A lower limit to the accretion disc radius in the low-luminosity AGN NGC 1052 derived from high-angular resolution data

NASA Astrophysics Data System (ADS)

Reb, Lennart; Fernández-Ontiveros, Juan A.; Prieto, M. Almudena; Dolag, Klaus

2018-05-01

We investigate the central sub-arcsec region of the low-luminosity active galactic nucleus NGC 1052, using a high-angular resolution dataset that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost ˜17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a truncated disc providing the necessary accretion power must be truncated at rtr ≳ 26 rg, consistent with the inner radius derived from the observations of the Fe Kα line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.

AN APPARENT REDSHIFT DEPENDENCE OF QUASAR CONTINUUM: IMPLICATION FOR COSMIC DUST EXTINCTION?

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

Xie, Xiaoyi; Shen, Shiyin; Shao, Zhengyi

We investigate the luminosity and redshift dependence of the quasar continuum by means of the composite spectrum using a large non-BAL radio-quiet quasar sample drawn from the Sloan Digital Sky Survey. Quasar continuum slopes in the UV-Opt band are measured at two different wavelength ranges, i.e., α{sub ν12} (1000 ∼ 2000 Å) and α{sub ν24} (2000 ∼ 4000 Å) derived from a power-law fitting. Generally, the UV spectra slope becomes harder (higher α{sub ν}) toward higher bolometric luminosity. On the other hand, when quasars are further grouped into luminosity bins, we find that both α{sub ν12} and α{sub ν24} show significant anti-correlationsmore » with redshift (i.e., the quasar continuum becomes redder toward higher redshift). We suggest that the cosmic dust extinction is very likely the cause of this observed α{sub ν} − z relation. We build a simple cosmic dust extinction model to quantify the observed reddening tendency and find an effective dust density nσ{sub v} ∼ 10{sup −5}h Mpc{sup −1} at z < 1.5. The other possibilities that could produce such a reddening effect have also been discussed.« less

The ionizing radiation of Seyfert 2 galactic nuclei

NASA Technical Reports Server (NTRS)

Ho, Luis C.; Shields, Joseph C.; Filippenko, Alexei V.

1993-01-01

We report the discovery of a nonrandom trend in the dispersion of emission-line intensity ratios for Seyfert 2 galaxies. The sense of this pattern suggests the influence of a single physical parameter, the hardness of the ionizing continuum, which controls the heating energy per ionizing photon. We compare the observed line ratios with new photoionization calculations and find that the observed distributions can be reproduced if the ionizing continuum is parametrized by a power law. Our results also suggest an inverse correlation between luminosity and continuum hardness for Seyfert 2 nuclei; if true, this trend extends a similar pattern known in quasars and Seyfert 1 galaxies to active galactic nuclei of lower luminosity. Samples of Seyfert 2 nuclei with improved selection uniformity are desirable for elaboration of these findings.

A Physical Model for the Evolving Ultraviolet Luminosity Function of High Redshift Galaxies and their Contribution to the Cosmic Reionization

NASA Astrophysics Data System (ADS)

Cai, Zhen-Yi; Lapi, Andrea; Bressan, Alessandro; De Zotti, Gianfranco; Negrello, Mattia; Danese, Luigi

2014-04-01

We present a physical model for the evolution of the ultraviolet (UV) luminosity function of high-redshift galaxies, taking into account in a self-consistent way their chemical evolution and the associated evolution of dust extinction. Dust extinction is found to increase fast with halo mass. A strong correlation between dust attenuation and halo/stellar mass for UV selected high-z galaxies is thus predicted. The model yields good fits of the UV and Lyman-α (Lyα) line luminosity functions at all redshifts at which they have been measured. The weak observed evolution of both luminosity functions between z = 2 and z = 6 is explained as the combined effect of the negative evolution of the halo mass function; of the increase with redshift of the star formation efficiency due to the faster gas cooling; and of dust extinction, differential with halo mass. The slope of the faint end of the UV luminosity function is found to steepen with increasing redshift, implying that low luminosity galaxies increasingly dominate the contribution to the UV background at higher and higher redshifts. The observed range of the UV luminosities at high z implies a minimum halo mass capable of hosting active star formation M crit <~ 109.8 M ⊙, which is consistent with the constraints from hydrodynamical simulations. From fits of Lyα line luminosity functions, plus data on the luminosity dependence of extinction, and from the measured ratios of non-ionizing UV to Lyman-continuum flux density for samples of z ~= 3 Lyman break galaxies and Lyα emitters, we derive a simple relationship between the escape fraction of ionizing photons and the star formation rate. It implies that the escape fraction is larger for low-mass galaxies, which are almost dust-free and have lower gas column densities. Galaxies already represented in the UV luminosity function (M UV <~ -18) can keep the universe fully ionized up to z ~= 6. This is consistent with (uncertain) data pointing to a rapid drop of the ionization degree above z ~= 6, such as indications of a decrease of the comoving emission rate of ionizing photons at z ~= 6, a decrease of sizes of quasar near zones, and a possible decline of the Lyα transmission through the intergalactic medium at z > 6. On the other hand, the electron scattering optical depth, τes, inferred from cosmic microwave background (CMB) experiments favor an ionization degree close to unity up to z ~= 9-10. Consistency with CMB data can be achieved if M crit ~= 108.5 M ⊙, implying that the UV luminosity functions extend to M UV ~= -13, although the corresponding τes is still on the low side of CMB-based estimates.

Radio astronomy aspects of the NASA SETI Sky Survey

NASA Technical Reports Server (NTRS)

Klein, Michael J.

1986-01-01

The application of SETI data to radio astronomy is studied. The number of continuum radio sources in the 1-10 GHz region to be counted and cataloged is predicted. The radio luminosity functions for steep and flat spectrum sources at 2, 8, and 22 GHz are derived using the model of Peacock and Gull (1981). The relation between source number and flux density is analyzed and the sensitivity of the system is evaluated.

Structure and kinematics of the broad-line regions in active galaxies from IUE variability data

NASA Technical Reports Server (NTRS)

Koratkar, Anuradha P.; Gaskell, C. Martin

1991-01-01

IUE archival data are used here to investigate the structure nad kinematics of the broad-line regions (BLRs) in nine AGN. It is found that the centroid of the line-continuum cross-correlation functions (CCFs) can be determined with reasonable reliability. The errors in BLR size estimates from CCFs for irregularly sampled light curves are fairly well understood. BLRs are found to have small luminosity-weighted radii, and lines of high ionization tend to be emitted closer to the central source than lines of low ionization, especially for low-luminosity objects. The motion of the gas is gravity-dominated with both pure inflow and pure outflow of high-velocity gas being excluded at a high confidence level for certain geometries.

A near-infrared relationship for estimating black hole masses in active galactic nuclei

NASA Astrophysics Data System (ADS)

Landt, Hermine; Ward, Martin J.; Peterson, Bradley M.; Bentz, Misty C.; Elvis, Martin; Korista, Kirk T.; Karovska, Margarita

2013-06-01

Black hole masses for samples of active galactic nuclei (AGN) are currently estimated from single-epoch optical spectra using scaling relations anchored in reverberation mapping results. In particular, the two quantities needed for calculating black hole masses, namely the velocity and the radial distance of the orbiting gas are derived from the widths of the Balmer hydrogen broad emission lines and the optical continuum luminosity, respectively. We have recently presented a near-infrared (near-IR) relationship for estimating AGN black hole masses based on the widths of the Paschen hydrogen broad emission lines and the total 1 μm continuum luminosity. The near-IR offers several advantages over the optical: it suffers less from dust extinction, the AGN continuum is observed only weakly contaminated by the host galaxy and the strongest Paschen broad emission lines Paα and Paβ are unblended. Here, we improve the calibration of the near-IR black hole mass relationship by increasing the sample from 14 to 23 reverberation-mapped AGN using additional spectroscopy obtained with the Gemini Near-Infrared Spectrograph. The additional sample improves the number statistics in particular at the high-luminosity end.

The MUSE Hubble Ultra Deep Field Survey. VI. The faint-end of the Lyα luminosity function at 2.91 < z < 6.64 and implications for reionisation

NASA Astrophysics Data System (ADS)

Drake, A. B.; Garel, T.; Wisotzki, L.; Leclercq, F.; Hashimoto, T.; Richard, J.; Bacon, R.; Blaizot, J.; Caruana, J.; Conseil, S.; Contini, T.; Guiderdoni, B.; Herenz, E. C.; Inami, H.; Lewis, J.; Mahler, G.; Marino, R. A.; Pello, R.; Schaye, J.; Verhamme, A.; Ventou, E.; Weilbacher, P. M.

2017-11-01

We present the deepest study to date of the Lyα luminosity function in a blank field using blind integral field spectroscopy from MUSE. We constructed a sample of 604 Lyα emitters (LAEs) across the redshift range 2.91 < z < 6.64 using automatic detection software in the Hubble Ultra Deep Field. The deep data cubes allowed us to calculate accurate total Lyα fluxes capturing low surface-brightness extended Lyα emission now known to be a generic property of high-redshift star-forming galaxies. We simulated realistic extended LAEs to fully characterise the selection function of our samples, and performed flux-recovery experiments to test and correct for bias in our determination of total Lyα fluxes. We find that an accurate completeness correction accounting for extended emission reveals a very steep faint-end slope of the luminosity function, α, down to luminosities of log10L erg s-1< 41.5, applying both the 1 /Vmax and maximum likelihood estimators. Splitting the sample into three broad redshift bins, we see the faint-end slope increasing from -2.03-0.07+ 1.42 at z ≈ 3.44 to -2.86-∞+0.76 at z ≈ 5.48, however no strong evolution is seen between the 68% confidence regions in L∗-α parameter space. Using the Lyα line flux as a proxy for star formation activity, and integrating the observed luminosity functions, we find that LAEs' contribution to the cosmic star formation rate density rises with redshift until it is comparable to that from continuum-selected samples by z ≈ 6. This implies that LAEs may contribute more to the star-formation activity of the early Universe than previously thought, as any additional intergalactic medium (IGM) correction would act to further boost the Lyα luminosities. Finally, assuming fiducial values for the escape of Lyα and LyC radiation, and the clumpiness of the IGM, we integrated the maximum likelihood luminosity function at 5.00

Broad-band properties of the CfA Seyfert galaxies. III - Ultraviolet variability

NASA Technical Reports Server (NTRS)

Edelson, R. A.; Pike, G. F.; Krolik, J. H.

1990-01-01

A total of 657 archived IUE spectra are used to study the UV variability properties of six members of the CfA Seyfert I galaxy sample. All show strong evidence for continuum and line variations and a tendency for less luminous objects to be more strongly variable. Most objects show a clear correlation at zero lag between UV spectral index and luminosity, evidence that the variable component is an accretion disk around a black hole which is systematically smaller in less luminous sources. No correlation is seen between the continuum luminosity and equivalent width of the C IV, Mg II, and semiforbidden C III emission lines when the entire sample is examined, but a clear anticorrelation is present when only repeated observations of individual objects are considered. This is due to a combination of light-travel time effects in the broad-line region and the nonlinear responses of lines to continuum fluctuations.

Can Low-Luminosity Galaxies Reionize the Universe?

NASA Astrophysics Data System (ADS)

Ferguson, Harry

2017-08-01

The prevailing wisdom is that low-luminosity galaxies are responsible for cosmic reionization. If this is true, then low-luminosity galaxies at high redshift have to be different from most of the low-luminosity galaxies studied to date at low redshift, which absorb too much of their ionizing radiation. While it is possible that high-z dwarf galaxies have the same metallicity at fixed mass and star-formation rate as low-redshift galaxies, they are different in one key respect. At fixed dark-halo mass, they are probably much denser (having collapsed earlier). This could lead to higher star-formation surface densities more capable of creating cavities in the ISM. But the denser halos of surrounding gas could be harder to clear. There is a critical need for further observations to validate and test physical models for the trends of escaping ionizing continuum with redshift, luminosity, and surface density. JWST will not be able to measure ionizing radiation during the epoch of reionization because the IGM absorbs most of the photons. To prepare for JWST, we need to use the ultraviolet capabilities of HST to measure diverse samples of galaxies at z<3, where we can see the photons and quantify the trends with other galaxy properties. As a complement to other studies, we propose to constrain the Lyman-continuum emission from 8 relatively low-luminosity strongly-lensed galaxies at 1

The XMM-Newton Wide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Page, M. J.; Watson, M. G.; Corral, A.; Tedds, J. A.; Ebrero, J.; Krumpe, M.; Schwope, A.; Ceballos, M. T.

2010-02-01

Aims: We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2-10 keV (rest-frame) luminosities from 1042-1045 erg s-1 and are detected up to redshift 4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods: We fitted the observed 0.2-12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results: We constrained the mean spectral index of the broad band X-ray continuum to <Γ> = 1.96 ± 0.02 with intrinsic dispersion {σ< Γ >} = 0.27-0.02+0.01. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2-10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in ⪆3% of our objects, with rest-frame column densities a few ×1022 cm-2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is 36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT 100 eV and σkT 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.

High resolution radio and optical observations of the central starburst in the low-metallicity dwarf galaxy II Zw 40

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

Kepley, Amanda A.; Reines, Amy E.; Johnson, Kelsey E.

2014-02-01

The extent to which star formation varies in galaxies with low masses, low metallicities, and high star formation rate surface densities is not well constrained. To gain insight into star formation under these physical conditions, this paper estimates the ionizing photon fluxes, masses, and ages for young massive clusters in the central region of II Zw 40—the prototypical low-metallicity dwarf starburst galaxy—from radio continuum and optical observations. Discrete, cluster-sized sources only account for half the total radio continuum emission; the remainder is diffuse. The young (≲ 5 Myr) central burst has a star formation rate surface density that significantly exceedsmore » that of the Milky Way. Three of the 13 sources have ionizing photon fluxes (and thus masses) greater than R136 in 30 Doradus. Although isolating the effects of galaxy mass and metallicity is difficult, the H II region luminosity function and the internal extinction in the center of II Zw 40 appear to be primarily driven by a merger-related starburst. The relatively flat H II region luminosity function may be the result of an increase in interstellar medium pressure during the merger and the internal extinction is similar to that generated by the clumpy and porous dust in other starburst galaxies.« less

Variations in Canonical Star-Forming Laws at Low Metallicity

NASA Astrophysics Data System (ADS)

Monkiewicz, Jacqueline; Bowman, Judd D.; Scowen, Paul

2018-01-01

Empirically-determined star formation relations link observed galaxy luminosities to extrapolated star formation rates at almost every observable wavelength range. These laws are a cornerstone of extragalactic astronomy, and will be critically important for interpreting upcoming observations of early high-redshift protogalaxies with JWST and WFIRST. There are indications at a variety of wavelengths that these canonical relations may become unreliable at the lowest metallicities observed. This potentially complicates interpretation of the earliest protogalaxies, which are expected to be pristine and largely unenriched by stellar nucleosynthesis. Using a sample of 15 local dwarf galaxies with 12+[O/H] < 8.2, I focus on two of these relations: the far-infrared/radio relation and the H-alpha/ultraviolet relation. The sample is chosen to have pre-existing far-IR and UV observations, and to span the full spread of the galaxy mass-metallicity relationship at low luminosity, so that luminosity and metallicity may be examined separately. Radio continuum observations of low metallicity dwarf galaxies 1 Zw 18 and SBS 0335-052E suggest that the far-IR/radio relation probably deviates at low metallicities, but the low luminosity end of the relation is not well sampled. The upgraded Jansky Very Large Array has the sensitivity to fill in this gap. I have obtained 45 hours of L- and C-band continuum data of my dwarf galaxy sample. I present radio continuum imaging of an initial sub-sample of Local Group dwarfs, some of which have never before been detected in radio continuum. The H-alpha/UV relationship is likewise known to become unreliable for dwarf galaxies, though this has been attributed to dwarf galaxy "bursty-ness" rather than metallicity effects. I have conducted a parallel survey of emission line imaging to study the underlying astrophysics of the H-alpha/UV relation. Using Balmer decrement imaging, I map out the pixel-to-pixel dust distribution and geometry within the nearest galaxies in my sample. I compare this to GALEX UV imaging. I discuss implications for UV escape fraction, and present initial results of the canonical star-forming relations at low galaxy luminosity and metallicity. THIS IS A POSTER AND WILL BE LOCATED IN THE AAS BOOTH.

On the Scatter in the Radius-Luminosity Relationship for Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Kilerci Eser, E.; Vestergaard, M.; Peterson, B. M.; Denney, K. D.; Bentz, M. C.

2015-03-01

We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ~40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ~0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ~0.13 dex.

Photometric redshifts for the next generation of deep radio continuum surveys - I. Template fitting

NASA Astrophysics Data System (ADS)

Duncan, Kenneth J.; Brown, Michael J. I.; Williams, Wendy L.; Best, Philip N.; Buat, Veronique; Burgarella, Denis; Jarvis, Matt J.; Małek, Katarzyna; Oliver, S. J.; Röttgering, Huub J. A.; Smith, Daniel J. B.

2018-01-01

We present a study of photometric redshift performance for galaxies and active galactic nuclei detected in deep radio continuum surveys. Using two multiwavelength data sets, over the NOAO Deep Wide Field Survey Boötes and COSMOS fields, we assess photometric redshift (photo-z) performance for a sample of ∼4500 radio continuum sources with spectroscopic redshifts relative to those of ∼63 000 non-radio-detected sources in the same fields. We investigate the performance of three photometric redshift template sets as a function of redshift, radio luminosity and infrared/X-ray properties. We find that no single template library is able to provide the best performance across all subsets of the radio-detected population, with variation in the optimum template set both between subsets and between fields. Through a hierarchical Bayesian combination of the photo-z estimates from all three template sets, we are able to produce a consensus photo-z estimate that equals or improves upon the performance of any individual template set.

Resolving the X-ray emission from the Lyman-continuum emitting galaxy Tol 1247-232

NASA Astrophysics Data System (ADS)

Kaaret, P.; Brorby, M.; Casella, L.; Prestwich, A. H.

2017-11-01

Chandra observations of the nearby, Lyman-continuum (LyC) emitting galaxy Tol 1247-232 resolve the X-ray emission and show that it is dominated by a point-like source with a hard spectrum (Γ = 1.6 ± 0.5) and a high luminosity [(9 ± 2) × 1040 erg s- 1]. Comparison with an earlier XMM-Newton observation shows flux variation of a factor of 2. Hence, the X-ray emission likely arises from an accreting X-ray source: a low-luminosity active galactic nucleus or one or a few X-ray binaries. The Chandra X-ray source is similar to the point-like, hard spectrum (Γ = 1.2 ± 0.2), high-luminosity (1041 erg s- 1) source seen in Haro 11, which is the only other confirmed LyC-emitting galaxy that has been resolved in X-rays. We discuss the possibility that accreting X-ray sources contribute to LyC escape.

ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI

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

Kilerci Eser, E.; Vestergaard, M.; Peterson, B. M.

2015-03-01

We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1more » galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ∼40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ∼0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ∼0.13 dex.« less

A Luminosity Function of Ly(alpha)-Emitting Galaxies at Z [Approx. Equal to] 4.5(Sup 1),(Sup 2)

NASA Technical Reports Server (NTRS)

Dawson, Steve; Rhoads, James E.; Malhotra, Sangeeta; Stern, Daniel; Wang, JunXian; Dey, Arjun; Spinrad, Hyron; Jannuzi, Buell T.

2007-01-01

We present a catalog of 59 z [approx. equal to] 4:5 Ly(alpha)-emitting galaxies spectroscopically confirmed in a campaign of Keck DEIMOS follow-up observations to candidates selected in the Large Are (LALA) narrowband imaging survey.We targeted 97 candidates for spectroscopic follow-up; by accounting for the variety of conditions under which we performed spectroscopy, we estimate a selection reliability of approx.76%. Together with our previous sample of Keck LRIS confirmations, the 59 sources confirmed herein bring the total catalog to 73 spectroscopically confirmed z [approx. equal to] 4:5 Ly(alpha)- emitting galaxies in the [approx. equal to] 0.7 deg(exp 2) covered by the LALA imaging. As with the Keck LRIS sample, we find that a nonnegligible fraction of the co rest-frame equivalent widths (W(sub lambda)(sup rest)) that exceed the maximum predicted for normal stellar populations: 17%-31%(93%confidence) of the detected galaxies show (W(sub lambda)(sup rest)) 12%-27% (90% confidence) show (W(sub lambda)(sup rest)) > 240 A. We construct a luminosity function of z [approx. equal to] 4.5 Ly(alpha) emission lines for comparison to Ly(alpha) luminosity function < 6.6. We find no significant evidence for Ly(alpha) luminosity function evolution from z [approx. equal to] 3 to z [approx. equal to] 6. This result supports the conclusion that the intergalactic me largely reionized from the local universe out to z [approx. equal to] 6.5. It is somewhat at odds with the pronounced drop in the cosmic star formation rate density recently measured between z approx. 3 an z approx. 6 in continuum-selected Lyman-break galaxies, and therefore potentially sheds light on the relationship between the two populations.

Radio continuum of galaxies with H2O megamaser disks: 33 GHz VLA data

NASA Astrophysics Data System (ADS)

Kamali, F.; Henkel, C.; Brunthaler, A.; Impellizzeri, C. M. V.; Menten, K. M.; Braatz, J. A.; Greene, J. E.; Reid, M. J.; Condon, J. J.; Lo, K. Y.; Kuo, C. Y.; Litzinger, E.; Kadler, M.

2017-09-01

Context. Galaxies with H2O megamaser disks are active galaxies in whose edge-on accretion disks 22 GHz H2O maser emission has been detected. Because their geometry is known, they provide a unique view into the properties of active galactic nuclei. Aims: The goal of this work is to investigate the nuclear environment of galaxies with H2O maser disks and to relate the maser and host galaxy properties to those of the radio continuum emission of the galaxy. Methods: The 33 GHz (9 mm) radio continuum properties of 24 galaxies with reported 22 GHz H2O maser emission from their disks are studied in the context of the multiwavelength view of these sources. The 29-37 GHz Ka-band observations are made with the Karl Jansky Very Large Array in B, CnB, or BnA configurations, achieving a resolution of 0.2-0.5 arcsec. Hard X-ray data from the Swift/BAT survey and 22 μm infrared data from WISE, 22 GHz H2O maser data and 1.4 GHz data from NVSS and FIRST surveys are also included in the analysis. Results: Eighty-seven percent (21 out of 24) galaxies in our sample show 33 GHz radio continuum emission at levels of 4.5-240σ. Five sources show extended emission (deconvolved source size larger than 2.5 times the major axis of the beam), including one source with two main components and one with three main components. The remaining detected 16 sources (and also some of the above-mentioned targets) exhibit compact cores within the sensitivity limits. Little evidence is found for extended jets (>300 pc) in most sources. Either they do not exist, or our chosen frequency of 33 GHz is too high for a detection of these supposedly steep spectrum features. In NGC 4388, we find an extended jet-like feature that appears to be oriented perpendicular to the H2O megamaser disk. NGC 2273 is another candidate whose radio continuum source might be elongated perpendicular to the maser disk. Smaller 100-300 pc sized jets might also be present, as is suggested by the beam-deconvolved morphology of our sources. Whenever possible, central positions with accuracies of 20-280 mas are provided. A correlation analysis shows that the 33 GHz luminosity weakly correlates with the infrared luminosity. The 33 GHz luminosity is anticorrelated with the circular velocity of the galaxy. The black hole masses show stronger correlations with H2O maser luminosity than with 1.4 GHz, 33 GHz, or hard X-ray luminosities. Furthermore, the inner radii of the disks show stronger correlations with 1.4 GHz, 33 GHz, and hard X-ray luminosities than their outer radii, suggesting that the outer radii may be affected by disk warping, star formation, or peculiar density distributions.

Rest-frame Optical Spectra and Black Hole Masses of 3 < z < 6 Quasars

NASA Astrophysics Data System (ADS)

Jun, Hyunsung David; Im, Myungshin; Lee, Hyung Mok; Ohyama, Youichi; Woo, Jong-Hak; Fan, Xiaohui; Goto, Tomotsugu; Kim, Dohyeong; Kim, Ji Hoon; Kim, Minjin; Lee, Myung Gyoon; Nakagawa, Takao; Pearson, Chris; Serjeant, Stephen

2015-06-01

We present the rest-frame optical spectral properties of 155 luminous quasars at 3.3 < z < 6.4 taken with the AKARI space telescope, including the first detection of the Hα emission line as far out as z ∼ 6. We extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (AGNs) to the high-luminosity, high-redshift regime that has rarely been probed before. Remarkably, we find that a single log-linear relation can be applied to the 5100 Å and Hα AGN luminosities over a wide range of luminosity (1042 < L5100 < 1047 ergs s-1) or redshift (0 < z < 6), suggesting that the physical mechanism governing this relation is unchanged from z = 0 to 6, over five decades in luminosity. Similar scaling relations are found between the optical and the UV continuum luminosities or line widths. Applying the scaling relations to the Hβ black hole (BH) mass (MBH) estimator of local AGNs, we derive the MBH estimators based on the Hα, Mg ii, and C iv lines, finding that the UV-line-based masses are overall consistent with the Balmer-line-based, but with a large intrinsic scatter of 0.40 dex for the C iv estimates. Our 43 MBH estimates from Hα confirm the existence of BHs as massive as ∼ 1010 M⊙ out to z ∼ 5 and provide a secure footing for previous results from Mg ii-line-based studies that a rapid MBH growth has occurred in the early universe.

Constraining the Active Galactic Nucleus Contribution in a Multiwavelength Study of Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Melendez, M.; Kraemer, S.B.; Schmitt, H.R.; Crenshaw, D.M.; Deo, R.P.; Mushotzky, R.F.; Bruhweiler, F.C.

2008-01-01

We have studied the relationship between the high- and low-ionization [O IV] (lambda)25.89 microns, [Ne III] (lambda)15.56 microns, and [Ne II] (lambda)12.81 microns emission lines with the aim of constraining the active galactic nuclei (AGNs) and star formation contributions for a sample of 103 Seyfert galaxies.We use the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas.We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGNs, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGNs and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of approx.1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation, we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies.We examined the mid- and far-infrared continua and found that [Ne II] is well correlated with the continuum luminosity at 60 microns and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGNs and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

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

Mancuso, C.; Prandoni, I.; Lapi, A.

We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, which will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. to compute the star formation rate functions, the AGN duty cycles, and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statisticsmore » at different radio frequencies and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. These specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the Square Kilometre Array and its precursors.« less

Long time scale hard X-ray variability in Seyfert 1 galaxies

NASA Astrophysics Data System (ADS)

Markowitz, Alex Gary

This dissertation examines the relationship between long-term X-ray variability characteristics, black hole mass, and luminosity of Seyfert 1 Active Galactic Nuclei. High dynamic range power spectral density functions (PSDs) have been constructed for six Seyfert 1 galaxies. These PSDs show "breaks" or characteristic time scales, typically on the order of a few days. There is resemblance to PSDs of lower-mass Galactic X-ray binaries (XRBs), with the ratios of putative black hole masses and variability time scales approximately the same (106--7) between the two classes of objects. The data are consistent with a linear correlation between Seyfert PSD break time scale and black hole mass estimate; the relation extrapolates reasonably well over 6--7 orders of magnitude to XRBs. All of this strengthens the case for a physical similarity between Seyfert galaxies and XRBs. The first six years of RXTE monitoring of Seyfert 1s have been systematically analyzed to probe hard X-ray variability on multiple time scales in a total of 19 Seyfert is in an expansion of the survey of Markowitz & Edelson (2001). Correlations between variability amplitude, luminosity, and black hole mass are explored, the data support the model of PSD movement with black hole mass suggested by the PSD survey. All of the continuum variability results are consistent with relatively more massive black holes hosting larger X-ray emission regions, resulting in 'slower' observed variability. Nearly all sources in the sample exhibit stronger variability towards softer energies, consistent with softening as they brighten. Direct time-resolved spectral fitting has been performed on continuous RXTE monitoring of seven Seyfert is to study long-term spectral variability and Fe Kalpha variability characteristics. The Fe Kalpha line displays a wide range of behavior but varies less strongly than the broadband continuum. Overall, however, there is no strong evidence for correlated variability between the line and continuum, severely challenging models in which the line tracks continuum variations modified only by a light-travel time delay. This experiment yields further support for spectral softening as continuum flux increases.

