on ionizing feedback from zero age main sequence supermassive Pop III.1 stars that may be the direct progenitors of SMBHs in this scenario. Such models naturally produce feedback effects on scales of $$\\sim100\\:$$kpc and thus self-consistently generate a SMBH number density similar to the observed value.« less

A 200-Second Quasi-Periodicity After the Tidal Disruption of a Star by a Dormant Black Hole

NASA Technical Reports Server (NTRS)

Reis, R. C.; Miller, J. M.; Reynolds, M. T.; Gueltkinm K.; Maitra, D.; King, A. L.; Strohmayer, T.

2012-01-01

Supermassive black holes are known to exist at the center of most galaxies with sufficient stellar mass, In the local Universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, often coming in the form of long term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a approx.200-s X-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local Universe.

Keck Observations of the Gas Dynamics at the Galactic Center

NASA Astrophysics Data System (ADS)

Campbell, Randall; Ciurlo, Anna; Morris, Mark; Sitarski, Breann N.; Ghez, Andrea M.; Do, Tuan

2018-06-01

In the central parsec of the Milky Way Galaxy the environment of the super-massive black hole (SMBH) presents a complicated mixture of stars, gas, and dust. These inner few tens of arcseconds of the GC have been observed at high resolution with Keck for 20 years with the primary goal of monitoring stars orbiting the SMBH. However, the gas features and their dynamics can also be closely examined using this unique baseline of data. In particular, observations with the Keck OSIRIS integral field spectrometer allow us to examine of the dynamical properties of the gas and to possibly identify new “G-type” objects, or dusty stellar objects. We present a study of morphology and orbital dynamics of sub-parsec scale gas features in the central region.

Jetted tidal disruptions of stars as a flag of intermediate mass black holes at high redshifts

NASA Astrophysics Data System (ADS)

Fialkov, Anastasia; Loeb, Abraham

2017-11-01

Tidal disruption events (TDEs) of stars by single or binary supermassive black holes (SMBHs) brighten galactic nuclei and reveal a population of otherwise dormant black holes. Adopting event rates from the literature, we aim to establish general trends in the redshift evolution of the TDE number counts and their observable signals. We pay particular attention to (I) jetted TDEs whose luminosity is boosted by relativistic beaming and (II) TDEs around binary black holes. We show that the brightest (jetted) TDEs are expected to be produced by massive black hole binaries if the occupancy of intermediate mass black holes (IMBHs) in low-mass galaxies is high. The same binary population will also provide gravitational wave sources for the evolved Laser Interferometer Space Antenna. In addition, we find that the shape of the X-ray luminosity function of TDEs strongly depends on the occupancy of IMBHs and could be used to constrain scenarios of SMBH formation. Finally, we make predictions for the expected number of TDEs observed by future X-ray telescopes finding that a 50 times more sensitive instrument than the Burst Alert Telescope (BAT) on board the Swift satellite is expected to trigger ˜10 times more events than BAT, while 6-20 TDEs are expected in each deep field observed by a telescope 50 times more sensitive than the Chandra X-ray Observatory if the occupation fraction of IMBHs is high. Because of their long decay times, high-redshift TDEs can be mistaken for fixed point sources in deep field surveys and targeted observations of the same deep field with year-long intervals could reveal TDEs.

Direct Collapse to Supermassive Black Hole Seeds with Radiation Transfer: Cosmological Halos

NASA Astrophysics Data System (ADS)

Ardaneh, Kazem; Luo, Yang; Shlosman, Isaac; Nagamine, Kentaro; Wise, John H.; Begelman, Mitchell C.

2018-06-01

We have modeled direct collapse of a primordial gas within dark matter halos in the presence of radiative transfer, in high-resolution zoom-in simulations in a cosmological framework, down to the formation of the photosphere and the central object. Radiative transfer has been implemented in the flux-limited diffusion (FLD) approximation. Adiabatic models were run for comparison. We find that (a) the FLD flow forms an irregular central structure and does not exhibit fragmentation, contrary to adiabatic flow which forms a thick disk, driving a pair of spiral shocks, subject to Kelvin-Helmholtz shear instability forming fragments; (b) the growing central core in the FLD flow quickly reaches ˜10 M⊙ and a highly variable luminosity of 1038 - 1039 erg s-1, comparable to the Eddington luminosity. It experiences massive recurrent outflows driven by radiation force and thermal pressure gradients, which mix with the accretion flow and transfer the angular momentum outwards; and (c) the interplay between these processes and a massive accretion, results in photosphere at ˜10 AU. We conclude that in the FLD model (1) the central object exhibits dynamically insignificant rotation and slower than adiabatic temperature rise with density; (2) does not experience fragmentation leading to star formation, thus promoting the fast track formation of a supermassive black hole (SMBH) seed; (3) inclusion of radiation force leads to outflows, resulting in the mass accumulation within the central 10-3 pc, which is ˜100 times larger than characteristic scale of star formation. The inclusion of radiative transfer reveals complex early stages of formation and growth of the central structure in the direct collapse scenario of SMBH seed formation.

A simple way to classify supermassive black holes

NASA Astrophysics Data System (ADS)

Feoli, A.

2014-02-01

We propose a classification of supermassive black holes (SMBHs) based on their efficiency in the conversion of infalling mass in emitted radiation. We use a theoretical model that assumes a conservation of angular momentum between the gas falling inside the hole and the photons emitted outwards, and suggests the existence of the scaling relation M-Re \\sigma3, where M is the mass of the central SMBH, whereas Re and \\sigma are the effective radius and velocity dispersion of the host galaxies (bulges), respectively. We apply our model on a data set of 57 galaxies of different morphological types and with M measurements, obtained through the analysis of Spitzer/IRAC 3.6-\\mum images. In order to find the best fit of the corresponding scaling law, we use the FITEXY routine to perform a least-squares regression of M on Re \\sigma3 for the considered sample of galaxies. Our analysis shows that the relation is tight and our theoretical model allows to easily estimate the efficiency of mass conversion into radiation of the central SMBHs. Finally we propose a new appealing way to classify the SMBHs in terms of this parameter.

THE FORMATION OF SUPERMASSIVE BLACK HOLES FROM LOW-MASS POP III SEEDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whalen, Daniel J.; Fryer, Chris L.

2012-09-01

The existence of 10{sup 9} M{sub Sun} black holes (BHs) in massive galaxies by z {approx} 7 is one of the great unsolved mysteries in cosmological structure formation. One theory argues that they originate from the BHs of Pop III stars at z {approx} 20 and then accrete at the Eddington limit down to the epoch of reionization, which requires that they have constant access to rich supplies of fuel. Because early numerical simulations suggested that Pop III stars were {approx}>100 M{sub Sun }, the supermassive black hole (SMBH) seeds considered up to now were 100-300 M{sub Sun }. However,more » there is a growing numerical and observational consensus that some Pop III stars were tens of solar masses, not hundreds, and that 20-40 M{sub Sun} BHs may have been much more plentiful at high redshift. However, we find that natal kicks imparted to 20-40 M{sub Sun} Pop III BHs during formation eject them from their halos and hence their fuel supply, precluding them from Eddington-limit growth. Consequently, SMBHs are far less likely to form from low-mass Pop III stars than from very massive ones.« less

The WISSH quasars project. III. X-ray properties of hyper-luminous quasars

NASA Astrophysics Data System (ADS)

Martocchia, S.; Piconcelli, E.; Zappacosta, L.; Duras, F.; Vietri, G.; Vignali, C.; Bianchi, S.; Bischetti, M.; Bongiorno, A.; Brusa, M.; Lanzuisi, G.; Marconi, A.; Mathur, S.; Miniutti, G.; Nicastro, F.; Bruni, G.; Fiore, F.

2017-12-01

We performed a survey of the X-ray properties of 41 objects from the WISE/SDSS selected hyper-luminous (WISSH) quasars sample, which includes 86 broad-line quasars with bolometric luminosity LBol ≳ 2 × 1047 erg s-1 shining at z 2-4. We used both proprietary and archival Chandra and XMM-Newton observations. Twenty-one quasars have sufficient quality data to perform a spectroscopic analysis, while for the remaining sources, X-ray properties are derived through hardness-ratio analysis (apart for six sources that result to be undetected). The bulk ( 70%) of the detected WISSH quasars exhibit NH <5 × 1022 cm-2, in agreement with their optical Type 1 AGN classification. All but three quasars show unabsorbed 2-10 keV luminosities L2-10≥ 1045 erg s-1. Thanks to their extreme radiative output across the mid-IR-to-X-ray range, WISSH quasars therefore offer the opportunity to significantly extend and validate the existing relations involving L2-10. Specifically, we studied the X-ray luminosity as a function of (i) X-ray-to-optical (X/O) flux ratio; (ii) mid-IR luminosity (LMIR); (iii) LBol, and (iv) αOX versus 2500 Å luminosity. We find that the WISSH quasars show (i) unreported very low X/O ( <0.1) compared to typical AGN values; (ii) L2-10/LMIR ratios that are significantly smaller than those derived for AGN with lower luminosity; (iii) a large X-ray bolometric correction, kBol,X ≈ 100-1000; and (iv) steep -2≳αOX≳-1.7. These results lead to a scenario in which the X-ray emission of hyper-luminous quasars is relatively weaker compared to lower luminosity AGN. Models predict that such an X-ray weakness can be relevant for the acceleration of powerful high-ionization, emission-line-driven winds, which are commonly detected in the UV spectra of WISSH quasars and can, in turn, perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous quasars represent the ideal laboratory to study the link between the AGN energy output and wind acceleration. Additionally, WISSH quasars exhibit very large SMBH masses (log [MBH/M⊙]≳ 9.5). This enables a more robust modeling of the Γ-MBH relation by increasing the statistics at high masses. We derive a flatter Γ dependence than previously found over the broad range 5 ≲log (MBH/M⊙)≲ 11. Finally, we estimate that only 300 ks observations of X-IFU on board Athena will offer a detailed view of the properties of absorption features associated with powerful X-ray SMBH winds for a representative sample of WISSH quasars.

New Constraints for X-ray Reprocessing Around Supermassive Black Holes: Near and Far with State-of-the-Art Multi-Mission Modeling

NASA Astrophysics Data System (ADS)

Tzanavaris, Panayiotis

Fluorescent Fe K emission from neutral matter in AGN spectracan arise in the accretion disk around the centralsupermassive black hole [SMBH] ("broad" line) and/or in distant matter ("narrow"line). If it is broad, it provides a unique windowto the strong gravity SMBH regime, including information on SMBH spin;if it is narrow, it probesthe distant reprocessor, likely a clumpy torus. We will use broadband X-ray data from four NASA X-ray missionsfor 45 nearby AGNs, and 1. Assess whether any known "broad" relativistic lines can be modeledas "narrow"instead, by means of self-consistent modeling of fluorescence,direct, and scattered continua; 2. Measure absorbing column densities both in and out of the line of sight; 3. Bootstrap measures of intrinsic bolometric AGN luminosity, with X-ray and optical data. This work will provide updated results on a) black hole spin, with implications on AGN jet power and accretion history; b) the census of highly-obscured (Compton thick) vs. Compton thin AGNs, with implications on models of the Cosmic X-ray Background; c) calibrations of Fe K line, X-ray intrinsic continuum, [OIII] and [OIV] luminosities as measures of intrinsc bolometric AGN luminosity, with implications on AGN feedback and galaxy evolution. Key in our approach is a physically based, self-consistent modeling of the narrow line, with finite column density in and out of the line of sight, and the latest relativistic modeling of the broad line.

Modeling Supermassive Black Holes in Cosmological Simulations

NASA Astrophysics Data System (ADS)

Tremmel, Michael

My thesis work has focused on improving the implementation of supermassive black hole (SMBH) physics in cosmological hydrodynamic simulations. SMBHs are ubiquitous in mas- sive galaxies, as well as bulge-less galaxies and dwarfs, and are thought to be a critical component to massive galaxy evolution. Still, much is unknown about how SMBHs form, grow, and affect their host galaxies. Cosmological simulations are an invaluable tool for un- derstanding the formation of galaxies, self-consistently tracking their evolution with realistic merger and gas accretion histories. SMBHs are often modeled in these simulations (generally as a necessity to produce realistic massive galaxies), but their implementations are commonly simplified in ways that can limit what can be learned. Current and future observations are opening new windows into the lifecycle of SMBHs and their host galaxies, but require more detailed, physically motivated simulations. Within the novel framework I have developed, SMBHs 1) are seeded at early times without a priori assumptions of galaxy occupation, 2) grow in a way that accounts for the angular momentum of gas, and 3) experience realistic orbital evolution. I show how this model, properly tuned with a novel parameter optimiza- tion technique, results in realistic galaxies and SMBHs. Utilizing the unique ability of these simulations to capture the dynamical evolution of SMBHs, I present the first self-consistent prediction for the formation timescales of close SMBH pairs, precursors to SMBH binaries and merger events potentially detected by future gravitational wave experiments.

Active Galactic Nuclei in Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Hein, Megan; Secrest, N.; Satyapal, S.

2014-01-01

Supermassive black holes (SMBHs) one million to a few billion times the mass of our sun are thought to reside in the center of most, if not all, bulge-dominated galaxies. It has been observed that the mass of these SMBHs is strongly correlated with the mass of these bulges, leading to the popular view that these central black holes are formed by galaxy mergers, which induce the growth of the galaxy's bulge and provide matter with which to feed the black hole. Although these properties and their possible consequences have been studied extensively in high mass galaxies and galaxies with large bulges, there is very little research on the possible existence and subsequent properties of SMBHs in low mass galaxies or galaxies with small or no central bulges. This is a significant weakness in the research of these objects as the study of this population of galaxies would allow us to gain valuable insight into SMBH seeds, black holes thought to have formed in the early universe. Strong X-rays are a good indicator of an accreting black hole, because they require more energy to produce and SMBHs are highly energetic, as well as being easier to see due to their ability to penetrate matter more easily than other forms of radiation. In this poster, I will present the results from an X-ray investigation using data matched from the Chandra X-ray observatory to a sample of low mass galaxies (with a mass of log(M) < 9).

Rapid formation of supermassive black hole binaries in galaxy mergers with gas.

PubMed

Mayer, L; Kazantzidis, S; Madau, P; Colpi, M; Quinn, T; Wadsley, J

2007-06-29

Supermassive black holes (SMBHs) are a ubiquitous component of the nuclei of galaxies. It is normally assumed that after the merger of two massive galaxies, a SMBH binary will form, shrink because of stellar or gas dynamical processes, and ultimately coalesce by emitting a burst of gravitational waves. However, so far it has not been possible to show how two SMBHs bind during a galaxy merger with gas because of the difficulty of modeling a wide range of spatial scales. Here we report hydrodynamical simulations that track the formation of a SMBH binary down to scales of a few light years after the collision between two spiral galaxies. A massive, turbulent, nuclear gaseous disk arises as a result of the galaxy merger. The black holes form an eccentric binary in the disk in less than 1 million years as a result of the gravitational drag from the gas rather than from the stars.

Relaxation near Supermassive Black Holes Driven by Nuclear Spiral Arms: Anisotropic Hypervelocity Stars, S-stars, and Tidal Disruption Events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamers, Adrian S.; Perets, Hagai B., E-mail: hamers@ias.edu

Nuclear spiral arms are small-scale transient spiral structures found in the centers of galaxies. Similarly to their galactic-scale counterparts, nuclear spiral arms can perturb the orbits of stars. In the case of the Galactic center (GC), these perturbations can affect the orbits of stars and binaries in a region extending to several hundred parsecs around the supermassive black hole (SMBH), causing diffusion in orbital energy and angular momentum. This diffusion process can drive stars and binaries to close approaches with the SMBH, disrupting single stars in tidal disruption events (TDEs), or disrupting binaries, leaving a star tightly bound to themore » SMBH and an unbound star escaping the galaxy, i.e., a hypervelocity star (HVS). Here, we consider diffusion by nuclear spiral arms in galactic nuclei, specifically the Milky Way GC. We determine nuclear-spiral-arm-driven diffusion rates using test-particle integrations and compute disruption rates. Our TDE rates are up to 20% higher compared to relaxation by single stars. For binaries, the enhancement is up to a factor of ∼100, and our rates are comparable to the observed numbers of HVSs and S-stars. Our scenario is complementary to relaxation driven by massive perturbers. In addition, our rates depend on the inclination of the binary with respect to the Galactic plane. Therefore, our scenario provides a novel potential source for the observed anisotropic distribution of HVSs. Nuclear spiral arms may also be important for accelerating the coalescence of binary SMBHs and for supplying nuclear star clusters with stars and gas.« less

Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Context

DOE Office of Scientific and Technical Information (OSTI.GOV)

Levine, Robyn Deborah

2008-01-01

Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmologicalmore » scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Lyα forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely into stars. The fueling appears to be a stochastic process, with no preferred timescale for accretion over the duration of the simulation.« less

An outflow in the Seyfert ESO 362-G18 revealed by Gemini-GMOS/IFU observations

NASA Astrophysics Data System (ADS)

Humire, Pedro K.; Nagar, Neil M.; Finlez, Carolina; Firpo, Verónica; Slater, Roy; Lena, Davide; Soto-Pinto, Pamela; Muñoz-Vergara, Dania; Riffel, Rogemar A.; Schmitt, Henrique R.; Kraemer, Steven B.; Schnorr-Müller, Allan; Fischer, Travis C.; Robinson, Andrew; Storchi-Bergmann, Thaisa; Crenshaw, Mike; Elvis, Martin S.

2018-06-01

We present two-dimensional stellar and gaseous kinematics of the inner 0.7 × 1.2 kpc2 of the Seyfert 1.5 galaxy ESO 362-G18, derived from optical (4092-7338 Å) spectra obtained with the GMOS integral field spectrograph on the Gemini South telescope at a spatial resolution of ≈170 pc and spectral resolution of 36 km s-1. ESO 362-G18 is a strongly perturbed galaxy of morphological type Sa or S0/a, with a minor merger approaching along the NE direction. Previous studies have shown that the [O III] emission shows a fan-shaped extension of ≈10'' to the SE. We detect the [O III] doublet, [N II] and Hα emission lines throughout our field of view. The stellar kinematics is dominated by circular motions in the galaxy plane, with a kinematic position angle of ≈137° and is centred approximately on the continuum peak. The gas kinematics is also dominated by rotation, with kinematic position angles ranging from 122° to 139°, projected velocity amplitudes of the order of 100 km s-1, and a mean velocity dispersion of 100 km s-1. A double-Gaussian fit to the [O III]λ5007 and Hα lines, which have the highest signal to noise ratios of the emission lines, reveal two kinematic components: (1) a component at lower radial velocities which we interpret as gas rotating in the galactic disk; and (2) a component with line of sight velocities 100-250 km s-1 higher than the systemic velocity, interpreted as originating in the outflowing gas within the AGN ionization cone. We estimate a mass outflow rate of 7.4 × 10-2 M⊙ yr-1 in the SE ionization cone (this rate doubles if we assume a biconical configuration), and a mass accretion rate on the supermassive black hole (SMBH) of 2.2 × 10-2 M⊙ yr-1. The total ionized gas mass within 84 pc of the nucleus is 3.3 × 105 M⊙; infall velocities of 34 km s-1 in this gas would be required to feed both the outflow and SMBH accretion. The reduced datacube (FITS file) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A94

Quantifying Feedback from Narrow Line Region Outflows in Nearby Active Galaxies. I. Spatially Resolved Mass Outflow Rates for the Seyfert 2 Galaxy Markarian 573

NASA Astrophysics Data System (ADS)

Revalski, M.; Crenshaw, D. M.; Kraemer, S. B.; Fischer, T. C.; Schmitt, H. R.; Machuca, C.

2018-03-01

We present the first spatially resolved mass outflow rate measurements ({\\dot{M}}out}) of the optical emission line gas in the narrow line region (NLR) of a Seyfert 2 galaxy, Markarian 573. Using long slit spectra and [O III] imaging from the Hubble Space Telescope and Apache Point Observatory in conjunction with emission line diagnostics and Cloudy photoionization models, we find a peak outflow rate of {\\dot{M}}out}≈ 3.4 +/- 0.5 {M}ȯ {yr}}-1 at a distance of 210 pc from the central supermassive black hole (SMBH). The outflow extends to distances of 600 pc from the nucleus with a total mass and kinetic energy of M ≈ 2.2 × 106 M ⊙ and E ≈ 5.1 × 1054 erg, revealing the outflows to be more energetic than those in the lower luminosity Seyfert 1 galaxy NGC 4151. The peak outflow rate is an order of magnitude larger than the mass accretion and nuclear outflow rates, indicating local in situ acceleration of the circumnuclear NLR gas. We compare these results to global techniques that quantify an average outflow rate across the NLR, and find the latter are subject to larger uncertainties. These results indicate that spatially resolved observations are critical for probing AGN feedback on scales where circumnuclear star formation occurs.

Secular Black Hole Growth and Feedback in Merger-Free Galaxies

NASA Astrophysics Data System (ADS)

Simmons, Brooke

2016-10-01

We will measure the merger-free galaxy-black hole mass relation for the first time, using a unique, newly-discovered sample of luminous active galactic nuclei (AGN) hosted in galaxies that have not grown via mergers. Our preliminary study has shown that supermassive black holes (SMBHs) in bulgeless galaxies - i.e., galaxies that have never undergone a significant merger - can have substantial growth: bulges are not required for the formation and growth of SMBHs. The proposed targets are broad-line AGN with black hole masses spanning a wide mass range (1e6 to >1e9 M_Sun) and hosted in strongly disk dominated galaxies (>80% light from a disk). This sample is an ideal laboratory for understanding merger-free black hole growth and its feedback on the host galaxy. HST imaging will allow us to disentangle bright nuclear emission from host galaxy, measure bulge type and strength, and identify bulgeless galaxies that have evolved under purely secular conditions. In addition, we will determine whether merger-free galaxies lie on the same SMBH-galaxy relation as galaxies with substantial past mergers, or whether merger-free growth results in a separate relation. The answer to this question has profound consequences for the role of baryon dynamics in driving black hole-galaxy co-evolution.

A Slowly Precessing Disk in the Nucleus of M31 as the Feeding Mechanism for a Central Starburst

NASA Astrophysics Data System (ADS)

Lockhart, K. E.; Lu, J. R.; Peiris, H. V.; Rich, R. M.; Bouchez, A.; Ghez, A. M.

2018-02-01

We present a kinematic study of the nuclear stellar disk in M31 at infrared wavelengths using high spatial resolution integral field spectroscopy. The spatial resolution achieved, FWHM = 0.″12 (0.45 pc at the distance of M31), has only previously been equaled in spectroscopic studies by space-based long-slit observations. Using adaptive-optics-corrected integral field spectroscopy from the OSIRIS instrument at the W. M. Keck Observatory, we map the line-of-sight kinematics over the entire old stellar eccentric disk orbiting the supermassive black hole (SMBH) at a distance of r < 4 pc. The peak velocity dispersion is 381 ± 55 km s‑1, offset by 0.″13 ± 0.″03 from the SMBH, consistent with previous high-resolution long-slit observations. There is a lack of near-infrared (NIR) emission at the position of the SMBH and young nuclear cluster, suggesting a spatial separation between the young and old stellar populations within the nucleus. We compare the observed kinematics with dynamical models from Peiris & Tremaine. The best-fit disk orientation to the NIR flux is [θ l , θ i , θ a ] = [‑33° ± 4°, 44° ± 2°, ‑15° ± 15°], which is tilted with respect to both the larger-scale galactic disk and the best-fit orientation derived from optical observations. The precession rate of the old disk is Ω P = 0.0 ± 3.9 km s‑1 pc‑1, lower than the majority of previous observations. This slow precession rate suggests that stellar winds from the disk will collide and shock, driving rapid gas inflows and fueling an episodic central starburst as suggested in Chang et al.

A New Class of Transients Marking Intensified Accretion onto Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Trakhtenbrot, Benny; Arcavi, Iair; Ricci, Claudio; Horesh, Assaf; Tacchella, Sandro; Stern, Daniel

2018-01-01

Our understanding of the demographics and evolution of supermassive black holes (SMBHs) beyond the local universe is limited to actively growing SMBHs, where relatively stable accretion of gas persists over several hundreds of millions of years. A growing number of transient and/or variable phenomena in galaxy nuclei have recently begun to shed new light on SMBH demographics and the physics of gas accretion onto these objects, tracing events where this accretion has drastically intensified. We present such an event, identified in the nucleus of an early-type galaxy at z=0.064, in which a previously-active SMBH experienced a dramatic increase in ultraviolet-optical emission. The emerging optical spectrum exhibits a mix of emission features, some of which are typical of luminous, unobscured active galactic nuclei. Other observed emission features of high-ionization species are likely driven by Bowen fluorescence -- seen for the first time in high-velocity lines, with ~2000 km/s, in a galaxy nucleus -- originating in dense, metal-rich gas that is exposed to the recently intensified UV radiation. Our multiwavelength space- and ground-based monitoring campaign shows that the spectral features and elevated UV flux show little to no evolution, over a period of at least six months. This disfavours the tidal disruption of a star as the origin of the UV “flash”, but suggests a rather longer-term re-ignition event. This event joins two other recently reported transients with similar emission properties, forming a new class of transients which has important implications for the identification and understanding of tidal disruption events, as well as other drivers of SMBH re-ignition.

Feeding, Feedback and the Growth of Galaxies - Molecules as Tools for Probing Galaxy Evolution

NASA Astrophysics Data System (ADS)

Aalto, Susanne

2017-06-01

Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. Some (U)LIRGS have deeply embedded galaxy nuclei that harbour a very active evolutionary stage of AGNs and/or starbursts. The nuclear activity will often drive mechanical feedback in the form of molecular winds, jets and outflows. This feedback can for example remove baryons from low-mass galaxies, prevent overgrowth of galaxies, be linked to the M_{BH}-σ relation, and explain "red-and dead" properties of local ellipticals. With the ALMA and NOEMA telescopes we can use molecules as diagnostic tools to probe the properties of dust-enshrouded galaxy nuclei and their associated cold winds and outflows. Their morphology, velocity structure, physical conditions and even chemistry can be studied at unprecedented sensitivity and resolution, opening new avenues to further our understanding of the growth of galaxies. I will give a brief review of the ALMA/NOEMA view of AGN and starburst radiative and mechanical feedback, and how it is linked to the properties of the nuclear power source. I will discuss the use of molecules (e.g. H_2O, H_3O^{+}, HCN, HCO^+, H_2S) for studying dusty nuclei and the nature of the embedded activity. We can, for example, investigate ionization rates and the impact of cosmic ray-, X-ray- and PDR-chemistry and the onset of outflows and winds. Interestingly, in some deeply obscured nuclei the chemistry shows strong similarities to that of Galactic hot cores. Finally I will show peculiar molecular jets and very recent ALMA observations at resolutions of tens of milli-arcseconds (few pc) of vibrationally excited HCN in opaque nuclei. These regions offer both challenges and opportunities for IR and submm studies of the nature of the buried activity - which we suggest is a deeply dust-enshrouded SMBH in a high-accretion state, or an extreme, high-temperature, burst of star formation.

Bulgeless Galaxies Hosting 107 M⊙ AGN in Galaxy Zoo: The Growth of Black Holes via Secular Processes

NASA Astrophysics Data System (ADS)

Simmons, Brooke; Lintott, C. J.; Schawinski, K.; Moran, E. C.; Han, A.; Kaviraj, S.; Masters, K. L.; Urry, C. M.; Willett, K.; Bamford, S. P.; Nichol, R.

2013-01-01

The growth of supermassive black holes (SMBHs) appears to proceed via multiple pathways including mergers and secular processes, but these are difficult to disentangle for most galaxies given their complex evolutionary histories. In order to understand the effects of secular galaxy evolution on black hole growth, we require a sample of active galactic nuclei (AGN) in galaxies with a calm formation history free of significant mergers, a population that heretofore has been difficult to locate. Here we present a sample of 13 AGN in massive galaxies lacking the classical bulges believed inevitably to result from mergers; they also either lack or have extremely small pseudobulges, meaning they have had very calm accretion histories. This is the largest sample to date of massive, bulgeless AGN host galaxies selected without any direct restriction on the SMBH mass. The broad-line objects in the sample have black hole masses of 106-7 M⊙ Eddington arguments imply similar masses for the rest of the sample, meaning these black holes have grown substantially in the absence of mergers or other bulge-building processes such as violent disk instabilities. The black hole masses are systematically higher than expected from established bulge-black hole relations. However, these systems may be consistent with the correlation between black hole mass and total stellar mass. We discuss these results in the context of other studies and consider the implication that the details of stellar galaxy evolution and dynamics may not be fundamental to the co-evolution of galaxies and black holes.

Small Seed Black Hole Growth in Various Accretion Regimes

NASA Astrophysics Data System (ADS)

Gerling-Dunsmore, Hannalore J.; Hopkins, Philip F.

2016-03-01

Observational evidence indicates a population of super massive black holes (SMBHs) (~109 -1010M⊙) formed within 1 Gyr after the Big Bang. One proposed means of SMBH formation is accretion onto small seed black holes (BHs) (~ 100M⊙). However, the existence of SMBHs within 1 Gyr requires rapid growth, but conventional models of accretion fail to grow the seed BHs quickly enough. Super Eddington accretion (Ṁ >ṀEddington) may aid in improving growth efficiency. We study small seed BH growth via accretion in 3D, using the magneto-hydrodynamics+gravity code GIZMO. In particular, we consider a BH in a high density turbulent star-forming cloud, and ask whether or not the BH can capture sufficient gas to grow rapidly. We consider both Eddington-limited and super Eddington regimes, and resolve physics on scales from 0.1 pc to 1 kpc while including detailed models for stellar feedback physics, including stellar winds, supernovae, radiation pressure, and photo-ionization. We present results on the viability of different small seed BHs growing into SMBH candidates.

A simple way to improve AGN feedback prescription in SPH simulations

NASA Astrophysics Data System (ADS)

Zubovas, Kastytis; Bourne, Martin A.; Nayakshin, Sergei

2016-03-01

Active galactic nuclei (AGN) feedback is an important ingredient in galaxy evolution, however its treatment in numerical simulations is necessarily approximate, requiring subgrid prescriptions due to the dynamical range involved in the calculations. We present a suite of smoothed particle hydrodynamics simulations designed to showcase the importance of the choice of a particular subgrid prescription for AGN feedback. We concentrate on two approaches to treating wide-angle AGN outflows: thermal feedback, where thermal and kinetic energy is injected into the gas surrounding the supermassive black hole (SMBH) particle, and virtual particle feedback, where energy is carried by tracer particles radially away from the AGN. We show that the latter model produces a far more complex structure around the SMBH, which we argue is a more physically correct outcome. We suggest a simple improvement to the thermal feedback model - injecting the energy into a cone, rather than spherically symmetrically - and show that this markedly improves the agreement between the two prescriptions, without requiring any noticeable increase in the computational cost of the simulation.

The NANOGrav 11 Year Data Set: Pulsar-timing Constraints on the Stochastic Gravitational-wave Background

NASA Astrophysics Data System (ADS)

Arzoumanian, Z.; Baker, P. T.; Brazier, A.; Burke-Spolaor, S.; Chamberlin, S. J.; Chatterjee, S.; Christy, B.; Cordes, J. M.; Cornish, N. J.; Crawford, F.; Thankful Cromartie, H.; Crowter, K.; DeCesar, M.; Demorest, P. B.; Dolch, T.; Ellis, J. A.; Ferdman, R. D.; Ferrara, E.; Folkner, W. M.; Fonseca, E.; Garver-Daniels, N.; Gentile, P. A.; Haas, R.; Hazboun, J. S.; Huerta, E. A.; Islo, K.; Jones, G.; Jones, M. L.; Kaplan, D. L.; Kaspi, V. M.; Lam, M. T.; Lazio, T. J. W.; Levin, L.; Lommen, A. N.; Lorimer, D. R.; Luo, J.; Lynch, R. S.; Madison, D. R.; McLaughlin, M. A.; McWilliams, S. T.; Mingarelli, C. M. F.; Ng, C.; Nice, D. J.; Park, R. S.; Pennucci, T. T.; Pol, N. S.; Ransom, S. M.; Ray, P. S.; Rasskazov, A.; Siemens, X.; Simon, J.; Spiewak, R.; Stairs, I. H.; Stinebring, D. R.; Stovall, K.; Swiggum, J.; Taylor, S. R.; Vallisneri, M.; van Haasteren, R.; Vigeland, S.; Zhu, W. W.; The NANOGrav Collaboration

2018-05-01

We search for an isotropic stochastic gravitational-wave background (GWB) in the newly released 11 year data set from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). While we find no evidence for a GWB, we place constraints on a population of inspiraling supermassive black hole (SMBH) binaries, a network of decaying cosmic strings, and a primordial GWB. For the first time, we find that the GWB constraints are sensitive to the solar system ephemeris (SSE) model used and that SSE errors can mimic a GWB signal. We developed an approach that bridges systematic SSE differences, producing the first pulsar-timing array (PTA) constraints that are robust against SSE errors. We thus place a 95% upper limit on the GW-strain amplitude of A GWB < 1.45 × 10‑15 at a frequency of f = 1 yr‑1 for a fiducial f ‑2/3 power-law spectrum and with interpulsar correlations modeled. This is a factor of ∼2 improvement over the NANOGrav nine-year limit calculated using the same procedure. Previous PTA upper limits on the GWB (as well as their astrophysical and cosmological interpretations) will need revision in light of SSE systematic errors. We use our constraints to characterize the combined influence on the GWB of the stellar mass density in galactic cores, the eccentricity of SMBH binaries, and SMBH–galactic-bulge scaling relationships. We constrain the cosmic-string tension using recent simulations, yielding an SSE-marginalized 95% upper limit of Gμ < 5.3 × 10‑11—a factor of ∼2 better than the published NANOGrav nine-year constraints. Our SSE-marginalized 95% upper limit on the energy density of a primordial GWB (for a radiation-dominated post-inflation universe) is ΩGWB(f) h 2 < 3.4 × 10‑10.

Constraints on the Nature of CID-42: Recoil Kick or Supermassive Black Hole Pair?

NASA Technical Reports Server (NTRS)

Blecha, Laura; Civano, Francesca; Elvis, Martin; Loeb, Abraham

2012-01-01

The galaxy CXOC J100043.1+020637, also known as CID-42, is a highly unusual object. An apparent galaxy merger remnant, it displays signatures of both an inspiraling, kiloparsecscale active galactic nucleus (AGN) pair and of a recoiling AGN with a kick velocity approximately greater than 1300 km s(exp -1). Among recoiling AGN candidates, CID-42 alone has both spatial offsets (in optical and X-ray bands) and spectroscopic offsets. In order to constrain the relative likelihood of both scenarios, we develop models using hydrodynamic galaxy merger simulations coupled with radiative transfer calculations. Our gas-rich, major merger models are generally well matched to the galactic morphology and to the inferred stellar mass and star formation rate. We show that a recoiling supermassive black hole (SMBH) in CID-42 should be observable as an AGN at the time of observation. However, in order for the recoiling AGN to produce narrow-line emission, it must be observed shortly after the kick while it still inhabits a dense gaseous region, implying a large total kick velocity (vk approximately greater than 2000 km s(exp -1)). For the dual AGN scenario, an unusually large broad-line offset is required, and the best match to the observed morphology requires a galaxy that is less luminous than CID-42. Further, the lack of X-ray emission from one of the two optical nuclei is not easily attributed to an intrinsically quiescent SMBH or to a Compton-thick galactic environment. While the current data do not allow either the recoiling or the dual AGN scenario for CID-42 to be excluded, our models highlight the most relevant parameters for distinguishing these possibilities with future observations. In particular, high-quality, spatially-resolved spectra that can pinpoint the origin of the broad and narrow line features will be critical for determining the nature of this unique source.

Continuum Reverberation Mapping of the Accretion Disks in Two Seyfert 1 Galaxies

NASA Astrophysics Data System (ADS)

Fausnaugh, M. M.; Starkey, D. A.; Horne, Keith; Kochanek, C. S.; Peterson, B. M.; Bentz, M. C.; Denney, K. D.; Grier, C. J.; Grupe, D.; Pogge, R. W.; De Rosa, G.; Adams, S. M.; Barth, A. J.; Beatty, Thomas G.; Bhattacharjee, A.; Borman, G. A.; Boroson, T. A.; Bottorff, M. C.; Brown, Jacob E.; Brown, Jonathan S.; Brotherton, M. S.; Coker, C. T.; Crawford, S. M.; Croxall, K. V.; Eftekharzadeh, Sarah; Eracleous, Michael; Joner, M. D.; Henderson, C. B.; Holoien, T. W.-S.; Hutchison, T.; Kaspi, Shai; Kim, S.; King, Anthea L.; Li, Miao; Lochhaas, Cassandra; Ma, Zhiyuan; MacInnis, F.; Manne-Nicholas, E. R.; Mason, M.; Montuori, Carmen; Mosquera, Ana; Mudd, Dale; Musso, R.; Nazarov, S. V.; Nguyen, M. L.; Okhmat, D. N.; Onken, Christopher A.; Ou-Yang, B.; Pancoast, A.; Pei, L.; Penny, Matthew T.; Poleski, Radosław; Rafter, Stephen; Romero-Colmenero, E.; Runnoe, Jessie; Sand, David J.; Schimoia, Jaderson S.; Sergeev, S. G.; Shappee, B. J.; Simonian, Gregory V.; Somers, Garrett; Spencer, M.; Stevens, Daniel J.; Tayar, Jamie; Treu, T.; Valenti, Stefano; Van Saders, J.; Villanueva, S., Jr.; Villforth, C.; Weiss, Yaniv; Winkler, H.; Zhu, W.

2018-02-01

We present optical continuum lags for two Seyfert 1 galaxies, MCG+08-11-011 and NGC 2617, using monitoring data from a reverberation mapping campaign carried out in 2014. Our light curves span the ugriz filters over four months, with median cadences of 1.0 and 0.6 days for MCG+08-11-011 and NGC 2617, respectively, combined with roughly daily X-ray and near-UV data from Swift for NGC 2617. We find lags consistent with geometrically thin accretion-disk models that predict a lag-wavelength relation of τ ∝ λ 4/3. However, the observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC 2617. These differences can be explained if the mass accretion rates are larger than inferred from the optical luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC 2617, although uncertainty in the SMBH masses determines the significance of this result. While the X-ray variability in NGC 2617 precedes the UV/optical variability, the long (2.6 day) lag is problematic for coronal reprocessing models.

First X-ray Statistical Tests for Clumpy Torii Models: Constraints from RXTE monitoring of Seyfert AGN

NASA Astrophysics Data System (ADS)

Markowitz, A.

2015-09-01

We summarize two papers providing the first X-ray-derived statistical constraints for both clumpy-torus model parameters and cloud ensemble properties. In Markowitz, Krumpe, & Nikutta (2014), we explored multi-timescale variability in line-of-sight X-ray absorbing gas as a function of optical classification. We examined 55 Seyferts monitored with the Rossi X-ray Timing Explorer, and found in 8 objects a total of 12 eclipses, with durations between hours and years. Most clouds are commensurate with the outer portions of the BLR, or the inner regions of infrared-emitting dusty tori. The detection of eclipses in type Is disfavors sharp-edged tori. We provide probabilities to observe a source undergoing an absorption event for both type Is and IIs, yielding constraints in [N_0, sigma, i] parameter space. In Nikutta et al., in prep., we infer that the small cloud angular sizes, as seen from the SMBH, imply the presence of >10^7 clouds in BLR+torus to explain observed covering factors. Cloud size is roughly proportional to distance from the SMBH, hinting at the formation processes (e.g. disk fragmentation). All observed clouds are sub-critical with respect to tidal disruption; self-gravity alone cannot contain them. External forces (e.g. magnetic fields, ambient pressure) are needed to contain them, or otherwise the clouds must be short-lived. Finally, we infer that the radial cloud density distribution behaves as 1/r^{0.7}, compatible with VLTI observations. Our results span both dusty and non-dusty clumpy media, and probe model parameter space complementary to that for short-term eclipses observed with XMM-Newton, Suzaku, and Chandra.

Compton Thick AGN in the COSMOS field

NASA Astrophysics Data System (ADS)

Lanzuisi, Giorgio; Cosmos Collaboration

2015-09-01

I will present the results we published in a couple of recent papers (Lanzuisi et al. 2015, A&A 573A 137, Lanzuisi et al. 2015, arXiv 1505.01153) on the properties of X-ray selected Compton Thick (CT, NH>10^24 cm^-2) AGN, in the COSMOS survey. We exploited the rich multi-wavelength dataset available in this field, to show that CT AGN tend to harbor smaller, rapidly growing SMBH with respect to unobscured AGN, and have a higher chance of being hosted by star-forming, merging and post-merger systems.We also demonstrated the detectability of even more heavily obscured AGN (NH>10^25 cm^-2), thanks to a truly multi-wavelength approach in the same field. The extreme source detected in this way shows strong evidences of ongoing powerful AGN feedback, detected as blue-shifted wings of high ionization optical emission lines such as [NeV] and [FeVII], as well as of the [OIII] emission line.The results obtained from these works point toward a scenario in which highly obscured AGN occupy a peculiar place in the galaxy-AGN co-evolution process, in which both the host and the SMBH rapidly evolve toward the local relations.We will also present estimates on the detectability of such extreme sources up to redshift ~6-7 with Athena. Combining the most up to date models for the Luminosity Function of CT AGN at high z, aggressive data analysis techniques on faint sources, and the current Athena survey design, we demonstrate that we will detect, and recognize as such, a small (few to ten) but incredibly valuable sample of CT AGN at such high redshift.

Astrophysical phenomena related to supermassive black holes

NASA Astrophysics Data System (ADS)

Pott, Jörg-Uwe

2006-12-01

The thesis contains the results of my recent projects in astrophysical research. All projects aim at pushing the limits of our knowledge about the interaction between a galaxy, the fundamental building block of today's universe, and a supermassive black hole (SMBH) at its center. Over the past years a lot of observational evidence has been gathered for the current understanding, that at least a major part of the galaxies with a stellar bulge contain central SMBHs. The typical extragalactic approach consists of searching for the spectroscopic pattern of Keplerian rotation, produced by stars and gas, when orbiting a central dark mass (Kormendy & Richstone 1995). It suggests that a significant fraction of large galaxies host in their very nucleus a SMBH of millions to billions of solar masses (Kormendy & Gebhardt 2001). In the closest case, the center of our Milky Way, the most central stars, which can be imaged, were shown to move on orbits with circulation times of a few decades only, evidencing a mass and compactness of the dark counter part of the Keplerian motion, which can only be explained by a SMBH (Eckart & Genzel 1996; Ghez et al. 2000; Schödel et al. 2002). Having acknowledged the widespread existence of SMBHs the obvious next step is investigating the interaction with their environment. Although the basic property of a SMBH, which is concentrating a huge amount of mass in a ludicrously small volume defined by the Schwarzschild radius, only creates a deep gravitational trough, its existence evokes much more phenomena than simply attracting the surrounding matter. It can trigger or exacerbate star formation via tidal forces (Morris 1993). It shapes the distribution of its surrounding matter to accretion discs, which themselves release gravitational potential energy as radiation, possibly due to magnetic friction (Blandford 1995). The radiation efficiency of such active galactic nuclei (AGN) can become roughly 100 times more efficient than atomic nuclear reactions in stars. In the most active galaxies known, the radiating accretion disc of the central SMBH engine easily outshines the stellar light of the entire galaxy (Blandford 1995). In addition to the light, plasma streams can emerge from the innermost regions at relativistic velocities, returning energy to the host galaxy (host) and creating jets and lobes with strong observational signatures, especially at radio and X-ray wavelengths (Wilson 2003). New insights in the wide field of SMBH/host interaction are often related to the development of new, more sensitive instruments and telescopes. For example the idea, that a high luminosity AGN may result from a merger event between two galaxies, could only develop with the upcoming high resolution and sensitive imaging capabilities needed to detect the highly distorted host galaxy morphologies of (post-)merger galaxies (Heckman et al. 1986). Furthermore multi-wavelength approaches, which combine the results of measurements at different wavelengths, often lead to new conclusions or confirm unsecured hypotheses. Thus developing a new instrument can be as valuable as combining different datasets. I follow both approaches and developed projects which (i) deal with new instrumentation and telescope technology, (ii) combine datasets from different wavelengths and resolutions, and (iii) incorporate recent theoretical models and predictions, which can be verified empirically. While some projects are more focused on investigating the power of new observational techniques, others incorporate acknowledged instruments to probe predictions based on previous observations and models and trace special phenomena of SMBH/host interaction. But in most cases aspects of all three items appear. The SMBH/host interaction results in phenomena at all linear size scales of the system, from the direct accretion of matter onto the central black hole up to radio jets crossing the entire galaxy. Thus interaction effects do not simply concentrate on the innermost region of a galaxy. Furthermore an increasing number of apparently totally distinct phenomena and properties of the SMBH/host system appear to be related to each other, provoking unifying ideas and models to explain the galaxy formation and evolution. For example several different types of AGN are understood as projection or orientation effects, claiming that the same AGN looks totally different as viewed from different sides (e.g. Antonucci & Miller 1985). The thesis is structured to reflect this general perception. All scales of size, AGN luminosity, and nuclear activity appear. The thesis consists of six chapters. The first two compile astrophysical and technical background of the individual projects, which themselves are presented in the following four chapters. While the first project (Chapter 3) deals with observations of the innermost parsec of our Galaxy, Chapter 4 presents data of the inner kpc of an active galaxy. The subjects of Chapters 5 and 6 are very luminous AGN/host systems, so-called QSOs. Whereas Chapter 5 presents global, spatially unresolved properties of SMBH/host systems, the radio jet, analyzed in the final Chapter 6, combines all size scales. It is investigated from close to its origin out to several kpc. The accretion onto the black hole of the Milky Way (Chapter 3) is extremely inefficient (Genzel et al. 2003a) and the SMBH possibly interacts dominantly via tidal forces only. The next discussed system (Chapter 4) is the prototype of moderately luminous Seyfert 2 AGN, NGC 1068. Here a strong local influence of the nuclear X-ray radiation is observed (Usero et al. 2004). Chapter 5 deals with the possible global importance of radiative interaction between highly luminous QSO AGN and the host. The radio jet in Chapter 6 definitely shows signs of interaction with the matter of its host several kpc away from the nucleus. Chapters 3-6 include a dedicated introductory and a conclusive section, which put the results obtained in the larger astrophysical context of the observation. The observational techniques chosen vary in dependence of the observed phenomenon. One major goal of especially Chapters 3 and 4 is to prove by successful explorative observations the scientific perspectives of the new instruments. Chapter 3 deals with the pioneering interferometric infrared study of stellar sources and their surroundings in the immediate vicinity of the SMBH at the center of the Milky Way. I was able to use the resolving power of an optical large baseline interferometer (OLBI) to investigate for the first time the different structures and excitation conditions of interstellar and circumstellar dust in 200 mpc distance to the SMBH. It is unknown whether the standard models for star and dust formation, which themselves dominate the infrared appearance of an inactive galaxy as the Milky Way, still apply under the strong tidal forces of gravity, exerted by the central SMBH. During the course of my doctoral research, I worked 2.5 years within the VLT Interferometry (VLTI) group of the European Southern Observatory (ESO) in M"unchen and Chile. I obtained the very first infrared fringes on GC sources and investigated the different instrument capabilities at the current sensitivity limit of the VLTI. The VLTI is the world leading stellar interferometric facility providing the infrastructure to combine the light of up to four 8m-class Adaptive Optics corrected telescopes, which themselves represent the state-of-the-art of optical-infrared telescope technology. The accomplished work includes the investigation of different data reduction techniques with respect to maximum accuracy and signal-to-noise ratios. The VLTI is right in the process of construction. While first modes are already open to the astronomical community, several advanced modes and instruments are still at different preliminary stages, ranging from early design studies to advanced instrument commissioning. The experiences of my VLTI observations, fully exploiting the currently available observing modes, and the data reduction were fed back via close collaboration to the Paranal Observatory and to the European science institutes of the instrument developing consortia1 . I contributed to improve the observing process (in particular to the infrared-based target acquisition of the instrument, and to the clarification of the chopping parameters) and the standard data reduction package (wavelength calibration, software debugging). The most recent NIR three-baseline observations of the GCIRS 7 helped to uncover imperfections in the numerical delay line model, which is needed to track the fringes during the observations. The smaller coherence lengths of these wide band observations were an ideal case to optimize the detector integration times for reaching highest signal-to-noise-ratios (SNR). The VLTI observations, described in Chapter 3, are the first observations of stellar interferometry in the infrared, which target objects through the 25 magnitudes of optical extinction along the line of sight toward the GC. One motivation for these observations, in addition to the direct scientific intention, was to create a showcase for advanced optical interferometry applications at the GC. An important part of the thesis is the detailed analysis of the achievable accuracy of the interferometric measurements. Such a precision study under the challenging conditions of off-axis optical AO guiding and faint target brightnesses close to the system limits has not been published before. Most of the interferometric observations were executed in the mid-infrared (MIR) wavelength regime at 10 μm (N -band), a natural starting point, because the optical requirements to the accuracy of the VLTI infrastructure are lower at these longer infrared wavelengths. The observed GCIRS 3 is an outstanding source at 10 μm being the most compact, brightest and isolated source at the GC. It bears significat signs of dust formation and will play a major role in understanding the dust formation and chemical properties of the local interstellar dust in the central parsec. The interferometric data of two observing seasons were interpreted together with different single telescope datasets. GCIRS 3 is known to be a very red luminous source, but no stellar spectrum could give away more detailed properties of the underlying source. I use a one-dimensional radiative transfer model to investigate the resolved dust shell properties, as observed with the 20 mas resolution of the VLTI at 10 μm. For the first time I can present results that show that the direct zone of dust formation around the deeply embedded star is observable. The temperature, derived from the spectral properties, and the spatial size, as derived from the high resolution interferometric dataset, show the cool star nature of the object. Earlier spatially unresolved N -band spectroscopic observations found a significant increase of oxygen rich silicate absorption towards GCIRS 3, deeper than towards the neighboring stars. The spectral properties of the VLTI data show that the immediate dust shell, formed by IRS 3 is not responsible for this strong absorption and might be devoid of a significant amount of silicate, favoring GCIRS 3 being a cool supergiant of ˜ 3000 K stellar temperature, forming more carbon-rich dust. The main impact of this result on GC science is, that the silicate-poor dust formation of GCIRS 3 and its silicate-rich surroundings appear to be the best place to study the extraordinary enrichment of the GC dust with interstellar amorphous silicate molecules (Roche & Aitken 1985). The dust formation in the nucleus of a galaxy is important, since only a detailed understanding of its composition helps to interpret the observed spectra and spectral energy distribution of spatially unresolved dusty nuclei of other galaxies. Furthermore the confirmed existence of a second massive red supergiant so close to GCIRS 7, which is already known to be a red supergiant, challenges the theories of star formation in galactic nuclei. Further currently possible VLTI-GC observations are presented in the following sections of Chapter 3. The dimensions of stellar bow-shocks are analyzed for the first time in the MIR to add information to the understanding of the kinematic features, which arise if massive stars with strong stellar winds ram into dense interstellar material. Such shock fronts can excite molecular hydrogen and add to the understanding of the excitation mechanisms in galactic nuclei (Pineau des Forêts et al. 2001). I show that such stellar bow-shocks are observable with the VLTI, and derive lower limits for their extension. Another set of first GC fringes was achieved in the near-infrared (NIR) at 2 μm on GCIRS 7. In one section of this chapter I describe the special importance of this star for future interferometric phase-referencing experiments. Despite of the technical problems occurred, fringes were found on one of the observed baseline, proving the feasibility of a detailed interferometric study of this putative phase calibrator in the near future. Phase referencing will significantly increase the number of observable targets, as soon as the respective hardware will be implemented. The following Chapter 4 reports on the first extragalactic sub-mm spectra of the innermost region in the Seyfert 2 prototype NGC 1068 with the new APEX telescope facility. The emission of the molecular rotational excitation lines CO(J=3-2) and HCN(J=4-3) were observed during the instrument testing phase. While the observations served for debugging the telescope operation, I prove that with dedicated data reduction already the current limited receiver capabilities are sufficient to measure broad extragalactic molecular line transitions in the sub-mm atmospheric transmission window. The observed lines are indispensable tracers of the warm and dense molecular gas (Papadopoulos & Seaquist 1999). The molecular gas is the major reservoir of matter in a galaxy, which supplies star formation and mass accretion onto the central SMBH. In Chapter 5, I present the results of the search for rotational line transitions at 80 GHz, in particular the 1-0 transition of the HCN molecule. It traces gas densities larger than 10e4/cm3 and is therefore a better quantitative tracers of the regions where star formation actually occurs than the stronger CO(1-0) transition, which correlates to the total amount of molecular gas which could be transformed into stars (Gao & Solomon 2004). The observed galaxies host a luminous quasar in their core. In nearby low luminosity AGN a relatively enhanced excitation of the HCN transition close to the central engine is observed (Usero et al. 2004). I investigate the hypothesis of an amplification and extension of this effect in high luminosity AGN from local nuclear to global galactic scales. Moreover the infrared luminosity ratios is used to trace global AGN dominance efficiently Then the detectability of enhanced HCN intensities due to intense nuclear X-ray irradiation and ionization is investigated. The measured upper limits are consistent with both normal and relatively enhanced HCN excitation. Quantitatively my results show that the detection of the expected HCN intensities in a statistically valuable sample of quasar host galaxies is within reach. In the last chapter, I analyze the physical properties of the radio jet in the radio loud quasar J1101+7225, which shows exceptionally far away from its nuclear origin (4 kpc) high relativistic motions. After a reanalysis of the cm-VLBI data, presented by Pott (2003), I include higher frequency data to follow the jet down to the hundred pc scale. The full analysis of the radio properties reveals an exemplary radio jet, which shows a complex inner structure including a possibly helical morphology. Far outside the nuclear region the jet rams into the host galaxy, which leads to a bending of the direction of propagation. Consequences for the galactic evolution of such interaction between the innermost accretion phenomenon and the surrounding host galaxy, which is typical for radio loud quasars, are not known yet. The diversity of the observations and results obtained gives an impression of the wide range of possible interactions between supermassive black holes and their host galaxies as well as of the many ways to observe them. Most of the presented results are published in peer-reviewed journals and presented at several conferences.

VizieR Online Data Catalog: Pinpointing the SMBH in NGC1052 (Baczko+, 2016)

NASA Astrophysics Data System (ADS)

Baczko, A.-K.; Schulz, R.; Kadler, M.; Ros, E.; Perucho, M.; Krichbaum, T. P.; Bock, M.; Bremer, M.; Grossberger, C.; Lindqvist, M.; Lobanov, A. P.; Mannheim, K.; Marti-Vidal, I.; Mueller, C.; Wilms, J.; Zensus, J. A.

2016-06-01

The source NGC1052 was observed with the GMVA at 86GHz in Oct. 2004. One naturally weighted and one uniformly weighted CLEAN-image as FITS-files (Fig. 1 and 2) and one tapered map with more weight to short baselines as FITS-file (Fig. 3). (2 data files).

The Stellar Cusp in the Galactic Center: Three-Dimensional Orbits of Stars

NASA Astrophysics Data System (ADS)

Chappell, Samantha; Ghez, Andrea M.; Boehle, Anna; Yelda, Sylvana; Sitarski, Breann; Witzel, Gunther; Do, Tuan; Lu, Jessica R.; Morris, Mark; Becklin, Eric E.

2015-01-01

We present new findings from our long term study of the nuclear star cluster around the Galaxy's central supermassive blackhole (SMBH). Measurements where made using speckle and laser guided adaptive optics imaging and integral field spectroscopy on the Keck telescopes. We report 13 new measurable accelerating sources around the SMBH, down to ~17 mag in K band, only 4 of which are known to be young stars, the rest are either known to be old stars or have yet to be spectral typed. Thus we more than double the number of measured accelerations for the known old stars and unknown spectral type population (increasing the number from 6 to 15). Previous observations suggest a flat density profile of late-type stars, contrary to the theorized Bahcall-Wolf cusp (Bahcall & Wolf 1976, 1977; Buchholz et al. 2009; Do et al. 2009; Bartko et al. 2010). With three-dimensional orbits of significantly accelerating sources, we will be able to better characterize the stellar cusp in the Galactic center, including the slope of the stellar density profile.

A highly magnetized twin-jet base pinpoints a supermassive black hole

NASA Astrophysics Data System (ADS)

Baczko, A.-K.; Schulz, R.; Kadler, M.; Ros, E.; Perucho, M.; Krichbaum, T. P.; Böck, M.; Bremer, M.; Grossberger, C.; Lindqvist, M.; Lobanov, A. P.; Mannheim, K.; Martí-Vidal, I.; Müller, C.; Wilms, J.; Zensus, J. A.

2016-09-01

Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could be the case for NGC 1052, to launch these jets. This requires magnetic fields on the order of 103G to 104G. We imaged the vicinity of the SMBH of the AGN NGC 1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the magnetic field at 1 Schwarzschild radius to lie between 200 G and ~ 8.3 × 104 G consistent with Blandford & Znajek models. The VLBI images shown in Figs. 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A47

Beating the confusion limit: the necessity of high angular resolution for probing the physics of Sagittarius A* and its environment: opportunities for LINC-NIRVANA (LBT), GRAVITY (VLTI) and and METIS (E-ELT)

NASA Astrophysics Data System (ADS)

Eckart, A.; Sabha, N.; Witzel, G.; Straubmeier, C.; Shahzamanian, B.; Valencia-S., M.; García-Marín, Macarena; Horrobin, M.; Moser, L.; Zuther, J.; Fischer, S.; Rauch, C.; Rost, S.; Iserlohe, C.; Yazici, S.; Smajic, S.; Wiest, M.; Araujo-Hauck, C.; Wank, I.

2012-07-01

The super-massive 4 million solar mass black hole (SMBH) SgrA* shows variable emission from the millimeter to the X-ray domain. A detailed analysis of the infrared light curves allows us to address the accretion phenomenon in a statistical way. The analysis shows that the near-infrared flux density excursions are dominated by a single state power law, with the low states of SgrA* are limited by confusion through the unresolved stellar background. We show that for 8-10m class telescopes blending effects along the line of sight will result in artificial compact star-like objects of 0.5-1 mJy that last for about 3-4 years. We discuss how the imaging capabilities of GRAVITY at the VLTI, LINC-NIRVANA at the LBT and METIS at the E-ELT will contribute to the investigation of the low variability states of SgrA*.

Active Galactic Nuclei and X-ray Ovservations

NASA Astrophysics Data System (ADS)

Vasylenko, A. A.; Zhdanov, V. I.; Fedorova, E. V.

2016-11-01

Active galactic nuclei (AGN) are the brightest objects in the Universe and their brightness is mainly caused by accretion of m atter onto supermassive black holes (SMBH). This is the common reason of the AGN activity. However, every AGN has differences and fine features, which are the subject of an intensive investigation. The occurrence of such highly-relativistic objects as SMBH residing at the AGN core makes them an excellent laboratory for testing the fundamental physical theories. The X-rays and gamma-rays generated in a corona of an accretion disc around SMBH yield valuable information for these tests, the radiation in the range of 1-100 keV being at present the most informative source. However, there are a number of obstacles for such a study due to different physical processes that complicate the interpretation of observations in different bands of the electromagnetic radiation. In this paper, we review the current concepts concerning the structure of AGNs with a focus on the central part of these objects th at require relativistic theories for their understanding. The basic notions of the unified AGN schemes are considered; some modifications are reviewed. The paper contains the following sections. I. Introduction; II. Observational manifestations and classification of galaxies with active nuclei (II.A. Optical observations; II.B. Radio observations; II.C. X-ray data; II.D Infrared data; II.E. AGN anatomy with multywave data); III. AGN "central machine"; III.A. Black holes; III.B. Accretion disc types; III.C. Corona; III.D. AGN unified scheme); IV. Simulation X-ray AGN spectra (IV.A. The power-law contimuum and the exponential cut-off; IV.B. The absorption of X-rays; IV.C. Reflection; IV.D. Fe K a line; IV.E. Spin paradigm); V. AGN as a laboratory to test the fundamental interactions (V.A. Strong gravitational fields; V.B. Dynamic dark energy near compact astrophysical objects

Confusing Binaries: The Role of Stellar Binaries in Biasing Disk Properties in the Galactic Center

NASA Astrophysics Data System (ADS)

Naoz, Smadar; Ghez, Andrea M.; Hees, Aurelien; Do, Tuan; Witzel, Gunther; Lu, Jessica R.

2018-02-01

The population of young stars near the supermassive black hole (SMBH) in the Galactic Center (GC) has presented an unexpected challenge to theories of star formation. Kinematic measurements of these stars have revealed a stellar disk structure (with an apparent 20% disk membership) that has provided important clues regarding the origin of these mysterious young stars. However, many of the apparent disk properties are difficult to explain, including the low disk membership fraction and the high eccentricities given the youth of this population. Thus far, all efforts to derive the properties of this disk have made the simplifying assumption that stars at the GC are single stars. Nevertheless, stellar binaries are prevalent in our Galaxy, and recent investigations suggested that they may also be abundant in the Galactic Center. Here, we show that binaries in the disk can largely alter the apparent orbital properties of the disk. The motion of binary members around each other adds a velocity component, which can be comparable to the magnitude of the velocity around the SMBH in the GC. Thus, neglecting the contribution of binaries can significantly vary the inferred stars’ orbital properties. While the disk orientation is unaffected, the apparent disk’s 2D width will be increased to about 11.°2, similar to the observed width. For a population of stars orbiting the SMBH with zero eccentricity, unaccounted for binaries will create a wide apparent eccentricity distribution with an average of 0.23. This is consistent with the observed average eccentricity of the stars’ in the disk. We suggest that this high eccentricity value, which poses a theoretical challenge, may be an artifact of binary stars. Finally, our results suggest that the actual disk membership might be significantly higher than the one inferred by observations that ignore the contribution of binaries, alleviating another theoretical challenge.

