Science.gov

Sample records for dynamic galactic mass

  1. Masses, luminosities and dynamics of galactic molecular clouds

    NASA Technical Reports Server (NTRS)

    Solomon, P. M.; Rivolo, A. R.; Mooney, T. J.; Barrett, J. W.; Sage, L. J.

    1987-01-01

    Star formation in galaxies takes place in molecular clouds and the Milky Way is the only galaxy in which it is possible to resolve and study the physical properties and star formation activity of individual clouds. The masses, luminosities, dynamics, and distribution of molecular clouds, primarily giant molecular clouds in the Milky Way are described and analyzed. The observational data sets are the Massachusetts-Stony Brook CO Galactic Plane Survey and the IRAS far IR images. The molecular mass and infrared luminosities of glactic clouds are then compared with the molecular mass and infrared luminosities of external galaxies.

  2. Impact Crises, Mass Extinctions, and Galactic Dynamics: A Unified Theory

    NASA Technical Reports Server (NTRS)

    Rampino, M.R.

    1997-01-01

    A general hypothesis linking mass extinctions of life with impacts of large asteroids and comets is based on astronomical data, impact dynamics, and geological information. The waiting times of large-body impacts on the Earth, derived from the flux of Earth-crossing asteroids and comets, and the estimated size of impacts capable of causing large-scale environmental disasters predict that impacts of objects (sup 3)5 km in diameter ((sup 3)10(exp 7) Mt TNT equivalent) could be sufficient to explain the record of about 25 extinction pulses in the last 540 m.y., with the five recorded major mass extinctions related to the impacts of the largest objects of (sup 3)10 km in diameter ( (sup 3)10(exp 8) Mt events). Smaller impacts (about 10(exp 6)-10(exp 7) Mt), with significant regional and even global environmental effects, could be responsible for the lesser boundaries in the geologic record. Tests of the "kill curve" relationship for impact-induced extinctions based on new data on extinction intensities and several well-dated large impact craters suggest that major mass extinctions require large impacts, and that a step in the kill curve may exist at impacts that produce craters of -100 km diameter, with smaller impacts capable of only relatively weak extinction pulses. Single impact craters < about 60 km in diameter should not be associated with global extinction pulses detectable in the Sepkoski database (although they may explain stage and zone boundaries marked by lesser faunal turnover), but multiple impacts in that size range may produce significant stepped extinction pulses. Statistical tests of the last occurrences of species at mass-extinction boundaries are generally consistent with predictions for abrupt or stepped extinctions, and several boundaries are known to show "catastrophic" signatures of environmental disasters and biomass crash, impoverished postextinction fauna and flora dominated by stress-tolerant and opportunistic species, and gradual ecological

  3. Topics in galactic dynamics

    NASA Astrophysics Data System (ADS)

    Little, Frank Blane

    1989-01-01

    The distant satellites of the Milky Way Galaxy are used to probe the distribution of dark matter in the Galactic halo. A new method of statistical analysis based on Bayes' theorem was devised, which directly yields confidence intervals for the mass of the Galaxy once the eccentricity distribution of the satellites is specified. Assuming an isotropic velocity distribution for 10 objects at distances of 50 to 140 kiloparsecs, mass results suggest that the Galaxy's massive dark halo extends to approximately less than 50 kiloparsecs from the Galactic center. A model galaxy with an artificial bar is used to explore the effect of dynamical friction on a galactic bar. An analytic formula is provided which correctly predicts angular momentum changes for a bar in interaction with a non self-gravitating disk. N-body simulations further show that disk self-gravity tends to make a bar without inner Lindblad resonances spin down more rapidly, and tends to make a bar dominated by inner Lindblad resonances spin up less rapidly. The long-term dynamical evolution of galactic bars is investigated using fully self gravitating bar-unstable disk-halo models. The models develop rapidly rotating bars which then slow down through transfers of angular momentum both to the outer disk and to the halo. The models suggest that the distance between the end of a bar and its corotation circle is proportional to the bar's age, and an approximate formula is presented which expresses this relationship. It is also concluded that the average tangential velocity within a barlike object drops by a factor of about 2 over approximately 45 initial rotation periods.

  4. On the mass of ultra-light bosonic dark matter from galactic dynamics

    SciTech Connect

    Lora, V.; Grebel, E.K.; Magaña, Juan; Sánchez-Salcedo, F.J.; Bernal, Argelia E-mail: jmagana@astroscu.unam.mx E-mail: jsanchez@astroscu.unam.mx

    2012-02-01

    We consider the hypothesis that galactic dark matter is composed of ultra-light scalar particles and use internal properties of dwarf spheroidal galaxies to establish a preferred range for the mass m{sub φ} of these bosonic particles. We re-investigate the problem of the longevity of the cold clump in Ursa Minor and the problem of the rapid orbital decay of the globular clusters in Fornax and dwarf ellipticals. Treating the scalar field halo as a rigid background gravitational potential and using N-body simulations, we have explored how the dissolution timescale of the cold clump in Ursa Minor depends on m{sub φ}. It is demonstrated that for masses in the range 0.3 × 10{sup −22} eV < m{sub φ} < 1 × 10{sup −22} eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the cold clump in Ursa Minor and the wide distribution of globular clusters in Fornax, but small enough to make the mass of the dark halos compatible with dynamical limits. It is encouraging to see that this interval of m{sub φ} is consistent with that needed to suppress the overproduction of substructure in galactic halos and is compatible with the acoustic peaks of cosmic microwave radiation. On the other hand, for self-interacting scalar fields with coupling constant λ, values of m{sub φ}{sup 4}/λ∼<0.55 × 10{sup 3} eV{sup 4} are required to account for the properties of the dark halos of these dwarf spheroidal galaxies.

  5. Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. III. Dynamical Distances and Mass-to-Light Ratios

    NASA Astrophysics Data System (ADS)

    Watkins, Laura L.; van der Marel, Roeland P.; Bellini, Andrea; Anderson, Jay

    2015-10-01

    We present dynamical distance estimates for 15 Galactic globular clusters (GCs) and use these to check the consistency of dynamical and photometric distance estimates. For most of the clusters, this is the first dynamical distance estimate ever determined. We extract proper-motion (PM) dispersion profiles using cleaned samples of bright stars from the Hubble Space Telescope PM catalogs recently presented in Bellini et al. and compile a set of line of sight (LOS) velocity-dispersion profiles from a variety of literature sources. Distances are then estimated by fitting spherical, non-rotating, isotropic, constant mass-to-light ratio (M/L) dynamical models to the PM and LOS dispersion profiles together. We compare our dynamical distance estimates with literature photometric estimates from the Harris GC catalog and find that the mean fractional difference between the two types is consistent with zero at just -1.9 ± 1.7%. This indicates that there are no significant biases in either estimation method and provides an important validation of the stellar-evolution theory that underlies photometric distance estimates. The analysis also estimates dynamical M/Ls for our clusters; on average, the dynamically inferred M/Ls agree with existing stellar-population-based M/Ls that assume a Chabrier initial mass function (IMF) to within -8.8 ± 6.4%, implying that such an IMF is consistent with our data. Our results are also consistent with a Kroupa IMF, but strongly rule out a Salpeter IMF. We detect no correlation between our M/L offsets from literature values and our distance offsets from literature values, strongly indicating that our methods are reliable and our results are robust. Based on proprietary and archival observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  6. Special Features of Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Efthymiopoulos, Christos; Voglis, Nikos; Kalapotharakos, Constantinos

    This is an introductory article to some basic notions and currently open problems of galactic dynamics. The focus is on topics mostly relevant to the so-called `new methods' of celestial mechanics or Hamiltonian dynamics, as applied to the ellipsoidal components of galaxies, i.e., to the elliptical galaxies and to the dark halos and bulges of disk galaxies. Traditional topics such as Jeans theorem, the role of a `third integral' of motion, Nekhoroshev theory, violent relaxation, and the statistical mechanics of collisionless stellar systems are first discussed. The emphasis is on modern extrapolations of these old topics. Recent results from orbital and global dynamical studies of galaxies are then shortly reviewed. The role of various families of orbits in supporting self-consistency, as well as the role of chaos in galaxies, are stressed. A description is then given of the main numerical techniques of integration of the N-body problem in the framework of stellar dynamics and of the results obtained via N-Body experiments. A final topic is the secular evolution and self-organization of galactic systems.

  7. Galactic Stellar and Substellar Initial Mass Function

    NASA Astrophysics Data System (ADS)

    Chabrier, Gilles

    2003-07-01

    formation at large redshift remains undetermined, but different observational constraints suggest that it does not extend below ~1 Msolar. These results suggest a characteristic mass for star formation that decreases with time, from conditions prevailing at large redshift to conditions characteristic of the spheroid (or thick disk) to present-day conditions. These conclusions, however, remain speculative, given the large uncertainties in the spheroid and early star IMF determinations. These IMFs allow a reasonably robust determination of the Galactic present-day and initial stellar and brown dwarf contents. They also have important galactic implications beyond the Milky Way in yielding more accurate mass-to-light ratio determinations. The mass-to-light ratios obtained with the disk and the spheroid IMF yield values 1.8-1.4 times smaller than for a Salpeter IMF, respectively, in agreement with various recent dynamical determinations. This general IMF determination is examined in the context of star formation theory. None of the theories based on a Jeans-type mechanism, where fragmentation is due only to gravity, can fulfill all the observational constraints on star formation and predict a large number of substellar objects. On the other hand, recent numerical simulations of compressible turbulence, in particular in super-Alfvénic conditions, seem to reproduce both qualitatively and quantitatively the stellar and substellar IMF and thus provide an appealing theoretical foundation. In this picture, star formation is induced by the dissipation of large-scale turbulence to smaller scales through radiative MHD shocks, producing filamentary structures. These shocks produce local nonequilibrium structures with large density contrasts, which collapse eventually in gravitationally bound objects under the combined influence of turbulence and gravity. The concept of a single Jeans mass is replaced by a distribution of local Jeans masses, representative of the lognormal probability

  8. Mass content around Galactic VHE sources

    NASA Astrophysics Data System (ADS)

    de Ona Wilhelmi, Emma; Pedaletti, Giovanna; Torres, Diego; Natale, Giovanni

    2015-08-01

    A large number of Galactic very-high energy (VHE; E>100 GeV) gamma-ray sources have been discovered in the past years with ground-based Cherenkov telescopes, being a large fraction of them still unidentified. The association of these VHE sources with regions of the sky rich in dust and gas has been noticed in the study of individual VHE sources. These regions are usually associated with environments with high stellar activity, implying the presence of evolved objects like supernova remnants or pulsar wind nebulae. The estimation of the mass content around VHE sources is crucial to understand acceleration in such sources, specially when the emission is due to hadronic interaction of accelerated particles with the target mass. Using the recently released all-sky maps of astrophysical foregrounds of the Planck satellite, we tested the correlation level at large scale between the Galactic VHE population and mass enhancement. We also explored the possibility that the unidentified sources are located in ambients particularly rich in material content unaccounted by traditional radio (CO lines) tracers. The results of this investigation will be presented and the implications on the VHE emission discussed.

  9. Constraints on Galactic intermediate mass black holes

    NASA Astrophysics Data System (ADS)

    Mapelli, M.; Ferrara, A.; Rea, N.

    2006-05-01

    Intermediate mass black holes (IMBHs; 101.3 to 105Msolar) are thought to form as relics of Population III stars or from the runaway collapse of stars in young clusters; their number and very existence are uncertain. We ran N-body simulations of Galactic IMBHs, modelling them as a halo population distributed according to a Navarro, Frenk & White (NFW) or a more concentrated Diemand, Madau & Moore (DMM) density profile. As IMBHs pass through Galactic molecular/atomic hydrogen regions, they accrete gas, thus becoming X-ray sources. We constrain the density of Galactic IMBHs, Ω•, by comparing the distribution of simulated X-ray sources with the observed one. From the null detections of Milky Way ultra-luminous X-ray sources, and from a comparison of simulations with unidentified sources in the Imager on Board the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) Satellite/INTEGRAL Soft Gamma-Ray Imager (IBIS/ISGRI) catalogue, we find a strong upper limit Ω•<= 10-2Ωb(<=10-1Ωb) for a DMM (NFW) profile, if IMBHs accrete via advection-dominated accretion flow (ADAF) discs. Slightly stronger constraints (Ω•<= 10-3Ωb for a DMM profile; Ω•<= 10-2Ωb for a NFW profile) can be derived if IMBHs accrete with higher efficiency, such as by forming thin accretion discs. Although not very tight, such constraints are the most stringent ones derived so far in the literature.

  10. Galactic Dynamics and Evolution: Mergers and Infall

    NASA Astrophysics Data System (ADS)

    Weil, Melinda Loving

    1995-01-01

    Collisions and mergers are cited as culprits in the production of a large range of morphological phenomena observed in galaxies. Galactic interactions may generate faint structures, such as arcs and rings, or create an entirely different type of galaxy, depending on the types of galaxies involved and their orbital geometry. I develop detailed merger and infall models which are compared with observations in order to elucidate the dynamical processes which govern galactic formation and evolution. In a first project, the effect of including gas is studied in encounters between low-mass companions and elliptical galaxies which produce sharp-edged features called "shells." Ellipticals accrete gas, which may be important in constraining their evolution. Numerical simulations of tidal disruption of dwarf galaxies containing both gas and stars were performed. The stellar and gaseous components rapidly segregate to produce very different structures. Gaseous remnants are dense, concentrated structures that form when gas flows into the center of the galaxy. Star formation is expected in the nucleus, localized and distinctly separate from the stellar remnant. In a second project, the formation of a peculiar ring galaxy is modeled. The Cartwheel galaxy, in addition to an outer and inner ring, has several spokes which connect the two. In an attempt to reproduce the spokes, a fully self-consistent model is constructed in which a companion collides head-on with a primary consisting of a live halo and a disk containing both stars and gas. Stars and gas react to passage of the companion through the disk by producing a morphology similar to that of the Cartwheel. The region between the inner and outer rings contains several spokes with a clumpy, interrupted structure. Finally, models of both pairs and small groups of bulge-disk-halo galaxies are merged to form remnants that evince properties similar to elliptical galaxies. I analyze the spatial and kinematic characteristics of

  11. Galactic civilizations - Population dynamics and interstellar diffusion

    NASA Technical Reports Server (NTRS)

    Newman, W. I.; Sagan, C.

    1981-01-01

    A model is developed of the interstellar diffusion of galactic civilizations which takes into account the population dynamics of such civilizations. The problem is formulated in terms of potential theory, with a family of nonlinear partial differential and difference equations specifying population growth and diffusion for an organism with advantageous genes that undergoes random dispersal while increasing in population locally, and a population at zero population growth. In the case of nonlinear diffusion with growth and saturation, it is found that the colonization wavefront from the nearest independently arisen galactic civilization can have reached the earth only if its lifetime exceeds 2.6 million years, or 20 million years if discretization can be neglected. For zero population growth, the corresponding lifetime is 13 billion years. It is concluded that the earth is uncolonized not because interstellar spacefaring civilizations are rare, but because there are too many worlds to be colonized in the plausible colonization lifetime of nearby civilizations, and that there exist no very old galactic civilizations with a consistent policy of the conquest of inhabited worlds.

  12. Mass Distributions Implying Flat Galactic Rotation Curves

    ERIC Educational Resources Information Center

    Keeports, David

    2010-01-01

    The rotational speeds of stars in the disc of a spiral galaxy are virtually independent of the distances of the stars from the centre of the galaxy. In common parlance, the stellar speed versus distance plot known as a galactic rotation curve is by observation typically nearly flat. This observation provides strong evidence that most galactic…

  13. galpy: A python LIBRARY FOR GALACTIC DYNAMICS

    SciTech Connect

    Bovy, Jo

    2015-02-01

    I describe the design, implementation, and usage of galpy, a python package for galactic-dynamics calculations. At its core, galpy consists of a general framework for representing galactic potentials both in python and in C (for accelerated computations); galpy functions, objects, and methods can generally take arbitrary combinations of these as arguments. Numerical orbit integration is supported with a variety of Runge-Kutta-type and symplectic integrators. For planar orbits, integration of the phase-space volume is also possible. galpy supports the calculation of action-angle coordinates and orbital frequencies for a given phase-space point for general spherical potentials, using state-of-the-art numerical approximations for axisymmetric potentials, and making use of a recent general approximation for any static potential. A number of different distribution functions (DFs) are also included in the current release; currently, these consist of two-dimensional axisymmetric and non-axisymmetric disk DFs, a three-dimensional disk DF, and a DF framework for tidal streams. I provide several examples to illustrate the use of the code. I present a simple model for the Milky Way's gravitational potential consistent with the latest observations. I also numerically calculate the Oort functions for different tracer populations of stars and compare them to a new analytical approximation. Additionally, I characterize the response of a kinematically warm disk to an elliptical m = 2 perturbation in detail. Overall, galpy consists of about 54,000 lines, including 23,000 lines of code in the module, 11,000 lines of test code, and about 20,000 lines of documentation. The test suite covers 99.6% of the code. galpy is available at http://github.com/jobovy/galpy with extensive documentation available at http://galpy.readthedocs.org/en/latest.

  14. galpy: A python Library for Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Bovy, Jo

    2015-02-01

    I describe the design, implementation, and usage of galpy, a python package for galactic-dynamics calculations. At its core, galpy consists of a general framework for representing galactic potentials both in python and in C (for accelerated computations); galpy functions, objects, and methods can generally take arbitrary combinations of these as arguments. Numerical orbit integration is supported with a variety of Runge-Kutta-type and symplectic integrators. For planar orbits, integration of the phase-space volume is also possible. galpy supports the calculation of action-angle coordinates and orbital frequencies for a given phase-space point for general spherical potentials, using state-of-the-art numerical approximations for axisymmetric potentials, and making use of a recent general approximation for any static potential. A number of different distribution functions (DFs) are also included in the current release; currently, these consist of two-dimensional axisymmetric and non-axisymmetric disk DFs, a three-dimensional disk DF, and a DF framework for tidal streams. I provide several examples to illustrate the use of the code. I present a simple model for the Milky Way's gravitational potential consistent with the latest observations. I also numerically calculate the Oort functions for different tracer populations of stars and compare them to a new analytical approximation. Additionally, I characterize the response of a kinematically warm disk to an elliptical m = 2 perturbation in detail. Overall, galpy consists of about 54,000 lines, including 23,000 lines of code in the module, 11,000 lines of test code, and about 20,000 lines of documentation. The test suite covers 99.6% of the code. galpy is available at http://github.com/jobovy/galpy with extensive documentation available at http://galpy.readthedocs.org/en/latest.

  15. No Evidence of Mass Segregation in the Low-mass Galactic Globular Cluster NGC 6101

    NASA Astrophysics Data System (ADS)

    Dalessandro, E.; Ferraro, F. R.; Massari, D.; Lanzoni, B.; Miocchi, P.; Beccari, G.

    2015-09-01

    We used a combination of Hubble Space Telescope and ground-based data to probe the dynamical state of the low-mass Galactic globular cluster NGC 6101. We have rederived the structural parameters of the cluster by using star counts and we find that it is about three times more extended than thought before. By using three different indicators, namely the radial distribution of blue straggler stars (BSSs), that of main-sequence binaries, and the luminosity (mass) function, we demonstrated that NGC 6101 shows no evidence of mass segregation, even in the innermost regions. Indeed, both the BSS and the binary radial distributions fully resemble those of any other cluster population. In addition, the slope of the luminosity (mass) function does not change with the distance, as expected for non-relaxed stellar systems. NGC 6101 is one of the few globulars where the absence of mass segregation has been observed so far. This result provides additional support for the use of the “dynamical clock” calibrated on the radial distribution of the blue stragglers as a powerful indicator of the cluster dynamical age. Based on observations collected at the the Very Large Telescope of the European Southern Observatory, Cerro Paranal, Chile (under proposal 091.D-0562). Also based on observations with the NASA/ESA HST (Prop. 10775), obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

  16. Chemical and dynamical evolution of galactic discs

    NASA Technical Reports Server (NTRS)

    Clarke, Catherine J.

    1989-01-01

    The relative roles of star formation and viscously-induced radial flows in galactic disks are discussed. It is shown that the present-day distributions of stars, gas, and metals in galactic spirals need not reflect initial conditions but may instead indicate a cooperation between star forming and viscous processes over the disk lifetime.

  17. Dynamical Simulations of Molecular Clouds in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Salas, Jesus; Morris, Mark

    2016-06-01

    The formation of the central massive cluster of young stars orbiting the Galactic black hole, Sgr A*, has been modeled by several groups by invoking an almost radially infalling molecular cloud that interacts with the black hole and creates a dense, gaseous disk in which stars can then form. However, the dynamical origin of such a cloud remains an open question. We present simulations of the central 30-100 pc of the Milky Way, starting from a population of molecular clouds located in a disk with scale height of ~30 pc, using the N-body/smoothed-particle hydrodynamics code, Gadget2. We followed the dynamical evolution of clouds in a galactic potential that includes a bar to explore whether cloud collisions or a succession of cloud scatterings can remove sufficient angular momentum from a massive cloud to endow it with a predominantly radial orbit. Initial results illustrate the importance of tidal shear; while dense cloud cores remain identifiable for extended periods of time, much of the molecular mass ends up in tidal streams, so cannot be deflected onto low angular momentum orbits by their mutual interactions. At the completion of our ongoing computations, we will report on whether the cloud cores can undergo sufficient scattering to achieve low-angular-momentum orbits.

  18. Elucidation of kinematical and dynamical structure of the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Yano, T.; Gouda, N.; Ueda, H.; Koyama, H.; Kan-ya, Y.; Taruya, A.

    2008-07-01

    Future space mission of astrometric satellite, GAIA and JASMINE (Japan Astrometry Satellite Mission for Infrared Exploration), will produce astrometric parameter, such as positions, parallaxes, and proper motions of stars in the Galactic bulge. Then kinematical information will be obtained in the future. Accordingly it is expected that our understanding of the dynamical structure will be greatly improved. Therefore it is important to make a method to construct a kinematical and dynamical structure of the Galactic bulge immediately.

  19. New Insights on the Galactic Bulge Initial Mass Function

    NASA Astrophysics Data System (ADS)

    Calamida, A.; Sahu, K. C.; Casertano, S.; Anderson, J.; Cassisi, S.; Gennaro, M.; Cignoni, M.; Brown, T. M.; Kains, N.; Ferguson, H.; Livio, M.; Bond, H. E.; Buonanno, R.; Clarkson, W.; Ferraro, I.; Pietrinferni, A.; Salaris, M.; Valenti, J.

    2015-09-01

    We have derived the Galactic bulge initial mass function (IMF) of the Sagittarius Window Eclipsing Extrasolar Planet Search field in the mass range 0.15 \\lt M/{M}⊙ 1.0, using deep photometry collected with the Advanced Camera for Surveys on the Hubble Space Telescope. Observations at several epochs, spread over 9 years, allowed us to separate the disk and bulge stars down to very faint magnitudes, F814W ≈ 26 mag, with a proper-motion accuracy better than 0.5 mas yr-1 (20 km s-1). This allowed us to determine the IMF of the pure bulge component uncontaminated by disk stars for this low-reddening field in the Sagittarius window. In deriving the mass function, we took into account the presence of unresolved binaries, errors in photometry, distance modulus and reddening, as well as the metallicity dispersion and the uncertainties caused by adopting different theoretical color-temperature relations. We found that the Galactic bulge IMF can be fitted with two power laws with a break at M˜ 0.56 {M}⊙ , the slope being steeper (α =-2.41+/- 0.50) for the higher masses, and shallower (α =-1.25+/- 0.20) for the lower masses. In the high-mass range, our derived mass function agrees well with the mass function derived for other regions of the bulge. In the low-mass range however, our mass function is slightly shallower, which suggests that separating the disk and bulge components is particularly important in the low-mass range. The slope of the bulge mass function is also similar to the slope of the mass function derived for the disk in the high-mass regime, but the bulge mass function is slightly steeper in the low-mass regime. We used our new mass function to derive stellar mass-to-light values for the Galactic bulge and we obtained 2.1 \\lt M/{L}F814W \\lt 2.4 and 3.1 \\lt M/{L}F606W \\lt 3.6 according to different assumptions on the slope of the IMF for masses larger than 1{M}⊙ . Based on observations made with the NASA/ESA Hubble Space Telescope, obtained by the

  20. Dusty Mass Loss from Galactic Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

    2016-06-01

    We are probing how mass loss from Asymptotic Giant Branch (AGB) stars depends upon their metallicity. Asymptotic giant branch (AGB) stars are evolved stars that eject large parts of their mass in outflows of dust and gas in the final stages of their lives. Our previous studies focused on mass loss from AGB stars in lower metallicity galaxies: the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). In our present study, we analyze AGB star mass loss in the Galaxy, with special attention to the Bulge, to investigate how mass loss differs in an overall higher metallicity environment. We construct radiative transfer models of the spectral energy distributions (SEDs) of stars in the Galaxy identified as AGB stars from infrared and optical surveys. Our Magellanic Cloud studies found that the AGB stars with the highest mass loss rates tended to have outflows with carbon-rich dust, and that overall more carbon-rich (C-rich) dust than oxygen-rich (O-rich) was produced by AGB stars in both LMC and SMC. Our radiative transfer models have enabled us to determine reliably the dust chemistry of the AGB star from the best-fit model. For our Galactic sample, we are investigating both the dust chemistries of the AGB stars and their mass-loss rates, to compare the balance of C-rich dust to O-rich dust between the Galactic bulge and the Magellanic Clouds. We are also constructing detailed dust opacity models of AGB stars in the Galaxy for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). This detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs of Galactic AGB stars. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

  1. The central mass and mass-to-light profile of the Galactic globular cluster M15

    NASA Astrophysics Data System (ADS)

    den Brok, Mark; van de Ven, Glenn; van den Bosch, Remco; Watkins, Laura

    2014-02-01

    We analyse line-of-sight velocity and proper motion data of stars in the Galactic globular cluster M15 using a new method to fit dynamical models to discrete kinematic data. Our fitting method maximizes the likelihood for individual stars and, as such, does not suffer the same loss of spatial and velocity information incurred when spatially binning data or measuring velocity moments. In this paper, we show that the radial variation in M15 of the mass-to-light ratio is consistent with previous estimates and theoretical predictions, which verifies our method. Our best-fitting axisymmetric Jeans models do include a central dark mass of ˜2 ± 1 × 103 M⊙, which can be explained by a high concentration of stellar remnants at the cluster centre. This paper shows that, from a technical point of view and with current computing power, spatial binning of data is no longer necessary. This not only leads to more accurate fits, but also avoids biased mass estimates due to the loss of resolution. Furthermore, we find that the mass concentration in M15 is significantly higher than previously measured, and is in close agreement with theoretical predictions for core-collapsed globular clusters without a central intermediate-mass black hole.

  2. Numerical simulation of the plasma and gravitational dynamics of a galactic magnetic monopole halo

    NASA Astrophysics Data System (ADS)

    Farouki, R.; Shapiro, S. L.; Wasserman, I.

    1984-09-01

    Numerical and analytical calculations designed to assess the viability of a Galactic magnetic monopole halo are presented. The dynamical interplay between magnetic currents and the Galactic magnetic field is treated self-consistently, taking full account of the temporal evolution of currents and fields. It is found that in general self-consistent bounds on the Galactic magnetic monopole flux based on the survival of the Galactic magnetic field are far less restrictive than the Parker limit. The halo models are consistent with monopole masses m(M) approximately equal to or less than 7 x 10 to the 19th GeV, and monopole fluxes in the range F(M) approximately equal to or greater than 3 x 10 to the -13th per sq cm per s. Topics for future, more detailed studies are enumerated and discussed.

  3. JASMINE: constructor of the dynamical structure of the Galactic bulge

    NASA Astrophysics Data System (ADS)

    Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.

    2008-07-01

    We introduce a Japanese space astrometry project which is called JASMINE. JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) will measure distances and tangential motions of stars in the Galactic bulge with yet unprecedented precision. JASMINE will operate in z-band whose central wavelength is 0.9 micron. It will measure parallaxes, positions with accuracy of about 10 micro-arcsec and proper motions with accuracy of about 10 micro- arcsec/year for the stars brighter than z=14 mag. The number of stars observed by JASMINE with high accuracy of parallaxes in the Galactic bulge is much larger than that observed in other space astrometry projects operating in optical bands. With the completely new “map of the Galactic bulge” including motions of bulge stars, we expect that many new exciting scientific results will be obtained in studies of the Galactic bulge. One of them is the construction of the dynamical structure of the Galactic bulge. Kinematics and distance data given by JASMINE are the closest approach to a view of the exact dynamical structure of the Galactic bulge. Presently, JASMINE is in a development phase, with a target launch date around 2016. We comment on the outline of JASMINE mission, scientific targets and a preliminary design of JASMINE in this paper.

  4. The chemical evolution of Dwarf Galaxies with galactic winds - the role of mass and gas distribution

    NASA Astrophysics Data System (ADS)

    Hensler, Gerhard; Recchi, Simone

    2015-08-01

    Energetic feedback from Supernovae and stellar winds can drive galactic winds. Dwarf galaxies (DGs), due to their shallower potential wells, are assumed to be more vulnera-ble to these energetic processes. Metal loss through galactic winds is also commonly invoked to explain the low metal content of DGs.Our main aim in this presentation is to show that galactic mass cannot be the only pa-rameter determining the fraction of metals lost by a galaxy. In particular, the distribution of gas must play an equally important role. We perform 2-D chemo-dynamical simula-tions of galaxies characterized by different gas distributions, masses and gas fractions. The gas distribution can change the fraction of lost metals through galactic winds by up to one order of magnitude. In particular, disk-like galaxies tend to lose metals more easily than roundish ones. Consequently, also the final element abundances attained by models with the same mass but with different gas distributions can vary by up to one dex. Confirming previous studies, we also show that the fate of gas and freshly pro-duced metals strongly depends on the mass of the galaxy. Smaller galaxies (with shal-lower potential wells) more easily develop large-scale outflows; therefore, the fraction of lost metals tends to be higher.Another important issue is that the invoked mechanism to transform central cusps to cored dark-matter distributions by baryon loss due to strong galactic winds cannot work in general, must be critically tested, and should be clearly discernible by the chemical evolution of DGs.

  5. Cosmic Ray Variability and Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Medvedev, Mikhail

    2007-05-01

    The spectral analysis of fluctuations of biodiversity (Rohde & Muller, 2005) and the subsequent re-analysis of the diversity record, species origination and extinction rates, gene duplication, etc (Melott & Liebermann, 2007) indicate the presence of a 62$\\pm$3My cyclicity, for the last 500My. Medvedev & Melott (2006) proposed that the cyclicity may be related to the periodicity of the Solar motion with respect to the Galactic plane, which exhibits a 63My oscillation, and the inhomogeneous distribution of Cosmic Rays (CR) throughout the Milky Way, which may affect the biosphere by changing mutation rate, climate, food chain, etc. Here we present a model of CR propagation in the Galactic magnetic fields, in the presence of both the mean field gradient and the strong MHD turbulence in the interstellar medium. We explore the "magnetic shielding effect" as a function of CR energy and composition and estimate the resultant flux of mutagenic secondary muons at the Earth surface.

  6. Dynamical Structures in the Galactic Disk

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.

    2014-01-01

    Resonances with spiral density waves or the Galactic bar can cause structure in local velocity distributions (also known as phase space). Because resonances are narrow, it is possible to place tight constraints on a pattern speed or the shape of the underlying gravitational potential. Interference between multiple spiral patterns can cause localized bursts of star formation and discontinuities or kinks in the spiral arm morphology. Numerical simulations suggest that boundaries between different dominant patterns in the disk can manifest in local velocity distributions as gaps that are associated with specific orbital periods or angular momentum values. Recent studies have detected age gradients that may be associated with the appearance of spiral features such as armlets and spurs. When patterns grow or vary in speed, resonances can be swept through the disk causing changes in the velocity distributions. Evidence of resonance capture or resonance crossing can be used to place constraints on the past history of patterns in the disk. The X-shaped Galactic bulge may have been caused by stars captured into vertical resonance with the Bar. Disturbances in the Galactic disk, such as from a past merger, can cause an uneven distribution of disk stars in action angles. Subsequently the stellar distribution becomes more tightly wound in phase space. Phase wrapping can cause a series of shell like features in either real space or in a local velocity distribution. The spacing between features is dependent on the time since the disturbance.

  7. Galactic evolution. I - Single-zone models. [encompassing stellar evolution and gas-star dynamic theories

    NASA Technical Reports Server (NTRS)

    Thuan, T. X.; Hart, M. H.; Ostriker, J. P.

    1975-01-01

    The two basic approaches of physical theory required to calculate the evolution of a galactic system are considered, taking into account stellar evolution theory and the dynamics of a gas-star system. Attention is given to intrinsic (stellar) physics, extrinsic (dynamical) physics, and computations concerning the fractionation of an initial mass of gas into stars. The characteristics of a 'standard' model and its variants are discussed along with the results obtained with the aid of these models.

  8. Multiscale mass transport in z ˜6 galactic discs: fuelling black holes

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Escala, Andrés

    2016-08-01

    By using Adaptive Mesh Refinement cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code, we studied the mass transport processes on to galactic nuclei from high redshift up to z ˜6. Due to the large dynamical range of the simulations, we were able to study the mass accretion process on scales from ˜50 kpc to ˜few 1 pc. We studied the black hole (BH) growth on to the Galactic Centre in relation with the mass transport processes associated to both the Reynolds stress and the gravitational stress on the disc. Such methodology allowed us to identify the main mass transport process as a function of the scales of the problem. We found that in simulations that include radiative cooling and supernovae feedback, the supermassive black hole (SMBH) grows at the Eddington limit for some periods of time presenting ≈ 0.5 throughout its evolution. The α parameter is dominated by the Reynolds term, αR, with αR ≫ 1. The gravitational part of the α parameter, αG, has an increasing trend towards the Galactic Centre at higher redshifts, with values αG ˜1 at radii ≲ few 101 pc contributing to the BH fuelling. In terms of torques, we also found that gravity has an increasing contribution towards the Galactic Centre at earlier epochs with a mixed contribution above ˜100 pc. This complementary work between pressure gradients and gravitational potential gradients allows an efficient mass transport on the disc with average mass accretion rates of the order of ˜few 1 M⊙ yr-1. These levels of SMBH accretion rates found in our cosmological simulations are needed in all models of SMBH growth that attempt to explain the formation of redshift 6-7 quasars.

  9. Multiscale mass transport in z˜6 galactic discs: fueling black holes.

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Escala, Andrés

    2016-05-01

    By using AMR cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code, we studied the mass transport processes onto galactic nuclei from high redshift up to z ˜ 6. Due to the large dynamical range of the simulations we were able to study the mass accretion process on scales from ˜50[kpc] to ˜ few 1[pc]. We studied the BH growth on to the galactic center in relation with the mass transport processes associated to both the Reynolds stress and the gravitational stress on the disc. Such methodology allowed us to identify the main mass transport process as a function of the scales of the problem. We found that in simulations that include radiative cooling and SNe feedback, the SMBH grows at the Eddington limit for some periods of time presenting ≈ 0.5 throughout its evolution. The α parameter is dominated by the Reynolds term, αR, with αR ≫ 1. The gravitational part of the α parameter, αG, has an increasing trend toward the galactic center at higher redshifts, with values αG ˜ 1 at radii ≲ few 101[pc] contributing to the BH fueling. In terms of torques, we also found that gravity has an increasing contribution toward the galactic center at earlier epochs with a mixed contribution above ˜100[pc]. This complementary work between pressure gradients and gravitational potential gradients allows an efficient mass transport on the disc with average mass accretion rates of the order ˜ few 1[M⊙/yr]. These level of SMBH accretion rates found in our cosmological simulations are needed in all models of SMBH growth that attempt to explain the formation of redshift 6 - 7 quasars.

  10. Multiscale mass transport inz ˜6 galactic discs: fuelling black holes

    NASA Astrophysics Data System (ADS)

    Prieto, Joaquin; Escala, Andrés

    2016-08-01

    By using AMR cosmological hydrodynamic N-body zoom-in simulations, with the RAMSES code, we studied the mass transport processes onto galactic nuclei from high redshift up to $z\\sim6$. Due to the large dynamical range of the simulations we were able to study the mass accretion process on scales from $\\sim50[kpc]$ to $\\sim$ few $1[pc]$. We studied the BH growth on to the galactic center in relation with the mass transport processes associated to both the Reynolds stress and the gravitational stress on the disc. Such methodology allowed us to identify the main mass transport process as a function of the scales of the problem. We found that in simulations that include radiative cooling and SNe feedback, the SMBH grows at the Eddington limit for some periods of time presenting $\\langle f_{EDD}\\rangle\\approx 0.5$ throughout its evolution. The $\\alpha$ parameter is dominated by the Reynolds term, $\\alpha_R$, with $\\alpha_R\\gg 1$. The gravitational part of the $\\alpha$ parameter, $\\alpha_G$, has an increasing trend toward the galactic center at higher redshifts, with values $\\alpha_G\\sim 1$ at radii <$\\sim$ few $ 10^1[pc]$ contributing to the BH fueling. In terms of torques, we also found that gravity has an increasing contribution toward the galactic center at earlier epochs with a mixed contribution above $\\sim 100 [pc]$. This complementary work between pressure gradients and gravitational potential gradients allows an efficient mass transport on the disc with average mass accretion rates of the order $\\sim$ few $1 [M_{\\odot}/yr]$. These level of SMBH accretion rates found in our cosmological simulations are needed in all models of SMBH growth that attempt to explain the formation of redshift $6-7$ quasars.

  11. The role of collective effects and secular mass migration on galactic transformation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolei; Buta, Ronald J.

    2015-03-01

    During the lifetime of a galaxy, secular radial mass redistribution is expected to gradually build up a bulge and transform the Hubble type from late to early. The dominant dynamical process responsible for this transformation is a collective instability mediated by density-wave collisionless shocks (Zhang 1996, 1998, 1999). The ability of this new mechanism to secularly redistribute the STELLAR mass provides a general pathway for the formation and evolution of the majority of Hubble types, ranging from late type disk galaxiess to disky ellipticals. ATLAS3D results (Cappellari et al. 2013) showed that spirals and S0s and disky ellipticals form a continuous trend of evolution which also coincides with the aging of the stellar population of galactic disks. The importance of stellar accretion is also revealed in the results of the COSMOS team which showed that the evolution of the black-hole-mass/bulge-mass correlation since z = 1 was mainly due to the mass redistribution on pre-existing STELLAR disks which were already in place by z = 1 (Cisternas et al. 2011). The weaker correlation between the masses of late-type bulges and AGNs observed at any given epoch in our view is a result of the quicker initial onset of accretion events in AGN disks compared to that in galactic disks, since the dynamical timescale is shorter for smaller AGN accretion disks. The same secular dynamical process can produce and maintain the well-known scaling relations and universal rotation curves of observed galaxies during their Hubble-type transformation (Zhang 2008), as well as reproduce many other observed structural and kinematic properties of galaxies such as the size-line-width relation of the interstellar medium and the age-velocity dispersion relation of solar neighborhood stars in our own Galaxy. A by-product of this analysis is a powerful new method for locating the multiple corotation resonances in galaxies (Zhang & Buta 2007; Buta & Zhang 2009). The current work also highlights

  12. SAS-2 gamma-ray results from the galactic plane and their implications for galactic structure and galactic cosmic-ray dynamics

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.