Discovery of a Kiloparsec Extended Hard X-Ray Continuum and Fe-Kα from the Compton Thick AGN ESO 428-G014

NASA Astrophysics Data System (ADS)

Fabbiano, G.; Elvis, M.; Paggi, A.; Karovska, M.; Maksym, W. P.; Raymond, J.; Risaliti, G.; Wang, Junfeng

2017-06-01

We report the discovery of kiloparsec-scale diffuse emission in both the hard continuum (3-6 keV) and in the Fe-Kα line in the Compton thick (CT) Seyfert galaxy ESO 428-G014. This extended hard component contains at least ˜24% of the observed 3-8 keV emission, and follows the direction of the extended optical line emission (ionization cone) and radio jet. The extended hard component has ˜0.5% of the intrinsic 2-10 keV luminosity within the bi-cones. A uniform scattering medium of density 1 {{cm}}-3 would produce this luminosity in a 1 kpc path length in the bi-cones. Alternatively, higher column density molecular clouds in the disk of ESO 428-G014 may be responsible for these components. The continuum may also be enhanced by the acceleration of charged particles in the radio jet. The steeper spectrum (Γ ˜ 1.7 ± 0.4) of the hard continuum outside of the central 1.″5 radius nuclear region suggests a contribution of scattered/fluorescent intrinsic Seyfert emission. Ultrafast nuclear outflows cannot explain the extended Fe-Kα emission. This discovery suggests that we may need to revise the picture at the base of our interpretation of CT AGN spectra.

Calibration and Limitations of the Mg II Line-based Black Hole Masses

NASA Astrophysics Data System (ADS)

Woo, Jong-Hak; Le, Huynh Anh N.; Karouzos, Marios; Park, Dawoo; Park, Daeseong; Malkan, Matthew A.; Treu, Tommaso; Bennert, Vardha N.

2018-06-01

We present single-epoch black hole mass ({M}BH}) calibrations based on the rest-frame ultraviolet (UV) and optical measurements of Mg II 2798 Å and Hβ 4861 Å lines and the active galactic nucleus (AGN) continuum, using a sample of 52 moderate-luminosity AGNs at z ∼ 0.4 and z ∼ 0.6 with high-quality Keck spectra. We combine this sample with a large number of luminous AGNs from the Sloan Digital Sky Survey to increase the dynamic range for a better comparison of UV and optical velocity and luminosity measurements. With respect to the reference {M}BH} based on the line dispersion of Hβ and continuum luminosity at 5100 Å, we calibrate the UV and optical mass estimators by determining the best-fit values of the coefficients in the mass equation. By investigating whether the UV estimators show a systematic trend with Eddington ratio, FWHM of Hβ, Fe II strength, or UV/optical slope, we find no significant bias except for the slope. By fitting the systematic difference of Mg II-based and Hβ-based masses with the L 3000/L 5100 ratio, we provide a correction term as a function of the spectral index as ΔC = 0.24 (1 + α λ ) + 0.17, which can be added to the Mg II-based mass estimators if the spectral slope can be well determined. The derived UV mass estimators typically show >∼0.2 dex intrinsic scatter with respect to the Hβ-based {M}BH}, suggesting that the UV-based mass has an additional uncertainty of ∼0.2 dex, even if high-quality rest-frame UV spectra are available.

A possible width-luminosity correlation of the Ca II K1 and Mg II k1 features. [of stellar atmospheres

NASA Technical Reports Server (NTRS)

Ayres, T. R.; Shine, R. A.; Linsky, J. L.

1975-01-01

Existing high resolution stellar profiles of the Ca II and Mg II resonance lines suggest a possible width-luminosity correlation of the K1 minimum features. It is shown that such a correlation can be simply understood if the continuum optical depth of the stellar temperature minimum is relatively independent of surface gravity as suggested by three stars studied in detail.

A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

NASA Technical Reports Server (NTRS)

Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

2002-01-01

Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe.

DUST CONTINUUM EMISSION AS A TRACER OF GAS MASS IN GALAXIES

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

Groves, Brent A.; Schinnerer, Eva; Walter, Fabian

2015-01-20

We use a sample of 36 galaxies from the KINGFISH (Herschel IR), HERACLES (IRAM CO), and THINGS (Very Large Array H I) surveys to study empirical relations between Herschel infrared (IR) luminosities and the total mass of the interstellar gas (H{sub 2} + H I). Such a comparison provides a simple empirical relationship without introducing the uncertainty of dust model fitting. We find tight correlations, and provide fits to these relations, between Herschel luminosities and the total gas mass integrated over entire galaxies, with the tightest, almost linear, correlation found for the longest wavelength data (SPIRE 500). However, we findmore » that accounting for the gas-phase metallicity (affecting the dust to gas ratio) is crucial when applying these relations to low-mass, and presumably high-redshift, galaxies. The molecular (H{sub 2}) gas mass is found to be better correlated with the peak of the IR emission (e.g., PACS160), driven mostly by the correlation of stellar mass and mean dust temperature. When examining these relations as a function of galactocentric radius, we find the same correlations, albeit with a larger scatter, up to a radius of r ∼ 0.7 r {sub 25} (containing most of a galaxy's baryonic mass). However, beyond that radius, the same correlations no longer hold, with increasing gas (predominantly H I) mass relative to the infrared emission. The tight relations found for the bulk of the galaxy's baryonic content suggest that total gas masses of disk-like (non-merging/ULIRG) galaxies can be inferred from far-infrared continuum measurements in situations where only the latter are available, e.g., in ALMA continuum observations of high-redshift galaxies.« less

The Sloan Digital Sky Survey Reverberation Mapping Project: Ensemble Spectroscopic Variability of Quasar Broad Emission Lines

NASA Astrophysics Data System (ADS)

Sun, Mouyuan; Trump, Jonathan R.; Shen, Yue; Brandt, W. N.; Dawson, Kyle; Denney, Kelly D.; Hall, Patrick B.; Ho, Luis C.; Horne, Keith; Jiang, Linhua; Richards, Gordon T.; Schneider, Donald P.; Bizyaev, Dmitry; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey

2015-09-01

We explore the variability of quasars in the Mg ii and {{H}}β broad emission lines and ultraviolet/optical continuum emission using the Sloan Digital Sky Survey Reverberation Mapping project (SDSS-RM). This is the largest spectroscopic study of quasar variability to date: our study includes 29 spectroscopic epochs from SDSS-RM over 6 months, containing 357 quasars with Mg ii and 41 quasars with {{H}}β . On longer timescales, the study is also supplemented with two-epoch data from SDSS-I/II. The SDSS-I/II data include an additional 2854 quasars with Mg ii and 572 quasars with {{H}}β . The Mg ii emission line is significantly variable ({{Δ }}f/f∼ 10% on ∼100-day timescales), a necessary prerequisite for its use for reverberation mapping studies. The data also confirm that continuum variability increases with timescale and decreases with luminosity, and the continuum light curves are consistent with a damped random-walk model on rest-frame timescales of ≳ 5 days. We compare the emission-line and continuum variability to investigate the structure of the broad-line region. Broad-line variability shows a shallower increase with timescale compared to the continuum emission, demonstrating that the broad-line transfer function is not a δ-function. {{H}}β is more variable than Mg ii (roughly by a factor of ∼1.5), suggesting different excitation mechanisms, optical depths and/or geometrical configuration for each emission line. The ensemble spectroscopic variability measurements enabled by the SDSS-RM project have important consequences for future studies of reverberation mapping and black hole mass estimation of 1\\lt z\\lt 2 quasars.

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

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

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 ofmore » 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.« less

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

NASA Technical Reports Server (NTRS)

Grindlay, J. E.; Forman, W. R.; Steiner, J. E.; Canizares, C. R.; Mcclintock, J. E.

1980-01-01

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

ALMA observation of 158 μm [C II] line and dust continuum of a z = 7 normally star-forming galaxy in the epoch of reionization

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

Ota, Kazuaki; Walter, Fabian; Da Cunha, Elisabete

We present ALMA observations of the [C II] line and far-infrared (FIR) continuum of a normally star-forming galaxy in the reionization epoch, the z = 6.96 Lyα emitter (LAE) IOK-1. Probing to sensitivities of σ{sub line} = 240 μJy beam{sup –1} (40 km s{sup –1} channel) and σ{sub cont} = 21 μJy beam{sup –1}, we found the galaxy undetected in both [C II] and continuum. Comparison of ultraviolet (UV)-FIR spectral energy distribution (SED) of IOK-1, including our ALMA limit, with those of several types of local galaxies (including the effects of the cosmic microwave background, CMB, on the FIR continuum)more » suggests that IOK-1 is similar to local dwarf/irregular galaxies in SED shape rather than highly dusty/obscured galaxies. Moreover, our 3σ FIR continuum limit, corrected for CMB effects, implies intrinsic dust mass M {sub dust} < 6.4 × 10{sup 7} M {sub ☉}, FIR luminosity L {sub FIR} < 3.7 × 10{sup 10} L {sub ☉} (42.5-122.5 μm), total IR luminosity L {sub IR} < 5.7 × 10{sup 10} L {sub ☉} (8-1000 μm), and dust-obscured star formation rate (SFR) < 10 M {sub ☉} yr{sup –1}, if we assume that IOK-1 has a dust temperature and emissivity index typical of local dwarf galaxies. This SFR is 2.4 times lower than one estimated from the UV continuum, suggesting that <29% of the star formation is obscured by dust. Meanwhile, our 3σ [C II] flux limit translates into [C II] luminosity, L {sub [C} {sub II]} < 3.4 × 10{sup 7} L {sub ☉}. Locations of IOK-1 and previously observed LAEs on the L {sub [C} {sub II]} versus SFR and L {sub [C} {sub II]}/L {sub FIR} versus L {sub FIR} diagrams imply that LAEs in the reionization epoch have significantly lower gas and dust enrichment than AGN-powered systems and starbursts at similar/lower redshifts, as well as local star-forming galaxies.« less

Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

NASA Technical Reports Server (NTRS)

Mushotzy, Richard F.; Winter, Lisa M.; McIntosh, Daniel H.; Tueller, Jack

2008-01-01

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of 10(exp 3) in luminosity (L(sub IR) approx.equals L(sub BAT)(sup 1.25) and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.

High redshift QSOs and the x ray background

NASA Technical Reports Server (NTRS)

Impey, Chris

1993-01-01

ROSAT pointed observations were made of 9 QSO's from the Large Bright Quasar Survey (LBQS). The LBQS is based on machine measurement of objective prism plates taken with the UK Schmidt Telescope. Software has been used to select QSO's by both color and by the presence of spectral features and continuum breaks. The probability of detection can be calculated as a function of magnitude, redshift and spectral features, and the completeness of the survey can be accurately estimated. Nine out of 1040 QSO's in the LBQS have z greater than 3. The observations will provide an important data point in the X-ray luminosity function of QSO's at high redshift. The QSO's with z greater than 3 span less than a magnitude in M(sub B), so can be combined as a homogeneous sample. This analysis is only possible with a sample drawn from a large and complete catalog such as the LBQS. Four of the 9 QSO's that were observed with the ROSAT PSPC for this proposal were detected, including one of the most luminous X-ray sources ever observed. The April 1992 version of the PROS DETECT package was used to reduce the data. The results have been used to search for evolution of the X-ray properties of QSO's in redshift. The 9 QSO's lie in the range -28.7 less than M(sub B) less than -27.8. When combined with data for 16 QSO's in a similar luminosity range at lower redshift correlations with luminosity and redshift can be separated out. The LBQS sample also yields a new constraint on the contribution of high redshift QSO's to the X-ray background. An initial requirement is knowledge of the X-ray properties (alpha(sub OX)) as a function of redshift. Integration over the evolving luminosity function of the LBQS then gives the QSO contribution to the source counts.

WIND STRUCTURE AND LUMINOSITY VARIATIONS IN THE WOLF-RAYET/LUMINOUS BLUE VARIABLE HD 5980

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

Georgiev, Leonid; Koenigsberger, Gloria; Hillier, D. John

Over the past 40 years, the massive luminous blue variable/Wolf-Rayet system HD 5980 in the Small Magellanic Cloud (SMC) has undergone a long-term S Doradus-type variability cycle and two brief and violent eruptions in 1993 and 1994. In this paper we analyze a collection of UV and optical spectra obtained between 1979 and 2009 and perform CMFGEN model fits to spectra of 1994, 2000, 2002, and 2009. The results are as follows: (1) the long-term S Dor-type variability is associated with changes of the hydrostatic radius; (2) the 1994 eruption involved changes in its bolometric luminosity and wind structure; (3)more » the emission-line strength, the wind velocity, and the continuum luminosity underwent correlated variations in the sense that a decreasing V{sub {infinity}} is associated with increasing emission line and continuum levels; and (4) the spectrum of the third star in the system (Star C) is well fit by a T{sub eff} = 32 K model atmosphere with SMC chemical abundances. For all epochs, the wind of the erupting star is optically thick at the sonic point and is thus driven mainly by the continuum opacity. We speculate that the wind switches between two stable regimes driven by the 'hot' (during the eruption) and the 'cool' (post-eruption) iron opacity bumps as defined by Lamers and Nugis and Graefener and Hamann, and thus the wind may undergo a bi-stability jump of a different nature from that which occurs in OB stars.« less

The 'Baldwin Effect' in Wolf-Rayet stars

NASA Technical Reports Server (NTRS)

Morris, Patrick; Conti, Peter S.; Lamers, Henny J. G. L. M.; Koenigsberger, Gloria

1993-01-01

The equivalent widths of a number of emission lines in the spectra of WN-type Wolf-Rayet stars are found to inversely correlate with the luminosity of the underlying continuum. This is the well-known Baldwin Effect that has previously been observed in quasars and some Seyfert I galaxies. The Effect can be inferred from line and continuum predictions in published non-LTE model helium atmospheres and is explainable in terms of differences in wind density among WN stars. Using a simple wind model, we show that the Effect arises from the fact that both the effective radius for the local continuum and the emission measure of the layers above the continuum-forming region depend on the density in the wind. The Effect provides a new method for distance determinations of W-R stars.

Structure and chemistry in the northwestern condensation of the Serpens molecular cloud core

NASA Technical Reports Server (NTRS)

Mcmullin, Joseph P.; Mundy, Lee G.; Wilking, Bruce A.; Hezel, T.; Blake, Geoff A.

1994-01-01

We present single-dish and interferometric observations of gas and dust in the core of the Serpens molecular cloud, focusing on the northwestern condensation. Single-dish molecular line observations are used to probe the structure and chemistry of the condensation while high-resolution images of CS and CH30H are combined with continuum observations from lambda = 1.3 mm to lambda = 3.5 cm to study the subcondensations and overall distribution of dust. For the northwestern condensation, we derive a characteristic density of 3 x 10(exp 5)/ cu cm and an estimated total mass of approximately 70 solar mass. We find compact molecular emission associated with the far-infrared source S68 FIRS 1, and with a newly detected subcondensation named S68 N. Comparison of the large-and small-scale emission reveals that most of the material in the northwest condensation is not directly associated with these compact sources, suggesting a youthful age for this region. CO J = 1 approaches 0 observations indicate widespread outflow activity. However, no unique association of embedded objects with outflows is possible with our observations. The SiO emission is found to be extended with the overall emission centered about S68 FIRS 1; the offset of the peak emission from all of the known continuum sources and the coincidence between the blueshifted SiO emission and blueshifted high-velocity gas traced by CO and CS is consistent with formation of SiO in shocks. Derived abundances of CO and HCO(+) are consistent with quiescent and other star-forming regions while CS, HCN, and H2CO abundances indicate mild depletions within the condensation. Spectral energy distribution fits to S68 FIRS 1 indicate a modest luminosity (50-60 solar luminosity), implying that it is a low-mass (0.5-3 solar mass) young stellar object. Radio continuum observations of the triple source toward S68 FIRS 1 indicate that the lobe emission is varying on timescales less than or equal to 1 yr while the central component is relatively constant over approximately 14 yr. The nature of a newly detected compact emission region, S68 N, is less certain due to the absence of firm continuum detections; based on its low luminosity (less than 5 solar luminosity) and strong molecular emission, S68 N may be prestellar subcondensation of gas and dust.

The Nature of VeLLOs

NASA Astrophysics Data System (ADS)

Huard, Tracy L.; Pound, Marc W.; Mundy, Lee; Dunham, Michael

2018-01-01

Very Low Luminosity Objects (VeLLOs) are young stellar sources that are defined by luminosities less than 0.1 solar luminosity and rising mid-infrared spectral energy distributions. But, what exactly are they? Brown dwarfs or low-mass stars in formation? Systems exhibiting low accretion rates? Extremely young objects? We have completed an ALMA survey of 33 candidates in the nearby Serpens, Ophiuchus, and Lupus star-forming molecular clouds. Continuum emission at 1.3 mm, consistent with the presence of an inner envelope and/or disk, was detected toward 17 candidates, with at least 6 of these candidates exhibiting CO outflow emission, suggesting ongoing formation. We will present these observations and results, and discuss their implications concerning the nature of VeLLOs.

Exploring the Faint End of the Luminosity-Metallicity Relation with Hα Dots

NASA Astrophysics Data System (ADS)

Hirschauer, Alec S.; Salzer, John J.

2015-01-01

The well-known correlation between a galaxy's luminosity and its gas-phase oxygen abundance (the luminosity-metallicity (L-Z) relation) offers clues toward our understanding of chemical enrichment histories and evolution. Bright galaxies are comparatively better studied than faint ones, leaving a relative dearth of observational data points to constrain the L-Z relation in the low-luminosity regime. We present high S/N nebular spectroscopy of low-luminosity star-forming galaxies observed with the KPNO 4m using the new KOSMOS spectrograph to derive direct-method metallicities. Our targets are strong point-like emission-line sources discovered serendipitously in continuum-subtracted narrowband images from the ALFALFA Hα survey. Follow-up spectroscopy of these "Hα dots" shows that these objects represent some of the lowest luminosity star-forming systems in the local Universe. Our KOSMOS spectra cover the full optical region and include detection of [O III] λ4363 in roughly a dozen objects. This paper presents some of the first scientific results obtained using this new spectrograph, and demonstrates its capabilities and effectiveness in deriving direct-method metallicities of faint objects.

Evidence for different accretion regimes in GRO J1008-57

NASA Astrophysics Data System (ADS)

Kühnel, Matthias; Fürst, Felix; Pottschmidt, Katja; Kreykenbohm, Ingo; Ballhausen, Ralf; Falkner, Sebastian; Rothschild, Richard E.; Klochkov, Dmitry; Wilms, Jörn

2017-11-01

We present a comprehensive spectral analysis of the BeXRB GRO J1008-57 over a luminosity range of three orders of magnitude using NuSTAR, Suzaku, and RXTE data. We find significant evolution of the spectral parameters with luminosity. In particular, the photon index hardens with increasing luminosity at intermediate luminosities in the range 1036-1037 erg s-1. This evolution is stable and repeatedly observed over different outbursts. However, at the extreme ends of the observed luminosity range, we find that the correlation breaks down, with a significance level of at least 3.7σ. We conclude that these changes indicate transitions to different accretion regimes, which are characterized by different deceleration processes, such as Coulomb or radiation breaking. We compare our observed luminosity levels of these transitions to theoretical predications and discuss the variation of those theoretical luminosity values with fundamental neutron star parameters. Finally, we present detailed spectroscopy of the unique "triple peaked" outburst in 2014/15 which does not fit in the general parameter evolution with luminosity. The pulse profile on the other hand is consistent with what is expected at this luminosity level, arguing against a change in accretion geometry. In summary, GRO J1008-57 is an ideal target to study different accretion regimes due to the well-constrained evolution of its broad-band spectral continuum over several orders of magnitude in luminosity.

The star formation rate cookbook at 1 < z < 3: Extinction-corrected relations for UV and [OII]λ3727 luminosities

NASA Astrophysics Data System (ADS)

Talia, M.; Cimatti, A.; Pozzetti, L.; Rodighiero, G.; Gruppioni, C.; Pozzi, F.; Daddi, E.; Maraston, C.; Mignoli, M.; Kurk, J.

2015-10-01

Aims: In this paper we use a well-controlled spectroscopic sample of galaxies at 1

Populations of High-Luminosity Density-Bounded HII Regions in Spiral Galaxies? Evidence and Implications

NASA Technical Reports Server (NTRS)

Beckman, J. E.; Rozas, M.; Zurita, A.; Watson, R. A.; Knapen, J. H.

2000-01-01

In this paper we present evidence that the H II regions of high luminosity in disk galaxies may be density bounded, so that a significant fraction of the ionizing photons emitted by their exciting OB stars escape from the regions. The key piece of evidence is the presence, in the Ha luminosity functions (LFs) of the populations of H iI regions, of glitches, local sharp peaks at an apparently invariant luminosity, defined as the Stromgren luminosity Lstr), LH(sub alpha) = Lstr = 10(sup 38.6) (+/- 10(sup 0.1)) erg/ s (no other peaks are found in any of the LFs) accompanying a steepening of slope for LH(sub alpha) greater than Lstr This behavior is readily explicable via a physical model whose basic premises are: (a) the transition at LH(sub alpha) = Lstr marks a change from essentially ionization bounding at low luminosities to density bounding at higher values, (b) for this to occur the law relating stellar mass in massive star-forming clouds to the mass of the placental cloud must be such that the ionizing photon flux produced within the cloud is a function which rises more steeply than the mass of the cloud. Supporting evidence for the hypothesis of this transition is also presented: measurements of the central surface brightnesses of H II regions for LH(sub alpha) less than Lstr are proportional to L(sup 1/3, sub H(sub alpha)), expected for ionization bounding, but show a sharp trend to a steeper dependence for LH(sub alpha) greater than Lstr, and the observed relation between the internal turbulence velocity parameter, sigma, and the luminosity, L, at high luminosities, can be well explained if these regions are density bounded. If confirmed, the density-bounding hypothesis would have a number of interesting implications. It would imply that the density-bounded regions were the main sources of the photons which ionize the diffuse gas in disk galaxies. Our estimates, based on the hypothesis, indicate that these regions emit sufficient Lyman continuum not only to ionize the diffuse medium, but to cause a typical spiral to emit significant ionizing flux into the intergalactic medium. The low scatter observed in Lstr, less than 0.1 mag rms in the still quite small sample measured to date, is an invitation to widen the data base, and to calibrate against primary standards, with the aim of obtaining a precise, approx. 10(exp 5) solar luminosity widely distributed standard candle.

GRS 1739-278 Observed at Very Low Luminosity with XMM-Newton and NuSTAR

NASA Astrophysics Data System (ADS)

Fürst, F.; Tomsick, J. A.; Yamaoka, K.; Dauser, T.; Miller, J. M.; Clavel, M.; Corbel, S.; Fabian, A.; García, J.; Harrison, F. A.; Loh, A.; Kaaret, P.; Kalemci, E.; Migliari, S.; Miller-Jones, J. C. A.; Pottschmidt, K.; Rahoui, F.; Rodriguez, J.; Stern, D.; Stuhlinger, M.; Walton, D. J.; Wilms, J.

2016-12-01

We present a detailed spectral analysis of XMM-Newton and NuSTAR observations of the accreting transient black hole GRS 1739-278 during a very faint low hard state at ˜0.02% of the Eddington luminosity (for a distance of 8.5 kpc and a mass of 10 {M}⊙ ). The broadband X-ray spectrum between 0.5 and 60 keV can be well-described by a power-law continuum with an exponential cutoff. The continuum is unusually hard for such a low luminosity, with a photon index of Γ = 1.39 ± 0.04. We find evidence for an additional reflection component from an optically thick accretion disk at the 98% likelihood level. The reflection fraction is low, with {{ R }}{refl}={0.043}-0.023+0.033. In combination with measurements of the spin and inclination parameters made with NuSTAR during a brighter hard state by Miller et al., we seek to constrain the accretion disk geometry. Depending on the assumed emissivity profile of the accretion disk, we find a truncation radius of 15-35 {R}{{g}} (5-12 {R}{ISCO}) at the 90% confidence limit. These values depend strongly on the assumptions and we discuss possible systematic uncertainties.

Imaging the nuclear environment of NGC 1365 with the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Kristen, Helmuth; Jorsater, Steven; Lindblad, Per Olof; Boksenberg, Alec

1997-12-01

The region surrounding the active nucleus of the barred spiral galaxy NGC 1365 is observed in the [Oiii] lambda 5007 line and neighbouring continuum using the Faint Object Camera (FOC) aboard the Hubble Space Telescope (HST). In the continuum light numerous bright ``super star clusters'' (SSCs) are seen in the nuclear region. They tend to fall on an elongated ring around the nucleus and contribute about 20 % of the total continuum flux in this wavelength regime. Without applying any extinction correction the brightest SSCs have an absolute luminosity M_B=-14fm1 +/- 0fm3 and are very compact with radii R la 3 pc. Complementary ground-based spectroscopy gives an extinction estimate A_B = 2fm5 +/- 0fm5 towards these regions, indicating a true luminosity M_B = -16fm6 +/- 0fm6 . The bright compact radio source NGC 1365:A is found to coincide spatially with one of the SSCs. We conclude that it is a ``radio supernova''. The HST observations resolve the inner structure of the conical outflow previously seen in the [Oiii] lambda 5007 line in ground-based observations, and reveal a complicated structure of individual emission-line clouds, some of which gather in larger agglomerations. The total luminosity in the [Oiii] line amounts to L_[OIII] =~ 3.7x 10(40) erg s(-1) where about 40 % is emitted by the clouds. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555, and observations at the European Southern Observatory (ESO), La Silla, Chile.

EVLA Observation of Centimeter Continuum Emission from Protostars in Serpens South

NASA Astrophysics Data System (ADS)

Kern, Nicholas S.; Tobin, John J.; Keown, Jared A.; Gutermuth, Robert A.

2015-01-01

Serpens South is a protocluster with an unusually high abundance of Class 0 and I protostars, suggesting it is in a very early phase of star formation and may eventually form a star cluster. Following its discovery in 2008 with the Spitzer space telescope, infrared and millimeter observations and analysis quickly followed, however, Serpens South has yet to be fully explored in the radio. Radio observations at centimeter wavelengths have long been used as a tool to probe the dynamical processes of young protostars that are still heavily shrouded in their protostellar envelopes and thus cannot be seen at longer wavelengths. Radio observations then become an important tool in understanding Serpens South due to its young age. To this end, we have conducted EVLA C band continuum observations of the central region of the Serpens South protostellar cluster in order to map the centimeter continuum emission in a region of high Class 0 / I protostellar surface density. We report the detection of centimeter emission corresponding to protostars identified by Spitzer, and to protostars identified but blended by Herschel. We characterize their centimeter emission, and put them in context with previous Spitzer and Herschel infrared and far-infrared observations, as well as IRAM millimeter observations. Additionally, we make an assessment of the protostars' bolometric luminosity, and compare them to the known protostellar 3.6 cm to 6.0 cm luminosity vs. bolometric luminosity relation. With the EVLA, we present a mid-resolution map of centimeter emission from the central region of Serpens South with the highest sensitivity to date, with a beam size of ~5 arcseconds and rms on the order of 15 microJansky.

Super-Eddington accreting massive black holes as long-lived cosmological standards.

PubMed

Wang, Jian-Min; Du, Pu; Valls-Gabaud, David; Hu, Chen; Netzer, Hagai

2013-02-22

Super-Eddington accreting massive black holes (SEAMBHs) reach saturated luminosities above a certain accretion rate due to photon trapping and advection in slim accretion disks. We show that these SEAMBHs could provide a new tool for estimating cosmological distances if they are properly identified by hard x-ray observations, in particular by the slope of their 2-10 keV continuum. To verify this idea we obtained black hole mass estimates and x-ray data for a sample of 60 narrow line Seyfert 1 galaxies that we consider to be the most promising SEAMBH candidates. We demonstrate that the distances derived by the new method for the objects in the sample get closer to the standard luminosity distances as the hard x-ray continuum gets steeper. The results allow us to analyze the requirements for using the method in future samples of active black holes and to demonstrate that the expected uncertainty, given large enough samples, can make them into a useful, new cosmological ruler.

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei XVI: A 13 Year Study of Spectral Variability in NGC 5548

NASA Technical Reports Server (NTRS)

Peterson, B. M.; Berlind, P.; Bertram, R.; Bischoff, K.; Bochkarev, N. G.; Burenkov, A. N.; Calkins, M.; Carrasco, L.; Chavushyan, V. H.

2002-01-01

We present the final installment of an intensive 13 year study of variations of the optical continuum and broad H beta emission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 H beta measurements. The H beta variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction between the size of the broad-line region and the ionizing luminosity, r is proportional to L(sup 1/2)(sub ion). Moreover, the apparently linear nature of the correlation between the H beta response time and the nonstellar optical continuum F(sub opt) arises as a consequence of the changing shape of the continuum as it varies, specifically F(sub opt) is proportional to F(sup 0.56)(sub UV).

The mean ultraviolet spectrum of a representative sample of faint z ˜ 3 Lyman alpha emitters

NASA Astrophysics Data System (ADS)

Nakajima, Kimihiko; Fletcher, Thomas; Ellis, Richard S.; Robertson, Brant E.; Iwata, Ikuru

2018-06-01

We discuss the rest-frame ultraviolet (UV) emission line spectra of a large (˜100) sample of low luminosity redshift z ˜ 3.1 Lyman alpha emitters (LAEs) drawn from a Subaru imaging survey in the SSA22 survey field. Our earlier work based on smaller samples indicated that such sources have high [O III]/[O II] line ratios possibly arising from a hard ionizing spectrum that may be typical of similar sources in the reionization era. With optical spectra secured from VLT/VIMOS, we re-examine the nature of the ionizing radiation in a larger sample using the strength of the high ionization diagnostic emission lines of CIII]λ1909, CIVλ1549, HEIIλ1640, and O III]λλ1661, 1666 Å in various stacked subsets. Our analysis confirms earlier suggestions of a correlation between the strength of Ly α and CIII] emission and we find similar trends with broad-band UV luminosity and rest-frame UV colour. Using various diagnostic line ratios and our stellar photoionization models, we determine both the gas phase metallicity and hardness of the ionization spectrum characterized by ξion - the number of Lyman continuum photons per UV luminosity. We confirm our earlier suggestion that ξion is significantly larger for LAEs than for continuum-selected Lyman break galaxies, particularly for those LAEs with the faintest UV luminosities. We briefly discuss the implications for cosmic reionization if the metal-poor intensely star-forming systems studied here are representative examples of those at much higher redshift.