The Incidence of Buried Dual AGN in Advanced Mergers: New results from Chandra

NASA Astrophysics Data System (ADS)

Pfeifle, Ryan William; Satyapal, Shobita; Secrest, Nathan; Gliozzi, Mario; Ricci, Claudio; Ellison, Sara L.; Blecha, Laura; Rothberg, Barry; Constantin, Anca

2018-01-01

Since the vast majority of galaxies contain supermassive black holes (SMBHs) and galaxy interactions trigger nuclear gas accretion, a direct consequence of the hierarchical model of galaxy formation would be the existence of dual active galactic nuclei (AGN). The existence, frequency, and characteristics of such dual AGN have important astrophysical implications on the SMBH mass function, the interplay between SMBHs and the host galaxy, and the M-sigma relation. Despite decades of searching, and strong theoretical reasons for their existence, observationally confirmed cases of dual AGN are extremely rare, and most have been discovered serendipitously. Using the all-sky WISE survey, we identified a population of over one hundred strongly interacting galaxies that display extreme red mid-infrared colors thus far exclusively associated with extragalactic sources possessing powerful AGN. In a recent Chandra, XMM-Newton, and NuSTAR investigation of advanced mergers selected by WISE, we find dual AGN candidates in 8 out of 15 mergers, all of which show no evidence for AGN based on optical spectroscopy. Our results demonstrate that 1) optical studies miss a significant fraction of single and dual AGN in advanced mergers, and 2) mid-infrared pre-selection is extremely effective in identifying dual AGN candidates in late-stage mergers. Our multi-wavelength observations suggest that the buried AGN in these mergers are highly absorbed, with intrinsic column densities in excess of NH > 1024 cm-2, consistent with hydrodynamic simulations.

A 149 min periodicity underlies the X-ray flaring of Sgr A*

NASA Astrophysics Data System (ADS)

Leibowitz, Elia

2018-03-01

In a paper in 2017, I have shown that 39 large X-ray flares of Sgr A* that were recorded by Chandra observatory in the year 2012 are concentrated preferably around tick marks of an equi-distance grid on the time axis. The period of this grid as found in that paper is 0.1033 d. In this work I show that the effect can be found among all the large X-ray flares recorded by Chandra and XMM - Newton along 15 yr. The mid-points of all the 71 large flares recorded between years 2000 and 2014 are also tightly grouped around tick marks of a grid with this period, or more likely, 0.1032 d. This result is obtained with a confidence level of at least 3.27σ and very likely of 4.62σ. I find also a possible hint that a similar grid is underlying IR flares of the object. I suggest that the pacemaker in the occurrences of the large X-ray flares of Sgr A* is a mass of the order of a low-mass star or a small planet, in a slightly eccentric Keplerian orbit around the SMBH at the centre of the Galaxy. The radius of this orbit is about 6.6 Schwarzschild radii of the BH.

STABILITY OF GAS CLOUDS IN GALACTIC NUCLEI: AN EXTENDED VIRIAL THEOREM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xian; Cuadra, Jorge; Amaro-Seoane, Pau, E-mail: xchen@astro.puc.cl, E-mail: jcuadra@astro.puc.cl, E-mail: Pau.Amaro-Seoane@aei.mpg.de

2016-03-10

Cold gas entering the central 1–10{sup 2} pc of a galaxy fragments and condenses into clouds. The stability of the clouds determines whether they will be turned into stars or can be delivered to the central supermassive black hole (SMBH) to turn on an active galactic nucleus (AGN). The conventional criteria to assess the stability of these clouds, such as the Jeans criterion and Roche (or tidal) limit, are insufficient here, because they assume the dominance of self-gravity in binding a cloud, and neglect external agents, such as pressure and tidal forces, which are common in galactic nuclei. We formulatemore » a new scheme for judging this stability. We first revisit the conventional Virial theorem, taking into account an external pressure, to identify the correct range of masses that lead to stable clouds. We then extend the theorem to further include an external tidal field, which is equally crucial for the stability in the region of our interest—in dense star clusters, around SMBHs. We apply our extended Virial theorem to find new solutions to controversial problems, namely, the stability of the gas clumps in AGN tori, the circum-nuclear disk in the Galactic Center, and the central molecular zone of the Milky Way. The masses we derive for these structures are orders of magnitude smaller than the commonly used Virial masses (equivalent to the Jeans mass). Moreover, we prove that these clumps are stable, contrary to what one would naively deduce from the Roche (tidal) limit.« less

The close environment of Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Matt, Giorgio

2016-07-01

There are two main scientific goals of the "Close environment of SMBH" Athena Topical Panel: the determination of the BH spin distribution in the local Universe, and of the geometry of the hot X-ray emitting corona via time lag measurements. The rationale behind these goals, and how they will be achieved with Athena, will be discussed in this talk.

Do Typical Galaxies in Adolescence Already Host Growing Black Holes?

NASA Astrophysics Data System (ADS)

Trump, Jonathan

2012-10-01

This archival grism proposal achieves a 100-fold gain in high-quality {5+sigma} information for discovering which properties of adolescent {0.7

The Herschel* PEP-HERMES Luminosity Function- I. Probing the Evolution of PACS Selected Galaxies to z approx. equal to 4

NASA Technical Reports Server (NTRS)

Gruppioni, Carlotta; Pozzi, F.; Rodighiero, G.; Delvecchio, I.; Berta, S.; Pozzetti, L.; Zamorani, G.; Andreani, P.; Cimatti, A.; Ilbert, O.;

The WISSH quasars project. I. Powerful ionised outflows in hyper-luminous quasars

NASA Astrophysics Data System (ADS)

Bischetti, M.; Piconcelli, E.; Vietri, G.; Bongiorno, A.; Fiore, F.; Sani, E.; Marconi, A.; Duras, F.; Zappacosta, L.; Brusa, M.; Comastri, A.; Cresci, G.; Feruglio, C.; Giallongo, E.; La Franca, F.; Mainieri, V.; Mannucci, F.; Martocchia, S.; Ricci, F.; Schneider, R.; Testa, V.; Vignali, C.

2017-02-01

Models and observations suggest that both the power and effects of AGN feedback should be maximised in hyper-luminous (LBol > 1047 erg s-1) quasars, I.e. objects at the brightest end of the AGN luminosity function. In this paper, we present the first results of a multiwavelength observing programme, focusing on a sample of WISE/SDSS selected hyper-luminous (WISSH) broad-line quasars at z ≈ 1.5-5. The WISSH quasars project has been designed to reveal the most energetic AGN-driven outflows, estimate their occurrence at the peak of quasar activity, and extend the study of correlations between outflows and nuclear properties up to poorly investigated, extreme AGN luminosities, I.e. LBol 1047 - 1048 erg s-1. We present near-infrared, long-slit LBT/LUCI1 spectroscopy of five WISSH quasars at z ≈ 2.3 - 3.5, showing prominent [OIII] emission lines with broad (FWHM 1200-2200 km s-1) and skewed profiles. The luminosities of these broad [OIII] wings are the highest measured so far, with L[OIII]broad ≳ 5 × 1044 erg s-1, and reveal the presence of powerful ionised outflows with associated mass outflow rates Ṁ ≳ 1700M⊙ yr-1 and kinetic powers Ėkin ≳ 1045 erg s-1. Although these estimates are affected by large uncertainties because of the use of [OIII] as a tracer of ionised outflows and the very basic outflow model adopted here, these results suggest that in our hyper-luminous targets the AGN is highly efficient at pushing large amounts of ionised gas outwards. Furthermore, the mechanical outflow luminosities measured for WISSH quasars correspond to higher percentages ( 1-3%) of LBol than those derived for AGN with lower LBol. Our targets host very massive (MBH ≳ 2 × 109M⊙) black holes that are still accreting at a high rate (I.e. a factor of 0.4-3 of the Eddington limit). These findings clearly demonstrate that WISSH quasars offer the opportunity to probe the extreme end of both luminosity and supermassive black holes (SMBH) mass functions and revealing powerful ionised outflows that are able to affect the evolution of their host galaxies.

Orbital dynamics in galaxy mergers

NASA Astrophysics Data System (ADS)

Hoffman, Loren

In the favored vacuum energy + cold dark matter (ACDM) cosmology, galaxies form through a hierarchical merging process. Mergers between comparable-mass sys tems are qualitatively different from the ongoing accretion of small objects by much larger ones, in that they can radically transform the nature of the merging objects, e.g. through violent relaxation of the stars and dark matter, triggered starbursts, and quasar activity. This thesis covers two phenomena unique to major galaxy mergers: the formation of supermassive black hole (SMBH) binary and triple systems, and the transformation of the stellar orbit structure through violent relaxation, triggered gas inflow, and star formation. In a major merger, the SMBHs can spiral in and form a bound binary in less than a Hubble time. If the binary lifetime exceeds the typical time between mergers, then triple black hole (BH) systems may form. We study the statistics of close triple-SMBH encounters in galactic nuclei by computing a series of three-body orbits with physically-motivated initial conditions appropriate for giant elliptical galaxies. Our simulations include a smooth background potential consisting of a stellar bulge plus a dark matter halo, drag forces due to gravitational radiation and dynamical friction on the stars and dark matter, and a simple model of the time evolution of the inner density profile under heating and mass ejection by the SMBHs. We find that the binary pair coalesces as a result of repeated close encounters in ~85% of our runs. In about 40% of the runs the lightest BH is left wandering through the galactic halo or escapes the galaxy altogether. The triple systems typically scour out cores with mass deficits ~1-2 times their total mass. The high coalescence rate and prevalence of very high-eccentricity orbits could provide interesting signals for the future Laser Interferometer Space Antenna (LISA). Our study of remnant orbit structure involved 42 disk-disk mergers at various gas fractions, and 10 re-mergers of the 40% gas remnants. All simulations were run using a version of GADGET-2 [173] that included subresolution models of radiative cooling, star formation, and supernova and AGN feedback. The potential was frozen at the last snapshot of each simulation and the orbits of ~50,000 randomly chosen stars were integrated for ~100 dynamical times, and classified based on their Fourier spectra using the algorithm of [30]. The 40% gas remnants were found to be dominated by minor-axis tube orbits in their inner regions, whereas box orbits were the dominant orbit family in the inner parts of the dissipationless disk-disk and remnant-remnant systems. The phase space available to minor-axis tube orbits in even the 5% gas remnants was much larger than that in the dissipationless remnants, but the 5% gas remnants are not fast rotators because these orbits tend to be isotropically distributed at low gas fractions. Some of the remnants show significant minor axis rotation, due to large orientation twists in their outer parts (in the 40% gas remnants) and asymmetrically rotating major-axis tube orbits throughout the remnants (in the re-mergers).

Feeding supermassive black holes through supersonic turbulence and ballistic accretion

NASA Astrophysics Data System (ADS)

Hobbs, Alexander; Nayakshin, Sergei; Power, Chris; King, Andrew

2011-06-01

It has long been recognized that the main obstacle to the accretion of gas on to supermassive black holes (SMBHs) is a large specific angular momentum. It is feared that the gas settles in a large-scale disc, and that accretion would then proceed too inefficiently to explain the masses of the observed SMBHs. Here we point out that, while the mean angular momentum in the bulge is very likely to be large, the deviations from the mean can also be significant. Indeed, cosmological simulations show that velocity and angular momentum fields of gas flows on to galaxies are very complex. Furthermore, inside bulges the gas velocity distribution can be further randomized by the velocity kicks due to feedback from star formation. We perform hydrodynamical simulations of gaseous rotating shells infalling on to an SMBH, attempting to quantify the importance of velocity dispersion in the gas at relatively large distances from the black hole. We implement this dispersion by means of a supersonic turbulent velocity spectrum. We find that, while in the purely rotating case the circularization process leads to efficient mixing of gases with different angular momenta, resulting in a low accretion rate, the inclusion of turbulence increases this accretion rate by up to several orders of magnitude. We show that this can be understood based on the notion of 'ballistic' accretion, whereby dense filaments, created by convergent turbulent flows, travel through the ambient gas largely unaffected by hydrodynamical drag. This prevents the efficient gas mixing that was found in the simulations without turbulence, and allows a fraction of gas to impact the innermost boundary of the simulations directly. Using the ballistic approximation, we derive a simple analytical formula that captures the numerical results to within a factor of a few. Rescaling our results to astrophysical bulges, we argue that this 'ballistic' mode of accretion could provide the SMBHs with sufficient fuel without the need to channel the gas via large-scale discs or bars. We therefore argue that star formation in bulges can be a strong catalyst for SMBH accretion.

Supermassive black hole binaries and transient radio events: studies in pulsar astronomy

NASA Astrophysics Data System (ADS)

Burke-Spolaor, S.

2011-06-01

The field of pulsar astronomy encompasses a rich breadth of astrophysical topics. The research in this thesis contributes to two particular subjects of pulsar astronomy: gravitational wave science, and identifying celestial sources of pulsed radio emission. We first investigated the detection of supermassive black hole (SMBH) binaries, which are the brightest expected source of gravitational waves for pulsar timing. We considered whether two electromagnetic SMBH tracers, velocity-resolved emission lines in active nuclei, and radio galactic nuclei with spatially-resolved, flat-spectrum cores, can reveal systems emitting gravitational waves in the pulsar timing band. We found that there are systems which may in principle be simultaneously detectable by both an electromagnetic signature and gravitational emission, however the probability of actually identifying such a system is low (they will represent much less than 1% of a randomly selected galactic nucleus sample). This study accents the fact that electromagnetic indicators may be used to explore binary populations down to the 'stalling radii' at which binary inspiral evolution may stall indefinitely at radii exceeding those which produce gravitational radiation in the pulsar timing band. We then performed a search for binary SMBH holes in archival Very Long Baseline Interferometry data for 3114 radio-luminous active galactic nuclei. One source was detected as a double nucleus. This result is interpreted in terms of post-merger timescales for SMBH centralisation, implications for 'stalling', and the relationship of radio activity in nuclei to mergers. Our analysis suggested that binary pair evolution of SMBHs (both of masses >108M circled bullet) spends less than 500Myr in progression from the merging of galactic stellar cores to within the purported stalling radius for SMBH pairs, giving no evidence for an excess of stalled binary systems at small separations. Circumstantial evidence showed that the relative state of radio emission between paired SMBHs is correlated within orbital separations of 2.5 kpc. We then searched for transient radio events in two archival pulsar surveys, and in the new High Time Resolution Universe (HTRU) Survey. We present the methodology employed for these searches, noting the novel addition of methods for single-event recognition, automatic interference mitigation, and data inspection. 27 new neutron stars were discovered. We discuss the relationship between "rotating radio transient" (RRAT) and pulsar populations, finding that the Galactic z-distribution of RRATs closely resembles the distribution of pulsars, and where measurable, RRAT pulse widths are similar to individual pulses from pulsars of similar period, implying a similar beaming fraction. We postulate that many RRATs may simply represent a tail of extreme-nulling pulsars that are "on" for less than a pulse period; this is supported by the fact that nulling pulsars and single-pulse discoveries exhibit a continuous distribution across null/activity timescales and nulling fractions. We found a drop-off in objects with emissivity cycles longer than 300 seconds at intermediate and low nulling fractions which is not readily explained by selection effects. The HTRU deep low-latitude survey (70-min. pointings at galactic latitudes |b| < 3.5 degrees and longitudes -80 degrees < l < 30 degrees) will be capable of exploring whether this deficit is natural or an effect of selection. The intriguing object PSR J0941-39 may represent an evolutionary link between nulling populations; discovered as an sparsely-pulsing RRAT, in follow-up observations it often appeared as a bright (10 mJy) pulsar with a low nulling fraction. It is therefore apparent that a neutron star can oscillate between nulling levels, much like mode-changing pulsars. Crucially, the RRAT and pulsar-mode emission sites are coincident, implying that the two emission mechanisms are linked. We estimate that the full HTRU survey will roughly quadruple the known deep-nulling pulsar population, allowing statistical studies to be made of extreme-nulling populations. HTRU's low-latitude survey will explore the neutron star population with null lengths lasting up to several hours. We lastly reported the discovery of 16 pulses, the bulk of which exhibit a frequency sweep with a shape and magnitude resembling the "Lorimer Burst" (Lorimer et al. 2007), which three years ago was reported as a solitary radio burst that was thought to be the first discovery of a rare, impulsive event of unknown extragalactic origin. However, the new events were of clearly terrestrial origin, with properties unlike any known sources of terrestrial broad-band radio emission. The new detections cast doubt on the extragalactic interpretation of the original burst, and call for further sophistication in radio-pulse survey techniques to identify the origin of the anomalous terrestrial signals and definitively distinguish future extragalactic pulse detections from local signals. The ambiguous origin of these seemingly dispersed, swept-frequency signals suggest that radio-pulse searches using multiple detectors will be the only experiments able to provide definitive information about the origin of new swept-frequency radio burst detections. Finally, we summarise our major findings and suggest future work which would expand on the work in this thesis.

Compton Thick AGN in the XMM-COSMOS field

NASA Astrophysics Data System (ADS)

Lanzuisi, G.; Perna, M.; Delvecchio, I.; Berta, S.; Brusa, M.; Gruppioni, C.; Comastri, A.

2016-06-01

I will present results we published in two recent papers (Lanzuisi et al. 2015, A&A 573A 137, Lanzuisi et al. 2015, A≈A 578A 120) on the properties of X-ray selected Compton Thick (CT, NH>10^{24} cm^{-2}) AGN, in the XMM-COSMOS survey. We exploited the rich multi-wavelength dataset available in this field, to show that CT AGN tend to harbor smaller, rapidly growing SMBH with respect to unobscured AGN, and have a higher chance of being hosted by star-forming, merging and post-merger systems. We also demonstrated the detectability of even more heavily obscured AGN (NH>10^{25} cm^{-2}), thanks to a truly multi-wavelength approach in the same field, and to the unrivaled XMM sensitivity. The extreme source detected in this way shows strong evidences of ongoing powerful AGN feedback, detected as blue-shifted wings of high ionization optical emission lines such as [NeV] and [FeVII], as well as of the [OIII] emission line. The results obtained from these works point toward a scenario in which highly obscured AGN occupy a peculiar place in the galaxy-AGN co-evolution process, in which both the host and the SMBH rapidly evolve toward the local relations.

High-Resolution Observations of a Binary Black Hole Candidate

NASA Astrophysics Data System (ADS)

Tsai, Chao-Wei; Phillips, Chris; Norris, Ray; Jarrett, Thomas; Emonts, Bjorn; Cluver, Michelle; Eisenhardt, Peter; Stern, Daniel; Assef, Roberto

2012-10-01

We propose a 12-hour 2.3 GHz continuum Long Baseline Array (LBA) observation of WISE J2332-5056, a newly discovered supermassive black hole (SMBH) merger candidate that is located in the nearby universe (z = 0.3447). Our recently acquired 9 GHz ATCA map shows unusual radio morphology: a one-sided, smaller (and likely younger) FR-I jet perpendicular to a larger, Doppler-boosted FR-II jet. Follow-up Gemini-S/GMOS spectroscopy of this WISE-selected radio galaxy reveals broad emission lines blue-shifted by > 3,500 km/s with respect to the narrow lines and host galaxy, hallmarks of a dual AGN system. Combined, the optical spectroscopy and radio morphology of this object are strongly suggestive of a black hole merger system. Even in the local universe these systems are extremely difficult to identify; yet the process of supermassive blackhole growth is vital toward understanding galaxy evolution from the early to the current universe. Moreover, nearby merging SMBHs may serve as outstanding targets for gravitational wave studies. The proposed high resolution LBA map, reaching 50 pc resolution at the source redshift will allow us to investigate the SMBH merger scenario hypothesis.

Probing the Hot and Energetic Universe: X-rays and Astrophysics

NASA Astrophysics Data System (ADS)

Bautz, Marshall; Kraft, Ralph

2016-03-01

X-ray observations are a cornerstone of our understanding of the formation and evolution of structure in the Universe, from solar-system-sized supermassive black holes (SMBH) to the largest galaxy clusters. At the most basic level, a significant fraction of the energy output in the Universe is in X-rays, and much of this emission traces the response of baryonic matter to the inexorable, gravity-driven growth of cosmic structure. At present, for example, half or more of the baryons in the Universe reside in a hot (>1 MK) X-ray-emitting phase. We discuss some of the remarkable progress that has been made in understanding the broad outlines of these processes with the current generation of X-ray observatories. We summarize the potential of recently launched and forthcoming X-ray observatories to track the development of large-scale cosmic structure and to understand the physics linking the growth of SMBH with that of the (many orders of magnitude larger) galaxies and clusters which host them. We briefly review nearer-term prospects for smaller, focussed missions, including one that will soon exploit pulsating X-ray emission from neutron stars to probe the equation of state of matter at nuclear densities.

Clustering of galaxies around AGNs in the HSC Wide survey

NASA Astrophysics Data System (ADS)

Shirasaki, Yuji; Akiyama, Masayuki; Nagao, Tohru; Toba, Yoshiki; He, Wanqiu; Ohishi, Masatoshi; Mizumoto, Yoshihiko; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Usuda, Tomonori

2018-01-01

We have measured the clustering of galaxies around active galactic nuclei (AGNs) for which single-epoch virial masses of the super-massive black hole (SMBH) are available to investigate the relation between the large-scale environment of AGNs and the evolution of SMBHs. The AGN samples used in this work were derived from the Sloan Digital Sky Survey (SDSS) observations and the galaxy samples were from the 240 deg2 S15b data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). The investigated redshift range is 0.6-3.0, and the masses of the SMBHs lie in the range 107.5-1010 M⊙. The absolute magnitude of the galaxy samples reaches to Mλ310 ˜ -18 at rest-frame wavelength 310 nm for the low-redshift end of the samples. More than 70% of the galaxies in the analysis are blue. We found a significant dependence of the cross-correlation length on redshift, which primarily reflects the brightness-dependence of the galaxy clustering. At the lowest redshifts the cross-correlation length increases from 7 h-1 Mpc around Mλ310 = -19 mag to >10 h-1 Mpc beyond Mλ310 = -20 mag. No significant dependence of the cross-correlation length on BH mass was found for whole galaxy samples dominated by blue galaxies, while there was an indication of BH mass dependence in the cross-correlation with red galaxies. These results provides a picture of the environment of AGNs studied in this paper being enriched with blue star-forming galaxies, and a fraction of the galaxies are evolving into red galaxies along with the evolution of SMBHs in that system.

Unseen Progenitors of Luminous High-z Quasars in the R h = ct Universe

NASA Astrophysics Data System (ADS)

Fatuzzo, Marco; Melia, Fulvio

2017-09-01

Quasars at high redshift provide direct information on the mass growth of supermassive black holes (SMBHs) and, in turn, yield important clues about how the universe evolved since the first (Pop III) stars started forming. Yet even basic questions regarding the seeds of these objects and their growth mechanism remain unanswered. The anticipated launch of eROSITA and ATHENA is expected to facilitate observations of high-redshift quasars needed to resolve these issues. In this paper, we compare accretion-based SMBH growth in the concordance ΛCDM model with that in the alternative Friedmann-Robertson-Walker cosmology known as the R h = ct universe. Previous work has shown that the timeline predicted by the latter can account for the origin and growth of the ≳109 M ⊙ highest redshift quasars better than that of the standard model. Here, we significantly advance this comparison by determining the soft X-ray flux that would be observed for Eddington-limited accretion growth as a function of redshift in both cosmologies. Our results indicate that a clear difference emerges between the two in terms of the number of detectable quasars at redshift z ≳ 7, raising the expectation that the next decade will provide the observational data needed to discriminate between these two models based on the number of detected high-redshift quasar progenitors. For example, while the upcoming ATHENA mission is expected to detect ˜0.16 (I.e., essentially zero) quasars at z ˜ 7 in R h = ct, it should detect ˜160 in ΛCDM—a quantitatively compelling difference.

Bondi or not Bondi: the impact of resolution on accretion and drag force modelling for supermassive black holes

NASA Astrophysics Data System (ADS)

Beckmann, R. S.; Slyz, A.; Devriendt, J.

2018-07-01

Whilst in galaxy-size simulations, supermassive black holes (SMBHs) are entirely handled by sub-grid algorithms, computational power now allows the accretion radius of such objects to be resolved in smaller scale simulations. In this paper, we investigate the impact of resolution on two commonly used SMBH sub-grid algorithms; the Bondi-Hoyle-Lyttleton (BHL) formula for accretion on to a point mass, and the related estimate of the drag force exerted on to a point mass by a gaseous medium. We find that when the accretion region around the black hole scales with resolution, and the BHL formula is evaluated using local mass-averaged quantities, the accretion algorithm smoothly transitions from the analytic BHL formula (at low resolution) to a supply-limited accretion scheme (at high resolution). However, when a similar procedure is employed to estimate the drag force, it can lead to significant errors in its magnitude, and/or apply this force in the wrong direction in highly resolved simulations. At high Mach numbers and for small accretors, we also find evidence of the advective-acoustic instability operating in the adiabatic case, and of an instability developing around the wake's stagnation point in the quasi-isothermal case. Moreover, at very high resolution, and Mach numbers above M_∞ ≥ 3, the flow behind the accretion bow shock becomes entirely dominated by these instabilities. As a result, accretion rates on to the black hole drop by about an order of magnitude in the adiabatic case, compared to the analytic BHL formula.

Gas Accretion onto a Supermassive Black Hole: A Step to Model AGN Feedback

NASA Astrophysics Data System (ADS)

Nagamine, K.; Barai, P.; Proga, D.

2012-08-01

We study gas accretion onto a supermassive black hole (SMBH) using the 3D SPH code GADGET-3 on scales of 0.1-200 pc. First we test our code with the spherically symmetric, adiabatic Bondi accretion problem. We find that our simulation can reproduce the expected Bondi accretion flow very well for a limited amount of time until the effect of the outer boundary starts to be visible. We also find artificial heating of gas near the inner accretion boundary due to the artificial viscosity of SPH. Second, we implement radiative cooling and heating due to X-rays, and examine the impact of thermal feedback by the central X-ray source. The accretion flow roughly follows the Bondi solution for low central X-ray luminosities; however, the flow starts to exhibit non-spherical fragmentation due to the thermal instability for a certain range of central LX, and a strong overall outflow develops for greater LX. The cold gas develops filamentary structures that fall into the central SMBH, whereas the hot gas tries to escape through the channels in between the cold filaments. Such fragmentation of accreting gas can assist in the formation of clouds around AGN, induce star-formation, and contribute to the observed variability of narrow-line regions.

The Advanced X-ray Imaging Satellite (AXIS)

NASA Astrophysics Data System (ADS)

Reynolds, Christopher S.; Mushotzky, Richard

2017-08-01

The Advanced X-ray Imaging Satellite (AXIS) will follow in the footsteps of the spectacularly successful Chandra X-ray Observatory with similar or higher angular resolution and an order of magnitude more collecting area in the 0.3-10keV band. These capabilities will enable major advances in many of the most active areas of astrophysics, including (i) mapping event horizon scale structure in AGN accretion disks and the determination of supermassive black hole (SMBH) spins through monitoring of gravitationally-microlensed quasars; (ii) dramatically deepening our understanding of AGN feedback in galaxies and galaxy clusters out to high-z through the direct imaging of AGN winds and the interaction of jets with the hot interstellar/intracluster medium; (iii) understanding the fueling of AGN by probing hot flows inside of the SMBH sphere of influence; (iv) obtaining geometric distance measurements using dust scattering halos. With a nominal 2028 launch, AXIS will be enormously synergistic with LSST, ALMA, WFIRST and ATHENA, and will be a valuable precursor to Lynx. AXIS is enabled by breakthroughs in the construction of light-weight X-ray optics from mono-crystalline silicon blocks, building on recent developments in the semiconductor industry. Here, we describe the straw-man concept for AXIS, some of the high profile science that this observatory will address, and how you can become involved.

NGC 5195 IN M51: FEEDBACK “BURPS” AFTER A MASSIVE MEAL?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlegel, E. M.; Jones, C.; Machacek, M.

2016-06-01

We describe a double-arc-like X-ray structure lying ∼15″–30″ (∼0.8–1.7 kpc) south of the NGC 5195 nucleus, visible in the merged exposures of long Chandra pointings of M51. The curvature and orientation of the arcs argues for a nuclear origin. The arcs are radially separated by ∼15″ (∼1 kpc), but are rotated relative to each other by ∼30°. From an archival image, we find a slender H α -emitting region just outside the outer edge of the outer X-ray arc, suggesting that the X-ray-emitting gas plowed up and displaced the H α -emitting material from the galaxy core. Star formation maymore » have commenced in that arc. H α emission is present at the inner arc, but appears more complex in structure. In contrast to an explosion expected to be azimuthally symmetric, the X-ray arcs suggest a focused outflow. We interpret the arcs as episodic outbursts from the central super-massive black hole (SMBH). We conclude that NGC 5195 represents the nearest galaxy exhibiting on-going, large-scale outflows of gas, in particular, two episodes of a focused outburst of the SMBH. The arcs represent a clear demonstration of feedback.« less

Tidal Disruption Events Prefer Unusual Host Galaxies

NASA Astrophysics Data System (ADS)

Arcavi, Iair; French, K. Decker; Zabludoff, Ann I.

2016-06-01

A star passing close to a supermassive black hole (SMBH) can be torn apart in a Tidal Disruption Events (TDE). TDEs that are accompanied by observable flares are now being discovered in transient surveys and are revealing the presence and the properties of otherwise-quiescent SMBHs. Recently, it was discovered that TDEs show a strong preference for rare post-starburst galaxies, (i.e. galaxies that have undergone intense star formation but are no longer forming stars today). We quantify this preference and find that TDEs are approximately 30-200 times more likely to occur in post-starburst hosts (compared to the general SDSS galaxy population), with the enhancement factor depending on the star formation history of the galaxy. This surprising host-galaxy preference connects the until-now disparate TDE subclasses of UV/optical-dominated TDEs and X-ray-dominated TDEs, and serves as the basis for TDE-targeted transient surveys. Post-starburst galaxies may be post-mergers, with binary SMBH systems that are still spiraling in. Such systems could enhance the TDE rate, but it is not yet clear if models can quantitatively reproduce the observed enhancement. Alternative explanations for enhanced TDE rate in post-starbursts include non-spherical post-merger central potentials and enhanced rates of giant stars.

Understanding the Host Galaxies of Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

Stone, Nicholas; Generozov, Aleksey; Vasiliev, Eugene; Metzger, Brian

2018-01-01

Recent observations suggest that stellar tidal disruption events (TDE) are strongly overrepresented in rare, post-starburst galaxies. Several dynamical mechanisms have been proposed to elevate their TDE rates, ranging from central stellar overdensities to the presence of supermassive black hole (SMBH) binaries. These, and other, dynamical hypotheses can be disentangled by comparing observations to theoretical predictions for the TDE delay time distribution (DTD). We show that SMBH binaries are a less plausible solution for the post-starburst preference, as they can only reproduce the observed DTD with extensive fine-tuning. The overdensity hypothesis produces a reasonable match to the observed DTD (based on the limited data currently available), provided that the initial stellar density profile created during the starburst, ρ(r), is exceptional in both steepness and normalization. In particular, explaining the post-starburst preference requires ρ∝r‑γ with γ>2.5, i.e. much steeper than the classic Bahcall-Wolf equilibrium profile of γ=7/4. Radial velocity anisotropies also represent a promising explanation, provided that initial anisotropy parameters of β0≈0.5 are sustainable against the radial orbit instability. As the sample of TDEs with well-studied host galaxies grows, the DTD will become a powerful tool for constraining the exceptional dynamical properties of post-starburst galactic nuclei.

Identification of 1.4 Million Active Galactic Nuclei In the Mid-Infrared Using WISE Data

DTIC Science & Technology

2015-11-01

galaxies – infrared: stars – galaxies : active – quasars: general Supporting material: machine-readable table 1. INTRODUCTION The International Celestial...AGN-dominated galaxies , optical emission is thought to originate from the compact accretion disk surrounding the supermassive black hole (SMBH), while... galaxies , an optical centroid can be shifted relative to the radio position because of contamination from the host galaxy . Depending on the distance to

Unseen Progenitors of Luminous High- z Quasars in the R {sub h} = ct Universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fatuzzo, Marco; Melia, Fulvio, E-mail: fatuzzo@xavier.edu, E-mail: fmelia@email.arizona.edu

Quasars at high redshift provide direct information on the mass growth of supermassive black holes (SMBHs) and, in turn, yield important clues about how the universe evolved since the first (Pop III) stars started forming. Yet even basic questions regarding the seeds of these objects and their growth mechanism remain unanswered. The anticipated launch of eROSITA and ATHENA is expected to facilitate observations of high-redshift quasars needed to resolve these issues. In this paper, we compare accretion-based SMBH growth in the concordance ΛCDM model with that in the alternative Friedmann–Robertson–Walker cosmology known as the R {sub h} = ct universe.more » Previous work has shown that the timeline predicted by the latter can account for the origin and growth of the ≳10{sup 9} M {sub ⊙} highest redshift quasars better than that of the standard model. Here, we significantly advance this comparison by determining the soft X-ray flux that would be observed for Eddington-limited accretion growth as a function of redshift in both cosmologies. Our results indicate that a clear difference emerges between the two in terms of the number of detectable quasars at redshift z ≳ 7, raising the expectation that the next decade will provide the observational data needed to discriminate between these two models based on the number of detected high-redshift quasar progenitors. For example, while the upcoming ATHENA mission is expected to detect ∼0.16 (i.e., essentially zero) quasars at z ∼ 7 in R {sub h} = ct , it should detect ∼160 in ΛCDM—a quantitatively compelling difference.« less

Ionized and Neutral Outflows in the QUEST QSOs

NASA Astrophysics Data System (ADS)

Veilleux, Sylvain

2011-10-01

The role of galactic winds in gas-rich mergers is of crucial importance to understand galaxy and SMBH evolution. In recent months, our group has had three major scientific breakthroughs in this area: {1} The discovery with Herschel of massive molecular {OH-absorbing} outflows in several ULIRGs, including the nearest quasar, Mrk 231. {2} The independent discovery from mm-wave interferometric observations in the same object of a spatially resolved molecular {CO-emitting} wind with estimated mass outflow rate 3x larger than the star formation rate and spatially coincident with blueshifted neutral {Na ID-absorbing} gas in optical long-slit spectra. {3} The unambiguous determination from recent Gemini/IFU observations that the Na ID outflow in this object is wide-angle, thus driven by a QSO wind rather than a jet. This powerful outflow may be the long-sought "smoking gun" of quasar mechanical feedback purported to transform gas-rich mergers. However, our Herschel survey excludes all FIR-faint {UV-bright} "classic" QSOs by necessity. So here we propose a complementary FUV absorption-line survey of all FIR-bright -and- FIR-faint QSOs from the same parent sample. New {19 targets} and archival {11} spectra will be used to study, for the first time, the gaseous environments of QSOs as a function of host properties and age across the merger sequence ULIRG -> QSO. These data will allow us to distinguish between ionized & neutral quasar-driven outflows, starburst-driven winds, and tidal debris around the mergers. They will also be uniquely suited for a shallow but broad study of the warm & warm-hot intergalactic media, complementary to on-going surveys that are deeper but narrower.

CHANDRA X-RAY AND HUBBLE SPACE TELESCOPE IMAGING OF OPTICALLY SELECTED KILOPARSEC-SCALE BINARY ACTIVE GALACTIC NUCLEI. II. HOST GALAXY MORPHOLOGY AND AGN ACTIVITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shangguan, Jinyi; Ho, Luis C.; Liu, Xin

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W ( U -band) and F105W ( Y -band) images taken by the Wide Fieldmore » Camera 3 on board the Hubble Space Telescope . Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U − Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers.« less

The Spectral Energy Distribution of the Hyperluminous, Hot Dust-obscured Galaxy W2246–0526

NASA Astrophysics Data System (ADS)

Fan, Lulu; Gao, Ying; Knudsen, Kirsten K.; Shu, Xinwen

2018-02-01

Hot dust-obscured galaxies (Hot DOGs) are a luminous, dust-obscured population recently discovered in the WISE All-Sky survey. Multiwavelength follow-up observations suggest that they are mainly powered by accreting supermassive black holes (SMBHs), lying in dense environments, and being in the transition phase between extreme starburst and UV-bright quasars. Therefore, they are good candidates for studying the interplay between SMBHs, star formation, and environment. W2246‑0526 (hereafter, W2246), a Hot DOG at z ∼ 4.6, has been taken as the most luminous galaxy known in the universe. Revealed by the multiwavelength images, the previous Herschel SPIRE photometry of W2246 is contaminated by a foreground galaxy (W2246f), resulting in an overestimation of its total IR luminosity by a factor of about two. We perform the rest-frame UV/optical-to-far-IR spectral energy distribution (SED) analysis with SED3FIT and re-estimate its physical properties. The derived stellar mass {M}\\star =4.3× {10}11 {M}ȯ makes it among the most massive galaxies with spectroscopic redshift z > 4.5. Its structure is extremely compact and requires an effective mechanism to puff-up. Most of (>95%) its IR luminosity is from AGN torus emission, revealing the rapid growth of the central SMBH. We also predict that W2246 may have a significant molecular gas reservoir based on the dust mass estimation.

RESOLVING THE GEOMETRY OF THE INNERMOST RELATIVISTIC JETS IN ACTIVE GALACTIC NUCLEI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Algaba, J. C.; Lee, S. S.; Nakamura, M.

2017-01-01

In the current paradigm, it is believed that the compact VLBI radio core of radio-loud active galactic nuclei (AGNs) represents the innermost upstream regions of relativistic outflows. These regions of AGN jets have generally been modeled by a conical outflow with a roughly constant opening angle and flow speed. Nonetheless, some works suggest that a parabolic geometry would be more appropriate to fit the high energy spectral distribution properties and it has been recently found that, at least in some nearby radio galaxies, the geometry of the innermost regions of the jet is parabolic. We compile here multi-frequency core sizes of archivalmore » data to investigate the typically unresolved upstream regions of the jet geometry of a sample of 56 radio-loud AGNs. Data combined from the sources considered here are not consistent with the classic picture of a conical jet starting in the vicinity of the super-massive black hole (SMBH), and may exclude a pure parabolic outflow solution, but rather suggest an intermediate solution with quasi-parabolic streams, which are frequently seen in numerical simulations. Inspection of the large opening angles near the SMBH and the range of the Lorentz factors derived from our results support our analyses. Our result suggests that the conical jet paradigm in AGNs needs to be re-examined by millimeter/sub-millimeter VLBI observations.« less

Hyperaccretion during Tidal Disruption Events: Weakly Bound Debris Envelopes and Jets

NASA Astrophysics Data System (ADS)

Coughlin, Eric R.; Begelman, Mitchell C.

2014-02-01

After the destruction of the star during a tidal disruption event (TDE), the cataclysmic encounter between a star and the supermassive black hole (SMBH) of a galaxy, approximately half of the original stellar debris falls back onto the hole at a rate that can initially exceed the Eddington limit by orders of magnitude. We argue that the angular momentum of this matter is too low to allow it to attain a disk-like configuration with accretion proceeding at a mildly super-Eddington rate, the excess energy being carried away by a combination of radiative losses and radially distributed winds. Instead, we propose that the infalling gas traps accretion energy until it inflates into a weakly bound, quasi-spherical structure with gas extending nearly to the poles. We study the structure and evolution of such "zero-Bernoulli accretion" flows as a model for the super-Eddington phase of TDEs. We argue that such flows cannot stop extremely super-Eddington accretion from occurring, and that once the envelope is maximally inflated, any excess accretion energy escapes through the poles in the form of powerful jets. We compare the predictions of our model to Swift J1644+57, the putative super-Eddington TDE, and show that it can qualitatively reproduce some of its observed features. Similar models, including self-gravity, could be applicable to gamma-ray bursts from collapsars and the growth of SMBH seeds inside quasi-stars.

How do accretion discs break?

NASA Astrophysics Data System (ADS)

Dogan, Suzan

2016-07-01

Accretion discs are common in binary systems, and they are often found to be misaligned with respect to the binary orbit. The gravitational torque from a companion induces nodal precession in misaligned disc orbits. In this study, we first calculate whether this precession is strong enough to overcome the internal disc torques communicating angular momentum. We compare the disc precession torque with the disc viscous torque to determine whether the disc should warp or break. For typical parameters precession wins: the disc breaks into distinct planes that precess effectively independently. To check our analytical findings, we perform 3D hydrodynamical numerical simulations using the PHANTOM smoothed particle hydrodynamics code, and confirm that disc breaking is widespread and enhances accretion on to the central object. For some inclinations, the disc goes through strong Kozai cycles. Disc breaking promotes markedly enhanced and variable accretion and potentially produces high-energy particles or radiation through shocks. This would have significant implications for all binary systems: e.g. accretion outbursts in X-ray binaries and fuelling supermassive black hole (SMBH) binaries. The behaviour we have discussed in this work is relevant to a variety of astrophysical systems, for example X-ray binaries, where the disc plane may be tilted by radiation warping, SMBH binaries, where accretion of misaligned gas can create effectively random inclinations and protostellar binaries, where a disc may be misaligned by a variety of effects such as binary capture/exchange, accretion after binary formation.

Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-01-01

Three-dimensional hydrodynamic simulations, covering the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass 108 M⊙, with detailed radiative cooling processes, are performed. Generically found is the existence of a significant amount of shock heated, high temperature (≥108 K) coronal gas in the inner (≤104 rsch) region. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

C IV broad absorption line variability in QSO spectra from SDSS surveys

NASA Astrophysics Data System (ADS)

De Cicco, Demetra; Brandt, William N.; Grier, Catherine J.; Paolillo, Maurizio

2017-12-01

Broad absorption lines (BALs) in the spectra of quasi-stellar objects (QSOs) are thought to arise from outflowing winds along our line of sight; winds, in turn, are thought to originate from the accretion disk, in the very surroundings of the central supermassive black hole (SMBH), and they likely affect the accretion process onto the SMBH, as well as galaxy evolution. BALs can exhibit variability on timescales typically ranging from months to years. We analyze such variability and, in particular, BAL disappearance, with the aim of investigating QSO physics and structure. We search for disappearing C IV BALs in the spectra of 1319 QSOs from different programs from the Sloan Digital Sky Survey (SDSS); the analyzed time span covers 0.28-4.9 yr (rest frame), and the source redshifts are in the range 1.68-4.27. This is to date the largest sample ever used for such a study. We find 67 sources (5.1_{-0.6}^{+0.7}% of the sample) with 73 disappearing BALs in total (3.9_{-0.5}^{+0.5}% of the total number of C IV BALs detected; some sources have more than one BAL that disappears). We compare the sample of disappearing BALs to the whole sample of BALs, and investigate the correlation in the variability of multiple troughs in the same spectrum. We also derive estimates of the average lifetime of a BAL trough and of the BAL phase along our line of sight.

BOOSTED TIDAL DISRUPTION BY MASSIVE BLACK HOLE BINARIES DURING GALAXY MERGERS FROM THE VIEW OF N -BODY SIMULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Shuo; Berczik, Peter; Spurzem, Rainer

Supermassive black hole binaries (SMBHBs) are productions of the hierarchical galaxy formation model. There are many close connections between a central SMBH and its host galaxy because the former plays very important roles on galaxy formation and evolution. For this reason, the evolution of SMBHBs in merging galaxies is a fundamental challenge. Since there are many discussions about SMBHB evolution in a gas-rich environment, we focus on the quiescent galaxy, using tidal disruption (TD) as a diagnostic tool. Our study is based on a series of numerical, large particle number, direct N -body simulations for dry major mergers. According tomore » the simulation results, the evolution can be divided into three phases. In phase I, the TD rate for two well separated SMBHs in a merging system is similar to that for a single SMBH in an isolated galaxy. After two SMBHs approach close enough to form a bound binary in phase II, the disruption rate can be enhanced by ∼2 orders of magnitude within a short time. This “boosted” disruption stage finishes after the SMBHB evolves to a compact binary system in phase III, corresponding to a reduction in disruption rate back to a level of a few times higher than in phase I. We also discuss how to correctly extrapolate our N -body simulation results to reality, and the implications of our results to observations.« less

AXIS - Advanced X-ray Imaging Sarellite

NASA Astrophysics Data System (ADS)

Loewenstein, Michael; AXIS Team

2018-01-01

We present an overview of the Advanced X-ray Imaging Satellite (AXIS), a probe mission concept under study to the 2020 Decadal survey. AXIS follows in the footsteps of the spectacularly successful Chandra X-ray Observatory with similar or higher angular resolution and an order of magnitude more collecting area in the 0.3-10 keV band over a 15' field of view. These capabilities are designed to attain a wide range of science goals such as (i) measuring the event horizon scale structure in AGN accretion disks and the spin of supermassive black holes through monitoring of gravitationally microlensed quasars; (ii) understanding AGN and starburst feedback in galaxies and galaxy clusters through direct imaging of winds and interaction of jets and via spatially resolved imaging of galaxies at high-z; (iii) probing the fueling of AGN by resolving the SMBH sphere of influence in nearby galaxies; (iv) investigating hierarchical structure formation and the SMBH merger rate through measurement of the occurrence rate of dual AGN and occupation fraction of SMBHs; (v) advancing SNR physics and galaxy ecology through large detailed samples of SNR in nearby galaxies; (vi) measuring the Cosmic Web through its connection to cluster outskirts. With a nominal 2028 launch, AXIS benefits from natural synergies with LSST, ELTs, ALMA, WFIRST and ATHENA, and will be a valuable precursor to Lynx. AXIS utilizes breakthroughs in the construction of light-weight X-ray optics from mono-crystalline silicon blocks, and developments in the fabrication of large format, small pixel, high readout detectors.

A Method for Locating a High-energy Dissipation Region in a Blazar

NASA Astrophysics Data System (ADS)

Yan, Dahai; Wu, Qingwen; Fan, Xuliang; Wang, Jiancheng; Zhang, Li

2018-06-01

The production site of gamma-rays in a blazar jet is an unresolved problem. We present a method to locate a gamma-ray emission region in the framework of a one-zone emission model. From measurements of the core-shift effect, the relation between the magnetic field strengths (B‧) in the radio cores of the jet and the distances (R) of these radio cores from the central supermassive black hole (SMBH) can be inferred. Therefore, once the magnetic field strength in the gamma-ray emission region ({B}diss}{\\prime }) is obtained, one can use the relation of B‧–R to derive the distance (R diss) of the gamma-ray emission region from the SMBH. Here, we evaluate the lower limit of {B}diss}{\\prime } by using the criteria that the optical variability timescale t var should be longer than or equal to the synchrotron radiation cooling timescale of the electrons that emit optical photons. We test the method with the observations of PSK 1510-089 and BL Lacertae, and derive {R}diss}< 0.15{δ }{{D}}1/3{(1+A)}2/3 pc for PSK 1510-089 with t var ∼ a few hours and {R}diss}< 0.003{δ }{{D}}1/3{(1+A)}2/3 pc for BL Lacertae with t var ∼ a few minutes. Here, δ D is the Doppler factor and A is the Compton dominance (i.e., the ratio of the Compton to the synchrotron peak luminosities).

Coevolution of Supermassive Black Holes and Galaxies across cosmic times

NASA Astrophysics Data System (ADS)

Aversa, Rossella

2015-10-01

Understanding how supermassive black holes (SMBHs) and galaxies coevolve within their host dark matter (DM) halos is a fundamental issue in astrophysics. This thesis is aimed to shed light on this topic. As a first step, we employ the recent wide samples of far-infrared (FIR) selected galaxies followed-up in X-rays, and of X-ray/optically selected active galactic nuclei (AGNs) followed-up in the FIR band, along with the classic data on AGN and stellar luminosity functions at redshift z & 1.5, to probe different stages in the coevolution of SMBHs and their host galaxies. The results of this analysis indicate the following scenario: (i) the star formation in the host galaxy proceeds within a heavily dust-enshrouded medium, at an almost constant rate, over a timescale . 0.5 - 1 Gyr, and then abruptly declines due to quasar feedback; (ii) part of the interstellar medium loses angular momentum, reaches the circum-nuclear regions, at a rate proportional to the star formation, and is temporarily stored into a massive reservoir/proto-torus, wherefrom it can be promptly accreted; (iii) the black hole (BH) grows by accretion in a self-regulated regime with radiative power that can slightly exceed the Eddington limit (L/LEdd . 4), particularly at the highest redshifts; (iv) the ensuing energy feedback from massive BHs, at its maximum, exceeds the stellar one and removes the interstellar gas, thus stopping the star formation and the fueling of the reservoir; (v) afterwards, if the gas stored in the reservoir is enough, a phase of supply-limited accretion follows, whose rate exponentially declines with a timescale of ∼3 e-folding times. We also discuss how the detailed properties and the specific evolution of the reservoir can be investigated via coordinated, high-resolution observations of starforming, strongly lensed galaxies in the (sub-)mm band with ALMA, and in the X-ray band with Chandra and the next generation of X-ray instruments. According to the scenario described above, we further investigate the coevolution of galaxies and hosted SMBHs throughout the history of the Universe by applying a statistical, model-independent approach, based on the continuity equation and the abundance matching technique. We present analytical solutions of the continuity equation without source term, to reconstruct the SMBH mass function (BHMF) at different redshifts iii from the AGN luminosity function. Such an approach includes the physically-motivated AGN lightcurves we have tested and discussed, which describe the evolution of both the Eddington ratio and the radiative efficiency from slim- to thin-disc conditions. We nicely reproduce the local estimates of the BHMF, the AGN duty cycle as a function of mass and redshift, along with the Eddington ratio function and the fraction of galaxies hosting an AGN with given Eddington ratio. We employ the same approach to reconstruct the observed stellar mass function (SMF) at different redshifts, starting from the ultraviolet (UV) and FIR luminosity functions associated to star formation in galaxies. Our results imply that the buildup of stars and BHs in galaxies occurs via in-situ processes, with dry mergers playing a marginal role, at least for stellar masses . 3×10^11 M⊙ and BH masses . 10^9 M⊙, where the statistical data are more secure and less biased by systematic errors. In addition, we develop an improved abundance matching technique, to link the stellar and BH content of galaxies to the gravitationally dominant DM component. The resulting relationships constitute a testbed for galaxy evolution models, highlighting the complementary role of stellar and AGN feedback in the star formation process. They may also be operationally implemented in numerical simulations to populate DM halos, or to gauge subgrid physics. Moreover, they can be exploited to investigate the galaxy/AGN clustering as a function of redshift, stellar/BH mass, and/or luminosity. The clustering properties of BHs and galaxies are found to be in full agreement with current observations, so further validating our results from the continuity equation. Finally, our analysis highlights that: (i) the fraction of AGNs observed in the slim-disc regime, where anyway most of the BH mass is accreted, increases with redshift; (ii) already at z & 6, a substantial amount of dust must have formed, over timescales . 10^8 yr, in strongly starforming galaxies, making these sources well within the reach of ALMA surveys in (sub-)millimeter bands.

From the sun to the Galactic Center: dust, stars and black hole(s)

NASA Astrophysics Data System (ADS)

Fritz, Tobias

2013-07-01

The centers of galaxies are their own ultimate gravitational sinks. Massive black holes and star clusters as well as gas are especially likely to fall into the centers of galaxies by dynamical friction or dissipation. Many galactic centers harbor supermassive black holes (SMBH) and dense nuclear (star) clusters which possibly arrived there by these processes. Nuclear clusters can be formed in situ from gas, or from smaller star clusters which fall to the center. Since the Milky Way harbors both an SMBH and a nuclear cluster, both can be studied best in the Galactic Center (GC), which is the closest galactic nucleus to us. In Chapter 1, I introduce the different components of the Milky Way, and put these into the context of the GC. I then give an overview of relevant properties (e.g. star content and distribution) of the GC. Afterwards, I report the results of four different studies about the GC. In Chapter 2, I analyze the limitations of astrometry, one of the most useful methods for the study of the GC. Thanks to the high density of stars and its relatively small distance from us it is possible to measure the motions of thousands of stars in the GC with images, separated by few years only. I find two main limitations to this method: (1) for bright stars the not perfectly correctable distortion of the camera limits the accuracy, and (2) for the majority of the fainter stars, the main limitation is crowding from the other stars in the GC. The position uncertainty of faint stars is mainly caused by the seeing halos of bright stars. In the very center faint unresolvable stars are also important for the position uncertainty. In Chapter 3, I evaluate the evidence for an intermediate mass black hole in the small candidate cluster IRS13E within the GC. Intermediate mass black holes (IMBHs) have a mass between the two types of confirmed black hole: the stellar remnants and the supermassive black holes in the centers of galaxies. One possibility for! their formation is the collision of stars in a dense young st! ar cluster. Such a cluster could sink to the GC by dynamical friction. There it would consist of few bright stars like IRS13E. Firstly, I analyze the SEDs of the objects in IRS13E. The SEDs of most objects can be explained by pure dust emission. Thus, most objects in IRS13E are pure dust clumps and only three young stars. This reduces the significance of the 'cluster' IRS13E compared to the stellar background. Secondly, I obtain acceleration limits for these three stars. The non-detection of accelerations makes an IMBH an unlikely scenario in IRS13E. However, since its three stars form a comoving association, which is unlikely to form by chance, the nature of IRS13E is not yet settled. In the third study (Chapter 4) I measure and analyze the extinction curve toward the GC. The extinction is a contaminant for GC observations and therefore it is necessary to know the extinction toward the GC to determine the luminosity properties of its stars. I obtain the extinction curve by measuring the flux of the HII region in the GC in several infrared HII lines and in the unextincted radio continuum. I compare these ratios with the ratios expected from recombination physics and obtain extinctions at 22 different lines between 1 and 19 micron. For the K-band I derive A_Ks=2.62+/-0.11. The extinction curve follows a power law with a steep slope of -2.11+/-0.06 shortward of 2.8 micron. At longer wavelengths the extinction is grayer and there are absorption features from ices. The extinction curve is a tool to constrain the properties of cosmic dust between the sun and the GC. The extinction curve cannot be explained by dust grains consisting of carbonaceous and silicate grains only. In addition composite particles, which also contain ices are necessary to fit the extinction curve. In the final part of this thesis (Chapter 5) I look at the properties of most of the stars in the GC. These are the old stars that form the nuclear cluster of the Milky Way. I obtain the mass distribution and the light distribution of these stars. I ! find that the flattening of the stellar distribution increases outside 70''. This indicates that inside a nearly spherical nuclear cluster dominates and that the surrounding light belongs mostly to the nuclear disk. I dissect the light in two components and obtain for the nuclear cluster L_Ks=2.7*10^7 L_sun. I obtain proper motions for more than 10000 stars and radial velocities for more than 2400 stars. Using Jeans modeling I combine velocities and the radial profile to obtain within 100'' (4 pc) a mass of 6.02*10^6 M_sun and a total nuclear cluster mass of 12.88*10^6 M_sun. The Jeans modeling and various other evidence weakly favor a core in the extended mass compared to a cusp. The old star light shows a similar core. The mass to light ratio of the old stars of the nuclear cluster is consistent with the usual initial mass function in the Galaxy. This suggests that most stars in GC formed in the usual way, in a mode different from the origin of the youngest stars there.

Interactions between multiple supermassive black holes in galactic nuclei: a solution to the final parsec problem

NASA Astrophysics Data System (ADS)

Ryu, Taeho; Perna, Rosalba; Haiman, Zoltán; Ostriker, Jeremiah P.; Stone, Nicholas C.

2018-01-01

Using few-body simulations, we investigate the evolution of supermassive black holes (SMBHs) in galaxies (M* = 1010-1012 M⊙ at z = 0) at 0 < z < 4. Following galaxy merger trees from the Millennium simulation, we model BH mergers with two extreme binary decay scenarios for the 'hard binary' stage: a full or an empty loss cone. These two models should bracket the true evolution, and allow us to separately explore the role of dynamical friction and that of multibody BH interactions on BH mergers. Using the computed merger rates, we infer the stochastic gravitational wave background (GWB). Our dynamical approach is a first attempt to study the dynamical evolution of multiple SMBHs in the host galaxies undergoing mergers with various mass ratios (10-4 < q* < 1). Our main result demonstrates that SMBH binaries are able to merge in both scenarios. In the empty loss cone case, we find that BHs merge via multibody interactions, avoiding the 'final parsec' problem, and entering the pulsar timing arrays band with substantial orbital eccentricity. Our full loss cone treatment, albeit more approximate, suggests that the eccentricity becomes even higher when GWs become dominant, leading to rapid coalescences (binary lifetime ≲1 Gyr). Despite the lower merger rates in the empty loss cone case, due to their higher mass ratios and lower redshifts, the GWB in the full/empty loss cone models are comparable (0.70 × 10-15 and 0.53 × 10-15 at a frequency of 1 yr-1, respectively). Finally, we compute the effects of high eccentricities on the GWB spectrum.

A remarkably large depleted core in the Abell 2029 BCG IC 1101

NASA Astrophysics Data System (ADS)

Dullo, Bililign T.; Graham, Alister W.; Knapen, Johan H.

2017-10-01

We report the discovery of an extremely large (Rb ˜2.77 arcsec ≈ 4.2 kpc) core in the brightest cluster galaxy, IC 1101, of the rich galaxy cluster Abell 2029. Luminous core-Sérsic galaxies contain depleted cores - with sizes (Rb) typically 20-500 pc - that are thought to be formed by coalescing black hole binaries. We fit a (double nucleus) + (spheroid) + (intermediate-scale component) + (stellar halo) model to the Hubble Space Telescope surface brightness profile of IC 1101, finding the largest core size measured in any galaxy to date. This core is an order of magnitude larger than those typically measured for core-Sérsic galaxies. We find that the spheroid's V-band absolute magnitude (MV) of -23.8 mag (˜25 per cent of the total galaxy light, I.e. including the stellar halo) is faint for the large Rb, such that the observed core is 1.02 dex ≈ 3.4σs (rms scatter) larger than that estimated from the Rb-MV relation. The suspected scouring process has produced a large stellar mass deficit (Mdef) ˜4.9 × 1011 M⊙, I.e. a luminosity deficit ≈28 per cent of the spheroid's luminosity prior to the depletion. Using IC 1101's black hole mass (MBH) estimated from the MBH-σ, MBH-L and MBH-M* relations, we measure an excessive and unrealistically high number of 'dry' major mergers for IC 1101 (I.e. N ≳ 76) as traced by the large Mdef/MBH ratios of 38-101. The large core, high mass deficit and oversized Mdef/MBH ratio of IC 1101 suggest that the depleted core was scoured by overmassive SMBH binaries with a final coalesced mass MBH ˜ (4-10) × 1010 M⊙, I.e. ˜ (1.7-3.2) × σs larger than the black hole masses estimated using the spheroid's σ, L and M*. The large core might be partly due to oscillatory core passages by a gravitational radiation-recoiled black hole.

The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shipley, Heath V.

2016-01-01

For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with those available from Paα. This new SFR indicator will be useful for probing the peak of the SFR density in the universe (1 < z < 3) and for studying the co-evolution of star-formation and supermassive blackhole accretion contemporaneously in a galaxy.

Inflow Generated X-Ray Corona around Supermassive Black Holes and a Unified Model for X-Ray Emission

NASA Astrophysics Data System (ADS)

Wang, Lile; Cen, Renyue

2016-02-01

Three-dimensional hydrodynamic simulations are performed, which cover the spatial domain from hundreds of Schwarzschild radii to 2 pc around the central supermassive black hole of mass {10}8{M}⊙ , with detailed radiative cooling processes. The existence of a significant amount of shock heated, high temperature (≥slant {10}8 {{K}}) coronal gas in the inner (≤slant {10}4{r}{sch}) region is generally found. It is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures is in reasonable agreement with the overall ensemble spectrum of active galactic nuclei (AGNs) and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shapes, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

Understanding Supermassive Black Hole Growth Mechanisms in the SSA22 Protocluster

NASA Astrophysics Data System (ADS)

Bonine, Brett; Lehmer, Bret

2018-01-01

The SSA22 protocluster is a collection of galaxies at redshift z = 3.09, corresponding to a look back time of 11.6 billion years. Observations of the protocluster allow for the investigation of galaxy properties of such protocluster environments in the early universe, potentially giving insight into the formation and evolution of galaxy clusters visible in the local universe (e.g., the Coma Cluster). Compared to other field galaxies at a similar redshift, a larger fraction of galaxies in SSA22 have been found to possess active galactic nuclei (AGN). This enhanced AGN activity suggests a relationship between the environment within the cluster and the growth of supermassive black holes (SMBHs). I will clarify the role that the protocluster environment at z = 3.09 plays in enhancing the growth of SMBHs in the cluster. To accomplish this, we are analyzing recently obtained WFC3 F160W data from the Hubble Space Telescope (HST) in SSA22, and equivalent archival CANDELS data in the Hubble Deep Field-North, to compare the merger rates and stellar mass distributions of galaxies in the SSA22 protocluster and in the field. Our goal is to assess the relative role that mergers play in enhancing the SMBH growth observed in over-dense regions in the z = 3 Universe.

Multiphase environment of compact galactic nuclei: the role of the nuclear star cluster

NASA Astrophysics Data System (ADS)

Różańska, A.; Kunneriath, D.; Czerny, B.; Adhikari, T. P.; Karas, V.

2017-01-01

We study the conditions for the onset of thermal instability in the innermost regions of compact galactic nuclei, where the properties of the interstellar environment are governed by the interplay of quasi-spherical accretion on to a supermassive black hole (SMBH) and the heating/cooling processes of gas in a dense nuclear star cluster (NSC). Stellar winds are the source of material for radiatively inefficient (quasi-spherical, non-magnetized) inflow/outflow on to the central SMBH, where a stagnation point develops within the Bondi-type accretion. We study the local thermal equilibrium to determine the parameter space that allows cold and hot phases in mutual contact to co-exist. We include the effects of mechanical heating by stellar winds and radiative cooling/heating by the ambient field of the dense star cluster. We consider two examples: the NSC in the Milky Way central region (including the gaseous mini-spiral of Sgr A*), and the ultracompact dwarf galaxy M60-UCD1. We find that the two systems behave in different ways because they are placed in different areas of parameter space in the instability diagram: gas temperature versus dynamical ionization parameter. In the case of Sgr A*, stellar heating prevents the spontaneous formation of cold clouds. The plasma from stellar winds joins the hot X-ray emitting phase and forms an outflow. In M60-UCD1, our model predicts spontaneous formation of cold clouds in the inner part of the galaxy. These cold clouds may survive since the cooling time-scale is shorter than the inflow/outflow time-scale.