    1977-01-01

    The final SAS-2 results related to high energy galactic gamma-ray emission show a strong correlation with galactic structural features seen at other wavelenghts, when the known gamma-ray sources are subtracted. Theoretical considerations and analysis of the gamma-ray data suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density is enhanced where the matter density is greatest on the scale of the galactic arms. This concept has been explored in a galactic model that assumes: (1) cosmic rays are galactic and not universal; (2)on the scale of the galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3)the cosmic ray scale height is significantly larger than the scale height to the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of over 2:1.

  13. The IMF at intermediate masses from Galactic Cepheids

    NASA Astrophysics Data System (ADS)

    Mor, R.; Robin, A. C.; Figueras, F.; Lemasle, B.

    2014-07-01

    Aims: To constrain the Initial Mass Function (IMF) of the Galactic young (<1 Gyr) thin Disc population using Cepheids. Methods: We have optimized the flexibility of the new Besançon Galaxy Model (Czekaj 2014) to simulate magnitude and distance complete samples of young intermediate mass stars assuming different IMFs and Star Formation Histories (SFH). Comparing the simulated synthetic catalogues with the observational data we studied which IMF reproduces better the observational number of Cepheids in the Galactic thin Disc. We analysed three different IMF: (1) Salpeter, (2) Kroupa-Haywood and (3) Haywood-Robin IMFs with a decreasing SFH from Aumer & Binney (2009). Results: For the first time the Besançon Galaxy Model is used to characterize the galactic Cepheids. We found that for most of the cases the Salpeter IMF overestimates the number of observed Cepheids and Haywood-Robin IMF underestimates it. The Kroupa-Haywood IMF, with a slope α = 3.2, is the one that best reproduces the observed Cepheids. From the comparison of the predicted and observed number of Cepheids up to V = 12, we point that the model might underestimate the scale height of the young population. Conclusions: In agreement with Kroupa & Weidner (2003) our study shows that the Salpeter IMF (α = 2.35) overestimates the star counts in the range 4 ≤ M/M⊙≤ 10 and supports the idea that the slope of the intermediate and massive stars IMF is steeper than the Salpeter IMF. The poster can be found online at: https://gaia.ub.edu/Twiki/pub/GREATITNFC/ProgramFinalconference/Poster_R._Mor_Great.pdf.

  14. Galactic civilizations: Population dynamics and interstellar diffusion

    NASA Technical Reports Server (NTRS)

    Newman, W. I.; Sagan, C.

    1978-01-01

    The interstellar diffusion of galactic civilizations is reexamined by potential theory; both numerical and analytical solutions are derived for the nonlinear partial differential equations which specify a range of relevant models, drawn from blast wave physics, soil science, and, especially, population biology. An essential feature of these models is that, for all civilizations, population growth must be limited by the carrying capacity of the environment. Dispersal is fundamentally a diffusion process; a density-dependent diffusivity describes interstellar emigration. Two models are considered: the first describing zero population growth (ZPG), and the second which also includes local growth and saturation of a planetary population, and for which an asymptotic traveling wave solution is found.

  15. Dark matter superfluidity and galactic dynamics

    NASA Astrophysics Data System (ADS)

    Berezhiani, Lasha; Khoury, Justin

    2016-02-01

    We propose a unified framework that reconciles the stunning success of MOND on galactic scales with the triumph of the ΛCDM model on cosmological scales. This is achieved through the physics of superfluidity. Dark matter consists of self-interacting axion-like particles that thermalize and condense to form a superfluid in galaxies, with ∼mK critical temperature. The superfluid phonons mediate a MOND acceleration on baryonic matter. Our framework naturally distinguishes between galaxies (where MOND is successful) and galaxy clusters (where MOND is not): dark matter has a higher temperature in clusters, and hence is in a mixture of superfluid and normal phase. The rich and well-studied physics of superfluidity leads to a number of striking observational signatures.

  16. Merging of unequal mass binary black holes in non-axisymmetric galactic nuclei

    NASA Astrophysics Data System (ADS)

    Berczik, Peter; Wang, Long; Nitadori, Keigo; Spurzem, Rainer

    2016-02-01

    In this work we study the stellar-dynamical hardening of unequal mass massive black hole (MBH) binaries in the central regions of galactic nuclei. We present a comprehensive set of direct N-body simulations of the problem, varying both the total mass and the mass ratio of the MBH binary. Our initial model starts as an axisymmetric, rotating galactic nucleus, to describe the situation right after the galaxies have merged, but the black holes are still unbound to each other. We confirm that results presented in earlier works (Berczik et al. 2006; Khan et al. 2013; Wang et al. 2014) about the solution of the ``last parsec problem'' (sufficiently fast black hole coalescence for black hole growth in cosmological context) are robust for both for the case of unequal black hole masses and large particle numbers. The MBH binary hardening rate depends on the reduced mass ratio through a single parameter function, which quantitatively quite well agrees with standard 3 body scattering theory (see e.g., Hills 1983). Based on our results we conclude that MBH binaries at high redshifts are expected to merge with a factor of ~ 2 more efficiently, which is important to determine the possible overall gravitational wave signals. However, we have not yet fully covered all the possible parameter space, in particular with respect to the preceding of the galaxy mergers, which may lead to a wider variety of initial models, such as initially more oblate and / or even significantly triaxial galactic nuclei. Our N-body simulations were carried out on a new special supercomputers using the hardware acceleration with graphic processing units (GPUs).

  17. ON THE TEMPORAL EVOLUTION OF THE STELLAR MASS FUNCTION IN GALACTIC CLUSTERS

    SciTech Connect

    De Marchi, Guido; Paresce, Francesco; Portegies Zwart, Simon E-mail: paresce@iasfbo.inaf.i

    2010-07-20

    We show that we can obtain a good fit to the present-day stellar mass functions (MFs) of a large sample of young and old Galactic clusters in the range 0.1-10 M{sub sun} with a tapered power-law distribution function with an exponential truncation of the form dN/dm{proportional_to}m{sup {alpha}} [1 -e{sup -}(m/m{sub c}){sup {beta}}]. The average value of the power-law index {alpha} is {approx}-2, that of {beta} is {approx}2.5, whereas the characteristic mass m{sub c} is in the range 0.1-0.8 M {sub sun} and does not seem to vary in any systematic way with the present cluster parameters such as metal abundance, total cluster mass, or central concentration. However, m{sub c} shows a remarkable correlation with the dynamical age of the cluster, namely, m{sub c} /M {sub sun} {approx_equal} 0.15 + 0.5 x {tau}{sup 3/4}{sub dyn}, where {tau}{sub dyn} is the dynamical age taken as the ratio of cluster age and dissolution time. The small scatter seen around this correlation is consistent with the uncertainties in the estimated value of {tau}{sub dyn}. We attribute the observed trend to the onset of mass segregation via two-body relaxation in a tidal environment, causing the preferential loss of low-mass stars from the cluster and hence a drift of the characteristic mass m{sub c} toward higher values. If dynamical evolution is indeed at the origin of the observed trend, it would seem plausible that high-concentration globular clusters, now with median m{sub c} {approx_equal} 0.33 M{sub sun}, were born with a stellar MF very similar to that measured today in the youngest Galactic clusters and with a value of m{sub c} {approx_equal} 0.15 M{sub sun}. This hypothesis is consistent with the absence of a turnover in the MF of the Galactic bulge down to the observational limit at {approx}0.2 M{sub sun} and, if correct, it would carry the implication that the characteristic mass is not set by the thermal Jeans mass of the cloud.

  18. 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.

  19. THE ACS SURVEY OF GALACTIC GLOBULAR CLUSTERS. VIII. EFFECTS OF ENVIRONMENT ON GLOBULAR CLUSTER GLOBAL MASS FUNCTIONS

    SciTech Connect

    Paust, Nathaniel E. Q.; Reid, I. Neill; Anderson, Jay E-mail: inr@stsci.edu

    2010-02-15

    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, {approx}0.8 M {sub sun}, to 0.2-0.3 M {sub sun} on the lower main sequence. The slopes of those power-law fits, {alpha}, 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 {alpha} and either metallicity or Galactic location. However, we do find a strong statistical correlation with the related parameters central surface brightness, {mu} {sub V}, and inferred central density, {rho}{sub 0}. 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 {alpha}. 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.

  20. Cloud-particle galactic gas dynamics and star formation

    NASA Technical Reports Server (NTRS)

    Roberts, W. W., Jr.

    1983-01-01

    Galactic gas dynamics, spiral structure, and star formation are discussed in relation to N-body computational studies based on a cloud-particle model of the interstellar medium. On the small scale, the interstellar medium is seen as cloud-dominated and supernova-perturbed. It is noted that the cloud-particle model simulates cloud-cloud collisions, the formation of stellar associations, and supernova explosions as dominant local processes. On the large scale, in response to a spiral galactic gravitational field, global density waves and galactic shocks develop having large-scale characteristics similar to those found in continuum gas dynamical studies. Both the system of gas clouds and the system of young stellar associations forming from the clouds figure in the global spiral structure. However, with the attributes of neither assuming a continuum of gas (as in continuum gas dynamical studies) or requiring a prescribed equation of state (such as the isothermal condition), the cloud-particle picture retains much of the detail lost in earlier work. By detail is meant the small-scale features and structures so important in understanding the local, turbulent state of the interstellar medium as well as the degree of raggedness often seen to be superposed on the global spiral structure.

  1. Nonlinear Dynamics, Artificial Cognition and Galactic Export

    NASA Astrophysics Data System (ADS)

    Rössler, Otto E.

    2004-08-01

    The field of nonlinear dynamics focuses on function rather than structure. Evolution and brain function are examples. An equation for a brain, described in 1973, is explained. Then, a principle of interactional function change between two coupled equations of this type is described. However, all of this is not done in an abstract manner but in close contact with the meaning of these equations in a biological context. Ethological motivation theory and Batesonian interaction theory are reencountered. So is a fairly unknown finding by van Hooff on the indistinguishability of smile and laughter in a single primate species. Personhood and evil, two human characteristics, are described abstractly. Therapies and the question of whether it is ethically allowed to export benevolence are discussed. The whole dynamic approach is couched in terms of the Cartesian narrative, invented in the 17th century and later called Enlightenment. Whether or not it is true that a "second Enlightenment" is around the corner is the main question raised in the present paper.

  2. Dynamical Mass Generation

    SciTech Connect

    Bashir, A.; Raya, A.

    2006-09-25

    Understanding the origin of mass, in particular that of the fermions, is one of the most uncanny problems which lie at the very frontiers of particle physics. Although the celebrated Standard Model accommodates these masses in a gauge invariant fashion, it fails to predict their values. Moreover, the mass thus generated accounts for only a very small percentage of the mass which permeates the visible universe. Most of the observed mass is accounted for by the strong interactions which bind quarks into protons and neutrons. How does that exactly happen in its quantitative details is still an unsolved mystery. Lattice formulation of quantum chromodynamics (QCD) or continuum studies of its Schwinger-Dyson equations (SDEs) are two of the non-perturbative means to try to unravel how quarks, starting from negligible current masses can acquire enormously large constituent masses to account for the observed proton and neutron masses. Analytical studies of SDEs in this context are extremely hard as one has to resort to truncation schemes whose quantitative reliability can be established only after a very careful analysis. Let alone the far more complicated realm of QCD, arriving at reliable truncation schemes in simpler scenarios such as quantum electrodynamics (QED) has also proved to be a hard nut to crack. In the last years, there has been an increasing group of physicists in Mexico which is taking up the challenge of understanding how the dynamical generation of mass can be understood in a reliable way through SDEs of gauge theories in various contexts such as (i) in arbitrary space-time dimensions d as well as d {<=} 4 (ii) finite temperatures and (ii) in the presence of magnetic fields. In this article, we summarise some of this work.

  3. Active galactic nucleus black hole mass estimates in the era of time domain astronomy

    SciTech Connect

    Kelly, Brandon C.; Treu, Tommaso; Pancoast, Anna; Malkan, Matthew; Woo, Jong-Hak

    2013-12-20

    We investigate the dependence of the normalization of the high-frequency part of the X-ray and optical power spectral densities (PSDs) on black hole mass for a sample of 39 active galactic nuclei (AGNs) with black hole masses estimated from reverberation mapping or dynamical modeling. We obtained new Swift observations of PG 1426+015, which has the largest estimated black hole mass of the AGNs in our sample. We develop a novel statistical method to estimate the PSD from a light curve of photon counts with arbitrary sampling, eliminating the need to bin a light curve to achieve Gaussian statistics, and we use this technique to estimate the X-ray variability parameters for the faint AGNs in our sample. We find that the normalization of the high-frequency X-ray PSD is inversely proportional to black hole mass. We discuss how to use this scaling relationship to obtain black hole mass estimates from the short timescale X-ray variability amplitude with precision ∼0.38 dex. The amplitude of optical variability on timescales of days is also anticorrelated with black hole mass, but with larger scatter. Instead, the optical variability amplitude exhibits the strongest anticorrelation with luminosity. We conclude with a discussion of the implications of our results for estimating black hole mass from the amplitude of AGN variability.

  4. The Observed Galactic Annihilation Line: Possible Signature of Accreting Small Mass Black Holes in the Galactic Center

    NASA Technical Reports Server (NTRS)

    Titarchuk, Lev; Chardonnet, Pascal

    2006-01-01

    Various balloon and satellite observatories have revealed what appears to be an extended source of 0.511 MeV annihilation radiation with flux of approx. 10(exp -3) photons/sq cm/s centered on the Galactic Center. Positrons from radioactive products of stellar explosions can account for a significant fraction of the emission. We discuss an additional source for this emission: namely e(+)e(-) pairs produced when X-rays generated from the approx. 2.6 x 10(exp 6) solar mass Galactic Center Black Hole interact with approx. 10 MeV temperature blackbody emission from 10(exp 17) g black holes within 10(exp 14-l5) cm of the center. The number of such Small Mass Black Holes (SMMBHs) can account for the production of the 10(exp 42) e(+)/s that produces the observed annihilation in the inner Galaxy when transport effects are taken into account. We consider the possibility for confirming the presence of these SMMBHs in the Galactic Center region with future generations of gamma-ray instruments if a blackbody like emission of approx. 10 MeV temperature would be detected by them. Small Mass Black Hole can be a potential candidate for dark (invisible) matter hal

  5. Chemo-dynamics in the Heart of the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Zasowski, Gail; Ness, Melissa; García Pérez, Ana; Johnson, Jennifer

    2016-01-01

    Galactic bulges contain dense, information-rich fossil records of star formation and galaxy assembly, encoded in the chemo-dynamical patterns of the stellar populations. The Milky Way's bulge is the only one in which we can resolve the chemistry and kinematics of individual stars in those populations, but we still do not fully understand the formation and subsequent evolution of the bulge. The SDSS APOGEE survey affords the opportunity to characterize in detail large numbers of stars throughout the Milky Way's entire bulge. We present an analysis of the chemo-dynamical patterns observed in the full set of ~15,000 inner Galaxy stars from APOGEE-1, and compare these patterns to extragalactic bulges and to evolutionary models that include both chemistry and kinematics for the stellar populations. We discuss implications for disentangling contributions from different bulge formation scenarios.

  6. A self-consistent field method for galactic dynamics

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars; Ostriker, Jeremiah P.

    1992-01-01

    The present study describes an algorithm for evolving collisionless stellar systems in order to investigate the evolution of systems with density profiles like the R exp 1/4 law, using only a few terms in the expansions. A good fit is obtained for a truncated isothermal distribution, which renders the method appropriate for galaxies with flat rotation curves. Calculations employing N of about 10 exp 6-7 are straightforward on existing supercomputers, making possible simulations having significantly smoother fields than with direct methods such as tree-codes. Orbits are found in a given static or time-dependent gravitational field; the potential, phi(r, t) is revised from the resultant density, rho(r, t). Possible scientific uses of this technique are discussed, including tidal perturbations of dwarf galaxies, the adiabatic growth of central masses in spheroidal galaxies, instabilities in realistic galaxy models, and secular processes in galactic evolution.

  7. Mass properties measurement system dynamics

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    The MPMS mechanism possess two revolute degrees-of-freedom and allows the user to measure the mass, center of gravity, and the inertia tensor of an unknown mass. The dynamics of the Mass Properties Measurement System (MPMS) from the Lagrangian approach to illustrate the dependency of the motion on the unknown parameters.

  8. Neutrino mass and the origin of galactic magnetic fields

    SciTech Connect

    Enqvist, K. ); Semikoz, V. IZMIRAN, Academy of Sciences, Troitsk 142092 ); Shukurov, A. Computing Center, Moscow University, Moscow 119899 ); Sokoloff, D. Isaac Newton Institute, Cambridge University, Cambridge CB3 0EH )

    1993-11-15

    We compare two constraints on the strength of the cosmological primordial magnetic field: the one following from the restrictions on the Dirac neutrino spin flip in the early Universe, and another one based on the galactic dynamo theory for the Milky Way (presuming that the seed magnetic field has a relic origin). Since the magnetic field facilitates transitions between left- and right-handed neutrino states, thereby affecting [sup 4]He production at primordial nucleosynthesis, we can obtain a guaranteed [ital upper] limit on the strength of the relic magnetic field in the protogalaxy, [ital B][sub [ital c

  9. 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

  10. Rapid and Bright Stellar-mass Binary Black Hole Mergers in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bartos, Imre

    2016-06-01

    Galactic nuclei are expected to harbor the densest population of stellar-mass black holes, accounting for as much as ∼ 2% of the mass of the nuclear stellar cluster. A significant fraction (∼ 30%) of these black holes can reside in binaries. We discuss the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. Binary black holes can migrate into and then rapidly merge within the disk. The binaries also accrete a significant amount of gas from the disk, potentially leading to detectable X-ray or gamma-ray emission.

  11. Determination of Black Hole Masses in Galactic Black Hole Binaries Using Scaling of Spectral and Variability Characteristics

    NASA Astrophysics Data System (ADS)

    Shaposhnikov, Nickolai; Titarchuk, Lev

    2009-07-01

    We present a study of correlations between X-ray spectral and timing properties observed from a number of Galactic black hole (BH) binaries during hard-soft state spectral evolution. We analyze 17 transition episodes from eight BH sources observed with Rossi X-Ray Timing Explorer. Our scaling technique for BH mass determination uses a correlation between the spectral index and quasi-periodic oscillation (QPO) frequency. In addition, we use a correlation between the index and the normalization of the disk "seed" component to cross-check the BH mass determination and estimate the distance to the source. While the index-QPO correlations for two given sources contain information on the ratio of the BH masses in those sources, the index-normalization correlations depend on the ratio of the BH masses and the distance square ratio. In fact, the index-normalization correlation also discloses the index-mass accretion rate saturation effect given that the normalization of disk "seed" photon supply is proportional to the disk mass accretion rate. We present arguments that this observationally established index saturation effect is a signature of the bulk motion (converging) flow onto a BH, which was early predicted by the dynamical Comptonization theory. We use GRO J1655 - 40 as a primary reference source for which the BH mass, distance, and inclination angle are evaluated by dynamical measurements with unprecedented precision among other Galactic BH sources. We apply our scaling technique to determine BH masses and distances for Cygnus X-1, GX 339 - 4, 4U 1543 - 47, XTE J1550 - 564, XTE J1650 - 500, H 1743 - 322, and XTE J1859 - 226. A good agreement of our results for sources with known values of BH masses and distance provides independent verification for our scaling technique.

  12. Masses of Black Holes in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    2003-01-01

    We present a progress report on a project whose goal is to improve both the precision and accuracy of reverberation-based black-hole masses. Reverberation masses appear to be accurate to a factor of about three, and the black-hole mass/bulge velocity dispersion (M-sigma) relationship appears to be the same in active and quiescent galaxies.

  13. Dynamics of massive black holes as a possible candidate of Galactic dark matter

    NASA Technical Reports Server (NTRS)

    Xu, Guohong; Ostriker, Jeremiah P.

    1994-01-01

    If the dark halo of the Galaxy is comprised of massive black holes (MBHs), then those within approximately 1 kpc will spiral to the center, where they will interact with one another, forming binaries which contract, owing to further dynamical friction, and then possibly merge to become more massive objects by emission of gravitational radiation. If successive mergers would invariably lead, as has been proposed by various authors, to the formation of a very massive nucleus of 10(exp 8) solar mass, then the idea of MBHs as a dark matter candidate could be excluded on observational grounds, since the observed limit (or value) for a Galactic central black hole is approximately 10(exp 6.5) solar mass. But, if successive mergers are delayed or prevented by other processes, such as the gravitational slingshot or rocket effect of gravitational radiation, then a large mass accumulation will not occur. In order to resolve this issue, we perform detailed N-body simulations using a modfied Aarseth code to explore the dynamical behavior of the MBHs, and we find that for a 'best estimate' model of the Galaxy a runaway does not occur. The code treates the MBHs as subject to the primary gravitational forces of one another and to the smooth stellar distribution, as well as the secondary perturbations in their orbits due to another and to the smooth stellar distribution, as well as the secondary perturbations in their orbits due to dynamical friction and gravitational radiation. Instead of a runaway, three-body interactions between hard binaries and single MBHs eject massive objects before accumulation of more than a few units, so that typically the center will contain zero, one, or two MBHs. We study how the situation depends in detail on the mass per MBH, the rotation of the halo, the mass distribution within the Galaxy, and other parameters. A runaway will most sensitively depend on the ratio of initial (spheroid/halo) central mass densities and secondarily on the typical values

  14. Variation of galactic cold gas reservoirs with stellar mass

    NASA Astrophysics Data System (ADS)

    Maddox, Natasha; Hess, Kelley M.; Obreschkow, Danail; Jarvis, M. J.; Blyth, S.-L.

    2015-02-01

    The stellar and neutral hydrogen (H I) mass functions at z ˜ 0 are fundamental benchmarks for current models of galaxy evolution. A natural extension of these benchmarks is the two-dimensional distribution of galaxies in the plane spanned by stellar and H I mass, which provides a more stringent test of simulations, as it requires the H I to be located in galaxies of the correct stellar mass. Combining H I data from the Arecibo Legacy Fast ALFA survey, with optical data from Sloan Digital Sky Survey, we find a distinct envelope in the H I-to-stellar mass distribution, corresponding to an upper limit in the H I fraction that varies monotonically over five orders of magnitude in stellar mass. This upper envelope in H I fraction does not favour the existence of a significant population of dark galaxies with large amounts of gas but no corresponding stellar population. The envelope shows a break at a stellar mass of ˜109 M⊙, which is not reproduced by modern models of galaxy populations tracing both stellar and gas masses. The discrepancy between observations and models suggests a mass dependence in gas storage and consumption missing in current galaxy evolution prescriptions. The break coincides with the transition from galaxies with predominantly irregular morphology at low masses to regular discs at high masses, as well as the transition from cold to hot accretion of gas in simulations.

  15. Star Formation and Dynamics in the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Mapelli, Michela; Gualandris, Alessia

    The centre of our Galaxy is one of the most studied and yet enigmatic places in the Universe. At a distance of about 8 kpc from our Sun, the Galactic centre (GC) is the ideal environment to study the extreme processes that take place in the vicinity of a supermassive black hole (SMBH). Despite the hostile environment, several tens of early-type stars populate the central parsec of our Galaxy. A fraction of them lie in a thin ring with mild eccentricity and inner radius ˜ 0.04 pc, while the S-stars, i.e. the ˜ 30 stars closest to the SMBH ( lesssim 0.04 pc), have randomly oriented and highly eccentric orbits. The formation of such early-type stars has been a puzzle for a long time: molecular clouds should be tidally disrupted by the SMBH before they can fragment into stars. We review the main scenarios proposed to explain the formation and the dynamical evolution of the early-type stars in the GC. In particular, we discuss the most popular in situ scenarios (accretion disc fragmentation and molecular cloud disruption) and migration scenarios (star cluster inspiral and Hills mechanism). We focus on the most pressing challenges that must be faced to shed light on the process of star formation in the vicinity of a SMBH.

  16. Gamma-ray evidence for a stellar-mass black hole near the Galactic center

    NASA Technical Reports Server (NTRS)

    Ramaty, Reuven; Lingenfelter, Richard E.

    1989-01-01

    An analysis of the time variability of the observed 511-keV line emission from the direction of the Galactic center and the correlation of its variations in the continuum emission above 511 keV from the same direction suggest the existence of a compact object at or near the Galactic center. A possible mechanism of the observed positron annihilation is consistent with a compact interaction region of the order of 10 to the 8th cm. A black hole of several hundred solar masses is favored as a candidate for this compact object; arguments in support of this suggestion are presented.

  17. A Galactic Weigh-in: Mass Models of SINGS Galaxies Using Chemo-spectrophotometric Galactic Evolution Models

    NASA Astrophysics Data System (ADS)

    de Denus-Baillargeon, M.-M.; Hernandez, O.; Boissier, S.; Amram, P.; Carignan, C.

    2013-08-01

    The baryonic mass-to-light ratio (Upsilonsstarf) used to perform the photometry-to-mass conversion has a tremendous influence on the measurement of the baryonic content and distribution as well as on the determination of the dark halo parameters. Since numerous clues hint at an inside-out formation process for galaxies, a radius-dependant Upsilonsstarf is needed to physically represent the radially varying stellar population. In this article, we use chemo-spectrophotometric galactic evolution (CSPE) models to determine Upsilonsstarf for a wide range of masses and sizes in the scenario of an inside-out formation process by gas accretion. We apply our method to a SINGS subsample of 10 spiral and dwarf galaxies with photometric coverage ranging from the UV to the mid-IR. The CSPE models prove to be a good tool for weighting the different photometric bands in order to obtain consistent stellar disk masses regardless of the spectral band used. On the other hand, we show that the color index versus Upsilonsstarf relation is an imperfect tool for assigning masses to young stellar populations because of the degeneracy affecting Upsilonsstarf in all bands at low color index. The disks resulting from our analysis are compatible with the maximum disk hypothesis provided that an adequate bulge/disk decomposition is performed and that the correction for the presence of a bar is not neglected since bars disturb the internal disk kinematics. Disk-mass models including Upsilonsstarf as a free parameter as well as models using our physically motivated, radially varying Upsilonsstarf are presented and discussed for each galaxy.

  18. A GALACTIC WEIGH-IN: MASS MODELS OF SINGS GALAXIES USING CHEMO-SPECTROPHOTOMETRIC GALACTIC EVOLUTION MODELS

    SciTech Connect

    De Denus-Baillargeon, M.-M.; Hernandez, O.; Carignan, C.; Boissier, S.; Amram, P.

    2013-08-20

    The baryonic mass-to-light ratio (Y{sub *}) used to perform the photometry-to-mass conversion has a tremendous influence on the measurement of the baryonic content and distribution as well as on the determination of the dark halo parameters. Since numerous clues hint at an inside-out formation process for galaxies, a radius-dependant Y{sub *} is needed to physically represent the radially varying stellar population. In this article, we use chemo-spectrophotometric galactic evolution (CSPE) models to determine Y{sub *} for a wide range of masses and sizes in the scenario of an inside-out formation process by gas accretion. We apply our method to a SINGS subsample of 10 spiral and dwarf galaxies with photometric coverage ranging from the UV to the mid-IR. The CSPE models prove to be a good tool for weighting the different photometric bands in order to obtain consistent stellar disk masses regardless of the spectral band used. On the other hand, we show that the color index versus Y{sub *} relation is an imperfect tool for assigning masses to young stellar populations because of the degeneracy affecting Y{sub *} in all bands at low color index. The disks resulting from our analysis are compatible with the maximum disk hypothesis provided that an adequate bulge/disk decomposition is performed and that the correction for the presence of a bar is not neglected since bars disturb the internal disk kinematics. Disk-mass models including Y{sub *} as a free parameter as well as models using our physically motivated, radially varying Y{sub *} are presented and discussed for each galaxy.

  19. Galactic rotation curves, the baryon-to-dark-halo-mass relation and space-time scale invariance

    NASA Astrophysics Data System (ADS)

    Wu, Xufen; Kroupa, Pavel

    2015-01-01

    Low-acceleration space-time scale invariant dynamics (SID) predicts two fundamental correlations known from observational galactic dynamics: the baryonic Tully-Fisher relation and a correlation between the observed mass discrepancy and acceleration (MDA) in the low-acceleration regime for disc galaxies. SID corresponds to the deep Modified Newtonian Dynamics limit. The MDA data emerging in cold/warm dark matter (C/WDM) cosmological simulations disagree significantly with the tight MDA correlation of the observed galaxies. Therefore, the most modern simulated disc galaxies, which are delicately selected to have a quiet merging history in a standard dark matter cosmological model, still do not represent the correct rotation curves. Also, the observed tight correlation contradicts the postulated stochastic formation of galaxies in low-mass dark matter haloes. Moreover, we find that SID predicts a baryonic to apparent virial halo (dark matter) mass relation which agrees well with the correlation deduced observationally assuming Newtonian dynamics to be valid, while the baryonic to halo mass relation predicted from CDM models does not. The distribution of the observed ratios of dark matter halo masses to baryonic masses may be empirical evidence for the external field effect, which is predicted in SID as a consequence of the forces acting between two galaxies depending on the position and mass of a third galaxy. Applying the external field effect, we predict the masses of galaxies in the proximity of the dwarf galaxies in the Miller et al. sample. Classical non-relativistic gravitational dynamics is thus best described as being Milgromian, rather than Newtonian.

  20. Dynamics with a Nonstandard Inertia-Acceleration Relation: An Alternative to Dark Matter in Galactic Systems

    NASA Astrophysics Data System (ADS)

    Milgrom, M.

    1994-02-01

    We investigate particle dynamics that is governed by a nonstandard kinetic action of a special form. We are guided by a phenomenological scheme-the modified dynamics (MOND)-that imputes the mass discrepancy, observed in galactic systems, not to the presence of dark matter, but to a departure from Newtonian dynamics below a certain scale of accelerations, a0. The particle's equation of motion in a potential φ is derived from an action, S, of the form S ~ Sk[r(t), a0] - ∫ φ dt. The limit a0 --> 0 corresponds to Newtonian dynamics, and there the kinetic action Sk must take the standard form. In the opposite limit, a0 --> ∞ we require Sk --> 0-and more specifically, for circular orbits Sk ~ a-10-in order to attain the phenomenological success of MOND. Galilei-invariant such theories must be strongly nonlocal. This is a blessing, as such theories need not suffer from the illnesses that are endemic to higher-derivative theories. We comment on the possibility that such a modified law of motion is an effective theory resulting from the elimination of degrees of freedom pertaining to the universe at large (the near equality a0 ≍ cH0 being a trace of that connection). We derive a general virial relation for bounded trajectories. Exact solutions are obtained for circular orbits, which pertain to rotation curves of disk galaxies. We also explore, in passing, theories that depart from the conventional Newtonian dynamics for very low frequencies.

  1. The relationship between the galactic matter distribution, cosmic ray dynamics, and gamma ray production

    NASA Technical Reports Server (NTRS)

    Kniffen, D. A.; Fichtel, C. E.; Thompson, D. J.

    1976-01-01

    Theoretical considerations and analysis of the results of gamma ray astronomy suggest that the galactic cosmic rays are dynamically coupled to the interstellar matter through the magnetic fields, and hence the cosmic ray density should be enhanced where the matter density is greatest on the scale of galactic arms. This concept has been explored in a galactic model using recent 21 cm radio observations of the neutral hydrogen and 2.6 mm observations of carbon monoxide, which is considered to be a tracer of molecular hydrogen. The model assumes: (1) cosmic rays are galactic and not universal; (2) on the scale of galactic arms, the cosmic ray column (surface) density is proportional to the total interstellar gas column density; (3) the cosmic ray scale height is significantly larger than the scale height of the matter; and (4) ours is a spiral galaxy characterized by an arm to interarm density ratio of about 3:1.

  2. Assembling the Largest, Most Distant Sample of Halo Wide Binaries for Galactic Structure and Dynamics

    NASA Astrophysics Data System (ADS)

    Coronado, J.; Chanamé, J.

    2015-10-01

    Samples of wide binaries (agtrsim \\ 100\\ AU) are a gold mine for Galactic studies. They have been used on a large list of applications in a diversity of fields. In the dynamical arena, wide binaries provided the first meaningful constraints on the mass and nature of disk dark matter and, more recently, they were used to close the remaining parameter space of MACHO-like halo dark matter not accessible to the micro-lensing campaigns. All these applications were possible when samples of these objects became large enough to not be dominated by random, chance alignments of two unrelated stars projected on the sky. Nevertheless, still today the largest available sample of the particularly valuable halo wide binaries free from selection biases, contains not much more than 100 systems, and conclusions on dark matter are very sensitive to this fact.

  3. AGE AND MASS SEGREGATION OF MULTIPLE STELLAR POPULATIONS IN GALACTIC NUCLEI AND THEIR OBSERVATIONAL SIGNATURES

    SciTech Connect

    Perets, Hagai B.; Mastrobuono-Battisti, Alessandra

    2014-04-01

    Nuclear stellar clusters (NSCs) are known to exist around massive black holes in galactic nuclei. They are thought to have formed through in situ star formation following gas inflow to the nucleus of the galaxy and/or through the infall of multiple stellar clusters. Here we study the latter, and explore the composite structure of the NSC and its relation to the various stellar populations originating from its progenitor infalling clusters. We use N-body simulations of cluster infalls and show that this scenario may produce observational signatures in the form of age segregation: the distribution of the stellar properties (e.g., stellar age and/or metallicity) in the NSCs reflects the infall history of the different clusters. The stellar populations of clusters, infalling at different times (dynamical ages), are differentially segregated in the NSC and are not fully mixed even after a few gigayears of evolution. Moreover, the radial properties of stellar populations in the progenitor cluster are mapped to their radial distribution in the final NSC, potentially leading to efficient mass segregation in NSCs, even those where relaxation times are longer than a Hubble time. Finally, the overall structures of the stellar populations present non-spherical configurations and show significant cluster to cluster population differences.

  4. Dynamics of Variable Mass Systems

    NASA Technical Reports Server (NTRS)

    Eke, Fidelis O.

    1998-01-01

    This report presents the results of an investigation of the effects of mass loss on the attitude behavior of spinning bodies in flight. The principal goal is to determine whether there are circumstances under which the motion of variable mass systems can become unstable in the sense that their transverse angular velocities become unbounded. Obviously, results from a study of this kind would find immediate application in the aerospace field. The first part of this study features a complete and mathematically rigorous derivation of a set of equations that govern both the translational and rotational motions of general variable mass systems. The remainder of the study is then devoted to the application of the equations obtained to a systematic investigation of the effect of various mass loss scenarios on the dynamics of increasingly complex models of variable mass systems. It is found that mass loss can have a major impact on the dynamics of mechanical systems, including a possible change in the systems stability picture. Factors such as nozzle geometry, combustion chamber geometry, propellant's initial shape, size and relative mass, and propellant location can all have important influences on the system's dynamic behavior. The relative importance of these parameters on-system motion are quantified in a way that is useful for design purposes.

  5. Constraining absolute neutrino masses via detection of galactic supernova neutrinos at JUNO

    SciTech Connect

    Lu, Jia-Shu; Cao, Jun; Li, Yu-Feng; Zhou, Shun

    2015-05-26

    A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses m{sub ν} via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be m{sub ν}<(0.83±0.24) eV at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is m{sub ν}<(0.94±0.28) eV at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted.

  6. Constraining absolute neutrino masses via detection of galactic supernova neutrinos at JUNO

    NASA Astrophysics Data System (ADS)

    Lu, Jia-Shu; Cao, Jun; Li, Yu-Feng; Zhou, Shun

    2015-05-01

    A high-statistics measurement of the neutrinos from a galactic core-collapse supernova is extremely important for understanding the explosion mechanism, and studying the intrinsic properties of neutrinos themselves. In this paper, we explore the possibility to constrain the absolute scale of neutrino masses mν via the detection of galactic supernova neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO) with a 20 kiloton liquid-scintillator detector. In assumption of a nearly-degenerate neutrino mass spectrum and a normal mass ordering, the upper bound on the absolute neutrino mass is found to be mν < (0.83 ± 0.24) eV at the 95% confidence level for a typical galactic supernova at a distance of 10 kpc, where the mean value and standard deviation are shown to account for statistical fluctuations. For comparison, we find that the bound in the Super-Kamiokande experiment is mν < (0.94 ± 0.28) eV at the same confidence level. However, the upper bound will be relaxed when the model parameters characterizing the time structure of supernova neutrino fluxes are not exactly known, and when the neutrino mass ordering is inverted.

  7. Large-scale gas dynamical processes affecting the origin and evolution of gaseous galactic halos

    NASA Technical Reports Server (NTRS)

    Shapiro, Paul R.

    1991-01-01

    Observations of galactic halo gas are consistent with an interpretation in terms of the galactic fountain model in which supernova heated gas in the galactic disk escapes into the halo, radiatively cools and forms clouds which fall back to the disk. The results of a new study of several large-scale gas dynamical effects which are expected to occur in such a model for the origin and evolution of galactic halo gas will be summarized, including the following: (1) nonequilibrium absorption line and emission spectrum diagnostics for radiatively cooling halo gas in our own galaxy, as well the implications of such absorption line diagnostics for the origin of quasar absorption lines in galactic halo clouds of high redshift galaxies; (2) numerical MHD simulations and analytical analysis of large-scale explosions ad superbubbles in the galactic disk and halo; (3) numerical MHD simulations of halo cloud formation by thermal instability, with and without magnetic field; and (4) the effect of the galactic fountain on the galactic dynamo.