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ≳ 6 studied with ALMA

NASA Astrophysics Data System (ADS)

Izumi, Takuma; Onoue, Masafusa; Shirakata, Hikari; Nagao, Tohru; Kohno, Kotaro; Matsuoka, Yoshiki; Imanishi, Masatoshi; Strauss, Michael A.; Kashikawa, Nobunari; Schulze, Andreas; Silverman, John D.; Fujimoto, Seiji; Harikane, Yuichi; Toba, Yoshiki; Umehata, Hideki; Nakanishi, Kouichiro; Greene, Jenny E.; Tamura, Yoichi; Taniguchi, Akio; Yamaguchi, Yuki; Goto, Tomotsugu; Hashimoto, Yasuhiro; Ikarashi, Soh; Iono, Daisuke; Iwasawa, Kazushi; Lee, Chien-Hsiu; Makiya, Ryu; Minezaki, Takeo; Tang, Ji-Jia

2018-04-01

We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L_[C II] = (3.8-10.2)× 108 L_{⊙} and LFIR = (1.2-2.0) × 1011 L_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≃ 23-40 M_{⊙} yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L_[C II]/L_FIR ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 M_{⊙}. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ˜ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). III. Star formation properties of the host galaxies at z ≳ 6 studied with ALMA

NASA Astrophysics Data System (ADS)

Izumi, Takuma; Onoue, Masafusa; Shirakata, Hikari; Nagao, Tohru; Kohno, Kotaro; Matsuoka, Yoshiki; Imanishi, Masatoshi; Strauss, Michael A.; Kashikawa, Nobunari; Schulze, Andreas; Silverman, John D.; Fujimoto, Seiji; Harikane, Yuichi; Toba, Yoshiki; Umehata, Hideki; Nakanishi, Kouichiro; Greene, Jenny E.; Tamura, Yoichi; Taniguchi, Akio; Yamaguchi, Yuki; Goto, Tomotsugu; Hashimoto, Yasuhiro; Ikarashi, Soh; Iono, Daisuke; Iwasawa, Kazushi; Lee, Chien-Hsiu; Makiya, Ryu; Minezaki, Takeo; Tang, Ji-Jia

2018-06-01

We present our ALMA Cycle 4 measurements of the [C II] emission line and the underlying far-infrared (FIR) continuum emission from four optically low-luminosity (M1450 > -25) quasars at z ≳ 6 discovered by the Subaru Hyper Suprime Cam (HSC) survey. The [C II] line and FIR continuum luminosities lie in the ranges L_[C II] = (3.8-10.2)× 108 L_{⊙} and LFIR = (1.2-2.0) × 1011 L_{⊙}, which are at least one order of magnitude smaller than those of optically-luminous quasars at z ≳ 6. We estimate the star formation rates (SFRs) of our targets as ≃ 23-40 M_{⊙} yr-1. Their line and continuum-emitting regions are marginally resolved, and found to be comparable in size to those of optically-luminous quasars, indicating that their SFR or likely gas mass surface densities (key controlling parameter of mass accretion) are accordingly different. The L_[C II}]}/L_FIR ratios of the hosts, ≃ (2.2-8.7) × 10-3, are fully consistent with local star-forming galaxies. Using the [C II] dynamics, we derived their dynamical masses within a radius of 1.5-2.5 kpc as ≃ (1.4-8.2) × 1010 M_{⊙}. By interpreting these masses as stellar ones, we suggest that these faint quasar hosts are on or even below the star-forming main sequence at z ˜ 6, i.e., they appear to be transforming into quiescent galaxies. This is in contrast to the optically-luminous quasars at those redshifts, which show starburst-like properties. Finally, we find that the ratios of black hole mass to host galaxy dynamical mass of most of the low-luminosity quasars, including the HSC ones, are consistent with the local value. The mass ratios of the HSC quasars can be reproduced by a semi-analytical model that assumes merger-induced black hole host galaxy evolution.

High-excitation OH and H2O Lines in Markarian 231: The Molecular Signatures of Compact Far-infrared Continuum Sources

NASA Astrophysics Data System (ADS)

González-Alfonso, Eduardo; Smith, Howard A.; Ashby, Matthew L. N.; Fischer, Jacqueline; Spinoglio, Luigi; Grundy, Timothy W.

2008-03-01

The ISO LWS far-infrared spectrum of the ultraluminous galaxy Mrk 231 shows OH and H2O lines in absorption from energy levels up to 300 K above the ground state, and emission in the [O I] 63 μm and [C II] 158 μm lines. Our analysis shows that OH and H2O are radiatively pumped by the far-infrared continuum emission of the galaxy. The absorptions in the high-excitation lines require high far-infrared radiation densities, allowing us to constrain the properties of the underlying continuum source. The bulk of the far-infrared continuum arises from a warm (Tdust = 70-100 K), optically thick (τ100μ m = 1-2) medium of effective diameter 200-400 pc. In our best-fit model of total luminosity LIR, the observed OH and H2O high-lying lines arise from a luminous (L/LIR ~ 0.56) region with radius ~100 pc. The high surface brightness of this component suggests that its infrared emission is dominated by the AGN. The derived column densities N(OH) gtrsim 1017 cm-2 and N(H2O) gtrsim 6 × 1016 cm-2 may indicate X-ray dominated region (XDR) chemistry, although significant starburst chemistry cannot be ruled out. The lower-lying OH, [C II] 158 μm, and [O I] 63 μm lines arise from a more extended (~350 pc) starburst region. We show that the [C II] deficit in Mrk 231 is compatible with a high average abundance of C+ because of an extreme overall luminosity to gas mass ratio. Therefore, a [C II] deficit may indicate a significant contribution to the luminosity by an AGN, and/or by extremely efficient star formation. Based on observations with the Infrared Space Observatory, an ESA project with instruments funded by ESA Member States (especially the principal investigator countries: France, Germany, Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

Star formation in AGNs at the hundred parsec scale using MIR high-resolution images

NASA Astrophysics Data System (ADS)

Ruschel-Dutra, Daniel; Rodríguez Espinosa, José Miguel; González Martín, Omaira; Pastoriza, Miriani; Riffel, Rogério

2017-04-01

It has been well established in the past decades that the central black hole masses of galaxies correlate with dynamical properties of their harbouring bulges. This notion begs the question of whether there are causal connections between the active galactic nucleus (AGN) and its immediate vicinity in the host galaxy. In this paper, we analyse the presence of circumnuclear star formation in a sample of 15 AGN using mid-infrared observations. The data consist of a set of 11.3 μm polycyclic aromatic hydrocarbon emission and reference continuum images, taken with ground-based telescopes, with sub-arcsecond resolution. By comparing our star formation estimates with AGN accretion rates, derived from X-ray luminosities, we investigate the validity of theoretical predictions for the AGN-starburst connection. Our main results are: (I) circumnuclear star formation is found, at distances as low as tens of parsecs from the nucleus, in nearly half of our sample (7/15); (II) star formation luminosities are correlated with the bolometric luminosity of the AGN (LAGN) only for objects with LAGN ≥ 1042 erg s-1; (III) low-luminosity AGNs (LAGN < 1042 erg s-1) seem to have starburst luminosities far greater than their bolometric luminosities.

Narrow vs. Broad line Seyfert 1 galaxies: X-ray, optical and mid-infrared AGN characteristics

NASA Astrophysics Data System (ADS)

Lakićević, Maša; Popović, Luka Č.; Kovačević-Dojčinović, Jelena

2018-05-01

We investigated narrow line Seyfert 1 galaxies (NLS1s) at optical, mid-infrared (MIR) and X-ray wavelengths, comparing them to the broad line active galactic nuclei (BLAGNs). We found that black hole mass, coronal line luminosities, X-ray hardness ratio and X-ray, optical and MIR luminosities are higher for the BLAGNs than for NLS1s, while policyclic aromatic hydrocarbon (PAH) contribution and the accretion rates are higher for the NLS1s. Furthermore, we found some trends among spectral parameters that NLS1s have and BLAGNs do not have. The evolution of FWHM(Hβ) with the luminosities of MIR and coronal lines, continuum luminosities, PAH contribution, Hβ broad line luminosity, FWHM[O III] and EW(HβNLR), are important trends found for NLS1s. That may contribute to the insight that NLS1s are developing AGNs, growing their black holes, while their luminosities and FWHM(Hβ) consequently grow, and that BLAGNs are mature, larger objects of slower and/or different evolution. Black hole mass is related to PAH contribution only for NLS1s, which may suggest that PAHs are more efficiently destroyed in NLS1s.

A comparison of the emission line properties between quasars and type 1 Seyfert galaxies

NASA Technical Reports Server (NTRS)

Wu, C. C.; Boggess, A.; Gull, T. R.

1982-01-01

For quasars and Seyfert galaxies, the equivalent width of C IV lambda 1550 increases as the continuum luminosity of an object decreases. A reasonable interpretation is that the covering factor increases as luminosity decreases. This is consistent with the fact that the L alpha and C IV equivalent widths for Seyferts are a factor of 2 larger than those for high redshift quasars. The C IV/C III ratio, which is a sensitive indicator of the ionization parameter, is about 5 for many Seyferts while it is about 2 for high redshift quasars.

GeV Observations of star-forming galaxies with the Fermi large area telescope

DOE PAGES

Ackermann, M.; Ajello, M.; Allafort, A.; ...

2012-08-07

Some recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. Here,more » we find further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and low-redshift starburst galaxies (conservative P-values ≲ 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log (L 0.1-100 GeV/L 1.4 GHz) = 1.7 ± 0.1(statistical) ± 0.2(dispersion) and log (L 0.1-100 GeV/L 8-1000 μm) = –4.3 ± 0.1(statistical) ± 0.2(dispersion) for a galaxy with a star formation rate of 1 M ⊙yr –1, assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 × 10 –6 ph cm –2 s –1 sr –1 (4%-23% of the intensity of the isotropic diffuse component measured with the LAT). Furthermore, we anticipate that ~10 galaxies could be detected by their cosmic-ray-induced gamma-ray emission during a 10 year Fermi mission.« less

GeV Observations of star-forming galaxies with the Fermi large area telescope

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

Ackermann, M.; Ajello, M.; Allafort, A.

Some recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. Here,more » we find further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and low-redshift starburst galaxies (conservative P-values ≲ 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log (L 0.1-100 GeV/L 1.4 GHz) = 1.7 ± 0.1(statistical) ± 0.2(dispersion) and log (L 0.1-100 GeV/L 8-1000 μm) = –4.3 ± 0.1(statistical) ± 0.2(dispersion) for a galaxy with a star formation rate of 1 M ⊙yr –1, assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 × 10 –6 ph cm –2 s –1 sr –1 (4%-23% of the intensity of the isotropic diffuse component measured with the LAT). Furthermore, we anticipate that ~10 galaxies could be detected by their cosmic-ray-induced gamma-ray emission during a 10 year Fermi mission.« less

GeV Observations of star-forming glaxies with the FERMI Large Area Telescope

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

Ackermann, M.; Ajello, M.; Allafort, A.

Recent detections of the starburst galaxies M82 and NGC 253 by gamma-ray telescopes suggest that galaxies rapidly forming massive stars are more luminous at gamma-ray energies compared to their quiescent relatives. Building upon those results, we examine a sample of 69 dwarf, spiral, and luminous and ultraluminous infrared galaxies at photon energies 0.1-100 GeV using 3 years of data collected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Measured fluxes from significantly detected sources and flux upper limits for the remaining galaxies are used to explore the physics of cosmic rays in galaxies. We findmore » further evidence for quasi-linear scaling relations between gamma-ray luminosity and both radio continuum luminosity and total infrared luminosity which apply both to quiescent galaxies of the Local Group and low-redshift starburst galaxies (conservative P-values lesssim 0.05 accounting for statistical and systematic uncertainties). The normalizations of these scaling relations correspond to luminosity ratios of log (L 0.1-100 GeV/L 1.4 GHz) = 1.7 ± 0.1(statistical) ± 0.2(dispersion) and log (L 0.1-100 GeV/L 8-1000 μm) = –4.3 ± 0.1(statistical) ± 0.2(dispersion) for a galaxy with a star formation rate of 1 M ⊙ yr–1, assuming a Chabrier initial mass function. Using the relationship between infrared luminosity and gamma-ray luminosity, the collective intensity of unresolved star-forming galaxies at redshifts 0 < z < 2.5 above 0.1 GeV is estimated to be 0.4-2.4 × 10–6 ph cm–2 s–1 sr–1 (4%-23% of the intensity of the isotropic diffuse component measured with the LAT). We anticipate that ~10 galaxies could be detected by their cosmic-ray-induced gamma-ray emission during a 10 year Fermi mission.« less

The active quiescence of HR Del (Nova Del 1967). The ex-nova HR Del

NASA Astrophysics Data System (ADS)

Selvelli, P.; Friedjung, M.

2003-04-01

This new UV study of the ex-nova HR Del is based on all of the data obtained with the International Ultraviolet Explorer (IUE) satellite, and includes the important series of spectra taken in 1988 and 1992 that have not been analyzed so far. This has allowed us to make a detailed study of both the long-timescale and the short-timescale UV variations, after the return of the nova, around 1981-1982, to the pre-outburst optical magnitude. After the correction for the reddening (EB-V=0.16), adopting a distance d =850 pc we have derived a mean UV luminosity close to LUV ~ 56 Lsun, the highest value among classical novae in ``quiescence". Also the ``average" optical absolute magnitude (Mv=+2.30) is indicative of a bright object. The UV continuum luminosity, the HeII 1640 Å emission line luminosity, and the optical absolute magnitude all give a mass accretion rate dot {M} very close to 1.4x 10-7 Msun yr-1, if one assumes that the luminosity of the old nova is due to a non-irradiated accretion disk. The UV continuum has declined by a factor less than 1.2 over the 13 years of the IUE observations, while the UV emission lines have faded by larger factors. The continuum distribution is well fitted with either a black body of 33 900 K, or a power-law Flambda ~ lambda -2.20. A comparison with the grid of models of Wade & Hubeny (\\cite{Wade}) indicates a low M1 value and a relatively high dot {M} but the best fittings to the continuum and the line spectrum come from different models. We show that the ``quiescent" optical magnitude at mv ~ 12 comes from the hot component and not from the companion star. Since most IUE observations correspond to the ``quiescent" magnitude at mv ~ 12, the same as in the pre-eruption stage, we infer that the pre-nova, for at least 70 years prior to eruption, was also very bright at near the same LUV, Mv, dot {M}, and T values as derived in the present study for the ex-nova. The wind components in the P Cyg profiles of the CIV 1550 Å and NV 1240 Å resonance lines are strong and variable on short timescales, with vedge up to -5000 km s-1, a remarkably high value. The phenomenology of the short-time variations of the wind indicates the presence of an inhomogeneous outflow. We discuss the nature of the strong UV continuum and wind features and the implications of the presence of a ``bright" state a long time before and after outburst on our present knowledge of the pre-nova and post-nova behavior. Based on observations made with the International Ultraviolet Explorer and de-archived from the ESA VILSPA Database. }

An Iwasawa-Taniguchi effect for Compton-thick active galactic nuclei

NASA Astrophysics Data System (ADS)

Boorman, Peter G.; Gandhi, Poshak; Baloković, Mislav; Brightman, Murray; Harrison, Fiona; Ricci, Claudio; Stern, Daniel

2018-07-01

We present the first study of an Iwasawa-Taniguchi/`X-ray Baldwin' effect for Compton-thick active galactic nuclei (AGN). We report a statistically significant anticorrelation between the rest-frame equivalent width (EW) of the narrow core of the neutral Fe Kα fluorescence emission line, ubiquitously observed in the reflection spectra of obscured AGN, and the mid-infrared 12 μ m continuum luminosity (taken as a proxy for the bolometric AGN luminosity). Our sample consists of 72 Compton-thick AGN selected from pointed and deep-field observations covering a redshift range of z ˜ 0.0014-3.7. We employ a Monte Carlo-based fitting method, which returns a Spearman's Rank correlation coefficient of ρ = - 0.28 ± 0.12, significant to 98.7 per cent confidence. The best-fitting found is log(EW_{Fe Kα }) ∝ -0.08± 0.04 log(L_{12 {μ } m}), which is consistent with multiple studies of the X-ray Baldwin effect for unobscured and mildly obscured AGN. This is an unexpected result, as the Fe Kα line is conventionally thought to originate from the same region as the underlying reflection continuum, which together constitute the reflection spectrum. We discuss the implications this could have if confirmed on larger samples, including a systematic underestimation of the line-of-sight X-ray obscuring column density and hence the intrinsic luminosities and growth rates for the most luminous AGN.

Planetary nebulae populations as tracers of the stellar kinematics and light in the outer halos of galaxies and the intracluster regions in the nearby clusters

NASA Astrophysics Data System (ADS)

Arnaboldi, Magda

2015-08-01

Planetary nebulae have been used sucessfully to trace the kinematics of stars and the spatial distribution of the parent stellar populations in regions where the continuum of the integrated light is only 1% of the night sky. The observed wavelength of the PN strong emission in the [OIII] line at 5007 A measures the line-of-sight velocity of that single star and can be used to derive the two-dimensional velocity fields in these extreme outer regions of galaxies and their angular momentum content out to 10 effective radii. The specific frequency or the PN luminosity number and the morphology of the PN luminosity function are probes of the properties of the parent stellar population, like the star formation history and metallicity. I will present the latest results from the survey of PN population in external galaxies and in the Virgo cluster, and the implications on the coexistence of galaxy halos and intracluster light, and the constraints of their stellar motions and physical parameters.

Combined Ultraviolet and Optical Spectra of 48 Low-Redshift QSOs and the Relation of the Continuum and Emission-Line Properties

NASA Astrophysics Data System (ADS)

Corbin, Michael R.; Boroson, Todd A.

1996-11-01

We present combined ultraviolet and optical spectra of 48 QSOs and Seyfert 1 galaxies in the redshift range 0.034-0.774. The UV spectra were obtained non-simultaneously with the optical and are derived from archival Hubble Space Telescope (HST) Faint Object Spectrograph and International Ultraviolet Explorer (IUE) observations. The sample consists of 22 radio- quiet objects, 12 flat radio spectrum radio-loud objects, and 14 steep radio spectrum objects, and it covers approximately 2.5 decades in ultraviolet continuum luminosity. The sample objects are among the most luminous known in this redshift range and include 3C 273 and Fairall 9, as well as many objects discovered in the Bright Quasar Survey. We measure and compare an array of emission-line and continuum parameters, including 2 keV X-ray luminosities derived from the Einstein database. We examine individual correlations and also apply a principal components analysis (PCA) in an effort to determine the underlying sources of variance among these observables. Our main results are as follows. 1. The C IV λ1549 profile asymmetry is correlated with the UV continuum luminosity measured at the position of that line, such that increasing continuum luminosity produces increasing redward asymmetry. This is the same correlation found between Hβ asymmetry and 2 keV luminosity in a larger sample of objects and appears to be followed by both radio-loud and radio-quiet sources. The C IV profile asymmetry is also correlated with the FWZI of the Lyα profile, with more redward asymmetric profiles associated with wider profile bases. The PCA reveals that the correlated increase in luminosity, C IV redward asymmetry, and profile base width accounts for over half the statistical variance in the sample. 2. There is a statistically significant difference between the FWZI distributions of the Lyα and Hβ lines, such that the former is wider on average by ~10^4^ km s^-1^. The FWHM values of the broad Hβ line are weakly correlated with those of C IV λ1549 and Lyα, and in contrast to the FWZI values the Hβ profiles are wider. Measures of the asymmetry of the Hβ and C IV profiles also show a weak correlation. The wavelength centroids at 3/4 maximum of the Lyα and C IV lines also show average blueshifts ~50-200 km s^-1^ from [O III] λ5007, versus an average redshift of 75 km s^-1^ for broad Hβ. 3. There is no clear evidence of narrow components to the stronger UV lines, even among objects in which the optical narrow lines including [O III] λλ4959, 5007 are unusually strong. We measure the average fractional contributions of such components to the Lyα and C III] λ1909 lines to be ~4%-5%, consistent with the findings from smaller samples. However, a sizable fraction (50%) of radio-loud objects display a narrow component of He II λ1640, the same as in the QSO population at intermediate redshifts, and such a component is likely to contribute to the other UV lines. We interpret the first result as the effect of a black hole mass/luminosity relation in which the profile widths and redward asymmetries are produced respectively by the virialized motions and gravitational redshift associated with 10^9^-10^10^ M_sun_ holes. This does not explain the cases of blueward profile asymmetries and blueshifted profile peaks, which require an effect acting oppositely to gravitational redshift. The peak redshift differences and relative weakness of the correlations between the UV profile widths and asymmetries and those of Hβ suggests a stratified ionization structure of the broad-line region (BLR), consistent with the variability studies of Seyfert 1 galaxies. Continuum variability and the dynamical evolution of the BLR gas may also influence these results. The difference between the Lyα and Hβ FWZI values provides additional evidence of an optically thin very broad line region (VBLR) lying interior to an intermediate line region (ILR) producing the profile cores. The smaller average FWHM values of the UV lines compared to Hβ indicate that they have a higher relative contribution of ILR emission, versus a more dominant VBLR component in the Balmer lines. The narrow He II λ1640 feature of radio-loud objects is likely associated with the inner regions of extended (100 kpc) ionized halos that are not present around radio-quiet objects, and which appear to be best explained as cooling flows around the QSO host galaxies.

Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar

NASA Technical Reports Server (NTRS)

Greene, Thomas P.; Lada, Charles J.; DeVincenzi, Donald L. (Technical Monitor)

2002-01-01

We present high-resolution (R is approximately equal to 18,000), high signal-to-noise 2 micron spectra of two luminous, X-ray flaring Class I protostars in the rho Ophiuchi cloud acquired with the NIRSPEC (near infrared spectrograph) of the Keck II telescope. We present the first spectrum of a highly veiled, strongly accreting protostar which shows photospheric absorption features and demonstrates the stellar nature of its central core. We find the spectrum of the luminous (L (sub bol) = 10 solar luminosity) protostellar source, YLW 15, to be stellar-like with numerous atomic and molecular absorption features, indicative of a K5 IV/V spectral type and a continuum veiling r(sub k) = 3.0. Its derived stellar luminosity (3 stellar luminosity) and stellar radius (3.1 solar radius) are consistent with those of a 0.5 solar mass pre-main-sequence star. However, 70% of its bolometric luminosity is due to mass accretion, whose rate we estimate to be 1.7 x 10(exp -6) solar masses yr(exp -1). We determine that excess infrared emission produced by the circumstellar accretion disk, the inner infalling envelope, and accretion shocks at the surface of the stellar core of YLW 15 all contribute significantly to its near-IR (infrared) continuum veiling. Its rotational velocity v sin i = 50 km s(exp -1) is comparable to those of flat-spectrum protostars but considerably higher than those of classical T Tauri stars in the rho Oph cloud. The protostar may be magnetically coupled to its circumstellar disk at a radius of 2 - 3 R(sub *). It is also plausible that this protostar can shed over half its angular momentum and evolve into a more slowly rotating classical T Tauri star by remaining coupled to its circumstellar disk (at increasing radius) as its accretion rate drops by an order of magnitude during the rapid transition between the Class I and Class II phases of evolution. The spectrum of WL 6 does not show any photospheric absorption features, and we estimate that its continuum veiling is r(sub k) is greater than or equal to 4.6. Its low luminosity (2 solar masses) and high veiling dictate that its central protostar is very low mass, M is approx. 0.1 solar masses. We also evaluate multi-epoch X ray data along with these spectra and conclude that the X ray variabilities of these sources are not directly related to their protostellar rotation velocities.

Supernova spectra below strong circumstellar interaction

NASA Astrophysics Data System (ADS)

Leloudas, G.; Hsiao, E. Y.; Johansson, J.; Maeda, K.; Moriya, T. J.; Nordin, J.; Petrushevska, T.; Silverman, J. M.; Sollerman, J.; Stritzinger, M. D.; Taddia, F.; Xu, D.

2015-02-01

We construct spectra of supernovae (SNe) interacting strongly with a circumstellar medium (CSM) by adding SN templates, a black-body continuum, and an emission-line spectrum. In a Monte Carlo simulation we vary a large number of parameters, such as the SN type, brightness and phase, the strength of the CSM interaction, the extinction, and the signal to noise ratio (S/N) of the observed spectrum. We generate more than 800 spectra, distribute them to ten different human classifiers, and study how the different simulation parameters affect the appearance of the spectra and their classification. The SNe IIn showing some structure over the continuum were characterized as "SNe IInS" to allow for a better quantification. We demonstrate that the flux ratio of the underlying SN to the continuum fV is the single most important parameter determining whether a spectrum can be classified correctly. Other parameters, such as extinction, S/N, and the width and strength of the emission lines, do not play a significant role. Thermonuclear SNe get progressively classified as Ia-CSM, IInS, and IIn as fV decreases. The transition between Ia-CSM and IInS occurs at fV ~ 0.2-0.3. It is therefore possible to determine that SNe Ia-CSM are found at the (un-extincted) magnitude range -19.5 >M> -21.6, in very good agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = -20.1. The literature sample of SNe Ia-CSM shows an association with 91T-like SNe Ia. Our experiment does not support that this association can be attributed to a luminosity bias (91T-like being brighter than normal events). We therefore conclude that this association has real physical origins and we propose that 91T-like explosions result from single degenerate progenitors that are responsible for the CSM. Despite the spectroscopic similarities between SNe Ibc and SNe Ia, the number of misclassifications between these types was very small in our simulation and mostly at low S/N. Combined with the SN luminosity function needed to reproduce the observed SN Ia-CSM luminosities, it is unlikely that SNe Ibc constitute an important contaminant within this sample. We show how Type II spectra transition to IIn and how the Hα profiles vary with fV. SNe IIn fainter than M = -17.2 are unable to mask SNe IIP brighter than M = -15. A more advanced simulation, including radiative transfer, shows that our simplified model is a good first order approximation. The spectra obtained are in good agreement with real data.

Relations Between FUV Excess and Coronal Soft X-Ray Emission Among Dwarf Stars

NASA Astrophysics Data System (ADS)

Smith, Graeme H.; Hargrave, Mason; Eckholm, Elliot

2017-11-01

The far-ultraviolet magnitudes of late-F, G and early-K dwarfs with (B - V) ⩾ 0.50 as measured by the GALEX satellite are shown to correlate with soft X-ray luminosity. This result indicates that line and continuum emission from stellar active regions make significant contributions to the flux in the GALEX FUV band for late-F, G and K dwarfs. By contrast, detection of a correlation between FUV brightness and soft X-ray luminosity among early-F dwarfs requires subtraction of the photospheric component from the FUV flux. The range in (B - V) among F and G dwarfs over which a correlation between uncorrected FUV magnitude and X-ray luminosity is detected coincides with the range in colour over which coronal and chromospheric emission correlates with stellar rotation.

Fermi-Compton scattering due to magnetopause surface fluctuations in Jupiter's magnetospheric cavity

NASA Technical Reports Server (NTRS)

Barbosa, D. D.

1981-01-01

The effects of boundary surface fluctuations on a spectrum of electromagnetic radiation trapped in a high Q (quality) cavity are considered. Undulating walls introduce small frequency shifts at reflection to the radiation, and it is argued that the process is entirely analogous to both Fermi (particle) acceleration and inverse Compton scattering. A Fokker-Planck formalism is pursued; it yields a diffusion equation in frequency for which the Green's function and steady-state solutions are found. Applying this analysis to the Jovian continuum radiation discovered by Voyager spacecraft, it is suggested that characteristic diffusion times are greater than 1 year, and that in order to account for the steep frequency spectra observed, an unidentified loss mechanism must operate in the cavity with a decay time constant approximately equal to the characteristic diffusion time divided by 28. A radiator-reactor model of the cavity is investigated to provide an estimate for the intrinsic luminosity of the low frequency (approximately 100 Hz) continuum source whose power is approximately 7 x 10 to the 6th W.