Chandra X-Ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-scale Binary Active Galactic Nuclei. II. Host Galaxy Morphology and AGN Activity

NASA Astrophysics Data System (ADS)

Shangguan, Jinyi; Liu, Xin; Ho, Luis C.; Shen, Yue; Peng, Chien Y.; Greene, Jenny E.; Strauss, Michael A.

2016-05-01

Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 on board the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U - Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO 12363.

The nuclear activity and central structure of the elliptical galaxy NGC 5322

NASA Astrophysics Data System (ADS)

Dullo, Bililign T.; Knapen, Johan H.; Williams, David R. A.; Beswick, Robert J.; Bendo, George; Baldi, Ranieri D.; Argo, Megan; McHardy, Ian M.; Muxlow, Tom; Westcott, J.

2018-04-01

We have analysed a new high-resolution e-MERLIN 1.5 GHz radio continuum map together with HST and SDSS imaging of NGC 5322, an elliptical galaxy hosting radio jets, aiming to understand the galaxy's central structure and its connection to the nuclear activity. We decomposed the composite HST + SDSS surface brightness profile of the galaxy into an inner stellar disc, a spheroid, and an outer stellar halo. Past works showed that this embedded disc counter-rotates rapidly with respect to the spheroid. The HST images reveal an edge-on nuclear dust disc across the centre, aligned along the major-axis of the galaxy and nearly perpendicular to the radio jets. After careful masking of this dust disc, we find a central stellar mass deficit Mdef in the spheroid, scoured by SMBH binaries with final mass MBH such that Mdef/MBH ˜ 1.3-3.4. We propose a three-phase formation scenario for NGC 5322, where a few (2-7) `dry' major mergers involving SMBHs built the spheroid with a depleted core. The cannibalism of a gas-rich satellite subsequently creates the faint counter-rotating disc and funnels gaseous material directly on to the AGN, powering the radio core with a brightness temperature of TB, core ˜ 4.5 × 107 K and the low-power radio jets (Pjets ˜ 7.04 × 1020 W Hz-1), which extend ˜1.6 kpc. The outer halo can later grow via minor mergers and the accretion of tidal debris. The low-luminosity AGN/jet-driven feedback may have quenched the late-time nuclear star formation promptly, which could otherwise have replenished the depleted core.

Massive Primordial Black Holes as Dark Matter and their detection with Gravitational Waves

NASA Astrophysics Data System (ADS)

García-Bellido, Juan

2017-05-01

Massive Primordial Black Holes (MPBH) can be formed after inflation due to broad peaks in the primordial curvature power spectrum that collapse gravitationally during the radiation era, to form clusters of black holes that merge and increase in mass after recombination, generating today a broad mass-spectrum of black holes with masses ranging from 0.01 to 105 M⊙ . These MPBH could act as seeds for galaxies and quick-start structure formation, initiating reionization, forming galaxies at redshift z > 10 and clusters at z > 1. They may also be the seeds on which SMBH and IMBH form, by accreting gas onto them and forming the centers of galaxies and quasars at high redshift. They form at rest with zero spin and have negligible cross-section with ordinary matter. If there are enough of these MPBH, they could constitute the bulk of the Dark Matter today. Such PBH could be responsible for the observed fluctuations in the CIB and X-ray backgrounds. MPBH could be directly detected by the gravitational waves emitted when they merge to form more massive black holes, as recently reported by LIGO. Their continuous merging since recombination could have generated a stochastic background of gravitational waves that could eventually be detected by LISA and PTA. MPBH may actually be responsible for the unidentified point sources seen by Fermi, Magic and Chandra. Furthermore, the ejection of stars from shallow potential wells like those of Dwarf Spheroidals (DSph), via the gravitational slingshot effect, could be due to MPBH, thus alleviating the substructure and too-big-to-fail problems of standard collisionless CDM. Their mass distribution peaks at a few tens of M⊙ today, and could therefore be detected also with long-duration microlensing events, as well as by the anomalous motion of stars in the field of GAIA. Their presence as CDM in the Universe could be seen in the time-dilation of strong-lensing images of quasars. The hierarchical large scale structure behaviour of MPBH does not differ from that of ordinary CDM.

Constraints on two accretion disks centered on the equatorial plane of a Kerr SMBH

NASA Astrophysics Data System (ADS)

Pugliese, Daniela; Stuchlík, Zdeněk

2017-12-01

The possibility that two toroidal accretion configurations may be orbiting around a super–massive Kerr black hole has been addressed. Such tori may be formed during different stages of the Kerr attractor accretion history. We consider the relative rotation of the tori and the corotation or counterrotation of a single torus with respect to the Kerr attractor. We give classification of the couples of accreting and non–accreting tori in dependence on the Kerr black hole dimensionless spin. We demonstrate that only in few cases a double accretion tori system may be formed under specific conditions.

Testing the accuracy of reflection-based supermassive black hole spin measurements in AGN

NASA Astrophysics Data System (ADS)

Kammoun, E. S.; Nardini, E.; Risaliti, G.

2018-06-01

Context. X-ray reflection is a very powerful method to assess the spin of supermassive black holes (SMBHs) in active galactic nuclei (AGN), yet this technique is not universally accepted. Indeed, complex reprocessing (absorption, scattering) of the intrinsic spectra along the line of sight can mimic the relativistic effects on which the spin measure is based. Aims: In this work, we test the reliability of SMBH spin measurements that can currently be achieved through the simulations of high-quality XMM-Newton and NuSTAR spectra. Methods: Each member of our group simulated ten spectra with multiple components that are typically seen in AGN, such as warm and (partial-covering) neutral absorbers, relativistic and distant reflection, and thermal emission. The resulting spectra were blindly analysed by the other two members. Results: Out of the 60 fits, 42 turn out to be physically accurate when compared to the input model. The SMBH spin is retrieved with success in 31 cases, some of which (9) are even found among formally inaccurate fits (although with looser constraints). We show that, at the high signal-to-noise ratio assumed in our simulations, neither the complexity of the multi-layer, partial-covering absorber nor the input value of the spin are the major drivers of our results. The height of the X-ray source (in a lamp-post geometry) instead plays a crucial role in recovering the spin. In particular, a success rate of 16 out of 16 is found among the accurate fits for a dimensionless spin parameter larger than 0.8 and a lamp-post height lower than five gravitational radii.

KVN observations reveal multiple γ-ray emission regions in 3C 84?

NASA Astrophysics Data System (ADS)

Hodgson, Jeffrey A.; Rani, Bindu; Lee, Sang-Sung; Algaba, Juan Carlos; Kino, Motoki; Trippe, Sascha; Park, Jong-Ho; Zhao, Guang-Yao; Byun, Do-Young; Kang, Sincheol; Kim, Jae-Young; Kim, Jeong-Sook; Kim, Soon-Wook; Miyazaki, Atsushi; Wajima, Kiyoaki; Oh, Junghwan; Kim, Dae-won; Gurwell, Mark

2018-03-01

3C 84 (NGC 1275) is a well-studied misaligned sctive galactic nucleus (AGN), which has been active in γ-rays since at least 2008. We have monitored the source at four wavelengths (14, 7, 3, and 2 mm) using the Korean VLBI network (KVN) since 2013 as part of the interferometric monitoring of γ-ray bright AGN (iMOGABA) programme, and it exhibits bright radio emission both near the central SMBH and in a slowly moving feature located to the south known as C3. Other facilities have also detected these short-term variations above a slowly rising trend at shorter wavelengths, such as in γ-ray and 1-mm total intensity light curves. We find that the variations in the γ-rays and 1-mm total intensity light curves are correlated, with the γ-ray leading and lagging the radio emission. Analysis of the 2-mm KVN data shows that both the γ-rays and 1-mm total intensity short-term variations are better correlated with the SMBH region than C3, likely placing the short-term variations in C1. We interpret the emission as being due to the random alignment of spatially separated emission regions. We place the slowly rising trend in C3, consistent with previous results. Spectral analysis of the γ-ray data shows that the γ-ray flaring is inconsistent with blazar-like γ-ray emission. Additionally, we report that since mid-2015, a large mm-wave radio flare has been occurring in C3, with a large γ-ray flare coincident with the onset of this flare at all radio wavelengths.

Observational Corollaries of Proto-AGN: Understanding Formation of Supermassive Black Hole Seeds

NASA Astrophysics Data System (ADS)

Shlosman, Isaac

2016-10-01

Formation of supermassive black holes (SMBHs) is still an enigma. Recent detections of high-z quasars which harbor massive SMBHs provide a challenge to models of structure buildup in the universe. Main alternatives for the formation of SMBH seeds are (1) remnants of Population III stars, and (2) a direct baryonic collapse within dark matter (DM) halos of 10^8 Mo -- first halos whose virial temperature exceeds 10^4 K, and which can lead to the formation of proto-AGN -- luminous pre-SMBH objects. Potentially, this can involve both high-z objects as well as low-z dwarf galaxies in voids. We focus on the direct collapse in 10^8 Mo halos which circumvents the pitfalls of Pop III remnants. The collapse can proceed via a radiation pressure-supported quasistar -- with a modified blackbody continuum. Such a configuration requires a very efficient angular momentum transfer. Or, it can form a thick, differentially rotating, self-gravitating disk, which is associated with an X-ray-infrared continuum and Seyfert-level luminosity, anisotropic emission, massive bi-conical outflows, and will be a powerful source of the Ly-alpha emission. We propose to perform radiative transfer in the continuum and hydrogen lines (e.g., Lyman and Balmer), using our models of proto-AGN, and do it on-the-fly -- concurrently with the collapse. We shall test the path to quasistellar and disky proto-AGN, produce first synthetic spectra of proto-AGN, and address the issue of feasibility of their detection by the JWST. Finally, we shall develop the strategy of searching for these objects at high- and low-z, based on the specific features in the spectra and associated variability.

Partitioning the Outburst Energy of a Low Eddington Accretion Rate AGN at the Center of an Elliptical Galaxy: The Recent 12 Myr History of the Supermassive Black Hole in M87

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forman, W.; Jones, C.; Kraft, R.

M87, the active galaxy at the center of the Virgo cluster, is ideal for studying the interaction of a supermassive black hole (SMBH) with a hot, gas-rich environment. A deep Chandra observation of M87 exhibits an approximately circular shock front (13 kpc radius, in projection) driven by the expansion of the central cavity (filled by the SMBH with relativistic radio-emitting plasma) with projected radius ∼1.9 kpc. We combine constraints from X-ray and radio observations of M87 with a shock model to derive the properties of the outburst that created the 13 kpc shock. Principal constraints for the model are (1)more » the measured Mach number ( M ∼ 1.2), (2) the radius of the 13 kpc shock, and (3) the observed size of the central cavity/bubble (the radio-bright cocoon) that serves as the piston to drive the shock. We find that an outburst of ∼5 × 10{sup 57} erg that began about 12 Myr ago and lasted ∼2 Myr matches all the constraints. In this model, ∼22% of the energy is carried by the shock as it expands. The remaining ∼80% of the outburst energy is available to heat the core gas. More than half the total outburst energy initially goes into the enthalpy of the central bubble, the radio cocoon. As the buoyant bubble rises, much of its energy is transferred to the ambient thermal gas. For an outburst repetition rate of about 12 Myr (the age of the outburst), 80% of the outburst energy is sufficient to balance the radiative cooling.« less

Optical, Near-IR, and Sub-mm IFU Observations of the Nearby Dual Active Galactic Nuclei MRK 463

NASA Astrophysics Data System (ADS)

Treister, Ezequiel; Privon, George C.; Sartori, Lia F.; Nagar, Neil; Bauer, Franz E.; Schawinski, Kevin; Messias, Hugo; Ricci, Claudio; U, Vivian; Casey, Caitlin; Comerford, Julia M.; Muller-Sanchez, Francisco; Evans, Aaron S.; Finlez, Carolina; Koss, Michael; Sanders, David B.; Urry, C. Megan

2018-02-01

We present optical and near-IR Integral Field Unit (IFU) and ALMA band 6 observations of the nearby dual active galactic nuclei (AGNs) Mrk 463. At a distance of 210 Mpc, and a nuclear separation of ∼4 kpc, Mrk 463 is an excellent laboratory to study the gas dynamics, star formation processes and supermassive black hole (SMBH) accretion in a late-stage gas-rich major galaxy merger. The IFU observations reveal a complex morphology, including tidal tails, star-forming clumps, and emission-line regions. The optical data, which map the full extent of the merger, show evidence for a biconical outflow and material outflowing at >600 km s‑1, both associated with the Mrk 463E nucleus, along with large-scale gradients likely related to the ongoing galaxy merger. We further find an emission-line region ∼11 kpc south of Mrk 463E that is consistent with photoionization by an AGN. Compared to the current AGN luminosity, the energy budget of the cloud implies a luminosity drop in Mrk 463E by a factor of 3–20 over the last 40,000 years. The ALMA observations of 12CO(2–1) and adjacent 1 mm continuum reveal the presence of ∼109 M ⊙ in molecular gas in the system. The molecular gas shows velocity gradients of ∼800 km s‑1 and ∼400 km s‑1 around the Mrk 463E and 463W nuclei, respectively. We conclude that, in this system, the infall of ∼100s M ⊙ yr‑1 of molecular gas is in rough balance with the removal of ionized gas by a biconical outflow being fueled by a relatively small, <0.01% of accretion onto each SMBH.

The Quest for the Largest Depleted Galaxy Core: Supermassive Black Hole Binaries and Stalled Infalling Satellites

NASA Astrophysics Data System (ADS)

Bonfini, Paolo; Graham, Alister W.

2016-10-01

Partially depleted cores are practically ubiquitous in luminous early-type galaxies (M B ≲ -20.5 mag) and are typically smaller than 1 kpc. In one popular scenario, supermassive black hole (SMBH) binaries—established during dry (I.e., gas-poor) galaxy mergers—kick out the stars from a galaxy’s central region via three-body interactions. Here, this “binary black hole scouring scenario” is probed at its extremes by investigating the two galaxies reported to have the largest partially depleted cores found to date: 2MASX J09194427+5622012 and 2MASX J17222717+3207571 (the brightest galaxy in Abell 2261). We have fit these galaxy’s two-dimensional light distribution using the core-Sérsic model and found that the former galaxy has a core-Sérsic break radius {R}b,{cS}=0.55 {{kpc}}, which is three times smaller than the published value. We use this galaxy to caution that other reportedly large break radii may too have been overestimated if they were derived using the “sharp-transition” (inner core)-to-(outer Sérsic) model. In the case of 2MASX J17222717+3207571, we obtain R b,cS = 3.6 kpc. While we confirm that this is the biggest known partially depleted core of any galaxy, we stress that it is larger than expected from the evolution of SMBH binaries—unless one invokes substantial gravitational-wave-induced (black hole-)recoil events. Given the presence of multiple nuclei located (in projection) within the core radius of this galaxy, we explored and found support for the alternative “stalled infalling perturber” core-formation scenario, in which this galaxy’s core could have been excavated by the action of an infalling massive perturber.

Partitioning the Outburst Energy of a Low Eddington Accretion Rate AGN at the Center of an Elliptical Galaxy: The Recent 12 Myr History of the Supermassive Black Hole in M87

NASA Astrophysics Data System (ADS)

Forman, W.; Churazov, E.; Jones, C.; Heinz, S.; Kraft, R.; Vikhlinin, A.

2017-08-01

M87, the active galaxy at the center of the Virgo cluster, is ideal for studying the interaction of a supermassive black hole (SMBH) with a hot, gas-rich environment. A deep Chandra observation of M87 exhibits an approximately circular shock front (13 kpc radius, in projection) driven by the expansion of the central cavity (filled by the SMBH with relativistic radio-emitting plasma) with projected radius ˜1.9 kpc. We combine constraints from X-ray and radio observations of M87 with a shock model to derive the properties of the outburst that created the 13 kpc shock. Principal constraints for the model are (1) the measured Mach number (M ˜ 1.2), (2) the radius of the 13 kpc shock, and (3) the observed size of the central cavity/bubble (the radio-bright cocoon) that serves as the piston to drive the shock. We find that an outburst of ˜5 × 1057 erg that began about 12 Myr ago and lasted ˜2 Myr matches all the constraints. In this model, ˜22% of the energy is carried by the shock as it expands. The remaining ˜80% of the outburst energy is available to heat the core gas. More than half the total outburst energy initially goes into the enthalpy of the central bubble, the radio cocoon. As the buoyant bubble rises, much of its energy is transferred to the ambient thermal gas. For an outburst repetition rate of about 12 Myr (the age of the outburst), 80% of the outburst energy is sufficient to balance the radiative cooling.

Variable X-Ray Absorption in the Mini-BAL QSO PG 1126-041

NASA Technical Reports Server (NTRS)

Giustini, M.; Cappi, M.; Chartas, G.; Dadina, M.; Eracleous, M.; Ponti, G.; Proga, D.; Tombesi, F.; Vignali, C.; Palumbo, G. G. C.

2011-01-01

Context. X-ray studies of AGN with powerful nuclear winds are important to constrain the physics of the inner accretion/ejection flow around SMBH, and to understand the impact of such winds on the AGN environment. Aims. Our main scientific goal is to constrain the properties of a variable outflowing absorber that is thought to be launched near the SMBH of the mini-BAL QSO PG 1126-041 using a multi-epoch observational campaign performed with XMM-Newton. Methods. We performed temporally resolved X-ray spectroscopy and simultaneous UV and X-ray photometry on the most complete set of observations and on the deepest X-ray exposure of a mini-BAL QSO to date. Results. We found complex X-ray spectral variability on time scales of both months and hours, best reproduced by means of variable massive ionized absorbers along the line of sight. As a consequence, the observed optical-to-X-ray spectral index is found to be variable with time. In the highest signal-to-noise observation we detected highly ionized X-ray absorbing material outflowing much faster (u(sub X) approx. 16 500 km/s) than the UV absorbing one (u(sub uv) approx. 5,000 km/s). This highly ionized absorber is found to be variable on very short (a few kiloseconds) time scales. Conclusions. Our findings are qualitatively consistent with line driven accretion disk winds scenarios. Our observations have opened the time-resolved X-ray spectral analysis field for mini-BAL QSOs; only with future deep studies will we be able to map the dynamics of the inner flow and understand the physics of AGN winds and their impact on the environment.

Violence in the hearts of galaxies: aberration or adolescence?

PubMed

Mundell, Carole G

2002-12-15

Violent activity in the nuclei of galaxies has long been considered a curiosity in its own right; manifestations of this phenomenon include distant quasars in the early Universe and comparatively nearby Seyfert galaxies, both thought to be powered by the release of gravitational potential energy as material from the host galaxy accretes onto a central supermassive black hole (SMBH). Traditionally, the broader study of the formation, structure and evolution of galaxies has largely excluded active galactic nuclei. Recently, however, this situation has changed dramatically, both observationally and theoretically, with the realization that the growth and influence of the SMBH, the origin and development of galaxies and nuclear activity at different epochs in the Universe may be intimately related. The most spectacular fireworks seen in distant quasars may be relatively easy to explain, since the era of greatest quasar activity seems to coincide with turbulent dynamics at the epoch of galaxy formation in the young, gas-rich Universe. Ubiquitous black holes are believed to be a legacy of this violent birth. Alternatively, black holes may be the seeds that drive galaxy formation in the first place. Closer to home, and hence more recently in the history of the Universe, a fraction of comparatively ordinary galaxies, similar to our own, has reignited their central engines, albeit at a lower level of activity. Since these galaxies are more established than their younger and more distant counterparts, the activity here is all the more puzzling. Whatever the mechanisms involved, they are likely to play an important role in galaxy evolution. I review the intriguing evidence for causal links between SMBHs, nuclear activity and the formation and evolution of galaxies, and describe opportunities for testing these relationships using the next generation of earthbound and space-borne astronomical facilities.

Dusty Starbursts within a z=3 Large Scale Structure revealed by ALMA

NASA Astrophysics Data System (ADS)

Umehata, Hideki

The role of the large-scale structure is one of the most important theme in studying galaxy formation and evolution. However, it has been still mystery especially at z>2. On the basis of our ALMA 1.1 mm observations in a z ~ 3 protocluster field, it is suggested that submillimeter galaxies (SMGs) preferentially reside in the densest environment at z ~ 3. Furthermore we find a rich cluster of AGN-host SMGs at the core of the protocluster, combining with Chandra X-ray data. Our results indicate the vigorous star-formation and accelerated super massive black hole (SMBH) growth in the node of the cosmic web.

Merging a Pair of Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-10-01

When galaxies merge, the supermassive black holes (SMBHs) at the galaxies centers are thought to coalesce, forming a new, larger black hole. But can this merger process take place on timescales short enough that we could actually observe it? Results from a new simulation suggests that it can!When Galaxies CollideThese stills demonstrate the time evolution of the galaxy merger after the beginning of the authors simulation (starting from z=3.6). The red and blue dots mark the positions of the SMBHs. [Adapted from Khan et al. 2016]At present, its not well understood how the merger of two SMBHs proceeds from the merger of their host galaxies. Whats more, there are concerns about whether the SMBHs can coalesce on reasonable timescales; in many simulations and models, the inspiral of these behemoths stalls out when they are about a parsec apart, in whats known as the final parsec problem.Why are these mergers poorly understood? Modeling them from the initial interactions of the host galaxies all the way down to the final coalescence of their SMBHs in a burst of gravitational waves is notoriously complicated, due to the enormous range of scales and different processes that must be accounted for.But in a recent study, a team of scientists led by Fazeel Khan (Institute of Space Technology in Pakistan) has presented a simulation that successfully manages to track the entire merger making it the first multi-scale simulation to model the complete evolution of an SMBH binary that forms within a cosmological galaxy merger.Stages of aSimulationKhan and collaborators tackled the challenges of this simulation by using a multi-tiered approach.Beginning with the output of a cosmological hydrodynamical simulation, the authors select a merger of two typical massive galaxies at z=3.6 and use this as the starting point for their simulation. They increase the resolution and add in two supermassive black holes, one at the center of each galaxy.They then continue to evolve the galaxies hydrodynamically, simulating the final stages of the galaxy merger.When the separation of the two SMBHs is small enough, the authors extract a spherical region of 5 kpc from around the pair and evolve this as an N-body simulation.Finally, the separation of the SMBHs becomes so small (0.01 pc) that gravitational-wave emission is the dominant loss of energy driving the inspiral. The authors add post-Newtonian terms into the N-body simulation to account for this.Time evolution of the separation between the SMBHs, beginning with the hydrodynamical simulation (blue), then transitioning to the direct N-body calculation (red), and ending with the introduction of post-Newtonian terms (green) to account for gravitational-wave emission. [Adapted from Khan et al. 2016]Successful CoalescenceKhan and collaborators complex approach allows them to simulate the entire process of the merger and SMBH coalescence, resulting in several key determinations.First, they demonstrate that the SMBHs can coalesce on timescales of only tens of Myr, which is roughly two orders of magnitude smaller than what was typically estimated before. They find that gas dissipation before the merger is instrumental in creating the conditions that allow for this rapid orbital decay.The authors also demonstrate that the gravitational potential of the galaxy merger remnant is triaxial throughout the merger. Khan and collaborators simulations confirm that this non-spherical potential solves the final parsec problem by sending stars on plunging orbits around the SMBHs. These more distant stars cause the SMBHs to lose angular momentum through dynamical friction and continue their inspiral, even when the stars immediately surrounding the SMBHs have been depleted.This simulation isan important step toward a better understanding of SMBH mergers. Its outcomes are especially promising for future gravitational-wave campaigns, as the short SMBH coalescence timescales indicate that these mergers could indeed be observable!CitationFazeel Mahmood Khan et al 2016 ApJ 828 73. doi:10.3847/0004-637X/828/2/73

Supermassive Black Holes in Bulgeless and Dwarf Galaxies: A Multi-Wavelength Investigation

NASA Astrophysics Data System (ADS)

Secrest, Nathan J.

Supermassive black holes (SMBHs) are now understood to reside at the centers of nearly all major galaxies in the Universe. From studies of high-redshift quasars, we understand that SMBHs formed very early in the Universe's history, and well-studied correlations between other properties of galaxies, such as their morphologies, star formation rate, and merger history, with their central SMBH shows that SMBHs played a key role in the evolution of galaxies. The fact that the post-Big Bang Universe was extremely uniform and homogeneous presents a major mystery: How did SMBHs millions to billions of times as massive as the Sun form in such a short time? Given the theoretical limit at which a black hole can accrete material, it is not plausible that SMBHs could have formed through the conventional route: the end stage of the lifecycle of a massive star. Rather, there are two major theories for the formation of SMBHs, each with its own prediction for the black hole mass distribution and occupation fraction in the local Universe. Understanding this mass distribution and occupation fraction is therefore imperative to understanding the formation of SMBHs, the quasars that reveal their presence in the early Universe, and ultimately the evolution of galaxies to the present day. While large SMBHs in major, bulge-dominated galaxies are relatively easy to detect and characterize, this population of SMBHs is understood to have been built up largely through black hole merger events that erase any information about the progenitor black holes' masses. We must therefore search for SMBHs in late-type, bulgeless, and dwarf galaxies, which are much more likely to have had a relatively quiet, merger-free history, in order to glimpse the properties of the `seed' black holes that led to the buildup of SMBHs during the earliest epoch of the Universe. In this thesis, I will discuss my contributions to the understanding of this question, as well as what questions remain to be answered and the future of research in this field.

Exploring the Powerful Ionised Wind in the Seyfert Galaxy PG1211+143

NASA Astrophysics Data System (ADS)

Pounds, Ken

2013-10-01

Highly-ionised high-speed winds in AGN (UFOs) were first detected with XMM-Newton a decade ago, and are now established as a key factor in the study of SMBH accretion, and in the growth and metal enrichment of their host galaxies. However, information on the ionisation and dynamical structure, and the ultimate fate of UFOs remains very limited. We request a 600ks extended XMM-Newton study of the prototype UFO PG1211+143 in AO-13, to obtain high quality EPIC and RGS spectra, to map the flow structure and variability, while seeking evidence for the anticipated interaction with the ISM and possible conversion of the energetic wind to a momentum-driven flow.

Modelling the thermal X-ray emission around the Galactic centre from colliding Wolf-Rayet winds

NASA Astrophysics Data System (ADS)

Russell, Christopher M. P.; Wang, Q. Daniel; Cuadra, Jorge

2017-11-01

We compute the thermal X-ray emission from hydrodynamic simulations of the 30 Wolf-Rayet (WR) stars orbiting within a parsec of Sgr A*, with the aim of interpreting the Chandra X-ray observations of this region. The model well reproduces the spectral shape of the observations, indicating that the shocked WR winds are the dominant source of this thermal emission. The model X-ray flux is tied to the strength of the Sgr A* outflow, which clears out hot gas from the vicinity of Sgr A*. A moderate outflow best fits the present-day observations, even though this supermassive black hole (SMBH) outflow ended ~100 yr ago.

Are Compton-thick AGNs the Missing Link between Mergers and Black Hole Growth?

NASA Astrophysics Data System (ADS)

Kocevski, Dale D.; Brightman, Murray; Nandra, Kirpal; Koekemoer, Anton M.; Salvato, Mara; Aird, James; Bell, Eric F.; Hsu, Li-Ting; Kartaltepe, Jeyhan S.; Koo, David C.; Lotz, Jennifer M.; McIntosh, Daniel H.; Mozena, Mark; Rosario, David; Trump, Jonathan R.

2015-12-01

We examine the host morphologies of heavily obscured active galactic nuclei (AGNs) at z∼ 1 to test whether obscured super-massive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGNs with {N}{{H}}\\gt {10}23.5 {{cm}}-2 and z\\lt 1.5. Using visual classifications, we compare the morphologies of these AGNs to control samples of moderately obscured (1022 cm{}-2\\lt {N}{{H}}\\lt {10}23.5 {{cm}}-2) and unobscured ({N}{{H}}\\lt {10}22 {{cm}}-2) AGN. These control AGNs have similar redshifts and intrinsic X-ray luminosities to our heavily obscured AGN. We find that heavily obscured AGNs are twice as likely to be hosted by late-type galaxies relative to unobscured AGNs ({65.3}-4.6+4.1% versus {34.5}-2.7+2.9%) and three times as likely to exhibit merger or interaction signatures ({21.5}-3.3+4.2% versus {7.8}-1.3+1.9%). The increased merger fraction is significant at the 3.8σ level. If we exclude all point sources and consider only extended hosts, we find that the correlation between the merger fraction and obscuration is still evident, although at a reduced statistical significance (2.5σ ). The fact that we observe a different disk/spheroid fraction versus obscuration indicates that the viewing angle cannot be the only thing differentiating our three AGN samples, as a simple unification model would suggest. The increased fraction of disturbed morphologies with obscuration supports an evolutionary scenario, in which Compton-thick AGNs are a distinct phase of obscured super-massive black hole (SMBH) growth following a merger/interaction event. Our findings also suggest that some of the merger-triggered SMBH growth predicted by recent AGN fueling models may be hidden among the heavily obscured, Compton-thick population.

The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Witzel, G.; Sitarski, B. N.; Ghez, A. M.

We present new adaptive optics (AO) imaging and spectroscopic measurements of Galactic center source G1 from W. M. Keck Observatory. Our goal is to understand its nature and relationship to G2, which is the first example of a spatially resolved object interacting with a supermassive black hole (SMBH). Both objects have been monitored with AO for the past decade (2003–2014) and are comparatively close to the black hole ( a {sub min} ∼ 200–300 au) on very eccentric orbits ( e {sub G1} ∼ 0.99; e {sub G2} ∼ 0.96). While G2 has been tracked before and during periapsis passagemore » ( T {sub 0} ∼ 2014.2), G1 has been followed since soon after emerging from periapsis ( T {sub 0} ∼ 2001.3). Our observations of G1 double the previously reported observational time baseline, which improves its orbital parameter determinations. G1's orbital trajectory appears to be in the same plane as that of G2 but with a significantly different argument of periapsis (Δ ω = 21° ± 4°). This suggests that G1 is an independent object and not part of a gas stream containing G2, as has been proposed. Furthermore, we show for the first time that (1) G1 is extended in the epochs closest to periapsis along the direction of orbital motion, and (2) it becomes significantly smaller over time (450 au in 2004 to less than 170 au in 2009). Based on these observations, G1 appears to be the second example of an object tidally interacting with an SMBH. G1's existence 14 yr after periapsis, along with its compactness in epochs further from the time of periapsis, suggest that this source is stellar in nature.« less

Electromagnetic Signatures of SMBH Coalescence

NASA Technical Reports Server (NTRS)

Schnittman, Jeremy

2012-01-01

When two supermassive black holes (SMBHs) approach within 1-10 mpc, gravitational wave (GW) losses begin to dominate the evolution of the binary, pushing the system to merge in a relatively small time. During this final inspiral regime, the system will emit copious energy in GWs, which should be directly detectable by pulsar timing arrays and space-based interferometers. At the same time, any gas or stars in the immediate vicinity of the merging 5MBHs can get heated and produce bright electromagnetic (EM) counterparts to the GW signals. We present here a number of possible mechanisms by which simultaneous EM and GW signals will yield valuable new information about galaxy evolution, accretion disk dynamics, and fundamental physics in the most extreme gravitational fields.

Quasars at Cosmic Dawn: Discoveries and Probes of the Early Universe

NASA Astrophysics Data System (ADS)

Wang, Feige; Wu, Xue-Bing; Fan, Xiaohui; Yang, Jinyi; Bian, Fuyan; McGreer, Ian D.; Green, Richard F.; Yang, Qian; Jiang, Linhua; Wang, Ran; DECaLS Team; UHS Team

2017-01-01

High redshift quasars, as the most luminous non-transient objects in the early universe, are the most promising tracers to address the history of cosmic reionization and how the origins of super-massive black hole (SMBH) are linked to galaxy formation and evolution. Over the last fifteen years, more than 100 quasars within the first billion years after the Big Bang have been discovered with the highest redshift at 7.1. We have developed a new method to select z>~6 quasars with both high efficiency and high completeness by combing optical and mid-IR Wide-field Infrared Survey Explorer (WISE) photometric data. We have applied this method to SDSS footprint and resulted in the discovery of the most luminous z>6 quasar ever discovered, which hosts a twelve billion solar mass black hole. I will present detailed follow-up observations of the host galaxies and environment of the most luminous quasars using HST, LBT and ALMA, in order to constrain early black hole growth and black hole/galaxy co-evolution at the highest redshift. I will also present initial results from a new quasar survey, which utilizes optical data from DECaLS, which is imaging 6700 deg^2 of sky down to z_AB˜23.0, and neaar-IR data from UHS and UKIDSS, which maps the whole northern sky at Decl.<+60deg. The combination of these datasets allows us to discover quasars at redshift z>~7 and to conduct a complete census of the faint quasar population at z~6.

IMPETUS: Consistent SPH calculations of 3D spherical Bondi accretion onto a black hole

NASA Astrophysics Data System (ADS)

Ramírez-Velasquez, J. M.; Sigalotti, L. Di G.; Gabbasov, R.; Cruz, F.; Klapp, J.

2018-04-01

We present three-dimensional calculations of spherically symmetric Bondi accretion onto a stationary supermassive black hole (SMBH) of mass 108M⊙ within a radial range of 0.02 - 10 pc, using a modified version of the smoothed particle hydrodynamics (SPH) GADGET-2 code, which ensures approximate first-order consistency (i.e., second-order accuracy) for the particle approximation. First-order consistency is restored by allowing the number of neighbours, nneigh, and the smoothing length, h, to vary with the total number of particles, N, such that the asymptotic limits nneigh → ∞ and h → 0 hold as N → ∞. The ability of the method to reproduce the isothermal (γ = 1) and adiabatic (γ = 5/3) Bondi accretion is investigated with increased spatial resolution. In particular, for the isothermal models the numerical radial profiles closely match the Bondi solution, except near the accretor, where the density and radial velocity are slightly underestimated. However, as nneigh is increased and h is decreased, the calculations approach first-order consistency and the deviations from the Bondi solution decrease. The density and radial velocity profiles for the adiabatic models are qualitatively similar to those for the isothermal Bondi accretion. Steady-state Bondi accretion is reproduced by the highly resolved consistent models with a percent relative error of ≲ 1% for γ = 1 and ˜9% for γ = 5/3, with the adiabatic accretion taking longer than the isothermal case to reach steady flow. The performance of the method is assessed by comparing the results with those obtained using the standard GADGET-2 and the GIZMO codes.

Partial dust obscuration in active galactic nuclei as a cause of broad-line profile and lag variability, and apparent accretion disc inhomogeneities

NASA Astrophysics Data System (ADS)

Gaskell, C. Martin; Harrington, Peter Z.

2018-04-01

The profiles of the broad emission lines of active galactic nuclei (AGNs) and the time delays in their response to changes in the ionizing continuum ("lags") give information about the structure and kinematics of the inner regions of AGNs. Line profiles are also our main way of estimating the masses of the supermassive black holes (SMBHs). However, the profiles often show ill-understood, asymmetric structure and velocity-dependent lags vary with time. Here we show that partial obscuration of the broad-line region (BLR) by outflowing, compact, dusty clumps produces asymmetries and velocity-dependent lags similar to those observed. Our model explains previously inexplicable changes in the ratios of the hydrogen lines with time and velocity, the lack of correlation of changes in line profiles with variability of the central engine, the velocity dependence of lags, and the change of lags with time. We propose that changes on timescales longer than the light-crossing time do not come from dynamical changes in the BLR, but are a natural result of the effect of outflowing dusty clumps driven by radiation pressure acting on the dust. The motion of these clumps offers an explanation of long-term changes in polarization. The effects of the dust complicate the study of the structure and kinematics of the BLR and the search for sub-parsec SMBH binaries. Partial obscuration of the accretion disc can also provide the local fluctuations in luminosity that can explain sizes deduced from microlensing.

Luminous, pc-scale CO 6-5 emission in the obscured nucleus of NGC 1377

NASA Astrophysics Data System (ADS)

Aalto, S.; Muller, S.; Costagliola, F.; Sakamoto, K.; Gallagher, J. S.; Falstad, N.; König, S.; Dasyra, K.; Wada, K.; Combes, F.; García-Burillo, S.; Kristensen, L. E.; Martín, S.; van der Werf, P.; Evans, A. S.; Kotilainen, J.

2017-12-01

High-resolution submillimeter line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs). With high-resolution (0.̋06 × 0.̋05 (6 × 5 pc)) ALMA 690 GHz observations we have found bright (TB > 80 K) and compact (full width half maximum size (FWHM) size of 10 × 7 pc) CO 6-5 line emission in the nuclear region of the extremely radio-quiet galaxy NGC 1377. The CO 6-5 intensity is partially aligned with the previously discovered jet/outflow of NGC 1377 and is tracing dense (n > 104cm-3) hot molecular gas at the base of the outflow. The velocity structure is complex and shifts across the jet/outflow are discussed in terms of separate overlapping kinematical components or rotation. High-velocity gas (Δv ± 145km s-1) is detected inside r < 2-3 pc and we suggest that it is emerging from an inclined rotating disk or torus of position angle PA = 140° ± 20° with a dynamical mass of 3 × 106M⊙. This mass is consistent with that of a supermassive black hole (SMBH), as inferred from the M-σ relation. The gas mass of the proposed disk/torus constitutes <3% of the dynamical mass inside a radius of 3 pc. In contrast to the intense CO 6-5 line emission, we do not detect 690 GHz dust continuum in the nuclear region of NGC 1377. The upper limit of S(690 GHz) ≲ 2 mJy implies an H2 column density N(H2) < 3 × 1023cm-2 (averaged in the central 6 × 5 pc beam). This is inconsistent with a Compton thick (CT) source and we discuss the possibility that CT obscuration may instead be occurring on smaller subparsec scales or in a larger foreground structure. From SED fitting we suggest that half of the IR emission of NGC 1377 is nuclear and the rest, mostly the far-infrared (FIR), is emerging from larger scales. The extreme radio quietness, and the lack of emission from other star formation tracers, raise questions on the origin of the FIR emission. We discuss the possibility that it arises from AGN-heated dust along the minor axis. The reduced datacube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A22

Feeding and feedback in radio galaxies of the local universe

NASA Astrophysics Data System (ADS)

Couto, Guilherme dos Santos

2016-10-01

We present integral field spectroscopic data covering the inner kiloparsecs of four radio galaxies of the local Universe (z<0.07), Arp 102B, Pictor A, 3C 33 and 4C +29.30, obtained with the GMOS-IFU instrument of the Gemini telescopes. We use these data to analyze the gas excitation and kinematics via two-dimensional maps. Using the flux distributions of the emission lines, we identify extended emission in ionized gas up to the edges of the observed field, which corresponds to 1.7 kpc x 2.5 kpc for Arp 102B, 2.5 kpc x 3.4 kpc for Pictor A, 4.0 kpc x 5.8 kpc for 3C 33 and 4.3 kpc x 6.2 kpc for 4C +29.30. The extended line emitting gas displays structures resembling rotating disks, spiral arms and bars. Line ratios indicate that both photons from the nuclear source and shocks originated in the interaction of the radio jet with circumnuclear gas are ionizing mechanisms of the gas. Line ratio values are typical of Seyfert galaxies for 3C 33 and 4C +29.30, while intermediate values between Seyferts and LINERs are observed in Arp 102B. Pictor A galaxy, however, shows low values of [NII]/Ha=0.15-0.25, expected for HII regions. We suggest that these values are observed due to the low gas metallicity (12+log(O/H)=8.39). Centroid velocity maps show that the gas kinematics is dominated by rotation only in Arp 102B and 3C 33. Outflows are observed in the galaxies Arp 102B, 3C 33 and 4C +29.30. We obtain mass outflow rates of 0.32-0.49 Msun per year, but the outflow kinetic power is small, ranging 0.04-0.07% of the AGN bolometric luminosity, indicating that the feedback has little impact in the host galaxies evolution. The high masses of ionized gas, ranging from 7.4E7 to 4.6E8 Msun, and the fact that these galaxies are early-type, suggest an external origin of the gas. Indeed, it is observed evidence of interaction with companion galaxies in Arp 102B, Pictor A and 4C +29.30. We suggest that the capture of mass has triggered the nuclear activity in these galaxies, with the high masses feeding not only the SMBH but also being a possible source of star formation.

Digital Signal Processing for the Event Horizon Telescope

NASA Astrophysics Data System (ADS)

Weintroub, Jonathan

2015-08-01

A broad international collaboration is building the Event Horizon Telescope (EHT). The aim is to test Einstein’s theory of General Relativity in one of the very few places it could break down: the strong gravity regime right at the edge of a black hole. The EHT is an earth-size VLBI array operating at the shortest radio wavelengths, that has achieved unprecedented angular resolution of a few tens of μarcseconds. For nearby super massive black holes (SMBH) this size scale is comparable to the Schwarzschild Radius, and emission in the immediate neighborhood of the event horizon can be directly observed. We give an introduction to the science behind the CASPER-enabled EHT, and outline technical developments, with emphasis on the secret sauce of high speed signal processing.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan Changshuo; Wang Jianmin, E-mail: wangjm@ihep.ac.c

High spatial resolution observations show that high-redshift galaxies are undergoing intensive evolution of dynamical structure and morphologies displayed by the H{alpha}, H{beta}, [O III], and [N II] images. It has been shown that supernova explosion (SNexp) of young massive stars during the star formation epoch, as kinetic feedback to host galaxies, can efficiently excite the turbulent viscosity. We incorporate the feedback into the dynamical equations through mass dropout and angular momentum transportation driven by the SNexp-excited turbulent viscosity. The empirical Kennicutt-Schmidt law is used for star formation rates (SFRs). We numerically solve the equations and show that there can bemore » intensive evolution of structure of the gaseous disk. Secular evolution of the disk shows interesting characteristics: (1) high viscosity excited by SNexp can efficiently transport the gas from 10 kpc to {approx}1 kpc forming a stellar disk whereas a stellar ring forms for the case with low viscosity; (2) starbursts trigger SMBH activity with a lag of {approx}10{sup 8} yr depending on SFRs, prompting the joint evolution of SMBHs and bulges; and (3) the velocity dispersion is as high as {approx}100 km s{sup -1} in the gaseous disk. These results are likely to vary with the initial mass function (IMF) that the SNexp rates rely on. Given the IMF, we use the GALAXEV code to compute the spectral evolution of stellar populations based on the dynamical structure. In order to compare the present models with the observed dynamical structure and images, we use the incident continuum from the simple stellar synthesis and CLOUDY to calculate emission line ratios of H{alpha}, H{beta}, [O III], and [N II], and H{alpha} brightness of gas photoionized by young massive stars formed on the disks. The models can produce the main features of emission from star-forming galaxies. We apply the present model to two galaxies, BX 389 and BX 482 observed in the SINS high-z sample, which are bulge and disk-dominated, respectively. Two successive rings independently evolving are able to reproduce the main dynamical and emission properties of the two galaxies, such as the Baldwin-Phillips-Terlevich diagram, the relation between line ratios, and H{alpha} brightness. The observed relation between turbulent velocity and the H{alpha} brightness can be explained by the present model. High viscosity excited by SNexp is able to efficiently transport the gas into a bulge to maintain high SFRs or to form a stellar ring close enough to the bulge so that it immigrates into the bulge of its host galaxy. This leads to a fast growing bulge. Implications and future work of the present models have been extensively discussed for galaxy formation in high-z universe.« less

Detection of significant cm to sub-mm band radio and  γ-ray correlated variability in Fermi bright blazars

DOE PAGES

Fuhrmann, L.; Larsson, S.; Chiang, J.; ...

2014-05-12

The exact location of the γ-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11 cm to 0.8 mm wavelength, F-GAMMA programme) and γ-ray (0.1–300 GeV) ~3.5 yr light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations. These results reveal: (i) the first highly significant multiband radio and γ-ray correlations (radio lagging γ rays) when averaging over the whole sample, (ii) average time delays (source frame: 76 ± 23 to 7 ±more » 9 d), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence τr, γ(ν) ∝ ν -1, in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk γ-ray production region typically located within/upstream of the 3 mm core region (τ3mm, γ = 12 ± 8 d), (iv) mean distances between the region of γ-ray peak emission and the radio ‘τ = 1 photosphere’ decreasing from 9.8 ± 3.0 pc (11 cm) to 0.9 ± 1.1 pc (2 mm) and 1.4 ± 0.8 pc (0.8 mm), (v) 3 mm/γ-ray correlations in nine individual sources at a significance level where one is expected by chance (probability: 4 × 10 -6), (vi) opacity and ‘time lag core shift’ estimates for quasar 3C 454.3 providing a lower limit for the distance of the bulk γ-ray production region from the supermassive black hole (SMBH) of ~0.8–1.6 pc, i.e. at the outer edge of the broad-line region (BLR) or beyond. A 3 mm τ = 1 surface at ~2–3 pc from the jet base (i.e. well outside the ‘canonical BLR’) finally suggests that BLR material extends to several parsec distances from the SMBH.« less

An X-ray survey of the central molecular zone: Variability of the Fe Kα emission line

NASA Astrophysics Data System (ADS)

Terrier, R.; Clavel, M.; Soldi, S.; Goldwurm, A.; Ponti, G.; Morris, M. R.; Chuard, D.

2018-05-01

There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 yr or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Kα line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000-2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000-2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 yr) events. Images of the Fe Kα emission as FITS files are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A102

Is an Accreting Binary Black Hole Precursor Driving the Ionisation Structure and its Kinematics in the Carafe?

NASA Astrophysics Data System (ADS)

Shastri, Prajval

2017-09-01

We seek to test the hypothesis that radiatively efficient accretion onto the central supermassive black holes (SMBHs) of two merging galaxies drive the emission-line structure and kinematics that we see in the ROSAT-detected Carafe. We have confirmed the presence of two compact sources with LINER-type spectra, which coincide with two compact radio sources that we detect. We have obtained the emission-line structure and kinematics of the Carafe with an optical IFU mosaic. We demonstrate that the proposed 35ksec ACIS imaging will yield both the soft and hard X-ray photons that we need to definitively distinguish between the following hypotheses: that the driver of the system is a pair of accreting SMBH, or that the hot extended gas in the Carafe is shock-excited by two compact star bursts.

On the rate of black hole binary mergers in galactic nuclei due to dynamical hardening

NASA Astrophysics Data System (ADS)

Leigh, N. W. C.; Geller, A. M.; McKernan, B.; Ford, K. E. S.; Mac Low, M.-M.; Bellovary, J.; Haiman, Z.; Lyra, W.; Samsing, J.; O'Dowd, M.; Kocsis, B.; Endlich, S.

2018-03-01

We assess the contribution of dynamical hardening by direct three-body scattering interactions to the rate of stellar-mass black hole binary (BHB) mergers in galactic nuclei. We derive an analytic model for the single-binary encounter rate in a nucleus with spherical and disc components hosting a super-massive black hole (SMBH). We determine the total number of encounters NGW needed to harden a BHB to the point that inspiral due to gravitational wave emission occurs before the next three-body scattering event. This is done independently for both the spherical and disc components. Using a Monte Carlo approach, we refine our calculations for NGW to include gravitational wave emission between scattering events. For astrophysically plausible models, we find that typically NGW ≲ 10. We find two separate regimes for the efficient dynamical hardening of BHBs: (1) spherical star clusters with high central densities, low-velocity dispersions, and no significant Keplerian component and (2) migration traps in discs around SMBHs lacking any significant spherical stellar component in the vicinity of the migration trap, which is expected due to effective orbital inclination reduction of any spherical population by the disc. We also find a weak correlation between the ratio of the second-order velocity moment to velocity dispersion in galactic nuclei and the rate of BHB mergers, where this ratio is a proxy for the ratio between the rotation- and dispersion-supported components. Because discs enforce planar interactions that are efficient in hardening BHBs, particularly in migration traps, they have high merger rates that can contribute significantly to the rate of BHB mergers detected by the advanced Laser Interferometer Gravitational-Wave Observatory.

Spherical accretion in giant elliptical galaxies: multi-transonicity, shocks, and implications on AGN feedback

NASA Astrophysics Data System (ADS)

Raychaudhuri, Sananda; Ghosh, Shubhrangshu; Joarder, Partha S.

2018-06-01

Isolated massive elliptical galaxies, or that are present at the center of cool-core clusters, are believed to be powered by hot gas accretion directly from their surrounding hot X-ray emitting gaseous medium. This leads to a giant Bondi-type spherical/quasi-spherical accretion flow onto their host SMBHs, with the accretion flow region extending well beyond the Bondi radius. In this work, we present a detailed study of Bondi-type spherical flow in the context of these massive ellipticals by incorporating the effect of entire gravitational potential of the host galaxy in the presence of cosmological constant Λ, considering a five-component galactic system (SMBH + stellar + dark matter + hot gas + Λ). The current work is an extension of Ghosh & Banik (2015), who studied only the cosmological aspect of the problem. The galactic contribution to the potential renders the (adiabatic) spherical flow to become multi-transonic in nature, with the flow topology and flow structure significantly deviating from that of classical Bondi solution. More notably, corresponding to moderate to higher values of galactic mass-to-light ratios, we obtain Rankine-Hugoniot shocks in spherical wind flows. Galactic potential enhances the Bondi accretion rate. Our study reveals that there is a strict lower limit of ambient temperature below which no Bondi accretion can be triggered; which is as high as ˜9 × 106 K for flows from hot ISM-phase, indicating that the hot phase tightly regulates the fueling of host nucleus. Our findings may have wider implications, particularly in the context of outflow/jet dynamics, and radio-AGN feedback, associated with these massive galaxies in the contemporary Universe.

The Possible Submillimeter Bump and Accretion-jet in the Central Supermassive Black Hole of NGC 4993

NASA Astrophysics Data System (ADS)

Wu, Qingwen; Feng, Jianchao; Fan, Xuliang

2018-03-01

NGC 4993, as a host galaxy of the electromagnetic counterpart of the first gravitational-wave detection of a binary neutron-star merger, was observed by many powerful telescopes from radio to γ-ray wavebands. The weak nuclear activities of NGC 4993 suggest that it is a low-luminosity active galactic nuclei (LLAGNs). We build the multiwaveband spectral energy distributions (SEDs) of NGC 4993 from the literature. We find that the radio spectrum at ∼100–300 GHz is much steeper than that of the low-frequency waveband (e.g., 6–100 GHz), where this break was also found in the supermassive black holes (SMBHs) in our galaxy center (Sgr A*), and in some other nearby AGNs. The radio emission above and below this break may have different physical origins, which provide an opportunity to probe the accretion and jet properties. We model the multiwaveband SEDs of NGC 4993 with an advection-dominated accretion flow (ADAF) jet model. We find that the high-frequency steep radio emission at the millimeter waveband is consistent with the prediction of the ADAF, while the low-frequency flat radio spectrum is better fitted by the jet. Furthermore, the X-ray emission can also be simultaneously explained by the ADAF model. From the model fits, we estimate important parameters of the central engine (e.g., the accretion rate near the horizon of the black hole and the mass-loss rate in the jet) for NGC 4993. This result strengthens the theory that the millimeter, submillimeter, and deep X-ray observations are crucial to understanding the weak or quiescent activities in SMBH systems. Further simultaneous millimeter and X-ray monitoring of this kind of LLAGN will help us to better understand the physical origin of multiwaveband emission.

The imprint of the cosmic supermassive black hole growth history on the 21 cm background radiation

NASA Astrophysics Data System (ADS)

Tanaka, Takamitsu L.; O'Leary, Ryan M.; Perna, Rosalba

2016-01-01

The redshifted 21 cm transition line of hydrogen tracks the thermal evolution of the neutral intergalactic medium (IGM) at `cosmic dawn', during the emergence of the first luminous astrophysical objects (˜100 Myr after the big bang) but before these objects ionized the IGM (˜400-800 Myr after the big bang). Because X-rays, in particular, are likely to be the chief energy courier for heating the IGM, measurements of the 21 cm signature can be used to infer knowledge about the first astrophysical X-ray sources. Using analytic arguments and a numerical population synthesis algorithm, we argue that the progenitors of supermassive black holes (SMBHs) should be the dominant source of hard astrophysical X-rays - and thus the primary driver of IGM heating and the 21 cm signature - at redshifts z ≳ 20, if (I) they grow readily from the remnants of Population III stars and (II) produce X-rays in quantities comparable to what is observed from active galactic nuclei and high-mass X-ray binaries. We show that models satisfying these assumptions dominate over contributions to IGM heating from stellar populations, and cause the 21 cm brightness temperature to rise at z ≳ 20. An absence of such a signature in the forthcoming observational data would imply that SMBH formation occurred later (e.g. via so-called direct collapse scenarios), that it was not a common occurrence in early galaxies and protogalaxies, or that it produced far fewer X-rays than empirical trends at lower redshifts, either due to intrinsic dimness (radiative inefficiency) or Compton-thick obscuration close to the source.

A mass census of the nearby universe with the RESOLVE survey

NASA Astrophysics Data System (ADS)

Eckert, Kathleen

The galaxy mass function, i.e., the distribution of galaxies as a function of mass, is a useful way to characterize the galaxy population. In this work, we examine the stellar and baryonic mass function, and the velocity function of galaxies and galaxy groups for two volume-limited surveys of the nearby universe. Stellar masses are estimated from multi-band photometry, and we add cold atomic gas from measurements and a newly calibrated estimator to obtain baryonic mass. Velocities are measured from the internal motions of galaxies and groups and account for all matter within the system. We compare our observed mass and velocity functions with the halo mass function from theoretical simulations of dark matter, which predict a much more steeply rising low-mass slope than is normally observed for the galaxy mass function. We show that taking into account the cold gas mass, which dominates the directly detectable mass of low-mass galaxies, steepens the low-mass slope of the galaxy mass function. The low- mass slope of the baryonic mass function, however, is still much shallower than that of the halo mass function. The discrepancy in low-mass slope persists when examining the velocity function, which accounts for all matter in galaxies (detectable or not), suggesting that some mechanism must reduce the mass in halos or destroy them completely. We investigate the role of environment by performing group finding and examining the mass and velocity functions as a function of group halo mass. Broken down by halo mass regime, we find dips and varying low-mass slopes in the mass and velocity functions, suggesting that group formation processes such as merging and stripping, which destroy and lower the mass of low-mass satellites respectively, potentially contribute to the discrepancy in low-mass slope. In particular, we focus on the nascent group regime, groups of mass 10 11.4-12 [solar mass] with few members, which has a depressed and flat low-mass slope in the galaxy mass and velocity function. We find that nascent groups are at the peak baryonic collapse efficiency (group-integrated cold baryonic mass divided by the group halo mass), while isolated dwarfs in lower mass halos are rapidly growing in their collapsed baryonic mass and larger groups are increasingly dominated by their hot halo gas. Scatter in this collapsed baryon efficiency could indicate varying hot gas fractions in nascent groups, suggestive of a wide variety of group formation processes occurring at these scales. We point to this nascent group regime as a period of transition in group evolution, where merging and stripping remove galaxies from the population, contributing to the discrepancy in low-mass slope between observations and dark matter simulations.

A new detection of an UFO in the X-ray spectrum of a lensed QSO

NASA Astrophysics Data System (ADS)

Dadina, M.

2017-10-01

The discovery of the "M_{SMBH}-σ relation" indicated that a connection between the central black-hole and the hosting galaxies acted during the cosmic time. With the discovery in X-rays of the ultra-fast outflows in nearby AGN, we have most probably probed one of the ingredients that are needed to build-up this mechanism. At high-z, however, such measurements were possible only in an handful of objects and this was possible mainly for the presence of gravitational lenses that magnified otherwise X-ray weak QSO. Following this, we proposed a program to use XMM-Newton and gravitational lenses as telescopes to point bright, lensed and distant QSO to characterize in detail their X-ray spectrum and to detect blushifted absorption lines at E˜7-10 keV (rest frame). Here we present the preliminary results obtained for the z=2.64 QSO MG J0414+0534.

A Numerical Study on the Streams of Star Debris after Tidal Disruption

NASA Astrophysics Data System (ADS)

Camacho Olachea, Priscila; Ramirez-Ruiz, Enrico; Law-Smith, Jamie

2017-01-01

Lurking at the centers of most galaxies are gigantic star and gas devouring monsters. These monsters are supermassive black holes (SMBHs), some of which are larger than our solar system and ten billion times as massive as our own Sun. The vast majority of stars in the universe live for tens of billions of years, eventually dying from old age as the nuclearreactions that power them become progressively less effective. But for every ten thousand stars that die peacefully, one star will be brutally torn apart by the extreme tidal forces present as it passes near a SMBH. My recent work has been to develop computational tools necessary to study the fates of stars disrupted by SMBHs. In this research project I presentthe results of my numerical study aimed at understanding the streams of star debris that result after disruption.

Obscured AGNs in Bulgeless Hosts discovered by WISE: The Case Study of SDSS J1224+5555

NASA Astrophysics Data System (ADS)

Satyapal, S.; Secrest, N. J.; Rothberg, B.; O'Connor, J. A.; Ellison, S. L.; Hickox, R. C.; Constantin, A.; Gliozzi, M.; Rosenberg, J. L.

2016-08-01

There is mounting evidence that supermassive black holes (SMBHs) form and grow in bulgeless galaxies. However, a robust determination of the fraction of active galactic nuclei (AGNs) in bulgeless galaxies, an important constraint to models of SMBH seed formation and merger-free models of AGN fueling, is unknown, since optical studies have been shown to be incomplete for AGNs in low-mass galaxies. In a recent study using the Wide-field Infrared Survey Explorer, we discovered hundreds of bulgeless galaxies that display mid-infrared signatures of extremely hot dust suggestive of powerful accreting massive black holes, despite having no signatures of black hole activity at optical wavelengths. Here we report X-ray follow-up observations of J122434.66+555522.3, a nearby (z = 0.052) isolated bulgeless galaxy that contains an unresolved X-ray source detected at the 3σ level by XMM-Newton with an observed luminosity uncorrected for intrinsic absorption of {L}2-10{keV}=(1.1+/- 0.4)× {10}40 erg s-1. Ground-based near-infrared spectroscopy with the Large Binocular Telescope and multiwavelength observations from ultraviolet to millimeter wavelengths together suggest that J1224+5555 harbors a highly absorbed AGN with an intrinsic absorption of {N}{{H}}\\gt {10}24 cm-2. The hard X-ray luminosity of the putative AGN corrected for absorption is {L}2-10{keV}˜ 3× {10}42 erg s-1, which, depending on the bolometric correction factor, corresponds to a bolometric luminosity of the AGN of {L}{bol}.˜ 6× {10}43-3 × 1044 {erg} {{{s}}}-1 and a lower mass limit for the black hole of {M}{BH}≃ 2× {10}6 {M}⊙ , based on the Eddington limit. While enhanced X-ray emission and hot dust can be produced by star formation in extremely low metallicity environments typical in dwarf galaxies, J1224+5555 has a stellar mass of ˜ 2.0× {10}10 {M}⊙ and an above solar metallicity (12 + {logO}/{{H}} = 9.11), typical of our WISE-selected bulgeless galaxy sample. While collectively these observations suggest the presence of an AGN, we caution that identifying obscured AGNs in the low-luminosity regime is challenging and often requires multiwavelength observations. These observations suggest that low-luminosity AGNs can be heavily obscured and reside in optically quiescent galaxies, adding to the growing body of evidence that the fraction of bulgeless galaxies with accreting black holes may be significantly underestimated based on optical studies.

When Supermassive Black Holes Wander

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-05-01

Are supermassive black holes found only at the centers of galaxies? Definitely not, according to a new study in fact, galaxies like the Milky Way may harbor several such monsters wandering through their midst.Collecting Black Holes Through MergersIts generally believed that galaxies are built up hierarchically, growing in size through repeated mergers over time. Each galaxy in a major merger likely hosts a supermassive black hole a black hole of millions to billions of times the mass of the Sun at its center. When a pair of galaxies merges, their supermassive black holes will often sink to the center of the merger via a process known as dynamical friction. There the supermassive black holes themselves will eventually merge in a burst of gravitational waves.Spatial distribution and velocities of wandering supermassive black holes in three of the authors simulated galaxies, shown in edge-on (left) and face-on (right) views of the galaxy disks. Click for a closer look. [Tremmel et al. 2018]But if a galaxy the size of the Milky Way was built through a history of many major galactic mergers, are we sure that all its accumulated supermassive black holes eventually merged at the galactic center? A new study suggests that some of these giants might have escaped such a fate and they now wander unseen on wide orbits through their galaxies.Black Holes in an Evolving UniverseLed by Michael Tremmel (Yale Center for Astronomy Astrophysics), a team of scientists has used data from a large-scale cosmological simulation, Romulus25, to explore the possibility of wandering supermassive black holes. The Romulus simulations are uniquely suited to track the formation and subsequent orbital motion of supermassive black holes as galactic halos are built up through mergers over the history of the universe.From these simulations, Tremmel and collaborators find an end total of 316 supermassive black holes residing within the bounds of 26 Milky-Way-mass halos. Of these, roughly a third are wanderers within 10 kpc of the halo center (roughly the size of the Milky Ways disk).These wandering supermassive black holes were kicked onto wide orbits during the merger of their host galaxy with the main halo; Tremmel and collaborators find that their orbits are often tilted, lying outside of the galactic disk. Because these black holes travel through relatively deserted regions, they accumulate little mass and are rarely perturbed in their journeys, wandering for billions of years.Finding MonstersCumulative fraction of simulated Milky-Way-mass halos as a function of the number of supermassive black holes they host. All of the halos host at least one SMBH within 10 kpc from halo center, but the majority host more than that. [Tremmel et al. 2018]Tremmel and collaborators simulations suggest that, regardless of its merger history, a Milky-Way-mass halo will end up with an average of 5 supermassive black holes within 10 kpc of the galaxy center, and an average of 12 within its larger virial radius! This means there could be a number of supermassive black holes just like the enormous Sgr A* at our galaxys core wandering the Milky Way unseen.So how can we find these invisible monsters? We already have some observational evidence in the form of offset and dual active galactic nuclei of non-central supermassive black holes in distant galaxies. As for nearby, our best bet is to look for tidal disruption events, the burps of emission that occur when an otherwise invisible black hole encounters a star or a cloud of gas.CitationMichael Tremmel et al 2018 ApJL 857 L22. doi:10.3847/2041-8213/aabc0a

Dynamical and Radiative Modeling of Sagittarius A*

NASA Astrophysics Data System (ADS)

Shcherbakov, Roman V.