  8. The universal relation of galactic chemical evolution: the origin of the mass-metallicity relation

    SciTech Connect

    Zahid, H. Jabran; Dima, Gabriel I.; Kudritzki, Rolf-Peter; Kewley, Lisa J.; Geller, Margaret J.; Hwang, Ho Seong; Silverman, John D.; Kashino, Daichi

    2014-08-20

    We examine the mass-metallicity relation for z ≲ 1.6. The mass-metallicity relation follows a steep slope with a turnover, or 'knee', at stellar masses around 10{sup 10} M {sub ☉}. At stellar masses higher than the characteristic turnover mass, the mass-metallicity relation flattens as metallicities begin to saturate. We show that the redshift evolution of the mass-metallicity relation depends only on the evolution of the characteristic turnover mass. The relationship between metallicity and the stellar mass normalized to the characteristic turnover mass is independent of redshift. We find that the redshift-independent slope of the mass-metallicity relation is set by the slope of the relationship between gas mass and stellar mass. The turnover in the mass-metallicity relation occurs when the gas-phase oxygen abundance is high enough that the amount of oxygen locked up in low-mass stars is an appreciable fraction of the amount of oxygen produced by massive stars. The characteristic turnover mass is the stellar mass, where the stellar-to-gas mass ratio is unity. Numerical modeling suggests that the relationship between metallicity and the stellar-to-gas mass ratio is a redshift-independent, universal relationship followed by all galaxies as they evolve. The mass-metallicity relation originates from this more fundamental universal relationship between metallicity and the stellar-to-gas mass ratio. We test the validity of this universal metallicity relation in local galaxies where stellar mass, metallicity, and gas mass measurements are available. The data are consistent with a universal metallicity relation. We derive an equation for estimating the hydrogen gas mass from measurements of stellar mass and metallicity valid for z ≲ 1.6 and predict the cosmological evolution of galactic gas masses.

  9. Spectral Analysis of Biodiversity Cycles and Galactic Dynamics

    NASA Astrophysics Data System (ADS)

    Lieberman, Bruce; Melott, Adrian

    2007-04-01

    We have analyzed the power spectral and phase relationships of fluctuations in biodiversity, species origination, extinction rate, and motion of the solar system normal to the galactic plane over the last ˜500 My. The period of the dominant spectral component is the same 62 My for all these except extinction. It is also the same as the rate of gene duplication events (as determined by Ding et al.), suggesting some sort of causal relationship. The spectra suggest that the biodiversity cycle is more closely related to origination rates than extinction rates. Biodiversity and solar motion are offset by π, with gene duplication and origination lagging and leading biodiversity by ˜2 radians. A picture emerges consistent with a rising rate of mutation and stress on the biosphere as the solar system moves to galactic north, possibly exposed to higher cosmic rays from a galactic bow shock, as proposed elsewhere, and increasing species origination as it returns to the magnetic shielding of the galactic disk.

  10. Kinematics and dynamics of molecular gas in galactic centers

    NASA Astrophysics Data System (ADS)

    Sakamoto, K.

    2014-05-01

    The central molecular zone (CMZ) in the central half kpc of the Milky Way is a massive concentration of molecular gas in the center of a barred spiral galaxy. Current and past activities in the Galactic center include the formation of massive stars/clusters, AGN feeding, and feedback. At the same time, observations of molecular gas in external galaxies show that many disk galaxies have similar condensations of molecular gas in their central kpc or so. They also have CMZs, or nuclear molecular rings or concentrations in more common terms among extragalactic observers. The formation of the CMZs are often, but not always, related to stellar bars. The centers of nearby galaxies can provide valuable information on the general properties of galactic centers and CMZs through comparative studies of multiple galactic centers of different characteristics from various viewing angles. Linear resolutions achieved toward nearby extragalactic CMZs with modern radio interferometers are now comparable to those achieved toward the Galactic CMZ with small single-dish telescopes. I review and present work on the formation mechanism and properties of the CMZs in external galaxies with some comparisons with the CMZ of our Galaxy.

  11. Constraining the mass of Galactic black hole GX 339-4

    NASA Astrophysics Data System (ADS)

    Sreehari, H.; Iyer, N.; Nandi, Anuj

    Observations of Galactic black hole candidates during their outburst phases have revealed Quasi-Periodic Oscillations (QPOs) and their dependence on the spectral parameters. We used the 2010 outburst data of GX 339-4 from Rossi X-ray Timing Explorer (RXTE) and modeled it based on evolution of QPO frequencies and spectro-temporal correlation to constrain the mass of the compact object.

  12. Tracing the Dynamics of the Galactic Disk with SIM PlanetQuest

    NASA Astrophysics Data System (ADS)

    Majewski, S. R.; Frinchaboy, P. M.; Patterson, R. J.

    2005-12-01

    Establishing the rotation curve of the Milky Way on an absolute scale is one of the fundamental contributions that SIM PlanetQuest can make to understanding the Galaxy and its mass distribution. As preparatory work for the ``Taking Measure of the Milky Way'' SIM Key Project, we have undertaken a systematic spectroscopic survey of open star clusters which can serve as tracers of Galactic disk dynamics. We report progress on our inital sample of over 100 clusters for which the Hydra multifiber spectrographs on the WIYN and Blanco telescopes have delivered ˜ 1 km s-1 radial velocities (RVs) of many dozens of stars per cluster. The RVs are used to derive cluster membership for individual stars in these crowded fields and to derive a bulk cluster RV. The clusters selected for study have a broad spatial distribution in order to be sensitive to the disk velocity field in all Galactic quadrants and across a Galactocentric radius range as much as 2.5 kpc from the solar circle. These clusters already have published ages, distances, and metallicity estimates, but these can be improved once chemical abundances on a uniform scale are measured from the homogenous spectra, and once SIM parallaxes are obtained for member stars. The new RVs combined with Tycho proper motions (for bright members in each cluster) allow an initial investigation of the local disk dynamics, but this will be substantially improved once SIM proper motions are obtained for these and even more distant open clusters. We acknowledge funding by NASA/JPL contract 1228235, NSF grant AST-0307851, and the F.H. Levinson Fund of the Peninsula Community Foundation. PMF is supported by a NASA-GSRP, a UVa Faculty Senate Dissertation-Year Fellowship, and the Virginia Space Grant Consortium.

  13. Binary systems, star clusters and the Galactic-field population. Applied stellar dynamics

    NASA Astrophysics Data System (ADS)

    Kroupa, Pavel

    2002-01-01

    This book contains the results of recent theoretical work on the evolution of primordial binary systems in young star clusters, their effect on the evolution of their host clusters, implications for the distribution of young stars in the Milky Way, and the formation of bound star clusters. This work shows that if the Galactic-field binary population is a dynamically evolved version of the Taurus-Auriga pre-main sequence population, then most stars form in clusters with typically a few hundred binaries within a radius of about 0.5-1 pc. The results also suggest that the population I primordial binary-star orbital-parameter distribution functions may be universal, much like the initial mass function. Most solar-like planetary systems can survive in such clusters. The work presented here also establishes that most observed triple and quadruple systems must be primordial, but that α Cen A/B-Proxima Cen-like systems can form in clusters through dynamical capture. Precise N-body calculations using Aarseth's N-body codes of clusters containing up to 104 stars are used to create an extensive young-cluster library. These data demonstrate that the primordial binary systems are disrupted on a crossing-time scale, and that the truncation of the surviving period distribution measures the maximum concentration the cluster ever experienced. The N-body calculations demonstrate that Galactic star clusters form readily as nuclei of expanding OB associations despite a star-formation efficiency of typically 30 per cent and gas-expulsion over a time-span shorter than the cluster crossing time.

  14. Galactic Star Cluster mass evolution. High performance star by star simulations. Observations vs. modeling.

    NASA Astrophysics Data System (ADS)

    Berczik, Peter; Just, Andreas; Ernst, Andreas; Spurzem, Rainer

    2015-08-01

    We carry out the large set of Galactic Star Cluster simulations (from 1e2 up to 5e5 Msol initial masses) using our high performance parallel direct N-body code phi-GRAPE+GPU with the maximum possible numerical resolution (one particle one star) on the largest astrophysical GPU clusters (in Germany and China). Our main goal was to investigate the cluster initial volume "filling" factor to the process of the cluster mass loss as well us the cluster whole lifetime. We also investigate the evolution of the present day Cluster Mass Function in solar cylinder depending on the initial parameters of the star formation, Initial Cluster Mass Function and the star clusters masses and initial "filling" factors.

  15. THE ORIGIN OF BLACK HOLE SPIN IN GALACTIC LOW-MASS X-RAY BINARIES

    SciTech Connect

    Fragos, T.; McClintock, J. E.

    2015-02-10

    Galactic field black hole (BH) low-mass X-ray binaries (LMXBs) are believed to form in situ via the evolution of isolated binaries. In the standard formation channel, these systems survived a common envelope phase, after which the remaining helium core of the primary star and the subsequently formed BH are not expected to be highly spinning. However, the measured spins of BHs in LMXBs cover the whole range of spin parameters. We propose here that the BH spin in LMXBs is acquired through accretion onto the BH after its formation. In order to test this hypothesis, we calculated extensive grids of detailed binary mass-transfer sequences. For each sequence, we examined whether, at any point in time, the calculated binary properties are in agreement with their observationally inferred counterparts of 16 Galactic LMXBs. The ''successful'' sequences give estimates of the mass that the BH has accreted since the onset of Roche-Lobe overflow. We find that in all Galactic LMXBs with measured BH spin, the origin of the spin can be accounted for by the accreted matter, and we make predictions about the maximum BH spin in LMXBs where no measurement is yet available. Furthermore, we derive limits on the maximum spin that any BH can have depending on current properties of the binary it resides in. Finally we discuss the implication that our findings have on the BH birth-mass distribution, which is shifted by ∼1.5 M {sub ☉} toward lower masses, compared to the currently observed one.

  16. THE STELLAR INITIAL MASS FUNCTION OF ULTRA-FAINT DWARF GALAXIES: EVIDENCE FOR IMF VARIATIONS WITH GALACTIC ENVIRONMENT

    SciTech Connect

    Geha, Marla; Brown, Thomas M.; Tumlinson, Jason; Kalirai, Jason S.; Avila, Roberto J.; Ferguson, Henry C.; Simon, Joshua D.; Kirby, Evan N.; VandenBerg, Don A.; Munoz, Ricardo R.; Guhathakurta, Puragra E-mail: tbrown@stsci.edu

    2013-07-01

    We present constraints on the stellar initial mass function (IMF) in two ultra-faint dwarf (UFD) galaxies, Hercules and Leo IV, based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. The Hercules and Leo IV galaxies are extremely low luminosity (M{sub V} = -6.2, -5.5), metal-poor (([Fe/H]) = -2.4, -2.5) systems that have old stellar populations (>11 Gyr). Because they have long relaxation times, we can directly measure the low-mass stellar IMF by counting stars below the main-sequence turnoff without correcting for dynamical evolution. Over the stellar mass range probed by our data, 0.52-0.77 M{sub Sun }, the IMF is best fit by a power-law slope of {alpha}= 1.2{sub -0.5}{sup +0.4} for Hercules and {alpha} = 1.3 {+-} 0.8 for Leo IV. For Hercules, the IMF slope is more shallow than a Salpeter ({alpha} = 2.35) IMF at the 5.8{sigma} level, and a Kroupa ({alpha} = 2.3 above 0.5 M{sub Sun }) IMF slope at 5.4{sigma} level. We simultaneously fit for the binary fraction, f{sub binary}, finding f{sub binary}= 0.47{sup +0.16}{sub -0.14} for Hercules, and 0.47{sup +0.37}{sub -0.17} for Leo IV. The UFD binary fractions are consistent with that inferred for Milky Way stars in the same mass range, despite very different metallicities. In contrast, the IMF slopes in the UFDs are shallower than other galactic environments. In the mass range 0.5-0.8 M{sub Sun }, we see a trend across the handful of galaxies with directly measured IMFs such that the power-law slopes become shallower (more bottom-light) with decreasing galactic velocity dispersion and metallicity. This trend is qualitatively consistent with results in elliptical galaxies inferred via indirect methods and is direct evidence for IMF variations with galactic environment.

  17. Observational dynamics of low-mass stellar systems

    NASA Astrophysics Data System (ADS)

    Frank, M. J.

    The last fifteen years have seen the discovery of new types of low-mass stellar systems that bridge the gap between the once well-separated regimes of galaxies and of star clusters. Whether such objects are considered galaxies depends also on the definition of the term ``galaxy'', and several possible criteria are based on their internal dynamics (e.g. the common concept that galaxies contain dark matter). Moreover, studying the internal dynamics of low-mass stellar systems may also help understand their origin and evolutionary history. The focus of this paper is on two classes of stellar systems at the interface between star clusters and dwarf galaxies: ultra-compact dwarf galaxies (UCDs) and diffuse Galactic globular clusters (GCs). A review of our current knowledge on the properties of UCDs is provided and dynamical considerations applying to diffuse GCs are introduced. In the following, recent observational results on the internal dynamics of individual UCDs and diffuse Galactic globular clusters are presented. Partly based on observations obtained at the European Southern Observatory, Chile (Observing Programmes 078.B-0496(B) and 081.B-0282). Doctoral Thesis Award Lecture 2013

  18. The Masses of the B Stars in the High Galactic Latitude Eclipsing Binary IT Librae

    NASA Astrophysics Data System (ADS)

    Martin, John C.

    2003-01-01

    A number of blue stars that appear to be similar to Population I B stars in the star-forming regions of the Galactic disk are found more than 1 kpc from the Galactic plane. Uncertainties about the true distances and masses of these high-latitude B stars have fueled a debate as to their origin and evolutionary status. The eclipsing binary IT Lib is composed of two B stars, is approximately 1 kpc above the Galactic plane, and is moving back toward the plane. Observations of the light and velocity curves presented here lead to the conclusion that the B stars in this system are massive young main-sequence stars. While there are several possible explanations, it appears most plausible that the IT Lib system formed in the disk about 30 million years ago and was ejected on a trajectory taking it to its present position. Based on observations made at the 2.1 m Otto Struve Telescope of McDonald Observatory operated by the University of Texas at Austin and also at the 2.1 m telescope at Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under cooperative agreement with the National Science Foundation.

  19. Energy Spectra and Mass Composition of Cosmic Rays in the Fractal-Like Galactic Medium

    NASA Astrophysics Data System (ADS)

    Lagutin, A. A.; Tyumentsev, A. G.; Yushkov, A. V.

    We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by galactic sources. The fractional diffusion equation proposed in our recent papers is used to describe the cosmic rays propagation in interstellar medium. We show that in the framework of this approach it is possible to explain the locally observed basic features of the cosmic rays in the energy region 1010 ÷ 1020 eV: difference between spectral exponents of protons and other nuclei, mass composition variation, "knee" problem, flattening of the primary spectrum for E ≥ 1018 ÷ 1019 eV.

  20. DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE

    SciTech Connect

    McDonald, I.; Zijlstra, A. A.; Boyer, M. L.; Van Loon, J. Th.

    2011-04-01

    Dust production among post-main-sequence stars is investigated in the Galactic globular cluster 47 Tucanae (NGC 104) based on infrared photometry and spectroscopy. We identify metallic iron grains as the probable dominant opacity source in these winds. Typical evolutionary timescales of asymptotic giant branch stars suggest the mass-loss rates we report are too high. We suggest that this is because the iron grains are small or elongated and/or that iron condenses more efficiently than at solar metallicity. Comparison to other works suggests metallic iron is observed to be more prevalent toward lower metallicities. The reasons for this are explored, but remain unclear. Meanwhile, the luminosity at which dusty mass loss begins is largely invariant with metallicity, but its presence correlates strongly with long-period variability. This suggests that the winds of low-mass stars have a significant driver that is not radiation pressure, but may be acoustic driving by pulsations.

  1. A polarimetric method for measuring black hole masses in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Piotrovich, M. Yu.; Gnedin, Yu. N.; Silant'ev, N. A.; Natsvlishvili, T. M.; Buliga, S. D.

    2015-11-01

    The structure of the broad emission line region (BLR) in active galactic nuclei (AGN) remains unclear. We test in this paper a flattened configuration model for BLR. The virial theorem, by taking into account the disc shape of BLR, allows us to get a direct connection between the mass of a supermassive black hole (SMBH) and the inclination angle of the accretion flow. The inclination angle itself is derived from the spectropolarimetric data on broad emission lines using the theory for the generation of polarized radiation developed by Sobolev and Chandrasekhar. As the result, the new estimates of SMBH masses in AGN with measured polarization of BLR are presented. It is crucial that the polarimetric data allow also to determine the value of the virial coefficient that is essential for determining SMBH masses.

  2. THE LUMINOSITY AND MASS FUNCTIONS OF LOW-MASS STARS IN THE GALACTIC DISK. II. THE FIELD

    SciTech Connect

    Bochanski, John J.; Hawley, Suzanne L.; Ivezic, Zeljko; Covey, Kevin R.; West, Andrew A.; Reid, I. Neill; Golimowski, David A.

    2010-06-15

    We report on new measurements of the luminosity function (LF) and mass function (MF) of field low-mass dwarfs derived from Sloan Digital Sky Survey Data Release 6 photometry. The analysis incorporates {approx}15 million low-mass stars (0.1 M{sub sun}< M < 0.8 M{sub sun}), spread over 8400 deg{sup 2}. Stellar distances are estimated using new photometric parallax relations, constructed from ugriz photometry of nearby low-mass stars with trigonometric parallaxes. We use a technique that simultaneously measures Galactic structure and the stellar LF from 7 < M{sub r} < 16. We compare the LF to previous studies and convert to an MF using the mass-luminosity relations of Delfosse et al. The system MF, measured over -1.0< log M/M{sub sun} <-0.1, is well described by a lognormal distribution with M{sub o} = 0.25 M{sub sun}. We stress that our results should not be extrapolated to other mass regimes. Our work generally agrees with prior low-mass stellar MFs and places strong constraints on future theoretical star formation studies.

  3. MOA-2011-BLG-028Lb: A Neptune-mass Microlensing Planet in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    Skowron, J.; Udalski, A.; Poleski, R.; Kozłowski, S.; Szymański, M. K.; Wyrzykowski, Ł.; Ulaczyk, K.; Pietrukowicz, P.; Pietrzyński, G.; Soszyński, I.; The OGLE Collaboration; Abe, F.; Bennett, D. P.; Bhattacharya, A.; Bond, I. A.; Freeman, M.; Fukui, A.; Hirao, Y.; Itow, Y.; Koshimoto, N.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Rattenbury, N.; Saito, To.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yonehara, A.; The MOA Collaboration; Dominik, M.; Jørgensen, U. G.; Bozza, V.; Harpsøe, K.; Hundertmark, M.; Skottfelt, J.; The MiNDSTEp Collaboration

    2016-03-01

    We present the discovery of a Neptune-mass planet orbiting a 0.8+/- 0.3{M}ȯ star in the Galactic bulge. The planet manifested itself during the microlensing event MOA-2011-BLG-028/OGLE-2011-BLG-0203 as a low-mass companion to the lens star. The analysis of the light curve provides the measurement of the mass ratio (1.2+/- 0.2)× {10}-4, which indicates that the mass of the planet is 12–60 Earth masses. The lensing system is located at 7.3 ± 0.7 kpc away from the Earth near the direction of Baade’s Window. The projected separation of the planet at the time of the microlensing event was 3.1–5.2 au. Although the microlens parallax effect is not detected in the light curve of this event, preventing the actual mass measurement, the uncertainties of mass and distance estimation are narrowed by the measurement of the source star proper motion on the OGLE-III images spanning eight years, and by the low amount of blended light seen, proving that the host star cannot be too bright and massive. We also discuss the inclusion of undetected parallax and orbital motion effects into the models and their influence onto the final physical parameters estimates. Based on observations obtained with the 1.3 m Warsaw telescope at the Las Campanas Observatory operated by the Carnegie Institution of Washington.

  4. Dynamics and X-Ray Emission of a Galactic Superwind Interacting with Disk and Halo Gas

    NASA Astrophysics Data System (ADS)

    Suchkov, A. A.; Balsara, D. S.; Heckman, T. M.; Leitherer, C.

    1993-12-01

    There is a general agreement that the conspicuous extranuclear x-ray, optical-line, and radio-continuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyse the interaction of the wind with a two-component disk--halo ambient interstellar medium. This two-component representation is argued to be crucial for adequate modelling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the x-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex `filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions related to the origin and development of the `filaments'. The `filament' parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A ``mild'' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk

  5. A review of action estimation methods for galactic dynamics

    NASA Astrophysics Data System (ADS)

    Sanders, Jason L.; Binney, James

    2016-04-01

    We review the available methods for estimating actions, angles and frequencies of orbits in both axisymmetric and triaxial potentials. The methods are separated into two classes. Unless an orbit has been trapped by a resonance, convergent, or iterative, methods are able to recover the actions to arbitrarily high accuracy given sufficient computing time. Faster non-convergent methods rely on the potential being sufficiently close to a separable potential, and the accuracy of the action estimate cannot be improved through further computation. We critically compare the accuracy of the methods and the required computation time for a range of orbits in an axisymmetric multicomponent Galactic potential. We introduce a new method for estimating actions that builds on the adiabatic approximation of Schönrich & Binney and discuss the accuracy required for the actions, angles and frequencies using suitable distribution functions for the thin and thick discs, the stellar halo and a star stream. We conclude that for studies of the disc and smooth halo component of the Milky Way, the most suitable compromise between speed and accuracy is the Stäckel Fudge, whilst when studying streams the non-convergent methods do not offer sufficient accuracy and the most suitable method is computing the actions from an orbit integration via a generating function. All the software used in this study can be downloaded from https://github.com/jls713/tact.

  6. The effect of active galactic nuclei feedback on the halo mass function

    NASA Astrophysics Data System (ADS)

    Cui, Weiguang; Borgani, Stefano; Murante, Giuseppe

    2014-06-01

    We investigate baryon effects on the halo mass function (HMF), with emphasis on the role played by active galactic nuclei (AGN) feedback. Haloes are identified with both friends-of-friends (FoF) and spherical overdensity (SO) algorithms. We embed the standard SO algorithm into a memory-controlled frame program and present the Python spherIcAl Overdensity code - PIAO (Chinese character: ). For both FoF and SO haloes, the effect of AGN feedback is that of suppressing the HMFs to a level even below that of dark matter (DM) simulations. The ratio between the HMFs in the AGN and in the DM simulations is ˜0.8 at overdensity Δc = 500, a difference that increases at higher overdensity Δc = 2500, with no significant redshift and mass dependence. A decrease of the halo masses ratio with respect to the DM case induces the decrease of the HMF in the AGN simulation. The shallower inner density profiles of haloes in the AGN simulation witnesses that mass reduction is induced by the sudden displacement of gas induced by thermal AGN feedback. We provide fitting functions to describe halo mass variations at different overdensities, which can recover the HMFs with a residual random scatter ≲5 per cent for halo masses larger than 1013 h-1 M⊙.

  7. X-ray induced stellar mass loss near active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Voit, G. Mark; Shull, J. Michael

    1988-01-01

    The effects of UV and X-ray radiation on stars in active galactic nuclei (AGN) are critically evaluated. Mass loss rates in X-ray-induced winds are evaluated for realistic red giant models, and the effects of the ablation of stellar envelopes by radiation pressure are considered. The importance of X-ray-induced mass loss in the standard quasar model is evaluated and whether it can provide a source of accretion fuel or emission-line clouds is discussed. It is concluded that thermal winds driven by X-ray heating are a minor total supply of mass to AGN, but that thermal plus line-driven winds and stellar ablation may increase the mass loss and improve the chances for supplying a fraction of the necessary mass supply to the central object. It is speculated that when steady winds are inefficient, complex time-dependent processes due to X-ray energy injection deep into a stellar atmosphere could still release significant mass from stars.

  8. The delayed contribution of low and intermediate mass stars to chemical galactic enrichment: An analytical approach

    NASA Astrophysics Data System (ADS)

    Franco, I.; Carigi, L.

    2008-10-01

    We find a new analytical solution for the chemical evolution equations, taking into account the delayed contribution of all low and intermediate mass stars (LIMS) as one representative star that enriches the interstellar medium. This solution is built only for star formation rate proportional to the gas mass in a closed box model. We obtain increasing C/O and N/O ratios with increasing O/H, behavior impossible to match with the Instantaneous Recycling Approximation (IRA). Our results, obtained by two analytical equations, are very similar to those found by numerical models that consider the lifetimes of each star. This delayed model reproduces successfully the evolution of the C/O-O/H and Y - O relations in the solar vicinity. This analytical approximation is a useful tool to study the chemical evolution of elements produced by LIMS when a galactic chemical evolutionary code is not available.

  9. Low-mass Active Galactic Nuclei with Rapid X-Ray Variability

    NASA Astrophysics Data System (ADS)

    Ho, Luis C.; Kim, Minjin

    2016-04-01

    We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad Hα emission in all the sources, allowing us to estimate robust virial BH masses and Eddington ratios for this unique sample. We confirm that the sample contains low-mass BHs accreting at high rates: the median MBH = 1.2 × 106 M⊙ and median Lbol/LEdd = 0.44. The sample follows the MBH–σ* relation, within the considerable scatter typical of pseudobulges, the probable hosts of these low-mass AGNs. Various lines of evidence suggest that ongoing star formation is prevalent in these systems. We propose a new strategy to estimate star formation rates in AGNs hosted by low-mass, low-metallicity galaxies, based on modification of an existing method using the strength of [O ii] λ3727, [O iii] λ5007, and X-rays.

  10. Mass extinctions, galactic orbits in the solar neighborhood and the Sun: a connection?

    NASA Astrophysics Data System (ADS)

    Porto de Mello, G. F.; Dias, W. S.; Lépine, J. R. D.; Lorenzo-Oliveira, D.; Siqueira, R. K.

    2014-10-01

    The orbits of the stars in the disk of the Galaxy, and their passages through the Galactic spiral arms, are a rarely mentioned factor of biosphere stability which might be important for long-term planetary climate evolution, with a possible bearing on mass extinctions. The Sun lies very near the co-rotation radius, where stars revolve around the Galaxy in the same period as the density wave perturbations of the spiral arms. Conventional wisdom generally considers that this status makes for few passages through the spiral arms. Controversy still surrounds whether time spent inside or around spiral arms is dangerous to biospheres and conducive to mass extinctions. Possible threats include giant molecular clouds disturbing the Oort comet cloud and provoking heavy bombardment; a higher exposure to cosmic rays near star forming regions triggering increased cloudiness in Earth's atmosphere and ice ages; and the destruction of Earth's ozone layer posed by supernova explosions. We present detailed calculations of the history of spiral arm passages for all 212 solar-type stars nearer than 20 parsecs, including the total time spent inside the spiral arms in the last 500 Myr, when the spiral arm position can be traced with good accuracy. We found that there is a large diversity of stellar orbits in the solar neighborhood, and the time fraction spent inside spiral arms can vary from a few percent to nearly half the time. The Sun, despite its proximity to the galactic co-rotation radius, has exceptionally low eccentricity and a low vertical velocity component, and therefore spends 30% of its lifetime crossing the spiral arms, more than most nearby stars. We discuss the possible implications of this fact to the long-term habitability of the Earth, and possible correlations of the Sun's passage through the spiral arms with the five great mass extinctions of the Earth's biosphere from the Late Ordovician to the Cretaceous-Tertiary.

  11. DUST PRODUCTION AND MASS LOSS IN THE GALACTIC GLOBULAR CLUSTER NGC 362

    SciTech Connect

    Boyer, Martha L.; Gordon, Karl D.; Meixner, Margaret; Sewilo, Marta; Shiao, Bernie; Whitney, Barbara; McDonald, Iain; Van Loon, Jacco Th.; Oliveira, Joana M.; Babler, Brian; Bracker, Steve; Meade, Marilyn; Block, Miwa; Engelbracht, Charles; Misselt, Karl; Hora, Joe; Indebetouw, Remy

    2009-11-01

    We investigate dust production and stellar mass loss in the Galactic globular cluster NGC 362. Due to its close proximity to the Small Magellanic Cloud (SMC), NGC 362 was imaged with the Infrared Array Camera and Multiband Imaging Photometer cameras onboard the Spitzer Space Telescope as part of the Surveying the Agents of Galaxy Evolution (SAGE-SMC) Spitzer Legacy program. We detect several cluster members near the tip of the red giant branch (RGB) that exhibit infrared excesses indicative of circumstellar dust and find that dust is not present in measurable quantities in stars below the tip of the RGB. We modeled the spectral energy distribution (SED) of the stars with the strongest IR excess and find a total cluster dust mass-loss rate of 3.0{sup +2.0}{sub -1.2} x 10{sup -9} M{sub sun} yr{sup -1}, corresponding to a gas mass-loss rate of 8.6{sup +5.6}{sub -3.4} x 10{sup -6} M{sub sun} yr{sup -1}, assuming [Fe/H] =-1.16. This mass loss is in addition to any dustless mass loss that is certainly occurring within the cluster. The two most extreme stars, variables V2 and V16, contribute up to 45% of the total cluster dust-traced mass loss. The SEDs of the more moderate stars indicate the presence of silicate dust, as expected for low-mass, low-metallicity stars. Surprisingly, the SED shapes of the stars with the strongest mass-loss rates appear to require the presence of amorphous carbon dust, possibly in combination with silicate dust, despite their oxygen-rich nature. These results corroborate our previous findings in omega Centauri.

  12. A New Black Hole Mass Estimate for Obscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Minezaki, Takeo; Matsushita, Kyoko

    2015-04-01

    We propose a new method for estimating the mass of a supermassive black hole, applicable to obscured active galactic nuclei (AGNs). This method estimates the black hole mass using the width of the narrow core of the neutral FeKα emission line in X-rays and the distance of its emitting region from the black hole based on the isotropic luminosity indicator via the luminosity scaling relation. Assuming the virial relation between the locations and the velocity widths of the neutral FeKα line core and the broad Hβ emission line, the luminosity scaling relation of the neutral FeKα line core emitting region is estimated. We find that the velocity width of the neutral FeKα line core falls between that of the broad Balmer emission lines and the corresponding value at the dust reverberation radius for most of the target AGNs. The black hole mass {{M}BH,FeKα } estimated with this method is then compared with other black hole mass estimates, such as the broad emission-line reverberation mass {{M}BH,rev} for type 1 AGNs, the mass {{M}BH,{{H2}O}} based on the H2O maser, and the single-epoch mass estimate {{M}BH,pol} based on the polarized broad Balmer lines for type 2 AGNs. We find that {{M}BH,FeKα } is consistent with {{M}BH,rev} and {{M}BH,pol}, and find that {{M}BH,FeKα } correlates well with {{M}BH,{{H2}O}}. These results suggest that {{M}BH,FeKα } is a potential indicator of the black hole mass for obscured AGNs. In contrast, {{M}BH,FeKα } is systematically larger than {{M}BH,{{H2}O}} by about a factor of 5, and the possible origins are discussed.

  13. No Evidence for Multiple Stellar Populations in the Low-mass Galactic Globular Cluster E 3

    NASA Astrophysics Data System (ADS)

    Salinas, Ricardo; Strader, Jay

    2015-08-01

    Multiple stellar populations are a widespread phenomenon among Galactic globular clusters. Even though the origin of the enriched material from which new generations of stars are produced remains unclear, it is likely that self-enrichment will be feasible only in clusters massive enough to retain this enriched material. We searched for multiple populations in the low mass (M˜ 1.4× {10}4 {M}⊙ ) globular cluster E3, analyzing SOAR/Goodman multi-object spectroscopy centered on the blue cyanogen (CN) absorption features of 23 red giant branch stars. We find that the CN abundance does not present the typical bimodal behavior seen in clusters hosting multistellar populations, but rather a unimodal distribution that indicates the presence of a genuine single stellar population, or a level of enrichment much lower than in clusters that show evidence for two populations from high-resolution spectroscopy. E3 would be the first bona fide Galactic old globular cluster where no sign of self-enrichment is found. Based on observations obtained at the Southern Astrophysical Research (SOAR) Telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the US National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  14. Population synthesis of classical low-mass X-ray binaries in the Galactic Bulge

    NASA Astrophysics Data System (ADS)

    van Haaften, L. M.; Nelemans, G.; Voss, R.; van der Sluys, M. V.; Toonen, S.

    2015-07-01

    Aims: We model the present-day population of classical low-mass X-ray binaries (LMXBs) with neutron star accretors, which have hydrogen-rich donor stars. Their population is compared with that of hydrogen-deficient LMXBs, known as ultracompact X-ray binaries (UCXBs). We model the observable LMXB population and compare it to observations. We model the Galactic Bulge because it contains a well-observed population and it is the target of the Galactic Bulge Survey. Methods: We combine the binary population synthesis code SeBa with detailed LMXB evolutionary tracks to model the size and properties of the present-day LMXB population in the Galactic Bulge. Whether sources are persistent or transient, and what their instantaneous X-ray luminosities are, is predicted using the thermal-viscous disk instability model. Results: We find a population of ~2.1 × 103 LMXBs with neutron star accretors. Of these about 15-40 are expected to be persistent (depending on model assumptions), with luminosities higher than 1035 erg s-1. About 7-20 transient sources are expected to be in outburst at any given time. Within a factor of two these numbers are consistent with the observed population of bright LMXBs in the Bulge. This gives credence to our prediction of the existence of a population of ~1.6 × 103 LMXBs with low donor masses that have gone through the period minimum, and have present-day mass transfer rates below 10-11 M⊙ yr-1. Conclusions: Even though the observed population of hydrogen-rich LMXBs in the Bulge is larger than the observed population of (hydrogen-deficient) UCXBs, the latter have a higher formation rate. While UCXBs may dominate the total LMXB population at the present time, the majority would be very faint or may have become detached and produced millisecond radio pulsars. In that case UCXBs would contribute significantly more to the formation of millisecond radio pulsars than hydrogen-rich LMXBs.

  15. The origins of active galactic nuclei obscuration: the 'torus' as a dynamical, unstable driver of accretion

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Hayward, Christopher C.; Narayanan, Desika; Hernquist, Lars

    2012-02-01

    Recent multiscale simulations have made it possible to follow gas inflows responsible for high-Eddington ratio accretion on to massive black holes (BHs) from galactic scales to the BH accretion disc. When sufficient gas is driven towards a BH, gravitational instabilities generically form lopsided, eccentric discs that propagate inwards from larger radii. The lopsided stellar disc exerts a strong torque on the gas, driving inflows that fuel the growth of the BH. Here, we investigate the possibility that the same disc, in its gas-rich phase, is the putative 'torus' invoked to explain obscured active galactic nuclei (AGN) and the cosmic X-ray background. The disc is generically thick and has characteristic ˜1-10 pc sizes and masses resembling those required of the torus. Interestingly, the scale heights and obscured fractions of the predicted torii are substantial even in the absence of strong stellar feedback providing the vertical support. Rather, they can be maintained by strong bending modes and warps/twists excited by the inflow-generating instabilities. A number of other observed properties commonly attributed to 'feedback' processes may in fact be explained entirely by dynamical, gravitational effects: the lack of alignment between torus and host galaxy, correlations between local star formation rate (SFR) and turbulent gas velocities and the dependence of obscured fractions on AGN luminosity or SFR. We compare the predicted torus properties with observations of gas surface density profiles, kinematics, scale heights and SFR densities in AGN, and find that they are consistent in all cases. We argue that it is not possible to reproduce these observations and the observed column density distribution without a clumpy gas distribution, but allowing for simple clumping on small scales the predicted column density distribution is in good agreement with observations from NH˜ 1020-1027 cm-2. We examine how the NH distribution scales with galaxy and AGN properties

  16. AN INITIAL MASS FUNCTION FOR INDIVIDUAL STARS IN GALACTIC DISKS. I. CONSTRAINING THE SHAPE OF THE INITIAL MASS FUNCTION

    SciTech Connect

    Parravano, Antonio; McKee, Christopher F.; Hollenbach, David J.

    2011-01-01

    We derive a semi-empirical galactic initial mass function (IMF) from observational constraints. We assume that the IMF, {psi}(m), is a smooth function of the stellar mass m. The mass dependence of the proposed IMF is determined by five parameters: the low-mass slope {gamma}, the high-mass slope -{Gamma} (taken to be -1.35), the characteristic mass m{sub ch} ({approx} the peak mass of the IMF), and the lower and upper limits on the mass, m{sub l} and m{sub u} (taken to be 0.004 and 120 M{sub sun}, respectively): {psi}(m)dln m {proportional_to} m{sup -}{Gamma}{l_brace}1 - exp [- (m/m{sub ch}){sup {gamma}}+{Gamma}]{r_brace}dln m. The values of {gamma} and m{sub ch} are derived from two integral constraints: (1) the ratio of the number density of stars in the range m = 0.1-0.6 M{sub sun} to that in the range m = 0.6-0.8 M{sub sun} as inferred from the mass distribution of field stars in the local neighborhood and (2) the ratio of the number of stars in the range m = 0.08-1 M{sub sun} to the number of brown dwarfs in the range m = 0.03-0.08 M{sub sun} in young clusters. The IMF satisfying the above constraints is characterized by the parameters {gamma} = 0.51 and m{sub ch} = 0.35 M{sub sun} (which corresponds to a peak mass of 0.27 M{sub sun} ). This IMF agrees quite well with the Chabrier IMF for the entire mass range over which we have compared with data, but predicts significantly more stars with masses <0.03 M{sub sun}; we also compare with other IMFs in current use and give a number of important parameters implied by the IMFs.

  17. Sigma observations of the low mass X-ray binaries of the galactic bulge

    NASA Technical Reports Server (NTRS)

    Goldwurm, A.; Denis, M.; Paul, J.; Faisse, S.; Roques, J. P.; Bouchet, L.; Vedrenne, G.; Mandrou, P.; Sunyaev, R.; Churazov, E.

    1995-01-01

    The soft gamma-ray telescope (35-1300 keV) SIGMA aboard the high energy GRANAT space observatory has been monitoring the Galactic Bulge region for more than 2000 h of effective time since March 1990. In the resulting average 35-75 keV image we detected ten sources at a level of greater than 5 standard deviations, 6 of which can be identified with low mass X-ray binaries (LMXB). Among them, one is the 1993 X-ray nova in Ophiuchus (GRS 1726-249), one is an X-ray pulsar (GX 1+4), two are associated with X-ray bursters (GX 354-0 and A 1742-294) and two with bursting X-ray binaries in the globular clusters Terzan 2 and Terzan 1. Their spectral and long term variability behavior as measured by SIGMMA are presented and discussed.

  18. The mass function of IC 4665 revisited by the UKIDSS Galactic Clusters Survey

    NASA Astrophysics Data System (ADS)

    Lodieu, N.; de Wit, W.-J.; Carraro, G.; Moraux, E.; Bouvier, J.; Hambly, N. C.