Emission Line Properties of Seyfert Galaxies in the 12 μm Sample

NASA Astrophysics Data System (ADS)

Malkan, Matthew A.; Jensen, Lisbeth D.; Rodriguez, David R.; Spinoglio, Luigi; Rush, Brian

2017-09-01

We present optical and ultraviolet spectroscopic measurements of the emission lines of 81 Seyfert 1 and 104 Seyfert 2 galaxies that comprise nearly all of the IRAS 12 μm AGN sample. We have analyzed the emission-line luminosity functions, reddening, and other diagnostics. For example, the narrow-line regions (NLR) of Seyfert 1 and 2 galaxies do not significantly differ from each other in most of these diagnostics. Combining the Hα/Hβ ratio with a new reddening indicator—the [S II]6720/[O II]3727 ratio—we find the average E(B-V) is 0.49 ± 0.35 for type 1 and 0.52 ± 0.26 for type 2 Seyferts. The NLR of Sy 1s has an ionization level insignificantly higher than that of Sy 2s. For the broad-line region (BLR), we find that the C IV equivalent width correlates more strongly with [O III]/Hβ than with UV luminosity. Our bright sample of local active galaxies includes 22 Seyfert nuclei with extremely weak broad wings in Hα, known as Seyfert 1.9s and 1.8s, depending on whether or not broad Hβ wings are detected. Aside from these weak broad lines, our low-luminosity Seyferts are more similar to the Sy 2s than to Sy 1s. In a BPT diagram, we find that Sy 1.8s and 1.9s overlap the region occupied by Sy 2s. We compare our results on optical emission lines with those obtained by previous investigators, using AGN subsamples from the Sloan Digital Sky Survey. The luminosity functions of forbidden emission lines [O II]λ3727 Å, [O III]λ5007 Å, and [S II]λ6720 Å in Sy 1s and Sy 2s are indistinguishable. They all show strong downward curvature. Unlike the LFs of Seyfert galaxies measured by the Sloan Digital Sky Survey, ours are nearly flat at low luminosities. The larger number of faint Sloan “AGN” is attributable to their inclusion of weakly emitting LINERs and H II+AGN “composite” nuclei, which do not meet our spectral classification criteria for Seyferts. In an Appendix, we have investigated which emission line luminosities can provide the most reliable measures of the total non-stellar luminosity, estimated from our extensive multi-wavelength database. The hard X-ray or near-ultraviolet continuum luminosity can be crudely predicted from either the [O III]λ5007 Å luminosity or the combinations of [O III]+Hβ or [N II]+Hα lines, with a scatter of +/- 4 times for Sy 1s and +/- 10 times for Sy 2s. Although these uncertainties are large, the latter two hybrid (NLR+BLR) indicators have the advantage of predicting the same HX luminosity independent of Seyfert type.

Mass Accretion Rate of Very Low Luminosity Objects

NASA Astrophysics Data System (ADS)

Sung, Ren-Shiang; Lai, Shih-Ping; Hsieh, Tien-Hao

2013-08-01

We propose to measure the mass accretion rate of six Very Low Luminosity Objects (VeLLOs) using Near-infrared Integral Spectrometer (NIFS). The extremely low luminosity of VeLLOs, L_int ≤ 0.1 L_⊙, was previously thought not existing in the nature because the typical accretion rate gives much larger accretion luminosity even for the lowest mass star (``Luminosity Problem''). The commonly accepted solution is that the accretion rate is not constant but episodic. Thus, VeLLOs could be interpreted as protostars being in the quiescent phase of accretion activities. However, there is no observational data directly measuring the mass accretion rate of VeLLOs. The main goal of this proposal is to examine such theory and directly measure the mass accretion rate of VeLLOs for the first time. We propose to measure the blue continuum excess (veiling) of the stellar spectrum, which is the most reliable method for measuring the accretion rate. The measurements have to be made in infrared due to the very high extinction for highly embedded protostars. Our proposal provide a first opportunity to explain the long time ``Luminosity Problem'' through the observational aspects, and Gemini is the only instrument that can provide accurate and high sensitivity infrared spectroscopy measurements within reasonably short time scale.

ALMA Reveals Metals yet No Dust within Multiple Components in CR7

NASA Astrophysics Data System (ADS)

Matthee, J.; Sobral, D.; Boone, F.; Röttgering, H.; Schaerer, D.; Girard, M.; Pallottini, A.; Vallini, L.; Ferrara, A.; Darvish, B.; Mobasher, B.

2017-12-01

We present spectroscopic follow-up observations of CR7 with ALMA, targeted at constraining the infrared (IR) continuum and [C II]{}158μ {{m}} line-emission at high spatial resolution matched to the HST/WFC3 imaging. CR7 is a luminous Lyα emitting galaxy at z = 6.6 that consists of three separated UV-continuum components. Our observations reveal several well-separated components of [C II] emission. The two most luminous components in [C II] coincide with the brightest UV components (A and B), blueshifted by ≈ 150 km s‑1 with respect to the peak of Lyα emission. Other [C II] components are observed close to UV clumps B and C and are blueshifted by ≈ 300 and ≈80 km s‑1 with respect to the systemic redshift. We do not detect FIR continuum emission due to dust with a 3σ limiting luminosity {L}{IR}({T}d=35 {{K}})< 3.1× {10}10 {L}ȯ . This allows us to mitigate uncertainties in the dust-corrected SFR and derive SFRs for the three UV clumps A, B, and C of 28, 5, and 7 {M}ȯ yr‑1. All clumps have [C II] luminosities consistent within the scatter observed in the local relation between SFR and {L}[{{C}{{II}}]}, implying that strong Lyα emission does not necessarily anti-correlate with [C II] luminosity. Combining our measurements with the literature, we show that galaxies with blue UV slopes have weaker [C II] emission at fixed SFR, potentially due to their lower metallicities and/or higher photoionization. Comparison with hydrodynamical simulations suggests that CR7's clumps have metallicities of 0.1< {{Z}}/{{{Z}}}ȯ < 0.2. The observed ISM structure of CR7 indicates that we are likely witnessing the build up of a central galaxy in the early universe through complex accretion of satellites.

A study of (OI) 63.2 and 145.5 micron emission from M17 and SGR A from the Lear jet

NASA Technical Reports Server (NTRS)

Melnick, G. G.

1986-01-01

The Lear Jet Observatory was used to observe the 157.7 micron (C II) line from the galactic H II regions W3 and W51. These measurements established a lower limit in the 157.7 micron line for solar luminosity of 360 from W3, assuming adistance of 2 kpc, and a solar luminosity of 4100 from W51, assuming a distance of 7 kpc. The data indicated that the CII/far infrared continuum ratio for both W3 and W51 were within the range found for other galactic H II regions.

VizieR Online Data Catalog: BAL QSOs from SDSS DR3 (Trump+, 2006)

NASA Astrophysics Data System (ADS)

Trump, J. R.; Hall, P. B.; Reichard, T. A.; Richards, G. T.; Schneider, D. P.; vanden Berk, D. E.; Knapp, G. R.; Anderson, S. F.; Fan, X.; Brinkman, J.; Kleinman, S. J.; Nitta, A.

2007-11-01

We present a total of 4784 unique broad absorption line quasars from the Sloan Digital Sky Survey Third Data Release (Cat. ). An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000km/s in the CIV and MgII absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift, with the power-law spectral index and amount of dust reddening as additional free parameters. We characterize our sample through the traditional balnicity index and a revised absorption index, as well as through parameters such as the width, outflow velocity, fractional depth, and number of troughs. (1 data file).

The role of environment in the observed Fundamental Plane of radio Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Shabala, Stanislav S.

2018-05-01

The optical Fundamental Plane of black hole activity relates radio continuum luminosity of Active Galactic Nuclei to [O III] luminosity and black hole mass. We examine the environments of low redshift (z < 0.2) radio-selected AGN, quantified through galaxy clustering, and find that halo mass provides similar mass scalings to black hole mass in the Fundamental Plane relations. AGN properties are strongly environment-dependent: massive haloes are more likely to host radiatively inefficient (low-excitation) radio AGN, as well as a higher fraction of radio luminous, extended sources. These AGN populations have different radio - optical luminosity scaling relations, and the observed mass scalings in the parent AGN sample are built up by combining populations preferentially residing in different environments. Accounting for environment-driven selection effects, the optical Fundamental Plane of supermassive black holes is likely to be mass-independent, as predicted by models.

ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Infrared Excess of UV-Selected z = 2-10 Galaxies as a Function of UV-Continuum Slope and Stellar Mass

NASA Astrophysics Data System (ADS)

Bouwens, Rychard J.; Aravena, Manuel; Decarli, Roberto; Walter, Fabian; da Cunha, Elisabete; Labbé, Ivo; Bauer, Franz E.; Bertoldi, Frank; Carilli, Chris; Chapman, Scott; Daddi, Emanuele; Hodge, Jacqueline; Ivison, Rob J.; Karim, Alex; Le Fevre, Olivier; Magnelli, Benjamin; Ota, Kazuaki; Riechers, Dominik; Smail, Ian R.; van der Werf, Paul; Weiss, Axel; Cox, Pierre; Elbaz, David; Gonzalez-Lopez, Jorge; Infante, Leopoldo; Oesch, Pascal; Wagg, Jeff; Wilkins, Steve

2016-12-01

We make use of deep 1.2 mm continuum observations (12.7 μJy beam-1 rms) of a 1 arcmin2 region in the Hubble Ultra Deep Field to probe dust-enshrouded star formation from 330 Lyman-break galaxies spanning the redshift range z = 2-10 (to ˜2-3 M ⊙ yr-1 at 1σ over the entire range). Given the depth and area of ASPECS, we would expect to tentatively detect 35 galaxies, extrapolating the Meurer z ˜ 0 IRX-β relation to z ≥ 2 (assuming dust temperature T d ˜ 35 K). However, only six tentative detections are found at z ≳ 2 in ASPECS, with just three at >3σ. Subdividing our z = 2-10 galaxy samples according to stellar mass, UV luminosity, and UV-continuum slope and stacking the results, we find a significant detection only in the most massive (>109.75 M ⊙) subsample, with an infrared excess (IRX = L IR/L UV) consistent with previous z ˜ 2 results. However, the infrared excess we measure from our large selection of sub-L ∗ (<109.75 M ⊙) galaxies is {0.11}-0.42+0.32 ± 0.34 (bootstrap and formal uncertainties) and {0.14}-0.14+0.15 ± 0.18 at z = 2-3 and z = 4-10, respectively, lying below even an IRX-β relation for the Small Magellanic Cloud (95% confidence). These results demonstrate the relevance of stellar mass for predicting the IR luminosity of z ≳ 2 galaxies. We find that the evolution of the IRX-stellar mass relationship depends on the evolution of the dust temperature. If the dust temperature increases monotonically with redshift (\\propto {(1+z)}0.32) such that T d ˜ 44-50 K at z ≥ 4, current results are suggestive of little evolution in this relationship to z ˜ 6. We use these results to revisit recent estimates of the z ≥ 3 star formation rate density.

First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z ˜ 7

NASA Astrophysics Data System (ADS)

Zheng, Zhen-Ya; Wang, Junxian; Rhoads, James; Infante, Leopoldo; Malhotra, Sangeeta; Hu, Weida; Walker, Alistair R.; Jiang, Linhua; Jiang, Chunyan; Hibon, Pascale; Gonzalez, Alicia; Kong, Xu; Zheng, XianZhong; Galaz, Gaspar; Barrientos, L. Felipe

2017-06-01

We present the first results from the ongoing Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) project, which is the largest narrowband survey for z ˜ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark Energy Camera (DECam) on the NOAO/CTIO 4 m Blanco telescope, LAGER has collected 34 hr NB964 narrowband imaging data in the 3 deg2 COSMOS field. We have identified 23 Lyα Emitter candidates at z = 6.9 in the central 2-deg2 region, where DECam and public COSMOS multi-band images exist. The resulting luminosity function (LF) can be described as a Schechter function modified by a significant excess at the bright end (four galaxies with L Lyα ˜ 1043.4±0.2 erg s-1). The number density at L Lyα ˜ 1043.4±0.2 erg s-1 is little changed from z = 6.6, while at fainter L Lyα it is substantially reduced. Overall, we see a fourfold reduction in Lyα luminosity density from z = 5.7 to z = 6.9. Combined with a more modest evolution of the continuum UV luminosity density, this suggests a factor of ˜3 suppression of Lyα by radiative transfer through the z ˜ 7 intergalactic medium (IGM). It indicates an IGM neutral fraction of x H I ˜ 0.4-0.6 (assuming Lyα velocity offsets of 100-200 km s-1). The changing shape of the Lyα LF between z ≲ 6.6 and z = 6.9 supports the hypothesis of ionized bubbles in a patchy reionization at z ˜ 7.

Identifying the subtle signatures of feedback from distant AGN using ALMA observations and the EAGLE hydrodynamical simulations

NASA Astrophysics Data System (ADS)

Scholtz, J.; Alexander, D. M.; Harrison, C. M.; Rosario, D. J.; McAlpine, S.; Mullaney, J. R.; Stanley, F.; Simpson, J.; Theuns, T.; Bower, R. G.; Hickox, R. C.; Santini, P.; Swinbank, A. M.

2018-03-01

We present sensitive 870 μm continuum measurements from our ALMA programmes of 114 X-ray selected active galactic nuclei (AGN) in the Chandra Deep Field-South and Cosmic Evolution Survey fields. We use these observations in combination with data from Spitzer and Herschel to construct a sample of 86 X-ray selected AGN, 63 with ALMA constraints at z = 1.5-3.2 with stellar mass >2 × 1010 M⊙. We constructed broad-band spectral energy distributions in the infrared band (8-1000 μm) and constrain star-formation rates (SFRs) uncontaminated by the AGN. Using a hierarchical Bayesian method that takes into account the information from upper limits, we fit SFR and specific SFR (sSFR) distributions. We explore these distributions as a function of both X-ray luminosity and stellar mass. We compare our measurements to two versions of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulations: the reference model with AGN feedback and the model without AGN. We find good agreement between the observations and that predicted by the EAGLE reference model for the modes and widths of the sSFR distributions as a function of both X-ray luminosity and stellar mass; however, we found that the EAGLE model without AGN feedback predicts a significantly narrower width when compared to the data. Overall, from the combination of the observations with the model predictions, we conclude that (1) even with AGN feedback, we expect no strong relationship between the sSFR distribution parameters and instantaneous AGN luminosity and (2) a signature of AGN feedback is a broad distribution of sSFRs for all galaxies (not just those hosting an AGN) with stellar masses above ≈1010 M⊙.

The composite nature of Dust-Obscured Galaxies (DOGs) at z ˜ 2-3 in the COSMOS field - I. A far-infrared view

NASA Astrophysics Data System (ADS)

Riguccini, L.; Le Floc'h, E.; Mullaney, J. R.; Menéndez-Delmestre, K.; Aussel, H.; Berta, S.; Calanog, J.; Capak, P.; Cooray, A.; Ilbert, O.; Kartaltepe, J.; Koekemoer, A.; Lutz, D.; Magnelli, B.; McCracken, H.; Oliver, S.; Roseboom, I.; Salvato, M.; Sanders, D.; Scoville, N.; Taniguchi, Y.; Treister, E.

2015-09-01

Dust-Obscured Galaxies (DOGs) are bright 24 μm-selected sources with extreme obscuration at optical wavelengths. They are typically characterized by a rising power-law continuum of hot dust (TD ˜ 200-1000 K) in the near-IR indicating that their mid-IR luminosity is dominated by an active galactic nucleus (AGN). DOGs with a fainter 24 μm flux display a stellar bump in the near-IR and their mid-IR luminosity appears to be mainly powered by dusty star formation. Alternatively, it may be that the mid-IR emission arising from AGN activity is dominant but the torus is sufficiently opaque to make the near-IR emission from the AGN negligible with respect to the emission from the host component. In an effort to characterize the astrophysical nature of the processes responsible for the IR emission in DOGs, this paper exploits Herschel data (PACS + SPIRE) on a sample of 95 DOGs within the COSMOS field. We derive a wealth of far-IR properties (e.g. total IR luminosities; mid-to-far-IR colours; dust temperatures and masses) based on spectral energy distribution fitting. Of particular interest are the 24 μm-bright DOGs (F24 μm > 1 mJy). They present bluer far-IR/mid-IR colours than the rest of the sample, unveiling the potential presence of an AGN. The AGN contribution to the total 8-1000 μm flux increases as a function of the rest-frame 8 μm-luminosity irrespective of the redshift. This confirms that faint DOGs (L8 μm < 1012 L⊙) are dominated by star formation while brighter DOGs show a larger contribution from an AGN.

Toward Understanding the Fanaroff-Riley Dichotomy in Radio Source Morphology and Power

NASA Astrophysics Data System (ADS)

Baum, Stefi A.; Zirbel, Esther L.; O'Dea, Christopher P.

1995-09-01

In Paper I we presented the results of a study of the interrelationships between host galaxy magnitude, optical line luminosity, and radio luminosity in a large sample of Fanaroff-Riley classes 1 and 2 (FR 1 and FR 2) radio galaxies. We report several important differences between the FR 1 and FR 2 radio galaxies. At the same host galaxy magnitude or radio luminosity, the FR 2's produce substantially more optical line emission (by roughly an order of magnitude or more) than do FR 1's. Similarly, FR 2 sources produce orders of magnitude more line luminosity than do radio-quiet galaxies of the same optical magnitude, while FR 1 sources and radio-quiet galaxies of the same optical magnitude produce similar line luminosities. Combining these results with previous results from the literature, we conclude that while the emission-line gas in the FR 2's is indeed photoionized by a nuclear UV continuum source from the AGN, the emission-line gas in the FR 1's may be energized predominantly by processes associated with the host galaxy itself. The apparent lack of a strong UV continuum source from the central engine in FR 1 sources can be understood in two different ways. In the first scenario, FR l's are much more efficient at covering jet bulk kinetic energy into radio luminosity than FR 2's, such that an FR 1 has a much lower bolometric AGN luminosity (hence nuclear UV continuum source) than does an FR 2 of the same radio luminosity. We discuss the pros and cons of this model and conclude that the efficiency differences needed between FR 2 and FR 1 radio galaxies are quite large and may lead to difficulties with the interpretation since it would suggest that FR 2 radio source deposit very large amounts of kinetic energy into the ISM Intracluster Medium. However, this interpretation remains viable. Alternatively, it may be that the AGNs in FR 1 sources simply produce far less radiant UV energy than do those in FR 2 sources. That is, FR 1 sources may funnel a higher fraction of the total energy output from the AGNs into jet kinetic energy versus radiant energy than do FR 2 sources. If this interpretation is correct, then this suggests that there is a fundamental difference in the central engine and/or in the immediate "accretion region" around the engine in FR 1 and FR 2 radio galaxies. We note also the absence of FR 1 sources with nuclear broad line regions and suggest that the absence of the BLR is tied to the absence of the "isotropic" nuclear UV continuum source in FR 1 sources. We put forth the possibility that the FR 1/FR 2 dichotomy (i.e., the observed differences in the properties of low- and high-power radio sources) is due to qualitative differences in the structural properties of the central engines in these two types of sources. Following early work by Rees et al. (1982), we suggest the possibility that FR 1 sources are produced when the central engine is fed at a lower accretion rate, leading to the creation of a source in which the ratio of radiant to jet bulk kinetic energy is low, while FR 2 sources are produced when the central engine is fed at a higher accretion rate, causing the central engine to deposit a higher fraction of its energy in radiant energy. We further suggest the possibility that associated differences in the spin properties of the central black hole between FR 1 (lower spin) and FR 2 (higher spin) sources may be responsible for the different collimation properties and Mach numbers of the jets produced by these two types of radio-loud galaxies. This scenario, although currently clearly speculative, is nicely consistent with our current picture of the triggering, feeding, environments, and evolution of powerful radio galaxies. This model allows for evolution of these properties with time for example, the mass accretion rate and BH spin may decline with time causing an FR 2 radio source or quasar to evolve into a FR 1 radio source.

THE LOCAL [C ii] 158 μ m EMISSION LINE LUMINOSITY FUNCTION

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

Hemmati, Shoubaneh; Yan, Lin; Capak, Peter

We present, for the first time, the local [C ii] 158 μ m emission line luminosity function measured using a sample of more than 500 galaxies from the Revised Bright Galaxy Sample. [C ii] luminosities are measured from the Herschel PACS observations of the Luminous Infrared Galaxies (LIRGs) in the Great Observatories All-sky LIRG Survey and estimated for the rest of the sample based on the far-infrared (far-IR) luminosity and color. The sample covers 91.3% of the sky and is complete at S{sub 60μm} > 5.24 Jy. We calculate the completeness as a function of [C ii] line luminosity and distance, basedmore » on the far-IR color and flux densities. The [C ii] luminosity function is constrained in the range ∼10{sup 7–9} L{sub ⊙} from both the 1/ V{sub max} and a maximum likelihood methods. The shape of our derived [C ii] emission line luminosity function agrees well with the IR luminosity function. For the CO(1-0) and [C ii] luminosity functions to agree, we propose a varying ratio of [C ii]/CO(1-0) as a function of CO luminosity, with larger ratios for fainter CO luminosities. Limited [C ii] high-redshift observations as well as estimates based on the IR and UV luminosity functions are suggestive of an evolution in the [C ii] luminosity function similar to the evolution trend of the cosmic star formation rate density. Deep surveys using the Atacama Large Millimeter Array with full capability will be able to confirm this prediction.« less

A New Catalog of H II Regions in M31

NASA Astrophysics Data System (ADS)

Azimlu, M.; Marciniak, R.; Barmby, P.

2011-10-01

We present a new catalog of H II regions in M31. The full disk of the galaxy (~24 kpc from the galaxy center) is covered in a 2.2 deg2 mosaic of 10 fields observed with the Mosaic Camera on the Mayall 4 m telescope as part of the Local Group Galaxies survey. We used HIIphot, a code for automated photometry of H II regions, to identify the regions and measure their fluxes and sizes. A 10σ detection level was used to exclude diffuse gas fluctuations and star residuals after continuum subtraction. That selection limit may result in missing some faint H II regions, but our catalog of 3691 H II regions is still complete to a luminosity of L Hα = 1034 erg s-1. This is five times fainter than the only previous CCD-based study which contained 967 objects in the NE half of M31. We determined the Hα luminosity function (LF) by fitting a power law to luminosities larger than L Hα = 1036.7 and determined a slope of 2.52 ± 0.07. The in-arm and inter-arm LFs peak at different luminosities but they have similar bright-end slopes. The inter-arm regions are less populated (40% of total detected regions) and constitute only 14% of the total luminosity of L Hα = 5.6 × 1040 erg s-1 (after extinction correction and considering 65% contribution from diffused ionized gas). A star formation rate of 0.44 M sun yr-1 was estimated from the Hα total luminosity; this value is consistent with the determination from the Spitzer 8 μm image. We removed all known and potential planetary nebulae, yet we found a double-peaked LF. The inter-arm older population suggests a starburst between 15 and 20 million years ago. This result is in agreement with UV studies of the star formation history in M31 which found a star formation rate decrease in the recent past. We found a fair spatial correlation between the H II regions and stellar clusters in selected star-forming regions. Most of the matched regions lie within the arm regions.

LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS

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

Kryukova, E.; Megeath, S. T.; Allen, T. S.

2012-08-15

We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Usingmore » protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our luminosity functions to those predicted by models and find that our observed luminosity functions are best matched by models that invoke competitive accretion, although we do not find strong agreement between the high-mass SF clouds and any of the models.« less

1.0 Mm Maps and Radial Density Distributions of Southern Hii/molecular Cloud Complexes

NASA Technical Reports Server (NTRS)

Cheung, L. H.; Frogel, J. A.; Gezar, D. Y.; Hauser, M. G.

1980-01-01

Several 1.0 continuum mapping observations were made of seven southern hemisphere h12/molecular cloud complexes with 65 arcsec resolution. The radial density distribution of the clouds with central luminosity sources was determined observationally. Strong similarities in morphology and general physical conditions were found to exist among all of the southern clouds in the sample.

TESTING WIND AS AN EXPLANATION FOR THE SPIN PROBLEM IN THE CONTINUUM-FITTING METHOD

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

You, Bei; Czerny, Bożena; Sobolewska, Małgosia

2016-04-20

The continuum-fitting method is one of the two most advanced methods of determining the black hole spin in accreting X-ray binary systems. There are, however, still some unresolved issues with the underlying disk models. One of these issues manifests as an apparent decrease in spin for increasing source luminosity. Here, we perform a few simple tests to establish whether outflows from the disk close to the inner radius can address this problem. We employ four different parametric models to describe the wind and compare these to the apparent decrease in spin with luminosity measured in the sources LMC X-3 andmore » GRS 1915+105. Wind models in which parameters do not explicitly depend on the accretion rate cannot reproduce the spin measurements. Models with mass accretion rate dependent outflows, however, have spectra that emulate the observed ones. The assumption of a wind thus effectively removes the artifact of spin decrease. This solution is not unique; the same conclusion can be obtained using a truncated inner disk model. To distinguish among the valid models, we will need high-resolution X-ray data and a realistic description of the Comptonization in the wind.« less

THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

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

Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu

2015-01-01

We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg{sup 2} utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z{sub B} ) and (z{sub B} -z{sub R} ) colors, where z{sub B} and z{sub R} are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z{sub R} < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). Wemore » have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M {sub 1450} = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M {sub 1450} = –22.58 and a narrow Lyα emission with HWHM =427 km s{sup –1}, which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6.« less

Lyman-continuum leakage as dominant source of diffuse ionized gas in the Antennae galaxy

NASA Astrophysics Data System (ADS)

Weilbacher, Peter M.; Monreal-Ibero, Ana; Verhamme, Anne; Sandin, Christer; Steinmetz, Matthias; Kollatschny, Wolfram; Krajnović, Davor; Kamann, Sebastian; Roth, Martin M.; Erroz-Ferrer, Santiago; Marino, Raffaella Anna; Maseda, Michael V.; Wendt, Martin; Bacon, Roland; Dreizler, Stefan; Richard, Johan; Wisotzki, Lutz

2018-04-01

The Antennae galaxy (NGC 4038/39) is the closest major interacting galaxy system and is therefore often studied as a merger prototype. We present the first comprehensive integral field spectroscopic dataset of this system, observed with the MUSE instrument at the ESO VLT. We cover the two regions in this system which exhibit recent star formation: the central galaxy interaction and a region near the tip of the southern tidal tail. In these fields, we detect HII regions and diffuse ionized gas to unprecedented depth. About 15% of the ionized gas was undetected by previous observing campaigns. This newly detected faint ionized gas is visible everywhere around the central merger, and shows filamentary structure. We estimate diffuse gas fractions of about 60% in the central field and 10% in the southern region. We are able to show that the southern region contains a significantly different population of HII regions, showing fainter luminosities. By comparing HII region luminosities with the HST catalog of young star clusters in the central field, we estimate that there is enough Lyman-continuum leakage in the merger to explain the amount of diffuse ionized gas that we detect. We compare the Lyman-continuum escape fraction of each HII region against emission line ratios that are sensitive to the ionization parameter. While we find no systematic trend between these properties, the most extreme line ratios seem to be strong indicators of density bounded ionization. Extrapolating the Lyman-continuum escape fractions to the southern region, we conclude that simply from the comparison of the young stellar populations to the ionized gas there is no need to invoke other ionization mechanisms than Lyman-continuum leaking HII regions for the diffuse ionized gas in the Antennae. FITS images and Table of HII regions are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A95 and at http://muse-vlt.eu/science/antennae/

Karl G. Jansky very large array observations of cold dust and molecular gas in starbursting quasar host galaxies at z ∼ 4.5

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

Wagg, J.; Carilli, C. L.; Lentati, L.