2011-09-01

Sgr A* in our Galactic Center is the closest supermassive black hole (SMBH) with the largest event horizon angular size. Most other SMBHs are likely in the same dormant low-luminosity accretion state as Sgr A*. Thus, the important physical effects in lives of BHs can be best observed and studied in our Galactic Center. One of these effects is electron heat conduction. Conduction may be the main reason why Sgr A* is so dramatically underluminous: it transfers heat outwards from the inner flow and unbinds the outer flow, quenching the accretion. In Chapter 3 I build a realistic model of accretion with conduction, which incorporates feeding by stellar winds. In a model with accretion rate < 1% of the naive Bondi estimate I achieve agreement of the X-ray surface brightness profile and Faraday rotation measure to observations. An earlier model proposed in Chapter 2 with adiabatic accretion of turbulent magnetized medium cannot be tweaked to match the observations. Its accretion rate appears too large, so turbulent magnetic field cannot stop gas from falling in. Low accretion rate leads to a peculiar radiation pattern from near the BH: cyclo-synchrotron polarized radiation is observed in radio/sub-mm. Since it comes from several Schwarzschild radii, the BH spin can be determined, when we overcome all modeling challenges. I fit the average observed radiation spectrum with a theoretical spectrum, which is computed by radiative transfer over a simulation-based model. Relevant plasma effects responsible for the observed polarization state are accurately computed for thermal plasma in Chapter 4. The prescription of how to perform the correct general relativistic polarized radiative transfer is elaborated in Chapter 5. Application of this technique to three-dimensional general relativistic magneto hydrodynamic numerical simulations is reported in Chapter 6. The main results of analysis are that the spin inclination angle is estimated to lie within a narrow range theta est = 50° -- 59°, and most probable value of BH spin is a* = 0.9. I believe the researched topics will play a central role in future modeling of typical SMBH accretion and will lead to effective ways to determine the spins of these starving eaters. Computations of plasma effects reported here will also find applications when comparing models of jets to observations.

A Mass Census of the Nearby Universe with RESOLVE and ECO

NASA Astrophysics Data System (ADS)

Eckert, Kathleen D.; Kannappan, Sheila; Stark, David; Moffett, Amanda J.; Norris, Mark A.; Berlind, Andreas A.; Hall, Kirsten; Baker, Ashley; Snyder, Elaine M.; Bittner, Ashley; Hoversten, Erik A.; Lagos, Claudia; Nasipak, Zachary; RESOVE Team

2017-01-01

The low-mass slope of the galaxy stellar mass function is significantly shallower than that of the theoretical dark matter halo mass function, leading to several possible interpretations including: 1) stellar mass does not fully represent galaxy mass, 2) galaxy formation becomes increasingly inefficient in lower mass halos, and 3) environmental effects, such as stripping and merging, may change the mass function. To investigate these possible scenarios, we present the census of stellar, baryonic (stars + cold gas), and dynamical masses of galaxies and galaxy groups for the RESOLVE and ECO surveys. RESOLVE is a highly complete volume-limited survey of ~1500 galaxies, enabling direct measurement of galaxy mass functions without statistical completeness corrections down to baryonic mass Mb ~ 10^9 Msun. ECO provides a larger data set (~10,000 galaxies) complete down to Mb ~ 10^9.4 Msun. We show that the baryonic mass function has a steeper low-mass slope than the stellar mass function due to the large population of low-mass, gas-rich galaxies. The baryonic mass function’s low-mass slope, however, is still significantly shallower than that of the dark matter halo mass function. A more direct probe of total galaxy mass is its characteristic velocity, and we present RESOLVE’s preliminary galaxy velocity function, which combines ionized-gas rotation curves, stellar velocity dispersions, and estimates from scaling relations. The velocity function also diverges from the dark matter halo velocity function at low masses. To study the effect of environment, we break the mass functions into different group halo mass bins, finding complex substructure, including a depressed and flat low-mass slope for groups with halo masses ~10^11.4-12 Msun, which we refer to as the nascent group regime, with typical membership of 2-4 galaxies. This substructure is suggestive of efficient merging or gas stripping in nascent groups, which we find also have large scatter in their cold-baryon fractions, possibly pointing to diversity in hot halo gas content in this regime. This work is supported by NSF grant AST-0955368, the NC Space Grant Graduate Research Fellowship Program, and a UNC Royster Society Dissertation Completion Fellowship.

Validation: Codes to compare simulation data to various observations

NASA Astrophysics Data System (ADS)

Cohn, J. D.

2017-02-01

Validation provides codes to compare several observations to simulated data with stellar mass and star formation rate, simulated data stellar mass function with observed stellar mass function from PRIMUS or SDSS-GALEX in several redshift bins from 0.01-1.0, and simulated data B band luminosity function with observed stellar mass function, and to create plots for various attributes, including stellar mass functions, and stellar mass to halo mass. These codes can model predictions (in some cases alongside observational data) to test other mock catalogs.

Low-luminosity stellar mass functions in globular clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richer, H.B.; Fahlman, G.G.; Buonanno, R.

New data are presented on cluster luminosity functions and mass functions for selected fields in the globular clusters M13 and M71, extending down the main sequence to at least 0.2 solar mass. In this experiment, CCD photometry data were obtained at the prime focus of the CFHT on the cluster fields that were far from the cluster center. Luminosity functions were constructed, using the ADDSTAR routine to correct for the background, and mass functions were derived using the available models. The mass functions obtained for M13 and M71 were compared to existing data for NGC 6397. Results show that (1)more » all three globular clusters display a marked change in slope at about 0.4 solar mass, with the slopes becoming considerably steeper toward lower masses; (2) there is no correlation between the slope of the mass function and metallicity; and (3) the low-mass slope of the mass function for M13 is much steeper than for NGC 6397 and M71. 22 refs.« less

Slicing cluster mass functions with a Bayesian razor

NASA Astrophysics Data System (ADS)

Sealfon, C. D.

2010-08-01

We apply a Bayesian ``razor" to forecast Bayes factors between different parameterizations of the galaxy cluster mass function. To demonstrate this approach, we calculate the minimum size N-body simulation needed for strong evidence favoring a two-parameter mass function over one-parameter mass functions and visa versa, as a function of the minimum cluster mass.

Measuring Aggregation of Events about a Mass Using Spatial Point Pattern Methods

PubMed Central

Smith, Michael O.; Ball, Jackson; Holloway, Benjamin B.; Erdelyi, Ferenc; Szabo, Gabor; Stone, Emily; Graham, Jonathan; Lawrence, J. Josh

2017-01-01

We present a methodology that detects event aggregation about a mass surface using 3-dimensional study regions with a point pattern and a mass present. The Aggregation about a Mass function determines aggregation, randomness, or repulsion of events with respect to the mass surface. Our method closely resembles Ripley’s K function but is modified to discern the pattern about the mass surface. We briefly state the definition and derivation of Ripley’s K function and explain how the Aggregation about a Mass function is different. We develop the novel function according to the definition: the Aggregation about a Mass function times the intensity is the expected number of events within a distance h of a mass. Special consideration of edge effects is taken in order to make the function invariant to the location of the mass within the study region. Significance of aggregation or repulsion is determined using simulation envelopes. A simulation study is performed to inform researchers how the Aggregation about a Mass function performs under different types of aggregation. Finally, we apply the Aggregation about a Mass function to neuroscience as a novel analysis tool by examining the spatial pattern of neurotransmitter release sites as events about a neuron. PMID:29046865

On the abundance of extreme voids II: a survey of void mass functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chongchitnan, Siri; Hunt, Matthew, E-mail: s.chongchitnan@hull.ac.uk, E-mail: m.d.hunt@2012.hull.ac.uk

2017-03-01

The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation.

The maximal-density mass function for primordial black hole dark matter

NASA Astrophysics Data System (ADS)

Lehmann, Benjamin V.; Profumo, Stefano; Yant, Jackson

2018-04-01

The advent of gravitational wave astronomy has rekindled interest in primordial black holes (PBH) as a dark matter candidate. As there are many different observational probes of the PBH density across different masses, constraints on PBH models are dependent on the functional form of the PBH mass function. This complicates general statements about the mass functions allowed by current data, and, in particular, about the maximum total density of PBH. Numerical studies suggest that some forms of extended mass functions face tighter constraints than monochromatic mass functions, but they do not preclude the existence of a functional form for which constraints are relaxed. We use analytical arguments to show that the mass function which maximizes the fraction of the matter density in PBH subject to all constraints is a finite linear combination of monochromatic mass functions. We explicitly compute the maximum fraction of dark matter in PBH for different combinations of current constraints, allowing for total freedom of the mass function. Our framework elucidates the dependence of the maximum PBH density on the form of observational constraints, and we discuss the implications of current and future constraints for the viability of the PBH dark matter paradigm.

Hydrodynamical simulations of strong tides in astrophysical systems

NASA Astrophysics Data System (ADS)

Guillochon, James

2013-07-01

At the simplest level, gravitational sources are considered to be point-like and in solitude, with a radial force that falls off as r -2. In reality, all astrophysical objects aside from black holes are extended in space, and can be deformed by the tidal forces arising from the proximity of companion objects with large average densities. When these forces are weak, the response of an object to a tide can be through a decomposition into basis functions, but this approach fails when the tide is strong enough to deform an object by a distance equal to its own size. Under these circumstances, a hydrodynamical representation of the object is required to understand the true tidal response. In this thesis, we present a number of examples of physical systems in which tides dominate the dynamics. First, we consider the case of a star that encounters a supermassive black hole (SMBH) in a deeply penetrating encounter, resulting in a dramatic compression that produces shocks that would be observable in the X-ray. Second, we present the results of hydrodynamical simulations that demonstrate a new mechanism for igniting Type Ia supernovae from binary systems composed of two white dwarfs undergoing Roche-lobe overflow. Third, we investigate the survival prospects of giant planets that have been scattered into highly eccentricity orbits and are exposed to a strong tide applied by their parent star. Fourth, we systematically map the fallback rate resulting from the tidal disruptions of stars by SMBHs. Finally, we use what we have learned about the feeding rate to model determine the highest-likelihood model for an observed prototypical tidal disruption event.

Determination of the mass function of extra-galactic GMCs via NIR color maps. Testing the method in a disk-like geometry

NASA Astrophysics Data System (ADS)

Kainulainen, J.; Juvela, M.; Alves, J.

2007-06-01

The giant molecular clouds (GMCs) of external galaxies can be mapped with sub-arcsecond resolution using multiband observations in the near-infrared. However, the interpretation of the observed reddening and attenuation of light, and their transformation into physical quantities, is greatly hampered by the effects arising from the unknown geometry and the scattering of light by dust particles. We examine the relation between the observed near-infrared reddening and the column density of the dust clouds. In this paper we particularly assess the feasibility of deriving the mass function of GMCs from near-infrared color excess data. We perform Monte Carlo radiative transfer simulations with 3D models of stellar radiation and clumpy dust distributions. We include the scattered light in the models and calculate near-infrared color maps from the simulated data. The color maps are compared with the true line-of-sight density distributions of the models. We extract clumps from the color maps and compare the observed mass function to the true mass function. For the physical configuration chosen in this study, essentially a face-on geometry, the observed mass function is a non-trivial function of the true mass function with a large number of parameters affecting its exact form. The dynamical range of the observed mass function is confined to 103.5dots 105.5 M_⊙ regardless of the dynamical range of the true mass function. The color maps are more sensitive in detecting the high-mass end of the mass function, and on average the masses of clouds are underestimated by a factor of ˜ 10 depending on the parameters describing the dust distribution. A significant fraction of clouds is expected to remain undetected at all masses. The simulations show that the cloud mass function derived from JHK color excess data using simple foreground screening geometry cannot be regarded as a one-to-one tracer of the underlying mass function.

The emergence of the galactic stellar mass function from a non-universal IMF in clusters

NASA Astrophysics Data System (ADS)

Dib, Sami; Basu, Shantanu

2018-06-01

We investigate the dependence of a single-generation galactic mass function (SGMF) on variations in the initial stellar mass functions (IMF) of stellar clusters. We show that cluster-to-cluster variations of the IMF lead to a multi-component SGMF where each component in a given mass range can be described by a distinct power-law function. We also show that a dispersion of ≈0.3 M⊙ in the characteristic mass of the IMF, as observed for young Galactic clusters, leads to a low-mass slope of the SGMF that matches the observed Galactic stellar mass function even when the IMFs in the low-mass end of individual clusters are much steeper.

Proto-jet configurations in RADs orbiting a Kerr SMBH: symmetries and limiting surfaces

NASA Astrophysics Data System (ADS)

Pugliese, D.; Stuchlík, Z.

2018-05-01

Ringed accretion disks (RADs) are agglomerations of perfect-fluid tori orbiting around a single central attractor that could arise during complex matter inflows in active galactic nuclei. We focus our analysis to axi-symmetric accretion tori orbiting in the equatorial plane of a supermassive Kerr black hole; equilibrium configurations, possible instabilities, and evolutionary sequences of RADs were discussed in our previous works. In the present work we discuss special instabilities related to open equipotential surfaces governing the material funnels emerging at various regions of the RADs, being located between two or more individual toroidal configurations of the agglomerate. These open structures could be associated to proto-jets. Boundary limiting surfaces are highlighted, connecting the emergency of the jet-like instabilities with the black hole dimensionless spin. These instabilities are observationally significant for active galactic nuclei, being related to outflows of matter in jets emerging from more than one torus of RADs orbiting around supermassive black holes.

Unveiling the AGN activity in multiple SMBH systems observed with XMM-Newton

NASA Astrophysics Data System (ADS)

De Rosa, A.

2017-10-01

In this talk we will present results from the MAGNA (Multiple AGN Activity) project focused on the detection and study of multiple supermassive black hole systems. We investigate the physical properties (accretion rate and local environment) of multiple AGN candidates in interacting systems with respect to isolated sources with the goal to understand the mechanisms that trigger AGN activity in different stages of galaxy mergers. We present the study performed with SDSS and XMM data sets of 4 AGN pairs at separations of 20-70 kpc. XMM data allowed us to detect and characterize the AGN in all systems, by measuring the accretion and absorption properties of the sources. In each system at least one object is highly obscured, possibly Compton-thick, in agreement with the hypothesis that galaxy encounters are effective in driving gas inflow. One system however manifests the opposite behaviour showing a pair composed from an unobscured type 1 AGN and a Compton Thick AGN. The talk will reflect on broader implications of these findings.

A precise mass function in the excursion set approach

NASA Astrophysics Data System (ADS)

Del Popolo, Antonino

2017-04-01

In the present paper, using previous results from Del Popolo papers, we show how the mass function evolution can be obtained in the framework of a spherical collapse model, which has been modified to take account of dynamical friction, the cosmological constant, and angular momentum which proto-structures acquire through tidal interaction with neighbouring ones. We found an improved barrier which is in excellent agreement with simulations. The quoted barrier is used to calculated the mass function. In the case of the ΛCDM paradigm, our mass function is in good agreement (within some %) with the mass function of Klypin's Bolshoi simulation for the virial mass range 5 × 109 - 5 × 1014h-1M⊙, and 0 ≾ z ≿ 10. Similar agreement is obtained with Tinker's mass function, and Castorina's simulations.

Accurate mass and velocity functions of dark matter haloes

NASA Astrophysics Data System (ADS)

Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Klypin, Anatoly

2017-08-01

N-body cosmological simulations are an essential tool to understand the observed distribution of galaxies. We use the MultiDark simulation suite, run with the Planck cosmological parameters, to revisit the mass and velocity functions. At redshift z = 0, the simulations cover four orders of magnitude in halo mass from ˜1011M⊙ with 8783 874 distinct haloes and 532 533 subhaloes. The total volume used is ˜515 Gpc3, more than eight times larger than in previous studies. We measure and model the halo mass function, its covariance matrix w.r.t halo mass and the large-scale halo bias. With the formalism of the excursion-set mass function, we explicit the tight interconnection between the covariance matrix, bias and halo mass function. We obtain a very accurate (<2 per cent level) model of the distinct halo mass function. We also model the subhalo mass function and its relation to the distinct halo mass function. The set of models obtained provides a complete and precise framework for the description of haloes in the concordance Planck cosmology. Finally, we provide precise analytical fits of the Vmax maximum velocity function up to redshift z < 2.3 to push for the development of halo occupation distribution using Vmax. The data and the analysis code are made publicly available in the Skies and Universes data base.

Uncertainties and Systematic Effects on the estimate of stellar masses in high z galaxies

NASA Astrophysics Data System (ADS)

Salimbeni, S.; Fontana, A.; Giallongo, E.; Grazian, A.; Menci, N.; Pentericci, L.; Santini, P.

2009-05-01

We discuss the uncertainties and the systematic effects that exist in the estimates of the stellar masses of high redshift galaxies, using broad band photometry, and how they affect the deduced galaxy stellar mass function. We use at this purpose the latest version of the GOODS-MUSIC catalog. In particular, we discuss the impact of different synthetic models, of the assumed initial mass function and of the selection band. Using Chariot & Bruzual 2007 and Maraston 2005 models we find masses lower than those obtained from Bruzual & Chariot 2003 models. In addition, we find a slight trend as a function of the mass itself comparing these two mass determinations with that from Bruzual & Chariot 2003 models. As consequence, the derived galaxy stellar mass functions show diverse shapes, and their slope depends on the assumed models. Despite these differences, the overall results and scenario is observed in all these cases. The masses obtained with the assumption of the Chabrier initial mass function are in average 0.24 dex lower than those from the Salpeter assumption, at all redshifts, causing a shift of galaxy stellar mass function of the same amount. Finally, using a 4.5 μm-selected sample instead of a Ks-selected one, we add a new population of highly absorbed, dusty galaxies at z~=2-3 of relatively low masses, yielding stronger constraints on the slope of the galaxy stellar mass function at lower masses.

Deep luminosity function of the globular cluster M13

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drukier, G.A.; Fahlman, G.G.; Richter, H.B.

The luminosity function in a field of M13 at 14 core radii has been observed to M(V) = +12.0, and new theoretical, low-mass, stellar models appropriate to M13 are used to convert the function to a mass function which extends to M = 0.18 solar, within a factor of two of brown dwarf masses at this metal abundance. As the number of stars observed in each magnitude bin is still increasing at the limit of the data, the presence of stars with masses lower than 0.18 solar is probable. This result sets an upper limit of 0.18 solar mass formore » low-mass cutoffs in dynamical models of M13. No single power law mass function fits all the observations. The trend of the data supports the idea of a steep increase in the slope of the mass function for M less than 0.4 solar. The results imply that the total mass in low-mass stars in M13, and by implication elsewhere, is higher than was previously thought. 26 references.« less

Estimating initial contaminant mass based on fitting mass-depletion functions to contaminant mass discharge data: Testing method efficacy with SVE operations data

NASA Astrophysics Data System (ADS)

Mainhagu, J.; Brusseau, M. L.

2016-09-01

The mass of contaminant present at a site, particularly in the source zones, is one of the key parameters for assessing the risk posed by contaminated sites, and for setting and evaluating remediation goals and objectives. This quantity is rarely known and is challenging to estimate accurately. This work investigated the efficacy of fitting mass-depletion functions to temporal contaminant mass discharge (CMD) data as a means of estimating initial mass. Two common mass-depletion functions, exponential and power functions, were applied to historic soil vapor extraction (SVE) CMD data collected from 11 contaminated sites for which the SVE operations are considered to be at or close to essentially complete mass removal. The functions were applied to the entire available data set for each site, as well as to the early-time data (the initial 1/3 of the data available). Additionally, a complete differential-time analysis was conducted. The latter two analyses were conducted to investigate the impact of limited data on method performance, given that the primary mode of application would be to use the method during the early stages of a remediation effort. The estimated initial masses were compared to the total masses removed for the SVE operations. The mass estimates obtained from application to the full data sets were reasonably similar to the measured masses removed for both functions (13 and 15% mean error). The use of the early-time data resulted in a minimally higher variation for the exponential function (17%) but a much higher error (51%) for the power function. These results suggest that the method can produce reasonable estimates of initial mass useful for planning and assessing remediation efforts.

Does the HI Mass Function Vary with Environment?

NASA Astrophysics Data System (ADS)

Minchin, Robert F.

2017-01-01

Based on analysis of a large dataset from the ALFALFA survey, Jones et al. (2016) recently claimed that the slope of the HI mass function is constant across different galactic environments, defined by their density. They point out that this finding is “perplexing” given that many previous studies have found that the HI mass functions of groups of galaxies have flat slopes, while the general field has a relatively steep slope. I argue that the analysis of Jones et al., and similar analyses in the past, is flawed as they examine the HI mass function of the galaxies found in environments with a given density, summed across the survey, not the HI mass function actually present in the individual structures at that density. If the position of the knee in the HI mass function were to vary between these structures, then the slope of the HI mass function found by summing across all of the structures with a given density would be steeper than the slope actually found in the individual structures. For example, if a survey were to contain three groups of galaxies, all with flat HI mass functions, but with the ‘knee’, at the mass of the largest galaxy in the group, at 108, 109 and 1010 solar masses, then the summed HI mass function would appear to have a knee at 1010 solar masses and a steep slope below this, rather than the flat slope that is actually present in the individual environments. It is not possible, therefore, to say from the analysis of Jones et al. that there is no dependence of the HI mass function on environment. This scenario explains the “seemingly contradictory findings” of Jones et al. and the earlier studies of individual groups as being due to differences in what is being studies, without having to invoke methodological errors in the derivation of the HI mass function.The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association.

A deep X-ray view of the bare AGN Ark 120. IV. XMM-Newton and NuSTAR spectra dominated by two temperature (warm, hot) Comptonization processes

NASA Astrophysics Data System (ADS)

Porquet, D.; Reeves, J. N.; Matt, G.; Marinucci, A.; Nardini, E.; Braito, V.; Lobban, A.; Ballantyne, D. R.; Boggs, S. E.; Christensen, F. E.; Dauser, T.; Farrah, D.; Garcia, J.; Hailey, C. J.; Harrison, F.; Stern, D.; Tortosa, A.; Ursini, F.; Zhang, W. W.

2018-01-01

Context. The physical characteristics of the material closest to supermassive black holes (SMBHs) are primarily studied through X-ray observations. However, the origins of the main X-ray components such as the soft X-ray excess, the Fe Kα line complex, and the hard X-ray excess are still hotly debated. This is particularly problematic for active galactic nuclei (AGN) showing a significant intrinsic absorption, either warm or neutral, which can severely distort the observed continuum. Therefore, AGN with no (or very weak) intrinsic absorption along the line of sight, so-called "bare AGN", are the best targets to directly probe matter very close to the SMBH. Aims: We perform an X-ray spectral analysis of the brightest and cleanest bare AGN known so far, Ark 120, in order to determine the process(es) at work in the vicinity of the SMBH. Methods: We present spectral analyses of data from an extensive campaign observing Ark 120 in X-rays with XMM-Newton (4 × 120 ks, 2014 March 18-24), and NuSTAR (65.5 ks, 2014 March 22). Results: During this very deep X-ray campaign, the source was caught in a high-flux state similar to the earlier 2003 XMM-Newton observation, and about twice as bright as the lower-flux observation in 2013. The spectral analysis confirms the "softer when brighter" behavior of Ark 120. The four XMM-Newton/pn spectra are characterized by the presence of a prominent soft X-ray excess and a significant Fe Kα complex. The continuum is very similar above about 3 keV, while significant variability is present for the soft X-ray excess. We find that relativistic reflection from a constant-density, flat accretion disk cannot simultaneously produce the soft excess, broad Fe Kα complex, and hard X-ray excess. Instead, Comptonization reproduces the broadband (0.3-79 keV) continuum well, together with a contribution from a mildly relativistic disk reflection spectrum. Conclusions: During this 2014 observational campaign, the soft X-ray spectrum of Ark 120 below 0.5 keV was found to be dominated by Comptonization of seed photons from the disk by a warm (kTe 0.5 keV), optically-thick corona (τ 9). Above this energy, the X-ray spectrum becomes dominated by Comptonization from electrons in a hot optically thin corona, while the broad Fe Kα line and the mild Compton hump result from reflection off the disk at several tens of gravitational radii.

The Mass Function of Cosmic Structures

NASA Astrophysics Data System (ADS)

Audit, E.; Teyssier, R.; Alimi, J.-M.

We investigate some modifications to the Press and Schechter (1974) (PS) prescription resulting from shear and tidal effects. These modifications rely on more realistic treatments of the collapse process than the standard approach based on the spherical model. First, we show that the mass function resulting from a new approximate Lagrangian dynamic (Audit and Alimi, A&A 1996), contains more objects at high mass, than the classical PS mass function and is well fitted by a PS-like function with a threshold density of deltac ≍ 1.4. However, such a Lagrangian description can underestimate the epoch of structure formation since it defines it as the collapse of the first principal axis. We therefore suggest some analytical prescriptions, for computing the collapse time along the second and third principal axes, and we deduce the corresponding mass functions. The collapse along the third axis is delayed by the shear and the number of objects of high mass then decreases. Finally, we show that the shear also strongly affects the formation of low-mass halos. This dynamical effect implies a modification of the low-mass slope of the mass function and allows the reproduction of the observed luminosity function of field galaxies.

Luminosity Function of Faint Globular Clusters in M87

NASA Astrophysics Data System (ADS)

Waters, Christopher Z.; Zepf, Stephen E.; Lauer, Tod R.; Baltz, Edward A.; Silk, Joseph

2006-10-01

We present the luminosity function to very faint magnitudes for the globular clusters in M87, based on a 30 orbit Hubble Space Telescope (HST) WFPC2 imaging program. The very deep images and corresponding improved false source rejection allow us to probe the mass function further beyond the turnover than has been done before. We compare our luminosity function to those that have been observed in the past, and confirm the similarity of the turnover luminosity between M87 and the Milky Way. We also find with high statistical significance that the M87 luminosity function is broader than that of the Milky Way. We discuss how determining the mass function of the cluster system to low masses can constrain theoretical models of the dynamical evolution of globular cluster systems. Our mass function is consistent with the dependence of mass loss on the initial cluster mass given by classical evaporation, and somewhat inconsistent with newer proposals that have a shallower mass dependence. In addition, the rate of mass loss is consistent with standard evaporation models, and not with the much higher rates proposed by some recent studies of very young cluster systems. We also find that the mass-size relation has very little slope, indicating that there is almost no increase in the size of a cluster with increasing mass.

Predicting Functional Capacity From Measures of Muscle Mass in Postmenopausal Women.

PubMed

Orsatti, Fábio Lera; Nunes, Paulo Ricardo Prado; Souza, Aletéia de Paula; Martins, Fernanda Maria; de Oliveira, Anselmo Alves; Nomelini, Rosekeila Simões; Michelin, Márcia Antoniazi; Murta, Eddie Fernando Cândido

2017-06-01

Menopause increases body fat and decreases muscle mass and strength, which contribute to sarcopenia. The amount of appendicular muscle mass has been frequently used to diagnose sarcopenia. Different measures of appendicular muscle mass have been proposed. However, no studies have compared the most salient measure (appendicular muscle mass corrected by body fat) of the appendicular muscle mass to physical function in postmenopausal women. To examine the association of 3 different measurements of appendicular muscle mass (absolute, corrected by stature, and corrected by body fat) with physical function in postmenopausal women. Cross-sectional descriptive study. Outpatient geriatric and gynecological clinic. Forty-eight postmenopausal women with a mean age (standard deviation [SD]) of 62.1 ± 8.2 years, with mean (SD) length of menopause of 15.7 ± 9.8 years and mean (SD) body fat of 43.6% ± 9.8%. Not applicable. Appendicular muscle mass measure was measured with dual-energy x-ray absorptiometry. Physical function was measured by a functional capacity questionnaire, a short physical performance battery, and a 6 minute-walk test. Muscle quality (leg extensor strength to lower-body mineral-free lean mass ratio) and sum of z scores (sum of each physical function tests z score) were performed to provide a global index of physical function. The regression analysis showed that appendicular muscle mass corrected by body fat was the strongest predictor of physical function. Each increase in the standard deviation of appendicular muscle mass corrected by body fat was associated with a mean sum of z score increase of 59% (standard deviation), whereas each increase in absolute appendicular muscle mass and appendicular muscle mass corrected by stature were associated with a mean sum of z scores decrease of 23% and 36%, respectively. Muscle quality was associated with appendicular muscle mass corrected by body fat. These findings indicate that appendicular muscle mass corrected by body fat is a better predictor of physical function than the other measures of appendicular muscle mass in postmenopausal women. I. Copyright © 2017 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Comparison of muscle/lean mass measurement methods: correlation with functional and biochemical testing.

PubMed

Buehring, B; Siglinsky, E; Krueger, D; Evans, W; Hellerstein, M; Yamada, Y; Binkley, N

2018-03-01

DXA-measured lean mass is often used to assess muscle mass but has limitations. Thus, we compared DXA lean mass with two novel methods-bioelectric impedance spectroscopy and creatine (methyl-d3) dilution. The examined methodologies did not measure lean mass similarly and the correlation with muscle biomarkers/function varied. Muscle function tests predict adverse health outcomes better than lean mass measurement. This may reflect limitations of current mass measurement methods. Newer approaches, e.g., bioelectric impedance spectroscopy (BIS) and creatine (methyl-d3) dilution (D3-C), may more accurately assess muscle mass. We hypothesized that BIS and D3-C measured muscle mass would better correlate with function and bone/muscle biomarkers than DXA measured lean mass. Evaluations of muscle/lean mass, function, and serum biomarkers were obtained in older community-dwelling adults. Mass was assessed by DXA, BIS, and orally administered D3-C. Grip strength, timed up and go, and jump power were examined. Potential muscle/bone serum biomarkers were measured. Mass measurements were compared with functional and serum data using regression analyses; differences between techniques were determined by paired t tests. Mean (SD) age of the 112 (89F/23M) participants was 80.6 (6.0) years. The lean/muscle mass assessments were correlated (.57-.88) but differed (p < 0.0001) from one another with DXA total body less head being highest at 37.8 (7.3) kg, D3-C muscle mass at 21.1 (4.6) kg, and BIS total body intracellular water at 17.4 (3.5) kg. All mass assessment methods correlated with grip strength and jump power (R = 0.35-0.63, p < 0.0002), but not with gait speed or repeat chair rise. Lean mass measures were unrelated to the serum biomarkers measured. These three methodologies do not similarly measure muscle/lean mass and should not be viewed as being equivalent. Functional tests assessing maximal muscle strength/power (grip strength and jump power) correlated with all mass measures whereas gait speed was not. None of the selected serum measures correlated with mass. Efforts to optimize muscle mass assessment and identify their relationships with health outcomes are needed.

Bayesian inference of galaxy formation from the K-band luminosity function of galaxies: tensions between theory and observation

NASA Astrophysics Data System (ADS)

Lu, Yu; Mo, H. J.; Katz, Neal; Weinberg, Martin D.

2012-04-01

We conduct Bayesian model inferences from the observed K-band luminosity function of galaxies in the local Universe, using the semi-analytic model (SAM) of galaxy formation introduced in Lu et al. The prior distributions for the 14 free parameters include a large range of possible models. We find that some of the free parameters, e.g. the characteristic scales for quenching star formation in both high-mass and low-mass haloes, are already tightly constrained by the single data set. The posterior distribution includes the model parameters adopted in other SAMs. By marginalizing over the posterior distribution, we make predictions that include the full inferential uncertainties for the colour-magnitude relation, the Tully-Fisher relation, the conditional stellar mass function of galaxies in haloes of different masses, the H I mass function, the redshift evolution of the stellar mass function of galaxies and the global star formation history. Using posterior predictive checking with the available observational results, we find that the model family (i) predicts a Tully-Fisher relation that is curved; (ii) significantly overpredicts the satellite fraction; (iii) vastly overpredicts the H I mass function; (iv) predicts high-z stellar mass functions that have too many low-mass galaxies and too few high-mass ones and (v) predicts a redshift evolution of the stellar mass density and the star formation history that are in moderate disagreement. These results suggest that some important processes are still missing in the current model family, and we discuss a number of possible solutions to solve the discrepancies, such as interactions between galaxies and dark matter haloes, tidal stripping, the bimodal accretion of gas, preheating and a redshift-dependent initial mass function.

THE HALO MASS FUNCTION CONDITIONED ON DENSITY FROM THE MILLENNIUM SIMULATION: INSIGHTS INTO MISSING BARYONS AND GALAXY MASS FUNCTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Faltenbacher, A.; Finoguenov, A.; Drory, N.

2010-03-20

The baryon content of high-density regions in the universe is relevant to two critical unanswered questions: the workings of nurture effects on galaxies and the whereabouts of the missing baryons. In this paper, we analyze the distribution of dark matter and semianalytical galaxies in the Millennium Simulation to investigate these problems. Applying the same density field reconstruction schemes as used for the overall matter distribution to the matter locked in halos, we study the mass contribution of halos to the total mass budget at various background field densities, i.e., the conditional halo mass function. In this context, we present amore » simple fitting formula for the cumulative mass function accurate to {approx}<5% for halo masses between 10{sup 10} and 10{sup 15} h {sup -1} M{sub sun}. We find that in dense environments the halo mass function becomes top heavy and present corresponding fitting formulae for different redshifts. We demonstrate that the major fraction of matter in high-density fields is associated with galaxy groups. Since current X-ray surveys are able to nearly recover the universal baryon fraction within groups, our results indicate that the major part of the so-far undetected warm-hot intergalactic medium resides in low-density regions. Similarly, we show that the differences in galaxy mass functions with environment seen in observed and simulated data stem predominantly from differences in the mass distribution of halos. In particular, the hump in the galaxy mass function is associated with the central group galaxies, and the bimodality observed in the galaxy mass function is therefore interpreted as that of central galaxies versus satellites.« less

AGN host galaxy mass function in COSMOS. Is AGN feedback responsible for the mass-quenching of galaxies?

NASA Astrophysics Data System (ADS)

Bongiorno, A.; Schulze, A.; Merloni, A.; Zamorani, G.; Ilbert, O.; La Franca, F.; Peng, Y.; Piconcelli, E.; Mainieri, V.; Silverman, J. D.; Brusa, M.; Fiore, F.; Salvato, M.; Scoville, N.

2016-04-01

We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate, that is, λSAR, the distribution function (SARDF), up to z ~ 2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best-fit model characterizes the SARDF as a double power-law with mass-dependent but redshift-independent break, whose low λSAR slope flattens with increasing redshift while the normalization increases. This implies that for a given stellar mass, higher λSAR objects have a peak in their space density at earlier epoch than the lower λSAR objects, following and mimicking the well-known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with an almost constant M∗⋆ and a low-mass slope α that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that up to log (M⋆/M⊙) ~ 11.5, the ratio of AGN host galaxies to star-forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate subclasses with a previously published phenomenological model prediction for the "transient" population, which are galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, that is, M⋆ > 1010.7 M⊙, feedback from luminous AGN (log Lbol ≳ 46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

The Most Massive Galaxies and Black Holes Allowed by ΛCDM

NASA Astrophysics Data System (ADS)

Behroozi, Peter; Silk, Joseph

2018-04-01

Given a galaxy's stellar mass, its host halo mass has a lower limit from the cosmic baryon fraction and known baryonic physics. At z > 4, galaxy stellar mass functions place lower limits on halo number densities that approach expected ΛCDM halo mass functions. High-redshift galaxy stellar mass functions can thus place interesting limits on number densities of massive haloes, which are otherwise very difficult to measure. Although halo mass functions at z < 8 are consistent with observed galaxy stellar masses if galaxy baryonic conversion efficiencies increase with redshift, JWST and WFIRST will more than double the redshift range over which useful constraints are available. We calculate maximum galaxy stellar masses as a function of redshift given expected halo number densities from ΛCDM. We apply similar arguments to black holes. If their virial mass estimates are accurate, number density constraints alone suggest that the quasars SDSS J1044-0125 and SDSS J010013.02+280225.8 likely have black hole mass — stellar mass ratios higher than the median z = 0 relation, confirming the expectation from Lauer bias. Finally, we present a public code to evaluate the probability of an apparently ΛCDM-inconsistent high-mass halo being detected given the combined effects of multiple surveys and observational errors.

Binary Systems and the Initial Mass Function

NASA Astrophysics Data System (ADS)

Malkov, O. Yu.

2017-07-01

In the present paper we discuss advantages and disadvantages of binary stars, which are important for star formation history determination. We show that to make definite conclusions of the initial mass function shape, it is necessary to study binary population well enough to correct the luminosity function for unresolved binaries; to construct the mass-luminosity relation based on wide binaries data, and to separate observational mass functions of primaries, of secondaries, and of unresolved binaries.

The mass function and dynamical mass of young star clusters: why their initial crossing-time matters crucially

NASA Astrophysics Data System (ADS)

Parmentier, Geneviève; Baumgardt, Holger

2012-12-01

We highlight the impact of cluster-mass-dependent evolutionary rates upon the evolution of the cluster mass function during violent relaxation, that is, while clusters dynamically respond to the expulsion of their residual star-forming gas. Mass-dependent evolutionary rates arise when the mean volume density of cluster-forming regions is mass-dependent. In that case, even if the initial conditions are such that the cluster mass function at the end of violent relaxation has the same shape as the embedded-cluster mass function (i.e. infant weight-loss is mass-independent), the shape of the cluster mass function does change transiently during violent relaxation. In contrast, for cluster-forming regions of constant mean volume density, the cluster mass function shape is preserved all through violent relaxation since all clusters then evolve at the same mass-independent rate. On the scale of individual clusters, we model the evolution of the ratio of the dynamical mass to luminous mass of a cluster after gas expulsion. Specifically, we map the radial dependence of the time-scale for a star cluster to return to equilibrium. We stress that fields of view a few pc in size only, typical of compact clusters with rapid evolutionary rates, are likely to reveal cluster regions which have returned to equilibrium even if the cluster experienced a major gas expulsion episode a few Myr earlier. We provide models with the aperture and time expressed in units of the initial half-mass radius and initial crossing-time, respectively, so that our results can be applied to clusters with initial densities, sizes, and apertures different from ours.

Chandra X-Ray Spectroscopic Imaging of Sagittarius A* and the Central Parsec of the Galaxy

NASA Astrophysics Data System (ADS)

Baganoff, F. K.; Maeda, Y.; Morris, M.; Bautz, M. W.; Brandt, W. N.; Cui, W.; Doty, J. P.; Feigelson, E. D.; Garmire, G. P.; Pravdo, S. H.; Ricker, G. R.; Townsley, L. K.

2003-07-01

We report the results of the first-epoch observation with the ACIS-I instrument on the Chandra X-Ray Observatory of Sagittarius A* (Sgr A*), the compact radio source associated with the supermassive black hole (SMBH) at the dynamical center of the Milky Way. This observation produced the first X-ray (0.5-7 keV) spectroscopic image with arcsecond resolution of the central 17'×17' (40pc×40pc) of the Galaxy. We report the discovery of an X-ray source, CXOGC J174540.0-290027, coincident with Sgr A* within 0.27"+/-0.18". The probability of a false match is estimated to be <~0.5%. The spectrum is well fitted either by an absorbed power law with photon index Γ~2.7 or by an absorbed optically thin thermal plasma with kT~1.9 keV and column density NH~1×1023 cm-2. The observed flux in the 2-10 keV band is ~1.3×10-13 ergs cm-2 s-1, and the absorption-corrected luminosity is ~2.4×1033 ergs s-1. The X-ray emission at the position of Sgr A* is extended, with an intrinsic size of ~1.4" (FWHM), consistent with the Bondi accretion radius for a 2.6×106 Msolar black hole. A compact component within the source flared by up to a factor of 3 over a period of ~1 hr at the start of the observation. The search for Kα line emission from iron was inconclusive, yielding an upper limit on the equivalent width of 2.2 keV. Several potential stellar origins for the X-ray emission at Sgr A* are considered, but we conclude that the various properties of the source favor accretion onto the SMBH as the origin for the bulk of the emission. These data are inconsistent with ``standard'' advection-dominated accretion flow (ADAF) models or Bondi models, unless the accretion rate from stellar winds is much lower than anticipated. The central parsec of the Galaxy contains an ~1.3 keV plasma with electron density ne~26η-1/2fcm-3, where ηf is the filling factor. This plasma should supply ~10-6 Msolar yr-1 of material to the accretion flow at the Bondi radius, whereas measurements of linear polarization at 150 GHz and above limit the accretion rate near the event horizon to <~10-8 Msolar yr-1, assuming an equipartition magnetic field. Taken together, the X-ray and radio results imply that outflows or convection are playing a role in ADAF models and subequipartition magnetic fields in Bondi models, or else the X-ray emission must be generated predominantly via the synchrotron self-Compton (SSC) process. The measured extent of the source and the detection of short timescale variability are evidence that the emission from Sgr A* contains both thermal and nonthermal emission components at comparable levels. We also discuss the complex structure of the X-ray emission from the Sgr A radio complex and along the Galactic plane. Morphological evidence is presented that Sgr A* and the H II region Sgr A West lie within the hot plasma in the central cavity of Sgr A East, which we interpret as a supernova remnant that may have passed through the position of the SMBH, leading to a period of increased activity that ended within the past ~300 yr. Similarly, we have discovered bright clumps of X-ray emission located on opposite sides of the Galactic plane, along a line passing through the central parsec of the Galaxy. The arrangement of these lobes suggests that Sgr A* may have experienced an earlier period of increased activity lasting several thousand years during which it expelled hot gas in a bipolar outflow oriented roughly perpendicular to the Galactic plane. Additionally, we present an analysis of stellar emission within the central parsec of the Galaxy.

On the mass function of stars growing in a flocculent medium

NASA Astrophysics Data System (ADS)

Maschberger, Th.

2013-12-01

Stars form in regions of very inhomogeneous densities and may have chaotic orbital motions. This leads to a time variation of the accretion rate, which will spread the masses over some mass range. We investigate the mass distribution functions that arise from fluctuating accretion rates in non-linear accretion, ṁ ∝ mα. The distribution functions evolve in time and develop a power-law tail attached to a lognormal body, like in numerical simulations of star formation. Small fluctuations may be modelled by a Gaussian and develop a power-law tail ∝ m-α at the high-mass side for α > 1 and at the low-mass side for α < 1. Large fluctuations require that their distribution is strictly positive, for example, lognormal. For positive fluctuations the mass distribution function develops the power-law tail always at the high-mass hand side, independent of α larger or smaller than unity. Furthermore, we discuss Bondi-Hoyle accretion in a supersonically turbulent medium, the range of parameters for which non-linear stochastic growth could shape the stellar initial mass function, as well as the effects of a distribution of initial masses and growth times.

The ACS Survey of Galactic Globular Clusters. VIII. Effects of Environment on Globular Cluster Global Mass Functions

NASA Astrophysics Data System (ADS)

Paust, Nathaniel E. Q.; Reid, I. Neill; Piotto, Giampaolo; Aparicio, Antonio; Anderson, Jay; Sarajedini, Ata; Bedin, Luigi R.; Chaboyer, Brian; Dotter, Aaron; Hempel, Maren; Majewski, Steven; Marín-Franch, A.; Milone, Antonino; Rosenberg, Alfred; Siegel, Michael

2010-02-01

We have used observations obtained as part of the Hubble Space Telescope/ACS Survey of Galactic Globular Clusters to construct global present-day mass functions for 17 globular clusters utilizing multi-mass King models to extrapolate from our observations to the global cluster behavior. The global present-day mass functions for these clusters are well matched by power laws from the turnoff, ≈0.8 M sun, to 0.2-0.3 M sun on the lower main sequence. The slopes of those power-law fits, α, have been correlated with an extensive set of intrinsic and extrinsic cluster properties to investigate which parameters may influence the form of the present-day mass function. We do not confirm previous suggestions of correlations between α and either metallicity or Galactic location. However, we do find a strong statistical correlation with the related parameters central surface brightness, μ V , and inferred central density, ρ0. The correlation is such that clusters with denser cores (stronger binding energy) tend to have steeper mass functions (a higher proportion of low-mass stars), suggesting that dynamical evolution due to external interactions may have played a key role in determining α. Thus, the present-day mass function may owe more to nurture than to nature. Detailed modeling of external dynamical effects is therefore a requisite for determining the initial mass function for Galactic globular clusters.

First constraints on the stellar mass function of star-forming clumps at the peak of cosmic star formation

NASA Astrophysics Data System (ADS)

Dessauges-Zavadsky, Miroslava; Adamo, Angela

2018-06-01

Star-forming clumps dominate the rest-frame ultraviolet morphology of galaxies at the peak of cosmic star formation. If turbulence driven fragmentation is the mechanism responsible for their formation, we expect their stellar mass function to follow a power-law of slope close to -2. We test this hypothesis performing the first analysis of the stellar mass function of clumps hosted in galaxies at z ˜ 1 - 3.5. The sample is gathered from the literature with similar detection thresholds and stellar masses determined in a homogeneous way. To overcome the small number statistics per galaxy (each galaxy hosts up to a few tens of clumps only), we combine all high-redshift clumps. The resulting clump mass function follows a power-law of slope ˜-1.7 and flattens at masses below 2 × 107 M⊙. By means of randomly sampled clump populations, drawn out of a power-law mass function of slope -2, we test the effect of combining small clump populations, detection limits of the surveys, and blending on the mass function. Our numerical exercise reproduces all the features observed in the real clump mass function confirming that it is consistent with a power-law of slope ≃ -2. This result supports the high-redshift clump formation through fragmentation in a similar fashion as in local galaxies, but under different gas conditions.

New Insights into AGN Mass Outflows: Detailed Study of the Spectral Properties of NGC 4151

NASA Astrophysics Data System (ADS)

Denes Couto, Jullianna

2017-08-01

Active Galactic Nuclei (AGNs) exist in a few percent of all massive galaxies. It is believed that AGNs are powered by accretion of matter onto a supermassive black hole (SMBH), generating in the process huge amounts of radiation that span the entire electromagnetic spectrum. In turn, this also triggers the so-called AGN Feedback phenomenon, by inducing the formation of accretion disk winds (or outflows) that accelerate highly ionized gas outwards and affect the intergalactic medium of the host galaxy, reducing star formation rates and preventing bulge growth. It has been suggested that a dominant component of mass outflows is observable in the X-rays, and there are a limited number of detailed studies of single objects for which the relation between outflows and power of the central engine can be determined directly. The Seyfert 1.5 galaxy NGC 4151 is a great study candidate, given its proximity (14.077 Mpc, z = 0.0033), X-ray brightness and orientation. Over the past decades, it has been the target of many single and multiwavelength observations, and its heavily absorbed X-ray spectrum and complex absorption features have been extensively stud- ied and characterized. I have investigated the relationship between the long term X-ray spectral variability in and its intrinsic absorption, by comparing our 2014 simultaneous ultraviolet/X-Ray observations taken with Hubble Space Telescope Imaging Spectrometer (STIS) Echelle and Chandra High Energy Transmission Grating Spectrometer (HETGS) with archival observations from Chandra, XMM-Newton and Suzaku. The observations were divided into "high" and "low" flux states, with the low states showing strong and unabsorbed extended emission at energies below 2 keV. The X-ray model consists of a broken powerlaw, neutral reflection and two dominant absorption components, a high and a low ionization component, which are present in all epochs. The model fittings suggest that the absorbers are very stable, with the principal changes in the intrinsic absorption resulting from a response to the variable strength of the ionizing continuum. However, the low states show evidence of larger column densities in one or both of the absorbers. Among plausible explanations for the column increase, I discuss the possibility of an expanding/contracting X-ray corona. The higher ionization component is consistent with being part of a magnetohydrodynamic (MHD) wind, while the lower is possibly radiatively driven, which suggests that at a sufficiently large radial distance there could be a break point between MHD-dominated and radiatively driven outflows. The final model of the absorbed continuum was used as input to the analysis of the soft X-ray emission, which arises in an extended medium of several hundred parsecs. There is evidence of at least four components of gas, with different ionization states and different kinematic profiles. I calculated global covering factors, total masses, mass outflow rates and kinetic luminosity estimates for each component. The models results indicate that it is unlikely that the X-ray wind could contribute significantly to a large scale feedback on NGC 4151. However, this might not be the case for more powerful and energetic sources.

The most massive galaxies and black holes allowed by ΛCDM

NASA Astrophysics Data System (ADS)

Behroozi, Peter; Silk, Joseph

2018-07-01

Given a galaxy's stellar mass, its host halo mass has a lower limit from the cosmic baryon fraction and known baryonic physics. At z> 4, galaxy stellar mass functions place lower limits on halo number densities that approach expected Lambda Cold Dark Matter halo mass functions. High-redshift galaxy stellar mass functions can thus place interesting limits on number densities of massive haloes, which are otherwise very difficult to measure. Although halo mass functions at z < 8 are consistent with observed galaxy stellar masses if galaxy baryonic conversion efficiencies increase with redshift, JWST(James Webb Space Telescope) and WFIRST(Wide-Field InfraRed Survey Telescope) will more than double the redshift range over which useful constraints are available. We calculate maximum galaxy stellar masses as a function of redshift given expected halo number densities from ΛCDM. We apply similar arguments to black holes. If their virial mass estimates are accurate, number density constraints alone suggest that the quasars SDSS J1044-0125 and SDSS J010013.02+280225.8 likely have black hole mass to stellar mass ratios higher than the median z = 0 relation, confirming the expectation from Lauer bias. Finally, we present a public code to evaluate the probability of an apparently ΛCDM-inconsistent high-mass halo being detected given the combined effects of multiple surveys and observational errors.

What do Simulations Predict for the Galaxy Stellar Mass Function and its Evolution in Different Environments?

NASA Astrophysics Data System (ADS)

Vulcani, Benedetta; De Lucia, Gabriella; Poggianti, Bianca M.; Bundy, Kevin; More, Surhud; Calvi, Rosa

2014-06-01

We present a comparison between the observed galaxy stellar mass function and the one predicted from the De Lucia & Blaizot semi-analytic model applied to the Millennium Simulation, for cluster satellites and galaxies in the field (meant as a wide portion of the sky, including all environments), in the local universe (z ~ 0.06), and at intermediate redshift (z ~ 0.6), with the aim to shed light on the processes which regulate the mass distribution in different environments. While the mass functions in the field and in its finer environments (groups, binary, and single systems) are well matched in the local universe down to the completeness limit of the observational sample, the model overpredicts the number of low-mass galaxies in the field at z ~ 0.6 and in clusters at both redshifts. Above M * = 1010.25 M ⊙, it reproduces the observed similarity of the cluster and field mass functions but not the observed evolution. Our results point out two shortcomings of the model: an incorrect treatment of cluster-specific environmental effects and an overefficient galaxy formation at early times (as already found by, e.g., Weinmann et al.). Next, we consider only simulations. Also using the Guo et al. model, we find that the high-mass end of the mass functions depends on halo mass: only very massive halos host massive galaxies, with the result that their mass function is flatter. Above M * = 109.4 M ⊙, simulations show an evolution in the number of the most massive galaxies in all environments. Mass functions obtained from the two prescriptions are different, however, results are qualitatively similar, indicating that the adopted methods to model the evolution of central and satellite galaxies still have to be better implemented in semi-analytic models.

The young star cluster population of M51 with LEGUS - I. A comprehensive study of cluster formation and evolution

NASA Astrophysics Data System (ADS)

Messa, M.; Adamo, A.; Östlin, G.; Calzetti, D.; Grasha, K.; Grebel, E. K.; Shabani, F.; Chandar, R.; Dale, D. A.; Dobbs, C. L.; Elmegreen, B. G.; Fumagalli, M.; Gouliermis, D. A.; Kim, H.; Smith, L. J.; Thilker, D. A.; Tosi, M.; Ubeda, L.; Walterbos, R.; Whitmore, B. C.; Fedorenko, K.; Mahadevan, S.; Andrews, J. E.; Bright, S. N.; Cook, D. O.; Kahre, L.; Nair, P.; Pellerin, A.; Ryon, J. E.; Ahmad, S. D.; Beale, L. P.; Brown, K.; Clarkson, D. A.; Guidarelli, G. C.; Parziale, R.; Turner, J.; Weber, M.

2018-01-01

Recently acquired WFC3 UV (F275W and F336W) imaging mosaics under the Legacy Extragalactic UV Survey (LEGUS), combined with archival ACS data of M51, are used to study the young star cluster (YSC) population of this interacting system. Our newly extracted source catalogue contains 2834 cluster candidates, morphologically classified to be compact and uniform in colour, for which ages, masses and extinction are derived. In this first work we study the main properties of the YSC population of the whole galaxy, considering a mass-limited sample. Both luminosity and mass functions follow a power-law shape with slope -2, but at high luminosities and masses a dearth of sources is observed. The analysis of the mass function suggests that it is best fitted by a Schechter function with slope -2 and a truncation mass at 1.00 ± 0.12 × 105 M⊙. Through Monte Carlo simulations, we confirm this result and link the shape of the luminosity function to the presence of a truncation in the mass function. A mass limited age function analysis, between 10 and 200 Myr, suggests that the cluster population is undergoing only moderate disruption. We observe little variation in the shape of the mass function at masses above 1 × 104 M⊙ over this age range. The fraction of star formation happening in the form of bound clusters in M51 is ∼ 20 per cent in the age range 10-100 Myr and little variation is observed over the whole range from 1 to 200 Myr.

Evolutionary Description of Giant Molecular Cloud Mass Functions on Galactic Disks

NASA Astrophysics Data System (ADS)

Kobayashi, Masato I. N.; Inutsuka, Shu-ichiro; Kobayashi, Hiroshi; Hasegawa, Kenji

2017-02-01

Recent radio observations show that giant molecular cloud (GMC) mass functions noticeably vary across galactic disks. High-resolution magnetohydrodynamics simulations show that multiple episodes of compression are required for creating a molecular cloud in the magnetized interstellar medium. In this article, we formulate the evolution equation for the GMC mass function to reproduce the observed profiles, for which multiple compressions are driven by a network of expanding shells due to H II regions and supernova remnants. We introduce the cloud-cloud collision (CCC) terms in the evolution equation in contrast to previous work (Inutsuka et al.). The computed time evolution suggests that the GMC mass function slope is governed by the ratio of GMC formation timescale to its dispersal timescale, and that the CCC effect is limited only in the massive end of the mass function. In addition, we identify a gas resurrection channel that allows the gas dispersed by massive stars to regenerate GMC populations or to accrete onto pre-existing GMCs. Our results show that almost all of the dispersed gas contributes to the mass growth of pre-existing GMCs in arm regions whereas less than 60% contributes in inter-arm regions. Our results also predict that GMC mass functions have a single power-law exponent in the mass range <105.5 {M}⊙ (where {M}⊙ represents the solar mass), which is well characterized by GMC self-growth and dispersal timescales. Measurement of the GMC mass function slope provides a powerful method to constrain those GMC timescales and the gas resurrecting factor in various environments across galactic disks.

Time evolution of giant molecular cloud mass functions with cloud-cloud collisions and gas resurrection in various environments

NASA Astrophysics Data System (ADS)

Kobayashi, M. I. N.; Inutsuka, S.; Kobayashi, H.; Hasegawa, K.

We formulate the evolution equation for the giant molecular cloud (GMC) mass functions including self-growth of GMCs through the thermal instability, self-dispersal due to massive stars born in GMCs, cloud-cloud collisions (CCCs), and gas resurrection that replenishes the minimum-mass GMC population. The computed time evolutions obtained from this formulation suggest that the slope of GMC mass function in the mass range <105.5 Mȯ is governed by the ratio of GMC formation timescale to its dispersal timescale, and that the CCC process modifies only the massive end of the mass function. Our results also suggest that most of the dispersed gas contributes to the mass growth of pre-existing GMCs in arm regions whereas less than 60 per cent contributes in inter-arm regions.

Characteristics of transonic spherical symmetric accretion flow in Schwarzschild-de Sitter and Schwarzschild anti-de Sitter backgrounds, in pseudo-general relativistic paradigm

NASA Astrophysics Data System (ADS)

Ghosh, Shubhrangshu; Banik, Prabir

2015-07-01

In this paper, we present a complete work on steady state spherically symmetric Bondi type accretion flow in the presence of cosmological constant (Λ) in both Schwarzschild-de Sitter (SDS) and Schwarzschild anti-de Sitter (SADS) backgrounds considering an isolated supermassive black hole (SMBH), with the inclusion of a simple radiative transfer scheme, in the pseudo-general relativistic paradigm. We do an extensive analysis on the transonic behavior of the Bondi type accretion flow onto the cosmological BHs including a complete analysis of the global parameter space and the stability of flow, and do a complete study of the global family of solutions for a generic polytropic flow. Bondi type accretion flow in SADS background renders multiplicity in its transonic behavior with inner "saddle" type and outer "center" type sonic points, with the transonic solutions forming closed loops or contours. There is always a limiting value for ∣Λ∣ up to which we obtain valid stationary transonic solutions, which correspond to both SDS and SADS geometries; this limiting value moderately increases with the increasing radiative efficiency of the flow, especially correspond to Bondi type accretion flow in SADS background. Repulsive Λ suppresses the Bondi accretion rate by an order of magnitude for relativistic Bondi type accretion flow for a certain range in temperature, and with a marginal increase in the Bondi accretion rate if the corresponding accretion flow occurs in SADS background. However, for a strongly radiative Bondi type accretion flow with high mass accretion rate, the presence of cosmological constant do not much influence the corresponding Bondi accretion rate of the flow. Our analysis show that the relic cosmological constant has a substantial effect on Bondi type accretion flow onto isolated SMBHs and their transonic solutions beyond length-scale of kiloparsecs, especially if the Bondi type accretion occurs onto the host supergiant ellipticals or central dominant (CD) galaxies directly from ambient intercluster medium (ICM). However, for high mass accretion rate, the influence of cosmological constant on Bondi accretion dynamics, generically, diminishes. As active galactic nuclei (AGN)/ICM feedback can be advertently linked to Bondi type spherical accretion, any proper modeling of AGN feedback or megaparsecs-scale jet dynamics or accretion flow from ICM onto the central regions of host galaxies should take into account the relevant information of repulsive Λ, especially in context to supergiant elliptical galaxies or CD galaxies present in rich galaxy clusters. This could also explore the feasibility to limit the value of Λ, from the kinematics in local galactic-scales.

Evolution of the Black Hole Mass Function in Star Clusters from Multiple Mergers

NASA Astrophysics Data System (ADS)

Christian, Pierre; Mocz, Philip; Loeb, Abraham

2018-05-01

We investigate the effects of black hole (BH) mergers in star clusters on the black hole mass function (BHMF). As BHs are not produced in pair-instability supernovae, it is suggested that there is a dearth of high-mass stellar BHs. This dearth generates a gap in the upper end of the BHMF. Meanwhile, parameter fitting of X-ray binaries suggests the existence of a gap in the mass function under 5 solar masses. We show, through evolving a coagulation equation, that BH mergers can appreciably fill the upper mass gap, and that the lower mass gap generates potentially observable features at larger mass scales. We also explore the importance of ejections in such systems and whether dynamical clusters can be formation sites of intermediate-mass BH seeds.

The insignificant evolution of the richness-mass relation of galaxy clusters

NASA Astrophysics Data System (ADS)

Andreon, S.; Congdon, P.

2014-08-01

We analysed the richness-mass scaling of 23 very massive clusters at 0.15 < z < 0.55 with homogenously measured weak-lensing masses and richnesses within a fixed aperture of 0.5 Mpc radius. We found that the richness-mass scaling is very tight (the scatter is <0.09 dex with 90% probability) and independent of cluster evolutionary status and morphology. This implies a close association between infall and evolution of dark matter and galaxies in the central region of clusters. We also found that the evolution of the richness-mass intercept is minor at most, and, given the minor mass evolution across the studied redshift range, the richness evolution of individual massive clusters also turns out to be very small. Finally, it was paramount to account for the cluster mass function and the selection function. Ignoring them would lead to larger biases than the (otherwise quoted) errors. Our study benefits from: a) weak-lensing masses instead of proxy-based masses thereby removing the ambiguity between a real trend and one induced by an accounted evolution of the used mass proxy; b) the use of projected masses that simplify the statistical analysis thereby not requiring consideration of the unknown covariance induced by the cluster orientation/triaxiality; c) the use of aperture masses as they are free of the pseudo-evolution of mass definitions anchored to the evolving density of the Universe; d) a proper accounting of the sample selection function and of the Malmquist-like effect induced by the cluster mass function; e) cosmological simulations for the computation of the cluster mass function, its evolution, and the mass growth of each individual cluster.

THE ABUNDANCE OF X-SHAPED RADIO SOURCES: IMPLICATIONS FOR THE GRAVITATIONAL WAVE BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David H.; Saripalli, Lakshmi; Subrahmanyan, Ravi, E-mail: roberts@brandeis.edu

Coalescence of supermassive black holes (SMBHs) in galaxy mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers that X-shaped radio galaxies are signposts of such coalescences and that their abundance might be used to predict the magnitude of the GWB. In Roberts et al. we presented radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources thatmore » were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations (“spin flips”), much smaller than the 7% suggested by Leahy and Parma. Thus, the associated GWB may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB.« less

The XMM-SERVS Survey: first results in the 5 deg^2 XMM-LSS region

NASA Astrophysics Data System (ADS)

Chen, Chien-Ting; Brandt, William; Luo, Bin; X-SERVS team

2018-01-01

We present an X-ray source catalog obtained with XMM-Newton in the XMM-LSS region as part of the X-SERVS survey (XMM-SERVS-LSS), which aims to expand the parameter space of current X-ray surveys with medium-deep X-ray observations in multiple large fields with superb multiwavelength coverage. Within the 5 deg$^2$ XMM-SERVS-LSS field, we combine the 1.3 Ms XMM observations allocated at XMM AO-15 with archival data, and identified 5218 X-ray sources of which 2400 are new sources. We reach $1.2\\times10^{-15}$ erg s$^{-1} cm$^{-1}$ for 50\\% of the area, which is comparable to the XMM-COSMOS survey but with 2.5 times more sources. We also present multiwavelength identifications, basic photometric properties, and spectroscopic redshifts obtained from the literature. These data, combined with the existing data from COSMOS, will enable a wide range of science on AGN evolution, including studying SMBH growth across the full range of cosmic environments and minimizing cosmic variance.