    2011-08-01

    Context. Knowledge of the mass function in open clusters constitutes one way to constrain the formation of low-mass stars and brown dwarfs as does the knowledge of the frequency of multiple systems and the properties of disks. Aims: The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes in the pre-main sequence (27 Myr) cluster IC 4665, which is located at 350 pc from the Sun. Methods: We have cross-matched the near-infrared photometric data from the Eighth Data Release (DR8) of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS) with previous optical data obtained with the Canada-France-Hawaii (CFH) wide-field camera to improve the determination of the luminosity and mass functions in the low-mass and substellar regimes. Results: The availability of i and z photometry taken with the CFH12K camera on the Canada France Hawaii Telescope added strong constraints to the UKIDSS photometric selection in this cluster, which is located in a dense region of our Galaxy. We have derived the luminosity and mass functions of the cluster down to J = 18.5 mag, corresponding to masses of ~0.025 M⊙ at the distance and age of IC 4665 according to theoretical models. In addition, we have extracted new candidate members down to ~20 Jupiter masses in a previously unstudied region of the cluster. Conclusions: We have derived the mass function over the 0.6-0.04 M⊙ mass range and found that it is best represented by a log-normal function with a peak at 0.25-0.16 M⊙, consistent with the determination in the Pleiades. This work is based in part on data obtained as part of the UKIRT Infrared Deep Sky Survey. The United Kingdom Infrared Telescope is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the UK.This work is partly based on observations obtained at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada

  19. The Realm of the Galactic Globular Clusters and the Mass of Their Primordial Clouds

    NASA Astrophysics Data System (ADS)

    Tenorio-Tagle, Guillermo; Muñoz-Tuñón, Casiana; Cassisi, Santi; Silich, Sergiy

    2016-07-01

    By adopting the empirical constraints related to the estimates of helium enhancement ({{Δ }}Y), the present mass ratio between first and second stellar generations ({M}1{{G}}/{M}2{{G}}), and the actual mass of Galactic globular clusters (M GC), we envisage a possible scenario for the formation of these stellar systems. Our approach allows for the possible loss of stars through evaporation or tidal interactions and different star-formation efficiencies. In our approach, the star-formation efficiency of the first generation (ɛ 1G) is the central factor that links the stellar generations because it not only defines both the mass in stars of the first generation and the remaining mass available for further star formation, but it also fixes the amount of matter required to contaminate the second stellar generation. In this way, ɛ 1G is fully defined by the He enhancement between successive generations in a GC. We also show that globular clusters fit well within a ΔY versus {M}1{{G}}/{M}2{{G}} diagram that indicates three different evolutionary paths. The central one is for clusters that have not lost stars through tidal interactions from either of their stellar generations, and thus their present M GC value is identical to the amount of low-mass stars (M * ≤ 1 M ⊙) that resulted from both stellar generations. Other possible evolutions imply either the loss of first-generation stars or the combination of a low star-formation efficiency in the second stellar generation and a loss of stars from the second generation. From these considerations, we derive a lower limit to the mass (M tot) of the individual primordial clouds that gave origin to globular clusters.

  20. Made-to-measure models of the Galactic box/peanut bulge: stellar and total mass in the bulge region

    NASA Astrophysics Data System (ADS)

    Portail, M.; Wegg, C.; Gerhard, O.; Martinez-Valpuesta, I.

    2015-03-01

    We construct dynamical models of the Milky Way's box/peanut (B/P) bulge, using the recently measured 3D density of red clump giants (RCGs) as well as kinematic data from the Bulge Radial Velocity Assay (BRAVA) survey. We match these data using the NMAGIC made-to-measure method, starting with N-body models for barred discs in different dark matter haloes. We determine the total mass in the bulge volume of the RCGs measurement ( ± 2.2 × ±1.4 × ±1.2 kpc) with unprecedented accuracy and robustness to be 1.84 ± 0.07 × 1010 M⊙. The stellar mass in this volume varies between 1.25 and 1.6 × 1010 M⊙, depending on the amount of dark matter in the bulge. We evaluate the mass-to-light and mass-to-clump ratios in the bulge and compare them to theoretical predictions from population synthesis models. We find a mass-to-light ratio in the K band in the range 0.8-1.1. The models are consistent with a Kroupa or Chabrier initial mass function (IMF), but a Salpeter IMF is ruled out for stellar ages of 10 Gyr. To match predictions from the Zoccali IMF derived from the bulge stellar luminosity function requires ˜40 per cent or ˜ 0.7 × 1010 M⊙ dark matter in the bulge region. The BRAVA data together with the RCGs 3D density imply a low pattern speed for the Galactic B/P bulge of Ωp = 25-30 km s- 1 kpc- 1. This would place the Galaxy among the slow rotators (R ≥ 1.5). Finally, we show that the Milky Way's B/P bulge has an off-centred X structure, and that the stellar mass involved in the peanut shape accounts for at least 20 per cent of the stellar mass of the bulge, significantly larger than previously thought.

  1. The dynamical fate of binary star clusters in the Galactic tidal field

    NASA Astrophysics Data System (ADS)

    Priyatikanto, R.; Kouwenhoven, M. B. N.; Arifyanto, M. I.; Wulandari, H. R. T.; Siregar, S.

    2016-04-01

    Fragmentation and fission of giant molecular clouds occasionally results in a pair of gravitationally bound star clusters that orbit their mutual centre of mass for some time, under the influence of internal and external perturbations. We investigate the evolution of binary star clusters with different orbital configurations, with a particular focus on the Galactic tidal field. We carry out N-body simulations of evolving binary star clusters and compare our results with estimates from our semi-analytic model. The latter accounts for mass-loss due to stellar evolution and two-body relaxation, and for evolution due to external tides. Using the semi-analytic model, we predict the long-term evolution for a wide range of initial conditions. It accurately describes the global evolution of such systems, until the moment when a cluster merger is imminent. N-body simulations are used to test our semi-analytic model and also to study additional features of evolving binary clusters, such as the kinematics of stars, global cluster rotation, evaporation rates, and the cluster merger process. We find that the initial orientation of a binary star cluster with respect to the Galactic field, and also the initial orbital phase, is crucial for its fate. Depending on these properties, the binaries may experience orbital reversal, spiral-in, or vertical oscillation about the Galactic plane before they actually merge at t ≈ 100 Myr, and produce rotating star clusters with slightly higher evaporation rates. The merger process of a binary cluster induces an outburst that ejects ˜10 per cent of the stellar members into the Galactic field.

  2. Shaping the relation between the mass of supermassive black holes and the velocity dispersion of galactic bulges

    NASA Astrophysics Data System (ADS)

    Chan, M. H.

    2013-05-01

    I use the fact that the radiation emitted by the accretion disk of supermassive black hole can heat up the surrounding gas in the protogalaxy to achieve hydrostatic equilibrium during the galaxy formation. The correlation between the black hole mass M BH and velocity dispersion σ thus naturally arises. The result generally agrees with empirical fittings from observational data, even with M BH ≤106 M ⊙. This model provides a clear picture on how the properties of the galactic supermassive black holes are connected with the kinetic properties of the galactic bulges.

  3. Spin and mass of the supermassive black hole in the Galactic Center

    SciTech Connect

    Dokuchaev, V. I.

    2015-12-15

    A new method for exact determination of the masses and spins of black holes from the observations of quasi-periodic oscillations is discussed. The detected signal from the hot clumps in the accretion plasma must contain modulations with two characteristic frequencies: the frequency of rotation of the black hole event horizon and the frequency of the latitudinal precession of the clump’s orbit. Application of the method of two characteristic frequencies for interpretation of the observed quasi-periodic oscillations from the supermassive black hole in the Galactic center in the X-rays and in the near IR region yields the most exact, for the present, values of the mass and the spin (Kerr parameter) of the Sgr A* black hole: M = (4.2 ± 0.2) × 10{sup 6}M{sub ⊙} and a = 0.65 ± 0.05. The observed quasi-periodic oscillations with a period of about 11.5 min are identified as the black hole event horizon rotation period and those with a period of about 19 min are identified as the latitudinal oscillation period of the hot spot orbits in the accretion disk.

  4. Formation and Evolution of Galactic Intermediate/Low-Mass X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Shao, Yong; Li, Xiang-Dong

    2015-08-01

    We investigate the formation and evolutionary sequences of Galactic intermediate- and low-mass X-ray binaries (I/LMXBs) by combining binary population synthesis (BPS) and detailed stellar evolutionary calculations. Using an updated BPS code we compute the evolution of massive binaries that leads to the formation of incipient I/LMXBs and present their distribution in the initial donor mass versus initial orbital period diagram. We then follow the evolution of the I/LMXBs until the formation of binary millisecond pulsars (BMSPs). We find that the birthrate of the I/LMXB population is in the range of 9 × 10-6-3.4 × 10-5 yr-1, compatible with that of BMSPs that are thought to descend from I/LMXBs. We show that during the evolution of I/LMXBs they are likely to be observed as relatively compact binaries with orbital periods ≲1 day and donor masses ≲0.3M⊙. The resultant BMSPs have orbital periods ranging from less than 1 day to a few hundred days. These features are consistent with observations of LMXBs and BMSPs. We also confirm the discrepancies between theoretical predictions and observations mentioned in the literature, that is, the theoretical average mass transfer rates (˜10-10 M⊙ yr-1) of LMXBs are considerably lower than observed, and the number of BMSPs with orbital periods ˜0.1-10 days is severely underestimated. These discrepancies imply that something is missing in the modeling of LMXBs, which is likely to be related to the mechanisms of the orbital angular momentum loss.

  5. HIGH-PRECISION DYNAMICAL MASSES OF VERY LOW MASS BINARIES

    SciTech Connect

    Konopacky, Q. M.; Ghez, A. M.; McLean, I. S.; Barman, T. S.; Rice, E. L.; Bailey, J. I.; White, R. J.; Duchene, G. E-mail: ghez@astro.ucla.ed E-mail: barman@lowell.ed E-mail: white@chara.gsu.ed

    2010-03-10

    We present the results of a three year monitoring program of a sample of very low mass (VLM) field binaries using both astrometric and spectroscopic data obtained in conjunction with the laser guide star adaptive optics system on the W. M. Keck II 10 m telescope. Among the 24 systems studied, 15 have undergone sufficient orbital motion, allowing us to derive their relative orbital parameters and hence their total system mass. These measurements more than double the number of mass measurements for VLM objects, and include the most precise mass measurement to date (<2%). Among the 11 systems with both astrometric and spectroscopic measurements, six have sufficient radial velocity variations to allow us to obtain individual component masses. This is the first derivation of the component masses for five of these systems. Altogether, the orbital solutions of these low mass systems show a correlation between eccentricity and orbital period, consistent with their higher mass counterparts. In our primary analysis, we find that there are systematic discrepancies between our dynamical mass measurements and the predictions of theoretical evolutionary models (TUCSON and LYON) with both models either underpredicting or overpredicting the most precisely determined dynamical masses. These discrepancies are a function of spectral type, with late-M through mid-L systems tending to have their masses underpredicted, while one T-type system has its mass overpredicted. These discrepancies imply that either the temperatures predicted by evolutionary and atmosphere models are inconsistent for an object of a given mass, or the mass-radius relationship or cooling timescales predicted by the evolutionary models are incorrect. If these spectral-type trends are correct and hold into the planetary mass regime, the implication is that the masses of directly imaged extrasolar planets are overpredicted by the evolutionary models.

  6. Hubble Space Telescope Proper Motion (HSTPROMO) Catalogs of Galactic Globular Clusters. IV. Kinematic Profiles and Average Masses of Blue Straggler Stars

    NASA Astrophysics Data System (ADS)

    Baldwin, A. T.; Watkins, L. L.; van der Marel, R. P.; Bianchini, P.; Bellini, A.; Anderson, J.

    2016-08-01

    We make use of the Hubble Space Telescope proper-motion catalogs derived by Bellini et al. to produce the first radial velocity dispersion profiles σ (R) for blue straggler stars (BSSs) in Galactic globular clusters (GCs), as well as the first dynamical estimates for the average mass of the entire BSS population. We show that BSSs typically have lower velocity dispersions than stars with mass equal to the main-sequence turnoff mass, as one would expect for a more massive population of stars. Since GCs are expected to experience some degree of energy equipartition, we use the relation σ \\propto {M}-η , where η is related to the degree of energy equipartition, along with our velocity dispersion profiles to estimate BSS masses. We estimate η as a function of cluster relaxation from recent Monte Carlo cluster simulations by Bianchini et al. and then derive an average mass ratio {M}{BSS}/{M}{MSTO}=1.50+/- 0.14 and an average mass {M}{BSS}=1.22+/- 0.12 M ⊙ from 598 BSSs across 19 GCs. The final error bars include any systematic errors that are random between different clusters, but not any potential biases inherent to our methodology. Our results are in good agreement with the average mass of {M}{BSS}=1.22+/- 0.06 M ⊙ for the 35 BSSs in Galactic GCs in the literature with properties that have allowed individual mass determination. Based on proprietary and archival observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

  7. The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline

    NASA Astrophysics Data System (ADS)

    Kruijssen, J. M. Diederik; Dale, James E.; Longmore, Steven N.

    2015-02-01

    We recently proposed that the star-forming potential of dense molecular clouds in the Central Molecular Zone (CMZ, i.e. the central few 100 pc) of the Milky Way is intimately linked to their orbital dynamics, potentially giving rise to an absolute-time sequence of star-forming clouds. In this paper, we present an orbital model for the gas stream(s) observed in the CMZ. The model is obtained by integrating orbits in the empirically constrained gravitational potential and represents a good fit (χ _red^2=2.0) to the observed position-velocity distribution of dense (n > several 103 cm-3) gas, reproducing all of its key properties. The orbit is also consistent with observational constraints not included in the fitting process, such as the 3D space velocities of Sgr B2 and the Arches and Quintuplet clusters. It differs from previous, parametric models in several respects: (1) the orbit is open rather than closed due to the extended mass distribution in the CMZ, (2) its orbital velocity (100-200 km s-1) is twice as high as in previous models, and (3) Sgr A* coincides with the focus of the (eccentric) orbit rather than being offset. Our orbital solution supports the recently proposed scenario in which the dust ridge between G0.253+0.016 (`the Brick') and Sgr B2 represents an absolute-time sequence of star-forming clouds, of which the condensation was triggered by the tidal compression during their most recent pericentre passage. We position the clouds on a common timeline and find that their pericentre passages occurred 0.30-0.74 Myr ago. Given their short free-fall times (tff ˜ 0.34 Myr), the quiescent cloud G0.253+0.016 and the vigorously star-forming complex Sgr B2 are separated by a single free-fall time of evolution, implying that star formation proceeds rapidly once collapse has been initiated. We provide the complete orbital solution, as well as several quantitative predictions of our model (e.g. proper motions and the positions of star formation `hotspots'). The

  8. C II forbidden-line 158 micron mapping in Sagittarius A Rotation curve and mass distribution in the galactic center

    NASA Technical Reports Server (NTRS)

    Lugten, J. B.; Genzel, R.; Crawford, M. K.; Townes, C. H.

    1986-01-01

    Based on data obtained with the NASA Kuiper Airborne Observatory 91.4 cm telescope, the 158-micron fine structure line emission of C(+) is mapped near the galactic center. The strongest emission comes from a 10-pc FWHM diameter disk centered on Sgr A West whose dominant motion is rotation. Extended C(+) emission is also found from the +50 km/s galactic center molecular cloud, and a second cloud at v(LSR) of about -35 km/s. The rotation curve and mass distribution within 10 pc of the galactic center are derived, and the C(+) profiles show a drop-off of rotation velocity between 2 and 10 pc. A mass model is suggested with 2-4 million solar masses in a central point mass, and a M/L ratio of the central stellar cluster of 0.5 solar masses/solar luminosities, suggesting a large abundance of giants and relatively recent star formation in the center.

  9. On the dynamics of Armbruster Guckenheimer Kim galactic potential in a rotating reference frame

    NASA Astrophysics Data System (ADS)

    Elmandouh, A. A.

    2016-06-01

    In this article, we are interested in studying some dynamics aspects for the Armbruster Guckenheimer Kim galactic potential in a rotating reference frame. We introduce a non-integrability condition for this problem using Painlevé analysis. The equilibrium positions are given and their stability is studied. Furthermore, we prove the force resulting from the rotation of the reference frame can be used to stabilize the unstable maximum equilibrium positions. The periodic solutions near the equilibrium positions are constructed by applying Lyapunov method. The permitted region of motion is determined.

  10. CCD Observing and Dynamical Time Series Analysis of Active Galactic Nuclei.

    NASA Astrophysics Data System (ADS)

    Nair, Achotham Damodaran

    1995-01-01

    The properties, working and operations procedure of the Charge Coupled Device (CCD) at the 30" telescope at Rosemary Hill Observatory (RHO) are discussed together with the details of data reduction. Several nonlinear techniques of time series analysis, based on the behavior of the nearest neighbors, have been used to analyze the time series of the quasar 3C 345. A technique using Artificial Neural Networks based on prediction of the time series is used to study the dynamical properties of 3C 345. Finally, a heuristic model for variability of Active Galactic Nuclei is discussed.

  11. Beyond halo mass: galactic conformity as a smoking gun of central galaxy assembly bias

    NASA Astrophysics Data System (ADS)

    Hearin, Andrew P.; Watson, Douglas F.; van den Bosch, Frank C.

    2015-09-01

    Quenched central galaxies tend to reside in a preferentially quenched large-scale environment, a phenomenon that has been dubbed galactic conformity. Remarkably, this tendency persists out to scales far larger than the virial radius of the halo hosting the central. Therefore, conformity manifestly violates the widely adopted assumption that the dark matter halo mass Mvir exclusively governs galaxy occupation statistics. This paper is the first in a series studying the implications of the observed conformity signal for the galaxy-dark matter connection. We show that recent measurements of conformity on scales r ˜ 1-5 Mpc imply that central galaxy quenching statistics cannot be correctly predicted with the knowledge of Mvir alone. We also demonstrate that ejected (or `backsplash') satellites cannot give rise to the signal. We then invoke the age matching model, which is predicated on the co-evolution of galaxies and haloes. We find that this model produces a strong signal, and that central galaxies are solely responsible. We conclude that large-scale `two-halo' conformity represents a smoking gun of central galaxy assembly bias, and indicates that contemporary models of satellite quenching have systematically overestimated the influence of post-infall processes.

  12. WISE detection of the galactic low-mass X-ray binaries

    SciTech Connect

    Wang, Xuebing; Wang, Zhongxiang

    2014-06-20

    We report on the results from our search for the Wide-field Infrared Survey Explorer (WISE) detection of the Galactic low-mass X-ray binaries (LMXBs). Among 187 binaries cataloged in Liu et al., we find 13 counterparts and 2 candidate counterparts. For the 13 counterparts, 2 (4U 0614+091 and GX 339–4) have already been confirmed by previous studies to have a jet and 1 (GRS 1915+105) to have a candidate circumbinary disk, from which the detected infrared emission arose. Having collected the broadband optical and near-infrared data in the literature and constructed flux density spectra for the other 10 binaries, we identify that 3 (A0620–00, XTE J1118+480, and GX 1+4) are candidate circumbinary disk systems, 4 (Cen X-4, 4U 1700+24, 3A 1954+319, and Cyg X-2) had thermal emission from their companion stars, and 3 (Sco X-1, Her X-1, and Swift J1753.5–0127) are peculiar systems with the origin of their infrared emission rather uncertain. We discuss the results and WISE counterparts' brightness distribution among the known LMXBs, and suggest that more than half of the LMXBs would have a jet, a circumbinary disk, or both.

  13. WISE Detection of the Galactic Low-mass X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    Wang, Xuebing; Wang, Zhongxiang

    2014-06-01

    We report on the results from our search for the Wide-field Infrared Survey Explorer (WISE) detection of the Galactic low-mass X-ray binaries (LMXBs). Among 187 binaries cataloged in Liu et al., we find 13 counterparts and 2 candidate counterparts. For the 13 counterparts, 2 (4U 0614+091 and GX 339-4) have already been confirmed by previous studies to have a jet and 1 (GRS 1915+105) to have a candidate circumbinary disk, from which the detected infrared emission arose. Having collected the broadband optical and near-infrared data in the literature and constructed flux density spectra for the other 10 binaries, we identify that 3 (A0620-00, XTE J1118+480, and GX 1+4) are candidate circumbinary disk systems, 4 (Cen X-4, 4U 1700+24, 3A 1954+319, and Cyg X-2) had thermal emission from their companion stars, and 3 (Sco X-1, Her X-1, and Swift J1753.5-0127) are peculiar systems with the origin of their infrared emission rather uncertain. We discuss the results and WISE counterparts' brightness distribution among the known LMXBs, and suggest that more than half of the LMXBs would have a jet, a circumbinary disk, or both.

  14. On the formation of galactic black hole low-mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Jia, Kun; Li, Xiang-Dong

    2016-03-01

    Currently, there are 24 black hole (BH) X-ray binary systems that have been dynamically confirmed in the Galaxy. Most of them are low-mass X-ray binaries (LMXBs) comprised of a stellar-mass BH and a low-mass donor star. Although the formation of these systems has been extensively investigated, some crucial issues remain unresolved. The most noticeable one is that, the low-mass companion has difficulties in ejecting the tightly bound envelope of the massive primary during the spiral-in process. While initially intermediate-mass binaries are more likely to survive the common envelope (CE) evolution, the resultant BH LMXBs mismatch the observations. In this paper, we use both stellar evolution and binary population synthesis to study the evolutionary history of BH LMXBs. We test various assumptions and prescriptions for the supernova mechanisms that produce BHs, the binding energy parameter, the CE efficiency and the initial mass distributions of the companion stars. We obtain the birthrate and the distributions of the donor mass, effective temperature and orbital period for the BH LMXBs in each case. By comparing the calculated results with the observations, we put useful constraints on the aforementioned parameters. In particular, we show that it is possible to form BH LMXBs with the standard CE scenario if most BHs are born through failed supernovae.

  15. Synthetic extinction maps around intermediate-mass black holes in Galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Pepe, C.; Pellizza, L. J.

    2016-08-01

    During the last decades, much effort has been devoted to explain the discrepancy between the amount of intracluster medium (ICM) estimated from stellar evolution theories and that emerging from observations in globular clusters (GCs). One possible scenario is the accretion of this medium by an intermediate-mass black hole (IMBH) at the centre of the cluster. In this work, we aim at modelling the cluster colour-excess profile as a tracer of the ICM density, both with and without an IMBH. Comparing the profiles with observations allows us to test the existence of IMBHs and their possible role in the cleansing of the ICM. We derive the intracluster density profiles from hydrodynamical models of accretion on to a central IMBH in a GC and we determine the corresponding dust density. This model is applied to a list of 25 Galactic GCs. We find that central IMBHs decrease the ICM by several orders of magnitude. In a subset of nine clusters, the absence of the black hole combined with a low-ICM temperature would be at odds with present gas mass content estimations. As a result, we conclude that IMBHs are an effective cleansing mechanism of the ICM of GCs. We construct synthetic extinction maps for M 62 and ωCen, two clusters in the small subset of nine with observed 2D extinction maps. We find that under reasonable assumptions regarding the model parameters, if the gas temperature in M 62 is close to 8000 K, an IMBH needs to be invoked. Further ICM observations regarding both the gas and dust in GCs could help to settle this issue.

  16. Synthetic extinction maps around intermediate-mass black holes in Galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Pepe, C.; Pellizza, L. J.

    2016-08-01

    During the last decades, much effort has been devoted to explain the discrepancy between the amount of intracluster medium (ICM) estimated from stellar evolution theories and that emerging from observations in globular clusters (GCs). One possible scenario is the accretion of this medium by an intermediate-mass black hole (IMBH) at the centre of the cluster. In this work, we aim at modelling the cluster colour-excess profile as a tracer of the ICM density, both with and without an IMBH. Comparing the profiles with observations allows us to test the existence of IMBHs and their possible role in the cleansing of the ICM. We derive the intracluster density profiles from hydrodynamical models of accretion onto a central IMBH in a GC and we determine the corresponding dust density. This model is applied to a list of 25 Galactic GCs. We find that central IMBHs decrease the ICM by several orders of magnitude. In a subset of 9 clusters, the absence of the black hole combined with a low intracluster medium temperature would be at odds with present gas mass content estimations. As a result, we conclude that IMBHs are an effective cleansing mechanism of the ICM of GCs. We construct synthetic extinction maps for M 62 and {\\omega} Cen, two clusters in the small subset of 9 with observed 2D extinction maps. We find that under reasonable assumptions regarding the model parameters, if the gas temperature in M 62 is close to 8000 K, an IMBH needs to be invoked. Further ICM observations regarding both the gas and dust in GCs could help to settle this issue.

  17. Virtual mass effect in dynamic micromechanical mass sensing in liquids

    NASA Astrophysics Data System (ADS)

    Peiker, P.; Oesterschulze, E.

    2016-06-01

    Weighing individual micro- or nanoscale particles in solution using dynamic micromechanical sensors is quite challenging: viscous losses dramatically degrade the sensor's performance by both broadening the resonance peak and increasing the effective total mass of the resonator by the dragged liquid. While the virtual mass of the resonator was discussed frequently, little attention has been paid to the virtual mass of particles attached to the resonator's surface and its impact on the accuracy of mass sensing. By means of the in situ detection of a polystyrene microbead in water using a bridge-based microresonator, we demonstrate that the virtual mass of the bead significantly affects the observed frequency shift. In fact, 55 % of the frequency shift was caused by the virtual mass of the adsorbed bead, predicted by Stoke's theory. Based on the observed shift in the resonator's quality factor during particle adsorption, we confirm this significant effect of the virtual mass. Thus, a quantitative analysis of the mass of a single adsorbed particle is strongly diminished if dynamic micromechanical sensors are operated in a liquid environment.

  18. Quark mass effect on axial charge dynamics

    NASA Astrophysics Data System (ADS)

    Guo, Er-dong; Lin, Shu

    2016-05-01

    We studied the effect of finite quark mass on the dynamics of the axial charge using the D3/D7 model in holography. The mass term in the axial anomaly equation affects both the fluctuation (generation) and dissipation of the axial charge. We studied the dependence of the effect on quark mass and an external magnetic field. For axial charge generation, we calculated the mass diffusion rate, which characterizes the helicity flipping rate. The rate is a nonmonotonous function of mass and can be significantly enhanced by the magnetic field. The diffusive behavior is also related to a divergent susceptibility of the axial charge. For axial charge dissipation, we found that in the long time limit, the mass term dissipates all the charge effectively generated by parallel electric and magnetic fields. The result is consistent with a relaxation time approximation. The rate of dissipation through mass term is a monotonous increasing function of both quark mass and a magnetic field.

  19. REGULATION OF STAR FORMATION RATES IN MULTIPHASE GALACTIC DISKS: A THERMAL/DYNAMICAL EQUILIBRIUM MODEL

    SciTech Connect

    Ostriker, Eve C.; McKee, Christopher F.; Leroy, Adam K. E-mail: cmckee@astro.berkeley.ed

    2010-10-01

    We develop a model for the regulation of galactic star formation rates {Sigma}{sub SFR} in disk galaxies, in which interstellar medium (ISM) heating by stellar UV plays a key role. By requiring that thermal and (vertical) dynamical equilibrium are simultaneously satisfied within the diffuse gas, and that stars form at a rate proportional to the mass of the self-gravitating component, we obtain a prediction for {Sigma}{sub SFR} as a function of the total gaseous surface density {Sigma} and the midplane density of stars+dark matter {rho}{sub sd}. The physical basis of this relationship is that the thermal pressure in the diffuse ISM, which is proportional to the UV heating rate and therefore to {Sigma}{sub SFR}, must adjust until it matches the midplane pressure value set by the vertical gravitational field. Our model applies to regions where {Sigma} {approx}< 100 M{sub sun} pc{sup -2}. In low-{Sigma}{sub SFR} (outer-galaxy) regions where diffuse gas dominates, the theory predicts that {Sigma}{sub SFR{proportional_to}{Sigma}{radical}}({rho}{sub sd}). The decrease of thermal equilibrium pressure when {Sigma}{sub SFR} is low implies, consistent with observations, that star formation can extend (with declining efficiency) to large radii in galaxies, rather than having a sharp cutoff at a fixed value of {Sigma}. The main parameters entering our model are the ratio of thermal pressure to total pressure in the diffuse ISM, the fraction of diffuse gas that is in the warm phase, and the star formation timescale in self-gravitating clouds; all of these are (at least in principle) direct observables. At low surface density, our model depends on the ratio of the mean midplane FUV intensity (or thermal pressure in the diffuse gas) to the star formation rate, which we set based on solar-neighborhood values. We compare our results to recent observations, showing good agreement overall for azimuthally averaged data in a set of spiral galaxies. For the large flocculent spiral

  20. Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas

    NASA Astrophysics Data System (ADS)

    Suchkov, Anatoly A.; Balsara, Dinshaw S.; Heckman, Timothy M.; Leitherer, Claus

    1994-08-01

    There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and

  1. Dynamics and X-ray emission of a galactic superwind interacting with disk and halo gas

    NASA Technical Reports Server (NTRS)

    Suchkov, Anatoly A.; Balsara, Dinshaw S.; Heckman, Timothy M.; Leitherner, Claus

    1994-01-01

    There is a general agreement that the conspicuous extranuclear X-ray, optical-line, and radio-contiuum emission of starbursts is associated with powerful galactic superwinds blowing from their centers. However, despite the significant advances in observational studies of superwinds, there is no consensus on the nature of the emitting material and even on the emission mechanisms themselves. This is to a great extent a consequence of a poor understanding of dynamical processes in the starburst superwind regions. To address this issue, we have conducted two-dimensional hydrodynamical simulations of galactic superwinds. While previous similar studies have used a single (disk) component to represent the ISM of the starburst galaxy, we analyze the interaction of the wind with a two-component disk-halo ambient interstellar medium and argue that this two-component representation is crucial for adequate modeling of starbursts. The emphasis of this study is on the geometry and structure of the wind region and the X-ray emission arising in the wind material and the shocked gas in the disk and the halo of the galaxy. The simulation results have shown that a clear-cut bipolar wind can easily develop under a range of very different conditions. On the other hand, a complex 'filamentary' structure associated with the entrained dense disk material is found to arise within the hot bubble blown out by the wind. The flow pattern within the bubble is dominated equally by the central biconic outflow and a system of whirling motions r elated to the origin and development of the 'filaments'. The filament parameters make them a good candidate for optical-emission-line filamentary gas observed in starburst halos. We find that the history of mass and energy deposition in the starburst region of the galaxy is crucial for wind dynamics. A 'mild' early wind, which arises as a result of the cumulative effect of stellar winds from massive stars, produces a bipolar vertical cavity in the disk and

  2. Intermediate-Mass Black Hole(s) and Stellar Orbits in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Levin, Yuri; Wu, Alice; Thommes, Ed

    2005-12-01

    Many young stars reside within the central half-parsec from Sgr A*, the supermassive black hole in the Galactic center. The origin of these stars remains a puzzle. Recently, Hansen & Milosavljevic (HM) have argued that an intermediate-mass black hole (IMBH) could have delivered the young stars to the immediate vicinity of Sgr A*. Here we focus on the final stages of the HM scenario. Namely, we integrate numerically the orbits of stars that are initially bound to the IMBH but are stripped from it by the tidal field of Sgr A*. Our numerical algorithm is a symplectic integrator designed specifically for the problem at hand; however, we have checked our results with SYMBA, a version of the widely available SWIFT code. We find that the distribution of the postinspiral orbital parameters is sensitive to the eccentricity of the inspiraling IMBH. If the IMBH is on a circular orbit, then the inclinations of numerically computed orbits relative to the inspiral plane are almost always smaller than 10°, and therefore (1) the simulations are in good agreement with the observed motions of stars in a clockwise-moving stellar disk; and (2) the simulations never reproduce the orbits of stars outside this disk, which include those in the second thick ring of stars and the randomly oriented unrelaxed orbits of some of the S stars. If the IMBH's orbital eccentricity is e=0.6, then approximately half of the stars end up with orbital inclinations below 10°, and another half have inclinations anywhere between 0° and 180° this is somewhat closer to what is observed. We also show that if the IRS 13 cluster is bound by an IMBH, as has been argued by Maillard et al., then the same IMBH could not have delivered all of the young stars to their present location.

  3. A solution of the coincidence problem based on the recent galactic core black hole mass density increase

    NASA Astrophysics Data System (ADS)

    Kofinas, Georgios; Zarikas, Vasilios

    2013-04-01

    A mechanism capable to provide a natural solution to two major cosmological problems, i.e. the cosmic acceleration and the coincidence problem, is proposed. A specific brane-bulk energy exchange mechanism produces a total dark pressure, arising when adding all normal to the brane negative pressures in the interior of galactic core black holes. This astrophysically produced negative dark pressure explains cosmic acceleration and why the dark energy today is of the same order to the matter density for a wide range of the involved parameters. An exciting result of the analysis is that the recent rise of the galactic core black hole mass density causes the recent passage from cosmic deceleration to acceleration. Finally, it is worth mentioning that this work corrects a wide spread fallacy among brane cosmologists, i.e. that escaping gravitons result in positive dark pressure.

  4. Mass-loading in Galactic Winds: the Role of Photoevaporation and Wind Ablation

    NASA Astrophysics Data System (ADS)

    Yeh, S. C. C.; Matzner, C. D.

    2012-09-01

    We present a dynamical scenario of instantaneous dense gas entrainment by stellar winds in a wind-dominated HII region. Stellar winds and radiation pressure will become more important in an HII region as the central star or cluster is sufficiently luminous, therefore the region is windswept instead of photoevaporation-dominated. In our model, a cloud is smaller than the region as a whole, hence its mass injection occurs through either ordinary photoevaporation or wind ablation. We predict that the instantaneous wind ablation will cause strong mixing between hot winds and warm gas, and the mass injection rate of the wind-confined photoevaporated flow is higher than that of the ionizing source.

  5. Tracing the Galactic Halo: Obtaining Bayesian mass estimates of the Galaxy in the presence of incomplete data

    NASA Astrophysics Data System (ADS)

    Eadie, Gwendolyn; Harris, William; Widrow, Lawrence; Springford, Aaron

    2016-08-01

    The mass and cumulative mass profile of the Galaxy are its most fundamental properties. Estimating these properties, however, is not a trivial problem. We rely on the kinematic information from Galactic satellites such as globular clusters and dwarf galaxies, and this data is incomplete and subject to measurement uncertainty. In particular, the complete 3D velocity vectors of objects are sometimes unavailable, and there may be selection biases due to both the distribution of objects around the Galaxy and our measurement position. On the other hand, the uncertainties of these data are fairly well understood. Thus, we would like to incorporate these uncertainties and the incomplete data into our estimate of the Milky Way's mass. The Bayesian paradigm offers a way to deal with both the missing kinematic data and measurement errors using a hierarchical model. An application of this method to the Milky Way halo mass profile, using the kinematic data for globular clusters and dwarf satellites, is shown.

  6. Galactic and stellar dynamics in the era of high resolution surveys

    NASA Astrophysics Data System (ADS)

    Boily, C. M.; Combes, F.; Hensler, G.; Spurzem, R.

    2008-12-01

    The conference Galactic and Stellar Dynamics in the Era of High Resolution Surveys took place at the European Doctoral College (EDC) in Strasbourg from 2008 March 16 to 20. The event was co-sponsored by the Astronomische Gesellschaft (AG) and the Société Fran\\c{c}aise d'Astronomie et d'Astrophysique (SF2A), a joint venture aiming to set a new trend of regular thematic meetings in specific areas of research. This special issue of the Astronomische Nachrichten is a compilation of the papers presented at the meeting. We give an outline of the meeting together with a short history of the relations of the two societies.

  7. A MULTIWAVELENGTH VIEW OF A MASS OUTFLOW FROM THE GALACTIC CENTER

    SciTech Connect

    Law, C. J.

    2010-01-01

    The Galactic center (GC) lobe is a degree-tall shell of gas that spans the central degree of our Galaxy. It has been cited as evidence for a mass outflow from our GC region, which has inspired diverse models for its origin. However, most work has focused on the morphology of the GC lobe, which has made it difficult to draw strong conclusions about its nature. Here, I present a coherent, multiwavelength analysis of new and archival observations of the GC lobe. New radio continuum observations show that the entire structure has a similar spectral index, indicating that it has a common origin. The radio continuum emission shows that the GC lobe has a magnetized layer with a diameter of 110 pc and an equipartition field strength ranging from 40 to 100 muG. I show that optical and radio recombination line emission are associated with the GC lobe and are consistent with being located in the GC region. The recombination line emission traces an ionized shell nested within the radio continuum with diameter of 80 pc and height 165 pc. Mid-infrared maps at 8 and 15 mum show that the GC lobe has a third layer of warm dust and polycyclic aromatic hydrocarbon-emission that surrounds the radio continuum shell with a diameter of 130 pc. Assuming adiabatic expansion of the gas in the GC lobe, its formation required an energy input of about 5 x 10{sup 52} ergs. I compare the physical conditions of the GC lobe to several models and find best agreement with the canonical starburst outflow model. The formation of the GC lobe is consistent with the currently observed pressure and star formation rate in the central tens of parsecs of our Galaxy. Outflows of this scale are more typical of dwarf galaxies and would not be easily detected in nearby spiral galaxies. Thus, the existence of such an outflow in our own Galaxy may indicate that it is a relatively common phenomenon in the nuclei of spiral galaxies.

  8. Galactic oscillator symmetry

    NASA Technical Reports Server (NTRS)

    Rosensteel, George

    1995-01-01

    Riemann ellipsoids model rotating galaxies when the galactic velocity field is a linear function of the Cartesian coordinates of the galactic masses. In nuclear physics, the kinetic energy in the linear velocity field approximation is known as the collective kinetic energy. But, the linear approximation neglects intrinsic degrees of freedom associated with nonlinear velocity fields. To remove this limitation, the theory of symplectic dynamical symmetry is developed for classical systems. A classical phase space for a self-gravitating symplectic system is a co-adjoint orbit of the noncompact group SP(3,R). The degenerate co-adjoint orbit is the 12 dimensional homogeneous space Sp(3,R)/U(3), where the maximal compact subgroup U(3) is the symmetry group of the harmonic oscillator. The Hamiltonian equations of motion on each orbit form a Lax system X = (X,F), where X and F are elements of the symplectic Lie algebra. The elements of the matrix X are the generators of the symplectic Lie algebra, viz., the one-body collective quadratic functions of the positions and momenta of the galactic masses. The matrix F is composed from the self-gravitating potential energy, the angular velocity, and the hydostatic pressure. Solutions to the hamiltonian dynamical system on Sp(3,R)/U(3) are given by symplectic isospectral deformations. The Casimirs of Sp(3,R), equal to the traces of powers of X, are conserved quantities.

  9. Upper limits to surface-force disturbances on LISA proof masses and the possibility of observing galactic binaries

    SciTech Connect

    Carbone, Ludovico; Ciani, Giacomo; Dolesi, Rita; Hueller, Mauro; Tombolato, David; Vitale, Stefano; Weber, William Joseph; Cavalleri, Antonella

    2007-02-15

    We have measured surface-force noise on a hollow replica of a LISA proof mass surrounded by its capacitive motion sensor. Forces are detected through the torque exerted on the proof mass by means of a torsion pendulum in the 0.1-30 mHz range. The sensor and electronics have the same design as for the flight hardware, including 4 mm gaps around the proof mass. The measured upper limit for forces would allow detection of a number of galactic binaries signals with signal-to-noise ratio up to {approx_equal}40 for 1 yr integration. We also discuss how LISA Pathfinder will substantially improve this limit, approaching the LISA performance.