2014-03-10

We present Karl G. Jansky Very Large Array (VLA) observations of 44 GHz continuum and CO J = 2-1 line emission in BRI 1202–0725 at z = 4.7 (a starburst galaxy and quasar pair) and BRI 1335–0417 at z = 4.4 (also hosting a quasar). With the full 8 GHz bandwidth capabilities of the upgraded VLA, we study the (rest-frame) 250 GHz thermal dust continuum emission for the first time along with the cold molecular gas traced by the low-J CO line emission. The measured CO J = 2-1 line luminosities of BRI 1202–0725 are L{sub CO}{sup ′}=(8.7±0.8)×10{sup 10} Kmore » km s{sup –1} pc{sup 2} and L{sub CO}{sup ′}=(6.0 ± 0.5)×10{sup 10} K km s{sup –1} pc{sup 2} for the submillimeter galaxy (SMG) and quasar, respectively, which are equal to previous measurements of the CO J = 5-4 line luminosities implying thermalized line emission, and we estimate a combined cold molecular gas mass of ∼9×10{sup 10} M {sub ☉}. In BRI 1335–0417 we measure L{sub CO}{sup ′}=(7.3±0.6)×10{sup 10} K km s{sup –1} pc{sup 2}. We detect continuum emission in the SMG BRI 1202–0725 North (S {sub 44} {sub GHz} = 51 ± 6 μJy), while the quasar is detected with S {sub 44} {sub GHz} = 24 ± 6 μJy and in BRI 1335–0417 we measure S {sub 44} {sub GHz} = 40 ± 7 μJy. Combining our continuum observations with previous data at (rest-frame) far-infrared and centimeter wavelengths, we fit three-component models in order to estimate the star formation rates. This spectral energy distribution fitting suggests that the dominant contribution to the observed 44 GHz continuum is thermal dust emission, while either thermal free-free or synchrotron emission contributes less than 30%.« less

Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars

NASA Astrophysics Data System (ADS)

Honnappa, Vijayakumar; Prabhakar, Vedavvathi

Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars Vijayakumar H. Doddamani*and P. Vedavathi Department of Physics, Bangalore University, Bangalore-560056, *Corresponding author:drvkdmani@gmail.com, Abstract The line and continuum flux variability is a hallmark phenomenon of Seyfert 1 galaxies and quasars. Large amplitude luminosity variability is observed in AGNs from x-rays through radio waves over a wide-ranging timescales from minutes to years. The combinations of high luminosity and short variability time scales suggests, that the power of AGN is produced by a phenomena more efficient in terms of energy release per unit mass than ordinary stellar processes. The basic structure of AGNs thus developed based on the variability studies consists of a central super massive black hole surrounded by an accretion disk or more generally optically thick plasma radiating brightly at UV and soft X-ray wavelengths. The variability studies have been important tools of understanding the physics of the central regions of AGNs, which in general cannot be resolved with the existing or planned ground and space telescopes. Therefore, we have undertaken a study of the simultaneous ultraviolet line and continuum flux variability studies in MRK501, ESOB113-IG45 (also called as Fairall 9), MRK1506, MRK1095 V*GQCOM, PG1211+143, MRK205, PG1226+023 (also known as 3C273), PG1351+640, MRK 1383, MRK876 and QSO2251-178 as these objects have been repeatedly observed by IUE satellite over several years.. It is observed that Fairall 9, MRK 1095 and 3C273 exhibit the large amplitude variability (» 30 times) over the observed timescale, which spans several years. The remaining nine objects exhibit small amplitude (» 5 times) variability over the long time scale of observations. The highest amplitude variability is observed in Lya with a least in the MgII line. The amplitude of variability decreases in the order of Lya, CIV and Mg II, lines. These results suggest that the BLR is spatially stratified into different regions from the central compact nuclear engine. Keywords: Active galaxies, Seyfert galaxies, Quasars, Line and continuum, Variability, Supermassive black hole

A New Compton-Thick AGN in Our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

NASA Technical Reports Server (NTRS)

Annuar, A.; Alexander, D. M.; Ghandi, P.; Lansbury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.;

Black Hole Demographics in and Nuclear Properties of Nearby Low Luminosity Radio Galaxies; Connections to Radio Activity?

NASA Technical Reports Server (NTRS)

Baum, S. A.; Kleijn, G. A. Verdoes; Xu, C.; ODea, C. P.; deZeeuw, P. T.

2004-01-01

We combine the results of an HST STIS and WFPC study of a complete sample of 21 nearby UGC low luminosity radio galaxies with the results of a radio VLA and VLBA study of the same sample. We examine the relationship between the stellar and gaseous properties of the galaxies on tens to hundreds of parsec scale with the properties of the radio jets on the same scale. From the VLA and VLBA data we constrain the physics of the outflowing radio plasma from the tens of parsecs to hundreds of kiloparsec scales. From the WFPC2 H alpha and dust images and the STIS kinematics of the near nuclear gas we obtain constraints on the orientation of near nuclear disks of gas and measures of the nuclear stellar, continuum point source, and line emission fluxes. Under the statistically supported assumption that the radio jet issues perpendicular to the disk, we use the orientation of the optical (large scale accretion?) disks to constrain the three-dimensional orientation of the radio ejection. From HST/STIS spectroscopy of the near-nuclear emission line gas we obtain measures/limits on the black hole masses. We examine correlations between the VLBA and VLA-scale radio emission, the nuclear line emission, and the nuclear optical and radio continuum emission. Though our sample is relatively small, it is uniquely well defined, spans a narrow range in redshift and we have a consistent set of high resolution data with which to carefully examine these relationships. We use the combined radio and optical data to: 1) Constrain the orientation, physics, and bulk outflow speed of the radio plasma; 2) Put limits on the mass accretion rate and study the relationship between black hole mass, radio luminosity, and near nuclear gaseous content; 3) Provide insight into the relationship between BL Lac objects and low luminosity radio galaxies.

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

Danforth, Charles W.; Stocke, John T.; France, Kevin

The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Ly α recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope ( HST ) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Ly α emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of themore » supermassive black hole in these radio-mode active galactic nuclei. We observe strong Ly α emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Ly α , which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Ly α luminosities ∼10{sup 40} erg s{sup -1} are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Ly α -emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Ly α luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Ly α , a clear indicator of relativistic beaming in our direction. Given their substantial space density (∼4 × 10{sup -3} Mpc{sup -3}), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (∼10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.« less

HST/COS Observations Of Lyman-α Emission From =0.03 Star Forming Galaxies

NASA Astrophysics Data System (ADS)

Wofford, Aida; Leitherer, C.; Salzer, J.; COS Science Team

2012-01-01

Although HI Lyman-alpha (Lyα, 1216 Å) is expected to be the strongest recombination line in HII nebulae, it is resonantly scattered by neutral hydrogen and is easily destroyed by dust. And yet, some star-forming galaxies show Lyα in emission. As evidenced by high dispersion HST/GHRS+STIS FUV spectroscopy of a handful of local (z<0.03) galaxies, the velocity shift between the neutral gas and the ionized gas plays a key role in driving the observed Lyα escape. We present HST/COS/G130M 1150-1450 Å (observed-frame) spectroscopy of 20 new targets located at a mean redshift of =0.03. The targets were selected from the KISSR survey on the basis of their GALEX FUV continuum luminosity. The observations cover the central 1-2 kpc of each galaxy, a wide range in metallicity ([O/H]=-0.83 to 0.38), and at least two orders of magnitude in FUV continuum luminosity. Seven objects show Lyα emission in the form of a P-Cygni or double-peaked profile. For 6/7 of the latter objects we are able to show that the emission is accompanied of O I gas outflows with speeds of up to 200 km/s. Two objects have Lyα luminosities comparable to the GALEX Lyα luminosities of targets at =0.3, but we find no Lyα emitters with EW(Lyα)>20 Å, such as those discovered with GALEX at z=0.2-0.35. We compare the observed Lyα/Hα line intensity ratios with predictions from dust-free cases A and B recombination under normal HII region conditions. We find evidence of O I gas inflow in the most metal-poor objects. This work is supported by NASA grant N1317.

The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H{sub 2}O Dissociation

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

France, Kevin; Roueff, Evelyne; Abgrall, Hervé, E-mail: kevin.france@colorado.edu

The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of some CTTSs is a broad emission approximately centered at 1600 Å, which has been referred to as the “1600 Å Bump.” The origin of this feature remains unclear. In an effort to better understand the molecular properties of planet-forming disks and the UV spectral properties of accreting protostars, we havemore » assembled archival FUV spectra of 37 disk-hosting systems observed by the Hubble Space Telescope -Cosmic Origins Spectrograph. Clear 1600 Å Bump emission is observed above the smooth, underlying 1100–1800 Å continuum spectrum in 19/37 Classical T Tauri disks in the HST -COS sample, with the detection rate in transition disks (8/8) being much higher than that in primordial or non-transition sources (11/29). We describe a spectral deconvolution analysis to separate the Bump (spanning 1490–1690 Å) from the underlying FUV continuum, finding an average Bump luminosity L (Bump) ≈ 7 × 10{sup 29} erg s{sup −1}. Parameterizing the Bump with a combination of Gaussian and polynomial components, we find that the 1600 Å Bump is characterized by a peak wavelength λ {sub o} = 1598.6 ± 3.3 Å, with FWHM = 35.8 ± 19.1 Å. Contrary to previous studies, we find that this feature is inconsistent with models of H{sub 2} excited by electron -impact. We show that this Bump makes up between 5%–50% of the total FUV continuum emission in the 1490–1690 Å band and emits roughly 10%–80% of the total fluorescent H{sub 2} luminosity for stars with well-defined Bump features. Energetically, this suggests that the carrier of the 1600 Å Bump emission is powered by Ly α photons. We argue that the most likely mechanism is Ly α -driven dissociation of H{sub 2}O in the inner disk, r ≲ 2 au. We demonstrate that non-thermally populated H{sub 2}O fragments can qualitatively account for the observed emission (discrete and continuum) and find that the average Ly α -driven H{sub 2}O dissociation rate is 1.7 × 10{sup 42} water molecules s{sup −1}.« less

AKARI IRC 2.5-5 μm spectroscopy of infrared galaxies over a wide luminosity range

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

Ichikawa, Kohei; Ueda, Yoshihiro; Imanishi, Masatoshi

2014-10-20

We present the result of a systematic infrared 2.5-5 μm spectroscopic study of 22 nearby infrared galaxies over a wide infrared luminosity range (10{sup 10} L {sub ☉} < L {sub IR} < 10{sup 13} L {sub ☉}) obtained from the AKARI Infrared Camera (IRC). The unique band of the AKARI IRC spectroscopy enables us to access both the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission feature from star-forming activity and the continuum of torus-dust emission heated by an active galactic nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover 14 buried AGNs. The large fraction ofmore » buried AGNs suggests that AGN activity behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies (U/LIRGs). We also find that both the fraction and energy contribution of buried AGNs increase with infrared luminosity from 10{sup 10} L {sub ☉} to 10{sup 13} L {sub ☉}, including normal infrared galaxies with L {sub IR} < 10{sup 11} L {sub ☉}. The energy contribution from AGNs in the total infrared luminosity is only ∼7% in LIRGs and ∼20% in ULIRGs, suggesting that the majority of the infrared luminosity originates from starburst activity. Using the PAH emission, we investigate the luminosity relation between star formation and AGNs. We find that these infrared galaxies exhibit higher star formation rates than optically selected Seyfert galaxies with the same AGN luminosities, implying that infrared galaxies could be an early evolutionary phase of AGN.« less

Early Science with the Large Millimeter Telescope: observations of dust continuum and CO emission lines of cluster-lensed submillimetre galaxies at z=2.0-4.7

NASA Astrophysics Data System (ADS)

Zavala, J. A.; Yun, M. S.; Aretxaga, I.; Hughes, D. H.; Wilson, G. W.; Geach, J. E.; Egami, E.; Gurwell, M. A.; Wilner, D. J.; Smail, Ian; Blain, A. W.; Chapman, S. C.; Coppin, K. E. K.; Dessauges-Zavadsky, M.; Edge, A. C.; Montaña, A.; Nakajima, K.; Rawle, T. D.; Sánchez-Argüelles, D.; Swinbank, A. M.; Webb, T. M. A.; Zeballos, M.

2015-09-01

We present Early Science observations with the Large Millimeter Telescope, AzTEC 1.1 mm continuum images and wide bandwidth spectra (73-111 GHz) acquired with the Redshift Search Receiver, towards four bright lensed submillimetre galaxies identified through the Herschel Lensing Survey-snapshot and the Submillimetre Common-User Bolometer Array-2 Cluster Snapshot Survey. This pilot project studies the star formation history and the physical properties of the molecular gas and dust content of the highest redshift galaxies identified through the benefits of gravitational magnification. We robustly detect dust continuum emission for the full sample and CO emission lines for three of the targets. We find that one source shows spectroscopic multiplicity and is a blend of three galaxies at different redshifts (z = 2.040, 3.252, and 4.680), reminiscent of previous high-resolution imaging follow-up of unlensed submillimetre galaxies, but with a completely different search method, that confirm recent theoretical predictions of physically unassociated blended galaxies. Identifying the detected lines as 12CO (Jup = 2-5) we derive spectroscopic redshifts, molecular gas masses, and dust masses from the continuum emission. The mean H2 gas mass of the full sample is (2.0 ± 0.2) × 1011 M⊙/μ, and the mean dust mass is (2.0 ± 0.2) × 109 M⊙/μ, where μ ≈ 2-5 is the expected lens amplification. Using these independent estimations we infer a gas-to-dust ratio of δGDR ≈ 55-75, in agreement with other measurements of submillimetre galaxies. Our magnified high-luminosity galaxies fall on the same locus as other high-redshift submillimetre galaxies, extending the L^' }_CO-LFIR correlation observed for local luminous and ultraluminous infrared galaxies to higher far-infrared and CO luminosities.

A census of the Carina Nebula - II. Energy budget and global properties of the nebulosity

NASA Astrophysics Data System (ADS)

Smith, Nathan; Brooks, Kate J.

2007-08-01

The first paper in this series took a direct census of energy input from the known OB stars in the Carina Nebula, and in this paper we study the global properties of the surrounding nebulosity. This detailed comparison may prove useful for interpreting observations of extragalactic giant HII regions and ultraluminous infrared (IR) galaxies. We find that the total IR luminosity of Carina is about 1.2 × 107Lsolar, accounting for only about 50-60 per cent of the known stellar luminosity from Paper I. Similarly, the ionizing photon luminosity derived from the integrated radio continuum is about 7 × 1050 s-1, accounting for ~75 per cent of the expected Lyman continuum from known OB stars. The total kinetic energy of the nebula is about 8 × 1051 erg, or ~30 per cent of the mechanical energy from stellar winds over the lifetime of the nebula, so there is no need to invoke a supernova (SN) explosion based on energetics. Warm dust grains residing in the HII region interior dominate emission at 10-30μm, but cooler grains at 30-40K dominate the IR luminosity and indicate a likely gas mass of ~106Msolar. We find an excellent correlation between the radio continuum and 20-25μm emission, consistent with the idea that the ~80-K grain population is heated by trapped Lyα photons. Similarly, we find a near perfect correlation between the far-IR optical depth map of cool grains and 8.6-μm hydrocarbon emission, indicating that most of the nebular mass resides as atomic gas in photodissociation regions and not in dense molecular clouds. Synchronized star formation around the periphery of Carina provides a strong case that star formation here was indeed triggered by stellar winds and ultraviolet radiation. This second generation appears to involve a cascade toward preferentially intermediate- and low-mass stars, but this may soon change when ηCarinae and its siblings explode. If the current reservoir of atomic and molecular gas can be tapped at that time, massive star formation may be rejuvenated around the periphery of Carina much as if it were a young version of Gould's Belt. Furthermore, when these multiple SNe occur, the triggered second generation will be pelted repeatedly with SN ejecta bearing short-lived radioactive nuclides. Carina may therefore represent the most observable analogue to the cradle of our own Solar system.

X-shooter spectroscopy of young stellar objects. IV. Accretion in low-mass stars and substellar objects in Lupus

NASA Astrophysics Data System (ADS)

Alcalá, J. M.; Natta, A.; Manara, C. F.; Spezzi, L.; Stelzer, B.; Frasca, A.; Biazzo, K.; Covino, E.; Randich, S.; Rigliaco, E.; Testi, L.; Comerón, F.; Cupani, G.; D'Elia, V.

2014-01-01

We present VLT/X-shooter observations of a sample of 36 accreting low-mass stellar and substellar objects (YSOs) in the Lupus star-forming region, spanning a range in mass from ~0.03 to ~1.2 M⊙, but mostly with 0.1 M⊙

Radio properties of type 1.8 and 1.9 Seyfert galaxies

NASA Technical Reports Server (NTRS)

Ulvestad, James S.

1986-01-01

A number of type 1.8 and 1.9 Seyfert galaxies have been observed at the VLA in order to compare their properties with those of the other types of Seyfert galaxy. The observed types have radio luminosities in the range of 10 to the 39th-40.5th args/s, with the median near 10 to the 40th ergs/s. Most of these galaxies have radio sources with diameters of about 500 pc or less. The ratio of radio luminosity to featureless optical continuum luminosity in the Seyfert 1.8/12.9 galaxies and Seyfert 1.2/1.5 galaxies is intermediate between the values for Seyfert 1 and Seyfert 2 galaxies. The infrared-to-radio ratio decreases along the sequence from Seyfert 1 galaxies, through intermediate Seyfert galaxies, to Seyfert 2 galaxies. This systematic statistical difference in the ratio of two aspect-independent quantities implies that the differences among the Seyfert classes cannot be attributed solely to differences in viewing angle.

Evolution of the symbiotic binary system AG Pegasi - The slowest classical nova eruption ever recorded

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Mikolajewska, Joanna; Mikolajewski, Maciej; Polidan, Ronald S.; Slovak, Mark H.

1993-01-01

We present an analysis of new and existing photometric and spectroscopic observations of the ongoing eruption in the symbiotic star AG Pegasi, showing that this binary has evolved considerably since the turn of the century. Recent dramatic changes in both the UV continuum and the wind from the hot component allow a more detailed analysis than in previous papers. AG Peg is composed of a normal M3 giant and a hot, compact star embedded in a dense, ionized nebula. The hot component powers the activity observed in this system, including a dense wind and a photoionized region within the outer atmosphere of the red giant. The hot component contracted in radius at roughly constant luminosity from 1850 to 1985. Its bolometric luminosity declined by a factor of about 4 during the past 5 yr. Both the mass loss rate from the hot component and the emission activity decreased in step with the hot component's total luminosity, while photospheric radiation from the red giant companion remained essentially constant.

The Non-Stellar Infrared Continuum of Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Alonso-Herrero, Almudena; Quillen, Alice C.; Simpson, Chris; Efstathiou, Andreas; Ward, Martin J.

2000-01-01

JHKL'M (1 - 5 micrometers) imaging of a sample of Seyfert 2 galaxies is presented. We have performed an accurate estimate of the near-infrared non-stellar nuclear fluxes. We confirm that the near-infrared nuclear continuum between 1 and 2.2microns of some Seyfert 2s is dominated by stellar emission, whereas the continuum emission at longer wavelengths (lambda = 3 - 5 micrometers) is almost entirely non-stellar in origin. The non-stellar spectral energy distributions (SED) in the infrared (up to 15 micrometers) of Seyfert galaxies show a variety of shapes, and they are well reproduced with the tapered disk models of Efstathiou & Rowan-Robinson (1995). We have used two models, one including an optically thin cone component found to fit the SED of NGC 1068, and a coneless model. Although our modelling of the SEDs does not allow us to favor either model to account for all the observed SEDs, we find that the viewing angle towards the central source is well constrained by both models. The galaxies in our sample have fitted values of the viewing angle in the range Theta(sub V) = 0 deg - 64 deg, for the assumed model parameters. We have also investigated non-stellar color-color diagrams (L' - M vs. H - M and L' - M vs. H - L'). The colors of the Seyfert galaxies with viewing angles Theta(sub v) less than 30 deg are better reproduced with the cone model. These diagrams provide a good means to separate Seyfert 2s with moderate obscuration (A(sub V) approx. less than 20 mag from hard X-ray observations) from those with high obscuration. The ground-based 4.8 microns and ISO 9.6 microns luminosities are well correlated with the hard X-ray luminosities of Seyfert ls and 2s. These continuum emissions appear as a good indicator of the AGN luminosity, at least in the cases of hard X-ray Compton-thin Seyfert galaxies (N(sub H) less than or = 10(exp 24)/sq cm). We finally stress the finding that some Compton thick galaxies show bright non-stellar emission at 5 microns This suggests that the near-infrared emission in Seyfert galaxies is produced in an extended component illuminated by the central source, that is more visible from all viewing angles, providing a good explanation for the differing N(sub H)/A(sub V) ratios found in some Seyfert 2s. We discuss possible implications of mid-infrared surveys for the search of counterparts of highly obscured hard X-ray sources.

Morphology and luminosity segregation of galaxies in nearby loose groups

NASA Astrophysics Data System (ADS)

Girardi, M.; Rigoni, E.; Mardirossian, F.; Mezzetti, M.

2003-08-01

We study morphology and luminosity segregation of galaxies in loose groups. We analyze the two catalogs of groups identified in the Nearby Optical Galaxy (NOG) sample, by means of hierarchical and percolation ``friends-of-friends'' methods (HG and PG catalogs, respectively). In the first part of our analysis we consider 387 and 436 groups of HG and PG and compare morphology- (luminosity-) weighted to unweighted group properties: velocity dispersion, mean pairwise distance, and mean groupcentric distance of member galaxies. The second part of our analysis is based on two ensemble systems, one for each catalog, built by suitably combining together galaxies of all groups (1584 and 1882 galaxies for HG and PG groups). We find that earlier-type (brighter) galaxies are more clustered and lie closer to the group centers, both in position and in velocity, than later-type (fainter) galaxies. Spatial segregations are stronger than kinematical segregations. These effects are generally detected at the >˜ 3-sigma level. Luminosity segregation is shown to be independent of morphology segregation. Our main conclusions are strengthened by the detection of segregation in both hierarchical and percolation catalogs. Our results agree with a continuum of segregation properties of galaxies in systems, from low-mass groups to massive clusters.

Multiwavelength Photometric and Spectropolarimetric Analysis of the FSRQ 3C 279

NASA Astrophysics Data System (ADS)

Patiño-Álvarez, V. M.; Fernandes, S.; Chavushyan, V.; López-Rodríguez, E.; León-Tavares, J.; Schlegel, E. M.; Carrasco, L.; Valdés, J.; Carramiñana, A.

2018-06-01

In this paper, we present light curves for 3C 279 over a time period of six years; from 2008 to 2014. Our multiwavelength data comprise 1 mm to gamma-rays, with additional optical polarimetry. Based on the behaviour of the gamma-ray light curve with respect to other bands, we identified three different activity periods. One of the activity periods shows anomalous behaviour with no gamma-ray counterpart associated with optical and NIR flares. Another anomalous activity period shows a flare in gamma-rays, 1 mm and polarization degree, however, it does not have counterparts in the UV continuum, optical and NIR bands. We find a significant overall correlation of the UV continuum emission, the optical and NIR bands. This correlation suggests that the NIR to UV continuum is co-spatial. We also find a correlation between the UV continuum and the 1 mm data, which implies that the dominant process in producing the UV continuum is synchrotron emission. The gamma-ray spectral index shows statistically significant variability and an anti-correlation with the gamma-ray luminosity. We demonstrate that the dominant gamma-ray emission mechanism in 3C 279 changes over time. Alternatively, the location of the gamma-ray emission zone itself may change depending on the activity state of the central engine.

Ionized absorbers, ionized emitters, and the X-ray spectrum of active galactic nuclei

NASA Technical Reports Server (NTRS)

Netzer, Hagai

1993-01-01

Broad absorption features are common in the X-ray spectrum of low-luminosity AGNs. The features have been modeled by leaky neutral absorbers or by highly ionized gas that completely occult the continuum source. Such models are incomplete since they do not take into account all the physical processes in the gas. In particular, no previous model included the X-ray emission by the ionized absorbing gas and the reflection of the continuum source radiation. The present work discusses the emission, absorption, and reflection properties of photoionized gases with emphasis on conditions thought to prevail in AGNs. It shows that such gas is likely to produce intense X-ray line and continuum radiation and to reflect a sizable fraction of the nonstellar continuum at all energies. If such gas is indeed responsible for the observed X-ray absorption, then absorption edges are much weaker than commonly assumed, and some residual X-ray continuum is likely to be observed even if the line of sight is completely blocked. Moreover, X-ray emission features may show up in sources not showing X-ray absorption. This has immense consequences for medium-resolution X-ray missions, such as BBXRT and Astro-D, and for the planned high-resolution experiments on board XMM and AXAF.

Search for correlated UV and x ray absorption of NGC 3516

NASA Technical Reports Server (NTRS)

Martin, Christopher; Halpern, Jules P.; Kolman, Michiel

1991-01-01

NGC 3516, a low-luminosity Seyfert galaxy, is one of a small fraction of Seyfert galaxies that exhibit broad absorption in a resonance line. In order to determine whether the UV and x ray absorption in NGC 3516 are related, 5 IUE observations were obtained, quasi-simultaneously with 4 Ginga observations. The results are presented and discussed. The following subject areas are covered: short-term UV variability; emission lines; galactic absorption lines; the C IV, N V, and Si IV absorption features; lower limit on the carbon column density; estimate of the distance from the absorber to the continuum source; variability in the continuum and absorption; a comparison with BAL QSO's; and the x ray-UV connection.

A Long-Term Space Astrophysics Research Program. The Evolution of the Quasar Continuum

NASA Technical Reports Server (NTRS)

Elvis, M.

1998-01-01

The grant "The Evolution of the Quasar Continuum" resulted in over 53 published referred papers and conference proceedings. The more significant of these papers are listed below, and abstracts are attached. The papers address a wide range of issues involving the evolution of quasars, their electromagnetic emissions, and their environment, from nearby low luminosity Seyfert galaxies to quasars at the highest redshifts. Primarily observational in content the work nonetheless included theoretical studies of quasar accretion disks that attempt to explain the observed time variability of quasars, and the overall 'demographics' of the quasar population. The work carried out under this grant has laid a strong foundation for ongoing and future research with AXAF, HST and other new facilities.

A Long-Term Space Astrophysics Research Program: The Evolution of the Quasar Continuum

NASA Technical Reports Server (NTRS)

Elvis, M.; Oliversen, Ronald K. (Technical Monitor)

2001-01-01

Four papers have been written. One reports on the major study funded by this grant: a pan-chromatic study of the quasar continuum at redshift 3. Two others make use of the quasar continuum shapes to find the minimum total accretion luminosity of the Universe, and hence the efficiency and spin of supermassive black holes; the second shows that the reemission of absorbed quasar radiation alleviates a major problem with galaxy formation and the FIR background. The last paper recognizes the role quasars may play in the initial formation of dust in the early Universe. The major study of a sample of z=3 and its comparison with a sample of z=0.l quasars across the whole X-ray to radio spectrum was completed and accepted for publication in ApJ Supplements. This study comprises the thesis work of Olga Kuhn. The two samples are matched in evolved luminosity, and so should be sampling the same black hole population at different z, and in different accretion states. Despite this no strong differences were found between the samples, except in the 'small bump' region of the optical/UV. This region is dominated by FeII emission, and may indicate abundance evolution in quasars. The lack of overall spectral changes argues strongly against a single population of quasars fading over cosmic time, and for a multiple generation, or multiple outburst model for quasars. A study of the total luminosity absorbed from quasars and re-emitted in the infrared produced two results (reported in two papers): The minimum intrinsic luminosity/Gpc(3) from AGN compared with the measured mass density in supermassive black holes [Gpc(-3)] requires a conversion efficiency of accreted mass into luminosity of greater than 15%. Non-rotating black holes cannot exceed 5% efficiency, while rapidly rotating black holes can reach 47%. Hence our result requires that most supermassive black holes must be rapidly rotating. The second result comes from considering the contribution that the re-radiated quasar radiation makes to the far infrared background (FIRB). The effective temperature of the re radiation is tightly constrained, but the detailed shape (e.g. line emission, range of temperature) is only of second order importance. At least 15perhaps 20-25% of the FIR background must come from AGN. This contribution significantly relieves problems in galaxy evolution that come from trying to use only starlight to make the FIRB. The third paper addresses the origin of the dust obscuration that is so widespread in AGN. The standard assumption is that the dust comes from the normal star-formation processes in galaxies and is drawn close to the nucleus along with the gas that powers the accretion. In complete contrast, using a wind outflow model for the broad emission line (BEL) region (Elvis 2000) as a basis, we show that BEL clouds will expand, cool and form dust as they flow outward, in strict analogy to the stellar winds of red supergiants.

The X-ray luminosity functions of Abell clusters from the Einstein Cluster Survey

NASA Technical Reports Server (NTRS)

Burg, R.; Giacconi, R.; Forman, W.; Jones, C.

1994-01-01

We have derived the present epoch X-ray luminosity function of northern Abell clusters using luminosities from the Einstein Cluster Survey. The sample is sufficiently large that we can determine the luminosity function for each richness class separately with sufficient precision to study and compare the different luminosity functions. We find that, within each richness class, the range of X-ray luminosity is quite large and spans nearly a factor of 25. Characterizing the luminosity function for each richness class with a Schechter function, we find that the characteristic X-ray luminosity, L(sub *), scales with richness class as (L(sub *) varies as N(sub*)(exp gamma), where N(sub *) is the corrected, mean number of galaxies in a richness class, and the best-fitting exponent is gamma = 1.3 +/- 0.4. Finally, our analysis suggests that there is a lower limit to the X-ray luminosity of clusters which is determined by the integrated emission of the cluster member galaxies, and this also scales with richness class. The present sample forms a baseline for testing cosmological evolution of Abell-like clusters when an appropriate high-redshift cluster sample becomes available.