Functional Gene Diversity and Metabolic Potential of the Microbial Community in an Estuary-Shelf Environment

PubMed Central

Wang, Yu; Zhang, Rui; He, Zhili; Van Nostrand, Joy D.; Zheng, Qiang; Zhou, Jizhong; Jiao, Nianzhi

2017-01-01

Microbes play crucial roles in various biogeochemical processes in the ocean, including carbon (C), nitrogen (N), and phosphorus (P) cycling. Functional gene diversity and the structure of the microbial community determines its metabolic potential and therefore its ecological function in the marine ecosystem. However, little is known about the functional gene composition and metabolic potential of bacterioplankton in estuary areas. The East China Sea (ECS) is a dynamic marginal ecosystem in the western Pacific Ocean that is mainly affected by input from the Changjiang River and the Kuroshio Current. Here, using a high-throughput functional gene microarray (GeoChip), we analyzed the functional gene diversity, composition, structure, and metabolic potential of microbial assemblages in different ECS water masses. Four water masses determined by temperature and salinity relationship showed different patterns of functional gene diversity and composition. Generally, functional gene diversity [Shannon–Weaner’s H and reciprocal of Simpson’s 1/(1-D)] in the surface water masses was higher than that in the bottom water masses. The different presence and proportion of functional genes involved in C, N, and P cycling among the bacteria of the different water masses showed different metabolic preferences of the microbial populations in the ECS. Genes involved in starch metabolism (amyA and nplT) showed higher proportion in microbial communities of the surface water masses than of the bottom water masses. In contrast, a higher proportion of genes involved in chitin degradation was observed in microorganisms of the bottom water masses. Moreover, we found a higher proportion of nitrogen fixation (nifH), transformation of hydroxylamine to nitrite (hao) and ammonification (gdh) genes in the microbial communities of the bottom water masses compared with those of the surface water masses. The spatial variation of microbial functional genes was significantly correlated with salinity, temperature, and chlorophyll based on canonical correspondence analysis, suggesting a significant influence of hydrologic conditions on water microbial communities. Our data provide new insights into better understanding of the functional potential of microbial communities in the complex estuarine-coastal environmental gradient of the ECS. PMID:28680420

Stellar mass and velocity functions of galaxies. Backward evolution and the fate of Milky Way siblings

NASA Astrophysics Data System (ADS)

Boissier, S.; Buat, V.; Ilbert, O.

2010-11-01

Context. In recent years, stellar mass functions of both star-forming and quiescent galaxies have been observed at different redshifts in various fields. In addition, star formation rate (SFR) distributions (e.g. in the form of far infrared luminosity functions) were also obtained. Taken together, they offer complementary pieces of information concerning the evolution of galaxies. Aims: We attempt in this paper to check the consistency of the observed stellar mass functions, SFR functions, and the cosmic SFR density with simple backward evolutionary models. Methods: Starting from observed stellar mass functions for star-forming galaxies, we use backwards models to predict the evolution of a number of quantities, such as the SFR function, the cosmic SFR density and the velocity function. Because the velocity is a parameter attached to a galaxy during its history (contrary to the stellar mass), this approach allows us to quantify the number density evolution of galaxies of a given velocity, e.g. of the Milky Way siblings. Results: Observations suggest that the stellar mass function of star-forming galaxies is constant between redshift 0 and 1. To reproduce this result, we must quench star formation in a number of star-forming galaxies. The stellar mass function of these “quenched” galaxies is consistent with available data concerning the increase in the population of quiescent galaxies in the same redshift interval. The stellar mass function of quiescent galaxies is then mainly determined by the distribution of active galaxies that must stop star formation, with a modest mass redistribution during mergers. The cosmic SFR density and the evolution of the SFR functions are recovered relatively well, although they provide some clues to a minor evolution of the stellar mass function of star forming galaxies at the lowest redshifts. We thus consider that we have obtained in a simple way a relatively consistent picture of the evolution of galaxies at intermediate redshifts. If this picture is correct, 50% of the Milky-Way sisters (galaxies with the same velocity as our Galaxy, i.e. 220 km s-1) have quenched their star formation since redshift 1 (and an even higher fraction for higher velocities). We discuss the processes that might be responsible for this transformation.

Lower Cognitive Function in Older Patients with Lower Muscle Strength and Muscle Mass.

PubMed

van Dam, Romee; Van Ancum, Jeanine M; Verlaan, Sjors; Scheerman, Kira; Meskers, Carel G M; Maier, Andrea B

2018-06-18

Low muscle strength and muscle mass are associated with adverse outcomes in older hospitalized patients. The aim of this study was to assess the association between cognitive functioning and muscle strength and muscle mass in hospitalized older patients. This prospective inception cohort included 378 patients aged 70 years or older. At admission patients were assessed for cognitive functioning by use of the Six-Item Cognitive Impairment Test (6-CIT). Muscle strength and muscle mass were assessed using handheld dynamometry and segmental multifrequency bioelectrical impedance analysis, within 48 h after admission and on day 7, or earlier on the day of discharge. The data of 371 patients (mean age ± standard deviation 80.1 ± 6.4 years, 49.3% female) were available for analyses. The median (interquartile range) 6-CIT score was 4 (0-8) points. At admission, lower cognitive functioning was associated with lower muscle strength, lower skeletal muscle mass (SMM), lower appendicular lean mass, and lower SMM index. Cognitive functioning was not associated with change in muscle strength and muscle mass during hospitalization. This study further strengthens evidence for an association between lower cognitive functioning and lower muscle strength and muscle mass, but without a further decline during hospitalization. © 2018 The Author(s) Published by S. Karger AG, Basel.

Mass functional for initial data in 4 +1 -dimensional spacetime

NASA Astrophysics Data System (ADS)

Alaee, Aghil; Kunduri, Hari K.

2014-12-01

We consider a broad class of asymptotically flat, maximal initial data sets satisfying the vacuum constraint equations, admitting two commuting rotational symmetries. We construct a mass functional for "t -ϕi"-symmetric data which evaluates to the Arnowitt-Deser-Misner mass. We then show that R ×U (1 )2 -invariant solutions of the vacuum Einstein equations are critical points of this functional amongst this class of data. We demonstrate the positivity of this functional for a class of rod structures which include the Myers-Perry initial data. The construction is a natural extension of Dain's mass functional to D =5 , although several new features arise.

Understanding the build-up of SMBH and Galaxies

NASA Astrophysics Data System (ADS)

Carrera, Francisco; Georgakakis, Antonis; Ueda, Yoshihiro; Akylas, Thanassis; Lanzuisi, Giorgio; Castello, N.

2015-09-01

One of the main open questions in modern Astrophysics is understanding the coupled growth of supermassive black holes by accretion and their host galaxies via star formation, from their peak at redshifts z~ 1-4 to the present time. The generic scenario proposed involves an early phase of intense black hole growth that takes place behind large obscuring columns of inflowing dust and gas clouds. It is postulated that this is followed by a blow-out stage during which some form of AGN feedback controls the fate of the interstellar medium and hence, the evolution of the galaxy. X-rays are essential for testing this scenario as they uniquely probe AGN at both the early heavily obscured stage and the later blow-out phase. X-ray spectral analysis can identify the smoking gun evidence of heavily obscured black hole growth (e.g. intense iron Kalpha line). It therefore provides the most robust method for compiling clean samples of deeply shrouded AGN with well-defined selection functions and unbiased determinations of their intrinsic properties (accretion luminosity, obscuring column). X-rays are also the best window for studying in detail AGN feedback. This process ultimately originates in the innermost regions close to the supermassive black hole and is dominated, in terms of energy and mass flux, by highly ionised material that remains invisible at other wavelengths. The most important epoch for investigating the relation between AGN and galaxies is the redshift range z~1-4, when most black holes and stars we see in the present-day Universe were put in place. Unfortunately, exhaustive efforts with current high-energy telescopes only scrape the tip of the iceberg of the most obscured AGN population. Moreover, Xray studies of the incidence, nature and energetics of AGN feedback are limited to the local Universe. The Athena observatory will provide the technological leap required for a breakthrough in our understanding of AGN and galaxy evolution at the heyday of the Universe. The excellent survey capabilities of Athena/WFI (effective area, angular resolution, field of view) will allow to measure the incidence of feedback in the shape of warm absorbers and Ultra Fast Outflows among the general population of AGN, as well as to complete the census of black hole growth by detecting and characterising significant samples of the most heavily obscured (including Compton thick) AGN, to redshifts z~3-4. The outstanding spectral throughput and resolution of Athena/X-IFU will permit measuring the energetics of those outflows to assess their influence on their host galaxies. The demographics of the heavily obscured and outflowing populations relative to their hosts are fundamental for understanding how major black hole growth events relate to the build-up of galaxies.

The joint fit of the BHMF and ERDF for the BAT AGN Sample

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Koss, Michael; Ricci, Claudio; Trakhtenbrot, Benny; Oh, Kyuseok; Schawinski, Kevin; Lamperti, Isabella

2018-01-01

A natural product of an AGN survey is the AGN luminosity function. This statistical measure describes the distribution of directly measurable AGN luminosities. Intrinsically, the shape of the luminosity function depends on the distribution of black hole masses and Eddington ratios. To constrain these fundamental AGN properties, the luminosity function thus has to be disentangled into the black hole mass and Eddington ratio distribution function. The BASS survey is unique as it allows such a joint fit for a large number of local AGN, is unbiased in terms of obscuration in the X-rays and provides black hole masses for type-1 and type-2 AGN. The black hole mass function at z ~ 0 represents an essential baseline for simulations and black hole growth models. The normalization of the Eddington ratio distribution function directly constrains the AGN fraction. Together, the BASS AGN luminosity, black hole mass and Eddington ratio distribution functions thus provide a complete picture of the local black hole population.

A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papastergis, Emmanouil; Huang, Shan; Giovanelli, Riccardo

We use both an H I-selected and an optically selected galaxy sample to directly measure the abundance of galaxies as a function of their 'baryonic' mass (stars + atomic gas). Stellar masses are calculated based on optical data from the Sloan Digital Sky Survey and atomic gas masses are calculated using atomic hydrogen (H I) emission line data from the Arecibo Legacy Fast ALFA survey. By using the technique of abundance matching, we combine the measured baryonic function of galaxies with the dark matter halo mass function in a {Lambda}CDM universe, in order to determine the galactic baryon fraction asmore » a function of host halo mass. We find that the baryon fraction of low-mass halos is much smaller than the cosmic value, even when atomic gas is taken into account. We find that the galactic baryon deficit increases monotonically with decreasing halo mass, in contrast with previous studies which suggested an approximately constant baryon fraction at the low-mass end. We argue that the observed baryon fractions of low-mass halos cannot be explained by reionization heating alone, and that additional feedback mechanisms (e.g., supernova blowout) must be invoked. However, the outflow rates needed to reproduce our result are not easily accommodated in the standard picture of galaxy formation in a {Lambda}CDM universe.« less

Low-mass stars in globular clusters. III. The mass function of 47 Tucanae.

NASA Astrophysics Data System (ADS)

de Marchi, G.; Paresce, F.

1995-12-01

We have used the WFPC2 on board HST to investigate the stellar population in a field located 4'6 E of the center of the globular cluster 47 Tuc (NGC 104), close to the half-mass radius, through wide band imaging at 606 and 812nm. A total of ~3000 stars are accurately classified by two-color photometry to form a color-magnitude diagram extending down to a limiting magnitude m_814_=~m_I_=~24. A rich cluster main sequence is detected spanning the range from m_814_=~18 through m_814_=~23, where it spreads considerably due to the increasing photometric uncertainty and galaxy contamination. A secondary sequence of objects is also detected, parallel to the main sequence, as expected for a population of binary stars. The measured binary fraction in the range 195%. The main sequence luminosity function obtained from the observed CMD increases with decreasing luminosity following a power-law trend with index α=~0.15 in the range 5

Exact analytic solution of position-dependent mass Schrödinger equation

NASA Astrophysics Data System (ADS)

Rajbongshi, Hangshadhar

2018-03-01

Exact analytic solution of position-dependent mass Schrödinger equation is generated by using extended transformation, a method of mapping a known system into a new system equipped with energy eigenvalues and corresponding wave functions. First order transformation is performed on D-dimensional radial Schrödinger equation with constant mass by taking trigonometric Pöschl-Teller potential as known system. The exactly solvable potentials with position-dependent mass generated for different choices of mass functions through first order transformation are also taken as known systems in the second order transformation performed on D-dimensional radial position-dependent mass Schrödinger equation. The solutions are fitted for "Zhu and Kroemer" ordering of ambiguity. All the wave functions corresponding to nonzero energy eigenvalues are normalizable. The new findings are that the normalizability condition of the wave functions remains independent of mass functions, and some of the generated potentials show a family relationship among themselves where power law potentials also get related to non-power law potentials and vice versa through the transformation.

Sensory stimulation augments the effects of massed practice training in persons with tetraplegia.

PubMed

Beekhuizen, Kristina S; Field-Fote, Edelle C

2008-04-01

To compare functional changes and cortical neuroplasticity associated with hand and upper extremity use after massed (repetitive task-oriented practice) training, somatosensory stimulation, massed practice training combined with somatosensory stimulation, or no intervention, in persons with chronic incomplete tetraplegia. Participants were randomly assigned to 1 of 4 groups: massed practice training combined with somatosensory peripheral nerve stimulation (MP+SS), somatosensory peripheral nerve stimulation only (SS), massed practice training only (MP), and no intervention (control). University medical school setting. Twenty-four subjects with chronic incomplete tetraplegia. Intervention sessions were 2 hours per session, 5 days a week for 3 weeks. Massed practice training consisted of repetitive practice of functional tasks requiring skilled hand and upper-extremity use. Somatosensory stimulation consisted of median nerve stimulation with intensity set below motor threshold. Pre- and post-testing assessed changes in functional hand use (Jebsen-Taylor Hand Function Test), functional upper-extremity use (Wolf Motor Function Test), pinch grip strength (key pinch force), sensory function (monofilament testing), and changes in cortical excitation (motor evoked potential threshold). The 3 groups showed significant improvements in hand function after training. The MP+SS and SS groups had significant improvements in upper-extremity function and pinch strength compared with the control group, but only the MP+SS group had a significant change in sensory scores compared with the control group. The MP+SS and MP groups had greater change in threshold measures of cortical excitability. People with chronic incomplete tetraplegia obtain functional benefits from massed practice of task-oriented skills. Somatosensory stimulation appears to be a valuable adjunct to training programs designed to improve hand and upper-extremity function in these subjects.

The Galaxy mass function up to z =4 in the GOODS-MUSIC sample: into the epoch of formation of massive galaxies

NASA Astrophysics Data System (ADS)

Fontana, A.; Salimbeni, S.; Grazian, A.; Giallongo, E.; Pentericci, L.; Nonino, M.; Fontanot, F.; Menci, N.; Monaco, P.; Cristiani, S.; Vanzella, E.; de Santis, C.; Gallozzi, S.

2006-12-01

Aims.The goal of this work is to measure the evolution of the Galaxy Stellar Mass Function and of the resulting Stellar Mass Density up to redshift ≃4, in order to study the assembly of massive galaxies in the high redshift Universe. Methods: .We have used the GOODS-MUSIC catalog, containing 3000 Ks-selected galaxies with multi-wavelength coverage extending from the U band to the Spitzer 8 μm band, of which 27% have spectroscopic redshifts and the remaining fraction have accurate photometric redshifts. On this sample we have applied a standard fitting procedure to measure stellar masses. We compute the Galaxy Stellar Mass Function and the resulting Stellar Mass Density up to redshift ≃4, taking into proper account the biases and incompleteness effects. Results: .Within the well known trend of global decline of the Stellar Mass Density with redshift, we show that the decline of the more massive galaxies may be described by an exponential timescale of ≃6 Gyr up to z≃ 1.5, and proceeds much faster thereafter, with an exponential timescale of ≃0.6 Gyr. We also show that there is some evidence for a differential evolution of the Galaxy Stellar Mass Function, with low mass galaxies evolving faster than more massive ones up to z≃ 1{-}1.5 and that the Galaxy Stellar Mass Function remains remarkably flat (i.e. with a slope close to the local one) up to z≃ 1{-}1.3. Conclusions: .The observed behaviour of the Galaxy Stellar Mass Function is consistent with a scenario where about 50% of present-day massive galaxies formed at a vigorous rate in the epoch between redshift 4 and 1.5, followed by a milder evolution until the present-day epoch.

The assessment and impact of sarcopenia in lung cancer: a systematic literature review.

PubMed

Collins, Jemima; Noble, Simon; Chester, John; Coles, Bernadette; Byrne, Anthony

2014-01-02

There is growing awareness of the relationship between sarcopenia (loss of muscle mass and function), and outcomes in cancer, making it a potential target for future therapies. In order to inform future research and practice, we undertook a systematic review of factors associated with loss of muscle mass, and the relationship between muscle function and muscle mass in lung cancer, a common condition associated with poor outcomes. We conducted a computerised systematic literature search on five databases. Studies were included if they explored muscle mass as an outcome measure in patients with lung cancer, and were published in English. Secondary care. Patients with lung cancer. Factors associated with loss of muscle mass and muscle function, or sarcopenia, and the clinical impact thereof in patients with lung cancer. We reviewed 5726 citations, and 35 articles were selected for analysis. Sarcopenia, as defined by reduced muscle mass alone, was found to be very prevalent in patients with lung cancer, regardless of body mass index, and where present was associated with poorer functional status and overall survival. There were diverse studies exploring molecular and metabolic factors in the development of loss of muscle mass; however, the precise mechanisms that contribute to sarcopenia and cachexia remain uncertain. The effect of nutritional supplements and ATP infusions on muscle mass showed conflicting results. There are very limited data on the correlation between degree of sarcopenia and muscle function, which has a non-linear relationship in older non-cancer populations. Loss of muscle mass is a significant contributor to morbidity in patients with lung cancer. Loss of muscle mass and function may predate clinically overt cachexia, underlining the importance of evaluating sarcopenia, rather than weight loss alone. Understanding this relationship and its associated factors will provide opportunities for focused intervention to improve clinical outcomes.

A test of the cross-scale resilience model: Functional richness in Mediterranean-climate ecosystems

USGS Publications Warehouse

Wardwell, D.A.; Allen, Craig R.; Peterson, G.D.; Tyre, A.J.

2008-01-01

Ecological resilience has been proposed to be generated, in part, in the discontinuous structure of complex systems. Environmental discontinuities are reflected in discontinuous, aggregated animal body mass distributions. Diversity of functional groups within body mass aggregations (scales) and redundancy of functional groups across body mass aggregations (scales) has been proposed to increase resilience. We evaluate that proposition by analyzing mammalian and avian communities of Mediterranean-climate ecosystems. We first determined that body mass distributions for each animal community were discontinuous. We then calculated the variance in richness of function across aggregations in each community, and compared observed values with distributions created by 1000 simulations using a null of random distribution of function, with the same n, number of discontinuities and number of functional groups as the observed data. Variance in the richness of functional groups across scales was significantly lower in real communities than in simulations in eight of nine sites. The distribution of function across body mass aggregations in the animal communities we analyzed was non-random, and supports the contentions of the cross-scale resilience model. ?? 2007 Elsevier B.V. All rights reserved.

The Effects of Single and Close Binary Evolution on the Stellar Mass Function

NASA Astrophysics Data System (ADS)

Schneider, R. N. F.; Izzard, G. R.; de Mink, S.; Langer, N., Stolte, A., de Koter, A.; Gvaramadze, V. V.; Hussmann, B.; Liermann, A.; Sana, H.

2013-06-01

Massive stars are almost exclusively born in star clusters, where stars in a cluster are expected to be born quasi-simultaneously and with the same chemical composition. The distribution of their birth masses favors lower over higher stellar masses, such that the most massive stars are rare, and the existence of an stellar upper mass limit is still debated. The majority of massive stars are born as members of close binary systems and most of them will exchange mass with a close companion during their lifetime. We explore the influence of single and binary star evolution on the high mass end of the stellar mass function using a rapid binary evolution code. We apply our results to two massive Galactic star clusters and show how the shape of their mass functions can be used to determine cluster ages and comment on the stellar upper mass limit in view of our new findings.

Black hole mass function from gravitational wave measurements

NASA Astrophysics Data System (ADS)

Kovetz, Ely D.; Cholis, Ilias; Breysse, Patrick C.; Kamionkowski, Marc

2017-05-01

We examine how future gravitational-wave measurements from merging black holes (BHs) can be used to infer the shape of the black-hole mass function, with important implications for the study of star formation and evolution and the properties of binary BHs. We model the mass function as a power law, inherited from the stellar initial mass function, and introduce lower and upper mass cutoff parametrizations in order to probe the minimum and maximum BH masses allowed by stellar evolution, respectively. We initially focus on the heavier BH in each binary, to minimize model dependence. Taking into account the experimental noise, the mass measurement errors and the uncertainty in the redshift dependence of the merger rate, we show that the mass function parameters, as well as the total rate of merger events, can be measured to <10 % accuracy within a few years of advanced LIGO observations at its design sensitivity. This can be used to address important open questions such as the upper limit on the stellar mass which allows for BH formation and to confirm or refute the currently observed mass gap between neutron stars and BHs. In order to glean information on the progenitors of the merging BH binaries, we then advocate the study of the two-dimensional mass distribution to constrain parameters that describe the two-body system, such as the mass ratio between the two BHs, in addition to the merger rate and mass function parameters. We argue that several years of data collection can efficiently probe models of binary formation, and show, as an example, that the hypothesis that some gravitational-wave events may involve primordial black holes can be tested. Finally, we point out that in order to maximize the constraining power of the data, it may be worthwhile to lower the signal-to-noise threshold imposed on each candidate event and amass a larger statistical ensemble of BH mergers.

ON THE IMF IN A TRIGGERED STAR FORMATION CONTEXT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Tingtao; Huang, Chelsea X.; Lin, D. N. C.

2015-07-20

The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It is generally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores that have a core mass function (CMF) with a similar shape. In the low-mass end, these mass functions increase with mass, albeit the sample may be somewhat incomplete; in the high-mass end, the mass functions decrease with mass. There is an offset in the turn-over mass between the two mass distributions. The stellar mass for the IMF peak is lowermore » than the corresponding core mass for the CMF peak in the Pipe Nebula by about a factor of three. Smaller offsets are found between the IMF and the CMFs in other nebulae. We suggest that the offset is likely induced during a starburst episode of global star formation which is triggered by the formation of a few O/B stars in the multi-phase media, which naturally emerged through the onset of thermal instability in the cloud-core formation process. We consider the scenario that the ignition of a few massive stars photoionizes the warm medium between the cores, increases the external pressure, reduces their Bonnor–Ebert mass, and triggers the collapse of some previously stable cores. We quantitatively reproduce the IMF in the low-mass end with the assumption of additional rotational fragmentation.« less

[Anthropometry, body composition and functional limitations in the elderly].

PubMed

Arroyo, Patricia; Lera, Lydia; Sánchez, Hugo; Bunout, Daniel; Santos, José Luis; Albala, Cecilia

2007-07-01

Functional limitations limit the independence and jeopardize the quality of life of elderly subjects. To assess the association between anthropometric measures and body composition with functional limitations in community-living older people. Cross-sectional survey of 377 people > or = 6 5 years old (238 women), randomly selected from the SABE/Chile project. Complete anthropometric measurements were done. Handgrip muscle strength was measured using dynamometers. Body composition was determined using Dual-Energy X-Ray Absorptiometry. Functional limitations were assessed using self reported and observed activities. Body mass index was strongly associated with fat mass (men r =0.87; women r =0.91) and with lean mass (men r =0.55; women r =0.62). Males had significantly greater lean mass (48.9 kg vs 34.9 kg), and bone mass than females (2.6 kg vs 1.8 kg) and women had higher fat mass than men (26.3 kg vs 22.9 kg). The prevalence of functional limitations was high, affecting more women than men (63.7% vs 37.5%, p <0.01). Functional limitations were associated with lower handgrip strength in both sexes. In the multiple regression models, with functional limitations as dependent variable and anthropometric measures as contributing variables, only hand grip strength had a significant association (negative) with functional limitations in both genders. Age was also a significant risk factor for functional limitations among women. Hand grip strength was strongly and inversely associated with functional limitations. Handgrip dynamometry is an easy, cheap and low time-consuming indicator for the assessment of functional limitations and the evaluation of geriatric interventions aimed to improve functional ability.

The f ( R ) halo mass function in the cosmic web

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braun-Bates, F. von; Winther, H.A.; Alonso, D.

An important indicator of modified gravity is the effect of the local environment on halo properties. This paper examines the influence of the local tidal structure on the halo mass function, the halo orientation, spin and the concentration-mass relation. We use the excursion set formalism to produce a halo mass function conditional on large-scale structure. Our simple model agrees well with simulations on large scales at which the density field is linear or weakly non-linear. Beyond this, our principal result is that f ( R ) does affect halo abundances, the halo spin parameter and the concentration-mass relationship in anmore » environment-independent way, whereas we find no appreciable deviation from \\text(ΛCDM) for the mass function with fixed environment density, nor the alignment of the orientation and spin vectors of the halo to the eigenvectors of the local cosmic web. There is a general trend for greater deviation from \\text(ΛCDM) in underdense environments and for high-mass haloes, as expected from chameleon screening.« less

dftools: Distribution function fitting

NASA Astrophysics Data System (ADS)

Obreschkow, Danail

2018-05-01

dftools, written in R, finds the most likely P parameters of a D-dimensional distribution function (DF) generating N objects, where each object is specified by D observables with measurement uncertainties. For instance, if the objects are galaxies, it can fit a mass function (D=1), a mass-size distribution (D=2) or the mass-spin-morphology distribution (D=3). Unlike most common fitting approaches, this method accurately accounts for measurement in uncertainties and complex selection functions.

An Empirical Mass Function Distribution

NASA Astrophysics Data System (ADS)

Murray, S. G.; Robotham, A. S. G.; Power, C.

2018-03-01

The halo mass function, encoding the comoving number density of dark matter halos of a given mass, plays a key role in understanding the formation and evolution of galaxies. As such, it is a key goal of current and future deep optical surveys to constrain the mass function down to mass scales that typically host {L}\\star galaxies. Motivated by the proven accuracy of Press–Schechter-type mass functions, we introduce a related but purely empirical form consistent with standard formulae to better than 4% in the medium-mass regime, {10}10{--}{10}13 {h}-1 {M}ȯ . In particular, our form consists of four parameters, each of which has a simple interpretation, and can be directly related to parameters of the galaxy distribution, such as {L}\\star . Using this form within a hierarchical Bayesian likelihood model, we show how individual mass-measurement errors can be successfully included in a typical analysis, while accounting for Eddington bias. We apply our form to a question of survey design in the context of a semi-realistic data model, illustrating how it can be used to obtain optimal balance between survey depth and angular coverage for constraints on mass function parameters. Open-source Python and R codes to apply our new form are provided at http://mrpy.readthedocs.org and https://cran.r-project.org/web/packages/tggd/index.html respectively.

Memory effects in nanoparticle dynamics and transport

NASA Astrophysics Data System (ADS)

Sanghi, Tarun; Bhadauria, Ravi; Aluru, N. R.

2016-10-01

In this work, we use the generalized Langevin equation (GLE) to characterize and understand memory effects in nanoparticle dynamics and transport. Using the GLE formulation, we compute the memory function and investigate its scaling with the mass, shape, and size of the nanoparticle. It is observed that changing the mass of the nanoparticle leads to a rescaling of the memory function with the reduced mass of the system. Further, we show that for different mass nanoparticles it is the initial value of the memory function and not its relaxation time that determines the "memory" or "memoryless" dynamics. The size and the shape of the nanoparticle are found to influence both the functional-form and the initial value of the memory function. For a fixed mass nanoparticle, increasing its size enhances the memory effects. Using GLE simulations we also investigate and highlight the role of memory in nanoparticle dynamics and transport.

Effects of functional group mass variance on vibrational properties and thermal transport in graphene

DOE PAGES

Lindsay, L.; Kuang, Y.

2017-03-13

Intrinsic thermal resistivity critically depends on features of phonon dispersions dictated by harmonic interatomic forces and masses. We present the effects of functional group mass variance on vibrational properties and thermal conductivity (κ ) of functionalized graphene from first principles calculations. We also use graphane, a buckled graphene backbone with covalently bonded Hydrogen atoms on both sides, as the base material and vary the mass of the Hydrogen atoms to simulate the effect of mass variance from other functional groups. We find non-monotonic behavior of κ with increasing mass of the functional group and an unusual cross-over from acoustic-dominated tomore » optic-dominated thermal transport behavior. We connect this cross-over to changes in the phonon dispersion with varying mass which suppress acoustic phonon velocities, but also give unusually high velocity optic modes. Further, we show that out-of-plane acoustic vibrations contribute significantly more to thermal transport than in-plane acoustic modes despite breaking of a reflection symmetry based scattering selection rule responsible for their large contributions in graphene. Our work demonstrates the potential for manipulation and engineering of thermal transport properties in two dimensional materials toward targeted applications.« less

Effects of functional group mass variance on vibrational properties and thermal transport in graphene

NASA Astrophysics Data System (ADS)

Lindsay, L.; Kuang, Y.

2017-03-01

Intrinsic thermal resistivity critically depends on features of phonon dispersions dictated by harmonic interatomic forces and masses. Here we present the effects of functional group mass variance on vibrational properties and thermal conductivity (κ ) of functionalized graphene from first-principles calculations. We use graphane, a buckled graphene backbone with covalently bonded hydrogen atoms on both sides, as the base material and vary the mass of the hydrogen atoms to simulate the effect of mass variance from other functional groups. We find nonmonotonic behavior of κ with increasing mass of the functional group and an unusual crossover from acoustic-dominated to optic-dominated thermal transport behavior. We connect this crossover to changes in the phonon dispersion with varying mass which suppress acoustic phonon velocities, but also give unusually high velocity optic modes. Further, we show that out-of-plane acoustic vibrations contribute significantly more to thermal transport than in-plane acoustic modes despite breaking of a reflection-symmetry-based scattering selection rule responsible for their large contributions in graphene. This work demonstrates the potential for manipulation and engineering of thermal transport properties in two-dimensional materials toward targeted applications.

Effects of functional group mass variance on vibrational properties and thermal transport in graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindsay, L.; Kuang, Y.

Intrinsic thermal resistivity critically depends on features of phonon dispersions dictated by harmonic interatomic forces and masses. We present the effects of functional group mass variance on vibrational properties and thermal conductivity (κ ) of functionalized graphene from first principles calculations. We also use graphane, a buckled graphene backbone with covalently bonded Hydrogen atoms on both sides, as the base material and vary the mass of the Hydrogen atoms to simulate the effect of mass variance from other functional groups. We find non-monotonic behavior of κ with increasing mass of the functional group and an unusual cross-over from acoustic-dominated tomore » optic-dominated thermal transport behavior. We connect this cross-over to changes in the phonon dispersion with varying mass which suppress acoustic phonon velocities, but also give unusually high velocity optic modes. Further, we show that out-of-plane acoustic vibrations contribute significantly more to thermal transport than in-plane acoustic modes despite breaking of a reflection symmetry based scattering selection rule responsible for their large contributions in graphene. Our work demonstrates the potential for manipulation and engineering of thermal transport properties in two dimensional materials toward targeted applications.« less

The Low-Mass Stellar Initial Mass Function: Ultra-Faint Dwarf Galaxies Revisited

NASA Astrophysics Data System (ADS)

Platais, Imants

2017-08-01

The stellar Initial Mass Function plays a critical role in the evolution of the baryonic content of the Universe. The form of the low-mass IMF - stars of mass less than the solar mass - determines the fraction of baryons locked up for a Hubble time, and thus indicates how gas and metals are cycled through galaxies. Inferences from resolved stellar populations, where the low-mass luminosity function and associated IMF can be derived from direct star counts, generally favor an invariant and universal IMF. However, a recent study of ultra-faint dwarf galaxies Hercules and Leo IV indicates a bottom-lite IMF, over a narrow range of stellar mass (only 0.55-0.75 M_sun), correlated with the internal velocity dispersion and/or metallicity. We propose to obtain ultra-deep imaging for a significantly closer ultra-faint dwarf, Bootes I, which will allow us to construct the luminosity function down to M_v=+10 (equivalent to 0.35 solar mass). We will also re-analyze the HST archival observations for the Hercules and Leo IV dwarfs using the same updated techniques as for Bootes I. The combined datasets should provide a reliable answer to the question of how variable is the low-mass stellar IMF.

An exactly solvable model of polymerization

NASA Astrophysics Data System (ADS)

Lushnikov, A. A.

2017-08-01

This paper considers the evolution of a polydisperse polymerizing system comprising g1,g2 … - mers carrying ϕ1,ϕ2 … functional groups reacting with one another and binding the g-mers together. In addition, the g-mers are assumed to be added at random by one at a time with a known rate depending on their mass g and functionality ϕ . Assuming that the rate of binding of two g-mers is proportional to the product of the numbers of nonreacted functional groups the kinetic equation for the distribution of clusters (g-mers) over their mass and functionalities is formulated and then solved by applying the generating function method. In contrast to existing approaches this kinetic equation operates with the efficiencies proportional to the product of the numbers of active functional groups in the clusters rather than to the product of their masses. The evolution process is shown to reveal a phase transition: the emergence of a giant linked cluster (the gel) whose mass is comparable to the total mass of the whole polymerizing system. The time dependence of the moments of the distribution of linked components over their masses and functionalities is investigated. The polymerization process terminates by forming a residual spectrum of sol particles in addition to the gel.

Relationships of leaf dark respiration to leaf nitrogen, specific leaf area and leaf life-span: a test across biomes and functional groups.

PubMed

Reich, Peter B; Walters, Michael B; Ellsworth, David S; Vose, James M; Volin, John C; Gresham, Charles; Bowman, William D

1998-05-01

Based on prior evidence of coordinated multiple leaf trait scaling, we hypothesized that variation among species in leaf dark respiration rate (R d ) should scale with variation in traits such as leaf nitrogen (N), leaf life-span, specific leaf area (SLA), and net photosynthetic capacity (A max ). However, it is not known whether such scaling, if it exists, is similar among disparate biomes and plant functional types. We tested this idea by examining the interspecific relationships between R d measured at a standard temperature and leaf life-span, N, SLA and A max for 69 species from four functional groups (forbs, broad-leafed trees and shrubs, and needle-leafed conifers) in six biomes traversing the Americas: alpine tundra/subalpine forest, Colorado; cold temperate forest/grassland, Wisconsin; cool temperate forest, North Carolina; desert/shrubland, New Mexico; subtropical forest, South Carolina; and tropical rain forest, Amazonas, Venezuela. Area-based R d was positively related to area-based leaf N within functional groups and for all species pooled, but not when comparing among species within any site. At all sites, mass-based R d (R d-mass ) decreased sharply with increasing leaf life-span and was positively related to SLA and mass-based A max and leaf N (leaf N mass ). These intra-biome relationships were similar in shape and slope among sites, where in each case we compared species belonging to different plant functional groups. Significant R d-mass -N mass relationships were observed in all functional groups (pooled across sites), but the relationships differed, with higher R d at any given leaf N in functional groups (such as forbs) with higher SLA and shorter leaf life-span. Regardless of biome or functional group, R d-mass was well predicted by all combinations of leaf life-span, N mass and/or SLA (r 2 ≥ 0.79, P < 0.0001). At any given SLA, R d-mass rises with increasing N mass and/or decreasing leaf life-span; and at any level of N mass , R d-mass rises with increasing SLA and/or decreasing leaf life-span. The relationships between R d and leaf traits observed in this study support the idea of a global set of predictable interrelationships between key leaf morphological, chemical and metabolic traits.

On the scatter in the relation between stellar mass and halo mass: random or halo formation time dependent?

NASA Astrophysics Data System (ADS)

Wang, Lan; De Lucia, Gabriella; Weinmann, Simone M.

2013-05-01

The empirical traditional halo occupation distribution (HOD) model of Wang et al. fits, by construction, both the stellar mass function and correlation function of galaxies in the local Universe. In contrast, the semi-analytical models of De Lucia & Blazoit (hereafter DLB07) and Guo et al. (hereafter Guo11), built on the same dark matter halo merger trees than the empirical model, still have difficulties in reproducing these observational data simultaneously. We compare the relations between the stellar mass of galaxies and their host halo mass in the three models, and find that they are different. When the relations are rescaled to have the same median values and the same scatter as in Wang et al., the rescaled DLB07 model can fit both the measured galaxy stellar mass function and the correlation function measured in different galaxy stellar mass bins. In contrast, the rescaled Guo11 model still overpredicts the clustering of low-mass galaxies. This indicates that the detail of how galaxies populate the scatter in the stellar mass-halo mass relation does play an important role in determining the correlation functions of galaxies. While the stellar mass of galaxies in the Wang et al. model depends only on halo mass and is randomly distributed within the scatter, galaxy stellar mass depends also on the halo formation time in semi-analytical models. At fixed value of infall mass, galaxies that lie above the median stellar mass-halo mass relation reside in haloes that formed earlier, while galaxies that lie below the median relation reside in haloes that formed later. This effect is much stronger in Guo11 than in DLB07, which explains the overclustering of low mass galaxies in Guo11. Assembly bias in Guo11 model might be overly strong. Nevertheless, in case that a significant assembly bias indeed exists in the real Universe, one needs to use caution when applying current HOD and abundance matching models that employ the assumption of random scatter in the relation between stellar and halo mass.

Quark Mass Functions and Pion Structure in the Covariant Spectator Theory

DOE PAGES

Biernat, Elmar P.; Gross, Franz; Pena, Teresa; ...

2018-05-24

The Covariant Spectator Theory is applied to the description of quarks and the pion. The dressed quark mass function is calculated dynamically in Minkowski space and used in the calculation of the pion electromagnetic form factor. The effects of the mass function on the pion form factor and the different quark-pole contributions to the triangle diagram then are analyzed.

Quark Mass Functions and Pion Structure in the Covariant Spectator Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biernat, Elmar P.; Gross, Franz; Pena, Teresa

The Covariant Spectator Theory is applied to the description of quarks and the pion. The dressed quark mass function is calculated dynamically in Minkowski space and used in the calculation of the pion electromagnetic form factor. The effects of the mass function on the pion form factor and the different quark-pole contributions to the triangle diagram then are analyzed.

Iterative and function-continuation Fourier deconvolution methods for enhancing mass spectrometer resolution

NASA Technical Reports Server (NTRS)

Ioup, J. W.; Ioup, G. E.; Rayborn, G. H., Jr.; Wood, G. M., Jr.; Upchurch, B. T.

1984-01-01

Mass spectrometer data in the form of ion current versus mass-to-charge ratio often include overlapping mass peaks, especially in low- and medium-resolution instruments. Numerical deconvolution of such data effectively enhances the resolution by decreasing the overlap of mass peaks. In this paper two approaches to deconvolution are presented: a function-domain iterative technique and a Fourier transform method which uses transform-domain function-continuation. Both techniques include data smoothing to reduce the sensitivity of the deconvolution to noise. The efficacy of these methods is demonstrated through application to representative mass spectrometer data and the deconvolved results are discussed and compared to data obtained from a spectrometer with sufficient resolution to achieve separation of the mass peaks studied. A case for which the deconvolution is seriously affected by Gibbs oscillations is analyzed.

Black hole binaries dynamically formed in globular clusters

NASA Astrophysics Data System (ADS)

Park, Dawoo; Kim, Chunglee; Lee, Hyung Mok; Bae, Yeong-Bok; Belczynski, Krzysztof

2017-08-01

We investigate properties of black hole (BH) binaries formed in globular clusters via dynamical processes, using directN-body simulations. We pay attention to effects of BH mass function on the total mass and mass ratio distributions of BH binaries ejected from clusters. First, we consider BH populations with two different masses in order to learn basic differences from models with single-mass BHs only. Secondly, we consider continuous BH mass functions adapted from recent studies on massive star evolution in a low metallicity environment, where globular clusters are formed. In this work, we consider only binaries that are formed by three-body processes and ignore stellar evolution and primordial binaries for simplicity. Our results imply that most BH binary mergers take place after they get ejected from the cluster. Also, mass ratios of dynamically formed binaries should be close to 1 or likely to be less than 2:1. Since the binary formation efficiency is larger for higher-mass BHs, it is likely that a BH mass function sampled by gravitational-wave observations would be weighed towards higher masses than the mass function of single BHs for a dynamically formed population. Applying conservative assumptions regarding globular cluster populations such as small BH mass fraction and no primordial binaries, the merger rate of BH binaries originated from globular clusters is estimated to be at least 6.5 yr-1 Gpc-3. Actual rate can be up to more than several times of our conservative estimate.

THE EFFECT OF WARM DARK MATTER ON GALAXY PROPERTIES: CONSTRAINTS FROM THE STELLAR MASS FUNCTION AND THE TULLY-FISHER RELATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Xi; Maccio, Andrea V.; Dutton, Aaron A.

2013-04-10

In this paper, we combine high-resolution N-body simulations with a semi-analytical model of galaxy formation to study the effects of a possible warm dark matter (WDM) component on the observable properties of galaxies. We compare three WDM models with a dark matter (DM) mass of 0.5, 0.75, and 2.0 keV with the standard cold dark matter case. For a fixed set of parameters describing the baryonic physics, the WDM models predict fewer galaxies at low (stellar) masses, as expected due to the suppression of power on small scales, while no substantial difference is found at the high-mass end. However, thesemore » differences in the stellar mass function vanish when a different set of parameters is used to describe the (largely unknown) galaxy formation processes. We show that it is possible to break this degeneracy between DM properties and the parameterization of baryonic physics by combining observations on the stellar mass function with the Tully-Fisher relation (the relation between stellar mass and the rotation velocity at large galactic radii as probed by resolved H I rotation curves). WDM models with a too warm candidate (m{sub {nu}} < 0.75 keV) cannot simultaneously reproduce the stellar mass function and the Tully-Fisher relation. We conclude that accurate measurements of the galaxy stellar mass function and the link between galaxies and DM halos down to the very low mass end can give very tight constraints on the nature of DM candidates.« less

Culture in Education and Mass Media: Conformation or Confrontation?

ERIC Educational Resources Information Center

Mosa, Ali Abdullah

1999-01-01

Discusses the concept of culture in light of the technological revolution that has crossed traditional geopolitical boundaries. Topics include the function of education; the function of mass media; and a comparison of how educational and mass media institutions affect culture. (Author/LRW)

How Massive Single Stars End Their Life

NASA Technical Reports Server (NTRS)

Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H.

2003-01-01

How massive stars die-what sort of explosion and remnant each produces-depends chiefly on the masses of their helium cores and hydrogen envelopes at death. For single stars, stellar winds are the only means of mass loss, and these are a function of the metallicity of the star. We discuss how metallicity, and a simplified prescription for its effect on mass loss, affects the evolution and final fate of massive stars. We map, as a function of mass and metallicity, where black holes and neutron stars are likely to form and where different types of supernovae are produced. Integrating over an initial mass function, we derive the relative populations as a function of metallicity. Provided that single stars rotate rapidly enough at death, we speculate on stellar populations that might produce gamma-ray bursts and jet-driven supernovae.

Effect of low appendicular lean mass, grip strength, and gait speed on the functional outcome after surgery for distal radius fractures.

PubMed

Roh, Young Hak; Noh, Jung Ho; Gong, Hyun Sik; Baek, Goo Hyun

2017-12-01

Patients with low appendicular lean mass plus slow gait speed or weak grip strength are at risk for poor functional recovery after surgery for distal radius fracture, even when they have similar radiologic outcomes. Loss of skeletal muscle mass and consequent loss in muscle function associate with aging, and this condition negatively impacts the activities of daily living and increases elderly individuals' frailty to falls. Thus, patients with low appendicular lean mass would show different functional recovery compared to those without this condition after surgery for distal radius fracture (DRF). This study compares the functional outcomes after surgery for DRF in patients with or without low appendicular lean mass plus slowness or weakness. A total of 157 patients older than 50 years of age with a DRF treated via volar plate fixation were enrolled in this prospective study. A definition of low appendicular lean mass with slowness or weakness was based on the consensus of the Asian Working Group for Sarcopenia. The researchers compared functional assessments (wrist range of motion and Michigan Hand Questionnaire [MHQ]) and radiographic assessments (radial inclination, volar tilt, ulnar variance, and articular congruity) 12 months after surgery between patients with and without low appendicular lean mass plus slowness or weakness. Multivariable regression analyses were performed to determine whether appendicular lean mass, grip strength, gait speed, patient demographic, or injury characteristics accounted for the functional outcomes. Patients with low appendicular lean mass plus slowness or weakness showed a significantly lower recovery of MHQ score than those in the control group throughout 12 months. There was no significant difference in the range of motion between the groups. The radiologic outcomes showed no significant difference between groups in terms of volar tilt, radial inclination, or ulnar variance. According to multivariable regression analysis, the poor recovery of MHQ score was associated with an increase in age, weak grip strength, and lower appendicular lean mass, and these three factors accounted for 37% of the variation in the MHQ scores. Patients with low appendicular lean mass plus slowness or weakness are at risk for poor functional recovery after surgery for DRF, even when they have similar radiologic outcomes.

Optical and Near-infrared Spectra of σ Orionis Isolated Planetary-mass Objects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zapatero Osorio, M. R.; Béjar, V. J. S.; Ramírez, K. Peña, E-mail: mosorio@cab.inta-csic.es, E-mail: vbejar@iac.es, E-mail: karla.pena@uantof.cl

We have obtained low-resolution optical (0.7–0.98 μ m) and near-infrared (1.11–1.34 μ m and 0.8–2.5 μ m) spectra of 12 isolated planetary-mass candidates ( J = 18.2–19.9 mag) of the 3 Myr σ Orionis star cluster with the aim of determining the spectroscopic properties of very young, substellar dwarfs and assembling a complete cluster mass function. We have classified our targets by visual comparison with high- and low-gravity standards and by measuring newly defined spectroscopic indices. We derived L0–L4.5 and M9–L2.5 using high- and low-gravity standards, respectively. Our targets reveal clear signposts of youth, thus corroborating their cluster membership andmore » planetary masses (6–13 M {sub Jup}). These observations complete the σ Orionis mass function by spectroscopically confirming the planetary-mass domain to a confidence level of ∼75%. The comparison of our spectra with BT-Settl solar metallicity model atmospheres yields a temperature scale of 2350–1800 K and a low surface gravity of log g ≈ 4.0 [cm s{sup −2}], as would be expected for young planetary-mass objects. We discuss the properties of the cluster’s least-massive population as a function of spectral type. We have also obtained the first optical spectrum of S Ori 70, a T dwarf in the direction of σ Orionis. Our data provide reference optical and near-infrared spectra of very young L dwarfs and a mass function that may be used as templates for future studies of low-mass substellar objects and exoplanets. The extrapolation of the σ Orionis mass function to the solar neighborhood may indicate that isolated planetary-mass objects with temperatures of ∼200–300 K and masses in the interval 6–13 M {sub Jup} may be as numerous as very low-mass stars.« less

Statistical Issues in Galaxy Cluster Cosmology

NASA Technical Reports Server (NTRS)

Mantz, Adam

2013-01-01

The number and growth of massive galaxy clusters are sensitive probes of cosmological structure formation. Surveys at various wavelengths can detect clusters to high redshift, but the fact that cluster mass is not directly observable complicates matters, requiring us to simultaneously constrain scaling relations of observable signals with mass. The problem can be cast as one of regression, in which the data set is truncated, the (cosmology-dependent) underlying population must be modeled, and strong, complex correlations between measurements often exist. Simulations of cosmological structure formation provide a robust prediction for the number of clusters in the Universe as a function of mass and redshift (the mass function), but they cannot reliably predict the observables used to detect clusters in sky surveys (e.g. X-ray luminosity). Consequently, observers must constrain observable-mass scaling relations using additional data, and use the scaling relation model in conjunction with the mass function to predict the number of clusters as a function of redshift and luminosity.

Estimation of the auto frequency response function at unexcited points using dummy masses

NASA Astrophysics Data System (ADS)

Hosoya, Naoki; Yaginuma, Shinji; Onodera, Hiroshi; Yoshimura, Takuya

2015-02-01

If structures with complex shapes have space limitations, vibration tests using an exciter or impact hammer for the excitation are difficult. Although measuring the auto frequency response function at an unexcited point may not be practical via a vibration test, it can be obtained by assuming that the inertia acting on a dummy mass is an external force on the target structure upon exciting a different excitation point. We propose a method to estimate the auto frequency response functions at unexcited points by attaching a small mass (dummy mass), which is comparable to the accelerometer mass. The validity of the proposed method is demonstrated by comparing the auto frequency response functions estimated at unexcited points in a beam structure to those obtained from numerical simulations. We also consider random measurement errors by finite element analysis and vibration tests, but not bias errors. Additionally, the applicability of the proposed method is demonstrated by applying it to estimate the auto frequency response function of the lower arm in a car suspension.

Quasar evolution and the growth of black holes

NASA Technical Reports Server (NTRS)

Small, Todd A.; Blandford, Roger D.

1992-01-01

A 'minimalist' model of AGN evolution is analyzed that links the measured luminosity function to an elementary description of black hole accretion. The observed luminosity function of bright AGN is extrapolated and simple prescriptions for the growth and luminosity of black holes are introduced to infer quasar birth rates, mean fueling rates, and relict black hole distribution functions. It is deduced that the mean accretion rate scales as (M exp -1./5)(t exp -6.7) and that, for the most conservative model used, the number of relict black holes per decade declines only as M exp -0.4 for black hole masses between 3 x 10 exp 7 and 3 x 10 exp 9 solar masses. If all sufficiently massive galaxies pass through a quasar phase with asymptotic black hole mass a monotonic function of the galaxy mass, then it is possible to compare the space density of galaxies with estimated central masses to that of distant quasars.

The Incomplete Conditional Stellar Mass Function: Unveiling the Stellar Mass Functions of Galaxies at 0.1 < Z < 0.8 from BOSS Observations

NASA Astrophysics Data System (ADS)

Guo, Hong; Yang, Xiaohu; Lu, Yi

2018-05-01

We propose a novel method to constrain the missing fraction of galaxies using galaxy clustering measurements in the galaxy conditional stellar mass function (CSMF) framework, which is applicable to surveys that suffer significantly from sample selection effects. The clustering measurements, which are not sensitive to the random sampling (missing fraction) of galaxies, are widely used to constrain the stellar–halo mass relation (SHMR). By incorporating a missing fraction (incompleteness) component into the CSMF model (ICSMF), we use the incomplete stellar mass function and galaxy clustering to simultaneously constrain the missing fractions and the SHMRs. Tests based on mock galaxy catalogs with a few typical missing fraction models show that this method can accurately recover the missing fraction and the galaxy SHMR, hence providing us with reliable measurements of the galaxy stellar mass functions. We then apply it to the Baryon Oscillation Spectroscopic Survey (BOSS) over the redshift range of 0.1 < z < 0.8 for galaxies of M * > 1011 M ⊙. We find that the sample completeness for BOSS is over 80% at z < 0.6 but decreases at higher redshifts to about 30%. After taking these completeness factors into account, we provide accurate measurements of the stellar mass functions for galaxies with {10}11 {M}ȯ < {M}* < {10}12 {M}ȯ , as well as the SHMRs, over the redshift range 0.1 < z < 0.8 in this largest galaxy redshift survey.

The mass function of Seyfert 1 nuclei

NASA Technical Reports Server (NTRS)

Padovani, P.; Burg, R.; Edelson, R. A.

1990-01-01

The first mass function of Seyfert 1 nuclei is derived from optical spectra of the complete CfA sample of Seyfert galaxies by estimating the mass for each object from a dynamical relation. An independent estimate is also derived using a complete infrared-selected sample. The two mass functions are indistinguishable. The mean mass of Seyfert 1 nuclei is about 2 x 10 to the 7th solar masses, and the integrated mass density is about 6 x 10 to the 11th solar masses/cu Gpc. This is approximately two orders of magnitude less than the value inferred from the energetics associated with quasar counts. A careful analysis of the various parameters and assumptions involved suggests that this large difference is not due to systematic errors in the determinations. Therefore, the bulk of mass related to the accretion processes connected with past quasar activity does not reside in Seyfert 1 nuclei. Instead, the remnants of past activity must be present in a much larger number of galaxies, and a one-to-one relation between distant and local active galactic nuclei seems then to be excluded.

Multi-epoch analysis of the X-ray spectrum of the active galactic nucleus in NGC 5506

NASA Astrophysics Data System (ADS)

Sun, Shangyu; Guainazzi, Matteo; Ni, Qingling; Wang, Jingchun; Qian, Chenyang; Shi, Fangzheng; Wang, Yu; Bambi, Cosimo

2018-05-01

We present a multi-epoch X-ray spectroscopy analysis of the nearby narrow-line Seyfert I galaxy NGC 5506. For the first time, spectra taken by Chandra, XMM-Newton, Suzaku, and NuSTAR - covering the 2000-2014 time span - are analyzed simultaneously, using state-of-the-art models to describe reprocessing of the primary continuum by optical thick matter in the AGN environment. The main goal of our study is determining the spin of the supermassive black hole (SMBH). The nuclear X-ray spectrum is photoelectrically absorbed by matter with column density ≃ 3 × 1022 cm-2. A soft excess is present at energies lower than the photoelectric cut-off. Both photo-ionized and collisionally ionized components are required to fit it. This component is constant over the time-scales probed by our data. The spectrum at energies higher than 2 keV is variable. We propose that its evolution could be driven by flux-dependent changes in the geometry of the innermost regions of the accretion disk. The black hole spin in NGC ,5506 is constrained to be 0.93± _{ 0.04 }^{0.04} at 90% confidence level for one interesting parameter.

The Compton-thick AGN fraction from the deepest X-ray spectroscopy in the CDF-S

NASA Astrophysics Data System (ADS)

Corral, A.; Georgantopoulos, I.; Akylas, A.; Ranalli, P.

2017-10-01

Highly obscured AGN, especially Compton-thick (CT) AGN, likely play a key role in the galaxy-AGN co-evolution scenario. They would comprise the early stages of AGN activity, preceding the AGN-feedback/star-formation quenching phase, during which most of both the SMBH and galaxy growth take place. However, the actual CT fraction among the AGN population is still largely unconstrained. The most reliable way of confirming the obscured nature of an AGN by X-ray spectroscopy, but very deep observations are needed to extend local analyses to larger distances. We will present the X-ray spectral analysis of the deepest X-ray data obtained to date, the almost 7Ms observation of the Chandra Deep Field South. The unprecedented depth of this survey allow us to carry out reliable spectral analyses down to a flux limit of 10^{-16} erg cm^{-2} s^{-1} in the hard 2-8 keV band. Besides the new deeper X-ray data, our approach also includes the implementation of Bayesian inference in the determination of the CT fraction. Our results favor X-ray background synthesis models which postulate a moderate fraction (25%) of CT objects among the obscured AGN population.

Feeding supermassive black holes by collisional cascades

NASA Astrophysics Data System (ADS)

Faber, Christian; Dehnen, Walter

2018-05-01

The processes driving gas accretion on to supermassive black holes (SMBHs) are still poorly understood. Angular momentum conservation prevents gas within ˜10 pc of the black hole from reaching radii ˜10-3 pc where viscous accretion becomes efficient. Here we present simulations of the collapse of a clumpy shell of swept-up isothermal gas, which is assumed to have formed as a result of feedback from a previous episode of AGN activity. The gas falls towards the SMBH forming clumps and streams, which intersect, collide, and often form a disc. These collisions promote partial cancellations of angular momenta, resulting in further infall and more collisions. This continued collisional cascade generates a tail of gas with sufficiently small angular momenta and provides a viable route for gas inflow to sub-parsec scales. The efficiency of this process hardly depends on details, such as gas temperature, initial virial ratio and power spectrum of the gas distribution, as long as it is not strongly rotating. Adding star formation to this picture might explain the near-simultaneous formation of the S-stars (from tidally disrupted binaries formed in plunging gas streams) and the sub-parsec young stellar disc around Sgr A⋆.

Feeding supermassive black holes by collisional cascades

NASA Astrophysics Data System (ADS)

Faber, Christian; Dehnen, Walter

2018-07-01

The processes driving gas accretion on to supermassive black holes (SMBHs) are still poorly understood. Angular momentum conservation prevents gas within ˜10 pc of the black hole from reaching radii ˜10-3pc where viscous accretion becomes efficient. Here we present simulations of the collapse of a clumpy shell of swept-up isothermal gas, which is assumed to have formed as a result of feedback from a previous episode of AGN activity. The gas falls towards the SMBH forming clumps and streams, which intersect, collide and often form a disc. These collisions promote partial cancellations of angular momenta, resulting in further infall and more collisions. This continued collisional cascade generates a tail of gas with sufficiently small angular momenta and provides a viable route for gas inflow to sub-parsec scales. The efficiency of this process hardly depends on details, such as gas temperature, initial virial ratio and power spectrum of the gas distribution, as long as it is not strongly rotating. Adding star formation to this picture might explain the near-simultaneous formation of the S-stars (from tidally disrupted binaries formed in plunging gas streams) and the sub-parsec young stellar disc around Sgr A⋆.

Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perley, D. A.; Perley, R. A.; Dhawan, V.

2017-06-01

We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of <0.5 mJy in 1989 to 4 mJy in 2016 ( ν = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincidentmore » with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 10{sup 7} years.« less

Constraint on the black hole spin of M87 from the accretion-jet model

NASA Astrophysics Data System (ADS)

Feng, Jianchao; Wu, Qingwen

2017-09-01

The millimetre bump, as found in high-resolution multiwaveband observations of M87 by Prieto et al., most possibly comes from the synchrotron emission of thermal electrons in advection-dominated accretion flow (ADAF). It is possible to constrain the accretion rate near the horizon if both the nuclear millimetre emission and its polarization are produced by the hot plasma in the accretion flow. The jet power of M87 has been extensively explored, which is around 8_-3^{+7}× 10^{42} erg s-1 based on the analysis of the X-ray cavity. The black hole (BH) spin can be estimated if the jet power and the accretion rate near the horizon are known. We model the multiwavelength spectral energy distribution (SED) of M87 with a coupled ADAF-jet model surrounding a Kerr BH, where the full set of relativistic hydrodynamical equations of the ADAF are solved. The hybrid jet formation model, as a variant of the Blandford-Znajek model, is used to model the jet power. We find that the SMBH should be fast rotating with a dimensionless spin parameter a_{*}˜eq 0.98_-0.02^{+0.012}.

VizieR Online Data Catalog: MIR-selected quasar parameters (Dai+, 2014)

NASA Astrophysics Data System (ADS)

Dai, Y. S.; Elvis, M.; Bergeron, J.; Fazio, G. G.; Huang, J.-S.; Wilkes, B. J.; Willmer, C. N. A.; Omont, A.; Papovich, C.

2017-03-01

The combined MIR 24 um and optical selection for this survey was designed to detect objects with luminous torus/nucleus and not biased against dusty hosts. The MIR selection allows for the detection of hot dust (a few hundred Kelvin) at the redshifts z ~ 1.5; while optical follow-up spectroscopically identified the BEL objects, confirming their unobscured (type 1) quasar nature. This MIR selection also allows for a far-infrared (FIR) cross-match to look for cool dust for SMBH-host studies, as demonstrated in Dai et al. (2012ApJ...753...33D). We select Spitzer MIPS (Rieke et al. 2004ApJS..154...25R) 24 um sources from the SWIRE survey in the ~22 deg2 LHS field centered at RA=10:46:48, DE=57:54:00 (Lonsdale et al. 2003PASP..115..897L). The SDSS imaging also covers the LHS region to r = 22.2 at 95% detection repeatability, but can go as deep as r = 23. All magnitudes are taken from the SDSS photoObj catalog in DR7, which are already corrected for Galactic extinction according to Schlegel et al. (1998ApJ...500..525S). (6 data files).

Circumnuclear Structures in Megamaser Host Galaxies

NASA Astrophysics Data System (ADS)

Pjanka, Patryk; Greene, Jenny E.; Seth, Anil C.; Braatz, James A.; Henkel, Christian; Lo, Fred K. Y.; Läsker, Ronald

2017-08-01

Using the Hubble Space Telescope, we identify circumnuclear (100-500 pc scale) structures in nine new H2O megamaser host galaxies to understand the flow of matter from kpc-scale galactic structures down to the supermassive black holes (SMBHs) at galactic centers. We double the sample analyzed in a similar way by Greene et al. and consider the properties of the combined sample of 18 sources. We find that disk-like structure is virtually ubiquitous when we can resolve <200 pc scales, in support of the notion that non-axisymmetries on these scales are a necessary condition for SMBH fueling. We perform an analysis of the orientation of our identified nuclear regions and compare it with the orientation of megamaser disks and the kpc-scale disks of the hosts. We find marginal evidence that the disk-like nuclear structures show increasing misalignment from the kpc-scale host galaxy disk as the scale of the structure decreases. In turn, we find that the orientation of both the ˜100 pc scale nuclear structures and their host galaxy large-scale disks is consistent with random with respect to the orientation of their respective megamaser disks.