  10. Dynamical equation of the effective gluon mass

    SciTech Connect

    Aguilar, A. C.; Binosi, D.; Papavassiliou, J.

    2011-10-15

    In this article, we derive the integral equation that controls the momentum dependence of the effective gluon mass in the Landau gauge. This is accomplished by means of a well-defined separation of the corresponding ''one-loop dressed'' Schwinger-Dyson equation into two distinct contributions, one associated with the mass and one with the standard kinetic part of the gluon. The entire construction relies on the existence of a longitudinally coupled vertex of nonperturbative origin, which enforces gauge invariance in the presence of a dynamical mass. The specific structure of the resulting mass equation, supplemented by the additional requirement of a positive-definite gluon mass, imposes a rather stringent constraint on the derivative of the gluonic dressing function, which is comfortably satisfied by the large-volume lattice data for the gluon propagator, both for SU(2) and SU(3). The numerical treatment of the mass equation, under some simplifying assumptions, is presented for the aforementioned gauge groups, giving rise to a gluon mass that is a nonmonotonic function of the momentum. Various theoretical improvements and possible future directions are briefly discussed.

  11. Dynamic Method for Identifying Collected Sample Mass

    NASA Technical Reports Server (NTRS)

    Carson, John

    2008-01-01

    G-Sample is designed for sample collection missions to identify the presence and quantity of sample material gathered by spacecraft equipped with end effectors. The software method uses a maximum-likelihood estimator to identify the collected sample's mass based on onboard force-sensor measurements, thruster firings, and a dynamics model of the spacecraft. This makes sample mass identification a computation rather than a process requiring additional hardware. Simulation examples of G-Sample are provided for spacecraft model configurations with a sample collection device mounted on the end of an extended boom. In the absence of thrust knowledge errors, the results indicate that G-Sample can identify the amount of collected sample mass to within 10 grams (with 95-percent confidence) by using a force sensor with a noise and quantization floor of 50 micrometers. These results hold even in the presence of realistic parametric uncertainty in actual spacecraft inertia, center-of-mass offset, and first flexibility modes. Thrust profile knowledge is shown to be a dominant sensitivity for G-Sample, entering in a nearly one-to-one relationship with the final mass estimation error. This means thrust profiles should be well characterized with onboard accelerometers prior to sample collection. An overall sample-mass estimation error budget has been developed to approximate the effect of model uncertainty, sensor noise, data rate, and thrust profile error on the expected estimate of collected sample mass.

  12. The dynamical mass of a classical Cepheid variable star in an eclipsing binary system.

    PubMed

    Pietrzyński, G; Thompson, I B; Gieren, W; Graczyk, D; Bono, G; Udalski, A; Soszyński, I; Minniti, D; Pilecki, B

    2010-11-25

    Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants-it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem, for which a solution is missing. An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15-30% (refs 6, 7), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts, no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Here we report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of 1% and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids. PMID:21107425

  13. Dissecting SUMO Dynamics by Mass Spectrometry.

    PubMed

    Drabikowski, Krzysztof; Dadlez, Michał

    2016-01-01

    Protein modification by SUMO proteins is one of the key posttranslational modifications in eukaryotes. Here, we describe a workflow to analyze SUMO dynamics in response to different stimuli, purify SUMO conjugates, and analyze the changes in SUMOylation level in organisms, tissues, or cell culture. We present a protocol for lysis in denaturing conditions that is compatible with downstream IMAC and antibody affinity purification, followed by mass spectrometry and data analysis. PMID:27613044

  14. Galactic Winds

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain

    Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

  15. THERMAL AND DYNAMICAL PROPERTIES OF GAS ACCRETING ONTO A SUPERMASSIVE BLACK HOLE IN AN ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Moscibrodzka, M.; Proga, D.

    2013-04-20

    We study stability of gas accretion in active galactic nuclei (AGNs). Our grid-based simulations cover a radial range from 0.1 to 200 pc, which may enable linking the galactic/cosmological simulations with small-scale black hole (BH) accretion models within a few hundreds of Schwarzschild radii. Here, as in previous studies by our group, we include gas radiative cooling as well as heating by a sub-Eddington X-ray source near the central supermassive BH of 10{sup 8} M{sub Sun }. Our theoretical estimates and simulations show that for the X-ray luminosity, L{sub X} {approx} 0.008 L{sub Edd}, the gas is thermally and convectively unstable within the computational domain. In the simulations, we observe that very tiny fluctuations in an initially smooth, spherically symmetric, accretion flow, grow first linearly and then nonlinearly. Consequently, an initially one-phase flow relatively quickly transitions into a two-phase/cold-hot accretion flow. For L{sub X} = 0.015 L{sub Edd} or higher, the cold clouds continue to accrete but in some regions of the hot phase, the gas starts to move outward. For L{sub X} < 0.015 L{sub Edd}, the cold phase contribution to the total mass accretion rate only moderately dominates over the hot phase contribution. This result might have some consequences for cosmological simulations of the so-called AGN feedback problem. Our simulations confirm the previous results of Barai et al. who used smoothed particle hydrodynamic (SPH) simulations to tackle the same problem. Here, however, because we use a grid-based code to solve equations in one dimension and two dimensions, we are able to follow the gas dynamics at much higher spacial resolution and for longer time compared with the three-dimensional SPH simulations. One of the new features revealed by our simulations is that the cold condensations in the accretion flow initially form long filaments, but at the later times, those filaments may break into smaller clouds advected outward within the

  16. On the Contribution of Gamma Ray Bursts to the Galactic Inventory of Some Intermediate Mass Nuclei

    SciTech Connect

    Pruet, J; Surman, R; McLaughlin, G C

    2004-01-23

    Light curves from a growing number of Gamma Ray Bursts (GRBs) indicate that GRBs copiously produce radioactive Ni moving outward at fractions of the speed of light. We calculate nuclear abundances of elements accompanying the outflowing Ni under the assumption that this Ni originates from a wind blown off of a viscous accretion disk. We also show that GRB's likely contribute appreciably to the galactic inventory of {sup 42}Ca, {sup 45}Sc, {sup 46}Ti, {sup 49}Ti, {sup 63}Cu, and may be an important site for the production of {sup 64}Zn.

  17. Another path for the emergence of modified galactic dynamics from dark matter superfluidity

    NASA Astrophysics Data System (ADS)

    Khoury, Justin

    2016-05-01

    In recent work we proposed a novel theory of dark matter (DM) superfluidity that matches the successes of the Λ CDM model on cosmological scales while simultaneously reproducing modified Newtonian dynamics (MOND) phenomenology on galactic scales. The agents responsible for mediating the MONDian force law are superfluid phonons that couple to ordinary (baryonic) matter. In this paper we propose an alternative way for the MOND phenomenon to emerge from DM superfluidity. The central idea is to use higher-gradient corrections in the superfluid effective theory. These next-to-leading order terms involve gradients of the gravitational potential, and therefore effectively modify the gravitational force law. In the process we discover a novel mechanism for generating the nonrelativistic MOND action, starting from a theory that is fully analytic in all field variables. The idea, inspired by the symmetron mechanism, uses the spontaneous breaking of a discrete symmetry. For large acceleration, the symmetry is unbroken and the action reduces to Einstein gravity. For small acceleration, the symmetry is spontaneously broken and the action reduces to MONDian gravity. Cosmologically, however, the Universe is always in the Einstein-gravity, symmetry-restoring phase. The expansion history and linear growth of density perturbations are therefore indistinguishable from Λ CDM cosmology.

  18. Single-epoch black hole mass estimators for broad-line active galactic nuclei: recalibrating Hβ with a new approach

    SciTech Connect

    Feng, Hua; Li, Hong; Shen, Yue

    2014-10-10

    Based on an updated Hβ reverberation mapping (RM) sample of 44 nearby active galactic nuclei (AGNs), we propose a novel approach for black hole (BH) mass estimation using two filtered luminosities computed from single-epoch (SE) AGN spectra around the Hβ region. We found that the two optimal-filter luminosities extract virial information (size and virial velocity of the broad-line region, BLR) from the spectra, justifying their usage in this empirical BH mass estimator. The major advantages of this new recipe over traditional SE BH mass estimators utilizing continuum luminosity and broad-line width are (1) it has a smaller intrinsic scatter of 0.28 dex calibrated against RM masses, (2) it is extremely simple to use in practice, without any need to decompose the spectrum, and (3) it produces unambiguous and highly repeatable results even with low signal-to-noise spectra. The combination of the two luminosities can also cancel out, to some extent, systematic luminosity errors potentially introduced by uncertainties in distance or flux calibration. In addition, we recalibrated the traditional SE mass estimators using broad Hβ FWHM and monochromatic continuum luminosity at 5100 Å (L {sub 5100}). We found that using the best-fit slopes on FWHM and L {sub 5100} (derived from fitting the BLR radius-luminosity relation and the correlation between rms line dispersion and SE FWHM, respectively) rather than simple assumptions (e.g., 0.5 for L {sub 5100} and 2 for FWHM) leads to more precise SE mass estimates, improving the intrinsic scatter from 0.41 dex to 0.36 dex with respect to the RM masses. We compared different estimators and discussed their applications to the Sloan Digital Sky Survey quasar sample. Due to the limitations of the current RM sample, application of any SE recipe calibrated against RM masses to distant quasars should be treated with caution.

  19. Evolution and Distribution of Magnetic Fields from Active Galactic Nuclei in Galaxy Clusters. II. The Effects of Cluster Size and Dynamical State

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Li, Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2011-10-01

    Theory and simulations suggest that magnetic fields from radio jets and lobes powered by their central super massive black holes can be an important source of magnetic fields in the galaxy clusters. This is Paper II in a series of studies where we present self-consistent high-resolution adaptive mesh refinement cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus. We studied 12 different galaxy clusters with virial masses ranging from 1 × 1014 to 2 × 1015 M sun. In this work, we examine the effects of the mass and merger history on the final magnetic properties. We find that the evolution of magnetic fields is qualitatively similar to those of previous studies. In most clusters, the injected magnetic fields can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process with hierarchical mergers, while the amplification history and the magnetic field distribution depend on the cluster formation and magnetism history. This can be very different for different clusters. The total magnetic energies in these clusters are between 4 × 1057 and 1061 erg, which is mainly decided by the cluster mass, scaling approximately with the square of the total mass. Dynamically older relaxed clusters usually have more magnetic fields in their ICM. The dynamically very young clusters may be magnetized weakly since there is not enough time for magnetic fields to be amplified.

  20. Dynamical generation of the top quark mass

    NASA Astrophysics Data System (ADS)

    Popovic, Marko Berislav

    2002-09-01

    I study new physics theories in which the observed mass of the heaviest elementary particle, the top quark, is a result of a dynamical mechanism at the subatomic level. The same mechanism needs to explain the transition of the effective physical description at the largest space-time scales to that at smaller scales. This large-scale description is characterized by non-zero masses for most of the elementary particles and the existence of the familiar electromagnetic interactions. The description at smaller space-time scales is characterized by the presence of a richer set of fundamental interactions, including weak and hypercharge interactions, as well as no masses for the particles. As a minimal consequence of this transition, particle theories commonly predict the existence of a still unobserved particle, called the Higgs, at the largest scales. New physics considered in this thesis includes the following: (1) Models with new fundamental interactions that select the top quark and give an exclusive role to its dynamical mass generation mechanism. I propose one such model, discuss current experimental constraints, and suggest future tests of this idea. (2) Models with new spin one-half particles, not sensitive to the weak interactions, that mix with ordinary particles, including the top quark. I discuss the phenomenology, i.e., analyze data from particle colliders, and set limits on the parameters of the models. (3) Models with new spin one-half particles, sensitive to the weak interactions, that mix with ordinary particles. I propose the model structure, discuss some of its phenomenology, and suggest further tests of this idea at linear particle accelerators. Finally, I analyze the connection between the Higgs mass (m H) and the space-time scale at which the above-mentioned transition occurs. Without introducing new physics at the smallest scales, I show that due to the very large top mass, the standard description with the Higgs particle fails at small scales

  1. Aero-Thermo-Dynamic Mass Analysis

    NASA Astrophysics Data System (ADS)

    Shiba, Kota; Yoshikawa, Genki

    2016-07-01

    Each gas molecule has its own molecular weight, while such a microscopic characteristic is generally inaccessible, and thus, it is measured indirectly through e.g. ionization in conventional mass analysis. Here, we present a novel approach to the direct measurement of molecular weight through a nanoarchitectonic combination of aerodynamics, thermodynamics, and mechanics, transducing microscopic events into macroscopic phenomena. It is confirmed that this approach can provide molecular weight of virtually any gas or vaporizable liquid sample in real-time without ionization. Demonstrations through analytical calculations, numerical simulations, and experiments verify the validity and versatility of the novel mass analysis realized by a simple setup with a flexible object (e.g. with a bare cantilever and even with a business card) placed in a laminar jet. Owing to its unique and simple working principle, this aero-thermo-dynamic mass analysis (AMA) can be integrated into various analytical devices, production lines, and consumer mobile platforms, opening new chapters in aerodynamics, thermodynamics, mechanics, and mass analysis.

  2. Aero-Thermo-Dynamic Mass Analysis.

    PubMed

    Shiba, Kota; Yoshikawa, Genki

    2016-01-01

    Each gas molecule has its own molecular weight, while such a microscopic characteristic is generally inaccessible, and thus, it is measured indirectly through e.g. ionization in conventional mass analysis. Here, we present a novel approach to the direct measurement of molecular weight through a nanoarchitectonic combination of aerodynamics, thermodynamics, and mechanics, transducing microscopic events into macroscopic phenomena. It is confirmed that this approach can provide molecular weight of virtually any gas or vaporizable liquid sample in real-time without ionization. Demonstrations through analytical calculations, numerical simulations, and experiments verify the validity and versatility of the novel mass analysis realized by a simple setup with a flexible object (e.g. with a bare cantilever and even with a business card) placed in a laminar jet. Owing to its unique and simple working principle, this aero-thermo-dynamic mass analysis (AMA) can be integrated into various analytical devices, production lines, and consumer mobile platforms, opening new chapters in aerodynamics, thermodynamics, mechanics, and mass analysis. PMID:27412335

  3. Aero-Thermo-Dynamic Mass Analysis

    PubMed Central

    Shiba, Kota; Yoshikawa, Genki

    2016-01-01

    Each gas molecule has its own molecular weight, while such a microscopic characteristic is generally inaccessible, and thus, it is measured indirectly through e.g. ionization in conventional mass analysis. Here, we present a novel approach to the direct measurement of molecular weight through a nanoarchitectonic combination of aerodynamics, thermodynamics, and mechanics, transducing microscopic events into macroscopic phenomena. It is confirmed that this approach can provide molecular weight of virtually any gas or vaporizable liquid sample in real-time without ionization. Demonstrations through analytical calculations, numerical simulations, and experiments verify the validity and versatility of the novel mass analysis realized by a simple setup with a flexible object (e.g. with a bare cantilever and even with a business card) placed in a laminar jet. Owing to its unique and simple working principle, this aero-thermo-dynamic mass analysis (AMA) can be integrated into various analytical devices, production lines, and consumer mobile platforms, opening new chapters in aerodynamics, thermodynamics, mechanics, and mass analysis. PMID:27412335

  4. THE BLACK HOLE-BULGE MASS RELATION OF ACTIVE GALACTIC NUCLEI IN THE EXTENDED CHANDRA DEEP FIELD-SOUTH SURVEY

    SciTech Connect

    Schramm, Malte; Silverman, John D.

    2013-04-10

    We present results from a study to determine whether relations-established in the local universe-between the mass of supermassive black holes (SMBHs) and their host galaxies are in place at higher redshifts. We identify a well-constructed sample of 18 X-ray-selected, broad-line active galactic nuclei (AGNs) in the Extended Chandra Deep Field-South Survey with 0.5 < z < 1.2. This redshift range is chosen to ensure that Hubble Space Telescope (HST) imaging is available with at least two filters that bracket the 4000 A break, thus providing reliable stellar mass estimates of the host galaxy by accounting for both young and old stellar populations. We compute single-epoch, virial black hole (BH) masses from optical spectra using the broad Mg II emission line. For essentially all galaxies in our sample, their total stellar mass content agrees remarkably well, given their BH masses, with local relations of inactive galaxies and active SMBHs. We further decompose the total stellar mass into bulge and disk components separately with full knowledge of the HST point-spread function. We find that {approx}80% of the sample is consistent with the local M{sub BH}-M{sub *,{sub Bulge}} relation even with 72% of the host galaxies showing the presence of a disk. In particular, bulge-dominated hosts are more aligned with the local relation than those with prominent disks. We further discuss the possible physical mechanisms that are capable of building up the stellar mass of the bulge from an extended disk of stars over the subsequent 8 Gyr.

  5. Reliable Identifications of Active Galactic Nuclei from the WISE, 2MASS, and ROSAT All-Sky Surveys

    NASA Astrophysics Data System (ADS)

    Edelson, R.; Malkan, M.

    2012-05-01

    We have developed the ''S IX'' statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3 m Kast spectroscopy. We find that sources with S IX < 0 have a gsim95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the ''W2R'' sample of 4316 sources with S IX < 0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J <~ 16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J < 14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg2, permitting construction of AGN samples in any sufficiently large region of sky.

  6. RELIABLE IDENTIFICATIONS OF ACTIVE GALACTIC NUCLEI FROM THE WISE, 2MASS, AND ROSAT ALL-SKY SURVEYS

    SciTech Connect

    Edelson, R.; Malkan, M.

    2012-05-20

    We have developed the ''S{sub IX}'' statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3 m Kast spectroscopy. We find that sources with S{sub IX} < 0 have a {approx}>95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the ''W2R'' sample of 4316 sources with S{sub IX} < 0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J {approx}< 16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J < 14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg{sup 2}, permitting construction of AGN samples in any sufficiently large region of sky.

  7. The VMC Survey. XVIII. Radial Dependence of the Low-mass, 0.55--0.82 M Stellar Mass Function in the Galactic Globular Cluster 47 Tucanae

    NASA Astrophysics Data System (ADS)

    Zhang, Chaoli; Li, Chengyuan; de Grijs, Richard; Bekki, Kenji; Deng, Licai; Zaggia, Simone; Rubele, Stefano; Piatti, Andrés E.; Cioni, Maria-Rosa L.; Emerson, Jim; For, Bi-Qing; Ripepi, Vincenzo; Marconi, Marcella; Ivanov, Valentin D.; Chen, Li

    2015-12-01

    We use near-infrared observations obtained as part of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Survey of the Magellanic Clouds (VMC), as well as two complementary Hubble Space Telescope (HST) data sets, to study the luminosity and mass functions (MFs) as a function of clustercentric radius of the main-sequence stars in the Galactic globular cluster 47 Tucanae. The HST observations indicate a relative deficit in the numbers of faint stars in the central region of the cluster compared with its periphery, for 18.75 ≤ mF606W ≤ 20.9 mag (corresponding to a stellar mass range of 0.55 < m*/M⊙ < 0.73). The stellar number counts at 6.‧7 from the cluster core show a deficit for 17.62 ≤ mF606W ≤ 19.7 mag (i.e., 0.65 < m*/M⊙ < 0.82), which is consistent with expectations from mass segregation. The VMC-based stellar MFs exhibit power-law shapes for masses in the range 0.55 < m*/M⊙ < 0.82. These power laws are characterized by an almost constant slope, α. The radial distribution of the power-law slopes α thus shows evidence of the importance of both mass segregation and tidal stripping, for both the first- and second-generation stars in 47 Tuc.

  8. Regulation of Star Formation Rates in Multiphase Galactic Disks: Numerical Tests of the Thermal/Dynamical Equilibrium Model

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Goo; Kim, Woong-Tae; Ostriker, Eve C.

    2011-12-01

    We use vertically resolved numerical hydrodynamic simulations to study star formation and the interstellar medium (ISM) in galactic disks. We focus on outer-disk regions where diffuse H I dominates, with gas surface densities Σ = 3-20 M⊙ pc-2 and star-plus-dark matter volume densities ρsd = 0.003-0.5 M⊙ pc-3. Star formation occurs in very dense, self-gravitating clouds that form by mergers of smaller cold cloudlets. Turbulence, driven by momentum feedback from supernova events, destroys bound clouds and puffs up the disk vertically. Time-dependent radiative heating (FUV from recent star formation) offsets gas cooling. We use our simulations to test a new theory for self-regulated star formation. Consistent with this theory, the disks evolve to a state of vertical dynamical equilibrium and thermal equilibrium with both warm and cold phases. The range of star formation surface densities and midplane thermal pressures is ΣSFR ∼ 10-4 to 10-2 M⊙ kpc-2 yr-1 and P th/k B ∼ 102 to 104 cm-3 K. In agreement with observations, turbulent velocity dispersions are ~7 km s-1 and the ratio of the total (effective) to thermal pressure is Ptot/Pth ∼ 4-5, across this whole range (provided shielding is similar to the solar neighborhood). We show that ΣSFR is not well correlated with Σ alone, but rather with Σ ρsd1/2, because the vertical gravity from stars and dark matter dominates in outer disks. We also find that ΣSFR has a strong, nearly linear correlation with Ptot, which itself is within ~13% of the dynamical equilibrium estimate Ptot, DE. The quantitative relationships we find between &SigmaSFR and the turbulent and thermal pressures show that star formation is highly efficient for energy and momentum production, in contrast to the low efficiency of mass consumption. Star formation rates adjust until the ISM's energy and momentum losses are replenished by feedback within a dynamical time.

  9. ULTRAVIOLET EMISSION-LINE CORRELATIONS IN HST/COS SPECTRA OF ACTIVE GALACTIC NUCLEI: SINGLE-EPOCH BLACK HOLE MASSES

    SciTech Connect

    Tilton, Evan M.; Shull, J. Michael E-mail: michael.shull@colorado.edu

    2013-09-01

    Effective methods of measuring supermassive black hole masses in active galactic nuclei (AGNs) are of critical importance to studies of galaxy evolution. While there has been much success in obtaining masses through reverberation mapping, the extensive observing time required by this method has limited the practicality of applying it to large samples at a variety of redshifts. This limitation highlights the need to estimate these masses using single-epoch spectroscopy of ultraviolet (UV) emission lines. We use UV spectra of 44 AGNs from HST/COS, the International Ultraviolet Explorer, and the Far Ultraviolet Spectroscopic Explorer of the C IV {lambda}1549, O VI {lambda}1035, O III] {lambda}1664, He II {lambda}1640, C II {lambda}1335, and Mg II {lambda}2800 emission lines and explore their potential as tracers of the broad-line region and supermassive black hole mass. The higher signal-to-noise ratio and better spectral resolution of the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) resolve AGN intrinsic absorption and produce more accurate line widths. From these, we test the viability of mass-scaling relationships based on line widths and luminosities and carry out a principal component analysis based on line luminosities, widths, skewness, and kurtosis. At L{sub 1450} {<=} 10{sup 45} erg s{sup -1}, the UV line luminosities correlate well with H{beta}, as does the 1450 A continuum luminosity. We find that C IV, O VI, and Mg II can be used as reasonably accurate estimators of AGN black hole masses, while He II and C II are uncorrelated.

  10. FUNDAMENTAL PARAMETERS, INTEGRATED RED GIANT BRANCH MASS LOSS, AND DUST PRODUCTION IN THE GALACTIC GLOBULAR CLUSTER 47 TUCANAE

    SciTech Connect

    McDonald, I.; Zijlstra, A. A.; Boyer, M. L.; Gordon, K.; Meixner, M.; Sewilo, M.; Shiao, B.; Whitney, B.; Van Loon, J. Th.; Hora, J. L.; Robitaille, T.; Babler, B.; Meade, M.; Block, M.; Misselt, K.

    2011-04-01

    Fundamental parameters and time evolution of mass loss are investigated for post-main-sequence stars in the Galactic globular cluster 47 Tucanae (NGC 104). This is accomplished by fitting spectral energy distributions (SEDs) to existing optical and infrared photometry and spectroscopy, to produce a true Hertzsprung-Russell diagram. We confirm the cluster's distance as d = 4611{sup +213}{sub -200} pc and age as 12 {+-} 1 Gyr. Horizontal branch models appear to confirm that no more red giant branch mass loss occurs in 47 Tuc than in the more metal-poor {omega} Centauri, though difficulties arise due to inconsistencies between the models. Using our SEDs, we identify those stars that exhibit infrared excess, finding excess only among the brightest giants: dusty mass loss begins at a luminosity of {approx}1000 L{sub sun}, becoming ubiquitous above L = 2000 L{sub sun}. Recent claims of dust production around lower-luminosity giants cannot be reproduced, despite using the same archival Spitzer imagery.

  11. A COMPARATIVE ANALYSIS OF VIRIAL BLACK HOLE MASS ESTIMATES OF MODERATE-LUMINOSITY ACTIVE GALACTIC NUCLEI USING SUBARU/FMOS

    SciTech Connect

    Matsuoka, K.; Silverman, J. D.; Schramm, M.; Steinhardt, C. L.; Nagao, T.; Kartaltepe, J.; Sanders, D. B.; Hasinger, G.; Treister, E.; Akiyama, M.; Ohta, K.; Ueda, Y.; Bongiorno, A.; Brandt, W. N.; Brusa, M.; Capak, P.; Comastri, A.; Lilly, S. J.; and others

    2013-07-01

    We present an analysis of broad emission lines observed in moderate-luminosity active galactic nuclei (AGNs), typical of those found in X-ray surveys of deep fields, with the goal of testing the validity of single-epoch virial black hole mass estimates. We have acquired near-infrared spectra of AGNs up to z {approx} 1.8 in the COSMOS and Extended Chandra Deep Field-South Survey, with the Fiber Multi-Object Spectrograph mounted on the Subaru telescope. These near-infrared spectra provide a significant detection of the broad H{alpha} line, shown to be a reliable probe of black hole mass at low redshift. Our sample has existing optical spectroscopy that provides a detection of Mg II, typically used for black hole mass estimation at z {approx}> 1. We carry out a spectral-line fitting procedure using both H{alpha} and Mg II to determine the virial velocity of gas in the broad-line region, the continuum luminosity at 3000 A, and the total H{alpha} line luminosity. With a sample of 43 AGNs spanning a range of two decades in luminosity, we find a tight correlation between the ultraviolet and emission-line luminosity. There is also a close one-to-one relationship between the full width at half-maximum of H{alpha} and Mg II. Both of these then lead to there being very good agreement between H{alpha}- and Mg II-based masses over a wide range in black hole mass, i.e., M{sub BH} {approx} 10{sup 7-9} M{sub Sun }. In general, these results demonstrate that local scaling relations, using Mg II or H{alpha}, are applicable for AGNs at moderate luminosities and up to z {approx} 2.

  12. A dynamical study of Galactic globular clusters under different relaxation conditions

    NASA Astrophysics Data System (ADS)

    Zocchi, A.; Bertin, G.; Varri, A. L.

    2012-03-01

    Aims: We perform a systematic combined photometric and kinematic analysis of a sample of globular clusters under different relaxation conditions, based on their core relaxation time (as listed in available catalogs), by means of two well-known families of spherical stellar dynamical models. Systems characterized by shorter relaxation time scales are expected to be better described by isotropic King models, while less relaxed systems might be interpreted by means of non-truncated, radially-biased anisotropic f(ν) models, originally designed to represent stellar systems produced by a violent relaxation formation process and applied here for the first time to the study of globular clusters. Methods: The comparison between dynamical models and observations is performed by fitting simultaneously surface brightness and velocity dispersion profiles. For each globular cluster, the best-fit model in each family is identified, along with a full error analysis on the relevant parameters. Detailed structural properties and mass-to-light ratios are also explicitly derived. Results: We find that King models usually offer a good representation of the observed photometric profiles, but often lead to less satisfactory fits to the kinematic profiles, independently of the relaxation condition of the systems. For some less relaxed clusters, f(ν) models provide a good description of both observed profiles. Some derived structural characteristics, such as the total mass or the half-mass radius, turn out to be significantly model-dependent. The analysis confirms that, to answer some important dynamical questions that bear on the formation and evolution of globular clusters, it would be highly desirable to acquire larger numbers of accurate kinematic data-points, well distributed over the cluster field. Appendices are available in electronic form at http://www.aanda.org

  13. Intermediate-mass black holes from Population III remnants in the first galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ryu, Taeho; Tanaka, Takamitsu L.; Perna, Rosalba; Haiman, Zoltán

    2016-08-01

    We report the formation of intermediate-mass black holes (IMBHs) in suites of numerical N-body simulations of Population III remnant black holes (BHs) embedded in gas-rich protogalaxies at redshifts z ≳ 10. We model the effects of gas drag on the BHs' orbits, and allow BHs to grow via gas accretion, including a mode of hyper-Eddington accretion in which photon trapping and rapid gas inflow suppress any negative radiative feedback. Most initial BH configurations lead to the formation of one (but never more than one) IMBH in the centre of the protogalaxy, reaching a mass of 103-5 M⊙ through hyper-Eddington growth. Our results suggest a viable pathway to forming the earliest massive BHs in the centres of early galaxies. We also find that the nuclear IMBH typically captures a stellar-mass BH companion, making these systems observable in gravitational waves as extreme mass-ratio inspirals with eLISA.

  14. THE MASS-INDEPENDENCE OF SPECIFIC STAR FORMATION RATES IN GALACTIC DISKS

    SciTech Connect

    Abramson, Louis E.; Gladders, Michael D.; Kelson, Daniel D.; Dressler, Alan; Oemler, Augustus Jr.; Poggianti, Bianca; Vulcani, Benedetta

    2014-04-20

    The slope of the star formation rate/stellar mass relation (the SFR {sup M}ain Sequence{sup ;} SFR-M {sub *}) is not quite unity: specific star formation rates (SFR/M {sub *}) are weakly but significantly anti-correlated with M {sub *}. Here we demonstrate that this trend may simply reflect the well-known increase in bulge mass-fractions—portions of a galaxy not forming stars—with M {sub *}. Using a large set of bulge/disk decompositions and SFR estimates derived from the Sloan Digital Sky Survey, we show that re-normalizing SFR by disk stellar mass (sSFR{sub disk} ≡ SFR/M {sub *,} {sub disk}) reduces the M {sub *} dependence of SF efficiency by ∼0.25 dex per dex, erasing it entirely in some subsamples. Quantitatively, we find log sSFR{sub disk}-log M {sub *} to have a slope β{sub disk} in [ – 0.20, 0.00] ± 0.02 (depending on the SFR estimator and Main Sequence definition) for star-forming galaxies with M {sub *} ≥ 10{sup 10} M {sub ☉} and bulge mass-fractions B/T ≲ 0.6, generally consistent with a pure-disk control sample (β{sub control} = –0.05 ± 0.04). That (SFR/M {sub *,} {sub disk}) is (largely) independent of host mass for star-forming disks has strong implications for aspects of galaxy evolution inferred from any SFR-M {sub *} relation, including manifestations of ''mass quenching'' (bulge growth), factors shaping the star-forming stellar mass function (uniform dlog M {sub *}/dt for low-mass, disk-dominated galaxies), and diversity in star formation histories (dispersion in SFR(M {sub *}, t)). Our results emphasize the need to treat galaxies as composite systems—not integrated masses—in observational and theoretical work.

  15. APOGEE Chemical Tagging Constraint on the Maximum Star Cluster Mass in the Alpha-enhanced Galactic Disk

    NASA Astrophysics Data System (ADS)

    Ting, Yuan-Sen; Conroy, Charlie; Rix, Hans-Walter

    2016-01-01

    Stars born from the same molecular cloud should be nearly homogeneous in their element abundances. The concept of chemical tagging is to identify members of disrupted clusters by their clustering in element abundance space. Chemical tagging requires large samples of stars with precise abundances for many individual elements. With uncertainties of {σ }[X/{{Fe}]} and {σ }[{Fe/{{H}}]}≃ 0.05 for 10 elements measured for \\gt {10}4 stars, the APOGEE DR12 spectra may be the first well-suited data set to put this idea into practice. We find that even APOGEE data offer only ˜500 independent volume elements in the 10-dimensional abundance space, when we focus on the α-enhanced Galactic disk. We develop and apply a new algorithm to search for chemically homogeneous sets of stars against a dominant background. By injecting star clusters into the APOGEE data set, we show that chemically homogeneous clusters with masses ≳ 3× {10}7 {M}⊙ would be easily detectable and yet no such signal is seen in the data. By generalizing this approach, we put a first abundance-based constraint on the cluster mass function for the old disk stars in the Milky Way.

  16. Chandra and MMT observations of low-mass black hole active galactic nuclei accreting at low rates in dwarf galaxies

    SciTech Connect

    Yuan, W.; Zhou, H.; Dou, L.; Dong, X.-B.; Wang, T.-G.; Fan, X.

    2014-02-10

    We report on Chandra X-ray observations of four candidate low-mass black hole (M {sub bh} ≲ 10{sup 6} M {sub ☉}) active galactic nuclei (AGNs) that have the estimated Eddington ratios among the lowest (∼10{sup –2}) found for this class. The aims are to validate the nature of their AGNs and to confirm the low Eddington ratios that are derived from the broad Hα line, and to explore this poorly studied regime in the AGN parameter space. Among them, two objects with the lowest significance of the broad lines are also observed with the Multi-Mirror Telescope, and the high-quality optical spectra taken confirm them as Seyfert 1 AGNs and as having small black hole masses. X-ray emission is detected from the nuclei of two of the galaxies, which is variable on timescales of ∼10{sup 3} s, whereas no significant (or only marginal at best) detection is found for the remaining two. The X-ray luminosities are on the order of 10{sup 41} erg s{sup –1} or even lower, on the order of 10{sup 40} erg s{sup –1} for non-detections, which are among the lowest regimes ever probed for Seyfert galaxies. The low X-ray luminosities, compared to their black hole masses derived from Hα, confirm their low accretion rates assuming typical bolometric corrections. Our results hint at the existence of a possibly large population of under-luminous low-mass black holes in the local universe. An off-nucleus ultra-luminous X-ray source in one of the dwarf galaxies is detected serendipitously, with a luminosity (6-9)× 10{sup 39} erg s{sup –1} in 2-10 keV.

  17. Active galactic nuclei at z ˜ 1.5: II. Black Hole Mass estimation by means of broad emission lines

    NASA Astrophysics Data System (ADS)

    Mejia-Restrepo, J. E.; Trakhtenbrot, B.; Lira, P.; Netzer, H.; Capellupo, D. M.

    2016-03-01

    This is the second in a series of papers aiming to test how the mass (MBH), accretion rate (dot{M}) and spin (a★) of super massive black holes (SMBHs) determine the observed properties of type-I active galactic nuclei (AGN). Our project utilizes a sample of 39 unobscured AGN at z ≃ 1.55 observed by VLT/X-shooter, selected to map a large range in MBH and L/LEddand covers the most prominent UV-optical (broad) emission lines, including Hα, Hβ, Mg II λ2798, and C IV λ1549. This paper focuses on single-epoch, "virial" MBH determinations from broad emission lines and examine the implications of different continuum modeling approaches in line width measurements. We find that using a local power-law continuum instead of a physically-motivated thin disk continuum leads to only slight underestimation of the FWHM of the lines and the associated MBH(FWHM). However, the line dispersion σline and associated MBH(σline) are strongly affected by the continuum placement and provides less reliable mass estimates than FWHM-based methods. Our analysis shows that Hα, Hβ and Mg II can be safely used for virial MBH estimation. The C IV line, on the other hand, is not reliable in the majority of the cases, this may indicate that the gas emitting this line is not virialized. While Hα and Hβ show very similar line widths, the mean FWHM(Mg II) is about 30% narrower than FWHM(Hβ). We confirm several recent suggestions to improve the accuracy in C IV-based mass estimates, relying on other UV emission lines. Such improvements do not reduce the scatter between C IV-based and Balmer-line-based mass estimates.

  18. Active galactic nuclei at z ˜ 1.5 - II. Black hole mass estimation by means of broad emission lines

    NASA Astrophysics Data System (ADS)

    Mejía-Restrepo, J. E.; Trakhtenbrot, B.; Lira, P.; Netzer, H.; Capellupo, D. M.

    2016-07-01

    This is the second in a series of papers aiming to test how the mass (MBH), accretion rate (Ṁ) and spin (a*) of supermassive black holes (SMBHs) determine the observed properties of type I active galactic nuclei (AGN). Our project utilizes a sample of 39 unobscured AGN at z ≃ 1.55 observed by Very Large Telescope/X-Shooter, selected to map a large range in MBH and L/LEdd and covers the most prominent UV-optical (broad) emission lines, including Hα, Hβ, Mg II λ2798 and C IV λ1549. This paper focuses on single-epoch, `virial' MBH determinations from broad emission lines and examines the implications of different continuum modelling approaches in line width measurements. We find that using a local power-law continuum instead of a physically motivated thin disc continuum leads to only slight underestimation of the full width at half-maximum (FWHM) of the lines and the associated MBH(FWHM). However, the line dispersion σline and associated MBH(σline) are strongly affected by the continuum placement and provides less reliable mass estimates than FWHM-based methods. Our analysis shows that Hα, Hβ and Mg II can be safely used for virial MBH estimation. The C IV line, on the other hand, is not reliable in the majority of the cases; this may indicate that the gas emitting this line is not virialized. While Hα and Hβ show very similar line widths, the mean FWHM(Mg II) is about 30 per cent narrower than FWHM(Hβ). We confirm several recent suggestions to improve the accuracy in C IV-based mass estimates, relying on other UV emission lines. Such improvements do not reduce the scatter between C IV-based and Balmer-line-based mass estimates.

  19. Dynamics of Line-driven Disk Winds in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Proga, Daniel; Stone, James M.; Kallman, Timothy R.

    2000-11-01

    We present the results of axisymmetric time-dependent hydrodynamic calculations of line-driven winds from accretion disks in active galactic nuclei (AGNs). We assume the disk is flat, Keplerian, geometrically thin, and optically thick, radiating according to the α-disk prescription. The central engine of the AGN is a source of both ionizing X-rays and wind-driving UV photons. To calculate the radiation force, we take into account radiation from the disk and the central engine. The gas temperature and ionization state in the wind are calculated self-consistently from the photoionization and heating rate of the central engine. We find that a disk accreting onto a 108 Msolar black hole at the rate of 1.8 Msolar yr-1 can launch a wind at ~1016 cm from the central engine. The X-rays from the central object are significantly attenuated by the disk atmosphere so they cannot prevent the local disk radiation from pushing matter away from the disk. However, in the supersonic portion of the flow high above the disk, the X-rays can overionize the gas and decrease the wind terminal velocity. For a reasonable X-ray opacity, e.g., κX=40 g-1 cm2, the disk wind can be accelerated by the central UV radiation to velocities of up to 15,000 km s-1 at a distance of ~1017 cm from the central engine. The covering factor of the disk wind is ~0.2. The wind is unsteady and consists of an opaque, slow vertical flow near the disk that is bounded on the polar side by a high-velocity stream. A typical column density through the fast stream is a few times 1023 cm-2 so the stream is optically thin to the UV radiation. This low column density is precisely why gas can be accelerated to high velocities. The fast stream contributes nearly 100% to the total wind mass-loss rate of 0.5 Msolar yr-1.