Predictions for imaging and spectroscopic surveys of galaxies and Active Galactic Nuclei in the mid-/far-Infrared

NASA Astrophysics Data System (ADS)

Bonato, Matteo

2015-02-01

While continuum imaging data at far-infrared to sub-millimeter wavelengths have provided tight constraints on the population properties of dusty star-forming galaxies up to high redshifts, future space missions like the Space Infra-Red Telescope for Cosmology and Astrophysics (SPICA) and ground based facilities like the Atacama Large Millimeter/submillimeter Array (ALMA) and the Cerro Chajnantor Atacama Telescope (CCAT) will allow detailed investigations of their physical properties via their mid-/far-infrared line emission. The goal of this thesis project was to carry out predictions for these spectroscopic surveys using both a phenomenological approach and physically grounded models. These predictions are useful to optimize the planning of the surveys. In the first part of the work, I present updated predictions for the number counts and the redshift distributions of star-forming galaxies spectroscopically detectable by these future missions. These predictions exploit a recent upgrade of evolutionary models, that includes the effect of strong gravitational lensing, in the light of the most recent Herschel and South Pole Telescope (SPT) data. Moreover the relations between line and continuum infrared luminosity are re-assessed, considering also differences among source populations, with the support of extensive simulations that take into account dust obscuration. My reference model for the redshift dependent IR luminosity functions is the one worked out by Cai et al. (2013) based on a comprehensive hybrid approach combining a physical model for the progenitors of early-type galaxies with a phenomenological one for late-type galaxies. The derived line luminosity functions are found to be highly sensitive to the spread of the line to continuum luminosity ratios. Estimates of the expected numbers of detections per spectral line by the SpicA FAR infrared Instrument (SAFARI) and by CCAT surveys for different integration times per field of view at fixed total observing time are presented. Comparing with the earlier estimates by Spinoglio et al. (2012), I find, in the case of SPICA-SAFARI, differences within a factor of two in most cases, but occasionally much larger. More substantial differences are found for CCAT. Thereafter I present new estimates of redshift-dependent luminosity functions of IR lines detectable by SPICA-SAFARI and excited both by star formation and by AGN activity. The new estimates improve over previous work by dealing in a self consistent way with the emission of galaxies as a whole, including both the starburst and the AGN component. While the galaxy-AGN co-evolution was already worked out by Cai et al. (2013) in the case of proto-spheroidal galaxies, the evolution of late-type galaxies was dealt with independently of that of AGNs associated with them. I upgraded the model to enable it to take into account in a coherent way the contributions of both starbursts and AGNs to the IR emission during the cosmic evolution also of late-type galaxies. New relationships between line and AGN bolometric luminosity have been derived and those between line and IR luminosities of the starburst component have been updated. These ingredients were used to work out predictions for the source counts in 11 mid/far-IR emission lines partially or entirely excited by AGN activity. I find that the statistics of the emission line detection of galaxies as a whole is mainly determined by the star formation rate, because of the rarity of bright AGNs. I also find that the slope of the line integral number counts is flatter than 2 implying that the number of detections at fixed observing time increases more by extending the survey area than by going deeper. I thus propose a spectroscopic survey of 1 hour integration per field-of-view over an area of 5 deg^2 to detect (at 5σ) ∼760 AGNs in [OIV]25.89μm - the brightest AGN mid-infrared line - out to z ∼ 2. Pointed observations of strongly lensed or hyper-luminous galaxies previously detected by large area surveys such as those by Herschel and by SPT can provide key information on the galaxy-AGN co-evolution out to higher redshifts. Finally, as third step of the work, I present predictions for number counts and redshift distributions of galaxies detectable in continuum and in emission lines with the Mid-infrared (MIR) Instrument (SMI) proposed for SPICA. I have considered 24 MIR emission fine-structure lines, four Polycyclic Aromatic Hydrocarbon (PAH) bands (at 6.2, 7.7, 8.6 and 11.3μm) and two silicate bands (in emission and in absorption) at 9.7μm and 18.0μm. Six of these lines are primarily associated with Active Galactic Nuclei (AGNs), the others primarily with star formation. Altogether, they allow us to study the interplay between star formation and super-massive black hole growth. A survey with the SMI spectrometers of 1 hour integration per field-of-view (FoV) over an area of 1 deg 2 will yield 5 σ detections of ≃ 140 AGN lines, produced by ≃ 110 AGNs 1 , and of ≃ 5.2 × 10^4 star-forming galaxies, ≃ 1.6 × 10^4 of which will be detected in at least two lines. The combination of a shallow (20.0 deg 2 , 1.4 × 10^-1 h integration per FoV) and a deep survey (6.9 × 10^-3 deg^2 , 635 h integration time), with the SMI camera, for a total of ∼1000 h, will accurately determine the MIR number counts of galaxies and of AGNs over five orders of magnitude in flux density, reaching values more than one order of magnitude fainter than the Spitzer 24 μm surveys. This will allow us to resolve almost completely the extragalactic background and to determine the cosmic star formation rate (SFR) function down to SFRs more than 100 times fainter than reached by the Herschel Observatory.

Cinematica del gas ionizado y perfiles de luminosidad de las Galaxias Porotos Verdes

NASA Astrophysics Data System (ADS)

Diaz, R. J.; Aguero, M.; Schirmer, M.; Holheim, K.; Levenson, N.; Winge, C.

We present preliminary spectroscopic results of a sample of green bean galaxies (GBG); known to show ultra-luminous; galaxy-wide; narrow-line regions. We analyze Gemini GMOS-S;N spectra of a sample of 12 GBG in order to obtain emission line ratios; gas kinematics and luminosity profiles in some continuous bands. We report here new results that confirm that the 5008 emission extends from 5 to 17 kpc; in all cases scales similar or larger than the stellar continuums at the spectra. In the extreme case of J145533.6+044643 the emission reaches a diameter of 17.51.6kpc. We find that the continuum half light radii extend from 3 to 7 kpc; the largest scale radius at shortest wavelengths; which is consistent with the scale lengths of large spiral galaxies or merging systems. Another new result is that the spatial variation of the continuum color profiles indicate the presence of extinction and possibly star formation. FULL TEXT IN SPANISH

Ultraviolet Opacity and Fluorescence in Supernova Envelopes

NASA Technical Reports Server (NTRS)

Li, Hongwei; McCray, Richard

1996-01-01

By the time the expanding envelope of a Type 2 supernova becomes transparent in the optical continuum, most of the gamma-ray luminosity produced by radioactive Fe/Co/Ni clumps propagates into the hydrogen/helium envelope and is deposited there, if at all. The resulting fast electrons excite He 1 and H 1, the two- photon continua of which are the dominant internal sources of ultraviolet radiation. The UV radiation is blocked by scattering in thousands of resonance lines of metals and converted by fluorescence into optical and infrared emission lines that escape freely. We describe results of Monte Carlo calculations that simulate non-LTE scattering and fluorescence in more than five million allowed lines of Ca, Sc, Ti, V, Cr, Mn, Fe, Co, and Ni. For a model approximating conditions in the envelope of SN 1987A, the calculated emergent spectrum resembles the observed one. For the first 2 yr after explosion, the ultraviolet radiation (lambda less than or approximately equals 3000) is largely blocked and converted into a quasi continuum of many thousands of weak optical and infrared emission lines and some prominent emission features, such as the Ca 2 lambdalambda8600 triplet. Later, as the envelope cools and expands, it becomes more transparent, and an increasing fraction of the luminosity emerges in the UV band.

X-Ray Absorption, Nuclear Infrared Emission, and Dust Covering Factors of AGNs: Testing Unification Schemes

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.; Hernán-Caballero, A.; Barcons, X.; Asensio Ramos, A.; Watson, M. G.; Blain, A.; Caccianiga, A.; Ballo, L.; Braito, V.; Ramos Almeida, C.

2016-03-01

We present the distributions of the geometrical covering factors of the dusty tori (f2) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2-10 keV luminosities between 1042 and 1046 erg s-1, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1-20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Optically classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f2 than type 1 AGNs. Nevertheless, ˜20% of type 1 AGNs have tori with large covering factors, while ˜23%-28% of type 2 AGNs have tori with small covering factors. Low f2 are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f2 increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f2 determine the optical appearance of an AGN and control the shape of the rest-frame ˜1-20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.

BLACK HOLE MASS ESTIMATES AND RAPID GROWTH OF SUPERMASSIVE BLACK HOLES IN LUMINOUS z ∼ 3.5 QUASARS

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

Zuo, Wenwen; Wu, Xue-Bing; Fan, Xiaohui

2015-02-01

We present new near-infrared (IR) observations of the Hβ λ4861 and Mg II λ2798 lines for 32 luminous quasars with 3.2 < z < 3.9 using the Palomar Hale 200 inch telescope and the Large Binocular Telescope. We find that the Mg II FWHM is well correlated with the Hβ FWHM, confirming itself as a good substitute for the Hβ FWHM in the black hole mass estimates. The continuum luminosity at 5100 Å well correlates with the continuum luminosity at 3000 Å and the broad emission line luminosities (Hβ and Mg II). With simultaneous near-IR spectroscopy of the Hβ andmore » Mg II lines to exclude the influences of flux variability, we are able to evaluate the reliability of estimating black hole masses based on the Mg II line for high redshift quasars. With the reliable Hβ line based black hole mass and Eddington ratio estimates, we find that the z ∼ 3.5 quasars in our sample have black hole masses 1.90 × 10{sup 9} M {sub ☉} ≲ M {sub BH} ≲ 1.37 × 10{sup 10} M {sub ☉}, with a median of ∼5.14 × 10{sup 9} M {sub ☉} and are accreting at Eddington ratios between 0.30 and 3.05, with a median of ∼1.12. Assuming a duty cycle of 1 and a seed black hole mass of 10{sup 4} M {sub ☉}, we show that the z ∼ 3.5 quasars in this sample can grow to their estimated black hole masses within the age of the universe at their redshifts.« less

The Envelope Kinematics and a Possible Disk around the Class 0 Protostar within BHR7

NASA Astrophysics Data System (ADS)

Tobin, John J.; Bos, Steven P.; Dunham, Michael M.; Bourke, Tyler L.; van der Marel, Nienke

2018-04-01

We present a characterization of the protostar embedded within the BHR7 dark cloud, based on both photometric measurements from the near-infrared to millimeter and interferometric continuum and molecular line observations at millimeter wavelengths. We find that this protostar is a Class 0 system, the youngest class of protostars, measuring its bolometric temperature to be 50.5 K, with a bolometric luminosity of 9.3 L ⊙. The near-infrared and Spitzer imaging show a prominent dark lane from dust extinction separating clear bipolar outflow cavities. Observations of 13CO (J=2\\to 1), C18O (J=2\\to 1), and other molecular lines with the Submillimeter Array (SMA) exhibit a clear rotation signature on scales <1300 au. The rotation can be traced to an inner radius of ∼170 au and the rotation curve is consistent with an R ‑1 profile, implying that angular momentum is being conserved. Observations of the 1.3 mm dust continuum with the SMA reveal a resolved continuum source, extended in the direction of the dark lane, orthogonal to the outflow. The deconvolved size of the continuum indicates a radius of ∼100 au for the continuum source at the assumed distance of 400 pc. The visibility amplitude profile of the continuum emission cannot be reproduced by an envelope alone and needs a compact component. Thus, we posit that the resolved continuum source could be tracing a Keplerian disk in this very young system. If we assume that the continuum radius traces a Keplerian disk (R ∼ 120 au) the observed rotation profile is consistent with a protostar mass of 1.0 M ⊙.

NLC Luminosity as a Function of Beam Parameters

NASA Astrophysics Data System (ADS)

Nosochkov, Y.

2002-06-01

Realistic calculation of NLC luminosity has been performed using particle tracking in DIMAD and beam-beam simulations in GUINEA-PIG code for various values of beam emittance, energy and beta functions at the Interaction Point (IP). Results of the simulations are compared with analytic luminosity calculations. The optimum range of IP beta functions for high luminosity was identified.

The Ly(alpha) Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage

NASA Technical Reports Server (NTRS)

Martin, Crystal L.; Dijkstra, Mark; Henry, Alaina L.; Soto, Kurt T.; Danforth, Charles W.; Wong, Joseph

2015-01-01

We present new Hubble Space Telescope Cosmic Origins Spectrograph far-ultraviolet (far-UV) spectroscopy and Keck Echellete optical spectroscopy of 11 ultraluminous infrared galaxies (ULIRGs), a rare population of local galaxies experiencing massive gas inflows, extreme starbursts, and prominent outflows. We detect Ly(alpha) emission from eight ULIRGs and the companion to IRAS09583+4714. In contrast to the P Cygni profiles often seen in galaxy spectra, the Ly(alpha) profiles exhibit prominent, blueshifted emission out to Doppler shifts exceeding -1000 km/s in three H II-dominated and two AGN-dominated ULIRGs. To better understand the role of resonance scattering in shaping the Ly(alpha) line profiles, we directly compare them to non-resonant emission lines in optical spectra. We find that the line wings are already present in the intrinsic nebular spectra, and scattering merely enhances the wings relative to the line core. The Ly(alpha) attenuation (as measured in the COS aperture) ranges from that of the far-UV continuum to over 100 times more. A simple radiative transfer model suggests the Ly(alpha) photons escape through cavities which have low column densities of neutral hydrogen and become optically thin to the Lyman continuum in the most advanced mergers. We show that the properties of the highly blueshifted line wings on the Ly(alpha) and optical emission-line profiles are consistent with emission from clumps of gas condensing out of a fast, hot wind. The luminosity of the Ly(alpha) emission increases nonlinearly with the ULIRG bolometric luminosity and represents about 0.1-1% of the radiative cooling from the hot winds in the H II-dominated ULIRGs.

The luminosity function for the CfA redshift survey slices

NASA Technical Reports Server (NTRS)

De Lapparent, Valerie; Geller, Margaret J.; Huchra, John P.

1989-01-01

The luminosity function for two complete slices of the extension of the CfA redshift survey is calculated. The nonparametric technique of Lynden-Bell (1971) and Turner (1979) is used to determine the shape for the luminosity function of the 12 deg slice of the redshift survey. The amplitude of the luminosity function is determined, taking large-scale inhomogeneities into account. The effects of the Malmquist bias on a magnitude-limited redshift survey are examined, showing that the random errors in the magnitudes for the 12 deg slice affect both the determination of the luminosity function and the spatial density constrast of large scale structures.

Spitzer IRS Observations of Low-Mass Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Thornton, Carol E.; Barth, A. J.; Ho, L. C.; Greene, J. E.

2010-01-01

We present results from Spitzer IRS observations of a sample of 41 Seyfert galaxies with estimated black hole masses below 106 solar masses, including objects from the SDSS-selected samples of Seyfert 1 galaxies from Greene & Ho (2004) and Seyfert 2 galaxies from Barth et al. (2008), as well as NGC 4395 and POX 52. We use the IDL code PAHFIT (Smith et al. 2007) to derive measurements of continuum shapes and narrow emission line and PAH luminosities from the low-resolution spectra in order to examine the dust emission properties of these objects and investigate the relationship between Type 1 and Type 2 AGNs at low luminosities and low masses, to search for evidence of star formation, and to use emission-line diagnostics to constrain physical conditions within the narrow-line regions.

Unveiling the Composite Nature of Dust-Obscured Galaxies (DOGs) with Herschel

NASA Astrophysics Data System (ADS)

Riguccini, Laurie A.; Le Floc'h, Emeric; Mullaney, James

2015-08-01

DOGs are bright 24um-selected sources with extreme obscuration at optical wavelengths. Some of them are characterized by a rising power-law continuum of hot dust (T_D ~ 200-1000 K) in the near-IR emission indicating that their mid-IR luminosity is dominated by an AGN. Whereas DOGs with a fainter 24um flux display a stellar bump and their mid-IR luminosity is believed to be mainly powered by dusty star-formation. Another explanation is that the mid-IR emission still comes from AGN activity but the torus emission is so obscured that it becomes negligible with respect to the emission from the host component.In an effort to characterize the nature of the physical processes underlying their IR emission, we focus on DOGs (F24/FR>982) within the COSMOS field with Herschel data and derive their far-IR properties (e.g., total IR luminosities; mid-to-far IR colors; dust temperatures and masses and AGN contribution) based on SED fitting.Of particular interest are the 24um-bright DOGs (F24>1mJy). They present bluer far-IR/mid-IR colors than the rest of the sample, unveiling the potential presence of an AGN. The AGN contribution to the total 8-1000um flux increases as a function of the rest-frame 8um-luminosity irrespective of the redshift, with a stronger contribution at lower redshift. This confirms that faint DOGs (F24<1mJy) are dominated by star-formation while brighter DOGs show a larger contribution from an AGN.Is this FIR-selection technique allowing us to probe a new population of obscured AGN? Or does it corresponds to already known AGN in the X-rays, NIR or radio? The wealth of multi wavelength data in COSMOS will allow us to describe our results here.

The 1600 Å Emission Bump in Protoplanetary Disks: A Spectral Signature of H2O Dissociation

NASA Astrophysics Data System (ADS)

France, Kevin; Roueff, Evelyne; Abgrall, Hervé

2017-08-01

The FUV continuum spectrum of many accreting pre-main sequence stars, Classical T Tauri Stars (CTTSs), does not continue smoothly from the well-studied Balmer continuum emission in the NUV, suggesting that additional processes contribute to the short-wavelength emission in these objects. The most notable spectral feature in the FUV continuum of some CTTSs is a broad emission approximately centered at 1600 Å, which has been referred to as the “1600 Å Bump.” The origin of this feature remains unclear. In an effort to better understand the molecular properties of planet-forming disks and the UV spectral properties of accreting protostars, we have assembled archival FUV spectra of 37 disk-hosting systems observed by the Hubble Space Telescope-Cosmic Origins Spectrograph. Clear 1600 Å Bump emission is observed above the smooth, underlying 1100-1800 Å continuum spectrum in 19/37 Classical T Tauri disks in the HST-COS sample, with the detection rate in transition disks (8/8) being much higher than that in primordial or non-transition sources (11/29). We describe a spectral deconvolution analysis to separate the Bump (spanning 1490-1690 Å) from the underlying FUV continuum, finding an average Bump luminosity L(Bump) ≈ 7 × 1029 erg s-1. Parameterizing the Bump with a combination of Gaussian and polynomial components, we find that the 1600 Å Bump is characterized by a peak wavelength λ o = 1598.6 ± 3.3 Å, with FWHM = 35.8 ± 19.1 Å. Contrary to previous studies, we find that this feature is inconsistent with models of H2 excited by electron -impact. We show that this Bump makes up between 5%-50% of the total FUV continuum emission in the 1490-1690 Å band and emits roughly 10%-80% of the total fluorescent H2 luminosity for stars with well-defined Bump features. Energetically, this suggests that the carrier of the 1600 Å Bump emission is powered by Lyα photons. We argue that the most likely mechanism is Lyα-driven dissociation of H2O in the inner disk, r ≲ 2 au. We demonstrate that non-thermally populated H2O fragments can qualitatively account for the observed emission (discrete and continuum) and find that the average Lyα-driven H2O dissociation rate is 1.7 × 1042 water molecules s-1. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z ∼ 7

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

Zheng, Zhen-Ya; Jiang, Chunyan; Wang, Junxian

2017-06-20

We present the first results from the ongoing Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) project, which is the largest narrowband survey for z ∼ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark Energy Camera (DECam) on the NOAO/CTIO 4 m Blanco telescope, LAGER has collected 34 hr NB964 narrowband imaging data in the 3 deg{sup 2} COSMOS field. We have identified 23 Ly α Emitter candidates at z = 6.9 in the central 2-deg{sup 2} region, where DECam and public COSMOS multi-band images exist. The resulting luminosity function (LF)more » can be described as a Schechter function modified by a significant excess at the bright end (four galaxies with L {sub Lyα∼} 10{sup 43.4±0.2} erg s{sup −1}). The number density at L {sub Ly} {sub α} ∼ 10{sup 43.4±0.2} erg s{sup −1} is little changed from z = 6.6, while at fainter L {sub Lyα} it is substantially reduced. Overall, we see a fourfold reduction in Ly α luminosity density from z = 5.7 to z = 6.9. Combined with a more modest evolution of the continuum UV luminosity density, this suggests a factor of ∼3 suppression of Ly α by radiative transfer through the z ∼ 7 intergalactic medium (IGM). It indicates an IGM neutral fraction of x {sub Hi} ∼ 0.4–0.6 (assuming Ly α velocity offsets of 100–200 km s{sup −1}). The changing shape of the Ly α LF between z ≲ 6.6 and z = 6.9 supports the hypothesis of ionized bubbles in a patchy reionization at z ∼ 7.« less

ATLASGAL-selected massive clumps in the inner Galaxy. III. Dust continuum characterization of an evolutionary sample

NASA Astrophysics Data System (ADS)

König, C.; Urquhart, J. S.; Csengeri, T.; Leurini, S.; Wyrowski, F.; Giannetti, A.; Wienen, M.; Pillai, T.; Kauffmann, J.; Menten, K. M.; Schuller, F.

2017-03-01

Context. Massive-star formation and the processes involved are still poorly understood. The ATLASGAL survey provides an ideal basis for detailed studies of large numbers of massive-star forming clumps covering the whole range of evolutionary stages. The ATLASGAL Top100 is a sample of clumps selected by their infrared and radio properties to be representative for the whole range of evolutionary stages. Aims: The ATLASGAL Top100 sources are the focus of a number of detailed follow-up studies that will be presented in a series of papers. In the present work we use the dust continuum emission to constrain the physical properties of this sample and identify trends as a function of source evolution. Methods: We determine flux densities from mid-infrared to submillimeter wavelength (8-870 μm) images and use these values to fit their spectral energy distributions and determine their dust temperature and flux. Combining these with recent distances from the literature including maser parallax measurements we determine clump masses, luminosities and column densities. Results: We define four distinct source classes from the available continuum data and arrange these into an evolutionary sequence. This begins with sources found to be dark at 70 μm, followed by 24 μm weak sources with an embedded 70 μm source, continues through mid-infrared bright sources and ends with infrared bright sources associated with radio emission (I.e., H II regions). We find trends for increasing temperature, luminosity, and column density with the proposed evolution sequence, confirming that this sample is representative of different evolutionary stages of massive star formation. Our sources span temperatures from approximately 11 to 41 K, with bolometric luminosities in the range 57 L⊙-3.8 × 106L⊙. The highest masses reach 4.3 × 104M⊙ and peak column densities up to 1.1 × 1024 cm-1, and therefore have the potential to form the most massive O-type stars. We show that at least 93 sources (85%) of this sample have the ability to form massive stars and that most are gravitationally unstable and hence likely to be collapsing. Conclusions: The highest column density ATLASGAL sources cover the whole range of evolutionary stages from the youngest to the most evolved high-mass-star forming clumps. Study of these clumps provides a unique starting point for more in-depth research on massive-star formation in four distinct evolutionary stages whose well defined physical parameters afford more detailed studies. As most of the sample is closer than 5 kpc, these sources are also ideal for follow-up observations with high spatial resolution. Full Table 1, including fluxes, is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A139

Very low luminosity active galaxies and the X-ray background

NASA Technical Reports Server (NTRS)

Elvis, M.; Soltan, A.; Keel, W. C.

1984-01-01

The properties of very low luminosity active galactic nuclei are not well studied, and, in particular, their possible contribution to the diffuse X-ray background is not known. In the present investigation, an X-ray luminosity function for the range from 10 to the 39th to 10 to the 42.5th ergs/s is constructed. The obtained X-ray luminosity function is integrated to estimate the contribution of these very low luminosity active galaxies to the diffuse X-ray background. The construction of the X-ray luminosity function is based on data obtained by Keel (1983) and some simple assumptions about optical and X-ray properties.

Simulations of dust in interacting galaxies

NASA Astrophysics Data System (ADS)

Jonsson, Patrik

This dissertation studies the effects of dust in N-body simulations of interacting galaxies. A new Monte-Carlo radiative-transfer code, Sunrise , is used in conjunction with hydrodynamic simulations. Results from radiative- transfer calculations in over 20 SPH simulations of disk-galaxy major mergers (Cox, 2004) are presented. Dust has a profound effect on the appearance of these simulations. At peak luminosities, 90% of the bolometric luminosity is absorbed by dust. The dust obscuration increases with luminosity in such a way that the brightness at UV/ visual wavelengths remains roughly constant. A general relationship between the fraction of energy absorbed and the ratio of bolometric luminosity to baryonic mass is found to hold in galaxies with metallicities >0.7 [Special characters omitted.] over a factor of 50 in mass. The accuracy to which the simulations describe observed starburst galaxies is evaluated by comparing them to observations by Meurer et al. (1999) and Heckman et al. (1998). The simulations are found to follow a relation similar to the IRX-b relation found by Meurer et al. (1999) when similar luminosity objects are considered. The highest-luminosity simulated galaxies depart from this relation and occupy the region where local LIRGs/ULIRGs are found. Comparing to the Heckman et al. (1998) sample, the simulations are found to obey the same relations between UV luminosity, UV color, IR luminosity, absolute blue magnitude and metallicity as the observations. This agreement is contingent on the presence of a realistic mass-metallicity relation, and Milky-Way-like dust. SMC-like dust results in far too red a UV continuum slope. On the whole, the agreement between the simulated and observed galaxies is impressive considering that the simulations have not been fit to agree with the observations, and we conclude that the simulations provide a realistic replication of the real universe. The simulations are used to study the performance of star-formation indicators in the presence of dust. The far-infrared luminosity is found to be reliable. In contrast, the Ha and far-ultraviolet luminosities suffer severely from dust attenuation, and dust corrections can only partially remedy the situation.

COLA. III. Radio Detection of Active Galactic Nucleus in Compact Moderate Luminosity Infrared Galaxies

NASA Astrophysics Data System (ADS)

Parra, R.; Conway, J. E.; Aalto, S.; Appleton, P. N.; Norris, R. P.; Pihlström, Y. M.; Kewley, L. J.

2010-09-01

We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median L IR = 1011.01 L sun) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores (~1021 W Hz-1) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whose VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity.

Models for infrared emission from IRAS galaxies

NASA Technical Reports Server (NTRS)

Rowan-Robinson, M.

1987-01-01

Models for the infrared emission from Infrared Astronomy Satellite (IRAS) galaxies by Rowan-Robinson and Crawford, by deJong and Brink, and by Helou, are reviewed. Rowan-Robinson and Crawford model the 12 to 100 micron radiation from IRAS galaxies in terms of 3 components: a normal disk component, due to interstellar cirrus; a starburst component, modeled as hot stars in an optically thick dust cloud; and a Seyfert component, modeled as a power-law continuum immersed in an n(r) variation r sup -1 dust cloud associated with the narrow-line region of the Seyfert nucleus. The correlations between the luminosities in the different components, the blue luminosity, and the X-ray luminosity of the galaxies are consistent with the model. Spectra from 0.1 to 1000 microns are predicted and compared with available observations. The de Jong and Brink, and Helou, model IRAS non-Seyfert galaxies in terms of a cool (cirrus) component and a warm (starburst) component. The de Jong and Brink estimate the face-on internal extinction in the galaxies and find that it is higher in galaxies with more luminous starbursts. In Helou's model the spectrum of the warm component varies strongly with the luminosity in that component. The three models are briefly compared.

Evolution of the luminosity function of quasar accretion disks

NASA Technical Reports Server (NTRS)

Caditz, David M.; Petrosian, Vahe; Wandel, Amri

1991-01-01

Using an accretion-disk model, accretion disk luminosities are calculated for a grid of black hole masses and accretion rates. It is shown that, as the black-hole mass increases with time, the monochromatic luminosity at a given frequency first increases and then decreases rapidly as this frequency is crossed by the Wien cutoff. The upper limit on the monochromatic luminosity, which is characteristic for a given epoch, constrains the evolution of quasar luminosities and determines the evolultion of the quasar luminosity function.

The quasar luminosity function at redshift 4 with the Hyper Suprime-Cam Wide Survey

NASA Astrophysics Data System (ADS)

Akiyama, Masayuki; He, Wanqiu; Ikeda, Hiroyuki; Niida, Mana; Nagao, Tohru; Bosch, James; Coupon, Jean; Enoki, Motohiro; Imanishi, Masatoshi; Kashikawa, Nobunari; Kawaguchi, Toshihiro; Komiyama, Yutaka; Lee, Chien-Hsiu; Matsuoka, Yoshiki; Miyazaki, Satoshi; Nishizawa, Atsushi J.; Oguri, Masamune; Ono, Yoshiaki; Onoue, Masafusa; Ouchi, Masami; Schulze, Andreas; Silverman, John D.; Tanaka, Manobu M.; Tanaka, Masayuki; Terashima, Yuichi; Toba, Yoshiki; Ueda, Yoshihiro

2018-01-01

We present the luminosity function of z ˜ 4 quasars based on the Hyper Suprime-Cam Subaru Strategic Program Wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. From stellar objects, 1666 z ˜ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. Their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. In combination with the quasar sample from the Sloan Digital Sky Survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of M1450 = -22 to -29 mag is constructed. The quasar luminosity function is well described by a double power-law model with a knee at M1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. The knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ˜ 2. The flat slope implies that the UV luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. If we convert the M1450 luminosity function to the hard X-ray 2-10 keV luminosity function using the relation between the UV and X-ray luminosity of quasars and its scatter, the number density of UV-selected quasars matches well with that of the X-ray-selected active galactic nuclei (AGNs) above the knee of the luminosity function. Below the knee, the UV-selected quasars show a deficiency compared to the hard X-ray luminosity function. The deficiency can be explained by the lack of obscured AGNs among the UV-selected quasars.