An analytic formula for the supercluster mass function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Seunghwan; Lee, Jounghun, E-mail: slim@astro.umass.edu, E-mail: jounghun@astro.snu.ac.kr

2014-03-01

We present an analytic formula for the supercluster mass function, which is constructed by modifying the extended Zel'dovich model for the halo mass function. The formula has two characteristic parameters whose best-fit values are determined by fitting to the numerical results from N-body simulations for the standard ΛCDM cosmology. The parameters are found to be independent of redshifts and robust against variation of the key cosmological parameters. Under the assumption that the same formula for the supercluster mass function is valid for non-standard cosmological models, we show that the relative abundance of the rich superclusters should be a powerful indicatormore » of any deviation of the real universe from the prediction of the standard ΛCDM model.« less

Muscle abnormalities in osteogenesis imperfecta

PubMed Central

Veilleux, L-N.; Trejo, P.; Rauch, F.

2017-01-01

Osteogenesis imperfecta (OI) is mainly characterized by bone fragility but muscle abnormalities have been reported both in OI mouse models and in children with OI. Muscle mass is decreased in OI, even when short stature is taken into account. Dynamic muscle tests aiming at maximal eccentric force production reveal functional deficits that can not be explained by low muscle mass alone. However, it appears that diaphyseal bone mass is normally adapted to muscle force. At present the determinants of muscle mass and function in OI have not been clearly defined. Physiotherapy interventions and bisphosphonate treatment appear to have some effect on muscle function in OI. Interventions targeting muscle mass have shown encouraging results in OI animal models and are an interesting area for further research. PMID:28574406

A new smooth-k space filter approach to calculate halo abundances

NASA Astrophysics Data System (ADS)

Leo, Matteo; Baugh, Carlton M.; Li, Baojiu; Pascoli, Silvia

2018-04-01

We propose a new filter, a smooth-k space filter, to use in the Press-Schechter approach to model the dark matter halo mass function which overcomes shortcomings of other filters. We test this against the mass function measured in N-body simulations. We find that the commonly used sharp-k filter fails to reproduce the behaviour of the halo mass function at low masses measured from simulations of models with a sharp truncation in the linear power spectrum. We show that the predictions with our new filter agree with the simulation results over a wider range of halo masses for both damped and undamped power spectra than is the case with the sharp-k and real-space top-hat filters.

VizieR Online Data Catalog: Tracers of the Milky Way mass (Bratek+, 2014)

NASA Astrophysics Data System (ADS)

Bratek, L.; Sikora, S.; Jalocha, J.; Kutschera, M.

2013-11-01

We model the phase-space distribution of the kinematic tracers using general, smooth distribution functions to derive a conservative lower bound on the total mass within ~~150-200kpc. By approximating the potential as Keplerian, the phase-space distribution can be simplified to that of a smooth distribution of energies and eccentricities. Our approach naturally allows for calculating moments of the distribution function, such as the radial profile of the orbital anisotropy. We systematically construct a family of phase-space functions with the resulting radial velocity dispersion overlapping with the one obtained using data on radial motions of distant kinematic tracers, while making no assumptions about the density of the tracers and the velocity anisotropy parameter β regarded as a function of the radial variable. While there is no apparent upper bound for the Milky Way mass, at least as long as only the radial motions are concerned, we find a sharp lower bound for the mass that is small. In particular, a mass value of 2.4x1011M⊙, obtained in the past for lower and intermediate radii, is still consistent with the dispersion profile at larger radii. Compared with much greater mass values in the literature, this result shows that determining the Milky Way mass is strongly model-dependent. We expect a similar reduction of mass estimates in models assuming more realistic mass profiles. (1 data file).

Near-infrared reddening of extra-galactic giant molecular clouds in a face-on geometry

NASA Astrophysics Data System (ADS)

Kainulainen, J.; Juvela, M.; Alves, J.

2008-04-01

Aims: We describe the near-infrared reddening signature of giant molecular clouds (GMCs) in external galaxies. In particular, we examine the EJ-H and EH-K color excesses and the effective extinction law observed in discrete GMC regions. We also study the effect of the relative scale height of the GMC distribution to the color excesses, and to the observed mass function of GMCs when the masses are derived using color excess as a linear estimator of mass. Methods: We performed Monte Carlo radiative transfer simulations with 3D models of stellar radiation and clumpy dust distributions, resembling a face-on geometry. The scattered light is included in the models, and near-infrared color maps were calculated from the simulated data. We performed the simulations with different scale heights of GMCs and compared the color excesses and attenuation of light in different geometries. We extracted GMCs from the simulated color maps and compared the mass functions to the input mass functions. Results: The effective near-infrared reddening law, i.e. the ratio EJ-H/EH-K, has a value close to unity in GMC regions. The ratio depends significantly on the relative scale height of GMCs, ξ, and for ξ values 0.1...0.75, we find the typical ratios of 0.6...1.1. The effective extinction law turns out to be very flat in GMC regions. We find the ratios of apparent extinctions of AH^a/AKa = 1.35...1.55 and AJ^a/AHa = 1.15. The effect of the scattered flux on the effective reddening law, as well as on the effective extinction law, is significant. Regarding the GMC mass function, we find no correlation between the input and observed slopes of the mass functions. Instead, the observed slope reflects the parameter ξ and the dynamical range of the mass function. As the observed slope depends on the geometric parameters, which are not known, it is not possible to constrain the slope of the mass function using this technique. We estimate that only a fraction of 10...20% of the total mass of GMCs is recovered, if the observed color excess values are transformed to masses using the Galactic reddening law. In the case of individual clouds, the fraction can vary between ~0...50%.

Relationships among body weight, joint moments generated during functional activities, and hip bone mass in older adults

PubMed Central

Wang, Man-Ying; Flanagan, Sean P.; Song, Joo-Eun; Greendale, Gail A.; Salem, George J.

2012-01-01

Objective To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults. Methods Eight male and eight female older adults (70–85 yr) performed functional activities including walking, chair sit–stand–sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson’s correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis. Findings Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p < 0.05 to p < 0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter. Interpretation Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass. PMID:16631283

Galaxy And Mass Assembly (GAMA): the galaxy stellar mass function to z = 0.1 from the r-band selected equatorial regions

NASA Astrophysics Data System (ADS)

Wright, A. H.; Robotham, A. S. G.; Driver, S. P.; Alpaslan, M.; Andrews, S. K.; Baldry, I. K.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Colless, M.; da Cunha, E.; Davies, L. J. M.; Graham, Alister W.; Holwerda, B. W.; Hopkins, A. M.; Kafle, P. R.; Kelvin, L. S.; Loveday, J.; Maddox, S. J.; Meyer, M. J.; Moffett, A. J.; Norberg, P.; Phillipps, S.; Rowlands, K.; Taylor, E. N.; Wang, L.; Wilkins, S. M.

2017-09-01

We derive the low-redshift galaxy stellar mass function (GSMF), inclusive of dust corrections, for the equatorial Galaxy And Mass Assembly (GAMA) data set covering 180 deg2. We construct the mass function using a density-corrected maximum volume method, using masses corrected for the impact of optically thick and thin dust. We explore the galactic bivariate brightness plane (M⋆-μ), demonstrating that surface brightness effects do not systematically bias our mass function measurement above 107.5 M⊙. The galaxy distribution in the M-μ plane appears well bounded, indicating that no substantial population of massive but diffuse or highly compact galaxies are systematically missed due to the GAMA selection criteria. The GSMF is fitted with a double Schechter function, with M^\\star =10^{10.78± 0.01± 0.20} M_{⊙}, φ ^\\star _1=(2.93± 0.40)× 10^{-3} h_{70}^3 Mpc-3, α1 = -0.62 ± 0.03 ± 0.15, φ ^\\star _2=(0.63± 0.10)× 10^{-3} h_{70}^3 Mpc-3 and α2 = -1.50 ± 0.01 ± 0.15. We find the equivalent faint end slope as previously estimated using the GAMA-I sample, although we find a higher value of M^\\star. Using the full GAMA-II sample, we are able to fit the mass function to masses as low as 107.5 M⊙, and assess limits to 106.5 M⊙. Combining GAMA-II with data from G10-COSMOS, we are able to comment qualitatively on the shape of the GSMF down to masses as low as 106 M⊙. Beyond the well-known upturn seen in the GSMF at 109.5, the distribution appears to maintain a single power-law slope from 109 to 106.5. We calculate the stellar mass density parameter given our best-estimate GSMF, finding Ω _\\star = 1.66^{+0.24}_{-0.23}± 0.97 h^{-1}_{70} × 10^{-3}, inclusive of random and systematic uncertainties.

Body composition, nutritional status, and endothelial function in physically active men without metabolic syndrome--a 25 year cohort study.

PubMed

Pigłowska, Małgorzata; Kostka, Tomasz; Drygas, Wojciech; Jegier, Anna; Leszczyńska, Joanna; Bill-Bielecka, Mirosława; Kwaśniewska, Magdalena

2016-04-27

The purpose of this analysis was to investigate the relationship between body composition, metabolic parameters and endothelial function among physically active healthy middle-aged and older men. Out of 101 asymptomatic men prospectively tracked for traditional cardiovascular risk factors (mean observation period 25.1 years), 55 metabolically healthy individuals who maintained stable leisure time physical activity (LTPA) level throughout the observation and agreed to participate in the body composition assessment were recruited (mean age 60.3 ± 9.9 years). Body composition and raw bioelectrical parameters were measured with bioelectrical impedance analysis (BIA). Microvascular endothelial function was evaluated by means of the reactive hyperemia index (RHI) using Endo-PAT2000 system. Strong correlations were observed between lifetime physical activity (PA), aerobic fitness and most of analyzed body composition parameters. The strongest inverse correlation was found for fat mass (p < 0.01) while positive relationship for fat-free mass (p < 0.01), total body water (p < 0.05 for current aerobic capacity and p < 0.01 for historical PA), body cell mass (p < 0.001), muscle mass (p < 0.001), calcium and potassium (p < 0.01 and p < 0.001 for current aerobic capacity and p < 0.001 and p < 0.01 for historical PA, respectively) and glycogen mass (p < 0.001). Among metabolic parameters, HDL cholesterol (HDL-C) and uric acid were significantly associated with most body composition indicators. Regarding endothelial function, a negative correlation was found for RHI and body mass (p < 0.05) while positive relationship for RHI and body cell mass (p < 0.05), calcium (p < 0.05) and potassium mass (p < 0.05). Impaired endothelial function was observed among 8 subjects. Among bioelectrical parameters, impedance (Z) and resistance (R) normalized for subjects' height were negatively related with body mass, body mass index (BMI) and waist circumference (p < 0.001); while reactance (Xc) normalized for patients' height was negatively related with body mass (p < 0.05). The mean phase angle value was relatively high (8.83 ± 1.22) what reflects a good level of cellularity and cell function. Phase angle was positively related with body mass and BMI (p < 0.05). Both fat mass and muscle mass components are important predictors of metabolic profile. Maintaining regular high PA level and metabolically healthy status through young and middle adulthood may have beneficial influence on body composition parameters and may prevent age-related decrease of fat-free mass and endothelial dysfunction.

Stellar Mass Function of Active and Quiescent Galaxies via the Continuity Equation

NASA Astrophysics Data System (ADS)

Lapi, A.; Mancuso, C.; Bressan, A.; Danese, L.

2017-09-01

The continuity equation is developed for the stellar mass content of galaxies and exploited to derive the stellar mass function of active and quiescent galaxies over the redshift range z˜ 0{--}8. The continuity equation requires two specific inputs gauged from observations: (I) the star formation rate functions determined on the basis of the latest UV+far-IR/submillimeter/radio measurements and (II) average star formation histories for individual galaxies, with different prescriptions for disks and spheroids. The continuity equation also includes a source term taking into account (dry) mergers, based on recent numerical simulations and consistent with observations. The stellar mass function derived from the continuity equation is coupled with the halo mass function and with the SFR functions to derive the star formation efficiency and the main sequence of star-forming galaxies via the abundance-matching technique. A remarkable agreement of the resulting stellar mass functions for active and quiescent galaxies of the galaxy main sequence, and of the star formation efficiency with current observations is found; the comparison with data also allows the characteristic timescales for star formation and quiescence of massive galaxies, the star formation history of their progenitors, and the amount of stellar mass added by in situ star formation versus that contributed by external merger events to be robustly constrained. The continuity equation is shown to yield quantitative outcomes that detailed physical models must comply with, that can provide a basis for improving the (subgrid) physical recipes implemented in theoretical approaches and numerical simulations, and that can offer a benchmark for forecasts on future observations with multiband coverage, as will become routinely achievable in the era of JWST.

Sizes of Black Holes Throughout the Universe

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-05-01

What is the distribution of sizes of black holes in our universe? Can black holes of any mass exist, or are there gaps in their possible sizes? The shape of this black-hole mass function has been debated for decades and the dawn of gravitational-wave astronomy has only spurred further questions.Mind the GapsThe starting point for the black-hole mass function lies in the initial mass function (IMF) for stellar black holes the beginning size distribution of black holes after they are born from stars. Instead of allowing for the formation of stellar black holes of any mass, theoretical models propose two gaps in the black-hole IMF:An upper mass gap at 50130 solar masses, due to the fact that stellar progenitors of black holes in this mass range are destroyed by pair-instability supernovae.A lower mass gap below 5 solar masses, which is argued to arise naturally from the mechanics of supernova explosions.Missing black-hole (BH) formation channels due to the existence of the lower gap (LG) and the upper gap (UG) in the initial mass function. a) The number of BHs at all scales are lowered because no BH can merge with BHs in the LG to form a larger BH. b) The missing channel responsible for the break at 10 solar masses, resulting from the LG. c) The missing channel responsible for the break at 60 solar masses, due to the interaction between the LG and the UG. [Christian et al. 2018]We can estimate the IMF for black holes by scaling a typical IMF for stars and then adding in these theorized gaps. But is this initial distribution of black-hole masses the same as the distribution that we observe in the universe today?The Influence of MergersBased on recent events, the answer appears to be no! Since the first detections of gravitational waves in September 2015, we now know that black holes can merge to form bigger black holes. An initial distribution of black-hole masses must therefore evolve over time, as mergers cause the depletion of low-mass black holes and an increase in higher-mass black holes.A team of scientists led by Pierre Christian, an Einstein Fellow at Harvard University, has now looked into characterizing this shift. In particular, Christian and collaborators explore how black-hole mergers in the centers of dense star clustersultimately shape the black-hole mass function of the universe.Black Holes TodayChristian and collaborators use analytical models of coagulation mergers of particles to form larger particles to estimate the impact of mergers in star clusters on resulting black-hole sizes. They find that, over an evolution of 10 billion years, mergers can appreciably fill in the upper mass gap of the black-hole IMF.An example of the black-hole mass function that can result from evolving the initial mass function complete with gaps over time. Two breaks appear as a result of the initial gaps: one at 10 (LB) and one at 60 solar masses (UB). [Christian et al. 2018]The lower mass gap, on the other hand, leaves observable signatures in the final black-hole mass function: a break at 10 solar masses (since black holes below this mass cant be created by mergers) and one at 60 solar masses (caused by the interaction of the upper and lower gaps). As we build up black-hole statistics in the future (thanks, gravitational-wave detectors!), searching for these breaks will help us to test our models.Lastly, the authors find that their models can only be consistent with observations if ejection is efficient black holes must be regularly ousted from star clusters through interactions with other bodies or as a result of kicks when they merge. This idea is consistent with many recent studies supporting a large population of free-floating stellar-mass black holes.CitationPierre Christian et al 2018 ApJL 858 L8. doi:10.3847/2041-8213/aabf88

Antarctic Mass Loss from GRACE from Space- and Time-Resolved Modeling with Slepian Functions

NASA Astrophysics Data System (ADS)

Simons, F. J.; Harig, C.

2013-12-01

The melting of polar ice sheets is a major contributor to global sea-level rise. Antarctica is of particular interest since most of the mass loss has occurred in West Antarctica, however updated glacial isostatic adjustment (GIA) models and recent mass gains in East Antarctica have reduced the continent-wide integrated decadal trend of mass loss. Here we present a spatially and temporally resolved estimation of the Antarctic ice mass change using Slepian localization functions. With a Slepian basis specifically for Antarctica, the basis functions maximize their energy on the continent and we can project the geopotential fields into a sparse set of orthogonal coefficients. By fitting polynomial functions to the limited basis coefficients we maximize signal-to-noise levels and need not perform smoothing or destriping filters common to other approaches. In addition we determine an empirical noise covariance matrix from the GRACE data to estimate the uncertainty of mass estimation. When applied to large ice sheets, as in our own recent Greenland work, this technique is able to resolve both the overall continental integrated mass trend, as well as the spatial distribution of the mass changes over time. Using CSR-RL05 GRACE data between Jan. 2003 and Jan 2013, we estimate the regional accelerations in mass change for several sub-regions and examine how the spatial pattern of mass has changed. The Amundsen Sea coast of West Antarctica has experienced a large acceleration in mass loss (-26 Gt/yr^2). While mass loss is concentrated near Pine Island and Thwaites glaciers, it has also increased along the coast further towards the Ross ice shelf.

First X-ray Statistical Tests for Clumpy-Torus Models: Constraints from RXTEmonitoring of Seyfert AGN

NASA Astrophysics Data System (ADS)

Markowitz, Alex; Krumpe, Mirko; Nikutta, R.

2016-06-01

In two papers (Markowitz, Krumpe, & Nikutta 2014, and Nikutta et al., in prep.), we derive the first X-ray statistical constraints for clumpy-torus models in Seyfert AGN by quantifying multi-timescale variability in line of-sight X-ray absorbing gas as a function of optical classification.We systematically search for discrete absorption events in the vast archive of RXTE monitoring of 55 nearby type Is and Compton-thin type IIs. We are sensitive to discrete absorption events due to clouds of full-covering, neutral/mildly ionized gas transiting the line of sight. Our results apply to both dusty and non-dusty clumpy media, and probe model parameter space complementary to that for eclipses observed with XMM-Newton, Suzaku, and Chandra.We detect twelve eclipse events in eight Seyferts, roughly tripling the number previously published from this archive. Event durations span hours to years. Most of our detected clouds are Compton-thin, and most clouds' distances from the black hole are inferred to be commensurate with the outer portions of the BLR or the inner regions of infrared-emitting dusty tori.We present the density profiles of the highest-quality eclipse events; the column density profile for an eclipsing cloud in NGC 3783 is doubly spiked, possibly indicating a cloud that is being tidallysheared. We discuss implications for cloud distributions in the context of clumpy-torus models. We calculate eclipse probabilities for orientation-dependent Type I/II unification schemes.We present constraints on cloud sizes, stability, and radial distribution. We infer that clouds' small angular sizes as seen from the SMBH imply 107 clouds required across the BLR + torus. Cloud size is roughly proportional to distance from the black hole, hinting at the formation processes (e.g., disk fragmentation). All observed clouds are sub-critical with respect to tidal disruption; self-gravity alone cannot contain them. External forces, such as magnetic fields or ambient pressure, are needed to contain them; otherwise, clouds must be short-lived.

On non-parametric maximum likelihood estimation of the bivariate survivor function.

PubMed

Prentice, R L

The likelihood function for the bivariate survivor function F, under independent censorship, is maximized to obtain a non-parametric maximum likelihood estimator &Fcirc;. &Fcirc; may or may not be unique depending on the configuration of singly- and doubly-censored pairs. The likelihood function can be maximized by placing all mass on the grid formed by the uncensored failure times, or half lines beyond the failure time grid, or in the upper right quadrant beyond the grid. By accumulating the mass along lines (or regions) where the likelihood is flat, one obtains a partially maximized likelihood as a function of parameters that can be uniquely estimated. The score equations corresponding to these point mass parameters are derived, using a Lagrange multiplier technique to ensure unit total mass, and a modified Newton procedure is used to calculate the parameter estimates in some limited simulation studies. Some considerations for the further development of non-parametric bivariate survivor function estimators are briefly described.

Transient response of multidegree-of-freedom linear systems to forcing functions with inequality constraints

NASA Technical Reports Server (NTRS)

Michalopoulos, C. D.

1974-01-01

Optimal control theory is applied to analyze the transient response of discrete linear systems to forcing functions with unknown time dependence but having known bounds. Particular attention is given to forcing functions which include: (1) maximum displacement of any given mass element, (2) maximum relative displacement of any two adjacent masses, and (3) maximum acceleration of a given mass. Linear mechanical systems with an arbitrary number of degrees of freedom and only one forcing function acting are considered. In the general case, the desired forcing function is found to be a function that switches from the upper-to-lower bound and vice-versa at certain moments of time. A general procedure for finding such switching times is set forth.

Poor physical function in elderly women in low-level aged care is related to muscle strength rather than to measures of sarcopenia

PubMed Central

Woods, Julie L; Iuliano-Burns, Sandra; King, Susannah J; Strauss, Boyd J; Walker, Karen Z

2011-01-01

Purpose: To determine the prevalence of sarcopenia and investigate relationships among body composition, muscle strength, and physical function in elderly women in low-level aged care. Subjects and methods: Sixty-three ambulatory women (mean age 86 years) participated in this cross-sectional study where body composition was determined by dual energy X-ray absorptiometry (DXA); ankle, knee, and hip strength by the Nicholas Manual Muscle Tester; and physical function by ‘timed up and go’ (TUG) and walking speed (WS) over 6 meters. Body composition data from a female reference group (n = 62, mean age 29 years) provided cut-off values for defining sarcopenia. Results: Elderly women had higher body mass index (P < 0.001), lower lean mass (P < 0.001), and higher fat mass (P < 0.01) than the young reference group. Only a small proportion (3.2%) had absolute sarcopenia (defined by appendicular skeletal muscle mass/height squared) whereas 37% had relative sarcopenia class II (defined by percentage skeletal muscle mass). Scores for TUG and WS indicated relatively poor physical function, yet these measures were not associated with muscle mass or indices of sarcopenia. In multivariate analysis, only hip abductor strength predicted both TUG and WS (both P = 0.01). Conclusion: Hip strength is a more important indicator of physical functioning than lean mass. Measurement of hip strength may therefore be a useful screening tool to detect those at risk of functional decline and requirement for additional care. Further longitudinal studies with a range of other strength measures are warranted. PMID:21472094

The Quételet index revisited in children and adults.

PubMed

Chiquete, Erwin; Ruiz-Sandoval, José L; Ochoa-Guzmán, Ana; Sánchez-Orozco, Laura V; Lara-Zaragoza, Erika B; Basaldúa, Nancy; Ruiz-Madrigal, Bertha; Martínez-López, Erika; Román, Sonia; Godínez-Gutiérrez, Sergio A; Panduro, Arturo

2014-02-01

The body mass index (BMI) is based on the original concept that body weight increases as a function of height squared. As an indicator of obesity the modern BMI assumption postulates that adiposity also increases as a function of height in states of positive energy balance. To evaluate the BMI concept across different adiposity magnitudes, in both children and adults. We studied 975 individuals who underwent anthropometric evaluation: 474 children and 501 adults. Tetrapolar bioimpedance analysis was used to assess body fat and lean mass. BMI significantly correlated with percentage of body fat (%BF; children: r=0.893; adults: r=0.878) and with total fat mass (children: r=0.967; adults: r=0.953). In children, body weight, fat mass, %BF and waist circumference progressively increased as a function of height squared. In adults body weight increased as a function of height squared, but %BF actually decreased with increasing height both in men (r=-0.406; p<0.001) and women (r=-0.413; p<0.001). Most of the BMI variance in adults was explained by a positive correlation of total lean mass with height squared (r(2)=0.709), and by a negative correlation of BMI with total fat mass (r=-0.193). Body weight increases as a function of height squared. However, adiposity progressively increases as a function of height only in children. BMI is not an ideal indicator of obesity in adults since it is significantly influenced by the lean mass, even in obese individuals. Copyright © 2013 SEEN. Published by Elsevier Espana. All rights reserved.

Poor physical function in elderly women in low-level aged care is related to muscle strength rather than to measures of sarcopenia.

PubMed

Woods, Julie L; Iuliano-Burns, Sandra; King, Susannah J; Strauss, Boyd J; Walker, Karen Z

2011-01-01

To determine the prevalence of sarcopenia and investigate relationships among body composition, muscle strength, and physical function in elderly women in low-level aged care. Sixty-three ambulatory women (mean age 86 years) participated in this cross-sectional study where body composition was determined by dual energy X-ray absorptiometry (DXA); ankle, knee, and hip strength by the Nicholas Manual Muscle Tester; and physical function by 'timed up and go' (TUG) and walking speed (WS) over 6 meters. Body composition data from a female reference group (n = 62, mean age 29 years) provided cut-off values for defining sarcopenia. Elderly women had higher body mass index (P < 0.001), lower lean mass (P < 0.001), and higher fat mass (P < 0.01) than the young reference group. Only a small proportion (3.2%) had absolute sarcopenia (defined by appendicular skeletal muscle mass/height squared) whereas 37% had relative sarcopenia class II (defined by percentage skeletal muscle mass). Scores for TUG and WS indicated relatively poor physical function, yet these measures were not associated with muscle mass or indices of sarcopenia. In multivariate analysis, only hip abductor strength predicted both TUG and WS (both P = 0.01). Hip strength is a more important indicator of physical functioning than lean mass. Measurement of hip strength may therefore be a useful screening tool to detect those at risk of functional decline and requirement for additional care. Further longitudinal studies with a range of other strength measures are warranted.

Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time.

PubMed

Zhang, Zhi-Yu; Romano, D; Ivison, R J; Papadopoulos, Padelis P; Matteucci, F

2018-06-01

All measurements of cosmic star formation must assume an initial distribution of stellar masses-the stellar initial mass function-in order to extrapolate from the star-formation rate measured for typically rare, massive stars (of more than eight solar masses) to the total star-formation rate across the full stellar mass spectrum 1 . The shape of the stellar initial mass function in various galaxy populations underpins our understanding of the formation and evolution of galaxies across cosmic time 2 . Classical determinations of the stellar initial mass function in local galaxies are traditionally made at ultraviolet, optical and near-infrared wavelengths, which cannot be probed in dust-obscured galaxies 2,3 , especially distant starbursts, whose apparent star-formation rates are hundreds to thousands of times higher than in the Milky Way, selected at submillimetre (rest-frame far-infrared) wavelengths 4,5 . The 13 C/ 18 O isotope abundance ratio in the cold molecular gas-which can be probed via the rotational transitions of the 13 CO and C 18 O isotopologues-is a very sensitive index of the stellar initial mass function, with its determination immune to the pernicious effects of dust. Here we report observations of 13 CO and C 18 O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three, and find unambiguous evidence for a top-heavy stellar initial mass function in all of them. A low 13 CO/C 18 O ratio for all our targets-alongside a well tested, detailed chemical evolution model benchmarked on the Milky Way 6 -implies that there are considerably more massive stars in starburst events than in ordinary star-forming spiral galaxies. This can bring these extraordinary starbursts closer to the 'main sequence' of star-forming galaxies 7 , although such main-sequence galaxies may not be immune to changes in initial stellar mass function, depending on their star-formation densities.

CHARACTERIZING THE BROWN DWARF FORMATION CHANNELS FROM THE INITIAL MASS FUNCTION AND BINARY-STAR DYNAMICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thies, Ingo; Pflamm-Altenburg, Jan; Kroupa, Pavel

2015-02-10

The stellar initial mass function (IMF) is a key property of stellar populations. There is growing evidence that the classical star-formation mechanism by the direct cloud fragmentation process has difficulties reproducing the observed abundance and binary properties of brown dwarfs and very-low-mass stars. In particular, recent analytical derivations of the stellar IMF exhibit a deficit of brown dwarfs compared to observational data. Here we derive the residual mass function of brown dwarfs as an empirical measure of the brown dwarf deficiency in recent star-formation models with respect to observations and show that it is compatible with the substellar part ofmore » the Thies-Kroupa IMF and the mass function obtained by numerical simulations. We conclude that the existing models may be further improved by including a substellar correction term that accounts for additional formation channels like disk or filament fragmentation. The term ''peripheral fragmentation'' is introduced here for such additional formation channels. In addition, we present an updated analytical model of stellar and substellar binarity. The resulting binary fraction and the dynamically evolved companion mass-ratio distribution are in good agreement with observational data on stellar and very-low-mass binaries in the Galactic field, in clusters, and in dynamically unprocessed groups of stars if all stars form as binaries with stellar companions. Cautionary notes are given on the proper analysis of mass functions and the companion mass-ratio distribution and the interpretation of the results. The existence of accretion disks around young brown dwarfs does not imply that these form just like stars in direct fragmentation.« less

A lower bound on the Milky Way mass from general phase-space distribution function models

NASA Astrophysics Data System (ADS)

Bratek, Łukasz; Sikora, Szymon; Jałocha, Joanna; Kutschera, Marek

2014-02-01

We model the phase-space distribution of the kinematic tracers using general, smooth distribution functions to derive a conservative lower bound on the total mass within ≈150-200 kpc. By approximating the potential as Keplerian, the phase-space distribution can be simplified to that of a smooth distribution of energies and eccentricities. Our approach naturally allows for calculating moments of the distribution function, such as the radial profile of the orbital anisotropy. We systematically construct a family of phase-space functions with the resulting radial velocity dispersion overlapping with the one obtained using data on radial motions of distant kinematic tracers, while making no assumptions about the density of the tracers and the velocity anisotropy parameter β regarded as a function of the radial variable. While there is no apparent upper bound for the Milky Way mass, at least as long as only the radial motions are concerned, we find a sharp lower bound for the mass that is small. In particular, a mass value of 2.4 × 1011 M⊙, obtained in the past for lower and intermediate radii, is still consistent with the dispersion profile at larger radii. Compared with much greater mass values in the literature, this result shows that determining the Milky Way mass is strongly model-dependent. We expect a similar reduction of mass estimates in models assuming more realistic mass profiles. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A134

X-ray View of Four High-Luminosity Swift-BAT AGN: Unveiling Obscuration and Reflection with Suzaku

NASA Technical Reports Server (NTRS)

Fiorettil, V.; Angelini, L.; Mushotzky, R. F.; Koss, M.; Malaguti, G.

2013-01-01

Aims. A complete census of obscured Active Galactic Nuclei (AGN) is necessary to reveal the history of the super massive black hole (SMBH) growth and galaxy evolution in the Universe given the complex feedback processes and the fact that much of this growth occurs in an obscured phase. In this context, hard X-ray surveys and dedicated follow-up observations represent a unique tool for selecting highly absorbed AGN and for characterizing the obscuring matter surrounding the SMBH. Here we focus on the absorption and reflection occurring in highly luminous, quasar-like AGN, to study the relation between the geometry of the absorbing matter and the AGN nature (e.g. X-ray, optical, and radio properties), and to help to determine the column density dependency on the AGN luminosity. Methods. The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10(exp -11) erg per square centimeter and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 less than LogLBAT less than 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis, adding an original spectral analysis when non was available from the literature. Results. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption (N(sub H) approximately 4 × 10(exp 23) per square centimeter) and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (less than 0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density, X-ray luminosity and radio morphology, but shows a strong long-term variability in flux and scattering fraction, consistent with the soft emission being scattered from a distant region (e.g., the narrow emission line region). The sample presents high (greater than 100) X-to- [OIII] luminosity ratios, with an extreme value of R(sup X)(sub [OIII]) approximately 800 for 3C 452, confirming the [OIII] luminosity to be affected by residual extinction in presence of mild absorption, especially for "buried" AGN such as 3C 452. Three of our targets are powerful FRII radio galaxies, which is shown by their high luminosity and absorption; this makes them the most luminous and absorbed AGN of the BAT Seyfert survey despite the inversely proportional N(sub H) - L(sub X) relation.

Observing Cool Dust Around Active Galactic Nuclei Using the Sofia Telescope

NASA Astrophysics Data System (ADS)

Fuller, Lindsay

2017-02-01

Dust surrounding the supermassive black holes (SMBH) in active galactic nuclei (AGN) intercepts high-energy radiation caused by material rapidly encircling the black hole. The dust re-radiates at low-energy mid-infrared (MIR) wavelengths, which are highly attenuated by water vapor in the Earth's atmosphere. For ground-based telescopes, the atmosphere is completely opaque from 30 microns to the submillimeter regime, making ground-based observations at wavelengths longer than 30 microns impossible. Space-based telescopes can be costly, and are oftentimes very small (< 1 m). As an alternative, NASA built the Stratospheric Observatory For Infrared Astronomy (SOFIA) aircraft, a 2.5-m telescope carried on board a Boeing 747 airframe. In this dissertation, new photometric observations of 15 AGN are analyzed. They were obtained during Observing Cycles 2 and 4 on the SOFIA telescope using the 31.5 and 37.1 micron filters on the Faint Object infraRed CAmera for the SOFIA Telescope (FORCAST). NGC 1068 was observed in the 19.7, 31.5, and 37.1 micron filters using FORCAST, as well as the 53 micron filter on the HAWC+ instrument. Observed differences in AGN properties are largely explained by a unified model in which dust fills a toroidal region surrounding the SMBH, blocking direct view of the center in some lines of sight. Observations show that this dust lies in the central 1 - 10 pc from the black hole. Subarcsecond-resolution photometric and spectroscopic data between 1 - 20 microns have been used to compute the nuclear spectral energy distributions (SEDs) of the torus for most objects in this sample. Although these previous studies have effectively described torus model parameters, the lack of high spatial resolution observations at longer wavelengths leaves the SED largely unconstrained. Without 31.5 micron data, the model tends to overestimate the SED output and wavelength of peak emission, which is tentatively found between 30 - 40 microns. Including the 31.5 micron nuclear flux in the SED 1) reduces the number of clumpy torus models compatible with the data, and 2) modifies the model output for the outer radial extent of the torus. These observations of the central 0.1 - 1 kpc ( 3 - 4 arseconds) of the AGN sample are the highest resolution images available in the 30 - 40 micron wavelength range. However, for AGN at distances on the order of tens of Mpc, SOFIA cannot resolve the parsec-scale torus structure, and contamination from diffuse IR emission and star formation (SF) can contaminate nuclear observations. This dissertation focuses on isolating torus emission from diffuse extended emission in order to 1) add 30 - 40 micron photometric data to the IR SED of the torus and its model parameters, and 2) identify the origin of diffuse extended emission. Extended emission within the FWHM of SOFIA that is not associated with SF ostensibly originates in the narrow line region.

Starburst clusters in the Galactic center

NASA Astrophysics Data System (ADS)

Habibi, Maryam

2014-09-01

The central region of the Galaxy is the most active site of star formation in the Milky Way, where massive stars have formed very recently and are still forming today. The rich population of massive stars in the Galactic center provide a unique opportunity to study massive stars in their birth environment and probe their initial mass function, which is the spectrum of stellar masses at their birth. The Arches cluster is the youngest among the three massive clusters in the Galactic center, providing a collection of high-mass stars and a very dense core which makes this cluster an excellent site to address questions about massive star formation, the stellar mass function and the dynamical evolution of massive clusters in the Galactic center. In this thesis, I perform an observational study of the Arches cluster using K_{s}-band imaging obtained with NAOS/CONICA at the VLT combined with Subaru/Cisco J-band data to gain a full understanding of the cluster mass distribution out to its tidal radius for the first time. Since the light from the Galactic center reaches us through the Galactic disc, the extinction correction is crucial when studying this region. I use a Bayesian method to construct a realistic extinction map of the cluster. It is shown in this study that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, I show that the difference can reach up to 30% for individually derived stellar masses and Δ A_{Ks}˜ 1 magnitude in acquired K_{s}-band extinction, while the present-day mass function slope changes by ˜ 0.17 dex. The present-day mass function slope derived assuming the more recent extinction law, which suggests a steeper wavelength dependence for the infrared extinction law, reveals an overpopulation of massive stars in the core (r<0.2 pc) with a flat slope of α_{Nishi}=-1.50 ±0.35 in comparison to the Salpeter slope of α=-2.3. The slope of the mass function increases to α_{Nishi}=-2.21 ±0.27 in the intermediate annulus (0.2

Center-of-Mass Tomography and Wigner Function for Multimode Photon States

NASA Astrophysics Data System (ADS)

Dudinets, Ivan V.; Man'ko, Vladimir I.

2018-06-01

Tomographic probability representation of multimode electromagnetic field states in the scheme of center-of-mass tomography is reviewed. Both connection of the field state Wigner function and observable Weyl symbols with the center-of-mass tomograms as well as connection of the Grönewold kernel with the center-of-mass tomographic kernel determining the noncommutative product of the tomograms are obtained. The dual center-of-mass tomogram of the photon states are constructed and the dual tomographic kernel is obtained. The models of other generalized center-of-mass tomographies are discussed. Example of two-mode even and odd Schrödinger cat states is presented in details.

Ages of young star clusters, massive blue stragglers, and the upper mass limit of stars: Analyzing age-dependent stellar mass functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, F. R. N.; Izzard, R. G.; Langer, N.

2014-01-10

Massive stars rapidly change their masses through strong stellar winds and mass transfer in binary systems. The latter aspect is important for populations of massive stars as more than 70% of all O stars are expected to interact with a binary companion during their lifetime. We show that such mass changes leave characteristic signatures in stellar mass functions of young star clusters that can be used to infer their ages and to identify products of binary evolution. We model the observed present-day mass functions of the young Galactic Arches and Quintuplet star clusters using our rapid binary evolution code. Wemore » find that the shaping of the mass function by stellar wind mass loss allows us to determine the cluster ages as 3.5 ± 0.7 Myr and 4.8 ± 1.1 Myr, respectively. Exploiting the effects of binary mass exchange on the cluster mass function, we find that the most massive stars in both clusters are rejuvenated products of binary mass transfer, i.e., the massive counterpart of classical blue straggler stars. This resolves the problem of an apparent age spread among the most luminous stars exceeding the expected duration of star formation in these clusters. We perform Monte Carlo simulations to probe stochastic sampling, which support the idea of the most massive stars being rejuvenated binary products. We find that the most massive star is expected to be a binary product after 1.0 ± 0.7 Myr in Arches and after 1.7 ± 1.0 Myr in Quintuplet. Today, the most massive 9 ± 3 stars in Arches and 8 ± 3 in Quintuplet are expected to be such objects. Our findings have strong implications for the stellar upper mass limit and solve the discrepancy between the claimed 150 M {sub ☉} limit and observations of four stars with initial masses of 165-320 M {sub ☉} in R136 and of supernova 2007bi, which is thought to be a pair-instability supernova from an initial 250 M {sub ☉} star. Using the stellar population of R136, we revise the upper mass limit to values in the range 200-500 M {sub ☉}.« less

Ages of Young Star Clusters, Massive Blue Stragglers, and the Upper Mass Limit of Stars: Analyzing Age-dependent Stellar Mass Functions

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Izzard, R. G.; de Mink, S. E.; Langer, N.; Stolte, A.; de Koter, A.; Gvaramadze, V. V.; Hußmann, B.; Liermann, A.; Sana, H.

2014-01-01

Massive stars rapidly change their masses through strong stellar winds and mass transfer in binary systems. The latter aspect is important for populations of massive stars as more than 70% of all O stars are expected to interact with a binary companion during their lifetime. We show that such mass changes leave characteristic signatures in stellar mass functions of young star clusters that can be used to infer their ages and to identify products of binary evolution. We model the observed present-day mass functions of the young Galactic Arches and Quintuplet star clusters using our rapid binary evolution code. We find that the shaping of the mass function by stellar wind mass loss allows us to determine the cluster ages as 3.5 ± 0.7 Myr and 4.8 ± 1.1 Myr, respectively. Exploiting the effects of binary mass exchange on the cluster mass function, we find that the most massive stars in both clusters are rejuvenated products of binary mass transfer, i.e., the massive counterpart of classical blue straggler stars. This resolves the problem of an apparent age spread among the most luminous stars exceeding the expected duration of star formation in these clusters. We perform Monte Carlo simulations to probe stochastic sampling, which support the idea of the most massive stars being rejuvenated binary products. We find that the most massive star is expected to be a binary product after 1.0 ± 0.7 Myr in Arches and after 1.7 ± 1.0 Myr in Quintuplet. Today, the most massive 9 ± 3 stars in Arches and 8 ± 3 in Quintuplet are expected to be such objects. Our findings have strong implications for the stellar upper mass limit and solve the discrepancy between the claimed 150 M ⊙ limit and observations of four stars with initial masses of 165-320 M ⊙ in R136 and of supernova 2007bi, which is thought to be a pair-instability supernova from an initial 250 M ⊙ star. Using the stellar population of R136, we revise the upper mass limit to values in the range 200-500 M ⊙.

Preserving Healthy Muscle during Weight Loss123

PubMed Central

Cava, Edda; Yeat, Nai Chien; Mittendorfer, Bettina

2017-01-01

Weight loss is the cornerstone of therapy for people with obesity because it can ameliorate or completely resolve the metabolic risk factors for diabetes, coronary artery disease, and obesity-associated cancers. The potential health benefits of diet-induced weight loss are thought to be compromised by the weight-loss–associated loss of lean body mass, which could increase the risk of sarcopenia (low muscle mass and impaired muscle function). The objective of this review is to provide an overview of what is known about weight-loss–induced muscle loss and its implications for overall physical function (e.g., ability to lift items, walk, and climb stairs). The currently available data in the literature show the following: 1) compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality; 2) diet-induced weight loss reduces muscle mass without adversely affecting muscle strength; 3) weight loss improves global physical function, most likely because of reduced fat mass; 4) high protein intake helps preserve lean body and muscle mass during weight loss but does not improve muscle strength and could have adverse effects on metabolic function; 5) both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength. We therefore conclude that weight-loss therapy, including a hypocaloric diet with adequate (but not excessive) protein intake and increased physical activity (particularly resistance-type exercise), should be promoted to maintain muscle mass and improve muscle strength and physical function in persons with obesity. PMID:28507015

Cuban Mass Media: Organization, Control and Functions. Journalism Monographs Number Seventy-Eight.

ERIC Educational Resources Information Center

Nichols, John Spicer

The mass media as interdependent parts of a larger social system both control and are controlled by other subsystems. The various combinations of control, in turn, determine the functions the media system will serve. In the 1960's, the Cuban mass media underwent frequent change that reflected the volatility of the revolutionary process. Today,…

A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters

NASA Astrophysics Data System (ADS)

Baumgardt, H.; Hilker, M.

2018-05-01

We have determined masses, stellar mass functions and structural parameters of 112 Milky Way globular clusters by fitting a large set of N-body simulations to their velocity dispersion and surface density profiles. The velocity dispersion profiles were calculated based on a combination of more than 15,000 high-precision radial velocities which we derived from archival ESO/VLT and Keck spectra together with ˜20, 000 published radial velocities from the literature. Our fits also include the stellar mass functions of the globular clusters, which are available for 47 clusters in our sample, allowing us to self-consistently take the effects of mass segregation and ongoing cluster dissolution into account. We confirm the strong correlation between the global mass functions of globular clusters and their relaxation times recently found by Sollima & Baumgardt (2017). We also find a correlation of the escape velocity from the centre of a globular cluster and the fraction of first generation stars (FG) in the cluster recently derived for 57 globular clusters by Milone et al. (2017), but no correlation between the FG star fraction and the global mass function of a globular cluster. This could indicate that the ability of a globular cluster to keep the wind ejecta from the polluting star(s) is the crucial parameter determining the presence and fraction of second generation stars and not its later dynamical mass loss.

Seismic design of passive tuned mass damper parameters using active control algorithm

NASA Astrophysics Data System (ADS)

Chang, Chia-Ming; Shia, Syuan; Lai, Yong-An

2018-07-01

Tuned mass dampers are a widely-accepted control method to effectively reduce the vibrations of tall buildings. A tuned mass damper employs a damped harmonic oscillator with specific dynamic characteristics, thus the response of structures can be regulated by the additive dynamics. The additive dynamics are, however, similar to the feedback control system in active control. Therefore, the objective of this study is to develop a new tuned mass damper design procedure based on the active control algorithm, i.e., the H2/LQG control. This design facilitates the similarity of feedback control in the active control algorithm to determine the spring and damper in a tuned mass damper. Given a mass ratio between the damper and structure, the stiffness and damping coefficient of the tuned mass damper are derived by minimizing the response objective function of the primary structure, where the structural properties are known. Varying a single weighting in this objective function yields the optimal TMD design when the minimum peak in the displacement transfer function of the structure with the TMD is met. This study examines various objective functions as well as derives the associated equations to compute the stiffness and damping coefficient. The relationship between the primary structure and optimal tuned mass damper is parametrically studied. Performance is evaluated by exploring the h2-and h∞-norms of displacements and accelerations of the primary structure. In time-domain analysis, the damping effectiveness of the tune mass damper controlled structures is investigated under impulse excitation. Structures with the optimal tuned mass dampers are also assessed under seismic excitation. As a result, the proposed design procedure produces an effective tuned mass damper to be employed in a structure against earthquakes.

The Average Star Formation Histories of Galaxies in Dark Matter Halos from z = 0-8

NASA Astrophysics Data System (ADS)

Behroozi, Peter S.; Wechsler, Risa H.; Conroy, Charlie

2013-06-01

We present a robust method to constrain average galaxy star formation rates (SFRs), star formation histories (SFHs), and the intracluster light (ICL) as a function of halo mass. Our results are consistent with observed galaxy stellar mass functions, specific star formation rates (SSFRs), and cosmic star formation rates (CSFRs) from z = 0 to z = 8. We consider the effects of a wide range of uncertainties on our results, including those affecting stellar masses, SFRs, and the halo mass function at the heart of our analysis. As they are relevant to our method, we also present new calibrations of the dark matter halo mass function, halo mass accretion histories, and halo-subhalo merger rates out to z = 8. We also provide new compilations of CSFRs and SSFRs; more recent measurements are now consistent with the buildup of the cosmic stellar mass density at all redshifts. Implications of our work include: halos near 1012 M ⊙ are the most efficient at forming stars at all redshifts, the baryon conversion efficiency of massive halos drops markedly after z ~ 2.5 (consistent with theories of cold-mode accretion), the ICL for massive galaxies is expected to be significant out to at least z ~ 1-1.5, and dwarf galaxies at low redshifts have higher stellar mass to halo mass ratios than previous expectations and form later than in most theoretical models. Finally, we provide new fitting formulae for SFHs that are more accurate than the standard declining tau model. Our approach places a wide variety of observations relating to the SFH of galaxies into a self-consistent framework based on the modern understanding of structure formation in ΛCDM. Constraints on the stellar mass-halo mass relationship and SFRs are available for download online.

An ALMA Archival Study of the Clump Mass Function in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Brunetti, Nathan

2017-11-01

This thesis presents 1.3 mm and 3.1 mm continuum maps of seven star forming regions within the Large Magellanic Cloud (LMC) as observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). The data were taken as part of six projects retrieved from the ALMA public archive plus one project observed specifically for this work. We developed a technique to combine Band 3 and Band 6 maps to estimate dust-only emission corrected for free-free emission contamination. We also present an automated clean masking script, with a listing of the code, which we adapted and used for all of the imaging in this thesis. From these observations we identify 32 molecular clumps in the LMC and estimate their total mass from their dust emission. We derive a cumulative clump mass function (N(≥M) ≈ M(α+1)) and fit it with a double power law to find α_low = -1.76+0.07-0.1, α_high = -3.3+0.3-0.6, and a break mass of 2500+700-300 M⊙. Comparing to the clump mass function derived by Indebetouw et al. (2013) from carbon monoxide spectral line emission for 30 Doradus-10 shows a consistent mass range of clumps between 205 M⊙ and 5740 M⊙ as well as consistency between their single power law fit and our low mass power law index. Also comparing to core and clump mass functions from several star forming regions in the Milky Way we find consistency between most of their high mass indices and our low mass index, which is where the clump mass ranges overlap.

The He I 2.06 microns/Br-gamma ratio in starburst galaxies - An objective constraint on the upper mass limit to the initial mass function

NASA Technical Reports Server (NTRS)

Doyon, Rene; Puxley, P. J.; Joseph, R. D.

1992-01-01

The use of the He I 2.06 microns/Br-gamma ratio as a constraint on the massive stellar population in star-forming galaxies is developed. A theoretical relationship between the He I 2.06 microns/Br-gamma ratio and the effective temperature of the exciting star in H II regions is derived. The effects of collisional excitation and dust within the nebula on the ratio are also considered. It is shown that the He I 2.06 microns/Br-gamma ratio is a steep function of the effective temperature, a property which can be used to determine the upper mass limit of the initial mass function (IMF) in galaxies. This technique is reliable for upper mass limits less than about 40 solar masses. New near-infrared spectra of starburst galaxies are presented. The He I 2.06 microns/Br-gamma ratios observed imply a range of upper mass limits from 27 to over 40 solar masses. There is also evidence that the upper mass limit is spatially dependent within a given galaxy. These results suggest that the upper mass limit is not a uniquely defined parameter of the IMF and probably varies with local physical conditions.

Calibrating First-Order Strong Lensing Mass Estimates in Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Reed, Brendan; Remolian, Juan; Sharon, Keren; Li, Nan; SPT Clusters Cooperation

2018-01-01

We investigate methods to reduce the statistical and systematic errors inherent to using the Einstein Radius as a first-order mass estimate in strong lensing galaxy clusters. By finding an empirical universal calibration function, we aim to enable a first-order mass estimate of large cluster data sets in a fraction of the time and effort of full-scale strong lensing mass modeling. We use 74 simulated cluster data from the Argonne National Laboratory in a lens redshift slice of [0.159, 0.667] with various source redshifts in the range of [1.23, 2.69]. From the simulated density maps, we calculate the exact mass enclosed within the Einstein Radius. We find that the mass inferred from the Einstein Radius alone produces an error width of ~39% with respect to the true mass. We explore an array of polynomial and exponential correction functions with dependence on cluster redshift and projected radii of the lensed images, aiming to reduce the statistical and systematic uncertainty. We find that the error on the the mass inferred from the Einstein Radius can be reduced significantly by using a universal correction function. Our study has implications for current and future large galaxy cluster surveys aiming to measure cluster mass, and the mass-concentration relation.

Giant Planet Occurrence Rate as a Function of Stellar Mass

NASA Astrophysics Data System (ADS)

Reffert, Sabine; Bergmann, Christoph; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas

2013-07-01

For over 12 years we have carried out a Doppler survey at Lick Observatory, identifying 15 planets and 20 candidate planets in a sample of 373 G and K giant stars. We investigate giant planet occurrence rate as a function of stellar mass and metallicity in this sample, which covers the mass range from about 1 to 3.5-5.0 solar masses. We confirm the presence of a strong planet-metallicity correlation in our giant star sample, which is fully consistent with the well-known planet-metallicity correlation for main-sequence stars. Furthermore, we find a very strong dependence of the giant planet occurrence rate on stellar mass, which we fit with a gaussian distribution. Stars with masses of about 1.9 solar masses have the highest probability of hosting a giant planet, whereas the planet occurrence rate drops rapidly for masses larger than 2.5 to 3.0 solar masses. We do not find any planets around stars more massive than 2.7 solar masses, although we have 113 stars with masses between 2.7 and 5.0 solar masses in our sample (planet occurrence rate in that mass range: 0% +1.6% at 68.3% confidence). This result is not due to a bias related to planet detectability as a function of stellar mass. We conclude that larger mass stars do not form giant planets which are observable at orbital distances of a few AU today. Possible reasons include slower growth rate due to the snow-line being located further out, longer migration timescale and faster disk depletion.

Initial mass function of planetesimals formed by the streaming instability

NASA Astrophysics Data System (ADS)

Schäfer, Urs; Yang, Chao-Chin; Johansen, Anders

2017-01-01

The streaming instability is a mechanism to concentrate solid particles into overdense filaments that undergo gravitational collapse and form planetesimals. However, it remains unclear how the initial mass function of these planetesimals depends on the box dimensions of numerical simulations. To resolve this, we perform simulations of planetesimal formation with the largest box dimensions to date, allowing planetesimals to form simultaneously in multiple filaments that can only emerge within such large simulation boxes. In our simulations, planetesimals with sizes between 80 km and several hundred kilometers form. We find that a power law with a rather shallow exponential cutoff at the high-mass end represents the cumulative birth mass function better than an integrated power law. The steepness of the exponential cutoff is largely independent of box dimensions and resolution, while the exponent of the power law is not constrained at the resolutions we employ. Moreover, we find that the characteristic mass scale of the exponential cutoff correlates with the mass budget in each filament. Together with previous studies of high-resolution simulations with small box domains, our results therefore imply that the cumulative birth mass function of planetesimals is consistent with an exponentially tapered power law with a power-law exponent of approximately -1.6 and a steepness of the exponential cutoff in the range of 0.3-0.4.

Negative effective mass in acoustic metamaterial with nonlinear mass-in-mass subsystems

NASA Astrophysics Data System (ADS)

Cveticanin, L.; Zukovic, M.

2017-10-01

In this paper the dynamics of the nonlinear mass-in-mass system as the basic subsystem of the acoustic metamaterial is investigated. The excitation of the system is in the form of the Jacobi elliptic function. The corresponding model to this forcing is the mass-in-mass system with cubic nonlinearity of the Duffing type. Mathematical model of the motion is a system of two coupled strong nonlinear and nonhomogeneous second order differential equations. Particular solution to the system is obtained. The analytical solution of the problem is based on the simple and double integral of the cosine Jacobi function. In the paper the integrals are given in the form of series of trigonometric functions. These results are new one. After some modification the simplified solution in the first approximation is obtained. The result is convenient for discussion. Conditions for elimination of the motion of the mass 1 by connection of the nonlinear dynamic absorber (mass - spring system) are defined. In the consideration the effective mass ratio is introduced in the nonlinear mass-in-mass system. Negative effective mass ratio gives the absorption of vibrations with certain frequencies. The advantage of the nonlinear subunit in comparison to the linear one is that the frequency gap is significantly wider. Nevertheless, it has to be mentioned that the amplitude of vibration differs from zero for a small value. In the paper the analytical results are compared with numerical one and are in agreement.

On the Mass Distribution of Animal Species

NASA Astrophysics Data System (ADS)

Redner, Sidney; Clauset, Aaron; Schwab, David

2009-03-01

We develop a simple diffusion-reaction model to account for the broad and asymmetric distribution of adult body masses for species within related taxonomic groups. The model assumes three basic evolutionary features that control body mass: (i) a fixed lower limit that is set by metabolic constraints, (ii) a species extinction risk that is a weakly increasing function of body mass, and (iii) cladogenetic diffusion, in which daughter species have a slight tendency toward larger mass. The steady-state solution for the distribution of species masses in this model can be expressed in terms of the Airy function. This solution gives mass distributions that are in good agreement with data on 4002 terrestrial mammal species from the late Quaternary and 8617 extant bird species.

Functional Body Composition and Related Aspects in Research on Obesity and Cachexia

PubMed Central

Müller, M.J.; Baracos, V.; Bosy-Westphal, A.; Dulloo, A.; Eckel, J.; Fearon, K.C.H.; Hall, K.D.; Pietrobelli, A.; Sørensen, T.I.A.; Speakman, J.; Trayhurn, P.; Visser, M.; Heymsfield, S.B.

2014-01-01

The 12th Stock Conference addressed body composition and related functions in two extreme situations, obesity and cancer cachexia. The concept of “functional body composition” integrates body components into regulatory systems relating the mass of organs and tissues to corresponding in vivo functions and metabolic processes. This concept adds to an understanding of organ/tissue mass and function in the context of metabolic adaptations to weight change and disease. During weight gain and loss there are associated changes in individual body components while the relationships between organ and tissue mass are fixed. Thus, an understanding of weight regulation involves an examination of organ-tissue regulation rather than of individual organ mass. The between organ/tissue mass relationships are associated with and explained by cross-talk between organs and tissues mediated by cytokines, hormones, and metabolites that are coupled with changes in body weight, composition, and function as observed in obesity and cancer cachexia. In addition to established roles in intermediary metabolism, cell function and inflammation, organ-tissue cross-talk mediators are determinants of body composition and its’ change with weight gain and loss. The 12th Stock Conference supported Michael Stocks’ concept of gaining new insights by integrating research ideas from obesity and cancer cachexia. The conference presentations provide an in-depth understanding of body composition and metabolism. PMID:24835453

Mass Media Functions, Knowledge and Social Control

ERIC Educational Resources Information Center

Donohue, G. A.; And Others

1973-01-01

Develops a macro-view of mass media as interdependent parts of a total social system including a series of interrelated subsystems with primary function involving the generation, dissemination, and assimilation of information. (RB)

Lower circulating insulin-like growth factor-I is associated with better cognition in females with exceptional longevity without compromise to muscle mass and function.

PubMed

Perice, Leland; Barzilai, Nir; Verghese, Joe; Weiss, Erica F; Holtzer, Roee; Cohen, Pinchas; Milman, Sofiya

2016-10-14

Mutations that reduce somatotropic signaling result in improved lifespan and health-span in model organisms and humans. However, whether reduced circulating insulin-like growth factor-I (IGF-I) level is detrimental to cognitive and muscle function in older adults remains understudied. A cross-sectional analysis was performed in Ashkenazi Jews with exceptional longevity (age ≥95 years). Cognition was assessed using the Mini-Mental State Examination and muscle function with the chair rise test, grip-strength, and gait speed. Muscle mass was estimated using the skeletal muscle index. Serum IGF-I was measured with liquid chromatography mass spectrometry. In gender stratified age-adjusted logistic regression analysis, females with IGF-I levels in the first tertile had lower odds of being cognitively impaired compared to females with IGF-I levels within the upper two tertiles, OR (95% CI) 0.39 (0.19-0.82). The result remained significant after adjustment for multiple parameters. No significant association was identified in males between IGF-I and cognition. No relationship was found between IGF-I tertiles and muscle function and muscle mass in females or males. Lower circulating IGF-I is associated with better cognitive function in females with exceptional longevity, with no detriment to skeletal muscle mass and function.

Winds from stripped low-mass helium stars and Wolf-Rayet stars

NASA Astrophysics Data System (ADS)

Vink, Jorick S.

2017-11-01

We present mass-loss predictions from Monte Carlo radiative transfer models for helium (He) stars as a function of stellar mass, down to 2 M⊙. Our study includes both massive Wolf-Rayet (WR) stars and low-mass He stars that have lost their envelope through interaction with a companion. For these low-mass He stars we predict mass-loss rates that are an order of magnitude smaller than by extrapolation of empirical WR mass-loss rates. Our lower mass-loss rates make it harder for these elusive stripped stars to be discovered via line emission, and we should attempt to find these stars through alternative methods instead. Moreover, lower mass-loss rates make it less likely that low-mass He stars provide stripped-envelope supernovae (SNe) of type Ibc. We express our mass-loss predictions as a function of L and Z and not as a function of the He abundance, as we do not consider this physically astute given our earlier work. The exponent of the M⊙ versus Z dependence is found to be 0.61, which is less steep than relationships derived from recent empirical atmospheric modelling. Our shallower exponent will make it more challenging to produce "heavy" black holes of order 40 M⊙, as recently discovered in the gravitational wave event GW 150914, making low metallicity for these types of events even more necessary.

THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. IV. A PROBABILISTIC APPROACH TO INFERRING THE HIGH-MASS STELLAR INITIAL MASS FUNCTION AND OTHER POWER-LAW FUNCTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisz, Daniel R.; Fouesneau, Morgan; Dalcanton, Julianne J.

2013-01-10

We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M {approx}> 1 M {sub Sun }). Using simulated clusters and Markov Chain Monte Carlomore » sampling of the probability distribution functions, we show that estimates of the MF slope, {alpha}, are unbiased and that the uncertainty, {Delta}{alpha}, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on {alpha}, and provide an analytic approximation for {Delta}{alpha} as a function of the observed number of stars and mass range. Comparison with literature studies shows that {approx}3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield ({alpha}) = 2.46, with a 1{sigma} dispersion of 0.35 dex. We verify that it is impossible for a power-law MF to obtain meaningful constraints on the upper mass limit of the initial mass function, beyond the lower bound of the most massive star actually observed. We show that avoiding substantial biases in the MF slope requires (1) including the MF as a prior when deriving individual stellar mass estimates, (2) modeling the uncertainties in the individual stellar masses, and (3) fully characterizing and then explicitly modeling the completeness for stars of a given mass. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations. We briefly discuss how each of these effects can be incorporated into extensions of the present framework. Finally, we emphasize that the technique and lessons learned are applicable to more general problems involving power-law fitting.« less

Sarcopenia during neoadjuvant therapy for oesophageal cancer: characterising the impact on muscle strength and physical performance.

PubMed

Guinan, Emer M; Doyle, S L; Bennett, A E; O'Neill, L; Gannon, J; Elliott, J A; O'Sullivan, J; Reynolds, J V; Hussey, J

2018-05-01

Preoperative chemo(radio)therapy for oesophageal cancer (OC) may have an attritional impact on body composition and functional status, impacting postoperative outcome. Physical decline with skeletal muscle loss has not been previously characterised in OC and may be amenable to physical rehabilitation. This study characterises skeletal muscle mass and physical performance from diagnosis to post-neoadjuvant therapy in patients undergoing preoperative chemo(radio)therapy for OC. Measures of body composition (axial computerised tomography), muscle strength (handgrip), functional capacity (walking distance), anthropometry (weight, height and waist circumference), physical activity, quality-of-life and nutritional status were captured prospectively. Sarcopenia status was defined as pre-sarcopenic (low muscle mass only), sarcopenic (low muscle mass and low muscle strength or function) or severely sarcopenic (low muscle mass and low muscle strength and low muscle function). Twenty-eight participants were studied at both time points (mean age 62.86 ± 8.18 years, n = 23 male). Lean body mass reduced by 4.9 (95% confidence interval 3.2 to 6.7) kg and mean grip strength reduced by 4.3 (2.5 to 6.1) kg from pre- to post-neoadjuvant therapy. Quality-of-life scores capturing gastrointestinal symptoms improved. Measures of anthropometry, walking distance, physical activity and nutritional status did not change. There was an increase in sarcopenic status from diagnosis (pre-sarcopenic n = 2) to post-treatment (pre-sarcopenic n = 5, severely sarcopenic n = 1). Despite maintenance of body weight, functional capacity and activity habits, participants experience declines in muscle mass and strength. Interventions involving exercise and/or nutritional support to build muscle mass and strength during preoperative therapy, even in patients who are functioning normally, are warranted.