  20. Three-dimensional Stellar Kinematics at the Galactic Center: Measuring the Nuclear Star Cluster Spatial Density Profile, Black Hole Mass, and Distance

    NASA Astrophysics Data System (ADS)

    Do, T.; Martinez, G. D.; Yelda, S.; Ghez, A.; Bullock, J.; Kaplinghat, M.; Lu, J. R.; Peter, A. H. G.; Phifer, K.

    2013-12-01

    We present three-dimensional (3D) kinematic observations of stars within the central 0.5 pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface density profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial density profile, cluster velocity anisotropy, black hole mass (M BH), and distance to the Galactic center (R 0) simultaneously. We find that the inner stellar density profile of the late-type stars, ρ(r)vpropr -γ, have a power law slope \\gamma =0.05_{-0.60}^{+0.29}, much more shallow than the frequently assumed Bahcall-Wolf slope of γ = 7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M_{BH}=5.76_{-1.26}^{+1.76}\\times 10^6 M ⊙ and R_0=8.92_{-0.55}^{+0.58} kpc is consistent with that derived from stellar orbits within 1'' of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R 0 is reduced by 30% (8.46_{-0.38}^{+0.42}\\ kpc). We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R 0.

  1. The Galactic Nucleus

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio

    Exciting new broadband observations of the galactic nucleus have placed the heart of the Milky Way under intense scrutiny in recent years. This has been due in part to the growing interest from theorists motivated to study the physics of black hole accretion, magnetized gas dynamics, and unusual star formation. The center of our Galaxy is now known to harbor the most compelling supermassive black hole candidate, weighing in at 3-4 million solar masses. Its nearby environment is comprised of a molecular dusty ring, clusters of evolved and young stars, diffuse hot gas, ionized gas streamers, and several supernova remnants. This chapter will focus on the physical makeup of this dynamic region and the feasibility of actually imaging the black hole's shadow in the coming decade with mm interferometry.

  2. Intermediate-mass black holes from Population III remnants in the first galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ryu, Taeho; Tanaka, Takamitsu L.; Perna, Rosalba; Haiman, Zoltán

    2016-08-01

    We report the formation of intermediate-mass black holes (IMBHs) in suites of numerical $N$-body simulations of Population III remnant black holes (BHs) embedded in gas-rich protogalaxies at redshifts $z\\gtrsim10$. We model the effects of gas drag on the BHs' orbits, and allow BHs to grow via gas accretion, including a mode of hyper-Eddington accretion in which photon trapping and rapid gas inflow suppress any negative radiative feedback. Most initial BH configurations lead to the formation of one (but never more than one) IMBH in the center of the protogalaxy, reaching a mass of $10^{3-5}\\mathrm{M}_{\\odot}$ through hyper-Eddington growth. Our results suggest a viable pathway to forming the earliest massive BHs in the centers of early galaxies. We also find that the nuclear IMBH typically captures a stellar-mass BH companion, making these systems observable in gravitational waves as extreme mass-ratio inspirals (EMRIs) with \\textit{eLISA}.

  3. Non-thermal insights on mass and energy flows through the Galactic Centre and into the Fermi bubbles

    NASA Astrophysics Data System (ADS)

    Crocker, R. M.

    2012-07-01

    We construct a simple model of the star-formation- (and resultant supernova-) driven mass and energy flows through the inner ˜200 pc (in diameter) of the Galaxy. Our modelling is constrained, in particular, by the non-thermal radio continuum and γ-ray signals detected from the region. The modelling points to a current star formation rate of 0.04-0.12 M⊙ yr-1 at 2σ confidence within the region with best-fitting value in the range 0.08-0.12 M⊙ yr-1 which - if sustained over 10 Gyr - would fill out the ˜109 M⊙ stellar population of the nuclear bulge. Mass is being accreted on to the Galactic Centre (GC) region at a rate ? yr-1. The region's star formation activity drives an outflow of plasma, cosmic rays and entrained, cooler gas. Neither the plasma nor the entrained gas reaches the gravitational escape speed, however, and all this material fountains back on to the inner Galaxy. The system we model can naturally account for the recently observed ≳106 M⊙'halo' of molecular gas surrounding the Central Molecular Zone out to 100-200 pc heights. The injection of cooler, high-metallicity material into the Galactic halo above the GC may catalyze the subsequent cooling and condensation of hot plasma out of this region and explain the presence of relatively pristine, nuclear-unprocessed gas in the GC. This process may also be an important ingredient in understanding the long-term stability of the GC star formation rate. The plasma outflow from the GC reaches a height of a few kpc and is compellingly related to the recently discovered Fermi bubbles by a number of pieces of evidence. These include that the outflow advects precisely (i) the power in cosmic rays required to sustain the bubbles'γ-ray luminosity in saturation; (ii) the hot gas required to compensate for gas cooling and drop-out from the bubbles and (iii) the magnetic field required to stabilize the walls of these structures. Our modelling demonstrates that ˜109 M⊙ of hot gas is processed through

  4. A Robust Measurement of the Mass Outflow Rate of the Galactic Outflow from NGC 6090

    NASA Astrophysics Data System (ADS)

    Chisholm, John; Tremonti, Christy A.; Leitherer, Claus; Chen, Yanmei

    2016-08-01

    To evaluate the impact of stellar feedback, it is critical to estimate the mass outflow rates of galaxies. Past estimates have been plagued by uncertain assumptions about the outflow geometry, metallicity, and ionization fraction. Here we use Hubble Space Telescope ultraviolet spectroscopic observations of the nearby starburst NGC 6090 to demonstrate that many of these quantities can be constrained by the data. We use the Si IV absorption lines to calculate the scaling of velocity (v), covering fraction (Cf), and density with distance from the starburst (r), assuming the Sobolev optical depth and a velocity law of the form: v~∝(1 - Ri/r)β (where Ri is the inner outflow radius). We find that the velocity (β=0.43) is consistent with an outflow driven by an r-2 force with the outflow radially accelerated, while the scaling of the covering fraction (Cf∝r-0.82) suggests that cool clouds in the outflow are in pressure equilibrium with an adiabatically expanding medium. We use the column densities of four weak metal lines and CLOUDY photoionization models to determine the outflow metallicity, the ionization correction, and the initial density of the outflow. Combining these values with the profile fitting, we find Ri = 63 pc, with most of the mass within 300 pc of the starburst. Finally, we find that the maximum mass outflow rate is 2.3 M⊙ yr-1 and the mass loading factor (outflow divided by the star formation rate) is 0.09, a factor of 10 lower than the value calculated using common assumptions for the geometry, metallicity and ionization structure of the outflow.

  5. The Arches cluster out to its tidal radius: dynamical mass segregation and the effect of the extinction law on the stellar mass function

    NASA Astrophysics Data System (ADS)

    Habibi, M.; Stolte, A.; Brandner, W.; Hußmann, B.; Motohara, K.

    2013-08-01

    The Galactic center is the most active site of star formation in the Milky Way, where particularly high-mass stars have formed very recently and are still forming today. However, since we are looking at the Galactic center through the Galactic disk, knowledge of extinction is crucial when studying this region. The Arches cluster is a young, massive starburst cluster near the Galactic center. We observed the Arches cluster out to its tidal radius using Ks-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. We show 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, we show that the difference can reach up to 30% for individually derived stellar masses and ΔAKs ~ 1 magnitude in acquired Ks-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 increases from a flat slope of αNishi = -1.50 ± 0.35 in the core (r < 0.2 pc) to αNishi = -2.21 ± 0.27 in the intermediate annulus (0.2 < r < 0.4 pc), where the Salpeter slope is -2.3. The mass function steepens to αNishi = -3.21 ± 0.30 in the outer annulus (0.4 < r < 1.5 pc), indicating that the outer cluster region is depleted of high-mass stars. This picture is consistent with mass segregation owing to the dynamical evolution of the cluster. Based on observations collected at the ESO/VLT under Program ID 081.D-0572(B) (PI: Brandner) and ID 71.C-0344(A) (PI: Eisenhauer, retrieved from the ESO archive). Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.Full Table 5 is

  6. ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION RATE, SPECIFIC STAR FORMATION RATE, AND THE PRESENCE OF ACTIVE GALACTIC NUCLEI FOR HIGH STELLAR MASS AND LOW STELLAR MASS GALAXIES

    SciTech Connect

    Deng Xinfa; Song Jun; Chen Yiqing; Jiang Peng; Ding Yingping

    2012-07-10

    Using two volume-limited main galaxy samples of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), we explore the environmental dependence of the star formation rate (SFR), specific star formation rate (SSFR), and the presence of active galactic nuclei (AGNs) for high stellar mass (HSM) and low stellar mass (LSM) galaxies. It is found that the environmental dependence of the SFR and SSFR for luminous HSM galaxies and faint LSM ones remains very strong: galaxies in the lowest density regime preferentially have higher SFR and SSFR than galaxies in the densest regime, while the environmental dependence of the SFR and SSFR for luminous LSM galaxies is substantially reduced. Our result also shows that the fraction of AGNs in HSM galaxies decreases as a function of density, while the one in LSM galaxies depends very little on local density. In the faint LSM galaxy sample, the SFR and SSFR of galaxies strongly decrease with increasing density, but the fraction of AGNs depends very little on local density. Such a result can rule out that AGNs are fueled by the cold gas in the disk component of galaxies that is also driving the star formation of those galaxies.

  7. The old nuclear star cluster in the Milky Way: dynamics, mass, statistical parallax, and black hole mass

    NASA Astrophysics Data System (ADS)

    Chatzopoulos, S.; Fritz, T. K.; Gerhard, O.; Gillessen, S.; Wegg, C.; Genzel, R.; Pfuhl, O.

    2015-02-01

    We derive new constraints on the mass, rotation, orbit structure, and statistical parallax of the Galactic old nuclear star cluster and the mass of the supermassive black hole. We combine star counts and kinematic data from Fritz et al., including 2500 line-of-sight velocities and 10 000 proper motions obtained with VLT instruments. We show that the difference between the proper motion dispersions σl and σb cannot be explained by rotation, but is a consequence of the flattening of the nuclear cluster. We fit the surface density distribution of stars in the central 1000 arcsec by a superposition of a spheroidal cluster with scale ˜100 arcsec and a much larger nuclear disc component. We compute the self-consistent two-integral distribution function f(E, Lz) for this density model, and add rotation self-consistently. We find that (i) the orbit structure of the f(E, Lz) gives an excellent match to the observed velocity dispersion profiles as well as the proper motion and line-of-sight velocity histograms, including the double-peak in the vl-histograms. (ii) This requires an axial ratio near q1 = 0.7 consistent with our determination from star counts, q1 = 0.73 ± 0.04 for r < 70 arcsec. (iii) The nuclear star cluster is approximately described by an isotropic rotator model. (iv) Using the corresponding Jeans equations to fit the proper motion and line-of-sight velocity dispersions, we obtain best estimates for the nuclear star cluster mass, black hole mass, and distance M*(r < 100 arcsec) = (8.94 ± 0.31|stat ± 0.9|syst) × 106 M⊙, M• = (3.86 ± 0.14|stat ± 0.4|syst) × 106 M⊙, and R0 = 8.27 ± 0.09|stat ± 0.1|syst kpc, where the estimated systematic errors account for additional uncertainties in the dynamical modelling. (v) The combination of the cluster dynamics with the S-star orbits around Sgr A* strongly reduces the degeneracy between black hole mass and Galactic Centre distance present in previous S-star studies. A joint statistical analysis with the

  8. An empirical mass-loss law for Population II giants from the Spitzer-IRAC survey of Galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Origlia, L.; Ferraro, F. R.; Fabbri, S.; Fusi Pecci, F.; Dalessandro, E.; Rich, R. M.; Valenti, E.

    2014-04-01

    Aims: The main aim of the present work is to derive an empirical mass-loss (ML) law for Population II stars in first and second ascent red giant branches. Methods: We used the Spitzer InfraRed Array Camera (IRAC) photometry obtained in the 3.6-8 μm range of a carefully chosen sample of 15 Galactic globular clusters spanning the entire metallicity range and sampling the vast zoology of horizontal branch (HB) morphologies. We complemented the IRAC photometry with near-infrared data to build suitable color-magnitude and color-color diagrams and identify mass-losing giant stars. Results: We find that while the majority of stars show colors typical of cool giants, some stars show an excess of mid-infrared light that is larger than expected from their photospheric emission and that is plausibly due to dust formation in mass flowing from them. For these stars, we estimate dust and total (gas + dust) ML rates and timescales. We finally calibrate an empirical ML law for Population II red and asymptotic giant branch stars with varying metallicity. We find that at a given red giant branch luminosity only a fraction of the stars are losing mass. From this, we conclude that ML is episodic and is active only a fraction of the time, which we define as the duty cycle. The fraction of mass-losing stars increases by increasing the stellar luminosity and metallicity. The ML rate, as estimated from reasonable assumptions for the gas-to-dust ratio and expansion velocity, depends on metallicity and slowly increases with decreasing metallicity. In contrast, the duty cycle increases with increasing metallicity, with the net result that total ML increases moderately with increasing metallicity, about 0.1 M⊙ every dex in [Fe/H]. For Population II asymptotic giant branch stars, we estimate a total ML of ≤0.1 M⊙, nearly constant with varying metallicity. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory

  9. Galactic Cosmic Ray Intensity Response to Interplanetary Coronal Mass Ejections/Magnetic Clouds in 1995-2009

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Cane, H. V.

    2011-01-01

    We summarize the response of the galactic cosmic ray (CGR) intensity to the passage of the more than 300 interplanetary coronal mass ejections (ICMEs) and their associated shocks that passed the Earth during 1995-2009, a period that encompasses the whole of Solar Cycle 23. In approx.80% of cases, the GCR intensity decreased during the passage of these structures, i.e., a "Forbush decrease" occurred, while in approx.10% there was no significant change. In the remaining cases, the GCR intensity increased. Where there was an intensity decrease, minimum intensity was observed inside the ICME in approx.90% of these events. The observations confirm the role of both post-shock regions and ICMEs in the generation of these decreases, consistent with many previous studies, but contrary to the conclusion of Reames, Kahler, and Tylka (Astrophys. 1. Lett. 700, L199, 2009) who, from examining a subset of ICMEs with flux-rope-like magnetic fields (magnetic clouds) argued that these are "open structures" that allow free access of particles including GCRs to their interior. In fact, we find that magnetic clouds are more likely to participate in the deepest GCR decreases than ICMEs that are not magnetic clouds.

  10. The effects of coronal mass ejection on galactic cosmic rays in the high latitude heliosphere: Observations from Ulysses` first orbit

    SciTech Connect

    Bothmer, V.; Heber, B.; Kunow, H.; Mueller-Mellin, R.; Wibberenz, G.; Gosling, J.T.; Balogh, A.; Raviart, A.; Paizis, C.

    1997-10-01

    During its first solar orbit the Ulysses spacecraft detected several coronal mass ejections (CMEs) at high heliographic latitudes. The authors present first observations on the effects of these high latitude CMEs on galactic cosmic rays (GCRs) using measurements from the Kiel Electron Telescope (KET) which is part of the Cosmic Ray and Solar Particle Investigation (COSPIN) experiment, the Los Alamos SWOOPS (Solar Wind Observations Over the Poles of the Sun) experiment and the magnetic field experiments. They find the passage of these CMEs over the spacecraft to be associated with short term decreases of GCR intensities The relatively weak shocks in these events, driven by the CMEs` over-expansion, had no strong influence on the GCRs. The intensity minimums of GCRs occurred on closed magnetic field lines inside the CMEs themselves as indicated by bidirectional fluxes of suprathermal electrons. Short episodes of intensity increases of GCRs inside CMEs at times when the bidirectional fluxes of suprathermal electrons disappeared, can be interpreted as evidence that GCRs can easily access the interior of those CMEs in which open magnetic field lines are embedded.

  11. DYNAMICAL MASS OF THE M8+M8 BINARY 2MASS J22062280 - 2047058AB {sup ,} {sup ,} {sup ,}

    SciTech Connect

    Dupuy, Trent J.; Bowler, Brendan P.; Liu, Michael C.

    2009-11-20

    We present Keck laser guide star adaptive optics imaging of the M8+M8 binary 2MASS J2206 - 2047AB. Together with archival Hubble Space Telescope, Gemini-North, and Very Large Telescope data, our observations span 8.3 yr of the binary's 35{sup +6}{sub -5} yr orbital period, and we determine a total dynamical mass of 0.15{sup +0.05} {sub -0.03} M{sub sun}, with the uncertainty dominated by the parallax error. Using the measured total mass and individual luminosities, the Tucson and Lyon evolutionary models both give an age for the system of 0.4{sup +9.6}{sub -0.2} Gyr, which is consistent with its thin disk space motion derived from the Besancon Galactic structure model. Our mass measurement combined with the Tucson (Lyon) evolutionary models also yields precise effective temperatures, giving 2660{sup +90}{sub -100} K and 2640{sup +90}{sub -100} K (2550{sup +90}{sub -100} K and 2530{sup +90}{sub -100} K) for components A and B, respectively. These temperatures are in good agreement with estimates for other M8 dwarfs (from the infrared flux method and the M8 mass benchmark LHS 2397aA), but atmospheric model fitting of the integrated-light spectrum gives hotter temperatures of 2800 +- 100 K for both components. This modest discrepancy can be explained by systematic errors in the atmospheric models or by a slight underestimation of the distance (and thus, mass and age) of the system. We also find that the observed near-infrared colors and magnitudes do not agree with those predicted by the Lyon Dusty models, given the known mass of the system.

  12. The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016

    NASA Astrophysics Data System (ADS)

    Johnston, K. G.; Beuther, H.; Linz, H.; Schmiedeke, A.; Ragan, S. E.; Henning, Th.

    2014-08-01

    Context. The massive infrared dark cloud G0.253+0.016 projected ~45 pc from the Galactic centre contains ~105 M⊙ of dense gas whilst being mostly devoid of observed star-formation tracers. Aims: Our goals are therefore to scrutinise the physical properties, dynamics and structure of this cloud with reference to its star-forming potential. Methods: We have carried out a concerted SMA and IRAM 30 m study of this enigmatic cloud in dust continuum, CO isotopologues, several shock tracing molecules, as well as H2CO to trace the gas temperature. In addition, we include ancillary far-IR and sub-mm Herschel and SCUBA data in our analysis. Results: We detect and characterise a total of 36 dust cores within G0.253+0.016 at 1.3 mm and 1.37 mm, with masses between 25 and approximately 250 M⊙, and find that the kinetic temperature of the gas traced by H2CO ratios is >320 K on size-scales of ~0.15 pc. Analysis of the position-velocity diagrams of our observed lines shows broad linewidths and strong shock emission in the south of the cloud, indicating that G0.253+0.016 is colliding with another cloud at vLSR ~ 70 km s-1. We confirm via an analysis of the observed dynamics in the Central Molecular Zone that it is an elongated structure, orientated with Sgr B2 closer to the Sun than Sgr A*, however our results suggest that the actual geometry may be more complex than an elliptical ring. We find that the column density probability distribution function of G0.253+0.016 derived from SMA and SCUBA dust continuum emission is log-normal with no discernible power-law tail, consistent with little star formation, and that its width can be explained in the framework of theory predicting the density structure of clouds created by supersonic, magnetised turbulence. We also present the Δ-variance spectrum of this region, a proxy for the density power spectrum of the cloud, and show it is consistent with that expected for clouds with no current star formation. Finally, we show that even

  13. CHARACTERIZATION OF A SAMPLE OF INTERMEDIATE-TYPE ACTIVE GALACTIC NUCLEI. II. HOST BULGE PROPERTIES AND BLACK HOLE MASS ESTIMATES

    SciTech Connect

    Benitez, Erika; Cruz-Gonzalez, Irene; Martinez, Benoni; Jimenez-Bailon, Elena; Mendez-Abreu, Jairo; Lopez-Martin, Luis; Fuentes-Carrera, Isaura; Chavushyan, Vahram; Leon-Tavares, Jonathan

    2013-02-15

    We present a study of the host bulge properties and their relations with the black hole mass for a sample of 10 intermediate-type active galactic nuclei (AGNs). Our sample consists mainly of early-type spirals, four of them hosting a bar. For 70{sup +10} {sub -17}% of the galaxies, we have been able to determine the type of the bulge, and find that these objects probably harbor a pseudobulge or a combination of classical bulge/pseudobulge, suggesting that pseudobulges might be frequent in intermediate-type AGNs. In our sample, 50% {+-} 14% of the objects show double-peaked emission lines. Therefore, narrow double-peaked emission lines seem to be frequent in galaxies harboring a pseudobulge or a combination of classical bulge/pseudobulge. Depending on the bulge type, we estimated the black hole mass using the corresponding M {sub BH}-{sigma}* relation and found them within a range of 5.69 {+-} 0.21 < log M {sup {sigma}}*{sub BH} < 8.09 {+-} 0.24. Comparing these M {sup {sigma}}*{sub BH} values with masses derived from the FWHM of H{beta} and the continuum luminosity at 5100 A from their SDSS-DR7 spectra (M {sub BH}), we find that 8 out of 10 (80{sup +7} {sub -17}%) galaxies have black hole masses that are compatible within a factor of 3. This result would support that M {sub BH} and M {sup {sigma}}*{sub BH} are the same for intermediate-type AGNs, as has been found for type 1 AGNs. However, when the type of the bulge is taken into account, only three out of the seven (43{sup +18} {sub -15}%) objects of the sample have their M {sup {sigma}}*{sub BH} and M {sub BH} compatible within 3{sigma} errors. We also find that estimations based on the M {sub BH}-{sigma}* relation for pseudobulges are not compatible in 50% {+-} 20% of the objects.

  14. CHARACTERIZING THE BROWN DWARF FORMATION CHANNELS FROM THE INITIAL MASS FUNCTION AND BINARY-STAR DYNAMICS

    SciTech Connect

    Thies, Ingo; Pflamm-Altenburg, Jan; Kroupa, Pavel; Marks, Michael

    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 of 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.

  15. Measuring Mass Flux, Kinetic Luminosities and Abundances in Outflows from Active Galactic Nuclei using the FUSE Archive

    NASA Astrophysics Data System (ADS)

    Kriss, Gerard

    Previous studies of active galactic nuclei (AGN) show that over half of all AGN show outflows from their nuclear regions as evidenced by blue-shifted absorption lines. Measuring the energetics of outflows is a high priority for NASA's science objective of understanding the effect of energetic processes around supermassive black holes on the surrounding environment in galaxies, clusters and the intergalactic medium. Therefore, the most important goals in the study of these outflows are to measure their mass flux, kinetic luminosity, and chemical abundances in order to assess their importance to AGN feedback on their environment. The broad range of redshifts and the access to short rest wavelengths made possible by Far Ultraviolet Spectroscopic Explorer (FUSE) observations of AGN opens a vast discovery space using the many more diagnostic lines (compared to longer wavelengths) in the 500-1050 A range (rest wavelengths) that show up as absorption troughs in AGN outflows. This is especially true for the density- sensitive excited-state transitions of highly ionized elements (e.g., OIV* 790) that can yield the distance of the outflows from the central source, and the increasingly higher ionization species (O VI, Ne VIII, Na IX and Mg X) that supply the crucial connection between the UV and X-ray (so-called warm absorbers) manifestation of AGN outflows. Over the course of its 10 years of operation, FUSE observed nearly two hundred active galactic nuclei (AGN) at redshifts from less than 0.01 to nearly 3. While a select few of the brightest individual objects have been studied in detail, the surveys of the overall data set done to date examined only the lowest redshift objects (z<0.15), and only using data from the first 6 years or so of the mission. Our preliminary examination of the FUSE archive reveals dozens of AGN with appropriate characteristics for us to carry out our proposed program of study. Many of the best objects also have HST spectra available, and we will

  16. Simultaneous radio and X-ray observations of Galactic Centre low-mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Berendsen, Stephan G. H.; Fender, Robert; Kuulkers, Erik; Heise, J.; van der Klis, M.

    2000-10-01

    We have performed simultaneous X-ray and radio observations of 13 Galactic Centre low-mass X-ray binaries in 1998 April using the Wide Field Cameras on board BeppoSAX and the Australia Telescope Compact Array, the latter simultaneously at 4.8 and 8.64GHz. We detect two Z sources, GX 17+2 and GX 5-1, and the unusual `hybrid' source GX 13+1. Upper limits, which are significantly deeper than previous non-detections, are placed on the radio emission from two more Z sources and seven atoll sources. Hardness-intensity diagrams constructed from the Wide Field Camera data reveal GX 17+2 and GX 5-1 to have been on the lower part of the horizontal branch and/or the upper part of the normal branch at the time of the observations, and the two non-detected Z sources, GX 340+0 and GX 349+2, to have been on the lower part of the normal branch. This is consistent with the previous empirically determined relation between radio and X-ray emission from Z sources, in which radio emission is strongest on the horizontal branch and weakest on the flaring branch. For the first time we have information on the X-ray state of atoll sources, which are clearly radio-quiet relative to the Z sources, during periods of observed radio upper limits. We place limits on the linear polarization from the three detected sources, and use accurate radio astrometry of GX 17+2 to confirm that it is probably not associated with the optical star NP Ser. Additionally we place strong upper limits on the radio emission from the X-ray binary 2S 0921-630, disagreeing with suggestions that it is a Z-source viewed edge-on.

  17. Galactic model parameters of cataclysmic variables: Results from a new absolute magnitude calibration with 2MASS and WISE

    NASA Astrophysics Data System (ADS)

    Özdönmez, A.; Ak, T.; Bilir, S.

    2015-01-01

    In order to determine the spatial distribution, Galactic model parameters and luminosity function of cataclysmic variables (CVs), a J-band magnitude limited sample of 263 CVs has been established using a newly constructed period-luminosity-colours (PLCs) relation which includes J,Ks and W1-band magnitudes in 2MASS and WISE photometries, and the orbital periods of the systems. This CV sample is assumed to be homogeneous regarding to distances as the new PLCs relation is calibrated with new or re-measured trigonometric parallaxes. Our analysis shows that the scaleheight of CVs is increasing towards shorter periods, although selection effects for the periods shorter than 2.25 h dramatically decrease the scaleheight: the scaleheight of the systems increases from 192 pc to 326 pc as the orbital period decreases from 12 to 2.25 h. The z-distribution of all CVs in the sample is well fitted by an exponential function with a scaleheight of 213-10+11 pc. However, we suggest that the scaleheight of CVs in the Solar vicinity should be ∼300 pc and that the scaleheights derived using the sech2 function should be also considered in the population synthesis models. The space density of CVs in the Solar vicinity is found 5.58(1.35)×10-6 pc-3 which is in the range of previously derived space densities and not in agreement with the predictions of the population models. The analysis based on the comparisons of the luminosity function of white dwarfs with the luminosity function of CVs in this study show that the best fits are obtained by dividing the luminosity functions of white dwarfs by a factor of 350-450.

  18. On the virialization of disk winds: Implications for the black hole mass estimates in active galactic nuclei

    SciTech Connect

    Kashi, Amit; Proga, Daniel; Nagamine, Kentaro; Greene, Jenny; Barth, Aaron J.

    2013-11-20

    Estimating the mass of a supermassive black hole in an active galactic nucleus usually relies on the assumption that the broad line region (BLR) is virialized. However, this assumption seems to be invalid in BLR models that consist of an accretion disk and its wind. The disk is likely Keplerian and therefore virialized. However, beyond a certain point, the wind material must be dominated by an outward force that is stronger than gravity. Here, we analyze hydrodynamic simulations of four different disk winds: an isothermal wind, a thermal wind from an X-ray-heated disk, and two line-driven winds, one with and the other without X-ray heating and cooling. For each model, we determine whether gravity governs the flow properties by computing and analyzing the volume-integrated quantities that appear in the virial theorem: internal, kinetic, and gravitational energies. We find that in the first two models, the winds are non-virialized, whereas the two line-driven disk winds are virialized up to a relatively large distance. The line-driven winds are virialized because they accelerate slowly so that the rotational velocity is dominant and the wind base is very dense. For the two virialized winds, the so-called projected virial factor scales with inclination angle as 1/sin {sup 2} i. Finally, we demonstrate that an outflow from a Keplerian disk becomes unvirialized more slowly when it conserves the gas specific angular momentum, as in the models considered here, than when it conserves the angular velocity, as in the so-called magneto-centrifugal winds.

  19. Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc

    NASA Astrophysics Data System (ADS)

    Mitschang, A. W.; De Silva, G.; Zucker, D. B.; Anguiano, B.; Bensby, T.; Feltzing, S.

    2014-03-01

    The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as Galactic Archaeology with HERMES (GALAH) and the Gaia European Southern Observatory survey (Gaia-ESO), will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work, we perform the first ever blind chemical tagging experiment, i.e. tagging stars with no known or otherwise discernible associations, on a sample of 714 disc field stars with a number of high-quality high-resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thought. Our results point to several important conclusions, among them that group finding will be limited strictly to chemical abundance space, e.g. stellar ages, kinematics, colours, temperature and surface gravity do not enhance the detectability of groups. We also demonstrate that in addition to its role in probing the chemical enrichment and kinematic history of the Galactic disc, chemical tagging represents a powerful new stellar age determination technique.

  20. Dynamical fermion mass generation and exciton spectra in graphene

    SciTech Connect

    Zhang Chunxu; Liu Guozhu; Huang Mingqiu

    2011-03-15

    The Coulomb interaction between massless Dirac fermions may induce dynamical chiral symmetry breaking by forming excitonic pairs in clean graphene, leading to semimetal-insulator transition. If the Dirac fermions have zero bare mass, an exact continuous chiral symmetry is dynamically broken and thus there are massless Goldstone excitons. If the Dirac fermions have a small bare mass, an approximate continuous chiral symmetry is dynamically broken and the resultant Goldstone-type excitons become massive, which is analogous to what happens in QCD. In this paper, after solving the Dyson-Schwinger gap equation in the presence of a small bare fermion mass, we found a remarkable reduction of the critical Coulomb interaction strength for excitonic pair formation and a strong enhancement of dynamical fermion mass. We then calculate the masses of Goldstone-type excitons using the Shifman-Vainshtein-Zakharov sum-rule method and operator product expansion technique developed in QCD and find that the exciton masses are much larger than bare fermion mass but smaller than the width of dynamical fermion mass gap. We also study the spin susceptibilities and estimate the masses of non-Goldstone-type excitons using the same tools.

  1. Besançon Galactic model analysis of MOA-II microlensing: evidence for a mass deficit in the inner bulge

    NASA Astrophysics Data System (ADS)

    Awiphan, S.; Kerins, E.; Robin, A. C.

    2016-02-01

    Galactic bulge microlensing surveys provide a probe of Galactic structure. We present the first field-by-field comparison between microlensing observations and the Besançon population synthesis Galactic model. Using an updated version of the model we provide maps of optical depth, average event duration and event rate for resolved source populations and for difference imaging analysis (DIA) events. We also compare the predicted event time-scale distribution to that observed. The simulation follows the selection criteria of the MOA-II survey. We modify the Besançon model to include M dwarfs and brown dwarfs. Our best-fitting model requires a brown dwarf mass function slope of -0.4. The model provides good agreement with the observed average duration, and respectable consistency with the shape of the time-scale distribution (reduced χ2 ≃ 2.2). The DIA and resolved source limiting yields bracket the observed number of events by MOA-II (2.17 × and 0.83 × the number observed, respectively). We perform a two-dimensional fit to the event spatial distribution to predict the optical depth and event rate across the Galactic bulge. The most serious difficulty for the model is that it provides only ˜50 per cent of the measured optical depth and event rate per star at low Galactic latitude around the inner bulge (|b| < 3°). This discrepancy most likely is associated with known underestimated extinction and star counts in the innermost regions and therefore provides additional support for a missing inner stellar population.

  2. On the Role of the Curvature Drift Instability in the Dynamics of Electrons in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Osmanov, Zaza

    2013-11-01

    We study the influence of the centrifugally driven curvature drift instability (CDI) on the dynamics of relativistic electrons in the magnetospheres of active galactic nuclei (AGN). We generalize in our previous paper by considering relativistic particles with different initial phases. Considering the Euler continuity and induction equations, by taking into account the resonant conditions, we derive the growth rate of the CDI. We show that due to the centrifugal effects, the rotational energy is efficiently pumped directly into the drift modes, that leads to the generation of a toroidal component of the magnetic field. As a result, the magnetic field lines transform into such a configuration when particles do not experience any forces and since the instability is centrifugally driven, at this stage the CDI is suspended.

  3. Symbiotic starburst-black hole active galactic nuclei - I. Isothermal hydrodynamics of the mass-loaded interstellar medium

    NASA Astrophysics Data System (ADS)

    Williams, R. J. R.; Baker, A. C.; Perry, Judith J.

    1999-12-01

    Compelling evidence associates the nuclei of active galaxies and massive starbursts. The symbiosis between a compact nuclear starburst stellar cluster and a massive black hole can self-consistently explain the properties of active nuclei. The young stellar cluster has a profound effect on the most important observable properties of active galaxies through its gravity, and by mass injection through stellar winds, supernovae and stellar collisions. This mass loss, injected throughout the nucleus, creates a hot nuclear interstellar medium (nISM). The cluster both acts as an optically thin fuel reservoir and enriches the nISM with the products of nucleosynthesis. The nISM flows under gravitational and radiative forces until it leaves the nucleus or is accreted on to the black hole or accretion disc. The radiative force exerted by the black hole-accretion disc radiation field is not spherically symmetric. This results in complex flows in which regions of inflow can coexist with high Mach number outflowing winds and hydrodynamic jets. We present two-dimensional hydrodynamic models of such nISM flows, which are highly complex and time-variable. Shocked shells, jets and explosive bubbles are produced, with bipolar winds driving out from the nucleus. Our results graphically illustrate why broad-emission-line studies have consistently failed to identify any simple, global flow geometry. The real structure of the flows is inevitably yet more complex. The structure of these nISM flows is principally determined by two dimensionless quantities. The first is the magnitude of the stellar cluster velocity dispersion relative to the sound speed in the nISM. These speeds measure the gravitational and thermal energies in the nISM respectively, and, therefore, whether the gas is initially bound or escapes in a thermal wind. The second parameter is the Mach number of the ill-collimated nISM flow which is driven away from the central black hole. We discuss a two-parameter classification

  4. THREE-DIMENSIONAL STELLAR KINEMATICS AT THE GALACTIC CENTER: MEASURING THE NUCLEAR STAR CLUSTER SPATIAL DENSITY PROFILE, BLACK HOLE MASS, AND DISTANCE

    SciTech Connect

    Do, T.; Martinez, G. D.; Bullock, J.; Kaplinghat, M.; Peter, A. H. G.; Yelda, S.; Ghez, A.; Phifer, K.; Lu, J. R.

    2013-12-10

    We present three-dimensional (3D) kinematic observations of stars within the central 0.5 pc of the Milky Way (MW) nuclear star cluster (NSC) using adaptive optics imaging and spectroscopy from the Keck telescopes. Recent observations have shown that the cluster has a shallower surface density profile than expected for a dynamically relaxed cusp, leading to important implications for its formation and evolution. However, the true 3D profile of the cluster is unknown due to the difficulty in de-projecting the stellar number counts. Here, we use spherical Jeans modeling of individual proper motions and radial velocities to constrain, for the first time, the de-projected spatial density profile, cluster velocity anisotropy, black hole mass (M {sub BH}), and distance to the Galactic center (R {sub 0}) simultaneously. We find that the inner stellar density profile of the late-type stars, ρ(r)∝r {sup –γ}, have a power law slope γ=0.05{sub −0.60}{sup +0.29}, much more shallow than the frequently assumed Bahcall-Wolf slope of γ = 7/4. The measured slope will significantly affect dynamical predictions involving the cluster, such as the dynamical friction time scale. The cluster core must be larger than 0.5 pc, which disfavors some scenarios for its origin. Our measurement of M{sub BH}=5.76{sub −1.26}{sup +1.76}×10{sup 6} M {sub ☉} and R{sub 0}=8.92{sub −0.55}{sup +0.58} kpc is consistent with that derived from stellar orbits within 1'' of Sgr A*. When combined with the orbit of S0-2, the uncertainty on R {sub 0} is reduced by 30% (8.46{sub −0.38}{sup +0.42} kpc). We suggest that the MW NSC can be used in the future in combination with stellar orbits to significantly improve constraints on R {sub 0}.

  5. COMPARING X-RAY AND DYNAMICAL MASS PROFILES IN THE EARLY-TYPE GALAXY NGC 4636

    SciTech Connect

    Johnson, Ria; Raychaudhury, Somak; Chakrabarty, Dalia; O'Sullivan, Ewan E-mail: D.Chakrabarty@warwick.ac.u

    2009-12-01

    We present the results of an X-ray mass analysis of the early-type galaxy NGC 4636, using Chandra data. We have compared the X-ray mass density profile with that derived from a dynamical analysis of the system's globular clusters (GCs). Given the observed interaction between the central active galactic nucleus and the X-ray emitting gas in NGC 4636, we would expect to see a discrepancy in the masses recovered by the two methods. Such a discrepancy exists within the central approx10 kpc, which we interpret as the result of non-thermal pressure support or a local inflow. However, over the radial range approx10-30 kpc, the mass profiles agree within the 1sigma errors, indicating that even in this highly disturbed system, agreement can be sought at an acceptable level of significance over intermediate radii, with both methods also indicating the need for a dark matter halo. However, at radii larger than 30 kpc, the X-ray mass exceeds the dynamical mass, by a factor of 4-5 at the largest disagreement. A Fully Bayesian Significance Test finds no statistical reason to reject our assumption of velocity isotropy, and an analysis of X-ray mass profiles in different directions from the galaxy center suggests that local disturbances at large radius are not the cause of the discrepancy. We instead attribute the discrepancy to the paucity of GC kinematics at large radius, coupled with not knowing the overall state of the gas at the radius where we are reaching the group regime (>30 kpc), or a combination of the two.

  6. Dynamical mass generation in QED with weak magnetic fields

    SciTech Connect

    Ayala, A.; Rojas, E.; Bashir, A.; Raya, A.

    2006-09-25

    We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2.

  7. Dynamics Behind the Quark Mass Hierarchy and Electroweak Symmetry breaking

    NASA Astrophysics Data System (ADS)

    Miransky, Vladimir A.