Luminosity and Stellar Mass Functions from the 6dF Galaxy Survey

NASA Astrophysics Data System (ADS)

Colless, M.; Jones, D. H.; Peterson, B. A.; Campbell, L.; Saunders, W.; Lah, P.

2007-12-01

The completed 6dF Galaxy Survey includes redshifts for over 124,000 galaxies. We present luminosity functions in optical and near-infrared passbands that span a range of 10^4 in luminosity. These luminosity functions show systematic deviations from the Schechter form. The corresponding luminosity densities in the optical and near-infrared are consistent with an old stellar population and a moderately declining star formation rate. Stellar mass functions, derived from the K band luminosities and simple stellar population models selected by b_J-r_F colour, lead to an estimate of the present-day stellar mass density of ρ_* = (5.00 ± 0.11) × 10^8 h M_⊙ Mpc^{-3}, corresponding to Ω_* h = (1.80 ± 0.04) × 10^{-3}.

NGC 2024: Multi-wavelength Infrared and Radio Observations

NASA Technical Reports Server (NTRS)

Smith, H. A.; Fischer, J.; Geballe, T. R.; Thronson, H. A., Jr.; Johnston, K. J.; Schwartz, P. R.; Wilson, T. L.; Crutcher, R. M.; Henkel, C.; Bieging, J.

1984-01-01

A series of far-infrared maps obtained on the KAO find the total IR luminosity of NGC 2024 is to the 4th power L, and show a peak in flux density and optical depth about 1' south of IRS 2. High resolution spectra of IRS 2 in Brackett alfa and Pfund gamma indicate the presence of an optically thick wind with M approx. 7 x 10 to the minus 7 power M sub yr to minus 1 power, from which we infer that IRS 2 is unable to supply the luminosity observed. A six centimeter continuum map peaks near the location of the far-infrared peak and confirms it as a likely site for a source to provide this luminosity. Maps in HCN, CS, and H2CO show the gas is dense in the direction of the far IR peak. Velocity analysis shows the H2 region created by the far IR source and IRS 2 forms an expanding bubble in front of which the H2CO is seen in absorption, and which is bounded in the south and behind by dense material.

Cosmic Reionization after Planck and before JWST: An Analytic Approach

NASA Astrophysics Data System (ADS)

Madau, Piero

2017-12-01

The reionization of cosmic hydrogen marks a critical juncture in the history of structure formation. Here we present a new formulation of the standard reionization equation for the evolution of the volume-averaged H II fraction that is more consistent with the accepted conceptual model of inhomogeneous intergalactic absorption. The revised equation explicitly accounts for the presence of the optically thick “Lyman-limit systems” that are known to determine the mean-free path of ionizing radiation after overlap. Integration of this equation provides a better characterization of the timing of reionization by smoothly linking the pre-overlap with the post-overlap phases of such a process. We confirm the validity of the quasi-instantaneous approximation as a predictor of reionization completion/maintenance and discuss new insights on the sources of cosmic reionization using the improved formalism. A constant emission rate into the intergalactic medium (IGM) of three Lyman continuum (LyC) photons per atom per gigayear leads to a reionization history that is consistent with a number of observational constraints on the ionization state of the z = 5–9 universe. While star-forming galaxies can dominate the reionization process if the luminosity-weighted fraction of LyC photons that escape into the IGM, {f}{esc}, exceeds 15% (for a faint magnitude cut-off of the galaxy UV luminosity function of {M}{lim}=-13 and a LyC photon yield per unit 1500 Å luminosity of {ξ }{ion}={10}25.3 {{erg}}-1 {Hz}), simple models where the product of the two unknowns {f}{esc}{ξ }{ion} is not evolving with redshift fail to reproduce the changing neutrality of the IGM observed at these epochs.

Structure and Kinematics of the BLR: What We have Learned and Where We Are

NASA Astrophysics Data System (ADS)

Gaskell, C. Martin

What has been learned from variability studies of the BLR is reviewded. The majority of our knowledge has ceom from determining only the first moment of the transfer function (the "lag"). Details of the method most widely used for determining the first moment, i.e., the partial interpolation cross correlation function (PICCF) method, are discussed. The much higher efficiency of the PICCF method compared to the discrete correlation function (DCF) method is emphasized. Recovering much beyond the first moment of the transfer function is difficult, and a plateau seems to ahve been reached in what we can learn from our present style of monitoring campaign. Directions are suggested for future observing campaigns. Obtaining simultaneous X-ray light curves is very important. Quasars with unusual double-peaked emission lines vlearly need ot be understoo as do ones with strong optical Fe II emission. Theoretical problems mentioned include (1) the reconciliation of the apparent lack of radial outflow with the blueshifting of high-ionization lines, (2) the role of electron scattering, and (3) the small apparent sizes seen in 3C 273 and some high-luminosity quasars. Continuum anisotropy offers a natural solution to the last problem.

The radio-far infrared correlation: Spiral and blue compact dwarf galaxies opposed

NASA Technical Reports Server (NTRS)

Klein, U.; Wunderlich, E.

1987-01-01

The recently established correlation between radio continuum and far infrared emission in galaxies was further investigated by comparing normal spiral and blue compact dwarf galaxies. The puzzling result is that the ratio of radio to far infrared luminosity and its dispersion is the same for both samples, although their ratios of blue to far infrared luminosity, their radio spectral indices and their dust temperatures exhibit markedly different mean values and dispersions. This suggests that the amount of energy radiated in the two regimes is enhanced in the same way although the mechanisms responsible for the two components are rather different and complex. The fact that the blue light does not increase at the same proportion shows that both the radio and the far infrared emission are connected with the recent star formation history.

Space Density Of Optically-Selected Type II Quasars From The SDSS

NASA Astrophysics Data System (ADS)

Reyes, Reinabelle; Zakamska, N. L.; Strauss, M. A.; Green, J.; Krolik, J. H.; Shen, Y.; Richards, G. T.

2007-12-01

Type II quasars are luminous Active Galactic Nuclei (AGN) whose central regions are obscured by large amounts of gas and dust. In this poster, we present a catalog of 887 type II quasars with redshifts z<0.83 from the Sloan Digital Sky Survey (SDSS), selected based on their emission lines, and derive the 1/Vmax [OIII] 5007 luminosity function from this sample. Since some objects may not be included in the sample because they lack strong emission lines, the derived luminosity function is only a lower limit. We also derive the [OIII] 5007 luminosity function for a sample of type I (broad-line) quasars in the same redshift range. Taking [OIII] 5007 luminosity as a tracer of intrinsic luminosity in both type I and type II quasars, we obtain lower limits to the type II quasar fraction as a function of [OIII] 5007 luminosity, from L[OIII] = 108.3 to 1010 Lsun, which roughly correspond to bolometric luminosities of 1044 to 1046 erg/s.

The Rapidly Rotating Sun

NASA Technical Reports Server (NTRS)

Hanasoge, Shravan M.; Duvall, Thomas L., Jr.; Sreenivasan, Katepalli R.

2012-01-01

Convection in the solar interior is thought to comprise structures at a continuum of scales, from large to small. This conclusion emerges from phenomenological studies and numerical simulations though neither covers the proper range of dynamical parameters of solar convection. In the present work, imaging techniques of time-distance helioseismology applied to observational data reveal no long-range order in the convective motion. We conservatively bound the associated velocity magnitudes, as a function of depth and the spherical-harmonic degree l to be 20-100 times weaker than prevailing estimates within the wavenumber band l < 60. The observationally constrained kinetic energy is approximately a thousandth of the theoretical prediction, suggesting the prevalence of an intrinsically different paradigm of turbulence. A fundamental question arises: what mechanism of turbulence transports the heat ux of a solar luminosity outwards? The Sun is seemingly a much faster rotator than previously thought, with advection dominated by Coriolis forces at scales l < 60.

A Multiwavelength Characterization of Proto-brown-dwarf Candidates in Serpens

NASA Astrophysics Data System (ADS)

Riaz, B.; Vorobyov, E.; Harsono, D.; Caselli, P.; Tikare, K.; Gonzalez-Martin, O.

2016-11-01

We present results from a deep submillimeter survey in the Serpens Main and Serpens/G3-G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined near- and mid-infrared spectroscopy, Herschel PACS far-infrared photometry, submillimeter continuum, and molecular gas line observations, with the aim of conducting a detailed multiwavelength characterization of “proto-brown-dwarf” (proto-BD) candidates in Serpens. We have performed continuum and line radiative transfer modeling and have considered various classification schemes to understand the structure and the evolutionary stage of the system. We have identified four proto-BD candidates, of which the lowest-luminosity source has an L bol ˜ 0.05 L ⊙. Two of these candidates show characteristics consistent with Stage 0/I systems, while the other two are Stage I-T/Class Flat systems with tenuous envelopes. Our work has also revealed a ˜20% fraction of misidentified Class 0/I/Flat sources that show characteristics consistent with Class II edge-on disk systems. We have set constraints on the mass of the central object using the measured bolometric luminosities and numerical simulations of stellar evolution. Considering the available gas+dust mass reservoir and the current mass of the central source, three of these candidates are likely to evolve into BDs.

A MULTIWAVELENGTH CHARACTERIZATION OF PROTO-BROWN-DWARF CANDIDATES IN SERPENS

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

Riaz, B.; Caselli, P.; Vorobyov, E.

2016-11-10

We present results from a deep submillimeter survey in the Serpens Main and Serpens/G3–G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined near- and mid-infrared spectroscopy, Herschel PACS far-infrared photometry, submillimeter continuum, and molecular gas line observations, with the aim of conducting a detailed multiwavelength characterization of “proto-brown-dwarf” (proto-BD) candidates in Serpens. We have performed continuum and line radiative transfer modeling and have considered various classification schemes to understand the structure and the evolutionary stage of the system. We have identified four proto-BD candidates, of which the lowest-luminosity source hasmore » an L {sub bol} ∼ 0.05 L {sub ☉}. Two of these candidates show characteristics consistent with Stage 0/I systems, while the other two are Stage I-T/Class Flat systems with tenuous envelopes. Our work has also revealed a ∼20% fraction of misidentified Class 0/I/Flat sources that show characteristics consistent with Class II edge-on disk systems. We have set constraints on the mass of the central object using the measured bolometric luminosities and numerical simulations of stellar evolution. Considering the available gas+dust mass reservoir and the current mass of the central source, three of these candidates are likely to evolve into BDs.« less

The contribution of faint AGNs to the ionizing background at z 4

NASA Astrophysics Data System (ADS)

Grazian, A.; Giallongo, E.; Boutsia, K.; Cristiani, S.; Vanzella, E.; Scarlata, C.; Santini, P.; Pentericci, L.; Merlin, E.; Menci, N.; Fontanot, F.; Fontana, A.; Fiore, F.; Civano, F.; Castellano, M.; Brusa, M.; Bonchi, A.; Carini, R.; Cusano, F.; Faccini, M.; Garilli, B.; Marchetti, A.; Rossi, A.; Speziali, R.

2018-05-01

Context. Finding the sources responsible for the hydrogen reionization is one of the most pressing issues in observational cosmology. Bright quasi-stellar objects (QSOs) are known to ionize their surrounding neighborhood, but they are too few to ensure the required HI ionizing background. A significant contribution by faint active galactic nuclei (AGNs), however, could solve the problem, as recently advocated on the basis of a relatively large space density of faint active nuclei at z > 4. Aims: This work is part of a long-term project aimed at measuring the Lyman Continuum escape fraction for a large sample of AGNs at z 4 down to an absolute magnitude of M1450 -23. We have carried out an exploratory spectroscopic program to measure the HI ionizing emission of 16 faint AGNs spanning a broad U - I color interval, with I 21-23, and 3.6 < z < 4.2. These AGNs are three magnitudes fainter than the typical SDSS QSOs (M1450 ≲-26) which are known to ionize their surrounding IGM at z ≳ 4. Methods: We acquired deep spectra of these faint AGNs with spectrographs available at the VLT, LBT, and Magellan telescopes, that is, FORS2, MODS1-2, and LDSS3, respectively. The emission in the Lyman Continuum region, close to 900 Å rest frame, has been detected with a signal to noise ratio of 10-120 for all 16 AGNs. The flux ratio between the 900 Å rest-frame region and 930 Å provides a robust estimate of the escape fraction of HI ionizing photons. Results: We have found that the Lyman Continuum escape fraction is between 44 and 100% for all the observed faint AGNs, with a mean value of 74% at 3.6 < z < 4.2 and - 25.1 ≲ M1450 ≲-23.3, in agreement with the value found in the literature for much brighter QSOs (M1450 ≲-26) at the same redshifts. The Lyman Continuum escape fraction of our faint AGNs does not show any dependence on the absolute luminosities or on the observed U - I colors of the objects. Assuming that the Lyman Continuum escape fraction remains close to 75% down to M1450 - 18, we find that the AGN population can provide between 16 and 73% (depending on the adopted luminosity function) of the whole ionizing UV background at z 4, measured through the Lyman forest. This contribution increases to 25-100% if other determinations of the ionizing UV background are adopted from the recent literature. Conclusions: Extrapolating these results to z 5-7, there are possible indications that bright QSOs and faint AGNs can provide a significant contribution to the reionization of the Universe, if their space density is high at M1450 -23. Based on observations made at the Large Binocular Telescope (LBT) at Mt. Graham (Arizona, USA). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 098.A-0862. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

Galaxy luminosity function and Tully-Fisher relation: reconciled through rotation-curve studies

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

Cattaneo, Andrea; Salucci, Paolo; Papastergis, Emmanouil, E-mail: andrea.cattaneo@oamp.fr, E-mail: salucci@sissa.it, E-mail: papastergis@astro.cornell.edu

2014-03-10

The relation between galaxy luminosity L and halo virial velocity v {sub vir} required to fit the galaxy luminosity function differs from the observed Tully-Fisher relation between L and disk speed v {sub rot}. Because of this, the problem of reproducing the galaxy luminosity function and the Tully-Fisher relation simultaneously has plagued semianalytic models since their inception. Here we study the relation between v {sub rot} and v {sub vir} by fitting observational average rotation curves of disk galaxies binned in luminosity. We show that the v {sub rot}-v {sub vir} relation that we obtain in this way can fullymore » account for this seeming inconsistency. Therefore, the reconciliation of the luminosity function with the Tully-Fisher relation rests on the complex dependence of v {sub rot} on v {sub vir}, which arises because the ratio of stellar mass to dark matter mass is a strong function of halo mass.« less

Evolution of the luminosity function of extragalactic objects

NASA Technical Reports Server (NTRS)

Petrosian, V.

1985-01-01

A nonparametric procedure for determination of the evolution of the luminosity function of extragalactic objects and use of this for prediction of expected redshift and luminosity distribution of objects is described. The relation between this statistical evolution of the population and their physical evolution, such as the variation with cosmological epoch of their luminosity and formation rate is presented. This procedure when applied to a sample of optically selected quasars with redshifts less than two shows that the luminosity function evolves more strongly for higher luminosities, indicating a larger quasar activity at earlier epochs and a more rapid evolution of the objects during their higher luminosity phases. It is also shown that absence of many quasars at redshifts greater than three implies slowing down of this evolution in the conventional cosmological models, perhaps indicating that this is near the epoch of the birth of the quasar (and galaxies).

2.0 to 2.4 micron spectroscopy of T Tauri stars

NASA Astrophysics Data System (ADS)

Hamann, F.; Simon, M.; Ridgway, S. T.

1988-03-01

Velocity-resolved 2.0-2.5-micron observations of the T Tau stars T, DF, DG, DK, HL, and RY Tau, SU Aur, and GW Ori are presented. For each of these stars except SU Aur, the Brackett gamma line was detected in emission with line widths inthe range of about 130-230 km/s. The Brackett gamma line profile of SU Aur is complex, having components of both emission and absorption. The first measurement of CO band-head emission in DG Tau is reported, and it is shown that published radio continuum fluxes of young stars far exceed what could be produced in an envelope ionized by only the stellar photospheric Lyman continuum. The excess of radio emission is found to be much greater in low-luminosity sources (e.g., the T Tau stars).

The Herschel ATLAS: Evolution of the 250 Micrometer Luminosity Function Out to z = 0.5

NASA Technical Reports Server (NTRS)

Dye, S.; Dunne, L.; Eales, S.; Smith, D. J. B.; Amblard, A.; Auld, R.; Baes, M.; Baldry, I. K.; Bamford, S.; Blain, A. W.;

Size–Luminosity Relations and UV Luminosity Functions at z = 6–9 Simultaneously Derived from the Complete Hubble Frontier Fields Data

NASA Astrophysics Data System (ADS)

Kawamata, Ryota; Ishigaki, Masafumi; Shimasaku, Kazuhiro; Oguri, Masamune; Ouchi, Masami; Tanigawa, Shingo

2018-03-01

We construct z ∼ 6–7, 8, and 9 faint Lyman break galaxy samples (334, 61, and 37 galaxies, respectively) with accurate size measurements with the software glafic from the complete Hubble Frontier Fields (HFF) cluster and parallel fields data. These are the largest samples hitherto and reach down to the faint ends of recently obtained deep luminosity functions. At faint magnitudes, however, these samples are highly incomplete for galaxies with large sizes, implying that derivation of the luminosity function sensitively depends on the intrinsic size–luminosity relation. We thus conduct simultaneous maximum-likelihood estimation of luminosity function and size–luminosity relation parameters from the observed distribution of galaxies on the size–luminosity plane with the help of a completeness map as a function of size and luminosity. At z ∼ 6–7, we find that the intrinsic size–luminosity relation expressed as r e ∝ L β has a notably steeper slope of β ={0.46}-0.09+0.08 than those at lower redshifts, which in turn implies that the luminosity function has a relatively shallow faint-end slope of α =-{1.86}-0.18+0.17. This steep β can be reproduced by a simple analytical model in which smaller galaxies have lower specific angular momenta. The β and α values for the z ∼ 8 and 9 samples are consistent with those for z ∼ 6–7 but with larger errors. For all three samples, there is a large, positive covariance between β and α, implying that the simultaneous determination of these two parameters is important. We also provide new strong lens mass models of Abell S1063 and Abell 370, as well as updated mass models of Abell 2744 and MACS J0416.1‑2403.

Sub-millimeter detected z ~ 2 radio-quiet QSOs. Accurate redshifts, black hole masses, and inflow/outflow velocities

NASA Astrophysics Data System (ADS)

Orellana, G.; Nagar, N. M.; Isaak, K. G.; Priddey, R.; Maiolino, R.; McMahon, R.; Marconi, A.; Oliva, E.

2011-07-01

Context. We present near-IR spectroscopy of a sample of luminous (MB - 27.5; Lbol > 1014 L⊙), sub-millimeter-detected, dusty (Md ~ 109 M⊙), radio-quiet quasi-stellar objects (QSOs) at z ~ 2. Aims: A primary aim is to provide a more accurate QSO redshift determination in order to trace kinematics and inflows/outflows in these sub-mm bright QSOs. Additionally, the Hα and continuum properties allow an estimation of the black hole mass and accretion rate, offering insights into the starburst-AGN connection in sub-mm bright QSOs. Methods: We measure the redshift, width, and luminosity of the Hα line, and the continuum luminosity near Hα. Relative velocity differences between Hα and rest-frame UV emission lines are used to study the presence and strength of outflows/inflows. Luminosities and line widths are used to estimate the black hole masses, bolometric luminosities, Eddington fractions, and accretion rates; these are compared to the star-formation-rate (SFR), estimated from the sub-mm derived far-infrared (FIR) luminosity. Finally our sub-mm-bright QSO sample is compared with other QSO samples at similar redshifts. Results: The Hα emission line was strongly detected in all sources. Two components - a very broad (≳5000 km s-1) Gaussian and an intermediate-width (≳1500 km s-1) Gaussian, were required to fit the Hα profile of all observed QSOs. Narrow (≲1000 km s-1) lines were not detected in the sample QSOs. The rest-frame UV emission lines in these sub-mm bright QSOs show larger than average blue-shifted velocities, potentially tracing strong - up to 3000 km s-1 - outflows in the broad line region. With the exception of the one QSO which shows exceptionally broad Hα lines, the black hole masses of the QSO sample are in the range log MBH = 9.0-9.7 and the Eddington fractions are between 0.5 and ~1. In black hole mass and accretion rate, this sub-mm bright QSO sample is indistinguishable from the Shemmer et al. (2004, ApJ, 614, 547) optically-bright QSO sample at z ~ 2; the latter is likely dominated by sub-mm dim QSOs. Previous authors have demonstrated a correlation, over six orders of magnitude, between SFR and accretion rate in active galaxies: the sub-mm bright QSOs lie at the upper extremes of both quantities and their SFR is an order of magnitude higher than that predicted from the correlation.

Luminosity function and jet structure of Gamma-Ray Burst

NASA Astrophysics Data System (ADS)

Pescalli, A.; Ghirlanda, G.; Salafia, O. S.; Ghisellini, G.; Nappo, F.; Salvaterra, R.

2015-02-01

The structure of gamma-ray burst (GRB) jets impacts on their prompt and afterglow emission properties. The jet of GRBs could be uniform, with constant energy per unit solid angle within the jet aperture, or it could be structured, namely with energy and velocity that depend on the angular distance from the axis of the jet. We try to get some insight about the still unknown structure of GRBs by studying their luminosity function. We show that low (1046-48 erg s-1) and high (i.e. with L ≥ 1050 erg s-1) luminosity GRBs can be described by a unique luminosity function, which is also consistent with current lower limits in the intermediate luminosity range (1048-50 erg s-1). We derive analytical expressions for the luminosity function of GRBs in uniform and structured jet models and compare them with the data. Uniform jets can reproduce the entire luminosity function with reasonable values of the free parameters. A structured jet can also fit adequately the current data, provided that the energy within the jet is relatively strongly structured, i.e. E ∝ θ-k with k ≥ 4. The classical E ∝ θ-2 structured jet model is excluded by the current data.

Studying the accretion geometry of EXO 2030+375 at luminosities close to the propeller regime

NASA Astrophysics Data System (ADS)

Fürst, F.; Kretschmar, P.; Kajava, J. J. E.; Alfonso-Garzón, J.; Kühnel, M.; Sanchez-Fernandez, C.; Blay, P.; Wilson-Hodge, C. A.; Jenke, P.; Kreykenbohm, I.; Pottschmidt, K.; Wilms, J.; Rothschild, R. E.

2017-10-01

The Be X-ray binary EXO 2030+375was in an extended low-luminosity state during most of 2016. We observed this state with NuSTARand Swift, supported by INTEGRALobservations and optical spectroscopy with the Nordic Optical Telescope (NOT). We present a comprehensive spectral and timing analysis of these data here to study the accretion geometry and investigate a possible onset of the propeller effect. The Hα data show that the circumstellar disk of the Be-star is still present. We measure equivalent widths similar to values found during more active phases in the past, indicating that the low-luminosity state is not simply triggered by a smaller Be disk. The NuSTARdata, taken at a 3-78 keV luminosity of 6.8 × 1035 erg s-1 (for a distance of 7.1 kpc), are nicely described by standard accreting pulsar models such as an absorbed power law with a high-energy cutoff. We find that pulsations are still clearly visible at these luminosities, indicating that accretion is continuing despite the very low mass transfer rate. In phase-resolved spectroscopy we find a peculiar variation of the photon index from 1.5 to 2.5 over only about 3% of the rotational period. This variation is similar to that observed with XMM-Newtonat much higher luminosities. It may be connected to the accretion column passing through our line of sight. With Swift/XRT we observe luminosities as low as 1034 erg s-1 where the data quality did not allow us to search for pulsations, but the spectrum is much softer and well described by either a blackbody or soft power-law continuum. This softer spectrum might be due to the accretion being stopped by the propeller effect and we only observe the neutron star surface cooling.

Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGNs: The Effects of Cloud Orientation and Anisotropic Illumination

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

Almeyda, Triana; Robinson, Andrew; Richmond, Michael

The obscuring circumnuclear torus of dusty molecular gas is one of the major components of active galactic nuclei (AGN). The torus can be studied by analyzing the time response of its infrared (IR) dust emission to variations in the AGN continuum luminosity, a technique known as reverberation mapping. The IR response is the convolution of the AGN ultraviolet/optical light curve with a transfer function that contains information about the size, geometry, and structure of the torus. Here, we describe a new computer model that simulates the reverberation response of a clumpy torus. Given an input optical light curve, the codemore » computes the emission of a 3D ensemble of dust clouds as a function of time at selected IR wavelengths, taking into account light travel delays. We present simulated dust emission responses at 3.6, 4.5, and 30 μ m that explore the effects of various geometrical and structural properties, dust cloud orientation, and anisotropy of the illuminating radiation field. We also briefly explore the effects of cloud shadowing (clouds are shielded from the AGN continuum source). Example synthetic light curves have also been generated, using the observed optical light curve of the Seyfert 1 galaxy NGC 6418 as input. The torus response is strongly wavelength-dependent, due to the gradient in cloud surface temperature within the torus, and because the cloud emission is strongly anisotropic at shorter wavelengths. Anisotropic illumination of the torus also significantly modifies the torus response, reducing the lag between the IR and optical variations.« less

COLA. III. RADIO DETECTION OF ACTIVE GALACTIC NUCLEUS IN COMPACT MODERATE LUMINOSITY INFRARED GALAXIES

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

Parra, R.; Conway, J. E.; Aalto, S.

2010-09-01

We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median L{sub IR} = 10{sup 11.01} L{sub sun}) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores ({approx}10{sup 21} W Hz{sup -1}) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whosemore » VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity.« less

The Lick AGN Monitoring Project 2016: Extending Reverberation Mapping to Higher Luminosity AGNs

NASA Astrophysics Data System (ADS)

U, Vivian; LAMP2016 Collaboration

2017-01-01

The technique of reverberation mapping has been used to estimate virial black hole masses and, more fundamentally, to probe the broad line region structure in Seyfert I galaxies. Efforts from the previous Lick AGN Monitoring Project (LAMP) campaigns and other studies to date have culminated in a large sample of reverberation mapped AGNs and measurements of their black hole masses, which in turn enabled major improvement to various AGN scaling relations. However, the high-luminosity end of such relations remains poorly constrained; this is because of observational challenges presented by the weaker continuum flux variations and longer time dilation in these sources. To this end, we have initiated a new LAMP2016 campaign to target AGNs with luminosities of 10^44 erg/s, with predicted H-beta lags of ~20 - 60 days or black hole masses of 10^7 - 10^8.5 Msun. Designed to monitor ~20 AGNs biweekly from Spring 2016 through Winter 2017 with the Kast spectrograph on the 3-m Shane Telescope at Lick Observatory, we aim to probe luminosity-dependent trends in broad line region structure and dynamics, improve calibrations for single-epoch estimates of high-redshift quasar black hole masses, and test photoionization models for the radially-stratified structure of the broad line region. In this talk, I will present the overview and scope of LAMP2016 and show preliminary results from our ongoing campaign.

Simultaneous Chandra and VLA Observations of the Transitional Millisecond Pulsar PSR J1023+0038: Anti-correlated X-Ray and Radio Variability

NASA Astrophysics Data System (ADS)

Bogdanov, Slavko; Deller, Adam T.; Miller-Jones, James C. A.; Archibald, Anne M.; Hessels, Jason W. T.; Jaodand, Amruta; Patruno, Alessandro; Bassa, Cees; D’Angelo, Caroline

2018-03-01

We present coordinated Chandra X-ray Observatory and Karl G. Jansky Very Large Array observations of the transitional millisecond pulsar PSR J1023+0038 in its low-luminosity accreting state. The unprecedented five hours of strictly simultaneous X-ray and radio continuum coverage for the first time unambiguously show a highly reproducible, anti-correlated variability pattern. The characteristic switches from the X-ray high mode into a low mode are always accompanied by a radio brightening with a duration that closely matches the X-ray low mode interval. This behavior cannot be explained by a canonical inflow/outflow accretion model where the radiated emission and the jet luminosity are powered by, and positively correlated with, the available accretion energy. We interpret this phenomenology as alternating episodes of low-level accretion onto the neutron star during the X-ray high mode that are interrupted by rapid ejections of plasma by the active rotation-powered pulsar, possibly initiated by a reconfiguration of the pulsar magnetosphere, that cause a transition to a less X-ray luminous mode. The observed anti-correlation between radio and X-ray luminosity has an additional consequence: transitional MSPs can make excursions into a region of the radio/X-ray luminosity plane previously thought to be occupied solely by black hole X-ray binary sources. This complicates the use of this luminosity relation for identifying candidate black holes, suggesting the need for additional discriminants when attempting to establish the true nature of the accretor.

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

NASA Astrophysics Data System (ADS)

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

2018-01-01

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

Implications of the Observed Ultraluminous X-Ray Source Luminosity Function

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Tennant, Allyn; Soria, Roberto; Yukita, Mihoko

2012-01-01

We present the X-ray luminosity function (XLF) of ultraluminous X-ray (ULX) sources with 0.3-10.0 keV luminosities in excess of 10(sup 39) erg/s in a complete sample of nearby galaxies. The XLF shows a break or cut-off at high luminosities that deviates from its pure power law distribution at lower luminosities. The cut-off is at roughly the Eddington luminosity for a 90-140 solar mass accretor. We examine the effects on the observed XLF of sample biases, of small-number statistics (at the high luminosity end) and of measurement uncertainties. We consider the physical implications of the shape and normalization of the XLF. The XLF is also compared and contrasted to results of other recent surveys.