Some special features of Wigner’s mass formula for nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nurmukhamedov, A. M., E-mail: fattah52@mail.ru

2014-12-15

Experimental data on anomalous values of the empirical function b(A) in Wigner’s mass formula are presented, the application of Student’s t criterion in experimentally proving the restoration of Wigner’s SU(4) symmetry in nuclei is validated, and a physical interpretation of the basic parameter of the empirical function a(A) in Wigner’s mass formula is given.

Spatiotemporal variations in litter mass and their relationships with climate in temperate grassland: A case study from Xilingol grassland, Inner Mongolia (China)

NASA Astrophysics Data System (ADS)

Ren, Hongrui; Zhang, Bei

2018-02-01

Clarifying spatiotemporal variations of litter mass and their relationships with climate factors will advance our understanding of ecosystem structure and functioning in grasslands. Our objective is to investigate the spatiotemporal variations of litter mass in the growing season and their relationships with precipitation and temperature in the Xilingol grassland using MOD09A1 data. With widely used STI (simple tillage index), we firstly estimated the litter mass of Xilingol grassland in the growing season from 2000 to 2014. Then we investigated the variations of litter mass in the growing season at regional and site scales. We further explored the spatiotemporal relationships between litter mass and precipitation and temperature at both scales. The litter mass increased with increasing mean annual precipitation and decreasing mean annual temperature at regional scale. The variations of litter mass at given sites followed quadratic function curves in the growing season, and litter mass generally attained maximums between August 1 and September 1. Positive spatial relationship was observed between litter mass variations and precipitation, and negative spatial relationship was found between litter mass variations and temperature in the growing season. There was no significant relationship between inter-annual variations of litter mass and precipitation and temperature at given sites. Results illustrate that precipitation and temperature are important drivers in shaping ecosystem functioning as reflected in litter mass at regional scale in the Xilingol grassland. Our findings also suggest the action of distinct mechanism in controlling litter mass variations at regional and sites scales.

Mass functions for globular cluster main sequences based on CCD photometry and stellar models

NASA Astrophysics Data System (ADS)

McClure, Robert D.; Vandenberg, Don A.; Smith, Graeme H.; Fahlman, Gregory G.; Richer, Harvey B.; Hesser, James E.; Harris, William E.; Stetson, Peter B.; Bell, R. A.

1986-08-01

Main-sequence luminosity functions constructed from CCD observations of globular clusters reveal a strong trend in slope with metal abundance. Theoretical luminosity functions constructed from VandenBerg and Bell's (1985) isochrones have been fitted to the observations and reveal a trend between x, the power-law index of the mass function, and metal abundance. The most metal-poor clusters require an index of about x = 2.5, whereas the most metal-rich clusters exhibit an index of x of roughly -0.5. The luminosity functions for two sparse clusters, E3 and Pal 5, are distinct from those of the more massive clusters, in that they show a turndown which is possibly a result of mass loss or tidal disruption.

The galaxy-wide initial mass function of dwarf late-type to massive early-type galaxies

NASA Astrophysics Data System (ADS)

Weidner, C.; Kroupa, P.; Pflamm-Altenburg, J.; Vazdekis, A.

2013-12-01

Observational studies are showing that the galaxy-wide stellar initial mass function (IMF) is top-heavy in galaxies with high star formation rates (SFRs). Calculating the integrated galactic stellar initial mass function (IGIMF) as a function of the SFR of a galaxy, it follows that galaxies which have or which formed with SFRs >10 M⊙ yr-1 would have a top-heavy IGIMF in excellent consistency with the observations. Consequently and in agreement with observations, elliptical galaxies would have higher mass-to-light ratios as a result of the overabundance of stellar remnants compared to a stellar population that formed with an invariant canonical stellar IMF. For the Milky Way, the IGIMF yields very good agreement with the disc- and the bulge IMF determinations. Our conclusions are that purely stochastic descriptions of star formation on the scales of a parsec and above are falsified. Instead, star formation follows the laws, stated here as axioms, which define the IGIMF theory. We also find evidence that the power-law index β of the embedded cluster mass function decreases with increasing SFR. We propose further tests of the IGIMF theory through counting massive stars in dwarf galaxies.

Deviations from Born-Oppenheimer mass scaling in spectroscopy and ultracold molecular physics

NASA Astrophysics Data System (ADS)

Lutz, Jesse J.; Hutson, Jeremy M.

2016-12-01

We investigate Born-Oppenheimer breakdown (BOB) effects (beyond the usual mass scaling) for the electronic ground states of a series of homonuclear and heteronuclear alkali-metal diatoms, together with the Sr2 and Yb2 diatomics. Several widely available electronic structure software packages are used to calculate the leading contributions to the total isotope shift for commonly occurring isotopologs of each species. Computed quantities include diagonal Born-Oppenheimer corrections (mass shifts) and isotopic field shifts. Mass shifts dominate for light nuclei up to and including K, but field shifts contribute significantly for Rb and Sr and are dominant for Yb. We compare the ab initio mass-shift functions for Li2, LiK and LiRb with spectroscopically derived ground-state BOB functions from the literature. We find good agreement in the values of the functions for LiK and LiRb at their equilibrium geometries, but significant disagreement with the shapes of the functions for all 3 systems. The differences may be due to contributions of nonadiabatic terms to the empirical BOB functions. We present a semiclassical model for the effect of BOB corrections on the binding energies of near-threshold states and the positions of zero-energy Feshbach resonances.

LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kryukova, E.; Megeath, S. T.; Allen, T. S.

2012-08-15

We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Usingmore » protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity functions to those predicted by models and find that our observed luminosity functions are best matched by models that invoke competitive accretion, although we do not find strong agreement between the high-mass SF clouds and any of the models.« less

Statistics of primordial density perturbations from discrete seed masses

NASA Technical Reports Server (NTRS)

Scherrer, Robert J.; Bertschinger, Edmund

1991-01-01

The statistics of density perturbations for general distributions of seed masses with arbitrary matter accretion is examined. Formal expressions for the power spectrum, the N-point correlation functions, and the density distribution function are derived. These results are applied to the case of uncorrelated seed masses, and power spectra are derived for accretion of both hot and cold dark matter plus baryons. The reduced moments (cumulants) of the density distribution are computed and used to obtain a series expansion for the density distribution function. Analytic results are obtained for the density distribution function in the case of a distribution of seed masses with a spherical top-hat accretion pattern. More generally, the formalism makes it possible to give a complete characterization of the statistical properties of any random field generated from a discrete linear superposition of kernels. In particular, the results can be applied to density fields derived by smoothing a discrete set of points with a window function.

Prevalence of skeletal muscle mass loss and its association with swallowing function after cardiovascular surgery.

PubMed

Wakabayashi, Hidetaka; Takahashi, Rimiko; Watanabe, Naoko; Oritsu, Hideyuki; Shimizu, Yoshitaka

2017-06-01

The aim of this study was to assess the prevalence of skeletal muscle mass loss and its association with swallowing function in patients with dysphagia after cardiovascular surgery. A retrospective cohort study was performed in 65 consecutive patients with dysphagia after cardiovascular surgery who were prescribed speech therapy. Skeletal muscle index (SMI) was calculated as total psoas muscle area assessed via abdominal computed tomography divided by height squared. Cutoff values were 6.36 cm 2 /m 2 for men and 3.92 cm 2 /m 2 for women. The Food Intake Level Scale (FILS) was used to assess the swallowing function. Univariate and ordered logistic regression analyses were applied to examine the associations between skeletal muscle mass loss and dysphagia. The study included 50 men and 15 women (mean age 73 ± 8 y). The mean SMI was 4.72 ± 1.37 cm 2 /m 2 in men and 3.33 ± 1.42 cm 2 /m 2 in women. Skeletal muscle mass loss was found in 53 (82%) patients. Twelve had tracheostomy cannula. Thirteen were non-oral feeding (FILS levels 1-3), 5 were oral food intake and alternative nutrition (levels 4-6), and 47 were oral food intake alone (levels 7-9) at discharge. The FILS at discharge was significantly lower in patients with skeletal muscle mass loss. Ordered logistic regression analysis of swallowing function showed that skeletal muscle mass loss and tracheostomy cannula were associated independently with the FILS at discharge. The prevalence of skeletal muscle mass loss is very high, and skeletal muscle mass loss is associated with swallowing function. Copyright © 2017 Elsevier Inc. All rights reserved.

A Dual Power Law Distribution for the Stellar Initial Mass Function

NASA Astrophysics Data System (ADS)

Hoffmann, Karl Heinz; Essex, Christopher; Basu, Shantanu; Prehl, Janett

2018-05-01

We introduce a new dual power law (DPL) probability distribution function for the mass distribution of stellar and substellar objects at birth, otherwise known as the initial mass function (IMF). The model contains both deterministic and stochastic elements, and provides a unified framework within which to view the formation of brown dwarfs and stars resulting from an accretion process that starts from extremely low mass seeds. It does not depend upon a top down scenario of collapsing (Jeans) masses or an initial lognormal or otherwise IMF-like distribution of seed masses. Like the modified lognormal power law (MLP) distribution, the DPL distribution has a power law at the high mass end, as a result of exponential growth of mass coupled with equally likely stopping of accretion at any time interval. Unlike the MLP, a power law decay also appears at the low mass end of the IMF. This feature is closely connected to the accretion stopping probability rising from an initially low value up to a high value. This might be associated with physical effects of ejections sometimes (i.e., rarely) stopping accretion at early times followed by outflow driven accretion stopping at later times, with the transition happening at a critical time (therefore mass). Comparing the DPL to empirical data, the critical mass is close to the substellar mass limit, suggesting that the onset of nuclear fusion plays an important role in the subsequent accretion history of a young stellar object.

Plant litter functional diversity effects on litter mass loss depend on the macro-detritivore community.

PubMed

Patoine, Guillaume; Thakur, Madhav P; Friese, Julia; Nock, Charles; Hönig, Lydia; Haase, Josephine; Scherer-Lorenzen, Michael; Eisenhauer, Nico

2017-11-01

A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with detritivore diversity are key to advancing our understanding of litter mass loss in nature.

Plant litter functional diversity effects on litter mass loss depend on the macro-detritivore community

PubMed Central

Patoine, Guillaume; Thakur, Madhav P.; Friese, Julia; Nock, Charles; Hönig, Lydia; Haase, Josephine; Scherer-Lorenzen, Michael; Eisenhauer, Nico

2017-01-01

A better understanding of the mechanisms driving litter diversity effects on decomposition is needed to predict how biodiversity losses affect this crucial ecosystem process. In a microcosm study, we investigated the effects of litter functional diversity and two major groups of soil macro-detritivores on the mass loss of tree leaf litter mixtures. Furthermore, we tested the effects of litter trait community means and dissimilarity on litter mass loss for seven traits relevant to decomposition. We expected macro-detritivore effects on litter mass loss to be most pronounced in litter mixtures of high functional diversity. We used 24 leaf mixtures differing in functional diversity, which were composed of litter from four species from a pool of 16 common European tree species. Earthworms, isopods, or a combination of both were added to each litter combination for two months. Litter mass loss was significantly higher in the presence of earthworms than in that of isopods, whereas no synergistic effects of macro-detritivore mixtures were found. The effect of functional diversity of the litter material was highest in the presence of both macro-detritivore groups, supporting the notion that litter diversity effects are most pronounced in the presence of different detritivore species. Species-specific litter mass loss was explained by nutrient content, secondary compound concentration, and structural components. Moreover, dissimilarity in N concentrations increased litter mass loss, probably because detritivores having access to nutritionally diverse food sources. Furthermore, strong competition between the two macro-detritivores for soil surface litter resulted in a decrease of survival of both macro-detritivores. These results show that the effects of litter functional diversity on decomposition are contingent upon the macro-detritivore community and composition. We conclude that the temporal dynamics of litter trait diversity effects and their interaction with detritivore diversity are key to advancing our understanding of litter mass loss in nature. PMID:29180828

Mass functions from the excursion set model

NASA Astrophysics Data System (ADS)

Hiotelis, Nicos; Del Popolo, Antonino

2017-11-01

Aims: We aim to study the stochastic evolution of the smoothed overdensity δ at scale S of the form δ(S) = ∫0S K(S,u)dW(u), where K is a kernel and dW is the usual Wiener process. Methods: For a Gaussian density field, smoothed by the top-hat filter, in real space, we used a simple kernel that gives the correct correlation between scales. A Monte Carlo procedure was used to construct random walks and to calculate first crossing distributions and consequently mass functions for a constant barrier. Results: We show that the evolution considered here improves the agreement with the results of N-body simulations relative to analytical approximations which have been proposed from the same problem by other authors. In fact, we show that an evolution which is fully consistent with the ideas of the excursion set model, describes accurately the mass function of dark matter haloes for values of ν ≤ 1 and underestimates the number of larger haloes. Finally, we show that a constant threshold of collapse, lower than it is usually used, it is able to produce a mass function which approximates the results of N-body simulations for a variety of redshifts and for a wide range of masses. Conclusions: A mass function in good agreement with N-body simulations can be obtained analytically using a lower than usual constant collapse threshold.

Mapping the core mass function to the initial mass function

NASA Astrophysics Data System (ADS)

Guszejnov, Dávid; Hopkins, Philip F.

2015-07-01

It has been shown that fragmentation within self-gravitating, turbulent molecular clouds (`turbulent fragmentation') can naturally explain the observed properties of protostellar cores, including the core mass function (CMF). Here, we extend recently developed analytic models for turbulent fragmentation to follow the time-dependent hierarchical fragmentation of self-gravitating cores, until they reach effectively infinite density (and form stars). We show that turbulent fragmentation robustly predicts two key features of the initial mass function (IMF). First, a high-mass power-law scaling very close to the Salpeter slope, which is a generic consequence of the scale-free nature of turbulence and self-gravity. We predict the IMF slope (-2.3) is slightly steeper than the CMF slope (-2.1), owing to the slower collapse and easier fragmentation of large cores. Secondly, a turnover mass, which is set by a combination of the CMF turnover mass (a couple solar masses, determined by the `sonic scale' of galactic turbulence, and so weakly dependent on galaxy properties), and the equation of state (EOS). A `soft' EOS with polytropic index γ < 1.0 predicts that the IMF slope becomes `shallow' below the sonic scale, but fails to produce the full turnover observed. An EOS, which becomes `stiff' at sufficiently low surface densities Σgas ˜ 5000 M⊙ pc-2, and/or models, where each collapsing core is able to heat and effectively stiffen the EOS of a modest mass (˜0.02 M⊙) of surrounding gas, are able to reproduce the observed turnover. Such features are likely a consequence of more detailed chemistry and radiative feedback.

Counts of galaxy clusters as cosmological probes: the impact of baryonic physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balaguera-Antolínez, Andrés; Porciani, Cristiano, E-mail: abalan@astro.uni-bonn.de, E-mail: porciani@astro.uni-bonn.de

2013-04-01

The halo mass function from N-body simulations of collisionless matter is generally used to retrieve cosmological parameters from observed counts of galaxy clusters. This neglects the observational fact that the baryonic mass fraction in clusters is a random variable that, on average, increases with the total mass (within an overdensity of 500). Considering a mock catalog that includes tens of thousands of galaxy clusters, as expected from the forthcoming generation of surveys, we show that the effect of a varying baryonic mass fraction will be observable with high statistical significance. The net effect is a change in the overall normalizationmore » of the cluster mass function and a milder modification of its shape. Our results indicate the necessity of taking into account baryonic corrections to the mass function if one wants to obtain unbiased estimates of the cosmological parameters from data of this quality. We introduce the formalism necessary to accomplish this goal. Our discussion is based on the conditional probability of finding a given value of the baryonic mass fraction for clusters of fixed total mass. Finally, we show that combining information from the cluster counts with measurements of the baryonic mass fraction in a small subsample of clusters (including only a few tens of objects) will nearly optimally constrain the cosmological parameters.« less

A Universal Break in the Planet-to-star Mass-ratio Function of Kepler MKG Stars

NASA Astrophysics Data System (ADS)

Pascucci, Ilaria; Mulders, Gijs D.; Gould, Andrew; Fernandes, Rachel

2018-04-01

We follow the microlensing approach and quantify the occurrence of Kepler exoplanets as a function of planet-to-star mass ratio, q, rather than planet radius or mass. For planets with radii ∼1–6 R ⊕ and periods <100 days, we find that, except for a normalization factor, the occurrence rate versus q can be described by the same broken power law with a break at ∼3 × 10‑5 independent of host type for hosts below 1 M ⊙. These findings indicate that the planet-to-star mass ratio is a more fundamental quantity in planet formation than planet mass. We then compare our results to those from microlensing for which the overwhelming majority satisfies the M host < 1 M ⊙ criterion. The break in q for the microlensing planet population, which mostly probes the region outside the snowline, is ∼3–10 times higher than that inferred from Kepler. Thus, the most common planet inside the snowline is ∼3–10 times less massive than the one outside. With rocky planets interior to gaseous planets, the solar system broadly follows the combined mass-ratio function inferred from Kepler and microlensing. However, the exoplanet population has a less extreme radial distribution of planetary masses than the solar system. Establishing whether the mass-ratio function beyond the snowline is also host type independent will be crucial to build a comprehensive theory of planet formation.

Parasitism alters three power laws of scaling in a metazoan community: Taylor’s law, density-mass allometry, and variance-mass allometry

PubMed Central

Lagrue, Clément; Poulin, Robert; Cohen, Joel E.

2015-01-01

How do the lifestyles (free-living unparasitized, free-living parasitized, and parasitic) of animal species affect major ecological power-law relationships? We investigated this question in metazoan communities in lakes of Otago, New Zealand. In 13,752 samples comprising 1,037,058 organisms, we found that species of different lifestyles differed in taxonomic distribution and body mass and were well described by three power laws: a spatial Taylor’s law (the spatial variance in population density was a power-law function of the spatial mean population density); density-mass allometry (the spatial mean population density was a power-law function of mean body mass); and variance-mass allometry (the spatial variance in population density was a power-law function of mean body mass). To our knowledge, this constitutes the first empirical confirmation of variance-mass allometry for any animal community. We found that the parameter values of all three relationships differed for species with different lifestyles in the same communities. Taylor's law and density-mass allometry accurately predicted the form and parameter values of variance-mass allometry. We conclude that species of different lifestyles in these metazoan communities obeyed the same major ecological power-law relationships but did so with parameters specific to each lifestyle, probably reflecting differences among lifestyles in population dynamics and spatial distribution. PMID:25550506

Parasitism alters three power laws of scaling in a metazoan community: Taylor's law, density-mass allometry, and variance-mass allometry.

PubMed

Lagrue, Clément; Poulin, Robert; Cohen, Joel E

2015-02-10

How do the lifestyles (free-living unparasitized, free-living parasitized, and parasitic) of animal species affect major ecological power-law relationships? We investigated this question in metazoan communities in lakes of Otago, New Zealand. In 13,752 samples comprising 1,037,058 organisms, we found that species of different lifestyles differed in taxonomic distribution and body mass and were well described by three power laws: a spatial Taylor's law (the spatial variance in population density was a power-law function of the spatial mean population density); density-mass allometry (the spatial mean population density was a power-law function of mean body mass); and variance-mass allometry (the spatial variance in population density was a power-law function of mean body mass). To our knowledge, this constitutes the first empirical confirmation of variance-mass allometry for any animal community. We found that the parameter values of all three relationships differed for species with different lifestyles in the same communities. Taylor's law and density-mass allometry accurately predicted the form and parameter values of variance-mass allometry. We conclude that species of different lifestyles in these metazoan communities obeyed the same major ecological power-law relationships but did so with parameters specific to each lifestyle, probably reflecting differences among lifestyles in population dynamics and spatial distribution.

GAMA/H-ATLAS: The Local Dust Mass Function and Cosmic Density as a Function of Galaxy Type - A Benchmark for Models of Galaxy Evolution

NASA Astrophysics Data System (ADS)

Beeston, R. A.; Wright, A. H.; Maddox, S.; Gomez, H. L.; Dunne, L.; Driver, S. P.; Robotham, A.; Clark, C. J. R.; Vinsen, K.; Takeuchi, T. T.; Popping, G.; Bourne, N.; Bremer, M. N.; Phillipps, S.; Moffett, A. J.; Baes, M.; Bland-Hawthorn, J.; Brough, S.; De Vis, P.; Eales, S. A.; Holwerda, B. W.; Loveday, J.; Liske, J.; Smith, M. W. L.; Smith, D. J. B.; Valiante, E.; Vlahakis, C.; Wang, L.

2018-06-01

We present the dust mass function (DMF) of 15,750 galaxies with redshift z < 0.1, drawn from the overlapping area of the GAMA and H-ATLAS surveys. The DMF is derived using the density corrected Vmax method, where we estimate Vmax using: (i) the normal photometric selection limit (pVmax) and (ii) a bivariate brightness distribution (BBD) technique, which accounts for two selection effects. We fit the data with a Schechter function, and find M^{*}=(4.65 ± 0.18)× 107 h^2_{70} M_{⊙ }, α = ( - 1.22 ± 0.01), φ ^{*}=(6.26 ± 0.28)× 10^{-3} h^3_{70} Mpc^{-3} dex^{-1}. The resulting dust mass density parameter integrated down to 104 M⊙ is Ωd = (1.11 ± 0.02) × 10-6 which implies the mass fraction of baryons in dust is f_{m_b}=(2.40± 0.04)× 10^{-5}; cosmic variance adds an extra 7-17 per cent uncertainty to the quoted statistical errors. Our measurements have fewer galaxies with high dust mass than predicted by semi-analytic models. This is because the models include too much dust in high stellar mass galaxies. Conversely, our measurements find more galaxies with high dust mass than predicted by hydrodynamical cosmological simulations. This is likely to be from the long timescales for grain growth assumed in the models. We calculate DMFs split by galaxy type and find dust mass densities of Ωd = (0.88 ± 0.03) × 10-6 and Ωd = (0.060 ± 0.005) × 10-6 for late-types and early-types respectively. Comparing to the equivalent galaxy stellar mass functions (GSMF) we find that the DMF for late-types is well matched by the GMSF scaled by (8.07 ± 0.35) × 10-4.

Muscle mass, structural and functional investigations of senescence-accelerated mouse P8 (SAMP8)

PubMed Central

Guo, An Yun; Leung, Kwok Sui; Siu, Parco Ming Fai; Qin, Jiang Hui; Chow, Simon Kwoon Ho; Qin, Ling; Li, Chi Yu; Cheung, Wing Hoi

2015-01-01

Sarcopenia is an age-related systemic syndrome with progressive deterioration in skeletal muscle functions and loss in mass. Although the senescence-accelerated mouse P8 (SAMP8) was reported valid for muscular ageing research, there was no report on the details such as sarcopenia onset time. Therefore, this study was to investigate the change of muscle mass, structure and functions during the development of sarcopenia. Besides the average life span, muscle mass, structural and functional measurements were also studied. Male SAMP8 animals were examined at month 6, 7, 8, 9, and 10, in which the right gastrocnemius was isolated and tested for ex vivo contractile properties and fatigability while the contralateral one was harvested for muscle fiber cross-sectional area (FCSA) and typing assessments. Results showed that the peak of muscle mass appeared at month 7 and the onset of contractility decline was observed from month 8. Compared with month 8, most of the functional parameters at month 10 decreased significantly. Structurally, muscle fiber type IIA made up the largest proportion of the gastrocnemius, and the fiber size was found to peak at month 8. Based on the altered muscle mass, structural and functional outcomes, it was concluded that the onset of sarcopenia in SAMP8 animals was at month 8. SAMP8 animals at month 8 should be at pre-sarcopenia stage while month 10 at sarcopenia stage. It is confirmed that SAMP8 mouse can be used in sarcopenia research with established time line in this study. PMID:26193895

Increased left ventricular mass and diastolic dysfunction are associated with endothelial dysfunction in normotensive offspring of subjects with essential hypertension.

PubMed

Zizek, Bogomir; Poredos, Pavel

2007-01-01

We aimed to investigate left ventricular (LV) morphology and function in normotensive offspring of subjects with essential hypertension (familial trait - FT), and to determine the association between LV mass and determinants of LV diastolic function and endothelium-dependent (NO-mediated) dilation of the brachial artery (BA). The study encompassed 76 volunteers of whom 44 were normotonics with FT aged 28-39 (mean 33) years and 32 age-matched controls without FT. LV mass and LV diastolic function was measured using conventional echocardiography and tissue Doppler imaging (TDI). LV diastolic filling properties were assessed and reported as the peak E/A wave ratio, and peak septal annular velocities (E(m) and E(m)/A(m) ratio) on TDI. Using high-resolution ultrasound, BA diameters at rest and during reactive hyperaemia (flow-mediated dilation--FMD) were measured. In subjects with FT, the LV mass index was higher than in controls (92.14+/-24.02 vs 70.08+/-20.58); p<0.001). Offspring of hypertensive families had worse LV diastolic function than control subjects (lower E/A ratio, lower E(m) and E(m)/A(m) ratio; p<0.001). In subjects with FT, FMD was decreased compared with the controls (6.11+/-3.28% vs 10.20+/-2.07%; p<0.001). LV mass index and E(m)/A(m) ratio were associated with FMD (p<0.001). In normotensive individuals with FT, LV morphological and functional changes were found. We demonstrated that an increase in LV mass and alterations in LV diastolic function are related to endothelial dysfunction.

The Limits of Functional Analysis in the Study of Mass Communication.

ERIC Educational Resources Information Center

Anderson, James A.; Meyer, Timothy P.

The fundamental limits of the functional approach to the study of mass communication are embodied in two of its criticisms. The first weakness is in its logical structure and the second involves the limits that are set by known methods. Functional analysis has difficulties as a meaningful research perspective because the process of mass…

The young star cluster population of M51 with LEGUS - II. Testing environmental dependences

NASA Astrophysics Data System (ADS)

Messa, Matteo; Adamo, A.; Calzetti, D.; Reina-Campos, M.; Colombo, D.; Schinnerer, E.; Chandar, R.; Dale, D. A.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Elmegreen, B. G.; Fumagalli, M.; Johnson, K. E.; Kruijssen, J. M. D.; Östlin, G.; Shabani, F.; Smith, L. J.; Whitmore, B. C.

2018-06-01

It has recently been established that the properties of young star clusters (YSCs) can vary as a function of the galactic environment in which they are found. We use the cluster catalogue produced by the Legacy Extragalactic UV Survey (LEGUS) collaboration to investigate cluster properties in the spiral galaxy M51. We analyse the cluster population as a function of galactocentric distance and in arm and inter-arm regions. The cluster mass function exhibits a similar shape at all radial bins, described by a power law with a slope close to -2 and an exponential truncation around 105 M⊙. While the mass functions of the YSCs in the spiral arm and inter-arm regions have similar truncation masses, the inter-arm region mass function has a significantly steeper slope than the one in the arm region, a trend that is also observed in the giant molecular cloud mass function and predicted by simulations. The age distribution of clusters is dependent on the region considered, and is consistent with rapid disruption only in dense regions, while little disruption is observed at large galactocentric distances and in the inter-arm region. The fraction of stars forming in clusters does not show radial variations, despite the drop in the H2 surface density measured as a function of galactocentric distance. We suggest that the higher disruption rate observed in the inner part of the galaxy is likely at the origin of the observed flat cluster formation efficiency radial profile.

Dynamical Formation Signatures of Black Hole Binaries in the First Detected Mergers by LIGO

NASA Astrophysics Data System (ADS)

O'Leary, Ryan M.; Meiron, Yohai; Kocsis, Bence

2016-06-01

The dynamical formation of stellar-mass black hole-black hole binaries has long been a promising source of gravitational waves for the Laser Interferometer Gravitational-Wave Observatory (LIGO). Mass segregation, gravitational focusing, and multibody dynamical interactions naturally increase the interaction rate between the most massive black holes in dense stellar systems, eventually leading them to merge. We find that dynamical interactions, particularly three-body binary formation, enhance the merger rate of black hole binaries with total mass M tot roughly as \\propto {M}{{tot}}β , with β ≳ 4. We find that this relation holds mostly independently of the initial mass function, but the exact value depends on the degree of mass segregation. The detection rate of such massive black hole binaries is only further enhanced by LIGO’s greater sensitivity to massive black hole binaries with M tot ≲ 80 {M}⊙ . We find that for power-law BH mass functions dN/dM ∝ M -α with α ≤ 2, LIGO is most likely to detect black hole binaries with a mass twice that of the maximum initial black hole mass and a mass ratio near one. Repeated mergers of black holes inside the cluster result in about ˜5% of mergers being observed between two and three times the maximum initial black hole mass. Using these relations, one may be able to invert the observed distribution to the initial mass function with multiple detections of merging black hole binaries.

ARE SOME MILKY WAY GLOBULAR CLUSTERS HOSTED BY UNDISCOVERED GALAXIES?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaritsky, Dennis; Crnojević, Denija; Sand, David J., E-mail: dennis.zaritsky@gmail.com

2016-07-20

The confirmation of a globular cluster (GC) in the recently discovered ultrafaint galaxy Eridanus II (Eri II) motivated us to examine the question posed in the title. After estimating the halo mass of Eri II using a published stellar mass—halo mass relation, the one GC in this galaxy supports extending the relationship between the number of GCs hosted by a galaxy and the galaxy’s total mass about two orders of magnitude in stellar mass below the previous limit. For this empirically determined specific frequency of between 0.06 and 0.39 GCs per 10{sup 9} M {sub ⊙} of total mass, themore » surviving Milky Way (MW) subhalos with masses smaller than 10{sup 10} M {sub ⊙} could host as many as 5–31 GCs, broadly consistent with the actual population of outer halo MW GCs, although matching the radial distribution in detail remains a challenge. Using a subhalo mass function from published high-resolution numerical simulations and a Poissonian model for populating those halos with the aforementioned empirically constrained frequency, we find that about 90% of these GCs lie in lower-mass subhalos than that of Eri II. From what we know about the stellar mass–halo mass function, the subhalo mass function, and the mass-normalized GC specific frequency, we conclude that some of the MW’s outer halo GCs are likely to be hosted by undetected subhalos with extremely modest stellar populations.« less

Black Hole and Galaxy Coevolution from Continuity Equation and Abundance Matching

NASA Astrophysics Data System (ADS)

Aversa, R.; Lapi, A.; de Zotti, G.; Shankar, F.; Danese, L.

2015-09-01

We investigate the coevolution of galaxies and hosted supermassive black holes (BHs) throughout the history of the universe by a statistical approach based on the continuity equation and the abundance matching technique. Specifically, we present analytical solutions of the continuity equation without source terms to reconstruct the supermassive BH mass function from the active galactic nucleus (AGN) luminosity functions. Such an approach includes physically motivated AGN light curves tested on independent data sets, which describe the evolution of the Eddington ratio and radiative efficiency from slim- to thin-disk conditions. We nicely reproduce the local estimates of the BH mass function, the AGN duty cycle as a function of mass and redshift, along with the Eddington ratio function and the fraction of galaxies with given stellar mass hosting an AGN with given Eddington ratio. We exploit the same approach to reconstruct the observed stellar mass function at different redshift from the ultraviolet and far-IR luminosity functions associated with star formation in galaxies. These results imply that the build-up of stars and BHs in galaxies occurs via in situ processes, with dry mergers playing a marginal role at least for stellar masses ≲ 3× {10}11 {M}⊙ and BH masses ≲ {10}9 {M}⊙ , where the statistical data are more secure and less biased by systematic errors. In addition, we develop an improved abundance matching technique to link the stellar and BH content of galaxies to the gravitationally dominant dark matter (DM) component. The resulting relationships constitute a testbed for galaxy evolution models, highlighting the complementary role of stellar and AGN feedback in the star formation process. In addition, they may be operationally implemented in numerical simulations to populate DM halos or to gauge subgrid physics. Moreover, they may be exploited to investigate the galaxy/AGN clustering as a function of redshift, mass, and/or luminosity. In fact, the clustering properties of BHs and galaxies are found to be in full agreement with current observations, thus further validating our results from the continuity equation. Finally, our analysis highlights that (i) the fraction of AGNs observed in the slim-disk regime, where most of the BH mass is accreted, increases with redshift; and (ii) already at z≳ 6 a substantial amount of dust must have formed over timescales ≲ {10}8 yr in strongly star-forming galaxies, making these sources well within the reach of ALMA surveys in (sub)millimeter bands.

BINARY FORMATION MECHANISMS: CONSTRAINTS FROM THE COMPANION MASS RATIO DISTRIBUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reggiani, Maddalena M.; Meyer, Michael R., E-mail: reggiani@phys.ethz.ch

2011-09-01

We present a statistical comparison of the mass ratio distribution of companions, as observed in different multiplicity surveys, to the most recent estimate of the single-object mass function. The main goal of our analysis is to test whether or not the observed companion mass ratio distribution (CMRD) as a function of primary star mass and star formation environment is consistent with having been drawn from the field star initial mass function (IMF). We consider samples of companions for M dwarfs, solar-type stars, and intermediate-mass stars, both in the field as well as clusters or associations, and compare them with populationsmore » of binaries generated by random pairing from the assumed IMF for a fixed primary mass. With regard to the field we can reject the hypothesis that the CMRD was drawn from the IMF for different primary mass ranges: the observed CMRDs show a larger number of equal-mass systems than predicted by the IMF. This is in agreement with fragmentation theories of binary formation. For the open clusters {alpha} Persei and the Pleiades we also reject the IMF random-pairing hypothesis. Concerning young star-forming regions, currently we can rule out a connection between the CMRD and the field IMF in Taurus but not in Chamaeleon I. Larger and different samples are needed to better constrain the result as a function of the environment. We also consider other companion mass functions and we compare them with observations. Moreover the CMRD both in the field and clusters or associations appears to be independent of separation in the range covered by the observations. Combining therefore the CMRDs of M (1-2400 AU) and G (28-1590 AU) primaries in the field and intermediate-mass primary binaries in Sco OB2 (29-1612 AU) for mass ratios, q = M{sub 2}/M{sub 1}, from 0.2 to 1, we find that the best chi-square fit follows a power law dN/dq{proportional_to}q {sup {beta}}, with {beta} = -0.50 {+-} 0.29, consistent with previous results. Finally, we note that the Kolmogorov-Smirnov test gives a {approx}1% probability of the observed CMRD in the Pleiades and Taurus being consistent with that observed for solar-type primaries in the field over comparable primary mass range. This highlights the value of using CMRDs to understand which star formation events contribute most to the field.« less

The Panchromatic Hubble Andromeda Treasury. IV. A Probabilistic Approach to Inferring the High-mass Stellar Initial Mass Function and Other Power-law Functions

NASA Astrophysics Data System (ADS)

Weisz, Daniel R.; Fouesneau, Morgan; Hogg, David W.; Rix, Hans-Walter; Dolphin, Andrew E.; Dalcanton, Julianne J.; Foreman-Mackey, Daniel T.; Lang, Dustin; Johnson, L. Clifton; Beerman, Lori C.; Bell, Eric F.; Gordon, Karl D.; Gouliermis, Dimitrios; Kalirai, Jason S.; Skillman, Evan D.; Williams, Benjamin F.

2013-01-01

We present a probabilistic approach for inferring the parameters of the present-day power-law stellar mass function (MF) of a resolved young star cluster. This technique (1) fully exploits the information content of a given data set; (2) can account for observational uncertainties in a straightforward way; (3) assigns meaningful uncertainties to the inferred parameters; (4) avoids the pitfalls associated with binning data; and (5) can be applied to virtually any resolved young cluster, laying the groundwork for a systematic study of the high-mass stellar MF (M >~ 1 M ⊙). Using simulated clusters and Markov Chain Monte Carlo sampling of the probability distribution functions, we show that estimates of the MF slope, α, are unbiased and that the uncertainty, Δα, depends primarily on the number of observed stars and on the range of stellar masses they span, assuming that the uncertainties on individual masses and the completeness are both well characterized. Using idealized mock data, we compute the theoretical precision, i.e., lower limits, on α, and provide an analytic approximation for Δα as a function of the observed number of stars and mass range. Comparison with literature studies shows that ~3/4 of quoted uncertainties are smaller than the theoretical lower limit. By correcting these uncertainties to the theoretical lower limits, we find that the literature studies yield langαrang = 2.46, with a 1σ dispersion of 0.35 dex. We verify that it is impossible for a power-law MF to obtain meaningful constraints on the upper mass limit of the initial mass function, beyond the lower bound of the most massive star actually observed. We show that avoiding substantial biases in the MF slope requires (1) including the MF as a prior when deriving individual stellar mass estimates, (2) modeling the uncertainties in the individual stellar masses, and (3) fully characterizing and then explicitly modeling the completeness for stars of a given mass. The precision on MF slope recovery in this paper are lower limits, as we do not explicitly consider all possible sources of uncertainty, including dynamical effects (e.g., mass segregation), unresolved binaries, and non-coeval populations. We briefly discuss how each of these effects can be incorporated into extensions of the present framework. Finally, we emphasize that the technique and lessons learned are applicable to more general problems involving power-law fitting. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

A massive Feynman integral and some reduction relations for Appell functions

NASA Astrophysics Data System (ADS)

Shpot, M. A.

2007-12-01

New explicit expressions are derived for the one-loop two-point Feynman integral with arbitrary external momentum and masses m12 and m22 in D dimensions. The results are given in terms of Appell functions, manifestly symmetric with respect to the masses mi2. Equating our expressions with previously known results in terms of Gauss hypergeometric functions yields reduction relations for the involved Appell functions that are apparently new mathematical results.

Epidemiology of Sarcopenia: Determinants Throughout the Lifecourse

PubMed Central

Shaw, SC; Denison, EM; Cooper, C

2017-01-01

Sarcopenia is an age-related syndrome characterised by progressive and generalised loss of skeletal muscle mass and strength; it is a major contributor to the risk of physical frailty, functional impairment in older people, poor health-related quality of life, and premature death. Many different definitions have been used to describe sarcopenia and have resulted in varying estimates of prevalence of the condition. The most recent attempts of definitions have tried to integrate information on muscle mass, strength and physical function and provide a definition that is useful in both research and clinical settings. This review focuses on the epidemiology of the three distinct physiological components of sarcopenia, and highlights the similarities and differences between their patterns of variation with age, gender, geography and time; and the individual risk factors that cluster selectively with muscle mass, strength and physical function. Methods used to measure muscle mass, strength and physical functioning and how differences in these approaches can contribute to the varying prevalence rates will also be described. The evidence for this review was gathered by undertaking a systematic search of the literature. The descriptive characteristics of muscle mass, strength and function described in this review point to the urgent need for a consensual definition of sarcopenia incorporating these parameters. PMID:28469267

Illustrating the Basic Functioning of Mass Analyzers in Mass Spectrometers with Ball-Rolling Mechanisms

ERIC Educational Resources Information Center

Horikoshi, Ryo; Takeiri, Fumitaka; Mikita, Riho; Kobayashi, Yoji; Kageyama, Hiroshi

2017-01-01

A unique demonstration with ball-rolling mechanisms has been developed to illustrate the basic principles of mass analyzers as components of mass spectrometers. Three ball-rolling mechanisms mimicking the currently used mass analyzers (i.e., a quadrupole mass filter, a magnetic sector, and a time-of- flight) have been constructed. Each mechanism…

THE ARECIBO LEGACY FAST ALFA SURVEY. IX. THE LEO REGION H I CATALOG, GROUP MEMBERSHIP, AND THE H I MASS FUNCTION FOR THE LEO I GROUP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stierwalt, Sabrina; Haynes, Martha P.; Giovanelli, Riccardo

We present the catalog of H I sources extracted from the ongoing Arecibo Legacy Fast ALFA (ALFALFA) extragalactic H I line survey, found within the sky region bounded by 9{sup h}36{sup m} < {alpha} < 11{sup h}36{sup m} and +08{sup 0} < {delta} < +12{sup 0}. The H I catalog presented here for this 118 deg{sup 2} region is combined with the ones derived from surrounding regions also covered by the ALFALFA survey to examine the large-scale structure in the complex Leo region. Because of the combination of wide sky coverage and superior sensitivity, spatial and spectral resolution, the ALFALFAmore » H I catalog of the Leo region improves significantly on the numbers of low H I mass sources as compared with those found in previous H I surveys. The H I mass function of the Leo I group presented here is dominated by low-mass objects: 45 of the 65 Leo I members have M{sub H{sub l}}<10{sup 8} M-odot, yielding tight constraints on the low-mass slope of the Leo I H I mass function. The best-fit slope is {alpha} {approx_equal} -1.41 + 0.2 - 0.1. A direct comparison between the ALFALFA H I line detections and an optical search of the Leo I region proves the advantage of the ALFALFA strategy in finding low-mass, gas-rich dwarfs. These results suggest the existence of a significant population of low surface brightness, gas-rich, yet still very low H I mass galaxies, and may reflect the same type of morphological segregation as is seen in the Local Group. While the low-mass end slope of the Leo I H I mass function is steeper than that determined for luminosity functions of the group, the slope still falls short of the values predicted by simulations of structure formation in the lambda cold dark matter paradigm.« less

Eddington's demon: inferring galaxy mass functions and other distributions from uncertain data

NASA Astrophysics Data System (ADS)

Obreschkow, D.; Murray, S. G.; Robotham, A. S. G.; Westmeier, T.

2018-03-01

We present a general modified maximum likelihood (MML) method for inferring generative distribution functions from uncertain and biased data. The MML estimator is identical to, but easier and many orders of magnitude faster to compute than the solution of the exact Bayesian hierarchical modelling of all measurement errors. As a key application, this method can accurately recover the mass function (MF) of galaxies, while simultaneously dealing with observational uncertainties (Eddington bias), complex selection functions and unknown cosmic large-scale structure. The MML method is free of binning and natively accounts for small number statistics and non-detections. Its fast implementation in the R-package dftools is equally applicable to other objects, such as haloes, groups, and clusters, as well as observables other than mass. The formalism readily extends to multidimensional distribution functions, e.g. a Choloniewski function for the galaxy mass-angular momentum distribution, also handled by dftools. The code provides uncertainties and covariances for the fitted model parameters and approximate Bayesian evidences. We use numerous mock surveys to illustrate and test the MML method, as well as to emphasize the necessity of accounting for observational uncertainties in MFs of modern galaxy surveys.

FRAGMENTATION AND EVOLUTION OF MOLECULAR CLOUDS. II. THE EFFECT OF DUST HEATING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, Andrea; Evans, Neal J.; Martel, Hugo

2010-02-20

We investigate the effect of heating by luminosity sources in a simulation of clustered star formation. Our heating method involves a simplified continuum radiative transfer method that calculates the dust temperature. The gas temperature is set by the dust temperature. We present the results of four simulations; two simulations assume an isothermal equation of state and the two other simulations include dust heating. We investigate two mass regimes, i.e., 84 M{sub sun} and 671 M{sub sun}, using these two different energetics algorithms. The mass functions for the isothermal simulations and simulations that include dust heating are drastically different. In themore » isothermal simulation, we do not form any objects with masses above 1 M{sub sun}. However, the simulation with dust heating, while missing some of the low-mass objects, forms high-mass objects ({approx}20 M{sub sun}) which have a distribution similar to the Salpeter initial mass function. The envelope density profiles around the stars formed in our simulation match observed values around isolated, low-mass star-forming cores. We find the accretion rates to be highly variable and, on average, increasing with final stellar mass. By including radiative feedback from stars in a cluster-scale simulation, we have determined that it is a very important effect which drastically affects the mass function and yields important insights into the formation of massive stars.« less

Light interception in species with different functional groups coexisting in moorland plant communities.

PubMed

Kamiyama, Chiho; Oikawa, Shimpei; Kubo, Takuya; Hikosaka, Kouki

2010-11-01

Competition for light is one of the most essential mechanisms affecting species composition. It has been suggested that similar light acquisition efficiency (Φ(mass), absorbed photon flux per unit aboveground mass) may contribute to species coexistence in multi-species communities. On the other hand, it is known that traits related with light acquisition vary among functional groups. We studied whether Φ(mass) was similar among species with different functional groups coexisting in moorland communities. We conducted stratified clipping in midsummer when the stand biomass reached a maximum. Light partitioning among species was estimated using a model accounting for both direct and diffuse light. Evergreen species were found to have a significantly lower Φ(mass) than deciduous species, which resulted from their lower absorbed photon flux per unit leaf area and lower specific leaf area. Shrubs had a smaller leaf mass fraction, but their Φ(mass) was not lower than that of herbs because they had a higher leaf position due to the presence of wintering stems. Species with vertical leaves had a higher Φ(mass) than those with horizontal leaves despite vertical leaves being a decided disadvantage in terms of light absorption. This higher Φ(mass) was achieved by a greater leaf height in species with vertical leaves. Our results clearly demonstrate that light acquisition efficiency was different among the functional groups. However, the trend observed is not necessarily the same as that expected based on prior knowledge, suggesting that disadvantages in some traits for light acquisition efficiency are partly compensated for by other traits.

The Copernicus Complexio: a high-resolution view of the small-scale Universe

NASA Astrophysics Data System (ADS)

Hellwing, Wojciech A.; Frenk, Carlos S.; Cautun, Marius; Bose, Sownak; Helly, John; Jenkins, Adrian; Sawala, Till; Cytowski, Maciej

2016-04-01

We introduce Copernicus Complexio (COCO), a high-resolution cosmological N-body simulation of structure formation in the ΛCDM model. COCO follows an approximately spherical region of radius ˜17.4 h-1 Mpc embedded in a much larger periodic cube that is followed at lower resolution. The high-resolution volume has a particle mass of 1.135 × 105 h-1 M⊙ (60 times higher than the Millennium-II simulation). COCO gives the dark matter halo mass function over eight orders of magnitude in halo mass; it forms ˜60 haloes of galactic size, each resolved with about 10 million particles. We confirm the power-law character of the subhalo mass function, overline{N}(>μ )∝ μ ^{-s}, down to a reduced subhalo mass Msub/M200 ≡ μ = 10-6, with a best-fitting power-law index, s = 0.94, for hosts of mass = 1012 h-1 M⊙. The concentration-mass relation of COCO haloes deviates from a single power law for masses M200 < afew × 108 h-1 M⊙, where it flattens, in agreement with results by Sanchez-Conde et al. The host mass invariance of the reduced maximum circular velocity function of subhaloes, ν ≡ Vmax/V200, hinted at in previous simulations, is clearly demonstrated over five orders of magnitude in host mass. Similarly, we find that the average, normalized radial distribution of subhaloes is approximately universal (I.e. independent of subhalo mass), as previously suggested by the Aquarius simulations of individual haloes. Finally, we find that at fixed physical subhalo size, subhaloes in lower mass hosts typically have lower central densities than those in higher mass hosts.

Hyperaccretion during tidal disruption events: weakly bound debris envelopes and jets

NASA Astrophysics Data System (ADS)

Coughlin, Eric; Begelman, M. C.

2014-01-01

After the destruction of the star during a tidal disruption event (TDE), the cataclysmic encounter between a star and the supermassive black hole (SMBH) of a galaxy, approximately half of the original stellar debris falls back onto the hole at a rate that can initially exceed the Eddington limit by orders of magnitude. We argue that the angular momentum of this matter is too low to allow it to attain a disk-like configuration with accretion proceeding at a mildly super-Eddington rate, the excess energy being carried away by a combination of radiative losses and radially distributed winds. Instead, we propose that the in-falling gas traps accretion energy until it inflates into a weakly-bound, quasi-spherical structure with gas extending nearly to the poles. We study the structure and evolution of such “Zero-Bernoulli accretion” flows (ZEBRAs) as a model for the super- Eddington phase of TDEs. We argue that such flows cannot stop extremely super-Eddington accretion from occurring, and that once the envelope is maximally inflated, any excess accretion energy escapes through the poles in the form of powerful jets. Similar models, including self-gravity, could be applicable to gamma-ray bursts from collapsars and the growth of supermassive black hole seeds inside quasi-stars.

Disc origin of broad optical emission lines of the TDE candidate PTF09djl

NASA Astrophysics Data System (ADS)

Liu, F. K.; Zhou, Z. Q.; Cao, R.; Ho, L. C.; Komossa, S.

2017-11-01

An otherwise dormant supermassive black hole (SMBH) in a galactic nucleus flares up when it tidally disrupts a star passing by. Most of the tidal disruption events (TDEs) and candidates discovered in the optical/UV have broad optical emission lines with complex and diverse profiles of puzzling origin. In this Letter, we show that the double-peaked broad H α line of the TDE candidate PTF09djl can be well modelled with a relativistic elliptical accretion disc and the peculiar substructures with one peak at the line rest wavelength and the other redshifted to about 3.5 × 104 km s-1 are mainly due to the orbital motion of the emitting matter within the disc plane of large inclination 88° and pericentre orientation nearly vertical to the observer. The accretion disc has an extreme eccentricity 0.966 and semimajor axis of 340 BH Schwarzschild radii. The viewing angle effects of large disc inclination lead to significant attenuation of He emission lines originally produced at large electron scattering optical depth and to the absence/weakness of He emission lines in the spectra of PTF09djl. Our results suggest that the diversities of line intensity ratios among the line species in optical TDEs are probably due to the differences of disc inclinations.

An X-ray survey of the Central Molecular Zone: variability of the Fe K emission line

NASA Astrophysics Data System (ADS)

Terrier, R.; Clavel, M.

2017-10-01

The observation of varying non-thermal diffuse X-ray emission molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the Galactic SMBH. Determining its light curve over the past centuries requires a detailed knowledge of the gas distribution, which is still lacking. Nevertheless, variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe K line, can bring strong constraints. Thanks to a deep scan of the inner 300 pc with XMM in 2012 and to a similar albeit more shallow scan performed in 2000-2001, we performed a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 years) events.

Mid-ir Properties Of Seyferts: Spitzer/irs Spectroscopy Of The Iras 12µM Seyfert Sample

NASA Astrophysics Data System (ADS)

Wu, Yanling; Charmandaris, V.; Huang, J.

2009-05-01

The study of Seyfert galaxies is of particular interest as they trace the build up of SMBH at the centers of galaxies and they are responsible for the most of the cosmic X-ray background at redshift z 0.8. Given the high obscuration of their nuclei by dust extinction, a large fraction of their emitted radiation is absorbed and reemitted in the infrared. It has been recently demonstrated that mid-infrared spectroscopy, in particular with ISO and Spitzer, is a powerful tool to probe the physics of the radiation field of deeply enshrouded galactic nuclei. Here we present our analysis on the properties of Seyfert galaxies based mostly on our uniformly extracted low-resolution Spitzer/IRS 5.5-35micron spectra for 103 Seyfert galaxies, nearly 90% of the local 12 µm IRAS Seyfert sample. We find that we are able to disentangle the AGN/starburst contribution of the mid-IR emission, and estimate the circumnuclear star formation rate using typical mid-IR tracers. We also find that the mid-IR properties of Type 1 and Type 2 Seyferts are indistinguishable at a given luminosiry range, placing constrains both on the infrared optical depth to their nuclei galaxies as well as to the applicability of the unified AGN model.

Dual Active Galactic Nuclei in Nearby Galaxies

NASA Astrophysics Data System (ADS)

Das, Mousumi; Rubinur, Khatun; Karb, Preeti; Varghese, Ashlin; Novakkuni, Navyasree; James, Atul

2018-04-01

Galaxy mergers play a crucial role in the formation of massive galaxies and the buildup of their bulges. An important aspect of the merging process is the in-spiral of the supermassive black-holes (SMBHs) to the centre of the merger remnant and the eventual formation of a SMBH binary. If both the SMBHs are accreting they will form a dual or binary active galactic nucleus (DAGN). The final merger remnant is usually very bright and shows enhanced star formation. In this paper we summarise the current sample of DAGN from previous studies and describe methods that can be used to identify strong DAGN candidates from optical and spectroscopic surveys. These methods depend on the Doppler separation of the double peaked AGN emission lines, the nuclear velocity dispersion of the galaxies and their optical/UV colours. We describe two high resolution, radio observations of DAGN candidates that have been selected based on their double peaked optical emission lines (DPAGN). We also examine whether DAGN host galaxies have higher star formation rates (SFRs) compared to merging galaxies that do not appear to have DAGN. We find that the SFR is not higher for DAGN host galaxies. This suggests that the SFRs in DAGN host galaxies is due to the merging process itself and not related to the presence of two AGN in the system.

An expanded set of brown dwarf and very low mass star models

NASA Technical Reports Server (NTRS)

Burrows, A.; Hubbard, W. B.; Saumon, D.; Lunine, J. I.

1993-01-01

We present in this paper updated and improved theoretical models of brown dwarfs and late M dwarfs. The evolution and characteristics of objects between 0.01 and 0.2 solar mass are exhaustively investigated and special emphasis is placed on their properties at early ages. The dependence on the helium fraction, deuterium fraction, and metallicity of the masses, effective temperature and luminosities at the edge of the hydrogen main sequence are calculated. We derive luminosity functions for representative mass functions and compare our predictions to recent cluster data. We show that there are distinctive features in the theoretical luminosity functions that can serve as diagnostics of brown dwarf physics. A zero-metallicity model is presented as a bound to or approximation of a putative extreme halo population.

Improved Tandem Measurement Techniques for Aerosol Particle Analysis

NASA Astrophysics Data System (ADS)

Rawat, Vivek Kumar

Non-spherical, chemically inhomogeneous (complex) nanoparticles are encountered in a number of natural and engineered environments, including combustion systems (which produces highly non-spherical aggregates), reactors used in gas-phase materials synthesis of doped or multicomponent materials, and in ambient air. These nanoparticles are often highly diverse in size, composition and shape, and hence require determination of property distribution functions for accurate characterization. This thesis focuses on development of tandem mobility-mass measurement techniques coupled with appropriate data inversion routines to facilitate measurement of two dimensional size-mass distribution functions while correcting for the non-idealities of the instruments. Chapter 1 provides the detailed background and motivation for the studies performed in this thesis. In chapter 2, the development of an inversion routine is described which is employed to determine two dimensional size-mass distribution functions from Differential Mobility Analyzer-Aerosol Particle Mass analyzer tandem measurements. Chapter 3 demonstrates the application of the two dimensional distribution function to compute cumulative mass distribution function and also evaluates the validity of this technique by comparing the calculated total mass concentrations to measured values for a variety of aerosols. In Chapter 4, this tandem measurement technique with the inversion routine is employed to analyze colloidal suspensions. Chapter 5 focuses on application of a transverse modulation ion mobility spectrometer coupled with a mass spectrometer to study the effect of vapor dopants on the mobility shifts of sub 2 nm peptide ion clusters. These mobility shifts are then compared to models based on vapor uptake theories. Finally, in Chapter 6, a conclusion of all the studies performed in this thesis is provided and future avenues of research are discussed.

Do muscle mass, muscle density, strength, and physical function similarly influence risk of hospitalization in older adults?

PubMed

Cawthon, Peggy Mannen; Fox, Kathleen M; Gandra, Shravanthi R; Delmonico, Matthew J; Chiou, Chiun-Fang; Anthony, Mary S; Sewall, Ase; Goodpaster, Bret; Satterfield, Suzanne; Cummings, Steven R; Harris, Tamara B

2009-08-01

To examine the association between strength, function, lean mass, muscle density, and risk of hospitalization. Prospective cohort study. Two U.S. clinical centers. Adults aged 70 to 80 (N=3,011) from the Health, Aging and Body Composition Study. Measurements were of grip strength, knee extension strength, lean mass, walking speed, and chair stand pace. Thigh computed tomography scans assessed muscle area and density (a proxy for muscle fat infiltration). Hospitalizations were confirmed by local review of medical records. Negative binomial regression models estimated incident rate ratios (IRRs) of hospitalization for race- and sex-specific quartiles of each muscle and function parameter separately. Multivariate models adjusted for age, body mass index, health status, and coexisting medical conditions. During an average 4.7 years of follow-up, 1,678 (55.7%) participants experienced one or more hospitalizations. Participants in the lowest quartile of muscle density were more likely to be subsequently hospitalized (multivariate IRR=1.47, 95% confidence interval (CI)=1.24-1.73) than those in the highest quartile. Similarly, participants with the weakest grip strength were at greater risk of hospitalization (multivariate IRR=1.52, 95% CI=1.30-1.78, Q1 vs. Q4). Comparable results were seen for knee strength, walking pace, and chair stands pace. Lean mass and muscle area were not associated with risk of hospitalization. Weak strength, poor function, and low muscle density, but not muscle size or lean mass, were associated with greater risk of hospitalization. Interventions to reduce the disease burden associated with sarcopenia should focus on increasing muscle strength and improving physical function rather than simply increasing lean mass.

Body mass index in ambulatory cerebral palsy patients.

PubMed

Feeley, Brian T; Gollapudi, Kiran; Otsuka, Norman Y

2007-05-01

Malnutrition is a common problem in children with cerebral palsy. Although malnutrition is often recognized in patients with severe cerebral palsy, it can be unrecognized in less severely affected patients. The consequences of malnutrition are serious, and include decreased muscle strength, poor immune status, and depressed cerebral functioning. Low body mass index has been used as a marker for malnutrition. The purpose of this study was to determine which patients in an ambulatory cerebral palsy patient population were at risk for low body mass index. A retrospective chart review was performed on 75 patients. Age, sex, height, weight, type of cerebral palsy, and functional status [gross motor functional classification system (GMFCS) level] was recorded from the chart. Descriptive statistics with bivariate and multivariate regression analyses were performed. Thirty-eight boys and 37 girls with an average age of 8.11 years were included in the study. Unique to our patient population, all cerebral palsy patients were independent ambulators. Patients with quadriplegic cerebral palsy had a significantly lower body mass index than those with diplegic and hemiplegic cerebral palsy. Patients with a GMFCS III had significantly lower body mass index than those with GMFCS I and II. When multivariate regression analysis to control for age and sex was performed, low body mass index remained associated with quadriplegic cerebral palsy and GMFCS III. Malnutrition is a common health problem in patients with cerebral palsy, leading to significant morbidity in multiple organ systems. We found that in an ambulatory cerebral palsy population, patients with lower functional status or quadriplegia had significantly lower body mass index, suggesting that even highly functioning ambulatory cerebral palsy patients are at risk for malnutrition.

The effects of dance music jump rope exercise on pulmonary function and body mass index after music jump rope exercise in overweight adults in 20's.

PubMed

Seo, KyoChul

2017-08-01

[Purpose] The purpose of this study was to examine the effect of a dance music jump rope exercise on changes Pulmonary Function and body mass index in female overweight subjects in their 20's. [Subjects and Methods] The subjects were randomly assigned to the dance music jump rope exercise group and the stationary cycle exercise group. All subjects have conducted the exercises three times a week for four weeks. Pulmonary function was evaluated using a spirometer, and body mass index was evaluated using an InBody 3.0. [Results] The findings of this study showed significant improvements in the voluntary capacity and body mass index of the experimental groups. Vital capacity was higher in the music jump rope exercise group than the stationary cycle exercise group, and body mass index was lower in the music jump rope exercise group than the stationary cycle exercise group. [Conclusion] This study showed that the dance music jump rope exercise can be used to improve vital capacity and body mass index.

Polymeric 3D Printed Functional Microcantilevers for Biosensing Applications.

PubMed

Stassi, Stefano; Fantino, Erika; Calmo, Roberta; Chiappone, Annalisa; Gillono, Matteo; Scaiola, Davide; Pirri, Candido Fabrizio; Ricciardi, Carlo; Chiadò, Alessandro; Roppolo, Ignazio

2017-06-07

In this study, we show for the first time the production of mass-sensitive polymeric biosensors by 3D printing technology with intrinsic functionalities. We also demonstrate the feasibility of mass-sensitive biosensors in the form of microcantilever in a one-step printing process, using acrylic acid as functional comonomer for introducing a controlled amount of functional groups that can covalently immobilize the biomolecules onto the polymer. The effectiveness of the application of 3D printed microcantilevers as biosensors is then demonstrated with their implementation in a standard immunoassay protocol. This study shows how 3D microfabrication techniques, material characterization, and biosensor development could be combined to obtain an engineered polymeric microcantilever with intrinsic functionalities. The possibility of tuning the composition of the starting photocurable resin with the addition of functional agents, and consequently controlling the functionalities of the 3D printed devices, paves the way to a new class of mass-sensing microelectromechanical system devices with intrinsic properties.

Planetary mass function and planetary systems

NASA Astrophysics Data System (ADS)

Dominik, M.

2011-02-01

With planets orbiting stars, a planetary mass function should not be seen as a low-mass extension of the stellar mass function, but a proper formalism needs to take care of the fact that the statistical properties of planet populations are linked to the properties of their respective host stars. This can be accounted for by describing planet populations by means of a differential planetary mass-radius-orbit function, which together with the fraction of stars with given properties that are orbited by planets and the stellar mass function allows the derivation of all statistics for any considered sample. These fundamental functions provide a framework for comparing statistics that result from different observing techniques and campaigns which all have their very specific selection procedures and detection efficiencies. Moreover, recent results both from gravitational microlensing campaigns and radial-velocity surveys of stars indicate that planets tend to cluster in systems rather than being the lonely child of their respective parent star. While planetary multiplicity in an observed system becomes obvious with the detection of several planets, its quantitative assessment however comes with the challenge to exclude the presence of further planets. Current exoplanet samples begin to give us first hints at the population statistics, whereas pictures of planet parameter space in its full complexity call for samples that are 2-4 orders of magnitude larger. In order to derive meaningful statistics, however, planet detection campaigns need to be designed in such a way that well-defined fully deterministic target selection, monitoring and detection criteria are applied. The probabilistic nature of gravitational microlensing makes this technique an illustrative example of all the encountered challenges and uncertainties.

Correlation between T2* cardiovascular magnetic resonance with left ventricular function and mass in adolescent and adult major thalassemia patients with iron overload.