    2011-05-01

    I review the dynamics in a new class of models describing the quark mass hierarchy, suggested recently by Michio Hashimoto and the author. In this class, the dynamics primarily responsible for electroweak symmetry breaking (EWSB) leads to the mass spectrum of quarks with no (or weak) isospin violation. Moreover, the values of these masses are of the order of the observed masses of the down-type quarks. Then, strong (although subcritical) horizontal diagonal interactions for the t quark plus horizontal flavor-changing neutral interactions between different families lead (with no fine tuning) to a realistic quark mass spectrum. In this scenario, many composite Higgs bosons occur. A concrete model with the dynamical EWSB with the fourth family is described in detail.

  8. Dynamics Behind the Quark Mass Hierarchy and Electroweak Symmetry breaking

    SciTech Connect

    Miransky, Vladimir A.

    2011-05-24

    I review the dynamics in a new class of models describing the quark mass hierarchy, suggested recently by Michio Hashimoto and the author. In this class, the dynamics primarily responsible for electroweak symmetry breaking (EWSB) leads to the mass spectrum of quarks with no (or weak) isospin violation. Moreover, the values of these masses are of the order of the observed masses of the down-type quarks. Then, strong (although subcritical) horizontal diagonal interactions for the t quark plus horizontal flavor-changing neutral interactions between different families lead (with no fine tuning) to a realistic quark mass spectrum. In this scenario, many composite Higgs bosons occur. A concrete model with the dynamical EWSB with the fourth family is described in detail.

  9. The search for low-luminosity high-mass X-ray binaries and the study of X-ray populations in the Galactic disk

    NASA Astrophysics Data System (ADS)

    Fornasini, Francesca; Tomsick, John; Bodaghee, Arash; Rahoui, Farid; Krivonos, Roman; Corral-Santana, Jesus; An, Hongjun; Bauer, Franz E.; Gotthelf, Eric V.; Stern, Daniel; NuSTAR Galactic Plane Survey Team

    2016-01-01

    High-mass X-ray binaries (HMXBs), which consist of a neutron star (NS) or black hole (BH) accreting material from a massive stellar companion, provide valuable insights into the evolution of massive stars and the merger rates of NS/NS, NS/BH, and BH/BH binaries whose gravitational wave signatures will soon be detectable by facilities such as Advanced-LIGO. INTEGRAL discoveries of new classes of lower-luminosity HMXBs, some highly obscured and some showing extreme transient activity, as well as the recent discovery of the very quiescent and only known Be-BH binary, have considerably changed our understanding of clumping in massive stellar winds and the relative importance of different binary evolutionary channels. In order to better characterize the low-luminosity HMXB population, we have performed a survey of a square degree region in the direction of the Norma spiral arm with Chandra and NuSTAR. These surveys, combined with optical and infrared spectroscopic follow-up of the counterparts of hard X-ray sources, have yielded three HMXB candidates to date. Future radial-velocity follow-up of these candidates, as well as other Be HMXB candidates from the NuSTAR serendipitous survey, will help determine whether these sources truly are HMXBs and, if so, constrain the mass of the compact object in these systems. If confirmed, these HMXB candidates could extend our measurement of the HMXB luminosity function by about two orders of magnitude and provide important constraints on massive binary evolutionary models. In addition, the colliding wind binaries and pulsar wind nebulae discovered in the Norma X-ray survey will help shed light on other aspects of massive stellar evolution and massive stellar remnants. Finally, these surveys provide the opportunity to compare the hard X-ray populations in the Galactic disk and the Galactic Center. While the dominant hard X-ray populations in both of these Galactic regions appear to be cataclysmic variables (CVs), those in the Norma

  10. Mass properties measurement system: Dynamics and statics measurements

    NASA Technical Reports Server (NTRS)

    Doty, Keith L.

    1993-01-01

    This report presents and interprets experimental data obtained from the Mass Properties Measurement System (MPMS). Statics measurements yield the center-of-gravity of an unknown mass and dynamics measurements yield its inertia matrix. Observations of the MPMS performance has lead us to specific design criteria and an understanding of MPMS limitations.

  11. Limits on the spatial variations of the electron-to-proton mass ratio in the Galactic plane

    NASA Astrophysics Data System (ADS)

    Levshakov, S. A.; Reimers, D.; Henkel, C.; Winkel, B.; Mignano, A.; Centurión, M.; Molaro, P.

    2013-11-01

    Aims: We aim to validate the Einstein equivalence principle (local position invariance) by limiting the fractional changes in the electron-to-proton mass ratio, μ = me/mp, measured in Galactic plane objects. Methods: High-resolution spectral observations of dark clouds in the inversion line of NH3(1, 1) and pure rotational lines of other molecules (the so-called ammonia method) were performed at the Medicina 32-m and the Effelsberg 100-m radio telescopes to measure the radial velocity offsets, ΔRV = Vrot - Vinv, between the rotational and inversion transitions, which have different sensitivities to the value of μ. Results: In our previous observations (2008-2010), a mean offset of ⟨ΔRV⟩ = 0.027 ± 0.010 km s-1 (3σ confidence level (C.L.)) was measured. To test for possible hidden errors, we carried out additional observations of a sample of molecular cores in 2010-2013. As a result, a systematic error with an amplitude ~0.02 km s-1 in the radial velocities was revealed. The averaged offset between the radial velocities of the rotational transitions of HC3N(2-1), HC5N(9-8), HC7N(16-15), HC7N(21-20), and HC7N(23-22), and the inversion transition of NH3(1, 1) is ⟨ΔRV⟩ = 0.003 ± 0.018 km s-1 (3σ C.L.). This value, when interpreted in terms of Δμ/μ = (μobs - μlab)/μlab, constraints the μ-variation at the level of Δμ/μ < 2 × 10-8 (3σ C.L.), which is the most stringent limit on the fractional changes in μ based on astronomical observations. Based on observations obtained with the Effelsberg 100-m telescope operated by the Max-Planck Institut für Radioastronomie on behalf of the Max-Planck-Gesellschaft (Germany), and with the Medicina 32-m telescope operated by INAF (Italy).

  12. The long and the short of it: modelling double neutron star and collapsar Galactic dynamics

    NASA Astrophysics Data System (ADS)

    Kiel, Paul D.; Hurley, Jarrod R.; Bailes, Matthew

    2010-07-01

    Understanding the nature of galactic populations of double compact binaries (where both stars are a neutron star or black hole) has been a topic of interest for many years, particularly the coalescence rate of these binaries. The only observed systems thus far are double neutron star systems containing one or more radio pulsars. However, theorists have postulated that short-duration gamma-ray bursts may be evidence of coalescing double neutron star or neutron star-black hole binaries, while long-duration gamma-ray bursts are possibly formed by tidally enhanced rapidly rotating massive stars that collapse to form black holes (collapsars). The work presented here examines populations of double compact binary systems and tidally enhanced collapsars. We make use of BINPOP and BINKIN, two components of a recently developed population synthesis package. Results focus on correlations of both binary and spatial evolutionary population characteristics. Pulsar and long-duration gamma-ray burst observations are used in concert with our models to draw the conclusions that (i) double neutron star binaries can merge rapidly on time-scales of a few million years (much less than that found for the observed double neutron star population), (ii) common-envelope evolution within these models is a very important phase in double neutron star formation and (iii) observations of long gamma-ray burst projected distances are more centrally concentrated than our simulated coalescing double neutron star and collapsar Galactic populations. Better agreement is found with dwarf galaxy models although the outcome is strongly linked to the assumed birth radial distribution. The birth rate of the double neutron star population in our models ranges from 4 to 160 Myr-1 and the merger rate ranges from 3 to 150 Myr-1. The upper and lower limits of the rates result from including electron-capture supernova kicks to neutron stars and decreasing the common-envelope efficiency, respectively. Our double

  13. Galactic cannibalism. IV. The evidence-correlations between dynamical time scales and Bautz-Morgan type

    SciTech Connect

    McGlynn, T.A.; Ostriker, J.P.

    1980-11-01

    If the luminosity of supergiant cD galaxies in particular, and the Bautz-Morgan sequence of galaxy types in general, is produced by dynamical evolutionary processes, then one expects to find a correlation between dynamical times and ..delta..M/sub 12/, the magnitude difference between first and second brightest cluster members.

  14. Common origin of the 3.55 keV x-ray line and the Galactic Center gamma-ray excess in a radiative neutrino mass model

    NASA Astrophysics Data System (ADS)

    Borah, Debasish; Dasgupta, Arnab; Adhikari, Rathin

    2015-10-01

    We attempt to simultaneously explain the recently observed 3.55 keV x-ray line in the analysis of XMM-Newton telescope data and the Galactic Center gamma ray excess observed by the Fermi Gamma Ray Space Telescope within an Abelian gauge extension of the standard model. We consider a two component dark matter scenario with tree level mass difference 3.55 keV such that the heavier one can decay into the lighter one and a photon with energy 3.55 keV. The lighter dark matter candidate is protected from decaying into the standard model particles by a remnant Z2 symmetry into which the Abelian gauge symmetry gets spontaneously broken. If the mass of the dark matter particle is chosen to be within 31-40 GeV, then this model can also explain the Galactic Center gamma ray excess if the dark matter annihilation into b b ¯ pairs has a cross section of ⟨σ v ⟩≃(1.4 -2.0 )×1 0-26 cm3/s . We constrain the model from the requirement of producing correct dark matter relic density, 3.55 keV x-ray line flux, and Galactic Center gamma ray excess. We also impose the bounds coming from dark matter direct detection experiments as well as collider limits on additional gauge boson mass and gauge coupling. We also briefly discuss how this model can give rise to subelectron volt neutrino masses at tree level as well as the one-loop level while keeping the dark matter mass at a few tens of giga-electron volts. We also constrain the model parameters from the requirement of keeping the one-loop mass difference between two dark matter particles below a kilo-electron volt. We find that the constraints from light neutrino mass and kilo-electron volt mass splitting between two dark matter components show more preference for opposite C P eigenvalues of the two fermion singlet dark matter candidates in the model.

  15. Quasar-microlensing versus star-microlensing evidence of small-planetary-mass objects as the dominant inner-halo galactic dark matter

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.; Schild, Rudolph E.

    2011-11-01

    We examine recent results of two kinds of microlensing experiments intended to detect galactic dark matter objects, and we suggest that the lack of short period star-microlensing events observed for stars near the Galaxy does not preclude either the "rogue planets" identified from quasar-microlensing by Schild 1996 as the missing-mass of a lens galaxy, or the "Primordial Fog Particles" (PFPs) in Proto-Globular-star-Cluster (PGC) clumps predicted by Gibson 1996 - 2000 as the dominant inner-halo galactic dark matter component from a new hydrodynamic gravitational structure formation theory. We point out that hydro-gravitational processes acting on a massive population of such micro-brown-dwarfs in their nonlinear accretional cascades to form stars gives intermittent lognormal number density np distributions for the PFPs within the PGC gas-stabilized-clumps. Hence, star-microlensing searches that focus on a small fraction of the sky assuming a uniform distribution for np are subject to vast underestimates of the mean ⟨np⟩mean. Sparse independent samples give modes 10-4 - 10-6 smaller than means of the highly skewed lognormal distributions expected. Quasar-microlensing searches with higher optical depths are less affected by np intermittency. We attempt to reconcile the results of the star-microlensing and quasar-microlensing studies, with particular reference to the necessarily hydrogenous and primordial small-planetary-mass range. We conclude that star microlensing searches cannot exclude and are unlikely even to detect these low-mass candidate-galactic-dark-matter-objects so easily observed by quasar-microlensing and so robustly predicted by the new theory.

  16. X-Ray Outbursts of ESO 243-49 HLX-1: Comparison with Galactic Low-mass X-Ray Binary Transients

    NASA Astrophysics Data System (ADS)

    Yan, Zhen; Zhang, Wenda; Soria, Roberto; Altamirano, Diego; Yu, Wenfei

    2015-09-01

    We studied the outburst properties of the hyper-luminous X-ray source ESO 243-49 HLX-1, using the full set of Swift monitoring observations. We quantified the increase in the waiting time, recurrence time, and e-folding rise timescale along the outburst sequence, and the corresponding decrease in outburst duration, total radiated energy, and e-folding decay timescale, which confirms previous findings. HLX-1 spends less and less time in outburst and more and more time in quiescence, but its peak luminosity remains approximately constant. We compared the HLX-1 outburst properties with those of bright Galactic low-mass X-ray binary transients (LMXBTs). Our spectral analysis strengthens the similarity between state transitions in HLX-1 and those in Galactic LMXBTs. We also found that HLX-1 follows the nearly linear correlations between the hard-to-soft state transition luminosity and the peak luminosity, and between the rate of change of X-ray luminosity during the rise phase and the peak luminosity, which indicates that the occurrence of the hard-to-soft state transition of HLX-1 is similar to those of Galactic LMXBTs during outbursts. We found that HLX-1 does not follow the correlations between total radiated energy and peak luminosity, and between total radiated energy and e-folding rise/decay timescales we had previously identified in Galactic LMXBTs. HLX-1 would follow those correlations if the distance were several hundreds of kiloparsecs. However, invoking a much closer distance for HLX-1 is not a viable solution to this problem, as it introduces other, more serious inconsistencies with the observations.

  17. Secular dynamics in hierarchical three-body systems with mass loss and mass transfer

    SciTech Connect

    Michaely, Erez; Perets, Hagai B.

    2014-10-20

    Recent studies have shown that secular evolution of triple systems can play a major role in the evolution and interaction of their inner binaries. Very few studies explored the stellar evolution of triple systems, and in particular the mass-loss phase of the evolving stellar components. Here we study the dynamical secular evolution of hierarchical triple systems undergoing mass loss. We use the secular evolution equations and include the effects of mass loss and mass transfer, as well as general relativistic effects. We present various evolutionary channels taking place in such evolving triples, and discuss both the effects of mass loss and mass transfer in the inner binary system, as well as the effects of mass loss/transfer from an outer third companion. We discuss several distinct types/regimes of triple secular evolution, where the specific behavior of a triple system can sensitively depend on its hierarchy and the relative importance of classical and general relativistic effects. We show that the orbital changes due to mass-loss and/or mass-transfer processes can effectively transfer a triple system from one dynamical regime to another. In particular, mass loss/transfer can both induce and quench high-amplitude (Lidov-Kozai) variations in the eccentricity and inclination of the inner binaries of evolving triples. They can also change the system dynamics from an orderly periodic behavior to a chaotic one, and vice versa.

  18. Galactic structure from the spacelab infrared telescope. III - A dynamical model for the Milky Way bulge

    NASA Technical Reports Server (NTRS)

    Kent, S. M.

    1992-01-01

    The Milky Way bulge is modeled as an oblate isotropic rotator with constant M/L ratio. A model with M/L sub 2.2 micron = 1 successfully reproduces a variety of stellar velocity dispersion measurements for R between 2 and 1200 pc. An observed increase in the stellar velocity dispersion inside 2 pc requires either that there be an additional central mass of order 3 x 10 exp 6 solar mass or that the stellar motions become anisotropic there. The model has insufficient mass to reproduce the observed peak in the H I and CO rotation curve of 250 km/s at 300 pc; it is argued that the peak arises from noncircular gas motions and does not reflect the true mass of the bulge.

  19. Dynamics of Orbital Masses in an Unbalanced Rotor

    NASA Technical Reports Server (NTRS)

    Gallardo, Vicente; Lawrence, Charles

    2006-01-01

    Historically, orbital masses have been used as automatic balancers in rotating machines. However, in these applications, the masses are free to move and rotate with the rotor from zero to operating speeds. For gas turbine applications it is desirable for the orbital masses to be fixed and unmoving, until their release from a sudden unbalance at the operating speed, such as occurs from a blade-out event. The objective of this work is to develop the dynamical equations of motion for orbital masses on a rotating shaft. In subsequent work these equations will be incorporated into a rotor structural dynamics computer code and the feasibility of attenuating rotor unbalance response with orbital masses will be investigated.

  20. Star formation across cosmic time and its influence on galactic dynamics

    NASA Astrophysics Data System (ADS)

    Freundlich, Jonathan

    2015-12-01

    Observations show that ten billion years ago, galaxies formed their stars at rates up to twenty times higher than now. As stars are formed from cold molecular gas, a high star formation rate means a significant gas supply, and galaxies near the peak epoch of star formation are indeed much more gas-rich than nearby galaxies. Is the decline of the star formation rate mostly driven by the diminishing cold gas reservoir, or are the star formation processes also qualitatively different earlier in the history of the Universe? Ten billion years ago, young galaxies were clumpy and prone to violent gravitational instabilities, which may have contributed to their high star formation rate. Stars indeed form within giant, gravitationally-bound molecular clouds. But the earliest phases of star formation are still poorly understood. Some scenarii suggest the importance of interstellar filamentary structures as a first step towards core and star formation. How would their filamentary geometry affect pre-stellar cores? Feedback mechanisms related to stellar evolution also play an important role in regulating star formation, for example through powerful stellar winds and supernovae explosions which expel some of the gas and can even disturb the dark matter distribution in which each galaxy is assumed to be embedded. This PhD work focuses on three perspectives: (i) star formation near the peak epoch of star formation as seen from observations at sub-galactic scales; (ii) the formation of pre-stellar cores within the filamentary structures of the interstellar medium; and (iii) the effect of feedback processes resulting from star formation and evolution on the dark matter distribution.

  1. Dynamical evidence for causality between galactic cosmic rays and interannual variation in global temperature.

    PubMed

    Tsonis, Anastasios A; Deyle, Ethan R; May, Robert M; Sugihara, George; Swanson, Kyle; Verbeten, Joshua D; Wang, Geli

    2015-03-17

    As early as 1959, it was hypothesized that an indirect link between solar activity and climate could be mediated by mechanisms controlling the flux of galactic cosmic rays (CR) [Ney ER (1959) Nature 183:451-452]. Although the connection between CR and climate remains controversial, a significant body of laboratory evidence has emerged at the European Organization for Nuclear Research [Duplissy J, et al. (2010) Atmos Chem Phys 10:1635-1647; Kirkby J, et al. (2011) Nature 476(7361):429-433] and elsewhere [Svensmark H, Pedersen JOP, Marsh ND, Enghoff MB, Uggerhøj UI (2007) Proc R Soc A 463:385-396; Enghoff MB, Pedersen JOP, Uggerhoj UI, Paling SM, Svensmark H (2011) Geophys Res Lett 38:L09805], demonstrating the theoretical mechanism of this link. In this article, we present an analysis based on convergent cross mapping, which uses observational time series data to directly examine the causal link between CR and year-to-year changes in global temperature. Despite a gross correlation, we find no measurable evidence of a causal effect linking CR to the overall 20th-century warming trend. However, on short interannual timescales, we find a significant, although modest, causal effect between CR and short-term, year-to-year variability in global temperature that is consistent with the presence of nonlinearities internal to the system. Thus, although CR do not contribute measurably to the 20th-century global warming trend, they do appear as a nontraditional forcing in the climate system on short interannual timescales. PMID:25733877

  2. Infrared divergences, mass shell singularities and gauge dependence of the dynamical fermion mass

    NASA Astrophysics Data System (ADS)

    Das, Ashok K.; Frenkel, J.; Schubert, C.

    2013-03-01

    We study the behavior of the dynamical fermion mass when infrared divergences and mass shell singularities are present in a gauge theory. In particular, in the massive Schwinger model in covariant gauges we find that the pole of the fermion propagator is divergent and gauge dependent at one loop, but the leading singularities cancel in the quenched rainbow approximation. On the other hand, in physical gauges, we find that the dynamical fermion mass is finite and gauge independent at least up to one loop.

  3. Large mass hierarchies from strongly-coupled dynamics

    NASA Astrophysics Data System (ADS)

    Athenodorou, Andreas; Bennett, Ed; Bergner, Georg; Elander, Daniel; Lin, C.-J. David; Lucini, Biagio; Piai, Maurizio

    2016-06-01

    Besides the Higgs particle discovered in 2012, with mass 125 GeV, recent LHC data show tentative signals for new resonances in diboson as well as diphoton searches at high center-of-mass energies (2 TeV and 750 GeV, respectively). If these signals are confirmed (or other new resonances are discovered at the TeV scale), the large hierarchies between masses of new bosons require a dynamical explanation. Motivated by these tentative signals of new physics, we investigate the theoretical possibility that large hierarchies in the masses of glueballs could arise dynamically in new strongly-coupled gauge theories extending the standard model of particle physics. We study lattice data on non-Abelian gauge theories in the (near-)conformal regime as well as a simple toy model in the context of gauge/gravity dualities. We focus our attention on the ratio R between the mass of the lightest spin-2 and spin-0 resonances, that for technical reasons is a particularly convenient and clean observable to study. For models in which (non-perturbative) large anomalous dimensions arise dynamically, we show indications that this mass ratio can be large, with R>5. Moreover,our results suggest that R might be related to universal properties of the IR fixed point. Our findings provide an interesting step towards understanding large mass ratios in the non-perturbative regime of quantum field theories with (near) IR conformal behaviour.

  4. Dynamical limits on dark mass in the outer solar system

    SciTech Connect

    Hogg, D.W.; Quinlan, G.D.; Tremaine, S. MIT, Cambridge, MA )

    1991-06-01

    Simplified model solar systems with known observational errors are considered in conducting a dynamical search for dark mass and its minimum detectable amount, and in determining the significance of observed anomalies. The numerical analysis of the dynamical influence of dark mass on the orbits of outer planets and comets is presented in detail. Most conclusions presented are based on observations of the four giant planets where the observational errors in latitude and longitude are independent Gaussian variables with a standard deviation. Neptune's long orbital period cannot be predicted by modern ephemerides, and no evidence of dark mass is found in considering this planet. Studying the improvement in fit when observations are fitted to models that consider dark mass is found to be an efficient way to detect dark mass. Planet X must have a mass of more than about 10 times the minimum detectable mass to locate the hypothetical planet. It is suggested that the IRAS survey would have already located the Planet X if it is so massive and close that it dynamically influences the outer planets. Orbital residuals from comets are found to be more effective than those from planets in detecting the Kuiper belt. 35 refs.

  5. Dynamic simulation of coronal mass ejections

    NASA Technical Reports Server (NTRS)

    Steinolfson, R. S.; Wu, S. T.

    1980-01-01

    A model is developed for the formation and propagation through the lower corona of the loop-like coronal transients in which mass is ejected from near the solar surface to the outer corona. It is assumed that the initial state for the transient is a coronal streamer. The initial state for the streamer is a polytropic, hydrodynamic solution to the steady-state radial equation of motion coupled with a force-free dipole magnetic field. The numerical solution of the complete time-dependent equations then gradually approaches a stationary coronal streamer configuration. The streamer configuration becomes the initial state for the coronal transient. The streamer and transient simulations are performed completely independent of each other. The transient is created by a sudden increase in the pressure at the base of the closed-field region in the streamer configuration. Both coronal streamers and coronal transients are calculated for values of the plasma beta (the ratio of thermal to magnetic pressure) varying from 0.1 to 100.

  6. Method for increasing the dynamic range of mass spectrometers

    DOEpatents

    Belov, Mikhail; Smith, Richard D.; Udseth, Harold R.

    2004-09-07

    A method for enhancing the dynamic range of a mass spectrometer by first passing a sample of ions through the mass spectrometer having a quadrupole ion filter, whereupon the intensities of the mass spectrum of the sample are measured. From the mass spectrum, ions within this sample are then identified for subsequent ejection. As further sampling introduces more ions into the mass spectrometer, the appropriate rf voltages are applied to a quadrupole ion filter, thereby selectively ejecting the undesired ions previously identified. In this manner, the desired ions may be collected for longer periods of time in an ion trap, thus allowing better collection and subsequent analysis of the desired ions. The ion trap used for accumulation may be the same ion trap used for mass analysis, in which case the mass analysis is performed directly, or it may be an intermediate trap. In the case where collection is an intermediate trap, the desired ions are accumulated in the intermediate trap, and then transferred to a separate mass analyzer. The present invention finds particular utility where the mass analysis is performed in an ion trap mass spectrometer or a Fourier transform ion cyclotron resonance mass spectrometer.

  7. RAPID DYNAMICAL MASS SEGREGATION AND PROPERTIES OF FRACTAL STAR CLUSTERS

    SciTech Connect

    Yu Jincheng; Chen Li; De Grijs, Richard

    2011-05-01

    We investigate the evolution of young star clusters using N-body simulations. We confirm that subvirial and fractal-structured clusters will dynamically mass segregate on a short timescale (within 0.5 Myr). We adopt a modified minimum-spanning-tree method to measure the degree of mass segregation, demonstrating that the stars escaping from a cluster's potential are important for the temporal dependence of mass segregation in the cluster. The form of the initial velocity distribution will also affect the degree of mass segregation. If it depends on radius, the outer parts of the cluster would expand without undergoing collapse. In velocity space, we find 'inverse mass segregation', which indicates that massive stars have higher velocity dispersions than their lower-mass counterparts.

  8. All Creatures Great and Small: Probing the Evolution and Structure of Mass from Sub-Galactic to Supercluster Scales using Gravitational Lensing

    NASA Astrophysics Data System (ADS)

    Lagattuta, David James

    Understanding the distribution of mass on cosmic scales provides context for a number of astrophysical topics, including galaxy evolution, structure formation, and cosmology. In this dissertation, I present new research into the distribution of mass throughout the universe, ranging from small (sub-galactic) to large (Supercluster) scales. This work is spread over four separate studies, each focusing on slightly different cosmological distance scales. In the first study, I employ strong and weak gravitational lensing to measure the mass profiles of a sample of massive elliptical galaxies at moderate redshift (z ˜ 0.6). I find that the total mass profile is best described by an isothermal (r -2) distribution, which disagrees with predictions made by numerical simulations. This disagreement provides important clues about the poorly understood interactions between dark matter and baryons. Furthermore, I compare these results to those of a low-redshift (z ˜ 0.2) galaxy sample, and this allows me to constrain the evolution of galaxy-scale mass profiles over a timescale of ˜ 7 billion years. In the second and third studies, I combine strong lensing constraints and high-resolution adaptive optics imaging to develop new mass models for the lens systems B0128+437 and B1938+666. I use these models to search for the presence of small-scale substructures (satellite galaxies) in the vicinity of the host lens. While structure formation models predict a large number of substructure galaxies orbiting a host, this does not agree with observations of the local universe, where only a handful of satellites are seen. I compare the upper-limit substructure constraints from the two strong lenses to the properties of known Milky Way satellites, and lay the foundation for a comprehensive census of extragalactic substructure, using a large sample of lenses to better resolve the tension between theory and observation. Finally, in the fourth study, I focus on mass at super-galactic scales

  9. Proposal on dynamic correction method for resonance ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Noto, Takuma; Tomita, Hideki; Richter, Sven; Schneider, Fabian; Wendt, Klaus; Iguchi, Tetsuo; Kawarabayashi, Jun

    2013-04-01

    For high precision and accuracy in isotopic ratio measurement of transuranic elements using laser ablation assisted resonance ionization mass spectrometry, a dynamic correction method based on correlation of ion signals with energy and timing of each laser pulse was proposed. The feasibility of this dynamic correction method was investigated through the use of a programmable electronics device for fast acquisition of the energy and timing of each laser pulse.

  10. Violent gas dynamics in galactic cosmogony: spiral shocks and rotation of star complexes.

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.

    Star complexes are huge aggregates of stars and gas which are considered as the largest cells of star formation in spiral galaxies (Efremov 1988). Basic observational data on star complexes are presented with a special emphasis on their rotational properties. A possible model of the formation of star complexes and the origin of their spin momentum is discussed based on the physics of nonlinear supersonic gas dynamics effects in the interstellar medium.

  11. Star formation in Galactic flows

    NASA Astrophysics Data System (ADS)

    Smilgys, Romas; Bonnell, Ian A.

    2016-06-01

    We investigate the triggering of star formation in clouds that form in Galactic scale flows as the interstellar medium passes through spiral shocks. We use the Lagrangian nature of smoothed particle hydrodynamics simulations to trace how the star-forming gas is gathered into self-gravitating cores that collapse to form stars. Large-scale flows that arise due to Galactic dynamics create shocks of the order of 30 km s-1 that compress the gas and form dense clouds (n > several × 102 cm-3) in which self-gravity becomes relevant. These large-scale flows are necessary for creating the dense physical conditions for gravitational collapse and star formation. Local gravitational collapse requires densities in excess of n > 103 cm-3 which occur on size scales of ≈1 pc for low-mass star-forming regions (M < 100 M⊙), and up to sizes approaching 10 pc for higher mass regions (M > 103 M⊙). Star formation in the 250 pc region lasts throughout the 5 Myr time-scale of the simulation with a star formation rate of ≈10-1 M⊙ yr-1 kpc-2. In the absence of feedback, the efficiency of the star formation per free-fall time varies from our assumed 100 per cent at our sink accretion radius to values of <10-3 at low densities.

  12. On the Stability of Circular Orbits in Galactic Dynamics: Newtonian Thin Disks

    NASA Astrophysics Data System (ADS)

    Vieira, Ronaldo S. S.; Ramos-Caro, Javier

    2015-01-01

    The study of off-equatorial orbits in razor-thin disks is still in its beginnings. Contrary to what was presented in the literature in recent publications, the vertical stability criterion for equatorial circular orbits cannot be based on the vertical epicyclic frequency, because of the discontinuity in the gravitational field on the equatorial plane. We present a rigorous criterion for the vertical stability of circular orbits in systems composed by a razor-thin disk surrounded by a smooth axially symmetric distribution of matter, the latter representing additional structures such as thick disk, bulge and (dark matter) halo. This criterion is satisfied once the mass surface density of the thin disk is positive. Qualitative and quantitative analyses of nearly equatorial orbits are presented. In particular, the analysis of nearly equatorial orbits allows us to construct an approximate analytical third integral of motion in this region of phase-space, which describes the shape of these orbits in the meridional plane.

  13. Identifying Dynamically Induced Variability in Glacier Mass-Balance Records

    NASA Astrophysics Data System (ADS)

    Christian, J. E.; Siler, N.; Koutnik, M. R.; Roe, G.

    2015-12-01

    Glacier mass-balance (i.e., accumulation vs. ablation) provides a direct indicator of a glacier's relationship with climate. However, mass-balance records contain noise due to internal climate variability (i.e., from stochastic fluctuations in large-scale atmospheric circulation), which can obscure or bias trends in these relatively short timeseries. This presents a challenge in correctly identifying the signature of anthropogenic change. "Dynamical adjustment" is a technique that identifies patterns of variance shared between a climate timeseries of interest (e.g., mass-balance) and independent "predictor" variables associated with large-scale circulation (e.g., Sea Level Pressure, SLP, or Sea Surface Temperature, SST). Extracting the component of variance due to internal variability leaves a residual timeseries for which trends can more confidently be attributed to external forcing. We apply dynamical adjustments based on Partial Least Squares Regression to mass-balance records from South Cascade Glacier in Washington State and Wolverine and Gulkana Glaciers in Alaska, independently analyzing seasonal balance records to assess the dynamical influences on winter accumulation and summer ablation. Seasonally averaged North Pacific SLP and SST fields perform comparably as predictor variables, explaining 50-60% of the variance in winter balance and 30-40% of variance in summer balance for South Cascade and Wolverine Glaciers. Gulkana glacier, located further inland than the other two glaciers, is less closely linked to North Pacific climate variability, with the predictors explaining roughly one-third of variance in its winter and summer balance. We analyze the significance of linear trends in the raw and adjusted mass-balance records, and find that for all three glaciers, a) summer balance shows a statistically significant downward trend that is not substantially altered when dynamically induced variability is removed, and b) winter balance shows no statistically

  14. Depleted galaxy cores and dynamical black hole masses

    SciTech Connect

    Rusli, S. P.; Erwin, P.; Saglia, R. P.; Thomas, J.; Fabricius, M.; Bender, R.; Nowak, N.

    2013-12-01

    Shallow cores in bright, massive galaxies are commonly thought to be the result of scouring of stars by mergers of binary supermassive black holes. Past investigations have suggested correlations between the central black hole mass and the stellar light or mass deficit in the core, using proxy measurements of M {sub BH} or stellar mass-to-light ratios (Y). Drawing on a wealth of dynamical models which provide both M {sub BH} and Y, we identify cores in 23 galaxies, of which 20 have direct, reliable measurements of M {sub BH} and dynamical stellar mass-to-light ratios (Y{sub *,dyn}). These cores are identified and measured using Core-Sérsic model fits to surface brightness profiles which extend out to large radii (typically more than the effective radius of the galaxy); for approximately one-fourth of the galaxies, the best fit includes an outer (Sérsic) envelope component. We find that the core radius is most strongly correlated with the black hole mass and that it correlates better with total galaxy luminosity than it does with velocity dispersion. The strong core-size-M {sub BH} correlation enables estimation of black hole masses (in core galaxies) with an accuracy comparable to the M {sub BH}-σ relation (rms scatter of 0.30 dex in log M {sub BH}), without the need for spectroscopy. The light and mass deficits correlate more strongly with galaxy velocity dispersion than they do with black hole mass. Stellar mass deficits span a range of 0.2-39 M {sub BH}, with almost all (87%) being <10 M {sub BH}; the median value is 2.2 M {sub BH}.

  15. Microlensing by the galactic bar

    NASA Technical Reports Server (NTRS)

    Zhao, Hongsheng; Spergel, David N.; Rich, R. Michael

    1995-01-01

    We compute the optical depth and duration distribution of microlensing events towrd Baade's window in a model composed of a Galactic disk and a bar. The bar model is a self-consistent dynamical model built out of individual orbits that has been populated to be consistent with the COBE maps of the Galaxy and kinematic observations of the Galactic bulge. We find that most of the lenses are in the bulge with a line-of-sight distance 6.25 kpc (adopting R(sub 0) = 8 kpc). The microlensing optical depth of a 2 x 10(exp 10) solar mass bar plus a truncated disk is (2.2 +/- 0.45) x 10(exp -6), consistent with the large optical depth (3.2 +/- 1.2) x 10(exp -6) found by Udalski et al. (1994). This model optical depth is enhanced over the predictions of axisymmetric models by Kiraga & Paczynski (1994) by slightly more than a factor of 2, since the bar is elongated along the line of sight. The large Einstein radius and small transverse velocity dispersion also predict a longer event duration in the self-consistent bar model than in the Kiraga-Paczynski model. The event rate and duration distribution also depend on the lower mass cutoff of the lens mass function. With a 0.1 solar mass cutoff, five to seven events (depending on the contribution of disk lenses) with a logarithmic mean duration of 20 days are expected for the Optical Gravitational Lensing Experiment (OGLE) according to our model, while Udalski et al. (1994) observed nine events with durations from 8 to 62 days. On the other hand, if most of the lenses are brown dwarfs, our model predicts too many short-duration events. A Kolmogorov-Smirnov test finds only 7% probability for the model with 0.01 solar mass cutoff to be consistent with current data.

  16. The Dynamical Evolution of Stellar-Mass Black Holes in Dense Star Clusters

    NASA Astrophysics Data System (ADS)

    Morscher, Maggie

    Solar masses. Birth kicks from supernova explosions may eject some black holes from their birth clusters, but most should be retained initially. Using our Monte Carlo code, we have investigated the long-term dynamical evolution of globular clusters containing large numbers of stellar black holes. Our study is the first to explore in detail the dynamics of BHs in clusters through a large number of realistic simulations covering a wide range of initial conditions (cluster masses from 105 -- 106 Solar masses, as well as variation in other key parameters, such as the virial radius, central concentration, and metallicity), that also includes all the required physics. In almost all of our models we find that significant numbers of black holes (up to about a 1000) are retained all the way to the present. This is in contrast to previous theoretical expectations that most black holes should be ejected dynamically within a few Gyr. The main reason for this difference is that core collapse driven by black holes (through the Spitzer "mass segregation instability'') is easily reverted through three-body processes, and involves only a small number of the most massive black holes, while lower-mass black holes remain well-mixed with ordinary stars far from the central cusp. Thus the rapid segregation of stellar black holes does not lead to a long-term physical separation of most black holes into a dynamically decoupled inner core, as often assumed previously; this is one of the most important results of this dissertation. Combined with the recent detections of several black hole X-ray binary candidates in Galactic globular clusters, our results suggest that stellar black holes could still be present in large numbers in many globular clusters today, and that they may play a significant role in shaping the long-term dynamical evolution and the present-day dynamical structure of many clusters.

  17. Galactic dynamos

    NASA Astrophysics Data System (ADS)

    Moss, David

    There is a broad agreement between the predictions of galactic dynamo theory and observations; although there are still some unresolved difficulties, the theory appears to be robust. Now attention is turning from generic models to studies of particular features of the large-scale magnetic fields, and also to models for specific galaxies. The effects of noncircular flows, for example driven by the interaction of spiral arms and galactic bars with the dynamo, are of current interest.

  18. Chaotic dynamics in charged-particle beams: Possible analogs of galactic evolution

    SciTech Connect

    Bohn, Courtlandt L.; /Northern Illinois U. /Fermilab

    2004-12-01

    During the last couple of years of his life, Henry Kandrup became intensely interested in using charged-particle beams as a tool for exploring the dynamics of evolving galaxies. He and I recognized that both galaxies and charged-particle beams can exhibit collisionless relaxation on surprisingly short time scales, and that this circumstance can be attributed to phase mixing of chaotic orbits. The chaos is often triggered by resonances caused by time dependence in the bulk potential, which acts almost identically for attractive gravitational forces as for repulsive electrostatic forces superposed on external focusing forces. Together we published several papers concerning evolving beams and galaxies, papers that relate to diverse topics such as the physics of chaotic mixing, the applicability of the Vlasov-Poisson formalism, and the production of diffuse halos. We also teamed with people from the University of Maryland to begin designing controlled experiments to be done at the University of Maryland Electron Ring. This paper highlights our collaborative findings as well as plans for future investigations that the findings have motivated.

  19. Photometric Surveys of the Galactic Bulge and Long Bar

    NASA Astrophysics Data System (ADS)

    Gerhard, O.; Wegg, C.; Portail, M.

    The Galactic bar and box/peanut bulge can be studied in an unrivaled manner, star-by-star, with detailed chemical information and full 3D kinematics. Because of intervening dust this is greatly facilitated by the availability of wide field deep NIR photometric surveys. Here we summarize recent results on the three-dimensional structure of the bulge and the long bar region, based on 2MASS, UKIDSS, and particularly the ongoing VVV survey. We also summarize results from dynamical models for the Galactic bulge constructed with the Made-to-Measure method.

  20. The lives and deaths of star clusters near the Galactic Center

    NASA Astrophysics Data System (ADS)

    McMillan, S. L. W.; Portegies Zwart, S. F.

    2001-12-01

    We study the dynamical evolution of young star clusters formed within 10 pc of the Galactic Center. Dynamical friction between a cluster and its surroundings tends to drive it toward the Galactic Center, ultimately leading to the cluster's disruption by tidal forces. During the inspiral, dynamical evolution drives the star cluster toward core collapse; the most massive stars segregate to the cluster center while lower mass stars segregate to the cluster halo. At the same time the cluster halo is stripped by the Galactic tidal field. Lower mass stars therefore tend to be lost from the cluster at larger distances from the Galactic center, while higher mass stars can reach farther in. We find a clear relation between galactocentric distance and the mean mass of stars left behind by the cluster. If the cluster goes into deep core collapse before it reaches the Galactic Center a collision runaway may occur, possibly resulting in the formation of a single object of several hundred solar masses. We acknowledge support from NASA under grants NAG5-9264 and NAG5-10775. SPZ is a Hubble Fellow.

  1. The AKARI 2.5-5.0 μm Spectral Atlas of Type-1 Active Galactic Nuclei: Black Hole Mass Estimator, Line Ratio, and Hot Dust Temperature

    NASA Astrophysics Data System (ADS)

    Kim, Dohyeong; Im, Myungshin; Kim, Ji Hoon; Jun, Hyunsung David; Woo, Jong-Hak; Lee, Hyung Mok; Lee, Myung Gyoon; Nakagawa, Takao; Matsuhara, Hideo; Wada, Takehiko; Oyabu, Shinki; Takagi, Toshinobu; Ohyama, Youichi; Lee, Seong-Kook

    2015-01-01

    We present 2.5-5.0 μm spectra of 83 nearby (0.002 < z < 0.48) and bright (K < 14 mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0 μm spectral region contains emission lines such as Brβ (2.63 μm), Brα (4.05 μm), and polycyclic aromatic hydrocarbons (3.3 μm), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selected from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ~1100 K and ~220 K, respectively, rather than the commonly cited hot dust temperature of 1500 K.

  2. MEASURING THE MASS OF 4UO900-40 DYNAMICALLY

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Etzel, Paul B.; Boyd, Patricia T.

    2006-01-01

    Accurate measurements of neutron star masses are needed to constrain the equation of state of neutron star matter - of importance to both particle physics and the astrophysics of neutron stars - and to identify the evolutionary track of the progenitor stars that form neutron stars. The best measured values of the mass of 4UO900-40 (= Vela XR-l), 1.86 +/- 0.16 Msun (Barziv et al. 2001) and 1.93 +/- 0.20 Msun (Abubekerov et al. 2004), make it a leading candidate for the most massive neutron star known. The direct relationship between the maximum mass of neutron stars and the equation of state of ultra-dense matter makes 4UO900-40 an important neutron star mass to determine accurately. The confidence interval on previous mass estimates, obtained from observations that include parameters determined by non-dynamical methods, are not small enough to significantly restrict possible equations of state. We describe here a purely dynamical method for determining the mass of 4UO900-40, an X-ray pulsar, using the reprocessed UV pulses emitted by its BO.5Ib companion. One can derive the instantaneous radial velocity of each component by simultaneous X-ray and UV observations at the two quadratures of the system. The Doppler shift caused by the primary's rotational velocity and the illumination pattern of the X-rays on the primary, two of the three principal contributors to the uncertainty on the derived mass of the neutron star, almost exactly cancel by symmetry in this method. A heuristic measurement of the mass of 4UO900-40 using observations obtained previously with the High Speed Photometer on HST is given in Appendix A.

  3. Emergent Newtonian dynamics and the geometric origin of mass

    SciTech Connect

    D’Alessio, Luca; Polkovnikov, Anatoli

    2014-06-15

    We consider a set of macroscopic (classical) degrees of freedom coupled to an arbitrary many-particle Hamiltonian system, quantum or classical. These degrees of freedom can represent positions of objects in space, their angles, shape distortions, magnetization, currents and so on. Expanding their dynamics near the adiabatic limit we find the emergent Newton’s second law (force is equal to the mass times acceleration) with an extra dissipative term. In systems with broken time reversal symmetry there is an additional Coriolis type force proportional to the Berry curvature. We give the microscopic definition of the mass tensor. The mass tensor is related to the non-equal time correlation functions in equilibrium and describes the dressing of the slow degree of freedom by virtual excitations in the system. In the classical (high-temperature) limit the mass tensor is given by the product of the inverse temperature and the Fubini–Study metric tensor determining the natural distance between the eigenstates of the Hamiltonian. For free particles this result reduces to the conventional definition of mass. This finding shows that any mass, at least in the classical limit, emerges from the distortions of the Hilbert space highlighting deep connections between any motion (not necessarily in space) and geometry. We illustrate our findings with four simple examples. -- Highlights: •Derive the macroscopic Newton’s equation from the microscopic many-particle Schrödinger’s equation. •Deep connection between geometry and dynamics. •Geometrical interpretation of the mass of macroscopic object as deformation of Hilbert space. •Microscopic expression for mass and friction tensors.

  4. Mass composition and dynamics in quiet sun prominences

    NASA Astrophysics Data System (ADS)

    Kilper, Gary K.

    2009-06-01

    Solar prominences are transient phenomena in the solar atmosphere that display highly dynamic activity and can result in dramatic eruptions, ejecting a large amount of material into the heliosphere. The dynamics of the prominence plasma reveal information about its interaction with the magnetic field of the prominence, while the eruptions are associated with coronal mass ejections, which greatly affect space weather near Earth and throughout the solar system. My research on these topics was conducted via observational analyses of the partially-ionized prominence material, its composition, and the dynamics over time in prominences that range in activity from quiescent to highly active. The main results are evidence that (1) in quiescent prominences, neutral He is located more in the lower part of the structure, (2) a higher level of activity in prominences is related to a mixing of the material, and (3) an extended period of high activity and mixing occurs prior to eruptions, possibly due to mass loading. In addition, innovative modifications to analytical techniques led to measurements of the material's mass, composition, and small-scale dynamics.

  5. Dynamical Mass Measurements of Contaminated Galaxy Clusters Using Machine Learning

    NASA Astrophysics Data System (ADS)

    Ntampaka, Michelle; Trac, Hy; Sutherland, Dougal; Fromenteau, Sebastien; Poczos, Barnabas; Schneider, Jeff

    2016-01-01

    Galaxy clusters are a rich source of information for examining fundamental astrophysical processes and cosmological parameters, however, employing clusters as cosmological probes requires accurate mass measurements derived from cluster observables. We study dynamical mass measurements of galaxy clusters contaminated by interlopers, and show that a modern machine learning (ML) algorithm can predict masses by better than a factor of two compared to a standard scaling relation approach. We create a mock catalog from Multidark's publicly-available N-body MDPL1 simulation where a simple cylindrical cut around the cluster center allows interlopers to contaminate the clusters. In the standard approach, we use a power law scaling relation to infer cluster mass from galaxy line of sight (LOS) velocity dispersion. The presence of interlopers in the catalog produces a wide, flat fractional mass error distribution, with width = 2.13. We employ the Support Distribution Machine (SDM) class of algorithms to learn from distributions of data to predict single values. Applied to distributions of galaxy observables such as LOS velocity and projected distance from the cluster center, SDM yields better than a factor-of-two improvement (width = 0.67). Remarkably, SDM applied to contaminated clusters is better able to recover masses than even a scaling relation approach applied to uncontaminated clusters. We show that the SDM method more accurately reproduces the cluster mass function, making it a valuable tool for employing cluster observations to evaluate cosmological models.

  6. A retarding ion mass spectrometer for the Dynamics Explorer-1

    NASA Technical Reports Server (NTRS)

    Wright, W.

    1985-01-01

    The Retarding Ion Mass Spectrometer (RIMS) for Dynamics Explorer-1 is an instrument designed to measure the details of the thermal plasma distribution. It combines the ion temperature determining capability of the retarding potential analyzer with the compositional capabilities of the mass spectrometer and adds multiple sensor heads to sample all directions relative to the spacecraft ram direction. This manual provides a functional description of the RIMS, the instrument calibration, and a description of the commands which can be stored in the instrument logic to control its operation.

  7. Derivation of mass and stiffness matrices from dynamic test data.

    NASA Technical Reports Server (NTRS)

    Thoren, A. R.

    1972-01-01

    A technique is described by which orthonormal modal vectors, computed from dynamic test response data, are used to derive mass, stiffness, and damping matrices for a discrete model of the distributed elastic system. Matrices thus computed from subsystems tests may be readily incorporated into larger system models. The method has been applied to a test of the Saturn V S-II stage LOX tank-engine support system. The dynamic responses of the discrete model are shown to correlate well with test data throughout the frequency range tested.

  8. The Circum-Galactic Medium of MASsive Spirals (CGM-MASS) I: Introduction to the XMM-Newton Large Project and a Case Study of NGC 5908

    NASA Astrophysics Data System (ADS)

    Li, Jiang-Tao; Bregman, Joel N.; Wang, Daniel; Crain, Robert A.; Anderson, Michael E.

    2016-04-01

    The Circum-Galactic Medium of MASsive Spirals (CGM-MASS) is a project studying the overall content, physical and chemical properties, and spatial distributions of the multi-phase circum-galactic medium (CGM) around a small sample of the most massive (M*>2×1011M⊙, vrot>300km/s) isolated spiral galaxies in the local Universe. In this talk, we will briefly introduce the sample and the science goals and present the first detailed case study of the XMM-Newton observation of the hot gas halo of NGC5908. After careful data calibration, point source removal, and background analysis, we find the diffuse soft X-ray emission of NGC 5908 is significantly more extended than the stellar light in the vertical direction. The 0.5-1.25keV radial intensity profile tracing hot gas emission can be detected above the background out to ~2’, or ~30kpc from the nucleus. The radial intensity distribution of hot gas can be characterized with a β-model with a core radius of rcore~8.8kpc and the β-index of β~0.8. The spectra extracted from the inner halo indicates an extremely low metallicity of Z<0.1Z⊙ and a temperature of kT~0.5keV. The cooling radius is rcool~27kpc or ~0.065r200, within which the hot gas could cool radiatively within the cosmic time. Using the best-fit models of the spectra and the radial intensity profile, we further estimate some physical parameters of the hot gas and extrapolate them to larger radii. Adding the mass of cold atomic and molecular gases, hot gas, and stars, the total baryon fraction fb within r200 is ~0.07, significantly below the cosmic baryon fraction of ~0.17. Therefore, ~60% of the baryons in the halo of NGC5908 is still “missing”. The hot gas accounts for ~56% of the total baryon content in the whole halo, but only ~2% within the cooling radius. By comparing NGC5908 to other galaxies or groups/clusters of galaxies, we find that it could be slightly X-ray brighter at a given stellar mass, when compared to lower-mass galaxies. NGC5908 also

  9. Exoplanetary System Dynamics: Planetary Multiplicity and Mass Effects

    NASA Astrophysics Data System (ADS)

    Isoe, Mari; Kokubo, Eiichiro; Turner, Edwin

    2015-12-01

    Recently numerous systems consisting of multiple exoplanets have been discovered. Using a dataset of 375 systems (500 planets) discovered by the radial velocity method and 365 systems (899 planets) containing planet candidates found by the Kepler Mission, we investigate the dependence of the dynamical structure of planetary systems on their multiplicity and the masses of the member planets. We classify the planetary system by three parameters: planetary multiplicity, planetary mass, and the evolutionary stage of the central star. We normalize planetary masses by the mass of the central star and divide the planets into small and large categories by a cut at $10^{-4}$. The central star is classified into main-sequence or giant according to its evolutionary stage. We focus on the angular momentum deficit (AMD) of the systems and the orbital separation between adjacent planets normalized by their Hill radii. We find that in all categories the system AMD decreases with increasing multiplicity. This suggests that in order for multiple systems to be stable, each planet's orbit must be relatively circular. In addition, we find that the distribution of orbital eccentricities of the massive planets and low-mass planets differs. In particular, only high-mass planets have eccentricities larger than 0.4. In the low-mass systems around main sequence stars, we find that the orbital separation decreases with increasing multiplicity. In addition, the orbital separation around main-sequence stars is wider than that around giants. Furthermore, the minimum orbital separation is about 6.4 for non-resonant pairs. This paper presents the statistical properties of the dynamical structure of multiple planetary systems and discusses their formation.

  10. Schwinger-Dyson Equations and Dynamical gluon mass generation

    SciTech Connect

    Aguilar, A.C.; Natale, A.A.

    2004-12-02

    We obtain a solution for the gluon propagador in Landau gauge within two distinct approximations for the Schwinger-Dyson equations (SDE). The first, named Mandelstam's approximation, consist in neglecting all contributions that come from fermions and ghosts fields while in the second, the ghosts fields are taken into account leading to a coupled system of integral equations. In both cases we show that a dynamical mass for the gluon propagator can arise as a solution.

  11. Numerical study of dynamical mass generation in QED3

    NASA Astrophysics Data System (ADS)

    Bashir, A.; Huet, A.; Raya, A.

    2006-05-01

    We carry out a numerical study of dynamical generation of fermion masses by solving the Schwinger-Dyson equation for the fermion propagator in three-dimensional quenched Quantum Electrodynamics (QED3) in various gauges. We employ an ansatz for the three-point vertex which satisfies the Ward-Green-Takahashi identity, namely, the Ball-Chiu Vertex. We discuss the advantages of our numerical method over some earlier ones.

  12. Dynamical and Stellar Masses of Lyman-alpha Galaxies

    NASA Astrophysics Data System (ADS)

    Rhoads, James E.; Malhotra, S.; McLinden, E.; Richardson, M. L.; Finkelstein, S. L.; Tilvi, V. S.

    2012-01-01

    We have observed strong nebular lines of [OIII] and H alpha for Lyman-alpha galaxies at z=2-3.1 using Keck+NIRSPEC, LBT+LUCIFER, and Gemini+NIFS. [OIII] 5007 is strong enough to dominate the 2 micron K band fluxes of these galaxies, and leads to an overestimate of the stellar mass of the galaxy by an order of magnitude. After correcting for the observed [OIII] lines, we infer low masses and young ages for these galaxies. We also use the physical widths of the rest-optical lines, combined with spatial sizes from HST imaging, to obtain direct dynamical mass estimates of Lyman alpha galaxies (which cannot be done using the resonantly scattered Lyman alpha line). Finally, we combine our stellar mass estimates and line widths to place these galaxies on the baryonic Tully-Fisher relation. We find that the stellar masses required to reproduce the observed light are lower than one would expect based on the galaxies' line widths. The stellar mass densities of these galaxies are comparable to those of elliptical galaxies today. We gratefully acknowledge support from NSF grant NSF-AST-0808165.

  13. Emergent Newtonian dynamics and the geometric origin of mass

    NASA Astrophysics Data System (ADS)

    D'Alessio, Luca; Polkovnikov, Anatoli

    2014-06-01

    We consider a set of macroscopic (classical) degrees of freedom coupled to an arbitrary many-particle Hamiltonian system, quantum or classical. These degrees of freedom can represent positions of objects in space, their angles, shape distortions, magnetization, currents and so on. Expanding their dynamics near the adiabatic limit we find the emergent Newton's second law (force is equal to the mass times acceleration) with an extra dissipative term. In systems with broken time reversal symmetry there is an additional Coriolis type force proportional to the Berry curvature. We give the microscopic definition of the mass tensor. The mass tensor is related to the non-equal time correlation functions in equilibrium and describes the dressing of the slow degree of freedom by virtual excitations in the system. In the classical (high-temperature) limit the mass tensor is given by the product of the inverse temperature and the Fubini-Study metric tensor determining the natural distance between the eigenstates of the Hamiltonian. For free particles this result reduces to the conventional definition of mass. This finding shows that any mass, at least in the classical limit, emerges from the distortions of the Hilbert space highlighting deep connections between any motion (not necessarily in space) and geometry. We illustrate our findings with four simple examples.

  14. Exploring dynamical gluon mass generation in three dimensions

    NASA Astrophysics Data System (ADS)

    Cornwall, John M.

    2016-01-01

    We reexamine the d =3 dynamical gluon mass problem in pure-glue non-Abelian S U (N ) gauge theories, paying particular attention to the observed (in Landau gauge) violation of positivity for the spectral function of the gluon propagator. This is expressed as a large bulge in the propagator at small momentum, due to the d =3 avatar of asymptotic freedom. Mass is defined through m-2=Δ (p =0 ) , where Δ (p ) is the scalar function for the gluon propagator in some chosen gauge; it is not a pole mass and is generally gauge dependent, except in the gauge-invariant pinch technique (PT). We truncate the PT equations with a recently proposed method called the vertex paradigm that automatically satisfies the QED-like Ward identity relating the three-gluon PT vertex function with the PT propagator. The mass is determined by a homogeneous Bethe-Salpeter equation involving this vertex and propagator. This gap equation also encapsulates the Bethe-Salpeter equation for the massless scalar excitations, essentially Nambu-Goldstone fields, that necessarily accompany gauge-invariant gluon mass. The problem is to find a good approximate value for m and at the same time explain the bulge, which by itself leads, in the gap equation for the gluon mass, to excessively large values for the mass. Our point is not to give a high-accuracy determination of m but to clarify the way in which the propagator bulge and a fairly accurate estimate of m can coexist, and we use various approximations that illustrate the underlying mechanisms. The most critical point is to satisfy the Ward identity. In the PT we estimate a gauge-invariant dynamical gluon mass of m ≈N g2/(2.48 π ) . We translate these results to the Landau gauge using a background-quantum identity involving a dynamical quantity κ such that m =κ mL , where mL-2≡ΔL(p =0 ) . Given our estimates for m , κ , the relation is fortuitously well satisfied for S U (2 ) lattice data.

  15. MASSIVE CLUSTERS IN THE INNER REGIONS OF NGC 1365: CLUSTER FORMATION AND GAS DYNAMICS IN GALACTIC BARS

    SciTech Connect

    Elmegreen, Bruce G.; Galliano, Emmanuel; Alloin, Danielle E-mail: egallian@on.b

    2009-10-01

    Cluster formation and gas dynamics in the central regions of barred galaxies are not well understood. This paper reviews the environment of three 10{sup 7} M {sub sun} clusters near the inner Lindblad resonance (ILR) of the barred spiral NGC 1365. The morphology, mass, and flow of H I and CO gas in the spiral and barred regions are examined for evidence of the location and mechanism of cluster formation. The accretion rate is compared with the star formation rate to infer the lifetime of the starburst. The gas appears to move from inside corotation in the spiral region to looping filaments in the interbar region at a rate of approx6 M {sub sun} yr{sup -1} before impacting the bar dustlane somewhere along its length. The gas in this dustlane moves inward, growing in flux as a result of the accretion to approx40 M {sub sun} yr{sup -1} near the ILR. This inner rate exceeds the current nuclear star formation rate by a factor of 4, suggesting continued buildup of nuclear mass for another approx0.5 Gyr. The bar may be only 1-2 Gyr old. Extrapolating the bar flow back in time, we infer that the clusters formed in the bar dustlane outside the central dust ring at a position where an interbar filament currently impacts the lane. The ram pressure from this impact is comparable to the pressure in the bar dustlane, and both are comparable to the pressure in the massive clusters. Impact triggering is suggested. The isothermal assumption in numerical simulations seems inappropriate for the rarefaction parts of spiral and bar gas flows. The clusters have enough lower-mass counterparts to suggest they are part of a normal power-law mass distribution. Gas trapping in the most massive clusters could explain their [Ne II] emission, which is not evident from the lower-mass clusters nearby.

  16. Quantum-gravity induced Lorentz violation and dynamical mass generation

    SciTech Connect

    Mavromatos, Nick E.

    2011-01-15

    In the eprint by Jean Alexandre [arXiv:1009.5834], a minimal extension of (3+1)-dimensional quantum electrodynamics has been proposed, which includes Lorentz violation (LV) in the form of higher-(spatial)-derivative isotropic terms in the gauge sector, suppressed by a mass scale M. The model can lead to dynamical mass generation for charged fermions. In this article, I elaborate further on this idea and I attempt to connect it to specific quantum-gravity models, inspired from string/brane theory. Specifically, in the first part of the article, I comment briefly on the gauge dependence of the dynamical mass generation in the approximations of J. Alexandre [arXiv:1009.5834.], and I propose a possible avenue for obtaining the true gauge-parameter-independent value of the mass by means of pinch technique argumentations. In the second part of the work, I embed the LV QED model into multibrane world scenarios with a view to provide a geometrical way of enhancing the dynamical mass to phenomenologically realistic values by means of bulk warp metric factors, in an (inverse) Randall-Sundrum hierarchy. Finally, in the third part of this paper, I demonstrate that such Lorentz-violating QED models may represent parts of a low-energy effective action (of Finsler-Born-Infeld type) of open strings propagating in quantum D0-particle stochastic space-time foam backgrounds, which are viewed as consistent quantum-gravity configurations. To capture correctly the quantum-fluctuating nature of the foam background, I replace the D0-recoil-velocity parts of this action by appropriate gradient operators in three-space, keeping the photon field part intact. This is consistent with the summation over world-sheet genera in the first-quantized string approach. I identify a class of quantum orderings which leads to the LV QED action of J. Alexandre, arXiv:1009.5834. In this way I argue, following the logic in that work, that the D-foam can lead to dynamically generated masses for charged

  17. THE GALACTIC SPIN OF AGN GALAXIES

    SciTech Connect

    Cervantes-Sodi, Bernardo; Hernandez, X.; Park, Changbom; Choi, Yun-Young E-mail: xavier@astroscu.unam.mx

    2011-07-01

    Using an extensive sample of galaxies selected from the Sloan Digital Sky Survey Data Release 5, we compare the angular momentum distribution of active galactic nuclei (AGNs) with non-AGN hosting late-type galaxies. To this end we characterize galactic spin through the dimensionless angular momentum parameter {lambda}, which we estimate through simple dynamical considerations. Using a volume-limited sample, we find a considerable difference when comparing the empirical distributions of {lambda} for AGNs and non-AGN galaxies, the AGNs showing typically low {lambda} values and associated dispersions, while non-AGNs present higher {lambda} values and a broader distribution. A more striking difference is found when looking at {lambda} distributions in thin M{sub r} cuts; while the spin of non-AGN galaxies presents an anticorrelation with M{sub r} , with bright (massive) galaxies having low spins, AGN host galaxies present uniform values of {lambda} at all magnitudes, a behavior probably imposed by the fact that most late-type AGN galaxies present a narrow range in color, with a typical constant {lambda} value. We also find that the fraction of AGN hosting galaxies in our sample strongly depends on galactic spin, increasing dramatically for decreasing {lambda}. For AGN host galaxies, we compute the mass of their supermassive black holes and find that this value tends to be higher for low spin galaxies, even at fixed luminosity, a result that could account, to a certain extent, for the spread on the luminosity-black-hole mass relation.

  18. Galaxy dynamics and the mass density of the universe.

    PubMed Central

    Rubin, V C

    1993-01-01

    Dynamical evidence accumulated over the past 20 years has convinced astronomers that luminous matter in a spiral galaxy constitutes no more than 10% of the mass of a galaxy. An additional 90% is inferred by its gravitational effect on luminous material. Here I review recent observations concerning the distribution of luminous and nonluminous matter in the Milky Way, in galaxies, and in galaxy clusters. Observations of neutral hydrogen disks, some extending in radius several times the optical disk, confirm that a massive dark halo is a major component of virtually every spiral. A recent surprise has been the discovery that stellar and gas motions in ellipticals are enormously complex. To date, only for a few spheroidal galaxies do the velocities extend far enough to probe the outer mass distribution. But the diverse kinematics of inner cores, peripheral to deducing the overall mass distribution, offer additional evidence that ellipticals have acquired gas-rich systems after initial formation. Dynamical results are consistent with a low-density universe, in which the required dark matter could be baryonic. On smallest scales of galaxies [10 kiloparsec (kpc); Ho = 50 km.sec-1.megaparsec-1] the luminous matter constitutes only 1% of the closure density. On scales greater than binary galaxies (i.e., >/=100 kpc) all systems indicate a density approximately 10% of the closure density, a density consistent with the low baryon density in the universe. If large-scale motions in the universe require a higher mass density, these motions would constitute the first dynamical evidence for nonbaryonic matter in a universe of higher density. Images Fig. 3 Fig. 5 PMID:11607393

  19. The masses of young stars: CN as a probe of dynamical masses

    NASA Astrophysics Data System (ADS)

    Guilloteau, S.; Simon, M.; Piétu, V.; Di Folco, E.; Dutrey, A.; Prato, L.; Chapillon, E.

    2014-07-01

    Aims: We attempt to determine the masses of single or multiple young T Tauri and HAeBe stars from the rotation of their Keplerian disks. Methods: We used the IRAM PdBI interferometer to perform arcsecond resolution images of the CN N = 2-1 transition with good spectral resolution. Integrated spectra from the 30 m radiotelescope show that CN is relatively unaffected by contamination from the molecular clouds. Our sample includes 12 sources, among which isolated stars like DM Tau and MWC 480 are used to demonstrate the method and its accuracy. We derive the dynamical mass by fitting a disk model to the emission, a process giving M/D, the mass-to-distance ratio. We also compare the CN results with higher resolution CO data, that are however affected by contamination. Results: All disks are found in nearly perfect Keplerian rotation. We determine accurate masses for 11 stars, in the mass range 0.5 to 1.9 M⊙. The remaining one, DG Tau B, is a deeply embedded object for which CN emission partially arises from the outflow. With previous determinations, this leads to 14 (single) stars with dynamical masses. Comparison with evolutionary tracks, in a distance independent modified HR diagram, show good overall agreement (with one exception, CW Tau), and indicate that measurement of effective temperatures are the limiting factor. The lack of low mass stars in the sample does not allow to distinguish between alternate tracks. Based on observations carried out with the IRAM Plateau de Bure interferometer. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Appendices are available in electronic form at http://www.aanda.org

  20. Emergent Newtonian dynamics and the geometric origin of mass

    NASA Astrophysics Data System (ADS)

    D'Alessio, Luca; Polkovnikov, Anatoli

    2014-03-01

    We consider an arbitrary many-body system with possibly infinitely many degrees of freedom interacting with few macroscopic parameters which are allowed to slowly change in time. These degrees of freedom can represent positions of objects in space, their angles, shape distortions, magnetization, currents and so on. By extending the Kubo linear response theory to such setups we derive the dynamics of the macroscopic d.o.f. which takes the form of the emergent Newton's second law (force is equal to the mass times acceleration) with an extra dissipative term. We find the microscopic expression for the mass tensor relating it to the non-equal time correlation functions in equilibrium. In the classical (high-temperature) limit the mass tensor is given by the product of the inverse temperature and the Fubini-Study metric tensor determining the natural distance between the eigenstates of the Hamiltonian. For free particles this result reduces to the conventional definition of mass. This finding shows that any mass, at least in the classical limit, emerges from the distortions of the Hilbert space highlighting deep connections between any motion and geometry. This work was partially supported by BSF 2010318, NSF DMR- 0907039, AFOSR FA9550-10- 1-0110

  1. ALMA Observations of the Galactic Center: SiO Outflows and High Mass Star Formation Near Sgr A

    NASA Technical Reports Server (NTRS)

    Yusef-Zadeh, F.; Royster, M.; Wardle, M.; Arendt, R.; Bushouse, H.; Gillessen, S.; Lis, D.; Pound, M. W.; Roberts, D. A.; Whitney, B.; Wooten, A.

    2013-01-01

    Using ALMA observations of the Galactic center with a spatial resolution of 2.61" x 0.97 ", we detected 11 SiO (5-4) clumps of molecular gas in the within 0.6pc (15") of Sgr A*, interior of the 2-pc circumnuclear molecular ring. Three SiO (5-4) clumps closest to Sgr A* show the largest central velocities of approximately 150 kilometers per second and broadest asymmetric linewidths with total linewidths FWZI approximately 110-147 kilometers per second. Other clumps are distributed mainly to the NE of the ionized minispiral with narrow linewidths of FWHM approximately 11-27 kilometers per second. Using CARMA data, LVG modeling of the broad velocity clumps, the SiO (5-4) and (2-1) line ratios constrain the column density N(SiO) approximately 10(exp 14) per square centimeter, and the H2 gas density n(sub H2) = (3-9) x 10(exp 5) per cubic centimeter for an assumed kinetic temperature 100-200K. The SiO (5-4) clumps with broad and narrow linewidths are interpreted as highly embedded protostellar outflows, signifying an early stage of massive star formation near Sgr A* in the last 104 years. Additional support for the presence of YSO outflows is that the luminosities and velocity widths lie in the range detected from protostellar outflows in star forming regions in the Galaxy. Furthermore, SED modeling of stellar sources along the N arm show two YSO candidates near SiO clumps supporting in-situ star formation near Sgr A*. We discuss the nature of star formation where the gravitational potential of the black hole dominates. In particular, we suggest that external radiative pressure exerted on self-shielded molecular clouds enhance the gas density, before the gas cloud become gravitationally unstable near Sgr A*.

  2. A Simple Model of Stability in Critical Mass Dynamics

    NASA Astrophysics Data System (ADS)

    Centola, Damon

    2013-04-01

    Collective behaviors often spread via the self-reinforcing dynamics of critical mass. In collective behaviors with strongly self-reinforcing dynamics, incentives to participate increase with the number of participants, such that incentives are highest when the full population has adopted the behavior. By contrast, when collective behaviors have weakly self-reinforcing dynamics, incentives to participate "peak out" early, leaving a residual fraction of non-participants. In systems of collective action, this residual fraction constitutes free riders, who enjoy the collective good without contributing anything themselves. This "free rider problem" has given rise to a research tradition in collective action that shows how free riding can be eliminated by increasing the incentives for participation, and thereby making cooperation strongly self-reinforcing. However, we show that when the incentives to participate have weakly self-reinforcing dynamics, which allow free riders, collective behaviors will have significantly greater long term stability than when the incentives have strongly self-reinforcing dynamics leading to full participation.

  3. The nuclear X-ray source in NGC 3628: A strange active galactic nucleus or the most luminous high-mass X-ray binary known?

    NASA Technical Reports Server (NTRS)

    Dahlem, Michael; Heckman, Timothy M.; Fabbiano, Giuseppina

    1995-01-01

    After 12 years, during which its unabsorbed soft X-ray flux in the 0.1-2.0 keV band was almost constant at about f(sub x) approximately 10(exp -12) ergs/s/sq cm, the compact nuclear source in NGC 3628 was not detected in one of our ROSAT observations, with a limiting sensitivity of f(sub x) approximately 5 x 10(exp -14) ergs/s/sq cm. Our data can be explained in two ways. The source is either the most massive X-ray binary known so far, with a greater than and approximately equal to 75 solar mass black hole, or an unusual low-luminosity Active Galactic Nuclei (AGN). The X-ray spectrum is typical of a high-mass X-ray binary, while the luminosity of the source of L(sub x) is approximately equal to 10(exp 40) ergs/s is more similar to those of low-luminosity AGNs. If it is an AGN, variable obscuration might explain the observed light curve.

  4. THE AKARI 2.5-5.0 μm SPECTRAL ATLAS OF TYPE-1 ACTIVE GALACTIC NUCLEI: BLACK HOLE MASS ESTIMATOR, LINE RATIO, AND HOT DUST TEMPERATURE

    SciTech Connect

    Kim, Dohyeong; Im, Myungshin; Kim, Ji Hoon; Jun, Hyunsung David; Lee, Seong-Kook; Woo, Jong-Hak; Lee, Hyung Mok; Lee, Myung Gyoon; Nakagawa, Takao; Matsuhara, Hideo; Wada, Takehiko; Takagi, Toshinobu; Oyabu, Shinki; Ohyama, Youichi E-mail: mim@astro.snu.ac.kr

    2015-01-01

    We present 2.5-5.0 μm spectra of 83 nearby (0.002 < z < 0.48) and bright (K < 14 mag) type-1 active galactic nuclei (AGNs) taken with the Infrared Camera on board AKARI. The 2.5-5.0 μm spectral region contains emission lines such as Brβ (2.63 μm), Brα (4.05 μm), and polycyclic aromatic hydrocarbons (3.3 μm), which can be used for studying the black hole (BH) masses and star formation activity in the host galaxies of AGNs. The spectral region also suffers less dust extinction than in the ultra violet (UV) or optical wavelengths, which may provide an unobscured view of dusty AGNs. Our sample is selected from bright quasar surveys of Palomar-Green and SNUQSO, and AGNs with reverberation-mapped BH masses from Peterson et al. Using 11 AGNs with reliable detection of Brackett lines, we derive the Brackett-line-based BH mass estimators. We also find that the observed Brackett line ratios can be explained with the commonly adopted physical conditions of the broad line region. Moreover, we fit the hot and warm dust components of the dust torus by adding photometric data of SDSS, 2MASS, WISE, and ISO to the AKARI spectra, finding hot and warm dust temperatures of ∼1100 K and ∼220 K, respectively, rather than the commonly cited hot dust temperature of 1500 K.

  5. THE OPTICAL COMPANION TO THE INTERMEDIATE-MASS MILLISECOND PULSAR J1439-5501 IN THE GALACTIC FIELD

    SciTech Connect

    Pallanca, C.; Lanzoni, B.; Dalessandro, E.; Ferraro, F. R.; Salaris, M.

    2013-08-20

    We present the identification of the companion star to the intermediate-mass binary pulsar (PSR) J1439-5501 obtained by means of ground-based deep images in the B, V, and I bands, acquired with FORS2 mounted at the European Southern Observatory (ESO)-Very Large Telescope (VLT). The companion is a massive white dwarf (WD) with B = 23.57 {+-} 0.02, V = 23.21 {+-} 0.01, and I = 22.96 {+-} 0.01, located at only {approx}0.''05 from the pulsar radio position. Comparing the WD location in the (B, B-V) and (V, V-I) color-magnitude diagrams with theoretical cooling sequences, we derived a range of plausible combinations of companion masses (1 M{sub Sun} {approx}< M{sub COM} {approx}< 1.3 M{sub Sun }), distances (d {approx}< 1200 pc), radii ({approx}< 7.810{sup -3} R{sub Sun }), and temperatures (T=31350{sup +21500}{sub -7400}). From the PSR mass function and the estimated mass range we also constrained the inclination angle i {approx}> 55 Degree-Sign and the pulsar mass (M{sub PSR} {approx}< 2.2 M{sub Sun }). The comparison between the WD cooling age and the spin-down age suggests that the latter is overestimated by a factor of about 10.

  6. Fermion flavor mixing in models with dynamical mass generation

    SciTech Connect

    Benes, Petr

    2010-03-15

    We present a model-independent method of dealing with fermion flavor mixing in the case when instead of constant, momentum-independent mass matrices one has rather momentum-dependent self-energies. This situation is typical for strongly coupled models of dynamical fermion mass generation. We demonstrate our approach on the example of quark mixing. We show that quark self-energies with a generic momentum dependence lead to an effective Cabibbo-Kobayashi-Maskawa matrix, which turns out to be in general nonunitary, in accordance with previous claims of other authors, and to nontrivial flavor changing electromagnetic and neutral currents. We also discuss some conceptual consequences of the momentum-dependent self-energies and show that in such a case the interaction basis and the mass basis are not related by a unitary transformation. In fact, we argue that the latter is merely an effective concept, in a specified sense. While focusing mainly on the fermionic self-energies, we also study the effects of momentum-dependent radiative corrections to the gauge bosons and to the proper vertices. Our approach is based on an application of the Lehmann-Symanzik-Zimmermann reduction formula and for the special case of constant self-energies it gives the same results as the standard approach based on the diagonalization of mass matrices.

  7. Estimation of the mass center and dynamics of a spherical test mass for gravitational reference sensors

    NASA Astrophysics Data System (ADS)

    Conklin, John W.

    variations in the sensor readout scale factor to ˜ 10-4, which is critical to the accurate reduction of the Gravity Probe B science data and the achievement of overall mission goals. The model is then extended to the application of an advanced gravitational reference sensor for gravitational wave observation, fundamental physics and inertial navigation. Analytical modeling and numerical simulation show that a data processing technique can produce picometer level mass center measurements and one part per million spin frequency determination on-board the spacecraft in real-time. However, dynamic range limitations of the optical displacement sensor require that the mass center offset from the geometric center be less than 100 mu, which is challenging due to test mass density inhomogeneities on the order of 10-5. In the final portion of this dissertation, a laboratory demonstration of a novel technique for measuring the mass center of a sphere to 150 nm, approaching the 100 nm requirement and nearly one order of magnitude better than previous methods, is presented. The new technique again takes advantage of the symmetry of the sphere to spectrally shift the mass center information above low frequency by rolling the sphere down a set of parallel rails.

  8. 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.

  9. Earth Structure, Ice Mass Changes, and the Local Dynamic Geoid

    NASA Astrophysics Data System (ADS)

    Harig, C.; Simons, F. J.

    2014-12-01

    Spherical Slepian localization functions are a useful method for studying regional mass changes observed by satellite gravimetry. By projecting data onto a sparse basis set, the local field can be estimated more easily than with the full spherical harmonic basis. We have used this method previously to estimate the ice mass change in Greenland from GRACE data, and it can also be applied to other planetary problems such as global magnetic fields. Earth's static geoid, in contrast to the time-variable field, is in large part related to the internal density and rheological structure of the Earth. Past studies have used dynamic geoid kernels to relate this density structure and the internal deformation it induces to the surface geopotential at large scales. These now classical studies of the eighties and nineties were able to estimate the mantle's radial rheological profile, placing constraints on the ratio between upper and lower mantle viscosity. By combining these two methods, spherical Slepian localization and dynamic geoid kernels, we have created local dynamic geoid kernels which are sensitive only to density variations within an area of interest. With these kernels we can estimate the approximate local radial rheological structure that best explains the locally observed geoid on a regional basis. First-order differences of the regional mantle viscosity structure are accessible to this technique. In this contribution we present our latest, as yet unpublished results on the geographical and temporal pattern of ice mass changes in Antarctica over the past decade, and we introduce a new approach to extract regional information about the internal structure of the Earth from the static global gravity field. Both sets of results are linked in terms of the relevant physics, but also in being developed from the marriage of Slepian functions and geoid kernels. We make predictions on the utility of our approach to derive fully three-dimensional rheological Earth models, to

  10. The role of stellar mass-loss in dynamics of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Jungwiert, B.; Combes, F.; Palous, J.

    A new N-body sticky-particles computer code for spiral galaxies is presented. The substantial improvement over existing models, either sticky-particles or SPH, is the scheme for the bi-directional mass exchange between gas and stars: the consumption of the former by star formation is taken into account by locking a fraction of gas in newly created stars while the mass-loss from stars via stellar winds and supernova explosions is implemented as time dependent over the Hubble time. A comparison with models not including gas recycling or treating it as immediate shows important differences as to star formation rate, gas consumption time, and the rate at which gas is fuelled towards galactic centers, all having potentially deep consequences for galactic evolution.