PubMed

Djer, Mulyadi M; Anggriawan, Shirley L; Gatot, Djajadiman; Amalia, Pustika; Sastroasmoro, Sudigdo; Widjaja, Patricia

2013-10-01

to assess for a correlation between T2*CMR with LV function and mass in thalassemic patients with iron overload. a cross-sectional study on thalassemic patients was conducted between July and September 2010 at Cipto Mangunkusumo and Premier Hospitals, Jakarta, Indonesia. Clinical examinations, review of medical charts, electrocardiography, echocardiography, and T2*CMR were performed. Cardiac siderosis was measured by T2*CMR conduction time. Left ventricle diastolic and systolic functions, as well as LV mass index were measured using echocardiography. Correlations between T2*CMR and echocardiography findings, as well as serum ferritin were determined using Pearson's and Spearman's tests. thirty patients aged 13-41 years were enrolled, of whom two-thirds had -thalassemia major and one-third had HbE/-thalassemia. Diastolic dysfunction was identified in 8 patients, whereas systolic function was normal in all patients. Increased LV mass index was found in 3 patients. T2*CMR conduction times ranged from 8.98 to 55.04 ms and a value below 20 ms was demonstrated in 14 patients. There was a statistically significant moderate positive correlation of T2*CMR conduction time with E/A ratio (r = 0.471, P = 0.009), but no correlation was found with LV mass index (r=0.097, P=0.608). A moderate negative correlation was found between T2*CMR and serum ferritin (r = -0.514, P = 0.004), while a moderate negative correlation was found between serum ferritin and E/A ratio (r = -0.425, P = 0.019). T2*CMR myocardial conduction time has a moderate positive correlation with diastolic function, moderate negative correlation with serum ferritin, but not with LV mass index and systolic function.

Time Evolution of the Giant Molecular Cloud Mass Functions across Galactic Disks

NASA Astrophysics Data System (ADS)

Kobayashi, Masato I. N.; Inutsuka, Shu-Ichiro; Kobayashi, Hiroshi; Hasegawa, Kenji

2017-01-01

We formulate and conduct the time-integration of time evolution equation for the giant molecular cloud mass function (GMCMF) including the cloud-cloud collision (CCC) effect. Our results show that the CCC effect is only limited in the massive-end of the GMCMF and indicate that future high resolution and sensitivity radio observations may constrain giant molecular cloud (GMC) timescales by observing the GMCMF slope in the lower mass regime.

Effect of gender specific anthropometric characteristics on lung function in young competitive triathletes from Malaysia.

PubMed

Johari, Hanapi M; Zainudin, Hakimi A; Knight, Victor F; Lumley, Steven A; Subramanium, Ananthan S; Caszo, Brinnell A; Gnanou, Justin V

2017-04-01

Anthropometric and lung function characteristics of triathletes are important for the implementation of individual specific training and recovery recommendations. However, limited data are available for these parameters in triathletes. Hence, the aim of this study was to characterize and examine the gender differences of lung function and anthropometry parameters in competitive triathletes from Malaysia. Body composition assessment and lung function tests were performed on sixteen competitive triathletes (nine male and seven female). The subject's body composition profile including muscle mass (kg), fat free mass (kg), and percent body fat was measured using a bio-impedance segmental body composition analyzer. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were measured by Quark PFT2 spirometer. The anthropometric measurements revealed that male triathletes were significantly taller than female triathletes and had significantly more protein and skeletal muscle mass. The female triathletes, however, had significantly higher percent body fat. Male triathletes had statistically significant higher FVC and FEV1 than female triathletes. Both the male and female triathletes showed a positive correlation between height, fat free mass and the lung function markers FVC and FEV1. This association was not seen with Body Mass Index (BMI) in female triathletes. The data from our study shows that anthropometric parameters are directly linked to lung function of a triathlete. We also found the relationship between BMI and lung function to be gender specific in triathletes and is dependent on the body protein and fat content. Hence, body composition characterization is essential and provides valuable information for developing individual specific training modules.

Relationship between dynapenia and cardiorespiratory functions in healthy postmenopausal women: novel clinical criteria.

PubMed

Barbat-Artigas, Seébastien; Dupontgand, Sophie; Fex, Annie; Karelis, Antony D; Aubertin-Leheudre, Mylène

2011-04-01

Muscle strength seems to be a better indicator of physical limitations than skeletal muscle mass is. The purpose of this study was to investigate, using a new developed clinical tool, the relationship between type I dynapenia and cardiorespiratory functions in postmenopausal women. Forty-six postmenopausal women were recruited and divided into two groups (dynapenic vs nondynapenic). Body composition (bioelectrical impedancemetry), muscle strength (dynamometer), cardiorespiratory functions (maximum oxygen consumption and forced expiratory volume in 1 second), resting energy expenditure (indirect calorimetry), and dietary intake (3-d dietary journal) were measured. Type I dynapenia was defined as less than 1.53 kg per skeletal muscle mass (kg) based on handgrip dynamometer. Significant differences were found between dynapenic (n=23) and nondynapenic (n=23) postmenopausal women for cardiorespiratory functions (maximum oxygen consumption, P=0.003; and forced expiratory volume in 1 second, P=0.046). We observed no differences between groups for age, age at menopause, use of hormone therapy, body mass index, waist circumference, fat mass, resting energy expenditure, and total energy intake, which are known to be potential confounders. No differences were observed for cardiorespiratory functions when our population was divided into sarcopenic and nonsarcopenic groups. Type I dynapenic women have significantly poorer cardiorespiratory functions that do nondynapenic women even if they presented the same skeletal muscle mass index. Thus, based on our results, dynapenia could potentially be used as a marker of cardiorespiratory functions. The clinical method developed to identify dynapenic women could be used by health professionals. © 2011 by The North American Menopause Society

Effective vortex mass from microscopic theory

NASA Astrophysics Data System (ADS)

Han, Jung Hoon; Kim, June Seo; Kim, Min Jae; Ao, Ping

2005-03-01

We calculate the effective mass of a single quantized vortex in the Bardeen-Cooper-Schrieffer superconductor at finite temperature. Based on effective action approach, we arrive at the effective mass of a vortex as integral of the spectral function J(ω) divided by ω3 over frequency. The spectral function is given in terms of the quantum-mechanical transition elements of the gradient of the Hamiltonian between two Bogoliubov-deGennes (BdG) eigenstates. Based on self-consistent numerical diagonalization of the BdG equation we find that the effective mass per unit length of vortex at zero temperature is of order m(kfξ0)2 ( kf=Fermi momentum, ξ0=coherence length), essentially equaling the electron mass displaced within the coherence length from the vortex core. Transitions between the core states are responsible for most of the mass. The mass reaches a maximum value at T≈0.5Tc and decreases continuously to zero at Tc .

Effects of mass on aircraft sidearm controller characteristics

NASA Technical Reports Server (NTRS)

Wagner, Charles A.

1994-01-01

When designing a flight simulator, providing a set of low mass variable-characteristic pilot controls can be very difficult. Thus, a strong incentive exists to identify the highest possible mass that will not degrade the validity of a simulation. The NASA Dryden Flight Research Center has conducted a brief flight program to determine the maximum acceptable mass (system inertia) of an aircraft sidearm controller as a function of force gradient. This information is useful for control system design in aircraft as well as development of suitable flight simulator controls. A modified Learjet with a variable-characteristic sidearm controller was used to obtain data. A boundary was defined between mass considered acceptable and mass considered unacceptable to the pilot. This boundary is defined as a function of force gradient over a range of natural frequencies. This investigation is limited to a study of mass-frequency characteristics only. Results of this investigation are presented in this paper.

Excited-State Effective Masses in Lattice QCD

DOE Office of Scientific and Technical Information (OSTI.GOV)

George Fleming, Saul Cohen, Huey-Wen Lin

2009-10-01

We apply black-box methods, i.e. where the performance of the method does not depend upon initial guesses, to extract excited-state energies from Euclidean-time hadron correlation functions. In particular, we extend the widely used effective-mass method to incorporate multiple correlation functions and produce effective mass estimates for multiple excited states. In general, these excited-state effective masses will be determined by finding the roots of some polynomial. We demonstrate the method using sample lattice data to determine excited-state energies of the nucleon and compare the results to other energy-level finding techniques.

Stellar populations dominated by massive stars in dusty starburst galaxies across cosmic time

NASA Astrophysics Data System (ADS)

Zhang, Zhi-Yu; Romano, D.; Ivison, R. J.; Papadopoulos, Padelis P.; Matteucci, F.

2018-06-01

All measurements of cosmic star formation must assume an initial distribution of stellar masses—the stellar initial mass function—in order to extrapolate from the star-formation rate measured for typically rare, massive stars (of more than eight solar masses) to the total star-formation rate across the full stellar mass spectrum1. The shape of the stellar initial mass function in various galaxy populations underpins our understanding of the formation and evolution of galaxies across cosmic time2. Classical determinations of the stellar initial mass function in local galaxies are traditionally made at ultraviolet, optical and near-infrared wavelengths, which cannot be probed in dust-obscured galaxies2,3, especially distant starbursts, whose apparent star-formation rates are hundreds to thousands of times higher than in the Milky Way, selected at submillimetre (rest-frame far-infrared) wavelengths4,5. The 13C/18O isotope abundance ratio in the cold molecular gas—which can be probed via the rotational transitions of the 13CO and C18O isotopologues—is a very sensitive index of the stellar initial mass function, with its determination immune to the pernicious effects of dust. Here we report observations of 13CO and C18O emission for a sample of four dust-enshrouded starbursts at redshifts of approximately two to three, and find unambiguous evidence for a top-heavy stellar initial mass function in all of them. A low 13CO/C18O ratio for all our targets—alongside a well tested, detailed chemical evolution model benchmarked on the Milky Way6—implies that there are considerably more massive stars in starburst events than in ordinary star-forming spiral galaxies. This can bring these extraordinary starbursts closer to the `main sequence' of star-forming galaxies7, although such main-sequence galaxies may not be immune to changes in initial stellar mass function, depending on their star-formation densities.

ASSESSMENT OF ANALYTICAL METHODS USED TO MEASURE CHANGES IN BODY COMPOSITION IN THE ELDERLY AND RECOMMENDATIONS FOR THEIR USE IN PHASE II CLINICAL TRIALS

PubMed Central

Lustgarten, M.S.; Fielding, R.A.

2012-01-01

It is estimated that in the next 20 years, the amount of people greater than 65 years of age will rise from 40 to 70 million, and will account for 19% of the total population. Age-related decreases in muscle mass and function, known as sarcopenia, have been shown to be related to functional limitation, frailty and an increased risk of morbidity and mortality. Therefore, with an increasing elderly population, interventions that can improve muscle mass content and/or function are essential. However, analytical techniques used for measurement of muscle mass in young subjects may not be valid for use in the elderly. Therefore, the purpose of this review is to examine the applied specificity and accuracy of methods that are commonly used for measurement of muscle mass in aged subjects, and, to propose specific recommendations for the use of body composition measures in phase II clinical trials of function-promoting anabolic therapies. PMID:21528163

Association of sarcopenia with functional decline in community-dwelling elderly subjects in Japan.

PubMed

Tanimoto, Yoshimi; Watanabe, Misuzu; Sun, Wei; Tanimoto, Keiji; Shishikura, Kanako; Sugiura, Yumiko; Kusabiraki, Toshiyuki; Kono, Koichi

2013-10-01

The present study aimed to determine the association of sarcopenia, defined by muscle mass, muscle strength and physical performance, with functional disability from a 2-year cohort study of community-dwelling elderly Japanese people. Participants were 743 community-dwelling elderly Japanese people aged 65 years or older. We used bioelectrical impedance analysis (BIA) to measure muscle mass, grip strength to measure muscle strength, and usual walking speed to measure physical performance in a baseline study. Functional disability was defined using an activities of daily living (ADL) scale and instrumental activities of daily living (IADL) scale at baseline and during follow-up examinations 2 years later. Logistic regression analysis, adjusted for age and body mass index, was used to examine the association between sarcopenia and the occurrence of functional disability. In the present study, 7.8% of men and 10.2% of women were classified as having sarcopenia. Among sarcopenia patients in the baseline study, 36.8% of men and 18.8% of women became dependent in ADL at 2-year follow up. From the logistic regression analysis adjusted by age and body mass index, sarcopenia was significantly associated with the occurrences of physical disability compared with normal subjects in both men and women. Sarcopenia, defined by muscle mass, muscle strength and physical performance, was associated with functional decline over a 2-year period in elderly Japanese. Interventions to prevent sarcopenia are very important to prevent functional decline among elderly individuals. © 2013 Japan Geriatrics Society.

The mysterious age invariance of the planetary nebula luminosity function bright cut-off

NASA Astrophysics Data System (ADS)

Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M.

2018-05-01

Planetary nebulae mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models1,2 predicted that only stars above approximately twice the solar mass could form a bright nebula. But the ubiquitous presence of bright planetary nebulae in old stellar populations, such as elliptical galaxies, contradicts this: such high-mass stars are not present in old systems. The planetary nebula luminosity function, and especially its bright cut-off, is almost invariant between young spiral galaxies, with high-mass stars, and old elliptical galaxies, with only low-mass stars. Here, we show that new evolutionary tracks of low-mass stars are capable of explaining in a simple manner this decades-old mystery. The agreement between the observed luminosity function and computed stellar evolution validates the latest theoretical modelling. With these models, the planetary nebula luminosity function provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a planetary nebula, but it will be faint.

Formation of massive, dense cores by cloud-cloud collisions

NASA Astrophysics Data System (ADS)

Takahira, Ken; Shima, Kazuhiro; Habe, Asao; Tasker, Elizabeth J.

2018-03-01

We performed sub-parsec (˜ 0.014 pc) scale simulations of cloud-cloud collisions of two idealized turbulent molecular clouds (MCs) with different masses in the range of (0.76-2.67) × 104 M_{⊙} and with collision speeds of 5-30 km s-1. Those parameters are larger than in Takahira, Tasker, and Habe (2014, ApJ, 792, 63), in which study the colliding system showed a partial gaseous arc morphology that supports the NANTEN observations of objects indicated to be colliding MCs using numerical simulations. Gas clumps with density greater than 10-20 g cm-3 were identified as pre-stellar cores and tracked through the simulation to investigate the effects of the mass of colliding clouds and the collision speeds on the resulting core population. Our results demonstrate that the smaller cloud property is more important for the results of cloud-cloud collisions. The mass function of formed cores can be approximated by a power-law relation with an index γ = -1.6 in slower cloud-cloud collisions (v ˜ 5 km s-1), and is in good agreement with observation of MCs. A faster relative speed increases the number of cores formed in the early stage of collisions and shortens the gas accretion phase of cores in the shocked region, leading to the suppression of core growth. The bending point appears in the high-mass part of the core mass function and the bending point mass decreases with increase in collision speed for the same combination of colliding clouds. The higher-mass part of the core mass function than the bending point mass can be approximated by a power law with γ = -2-3 that is similar to the power index of the massive part of the observed stellar initial mass function. We discuss implications of our results for the massive-star formation in our Galaxy.

Formation of massive, dense cores by cloud-cloud collisions

NASA Astrophysics Data System (ADS)

Takahira, Ken; Shima, Kazuhiro; Habe, Asao; Tasker, Elizabeth J.

2018-05-01

We performed sub-parsec (˜ 0.014 pc) scale simulations of cloud-cloud collisions of two idealized turbulent molecular clouds (MCs) with different masses in the range of (0.76-2.67) × 104 M_{⊙} and with collision speeds of 5-30 km s-1. Those parameters are larger than in Takahira, Tasker, and Habe (2014, ApJ, 792, 63), in which study the colliding system showed a partial gaseous arc morphology that supports the NANTEN observations of objects indicated to be colliding MCs using numerical simulations. Gas clumps with density greater than 10-20 g cm-3 were identified as pre-stellar cores and tracked through the simulation to investigate the effects of the mass of colliding clouds and the collision speeds on the resulting core population. Our results demonstrate that the smaller cloud property is more important for the results of cloud-cloud collisions. The mass function of formed cores can be approximated by a power-law relation with an index γ = -1.6 in slower cloud-cloud collisions (v ˜ 5 km s-1), and is in good agreement with observation of MCs. A faster relative speed increases the number of cores formed in the early stage of collisions and shortens the gas accretion phase of cores in the shocked region, leading to the suppression of core growth. The bending point appears in the high-mass part of the core mass function and the bending point mass decreases with increase in collision speed for the same combination of colliding clouds. The higher-mass part of the core mass function than the bending point mass can be approximated by a power law with γ = -2-3 that is similar to the power index of the massive part of the observed stellar initial mass function. We discuss implications of our results for the massive-star formation in our Galaxy.

Sleep, Muscle Mass and Muscle Function in Older People.

PubMed

Buchmann, Nikolaus; Spira, Dominik; Norman, Kristina; Demuth, Ilja; Eckardt, Rahel; Steinhagen-Thiessen, Elisabeth

2016-04-15

Loss of muscle mass, particularly in old age, can restrict mobility and physical function. Sleep is thought to play a key role in the maintenance of muscle mass; sleep disturbances have a prevalence of 6-30% in Germany. In this study, based on data from the Berlin Aging Study II (BASE-II), we analyze the relationship between sleep efficiency and quality on the one hand, and muscle mass and muscle function on the other. We analyzed cross-sectional data from 1196 subjects (52.5% women; 68 ± 4 years). Sleep behavior was assessed with questions from the Pittsburgh Sleep Quality Index; appendicular lean mass (ALM) with dual x-ray absorp - tiometry; and muscle function with a measure of grip strength and with questionnaires about physical activity and impairment of physical activities. Low muscle mass was determined from the ALM corrected by the body-mass index (BMI), i.e., from the ratio ALM/BMI. 19.1% of the women and 13.4% of the men reported poor sleep quality. Men whose ALM/BMI ratio was below the cutoff value for low muscle mass more frequently reported very poor sleep efficiency (9.1% , versus 4.8% in women; p<0.002). The adjusted odds ratio for low muscle mass was 2.8 for men with poor sleep quality (95% confidence interval: [1.1; 6.7]) and 4.3 for men with poor sleep efficiency [1.2; 15.1]. In women, there was no statistically significant association between sleep quality and efficiency on the one hand and ALM/BMI values below cutoff on the other, but poor sleep quality was found to be associated with reduced grip strength (16.25 kg ± 2.33 kg versus 15.67 kg ± 2.38 kg; p = 0.009) and low appendicular lean mass (ALM: 16.25 kg ± 2.33 kg versus 15.67 kg ± 2.38 kg; p = 0.016). These findings support the hypothesis of a link between sleep and muscle mass. The dependence of muscle mass on sleep behavior needs to be investigated in longitudinal studies.

THE ARECIBO LEGACY FAST ALFA SURVEY. X. THE H I MASS FUNCTION AND {Omega}{sub H{sub i}} FROM THE 40% ALFALFA SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Ann M.; Papastergis, Emmanouil; Giovanelli, Riccardo

The Arecibo Legacy Fast ALFA (ALFALFA) survey has completed source extraction for 40% of its total sky area, resulting in the largest sample of H I-selected galaxies to date. We measure the H I mass function from a sample of 10,119 galaxies with 6.2 < log (M{sub H{sub i}}/M{sub sun}) < 11.0 and with well-described mass errors that accurately reflect our knowledge of low-mass systems. We characterize the survey sensitivity and its dependence on profile velocity width, the effect of large-scale structure, and the impact of radio frequency interference in order to calculate the H I mass function with bothmore » the 1/V{sub max} and 2DSWML methods. We also assess a flux-limited sample to test the robustness of the methods applied to the full sample. These measurements are in excellent agreement with one another; the derived Schechter function parameters are {phi}{sub *} (h {sup 3}{sub 70} Mpc{sup -3} dex{sup -1}) = 4.8 {+-} 0.3 x 10{sup -3}, log (M{sub *}/M{sub sun}) + 2 log h{sub 70} = 9.96 {+-} 0.02, and {alpha} = -1.33 {+-} 0.02. We find {Omega}{sub H{sub i}}= 4.3 {+-} 0.3 x10{sup -4} h {sup -1}{sub 70}, 16% larger than the 2005 HIPASS result, and our Schechter function fit extrapolated to log (M{sub H{sub i}}/M{sub sun}) = 11.0 predicts an order of magnitude more galaxies than HIPASS. The larger values of {Omega}{sub H{sub i}} and of M{sub *} imply an upward adjustment for estimates of the detection rate of future large-scale H I line surveys with, e.g., the Square Kilometer Array. A comparison with simulated galaxies from the Millennium Run and a treatment of photoheating as a method of baryon removal from H I-selected halos indicate that the disagreement between dark matter mass functions and baryonic mass functions may soon be resolved.« less

Detection of masses in mammogram images using CNN, geostatistic functions and SVM.

PubMed

Sampaio, Wener Borges; Diniz, Edgar Moraes; Silva, Aristófanes Corrêa; de Paiva, Anselmo Cardoso; Gattass, Marcelo

2011-08-01

Breast cancer occurs with high frequency among the world's population and its effects impact the patients' perception of their own sexuality and their very personal image. This work presents a computational methodology that helps specialists detect breast masses in mammogram images. The first stage of the methodology aims to improve the mammogram image. This stage consists in removing objects outside the breast, reducing noise and highlighting the internal structures of the breast. Next, cellular neural networks are used to segment the regions that might contain masses. These regions have their shapes analyzed through shape descriptors (eccentricity, circularity, density, circular disproportion and circular density) and their textures analyzed through geostatistic functions (Ripley's K function and Moran's and Geary's indexes). Support vector machines are used to classify the candidate regions as masses or non-masses, with sensitivity of 80%, rates of 0.84 false positives per image and 0.2 false negatives per image, and an area under the ROC curve of 0.87. Copyright © 2011 Elsevier Ltd. All rights reserved.

Evaporation of planetary atmospheres due to XUV illumination by quasars

NASA Astrophysics Data System (ADS)

Forbes, John C.; Loeb, Abraham

2018-06-01

Planetary atmospheres are subject to mass loss through a variety of mechanisms including irradiation by XUV photons from their host star. Here we explore the consequences of XUV irradiation by supermassive black holes as they grow by the accretion of gas in galactic nuclei. Based on the mass distribution of stars in galactic bulges and disks and the luminosity history of individual black holes, we estimate the probability distribution function of XUV fluences as a function of galaxy halo mass, redshift, and stellar component. We find that about 50% of all planets in the universe may lose a mass of hydrogen of ˜2.5 × 1019 g (the total mass of the Martian atmosphere), 10% may lose ˜5.1 × 1021 g (the total mass of Earth's atmosphere), and 0.2% may lose ˜1.4 × 1024 g (the total mass of Earth's oceans). The fractions are appreciably higher in the spheroidal components of galaxies, and depend strongly on galaxy mass, but only weakly on redshift.

The VIMOS Public Extragalactic Redshift Survey (VIPERS). Environmental effects shaping the galaxy stellar mass function

NASA Astrophysics Data System (ADS)

Davidzon, I.; Cucciati, O.; Bolzonella, M.; De Lucia, G.; Zamorani, G.; Arnouts, S.; Moutard, T.; Ilbert, O.; Garilli, B.; Scodeggio, M.; Guzzo, L.; Abbas, U.; Adami, C.; Bel, J.; Bottini, D.; Branchini, E.; Cappi, A.; Coupon, J.; de la Torre, S.; Di Porto, C.; Fritz, A.; Franzetti, P.; Fumana, M.; Granett, B. R.; Guennou, L.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; McCracken, H. J.; Mellier, Y.; Moscardini, L.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.

2016-02-01

We exploit the first public data release of VIPERS to investigate environmental effects in the evolution of galaxies between z ~ 0.5 and 0.9. The large number of spectroscopic redshifts (more than 50 000) over an area of about 10 deg2 provides a galaxy sample with high statistical power. The accurate redshift measurements (σz = 0.00047(1 + zspec)) allow us to robustly isolate galaxies living in the lowest and highest density environments (δ< 0.7 and δ> 4, respectively) as defined in terms of spatial 3D density contrast δ. We estimate the stellar mass function of galaxies residing in these two environments and constrain the high-mass end (ℳ ≳ 1011 ℳ⊙) with unprecedented precision. We find that the galaxy stellar mass function in the densest regions has a different shape than was measured at low densities, with an enhancement of massive galaxies and a hint of a flatter (less negative) slope at z< 0.8. We normalise each mass function to the comoving volume occupied by the corresponding environment and relate estimates from different redshift bins. We observe an evolution of the stellar mass function of VIPERS galaxies in high densities, while the low-density one is nearly constant. We compare these results to semi-analytical models and find consistent environmental signatures in the simulated stellar mass functions. We discuss how the halo mass function and fraction of central/satellite galaxies depend on the environments considered, making intrinsic and environmental properties of galaxies physically coupled, hence difficult to disentangle. The evolution of our low-density regions is described well by the formalism introduced by Peng et al. (2010, ApJ, 721, 193), and is consistent with the idea that galaxies become progressively passive because of internal physical processes. The same formalism could also describe the evolution of the mass function in the high density regions, but only if a significant contribution from dry mergers is considered. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programmes 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.

The Mass Function of Young Star Clusters in the "Antennae" Galaxies.

PubMed

Zhang; Fall

1999-12-20

We determine the mass function of young star clusters in the merging galaxies known as the "Antennae" (NGC 4038/9) from deep images taken with the Wide Field Planetary Camera 2 on the refurbished Hubble Space Telescope. This is accomplished by means of reddening-free parameters and a comparison with stellar population synthesis tracks to estimate the intrinsic luminosity and age, and hence the mass, of each cluster. We find that the mass function of the young star clusters (with ages less, similar160 Myr) is well represented by a power law of the form psi&parl0;M&parr0;~M-2 over the range 104 less, similarM less, similar106 M middle dot in circle. This result may have important implications for our understanding of the origin of globular clusters during the early phases of galactic evolution.

Functional Requirements for the Next Generation of Mass Notification

ERIC Educational Resources Information Center

Trumbo, Berkly

2012-01-01

While the latest update to National Fire Protection Association (NFPA) redefines mass notification as "emergency communications systems" (ECS), the end user community is formulating expectations related to the future functionality of today's alerting solutions. Numerous best practices have surfaced since alerting technology began its rapid,…

Mass Estimation and Its Applications

DTIC Science & Technology

2012-02-23

parameters); e.g., the rect- angular kernel function has fixed width or fixed per unit size. But the rectangular function used in mass has no parameter...MassTER is implemented in JAVA , and we use DBSCAN in WEKA [13] and a version of DENCLUE implemented in R (www.r-project.org) in our empirical evaluation...Proceedings of SIGKDD, 2010, 989-998. [13] I.H. Witten and E. Frank, Data Mining: Practical Machine Learning Tools and Techniques with Java Implementations

Slowly-rotating neutron stars in massive bigravity

NASA Astrophysics Data System (ADS)

Sullivan, A.; Yunes, N.

2018-02-01

We study slowly-rotating neutron stars in ghost-free massive bigravity. This theory modifies general relativity by introducing a second, auxiliary but dynamical tensor field that couples to matter through the physical metric tensor through non-linear interactions. We expand the field equations to linear order in slow rotation and numerically construct solutions in the interior and exterior of the star with a set of realistic equations of state. We calculate the physical mass function with respect to observer radius and find that, unlike in general relativity, this function does not remain constant outside the star; rather, it asymptotes to a constant a distance away from the surface, whose magnitude is controlled by the ratio of gravitational constants. The Vainshtein-like radius at which the physical and auxiliary mass functions asymptote to a constant is controlled by the graviton mass scaling parameter, and outside this radius, bigravity modifications are suppressed. We also calculate the frame-dragging metric function and find that bigravity modifications are typically small in the entire range of coupling parameters explored. We finally calculate both the mass-radius and the moment of inertia-mass relations for a wide range of coupling parameters and find that both the graviton mass scaling parameter and the ratio of the gravitational constants introduce large modifications to both. These results could be used to place future constraints on bigravity with electromagnetic and gravitational-wave observations of isolated and binary neutron stars.

Relationships between cognitive function and body composition among community-dwelling older adults: a cross-sectional study.

PubMed

Noh, Hye-Mi; Oh, Sohee; Song, Hong Ji; Lee, Eun Young; Jeong, Jin-Young; Ryu, Ohk-Hyun; Hong, Kyung-Soon; Kim, Dong-Hyun

2017-11-02

Previous studies reported mixed results regarding the association between cognition and body weight in late life. We evaluated the relationships between cognitive function and body composition among community-dwelling older adults. Three hundred twenty subjects (≥65 years, women 53%) with available data of cognitive function and body composition from 2010 Hallym Aging Study. Cognitive function was assessed using Korean Mini-Mental State Examination (K-MMSE). Dual-energy X-ray absorptiometry (DEXA) was used for measuring body composition including body fat and lean body mass. Anthropometric measurements and laboratory data were collected in clinical examination. Body composition variables were divided into sex-specific tertiles, and examined by multivariable logistic regression. Among female, the highest tertile group of fat mass and second tertile group of total lean body mass were associated with lower risk for cognitive impairment compared to the respective first tertile groups (odds ratios, 0.23 and 0.09, respectively; 95% confidence intervals, 0.04-0.88 and 0.01-0.44, respectively) after adjusting for confounding factors. In male, higher arm bone mineral content was associated with lower risk for cognitive impairment, but significance was lost after adjusting for adiponectin, age, and education. Higher fat mass and lean body mass were associated with lower risk of cognitive impairment in older women. These observations suggest that body fat and lean mass later in life might be beneficial for cognition.

Skeletal muscle mass adjusted by height correlated better with muscular functions than that adjusted by body weight in defining sarcopenia.

PubMed

Han, Der-Sheng; Chang, Ke-Vin; Li, Chia-Ming; Lin, Yu-Hong; Kao, Tung-Wei; Tsai, Keh-Sung; Wang, Tyng-Grey; Yang, Wei-Shiung

2016-01-20

Sarcopenia, characterized by low muscle mass and function, results in frailty, comorbidities and mortality. However, its prevalence varies according to the different criteria used in its diagnosis. This cross-sectional study investigated the difference in the number of sarcopenia cases recorded by two different measurement methods of low muscle mass to determine which measurement was better. We recruited 878 (54.2% female) individuals aged over 65 years and obtained their body composition and functional parameters. Low muscle mass was defined as two standard deviations below either the mean height-adjusted (hSMI) or weight-adjusted (wSMI) muscle mass of a young reference group. The prevalence of sarcopenia was 6.7% vs. 0.4% (male/female) by hSMI, and 4.0% vs. 10.7% (male/female) by wSMI. The κ coefficients for these two criteria were 0.39 vs. 0.03 (male/female), and 0.17 in all subjects. Serum myostatin levels correlated positively with gait speed (r = 0.142, p = 0.007) after adjustment for gender. hSMI correlated with grip strength, cardiopulmonary endurance, leg endurance, gait speed, and flexibility. wSMI correlated with grip strength, leg endurance, gait speed, and flexibility. Since hSMI correlated more closely with grip strength and more muscular functions, we recommend hSMI in the diagnosis of low muscle mass.

Galaxy Zoo: Major Galaxy Mergers Are Not a Significant Quenching Pathway

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Caplar, Neven; Carpineti, Alfredo; Hart, Ross E.; Kaviraj, Sugata; Keel, William C.; Kruk, Sandor J.; Lintott, Chris J.; Nichol, Robert C.; Simmons, Brooke D.; Smethurst, Rebecca J.

2017-08-01

We use stellar mass functions to study the properties and the significance of quenching through major galaxy mergers. In addition to SDSS DR7 and Galaxy Zoo 1 data, we use samples of visually selected major galaxy mergers and post-merger galaxies. We determine the stellar mass functions of the stages that we would expect major-merger-quenched galaxies to pass through on their way from the blue cloud to the red sequence: (1) major merger, (2) post-merger, (3) blue early type, (4) green early type, and (5) red early type. Based on their similar mass function shapes, we conclude that major mergers are likely to form an evolutionary sequence from star formation to quiescence via quenching. Relative to all blue galaxies, the major-merger fraction increases as a function of stellar mass. Major-merger quenching is inconsistent with the mass and environment quenching model. At z˜ 0, major-merger-quenched galaxies are unlikely to constitute the majority of galaxies that transition through the green valley. Furthermore, between z˜ 0-0.5, major-merger-quenched galaxies account for 1%-5% of all quenched galaxies at a given stellar mass. Major galaxy mergers are therefore not a significant quenching pathway, neither at z˜ 0 nor within the last 5 Gyr. The majority of red galaxies must have been quenched through an alternative quenching mechanism that causes a slow blue to red evolution. .

Effect of added mass on treadmill performance and pulmonary function.

PubMed

Walker, Rachel E; Swain, David P; Ringleb, Stacie I; Colberg, Sheri R

2015-04-01

Military personnel engage in strenuous physical activity and load carriage. This study evaluated the role of body mass and of added mass on aerobic performance (uphill treadmill exercise) and pulmonary function. Performance on a traditional unloaded run test (4.8 km) was compared with performance on loaded tasks. Subjects performed an outdoor 4.8-km run and 4 maximal treadmill tests wearing loads of 0, 10, 20, and 30 kg. Subjects' pulmonary function (forced expired volume in 1 second [FEV1], forced vital capacity [FVC], and maximal voluntary ventilation [MVV]) was tested with each load, and peak values of heart rate, oxygen consumption ((Equation is included in full-text article.)), ventilation (VE), and respiratory exchange ratio (RER) were measured during each treadmill test. Performance on the 4.8-km run was correlated with treadmill performance, measured as time to exhaustion (TTE), with the strength of the correlation decreasing with load (r = 0.87 for 0 kg to 0.76 for 30 kg). Body mass was not correlated with TTE, other than among men with the 30-kg load (r = 0.48). During treadmill exercise, all peak responses other than RER decreased with load. Pulmonary function measures (FEV1, FVC, and MVV) decreased with load. Body mass was poorly correlated with treadmill performance, but added mass decreased performance. The decreased performance may be in part because of decreased pulmonary function. Unloaded 4.8-km run performance was correlated to unloaded uphill treadmill performance, but less so as load increased. Therefore, traditional run tests may not be an effective means of evaluating aerobic performance for military field operations.

Environmental dependence of the galaxy stellar mass function in the Dark Energy Survey Science Verification Data

DOE PAGES

Etherington, J.; Thomas, D.; Maraston, C.; ...

2016-01-04

Measurements of the galaxy stellar mass function are crucial to understand the formation of galaxies in the Universe. In a hierarchical clustering paradigm it is plausible that there is a connection between the properties of galaxies and their environments. Evidence for environmental trends has been established in the local Universe. The Dark Energy Survey (DES) provides large photometric datasets that enable further investigation of the assembly of mass. In this study we use ~3.2 million galaxies from the (South Pole Telescope) SPT-East field in the DES science verification (SV) dataset. From grizY photometry we derive galaxy stellar masses and absolutemore » magnitudes, and determine the errors on these properties using Monte-Carlo simulations using the full photometric redshift probability distributions. We compute galaxy environments using a fixed conical aperture for a range of scales. We construct galaxy environment probability distribution functions and investigate the dependence of the environment errors on the aperture parameters. We compute the environment components of the galaxy stellar mass function for the redshift range 0.15 < z < 1.05. For z < 0.75 we find that the fraction of massive galaxies is larger in high density environment than in low density environments. We show that the low density and high density components converge with increasing redshift up to z ~ 1.0 where the shapes of the mass function components are indistinguishable. As a result, our study shows how high density structures build up around massive galaxies through cosmic time.« less

Effective nucleon mass and the nuclear caloric curve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shetty, D. V.; Souliotis, G. A.; Galanopoulos, S.

2009-03-15

Assuming a schematic form of the nucleon effective mass as a function of nuclear excitation energy and mass, we provide a simple explanation for understanding the experimentally observed mass dependence of the nuclear caloric curve. It is observed that the excitation energy at which the caloric curve enters into a plateau region could be sensitive to the nuclear mass evolution of the effective nucleon mass.

Gravitational detection of a low-mass dark satellite galaxy at cosmological distance.

PubMed

Vegetti, S; Lagattuta, D J; McKean, J P; Auger, M W; Fassnacht, C D; Koopmans, L V E

2012-01-18

The mass function of dwarf satellite galaxies that are observed around Local Group galaxies differs substantially from simulations based on cold dark matter: the simulations predict many more dwarf galaxies than are seen. The Local Group, however, may be anomalous in this regard. A massive dark satellite in an early-type lens galaxy at a redshift of 0.222 was recently found using a method based on gravitational lensing, suggesting that the mass fraction contained in substructure could be higher than is predicted from simulations. The lack of very low-mass detections, however, prohibited any constraint on their mass function. Here we report the presence of a (1.9 ± 0.1) × 10(8) M dark satellite galaxy in the Einstein ring system JVAS B1938+666 (ref. 11) at a redshift of 0.881, where M denotes the solar mass. This satellite galaxy has a mass similar to that of the Sagittarius galaxy, which is a satellite of the Milky Way. We determine the logarithmic slope of the mass function for substructure beyond the local Universe to be 1.1(+0.6)(-0.4), with an average mass fraction of 3.3(+3.6)(-1.8) per cent, by combining data on both of these recently discovered galaxies. Our results are consistent with the predictions from cold dark matter simulations at the 95 per cent confidence level, and therefore agree with the view that galaxies formed hierarchically in a Universe composed of cold dark matter.

Luminosity and Stellar Mass Functions from the 6dF Galaxy Survey

NASA Astrophysics Data System (ADS)

Colless, M.; Jones, D. H.; Peterson, B. A.; Campbell, L.; Saunders, W.; Lah, P.

2007-12-01

The completed 6dF Galaxy Survey includes redshifts for over 124,000 galaxies. We present luminosity functions in optical and near-infrared passbands that span a range of 10^4 in luminosity. These luminosity functions show systematic deviations from the Schechter form. The corresponding luminosity densities in the optical and near-infrared are consistent with an old stellar population and a moderately declining star formation rate. Stellar mass functions, derived from the K band luminosities and simple stellar population models selected by b_J-r_F colour, lead to an estimate of the present-day stellar mass density of ρ_* = (5.00 ± 0.11) × 10^8 h M_⊙ Mpc^{-3}, corresponding to Ω_* h = (1.80 ± 0.04) × 10^{-3}.

Choice of resolution by functional trait or taxonomy affects allometric scaling in soil food webs.

PubMed

Sechi, Valentina; Brussaard, Lijbert; De Goede, Ron G M; Rutgers, Michiel; Mulder, Christian

2015-01-01

Belowground organisms often display a shift in their mass-abundance scaling relationships due to environmental factors such as soil chemistry and atmospheric deposition. Here we present new empirical data that show strong differences in allometric scaling according to whether the resolution at the local scale is based on a taxonomic or a functional classification, while only slight differences arise according to soil environmental conditions. For the first time, isometry (an inverse 1:1 proportion) is recognized in mass-abundance relationships, providing a functional signal for constant biomass distribution in soil biota regardless of discrete trophic levels. Our findings are in contrast to those from aquatic ecosystems, in that higher trophic levels in soil biota are not a direct function of increasing body mass.

Galaxy And Mass Assembly (GAMA): deconstructing bimodality - I. Red ones and blue ones

NASA Astrophysics Data System (ADS)

Taylor, Edward N.; Hopkins, Andrew M.; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brown, Michael J. I.; Colless, Matthew; Driver, Simon; Norberg, Peder; Robotham, Aaron S. G.; Alpaslan, Mehmet; Brough, Sarah; Cluver, Michelle E.; Gunawardhana, Madusha; Kelvin, Lee S.; Liske, Jochen; Conselice, Christopher J.; Croom, Scott; Foster, Caroline; Jarrett, Thomas H.; Lara-Lopez, Maritza; Loveday, Jon

2015-01-01

We measure the mass functions for generically red and blue galaxies, using a z < 0.12 sample of log M* > 8.7 field galaxies from the Galaxy And Mass Assembly (GAMA) survey. Our motivation is that, as we show, the dominant uncertainty in existing measurements stems from how `red' and `blue' galaxies have been selected/defined. Accordingly, we model our data as two naturally overlapping populations, each with their own mass function and colour-mass relation, which enables us characterize the two populations without having to specify a priori which galaxies are `red' and `blue'. Our results then provide the means to derive objective operational definitions for the terms `red' and `blue', which are based on the phenomenology of the colour-mass diagrams. Informed by this descriptive modelling, we show that (1) after accounting for dust, the stellar colours of `blue' galaxies do not depend strongly on mass; (2) the tight, flat `dead sequence' does not extend much below log M* ˜ 10.5; instead, (3) the stellar colours of `red' galaxies vary rather strongly with mass, such that lower mass `red' galaxies have bluer stellar populations; (4) below log M* ˜ 9.3, the `red' population dissolves into obscurity, and it becomes problematic to talk about two distinct populations; as a consequence, (5) it is hard to meaningfully constrain the shape, including the existence of an upturn, of the `red' galaxy mass function below log M* ˜ 9.3. Points 1-4 provide meaningful targets for models of galaxy formation and evolution to aim for.

Post-hatching development of mitochondrial function, organ mass and metabolic rate in two ectotherms, the American alligator (Alligator mississippiensis) and the common snapping turtle (Chelydra serpentina)

PubMed Central

Sirsat, Sarah K. G.; Sirsat, Tushar S.; Price, Edwin R.; Dzialowski, Edward M.

2016-01-01

ABSTRACT The ontogeny of endothermy in birds is associated with disproportionate growth of thermogenic organs and increased mitochondrial oxidative capacity. However, no similar study has been made of the development of these traits in ectotherms. For comparison, we therefore investigated the metabolism, growth and muscle mitochondrial function in hatchlings of a turtle and a crocodilian, two ectotherms that never develop endothermy. Metabolic rate did not increase substantially in either species by 30 days post-hatching. Yolk-free body mass and heart mass did not change through 30 days in alligators and heart mass was a constant proportion of body mass, even after 1 year. Yolk-free body mass and liver mass grew 36% and 27%, respectively, in turtles during the first 30 days post-hatch. The mass-specific oxidative phosphorylation capacity of mitochondria, assessed using permeabilized muscle fibers, increased by a non-significant 47% in alligator thigh and a non-significant 50% in turtle thigh over 30 days, but did not increase in the heart. This developmental trajectory of mitochondrial function is slower and shallower than that previously observed in ducks, which demonstrate a 90% increase in mass-specific oxidative phosphorylation capacity in thigh muscles over just a few days, a 60% increase in mass-specific oxidative phosphorylation capacity of the heart over a few days, and disproportionate growth of the heart and other organs. Our data thus support the hypothesis that these developmental changes in ducks represent mechanistic drivers for attaining endothermy. PMID:26962048

Galaxy and Mass Assembly (GAMA): the red fraction and radial distribution of satellite galaxies

NASA Astrophysics Data System (ADS)

Prescott, Matthew; Baldry, I. K.; James, P. A.; Bamford, S. P.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cameron, E.; Conselice, C. J.; Croom, S. M.; Driver, S. P.; Frenk, C. S.; Gunawardhana, M.; Hill, D. T.; Hopkins, A. M.; Jones, D. H.; Kelvin, L. S.; Kuijken, K.; Liske, J.; Loveday, J.; Nichol, R. C.; Norberg, P.; Parkinson, H. R.; Peacock, J. A.; Phillipps, S.; Pimbblet, K. A.; Popescu, C. C.; Robotham, A. S. G.; Sharp, R. G.; Sutherland, W. J.; Taylor, E. N.; Tuffs, R. J.; van Kampen, E.; Wijesinghe, D.

2011-10-01

We investigate the properties of satellite galaxies that surround isolated hosts within the redshift range 0.01 < z < 0.15, using data taken as part of the Galaxy And Mass Assembly survey. Making use of isolation and satellite criteria that take into account stellar mass estimates, we find 3514 isolated galaxies of which 1426 host a total of 2998 satellites. Separating the red and blue populations of satellites and hosts, using colour-mass diagrams, we investigate the radial distribution of satellite galaxies and determine how the red fraction of satellites varies as a function of satellite mass, host mass and the projected distance from their host. Comparing the red fraction of satellites to a control sample of small neighbours at greater projected radii, we show that the increase in red fraction is primarily a function of host mass. The satellite red fraction is about 0.2 higher than the control sample for hosts with ?, while the red fractions show no difference for hosts with ?. For the satellites of more massive hosts, the red fraction also increases as a function of decreasing projected distance. Our results suggest that the likely main mechanism for the quenching of star formation in satellites hosted by isolated galaxies is strangulation.

Galaxy and Mass Assembly (GAMA): galaxies at the faint end of the Hα luminosity function

NASA Astrophysics Data System (ADS)

Brough, S.; Hopkins, A. M.; Sharp, R. G.; Gunawardhana, M.; Wijesinghe, D.; Robotham, A. S. G.; Driver, S. P.; Baldry, I. K.; Bamford, S. P.; Liske, J.; Loveday, J.; Norberg, P.; Peacock, J. A.; Bland-Hawthorn, J.; Brown, M. J. I.; Cameron, E.; Croom, S. M.; Frenk, C. S.; Foster, C.; Hill, D. T.; Jones, D. H.; Kelvin, L. S.; Kuijken, K.; Nichol, R. C.; Parkinson, H. R.; Pimbblet, K.; Popescu, C. C.; Prescott, M.; Sutherland, W. J.; Taylor, E.; Thomas, D.; Tuffs, R. J.; van Kampen, E.

2011-05-01

We present an analysis of the properties of the lowest Hα-luminosity galaxies (LHα≤ 4 × 1032 W; SFR < 0.02 M⊙ yr-1, with SFR denoting the star formation rate) in the Galaxy And Mass Assembly survey. These galaxies make up the rise above a Schechter function in the number density of systems seen at the faint end of the Hα luminosity function. Above our flux limit, we find that these galaxies are principally composed of intrinsically low stellar mass systems (median stellar mass = 2.5 × 108 M⊙) with only 5/90 having stellar masses M > 1010 M⊙. The low-SFR systems are found to exist predominantly in the lowest-density environments (median density ˜0.02 galaxy Mpc-2) with none in environments more dense than ˜1.5 galaxy Mpc-2. Their current specific SFRs (SSFRs; -8.5 < log [SSFR (yr -1)] < -12) are consistent with their having had a variety of star formation histories. The low-density environments of these galaxies demonstrate that such low-mass, star-forming systems can only remain as low mass and form stars if they reside sufficiently far from other galaxies to avoid being accreted, dispersed through tidal effects or having their gas reservoirs rendered ineffective through external processes.

Evidence for top-heavy stellar initial mass functions with increasing density and decreasing metallicity

NASA Astrophysics Data System (ADS)

Marks, Michael; Kroupa, Pavel; Dabringhausen, Jörg; Pawlowski, Marcel S.

2012-05-01

Residual-gas expulsion after cluster formation has recently been shown to leave an imprint in the low-mass present-day stellar mass function (PDMF) which allowed the estimation of birth conditions of some Galactic globular clusters (GCs) such as mass, radius and star formation efficiency. We show that in order to explain their characteristics (masses, radii, metallicity and PDMF) their stellar initial mass function (IMF) must have been top heavy. It is found that the IMF is required to become more top heavy the lower the cluster metallicity and the larger the pre-GC cloud-core density are. The deduced trends are in qualitative agreement with theoretical expectation. The results are consistent with estimates of the shape of the high-mass end of the IMF in the Arches cluster, Westerlund 1, R136 and NGC 3603, as well as with the IMF independently constrained for ultra-compact dwarf galaxies (UCDs). The latter suggests that GCs and UCDs might have formed along the same channel or that UCDs formed via mergers of GCs. A Fundamental Plane is found which describes the variation of the IMF with density and metallicity of the pre-GC cloud cores. The implications for the evolution of galaxies and chemical enrichment over cosmological times are expected to be major.

Connecting massive galaxies to dark matter haloes in BOSS - I. Is galaxy colour a stochastic process in high-mass haloes?

NASA Astrophysics Data System (ADS)

Saito, Shun; Leauthaud, Alexie; Hearin, Andrew P.; Bundy, Kevin; Zentner, Andrew R.; Behroozi, Peter S.; Reid, Beth A.; Sinha, Manodeep; Coupon, Jean; Tinker, Jeremy L.; White, Martin; Schneider, Donald P.

2016-08-01

We use subhalo abundance matching (SHAM) to model the stellar mass function (SMF) and clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) `CMASS' sample at z ˜ 0.5. We introduce a novel method which accounts for the stellar mass incompleteness of CMASS as a function of redshift, and produce CMASS mock catalogues which include selection effects, reproduce the overall SMF, the projected two-point correlation function wp, the CMASS dn/dz, and are made publicly available. We study the effects of assembly bias above collapse mass in the context of `age matching' and show that these effects are markedly different compared to the ones explored by Hearin et al. at lower stellar masses. We construct two models, one in which galaxy colour is stochastic (`AbM' model) as well as a model which contains assembly bias effects (`AgM' model). By confronting the redshift dependent clustering of CMASS with the predictions from our model, we argue that that galaxy colours are not a stochastic process in high-mass haloes. Our results suggest that the colours of galaxies in high-mass haloes are determined by other halo properties besides halo peak velocity and that assembly bias effects play an important role in determining the clustering properties of this sample.

Obesity in the Kidney Transplant Process.

PubMed

Ateş, Damla; Cebeci, Fatma

2018-03-01

Obesity, which has become an increasing problem worldwide, poses a risk for kidney transplant recipients both before and after surgery. In this literature review, we studied the effects of obesity before and after kidney transplant. There are numerous studies and different opinions on the effects of obesity on graft function before and after transplant. Obesity prolongs surgery time and the ischemic process. A large cohort study of 11 836 recipients noted a close association between body mass index and delayed renal transplant and delayed graft function. However, another study found that being overweight or obese before transplant did not have any effects over the medium and long term. A 20-year follow-up study indicated that the firstyear body mass index in recipients after renal transplant had a greater effect on graft function and survival than body mass index before transplant. Still, another study found that body mass index had no effects on graft function and survival. In the study, 3-year graft function and mortality rates of morbidly obese people without diabetes, the functional status without dialysis, and living-donor transplant were reported to be much lower than in those with normal weight. In conclusion, there is no consensus on the effects of obesity before and after transplant, and it has been pointed out that more research should be done on this subject.

Failed Supernovae Explain the Compact Remnant Mass Function

NASA Astrophysics Data System (ADS)

Kochanek, C. S.

2014-04-01

One explanation for the absence of higher mass red supergiants (16.5 M ⊙ <~ M <~ 25 M ⊙) as the progenitors of Type IIP supernovae (SNe) is that they die in failed SNe creating black holes. Simulations show that such failed SNe still eject their hydrogen envelopes in a weak transient, leaving a black hole with the mass of the star's helium core (5-8 M ⊙). Here we show that this naturally explains the typical masses of observed black holes and the gap between neutron star and black hole masses without any fine-tuning of stellar mass loss, binary mass transfer, or the SN mechanism, beyond having it fail in a mass range where many progenitor models have density structures that make the explosions more likely to fail. There is no difficulty including this ~20% population of failed SNe in any accounting of SN types over the progenitor mass function. And, other than patience, there is no observational barrier to either detecting these black hole formation events or limiting their rates to be well below this prediction.

Gas-phase ion-molecule reactions for the identification of the sulfone functionality in protonated analytes in a linear quadrupole ion trap mass spectrometer.

PubMed

Tang, Weijuan; Sheng, Huaming; Kong, John Y; Yerabolu, Ravikiran; Zhu, Hanyu; Max, Joann; Zhang, Minli; Kenttämaa, Hilkka I

2016-06-30

The oxidation of sulfur atoms is an important biotransformation pathway for many sulfur-containing drugs. In order to rapidly identify the sulfone functionality in drug metabolites, a tandem mass spectrometric method based on ion-molecule reactions was developed. A phosphorus-containing reagent, trimethyl phosphite (TMP), was allowed to react with protonated analytes with various functionalities in a linear quadrupole ion trap mass spectrometer. The reaction products and reaction efficiencies were measured. Only protonated sulfone model compounds were found to react with TMP to form a characteristic [TMP adduct-MeOH] product ion. All other protonated compounds investigated, with functionalities such as sulfoxide, N-oxide, hydroxylamino, keto, carboxylic acid, and aliphatic and aromatic amino, only react with TMP via proton transfer and/or addition. The specificity of the reaction was further demonstrated by using a sulfoxide-containing anti-inflammatory drug, sulindac, as well as its metabolite sulindac sulfone. A method based on functional group-selective ion-molecule reactions in a linear quadrupole ion trap mass spectrometer has been demonstrated for the identification of the sulfone functionality in protonated analytes. A characteristic [TMP adduct-MeOH] product ion was only formed for the protonated sulfone analytes. The applicability of the TMP reagent in identifying sulfone functionalities in drug metabolites was also demonstrated. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Using PHP/MySQL to Manage Potential Mass Impacts

NASA Technical Reports Server (NTRS)

Hager, Benjamin I.

2010-01-01

This paper presents a new application using commercially available software to manage mass properties for spaceflight vehicles. PHP/MySQL(PHP: Hypertext Preprocessor and My Structured Query Language) are a web scripting language and a database language commonly used in concert with each other. They open up new opportunities to develop cutting edge mass properties tools, and in particular, tools for the management of potential mass impacts (threats and opportunities). The paper begins by providing an overview of the functions and capabilities of PHP/MySQL. The focus of this paper is on how PHP/MySQL are being used to develop an advanced "web accessible" database system for identifying and managing mass impacts on NASA's Ares I Upper Stage program, managed by the Marshall Space Flight Center. To fully describe this application, examples of the data, search functions, and views are provided to promote, not only the function, but the security, ease of use, simplicity, and eye-appeal of this new application. This paper concludes with an overview of the other potential mass properties applications and tools that could be developed using PHP/MySQL. The premise behind this paper is that PHP/MySQL are software tools that are easy to use and readily available for the development of cutting edge mass properties applications. These tools are capable of providing "real-time" searching and status of an active database, automated report generation, and other capabilities to streamline and enhance mass properties management application. By using PHP/MySQL, proven existing methods for managing mass properties can be adapted to present-day information technology to accelerate mass properties data gathering, analysis, and reporting, allowing mass property management to keep pace with today's fast-pace design and development processes.

ALMA reveals a warm and compact starburst around a heavily obscured supermassive black hole at z = 4.75

NASA Astrophysics Data System (ADS)

Gilli, R.; Norman, C.; Vignali, C.; Vanzella, E.; Calura, F.; Pozzi, F.; Massardi, M.; Mignano, A.; Casasola, V.; Daddi, E.; Elbaz, D.; Dickinson, M.; Iwasawa, K.; Maiolino, R.; Brusa, M.; Vito, F.; Fritz, J.; Feltre, A.; Cresci, G.; Mignoli, M.; Comastri, A.; Zamorani, G.

2014-02-01

We report ALMA Cycle 0 observations at 1.3 mm of LESS J033229.4-275619 (XID403), an ultraluminous infrared galaxy at z = 4.75 in the Chandra Deep Field South hosting a Compton-thick QSO. The source is not resolved in our data at a resolution of ~0.75 arcsec, placing an upper-limit of 2.5 kpc to the half-light radius of the continuum emission from heated-dust. After deconvolving for the beam size, however, we found a ~3σ indication of an intrinsic source size of 0.27 ± 0.08 arcsec (Gaussian FWHM), which would correspond to rhalf ~ 0.9 ± 0.3 kpc. We build the far-infrared SED of XID403 by combining datapoints from both ALMA and Herschel and fit it with a modified blackbody spectrum. For the first time, we measure the dust temperature Td = 58.5 ± 5.3 K in this system, which is comparable to what has been observed in other high-z submillimeter galaxies. The measured star formation rate is SFR = 1020 ± 150 M⊙ yr-1, in agreement with previous estimates at lower S/N. Based on the measured SFR and source size, we constrain the SFR surface density to be ΣSFR > 26M⊙ yr-1 kpc-2 (~200M⊙ yr-1 kpc-2 for rhalf ~ 0.9 kpc). The compactness of this starburst is comparable to what has been observed in other local and high-z starburst galaxies. If the gas mass measured from previous [CII] and CO(2-1) observations at low resolution is confined within the same dust region, assuming rhalf ~ 0.9 ± 0.3 kpc, this would produce a column density of NH ~ 0.3-1.1 × 1024 cm-2 towards the central SMBH, similar to the column density of ≈1.4 × 1024 cm-2 measured from the X-rays. Then, in principle, if both gas and dust were confined on sub-kpc scales, this would be sufficient to produce the observed X-ray column density without any need of a pc-scale absorber (e.g. the torus postulated by Unified Models). We speculate that the high compactness of star formation, together with the presence of a powerful AGN, likely produce an outflowing wind. This would be consistent with the ~350 km s-1 velocity shift observed between the Lyα emission and the submm lines ([CII], CO(2-1), [NII]) and with the highly-ionized Fe emission line at ~6.9 keV rest-frame tentatively observed in the X-ray spectrum. Finally, our observations show that, besides the mass, star formation rate and gas depletion timescale, XID403 has also the right size to be one of the progenitors of the compact quiescent massive galaxies seen at z ~ 3.

AGN fuelling: Bridging Large and Small Scales - Overlapping Inflows as Catalysts of Accretion

NASA Astrophysics Data System (ADS)

Manuel Carmona Loaiza, Juan Manuel

2015-05-01

One of the biggest challenges in understanding the fuelling of supermassive black holes in active galactic nuclei (AGN) is not on accounting for the source of fuel, as a galaxy can comfortably supply the required mass budget, but on its actual delivery. While a clear picture has been developed for the large scale (~ kpc) down to the intermediate one (~ 100 pc), and for the smallest scales (~ 0.1 pc) where an accretion disc likely forms, a bridge that has proven difficult to build is that between ~ 100 pc and ~ 0.1 pc. It is feared that gas at these scales might still retain enough angular momentum and settle into a larger scale disc with very low or no inflow to form or replenish the inner accretion disc (on ~ 0.01 pc scales). In this Thesis, I present numerical simulations in which a rotating gaseous shell flows towards a SMBH because of its lack of rotational support. As inflow proceeds, gas from the shell impacts an already present nuclear (~ 10pc) disc. The cancellation of angular momentum and redistribution of gas, due to the misalignment between the angular momentum of the shell and that of the disc, is studied in this scenario. The underlying hypothesis is that even if transport of angular momentum at these scales may be inefficient, the interaction of an inflow with a nuclear disc would still provide a mechanism to bring mass inwards because of the cancellation of angular momentum. I quantify the amount of gas such a cancellation would bring to the central parsec under different circumstances: Co- and counter-rotation between the disc and the shell and the presence or absence of an initial turbulent kick; I also discuss the impact of self gravity in our simulations. The scenario we study is highly idealized and designed to capture the specific outcomes produced by the mechanism proposed. I find that angular momentum cancellation and redistribution via hydrodynamical shocks leads to sub-pc inflows enhanced by more than 2-3 orders of magnitude. In all of our simulations, the gas inflow rate across the inner parsec is higher than in the absence of the interaction. Gas mixing changes the orientation of the nuclear disc as the interaction proceeds until warped discs or nested misaligned rings form as relic structures. The amount of inflow depends mainly on the spin orientation of the shell relative to the disc, while the relic warped disc structure depends mostly on the turbulent kick given to the gaseous shell in the initial conditions. The main conclusion of this Thesis is that actual cancellation of angular momentum within galactic nuclei can have a significant impact on feeding super massive black holes. Such cancellation by inflow-disc interactions would leave warped 10 - 20 pc discs as remnants.

Simulating the dust content of galaxies: successes and failures

NASA Astrophysics Data System (ADS)

McKinnon, Ryan; Torrey, Paul; Vogelsberger, Mark; Hayward, Christopher C.; Marinacci, Federico

2017-06-01

We present full-volume cosmological simulations, using the moving-mesh code arepo to study the coevolution of dust and galaxies. We extend the dust model in arepo to include thermal sputtering of grains and investigate the evolution of the dust mass function, the cosmic distribution of dust beyond the interstellar medium and the dependence of dust-to-stellar mass ratio on galactic properties. The simulated dust mass function is well described by a Schechter fit and lies closest to observations at z = 0. The radial scaling of projected dust surface density out to distances of 10 Mpc around galaxies with magnitudes 17 < I < 21 is similar to that seen in Sloan Digital Sky Survey data, albeit with a lower normalization. At z = 0, the predicted dust density of Ωdust ≈ 1.3 × 10-6 lies in the range of Ωdust values seen in low-redshift observations. We find that the dust-to-stellar mass ratio anticorrelates with stellar mass for galaxies living along the star formation main sequence. Moreover, we estimate the 850 μm number density functions for simulated galaxies and analyse the relation between dust-to-stellar flux and mass ratios at z = 0. At high redshift, our model fails to produce enough dust-rich galaxies, and this tension is not alleviated by adopting a top-heavy initial mass function. We do not capture a decline in Ωdust from z = 2 to 0, which suggests that dust production mechanisms more strongly dependent on star formation may help to produce the observed number of dusty galaxies near the peak of cosmic star formation.

Matrix-array 3-dimensional echocardiographic assessment of volumes, mass, and ejection fraction in young pediatric patients with a functional single ventricle: a comparison study with cardiac magnetic resonance.

PubMed

Soriano, Brian D; Hoch, Martin; Ithuralde, Alejandro; Geva, Tal; Powell, Andrew J; Kussman, Barry D; Graham, Dionne A; Tworetzky, Wayne; Marx, Gerald R

2008-04-08

Quantitative assessment of ventricular volumes and mass in pediatric patients with single-ventricle physiology would aid clinical management, but it is difficult to obtain with 2-dimensional echocardiography. The purpose of the present study was to compare matrix-array 3-dimensional echocardiography (3DE) measurements of single-ventricle volumes, mass, and ejection fraction with those measured by cardiac magnetic resonance (CMR) in young patients. Twenty-nine patients (median age, 7 months) with a functional single ventricle undergoing CMR under general anesthesia were prospectively enrolled. The 3DE images were acquired at the conclusion of the CMR. Twenty-seven of 29 3DE data sets (93%) were optimal for 3DE assessment. Two blinded and independent observers performed 3DE measurements of volume, mass, and ejection fraction. The 3DE end-diastolic volume correlated well (r=0.96) but was smaller than CMR by 9% (P<0.01), and 3DE ejection fraction was smaller than CMR by 11% (P<0.01). There was no significant difference in measurements of end-systolic volume and mass. The 3DE interobserver differences for mass and volumes were not significant except for ejection fraction (8% difference; P<0.05). Intraobserver differences were not significant. In young pediatric patients with a functional single ventricle, matrix-array 3DE measurements of mass and volumes compare well with those obtained by CMR. 3DE will provide an important modality for the serial analysis of ventricular size and performance in young patients with functional single ventricles.