Physical Properties of Spectroscopically Confirmed Galaxies at z >= 6. I. Basic Characteristics of the Rest-frame UV Continuum and Lyα Emission

NASA Astrophysics Data System (ADS)

Jiang, Linhua; Egami, Eiichi; Mechtley, Matthew; Fan, Xiaohui; Cohen, Seth H.; Windhorst, Rogier A.; Davé, Romeel; Finlator, Kristian; Kashikawa, Nobunari; Ouchi, Masami; Shimasaku, Kazuhiro

2013-08-01

We present deep Hubble Space Telescope near-IR and Spitzer mid-IR observations of a large sample of spectroscopically confirmed galaxies at z >= 6. The sample consists of 51 Lyα emitters (LAEs) at z ~= 5.7, 6.5, and 7.0, and 16 Lyman break galaxies (LBGs) at 5.9 <= z <= 6.5. The near-IR images were mostly obtained with WFC3 in the F125W and F160W bands, and the mid-IR images were obtained with IRAC in the 3.6 μm and 4.5 μm bands. Our galaxies also have deep optical imaging data from Subaru Suprime-Cam. We utilize the multi-band data and secure redshifts to derive their rest-frame UV properties. These galaxies have steep UV-continuum slopes roughly between β ~= -1.5 and -3.5, with an average value of β ~= -2.3, slightly steeper than the slopes of LBGs in previous studies. The slope shows little dependence on UV-continuum luminosity except for a few of the brightest galaxies. We find a statistically significant excess of galaxies with slopes around β ~= -3, suggesting the existence of very young stellar populations with extremely low metallicity and dust content. Our galaxies have moderately strong rest-frame Lyα equivalent width (EW) in a range of ~10 to ~200 Å. The star formation rates are also moderate, from a few to a few tens of solar masses per year. The LAEs and LBGs in this sample share many common properties, implying that LAEs represent a subset of LBGs with strong Lyα emission. Finally, the comparison of the UV luminosity functions between LAEs and LBGs suggests that there exists a substantial population of faint galaxies with weak Lyα emission (EW < 20 Å) that could be the dominant contribution to the total ionizing flux at z >= 6. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based in part on data collected at Subaru Telescope and obtained from SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan.

X-ray properties of quasars

NASA Technical Reports Server (NTRS)

Ku, W. H.-M.; Helfand, D. J.; Lucy, L. B.

1980-01-01

The X-ray properties of 111 catalogued quasars have been examined with the imaging proportional counter on board the Einstein Observatory. Thirty-five of the objects, of redshift between 0.064 and 3.53, were detected as X-ray sources. The 0.5-4.5-keV X-ray properties of these quasars are correlated with their optical and radio continuum properties and with their redshifts and variability characteristics. The X-ray luminosity of quasars tends to be highest for those objects which are bright in the optical and radio regimes and which exhibit optically violent variability. These observations suggest that quasars should be divided into two classes on the basis of radio luminosities, spectra, evolution and underlying morphology and that quasars can make up a significant portion of the diffuse soft X-ray background only if the slope of the optical quasar log N-log S relation is steeper than 2 to m sub b of about 21.5.

A New Compton-thick AGN in our Cosmic Backyard: Unveiling the Buried Nucleus in NGC 1448 with NuSTAR

NASA Astrophysics Data System (ADS)

Annuar, A.; Alexander, D. M.; Gandhi, P.; Lansbury, G. B.; Asmus, D.; Ballantyne, D. R.; Bauer, F. E.; Boggs, S. E.; Boorman, P. G.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Craig, W. W.; Farrah, D.; Goulding, A. D.; Hailey, C. J.; Harrison, F. A.; Koss, M. J.; LaMassa, S. M.; Murray, S. S.; Ricci, C.; Rosario, D. J.; Stanley, F.; Stern, D.; Zhang, W.

2017-02-01

NGC 1448 is one of the nearest luminous galaxies (L 8-1000μm > 109 L ⊙) to ours (z = 0.00390), and yet the active galactic nucleus (AGN) it hosts was only recently discovered, in 2009. In this paper, we present an analysis of the nuclear source across three wavebands: mid-infrared (MIR) continuum, optical, and X-rays. We observed the source with the Nuclear Spectroscopic Telescope Array (NuSTAR), and combined these data with archival Chandra data to perform broadband X-ray spectral fitting (≈0.5-40 keV) of the AGN for the first time. Our X-ray spectral analysis reveals that the AGN is buried under a Compton-thick (CT) column of obscuring gas along our line of sight, with a column density of N H(los) ≳ 2.5 × 1024 cm-2. The best-fitting torus models measured an intrinsic 2-10 keV luminosity of L {}2-10,{int} = (3.5-7.6) × 1040 erg s-1, making NGC 1448 one of the lowest luminosity CTAGNs known. In addition to the NuSTAR observation, we also performed optical spectroscopy for the nucleus in this edge-on galaxy using the European Southern Observatory New Technology Telescope. We re-classify the optical nuclear spectrum as a Seyfert on the basis of the Baldwin-Philips-Terlevich diagnostic diagrams, thus identifying the AGN at optical wavelengths for the first time. We also present high spatial resolution MIR observations of NGC 1448 with Gemini/T-ReCS, in which a compact nucleus is clearly detected. The absorption-corrected 2-10 keV luminosity measured from our X-ray spectral analysis agrees with that predicted from the optical [O III]λ5007 Å emission line and the MIR 12 μm continuum, further supporting the CT nature of the AGN.

The ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] Line and Dust Emission in 6

NASA Astrophysics Data System (ADS)

Aravena, M.; Decarli, R.; Walter, F.; Bouwens, R.; Oesch, P. A.; Carilli, C. L.; Bauer, F. E.; Da Cunha, E.; Daddi, E.; Gónzalez-López, J.; Ivison, R. J.; Riechers, D. A.; Smail, I.; Swinbank, A. M.; Weiss, A.; Anguita, T.; Bacon, R.; Bell, E.; Bertoldi, F.; Cortes, P.; Cox, P.; Hodge, J.; Ibar, E.; Inami, H.; Infante, L.; Karim, A.; Magnelli, B.; Ota, K.; Popping, G.; van der Werf, P.; Wagg, J.; Fudamoto, Y.

2016-12-01

We present a search for [C II] line and dust continuum emission from optical dropout galaxies at z > 6 using ASPECS, our Atacama Large Millimeter submillimeter Array Spectroscopic Survey in the Hubble Ultra-deep Field (UDF). Our observations, which cover the frequency range of 212-272 GHz, encompass approximately the range of 6 < z < 8 for [C II] line emission and reach a limiting luminosity of L [C II] ˜ (1.6-2.5) × 108 L ⊙. We identify 14 [C II] line emitting candidates in this redshift range with significances >4.5σ, two of which correspond to blind detections with no optical counterparts. At this significance level, our statistical analysis shows that about 60% of our candidates are expected to be spurious. For one of our blindly selected [C II] line candidates, we tentatively detect the CO(6-5) line in our parallel 3 mm line scan. None of the line candidates are individually detected in the 1.2 mm continuum. A stack of all [C II] candidates results in a tentative detection with S 1.2 mm = 14 ± 5 μJy. This implies a dust-obscured star-formation rate (SFR) of (3 ± 1) M ⊙ yr-1. We find that the two highest-SFR objects have candidate [C II] lines with luminosities that are consistent with the low-redshift L [C II] versus SFR relation. The other candidates have significantly higher [C II] luminosities than expected from their UV-based SFR. At the current sensitivity, it is unclear whether the majority of these sources are intrinsically bright [C II] emitters, or spurious sources. If only one of our line candidates was real (a scenario greatly favored by our statistical analysis), we find a source density for [C II] emitters at 6 < z < 8 that is significantly higher than predicted by current models and some extrapolations from galaxies in the local universe.

X-RAY ABSORPTION, NUCLEAR INFRARED EMISSION, AND DUST COVERING FACTORS OF AGNs: TESTING UNIFICATION SCHEMES

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

Mateos, S.; Carrera, F. J.; Alonso-Herrero, A.

2016-03-10

We present the distributions of the geometrical covering factors of the dusty tori (f{sub 2}) of active galactic nuclei (AGNs) using an X-ray selected complete sample of 227 AGNs drawn from the Bright Ultra-hard XMM-Newton Survey. The AGNs have z from 0.05 to 1.7, 2–10 keV luminosities between 10{sup 42} and 10{sup 46} erg s{sup −1}, and Compton-thin X-ray absorption. Employing data from UKIDSS, 2MASS, and the Wide-field Infrared Survey Explorer in a previous work, we determined the rest-frame 1–20 μm continuum emission from the torus, which we model here with the clumpy torus models of Nenkova et al. Opticallymore » classified type 1 and type 2 AGNs are intrinsically different, with type 2 AGNs having, on average, tori with higher f{sub 2} than type 1 AGNs. Nevertheless, ∼20% of type 1 AGNs have tori with large covering factors, while ∼23%–28% of type 2 AGNs have tori with small covering factors. Low f{sub 2} are preferred at high AGN luminosities, as postulated by simple receding torus models, although for type 2 AGNs the effect is certainly small. f{sub 2} increases with the X-ray column density, which implies that dust extinction and X-ray absorption take place in material that share an overall geometry and most likely belong to the same structure, the putative torus. Based on our results, the viewing angle, AGN luminosity, and also f{sub 2} determine the optical appearance of an AGN and control the shape of the rest-frame ∼1–20 μm nuclear continuum emission. Thus, the torus geometrical covering factor is a key ingredient of unification schemes.« less

Looking at A 0535+26 at low luminosities with NuSTAR

NASA Astrophysics Data System (ADS)

Ballhausen, Ralf; Pottschmidt, Katja; Fürst, Felix; Wilms, Jörn; Tomsick, John A.; Schwarm, Fritz-Walter; Stern, Daniel; Kretschmar, Peter; Caballero, Isabel; Harrison, Fiona A.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles J.; Zhang, William W.

2017-12-01

We report on two NuSTAR observations of the high-mass X-ray binary A 0535+26 taken toward the end of its normal 2015 outburst at very low 3-50 keV luminosities of 1.4 × 1036 erg s-1 and 5 × 1035 erg s-1, which are complemented by nine Swift observations. The data clearly confirm indications seen in earlier data that the source's spectral shape softens as it becomes fainter. The smooth exponential rollover at high energies seen in the first observation evolves to a much more abrupt steepening of the spectrum at 20-30 keV. The continuum evolution can be nicely described with emission from a magnetized accretion column, modeled using the compmag model modified by an additional Gaussian emission component for the fainter observation. Between the two observations, the optical depth changes from 0.75 ± 0.04 to , the electron temperature remains constant, and there is an indication that the column decreases in radius. Since the energy-resolved pulse profiles remain virtually unchanged in shape between the two observations, the emission properties of the accretion column reflect the same accretion regime. This conclusion is also confirmed by our result that the energy of the cyclotron resonant scattering feature (CRSF) at 45 keV is independent of the luminosity, implying that the magnetic field in the region in which the observed radiation is produced is the same in both observations. Finally, we also constrain the evolution of the continuum parameters with the rotational phase of the neutron star. The width of the CRSF could only be constrained for the brighter observation. Based on Monte Carlo simulations of CRSF formation in single accretion columns, its pulse phase dependence supports a simplified fan beam emission pattern. The evolution of the CRSF width is very similar to that of the CRSF depth, which is, however, in disagreement with expectations.

The Evolution of Globular Cluster Systems In Early-Type Galaxies

NASA Astrophysics Data System (ADS)

Grillmair, Carl

1999-07-01

We will measure structural parameters {core radii and concentrations} of globular clusters in three early-type galaxies using deep, four-point dithered observations. We have chosen globular cluster systems which have young, medium-age and old cluster populations, as indicated by cluster colors and luminosities. Our primary goal is to test the hypothesis that globular cluster luminosity functions evolve towards a ``universal'' form. Previous observations have shown that young cluster systems have exponential luminosity functions rather than the characteristic log-normal luminosity function of old cluster systems. We will test to see whether such young system exhibits a wider range of structural parameters than an old systems, and whether and at what rate plausible disruption mechanisms will cause the luminosity function to evolve towards a log-normal form. A simple observational comparison of structural parameters between different age cluster populations and between diff er ent sub-populations within the same galaxy will also provide clues concerning both the formation and destruction mechanisms of star clusters, the distinction between open and globular clusters, and the advisability of using globular cluster luminosity functions as distance indicators.

Luminosity function and cosmological evolution of X-ray selected quasars

NASA Technical Reports Server (NTRS)

Maccacaro, T.; Gioia, I. M.

1983-01-01

The preliminary analysis of a complete sample of 55 X-ray sources is presented as part of the Medium Sensitivity Survey of the Einstein Observatory. A pure luminosity evolutionary law is derived in order to determine the uniform distribution of the sources and the rates of evolution for Active Galactic Nuclei (AGNs) observed by X-ray and optical techniques are compared. A nonparametric representation of the luminosity function is fitted to the observational data. On the basis of the reduced data, it is determined that: (1) AGNs evolve cosmologically; (2) less evolution is required to explain the X-ray data than the optical data; (3) the high-luminosity portion of the X-ray luminosity can be described by a power-law with a slope of gamma = 3.6; and (4) the X-ray luminosity function flattens at low luminosities. Some of the implications of the results for conventional theoretical models of the evolution of quasars and Seyfert galaxies are discussed.

VizieR Online Data Catalog: XXL Survey: First results (Pierre+, 2016)

NASA Astrophysics Data System (ADS)

Pierre, M.; Pacaud, F.; Adami, C.; Alis, S.; Altieri, B.; Baran, B.; Benoist, C.; Birkinshaw, M.; Bongiorno, A.; Bremer, M. N.; Brusa, M.; Butler, A.; Ciliegi, P.; Chiappetti, L.; Clerc, N.; Corasaniti, P. S.; Coupon, J.; De Breuck, C.; Democles, J.; Desai, S.; Delhaize, J.; Devriendt, J.; Dubois, Y.; Eckert, D.; Elyiv, A.; Ettori, S.; Evrard, A.; Faccioli, L.; Farahi, A.; Ferrari, C.; Finet, F.; Fotopoulou, S.; Fourmanoit, N.; Gandhi, P.; Gastaldello, F.; Gastaud, R.; Georgantopoulos, I.; Giles, P.; Guennou, L.; Guglielmo, V.; Horellou, C.; Husband, K.; Huynh, M.; Iovino, A.; Kilbinger, M.; Koulouridis, E.; Lavoie, S.; Le Brun, A. M. C.; Lefevre, J. P.; Lidman, C.; Lieu, M.; Lin, C. A.; Mantz, A.; Maughan, B. J.; Maurogordato, S.; McCarthy, I. G.; McGee, S.; Melin, J. B.; Melnyk, O.; Menanteau, F.; Novak, M.; Paltani, S.; Plionis, M.; Poggianti, B. M.; Pomarede, D.; Pompei, E.; Ponman, T. J.; Ramos-Ceja, M. E.; Ranalli, P.; Rapetti, D.; Raychaudury, S.; Reiprich, T. H.; Rottgering, H.; Rozo, E.; Ryko, E.; Sadibekova, T.; Santos, J.; Sauvageot, J. L.; Schimd, C.; Sereno, M.; Smith, G. P.; Smolcic, V.; Snowden, S.; Spergel, D.; Stanford, S.; Surdej, J.; Valageas, P.; Valotti, A.; Valtchanov, I.; Vignali, C.; Willis, J.; Ziparo, F.

2016-03-01

Paper I. Scientific motivations - XMM-Newton observing plan. Follow-up observations and simulation programme. The table xxlpoint.dat is a list of all XMM survey-type observations (<=AO-10) in the XXL fields, providing the match between the internal naming and the ESA XXM log,the coordinates and useful exposure times of the XMM pointings, their quality and ancillary information. Paper II. The bright cluster sample: catalogue and luminosity function. Paper III. Luminosity-temperature relation of the bright cluster sample. Paper IV. Mass-temperature relation of the bright cluster sample. This article presents the XXL bright cluster sample, a subsample of 100 galaxy clusters selected from the full XXL catalogue by setting a lower limit of 3*10-14erg/cm2/s on the source flux within a 1' aperture. The selection function was estimated using a mixture of Monte Carlo simulations and analytical recipes that closely reproduce the source selection process. An extensive spectroscopic follow-up provided redshifts for 97 of the 100 clusters. We derived accurate X-ray parameters for all the sources. Scaling relations were self-consistently derived from the same sample in other publications of the series. On this basis, we study the number density, luminosity function, and spatial distribution of the sample. The bright cluster sample consists of systems with masses between M500=7*10+14 and 3*10+14Mȯ, mostly located between z=0.1 and 0.5. The observed sky density of clusters is slightly below the predictions from the WMAP9 model, and significantly below the prediction from the Planck 2015 cosmology. In general, within the current uncertainties of the cluster mass calibration, models with higher values of σ8 and/or ΩM appear more difficult to accommodate. We provide tight constraints on the cluster differential luminosity function and find no hint of evolution out to z~1. We also find strong evidence for the presence of large-scale structures in the XXL bright cluster sample and identify five new superclusters. We provide the XXL-100-GC catalogue (xxl100gc.dat), the master catalogue of the 100 brightest galaxy clusters from the XXL Survey. This catalogue summarizes all the information published on this sample by the XXL collaboration, which were initially distributed over several articles. It contains the sources positions, redshifts, fluxes and mass estimates published in Appendix D of paper II, combined with luminosities and temperatures from Table 1 of paper III, as well as gas masses from Table A.1 of paper XIII. Paper VI. The 1000 brightest X-ray point sources. We provide the XXL1000AGN catalogue (xxl1000a.dat), the first catalogue release of the XXL point source catalog, detected in the 2-10keV energy band. The catalogue contains the 1000 brightest sources, at the flux limit of F[2-10 keV]=4.8 10-14erg/s/cm2. We provide derived X-ray spectral parameters, and counterpart properties including four optical magnitudes, photometric and spectroscopic redshift estimates. We also provide the best photometric redshift class based on machine learning classification and the probability for a source to be a star or a photometric redshift outlier. Paper IX. Optical overdensity and radio continuum analysis of a supercluster at z=0.43. The table xxl_vla.dat contains the full source catalogue of all 155 radio sources detected with S/N>=6 in the Very Large Array 3GHz continuum survey of the XXL-North field. The observations covered the 0.7x0.7 square degrees subarea of the 25 square degree XXL-North field. The radio data has an angular resolution of 3.2x1.9 square arcsec and a mean rms of 20uJy per beam. There are 25 resolved sources, of which 8 are multicomponent objects. Paper XI. ATCA 2.1 GHz continuum observations. The table xxl_atca.dat contains the full source catalogue of all 1389 radio sources detected with S/N>=5 in the Australia Telescope Compact Array 2.1GHz continuum pilot survey of the XXL-South field. The observations covered the inner 6.5 square degrees of the 25 square degree XXL-South field. The radio data has an angular resolution of 4.7x4.2 square arcsec and a median rms of 50uJy per beam. There are 305 resolved sources, of which 77 are multicomponent objects. The table contains various observed parameters of the radio sources, such as position, peak flux density and signal-to-noise ratio. Paper XIV. AAOmega redshifts for the southern XXL field. We present a catalogue (xxlaaoz.dat) containing the redshifts of 3660 X-ray selected targets in the XXL southern field. The redshifts were obtained with the AAOmega spectrograph and 2dF fibre positioner on the Anglo-Australian Telescope. The catalogue contains 1515 broad line AGN, 528 stars, and redshifts for 41 out of the 49 brightest X-ray selected clusters in the XXL southern field. Paper XV. Evidence for dry merger driven BCG growth in XXL-100-GC X-ray clusters Given the availability of good quality multiband photometry together with photometric and spectroscopic redshifts to z<1, a simple set of criteria can be used to identify BCGs. For the present work, we define a BCG as: - the brightest galaxy in z-band, - within 0.5xr500 of the cluster X-ray centroid, - with a redshift that is consistent with that of the cluster as determined from all the redshifts available around the X-ray centroid. Our final sample (xxl100bc.dat) consists of 85 clusters, 45 of which are in the Northern field and 40 in the Southern field. (9 data files).

A VLA radio-continuum survey of a sample of confirmed and marginal barium stars

NASA Technical Reports Server (NTRS)

Drake, Stephen A.; Simon, Theodore; Linsky, Jeffrey L.

1987-01-01

Results are reported from a 6-cm VLA survey of five confirmed Ba II stars and eight mild Ba II stars, undertaken to search for evidence of gyrosynchrotron emission or thermal emission from the primary star's wind that is enhanced or photoionized by a white dwarf companion. Of these 13 stars, only Beta UMi was detected as a possible radio source at a flux level of 0.11 mJy (3sigma). The 6-cm radio luminosities (L6) of the other stars are as small as log L6 less than or equal to 14.0 and are an order of magnitude or more lower than the average levels found in RS CVn systems, but are consistent with the L6 upper limits previously found for stars of spectral type similar to the Ba II stars and normal elemental abundances. The upper limit to the radio luminosity for the possible mild Ba II star 56 Peg, when combined with its previously known X-ray luminosity, may provide useful constraints on the various models that have been proposed for this interesting object, once its orbital period is known.

What powers Hyperluminous infrared galaxies at z˜1-2?

NASA Astrophysics Data System (ADS)

Symeonidis, M.; Page, M. J.

2018-06-01

We investigate what powers hyperluminous infrared galaxies (HyLIRGs; LIR, 8-1000μm > 1013 L⊙) at z˜1-2, by examining the behaviour of the infrared AGN luminosity function in relation to the infrared galaxy luminosity function. The former corresponds to emission from AGN-heated dust only, whereas the latter includes emission from dust heated by stars and AGN. Our results show that the two luminosity functions are substantially different below 1013 L⊙ but converge in the HyLIRG regime. We find that the fraction of AGN dominated sources increases with total infrared luminosity and at L_IR>10^{13.5} L_{⊙} AGN can account for the entire infrared emission. We conclude that the bright end of the 1 < z < 2 infrared galaxy luminosity function is shaped by AGN rather than star-forming galaxies.

Axions and the luminosity function of white dwarfs. The thin and thick disks, and the halo

NASA Astrophysics Data System (ADS)

Isern, J.; García-Berro, E.; Torres, S.; Cojocaru, R.; Catalán, S.

2018-05-01

The evolution of white dwarfs is a simple gravothermal process of cooling. Since the shape of their luminosity function is sensitive to the characteristic cooling time, it is possible to use its slope to test the existence of additional sources or sinks of energy, such as those predicted by alternative physical theories. The aim of this paper is to study if the changes in the slope of the white dwarf luminosity function around bolometric magnitudes ranging from 8 to 10 and previously attributed to axion emission are, effectively, a consequence of the existence of axions and not an artifact introduced by the star formation rate. We compute theoretical luminosity functions of the thin and thick disk, and of the stellar halo including axion emission and we compare them with the existing observed luminosity functions. Since these stellar populations have different star formation histories, the slope change should be present in all of them at the same place if it is due to axions or any other intrinsic cooling mechanism. The signature of an unexpected cooling seems to be present in the luminosity functions of the thin and thick disks, as well as in the halo luminosity function. This additional cooling is compatible with axion emission, thus supporting to the idea that DFSZ axions, with a mass in the range of 4 to 10 meV, could exist. If this were the case, these axions could be detected by the future solar axioscope IAXO.

An Accreting Protoplanet: Confirmation and Characterization of LkCa15b

NASA Astrophysics Data System (ADS)

Follette, Katherine; Close, Laird; Males, Jared; Macintosh, Bruce; Sallum, Stephanie; Eisner, Josh; Kratter, Kaitlin M.; Morzinski, Katie; Hinz, Phil; Weinberger, Alycia; Rodigas, Timothy J.; Skemer, Andrew; Bailey, Vanessa; Vaz, Amali; Defrere, Denis; spalding, eckhart; Tuthill, Peter

2015-12-01

We present a visible light adaptive optics direct imaging detection of a faint point source separated by just 93 milliarcseconds (~15 AU) from the young star LkCa 15. Using Magellan AO's visible light camera in Simultaneous Differential Imaging (SDI) mode, we imaged the star at Hydrogen alpha and in the neighboring continuum as part of the Giant Accreting Protoplanet Survey (GAPplanetS) in November 2015. The continuum images provide a sensitive and simultaneous probe of PSF residuals and instrumental artifacts, allowing us to isolate H-alpha accretion luminosity from the LkCa 15b protoplanet, which lies well inside of the LkCa15 transition disk gap. This detection, combined with a nearly simultaneous near-infrared detection with the Large Binocular Telescope, provides an unprecedented glimpse at a planetary system during epoch of planet formation. [Nature result in press. Please embargo until released

Host Galaxies of Luminous Type 2 Quasars at z ~ 0.5

NASA Astrophysics Data System (ADS)

Liu, Xin; Zakamska, Nadia L.; Greene, Jenny E.; Strauss, Michael A.; Krolik, Julian H.; Heckman, Timothy M.

2009-09-01

We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at redshifts z ~ 0.5, drawn from the Sloan Digital Sky Survey type 2 quasar sample. Our targets were selected to have high intrinsic luminosities (MV < -26 mag) as indicated by the [O III] λ5007 Å emission-line luminosity (L [O III]). Our sample has a median black hole mass of ~108.8 M sun inferred assuming the local M BH-σ* relation and a median Eddington ratio of ~0.7, using stellar velocity dispersions σ* measured from the G band. We estimate the contamination of the stellar continuum from scattered quasar light based on the strength of broad Hβ, and provide an empirical calibration of the contamination as a function of L [O III]; the scattered-light fraction is ~30% of L 5100 for objects with L [O III] = 109.5 L sun. Population synthesis indicates that young poststarburst populations (<0.1 Gyr) are prevalent in luminous type 2 quasars, in addition to a relatively old population (>1 Gyr) which dominates the stellar mass. Broad emission complexes around He II λ4686 Å with luminosities up to 108.3 L sun are unambiguously detected in three out of the nine targets, indicative of Wolf-Rayet (WR) populations. Population synthesis shows that ~5 Myr poststarburst populations contribute substantially to the luminosities (>50% of L 5100) of all three objects with WR detections. We find two objects with double cores and four with close companions. Our results may suggest that luminous type 2 quasars trace an early stage of galaxy interaction, perhaps responsible for both the quasar and the starburst activity. Based, in part, on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

UV-CONTINUUM SLOPES AT z {approx} 4-7 FROM THE HUDF09+ERS+CANDELS OBSERVATIONS: DISCOVERY OF A WELL-DEFINED UV COLOR-MAGNITUDE RELATIONSHIP FOR z {>=} 4 STAR-FORMING GALAXIES

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

Bouwens, R. J.; Franx, M.; Labbe, I.

2012-08-01

Ultra-deep Advanced Camera for Surveys (ACS) and WFC3/IR HUDF+HUDF09 data, along with the wide-area GOODS+ERS+CANDELS data over the CDF-S GOODS field, are used to measure UV colors, expressed as the UV-continuum slope {beta}, of star-forming galaxies over a wide range of luminosity (0.1L*{sub z=3} to 2L*{sub z=3}) at high redshift (z {approx} 7 to z {approx} 4). {beta} is measured using all ACS and WFC3/IR passbands uncontaminated by Ly{alpha} and spectral breaks. Extensive tests show that our {beta} measurements are only subject to minimal biases. Using a different selection procedure, Dunlop et al. recently found large biases in their {beta}more » measurements. To reconcile these different results, we simulated both approaches and found that {beta} measurements for faint sources are subject to large biases if the same passbands are used both to select the sources and to measure {beta}. High-redshift galaxies show a well-defined rest-frame UV color-magnitude (CM) relationship that becomes systematically bluer toward fainter UV luminosities. No evolution is seen in the slope of the UV CM relationship in the first 1.5 Gyr, though there is a small evolution in the zero point to redder colors from z {approx} 7 to z {approx} 4. This suggests that galaxies are evolving along a well-defined sequence in the L{sub UV}-color ({beta}) plane (a 'star-forming sequence'?). Dust appears to be the principal factor driving changes in the UV color {beta} with luminosity. These new larger {beta} samples lead to improved dust extinction estimates at z {approx} 4-7 and confirm that the extinction is essentially zero at low luminosities and high redshifts. Inclusion of the new dust extinction results leads to (1) excellent agreement between the star formation rate (SFR) density at z {approx} 4-8 and that inferred from the stellar mass density; and (2) to higher specific star formation rates (SSFRs) at z {approx}> 4, suggesting that the SSFR may evolve modestly (by factors of {approx}2) from z {approx} 4-7 to z {approx} 2.« less

FUSE Observations of the Dwarf Seyfert Nucleus of NGC 4395

NASA Astrophysics Data System (ADS)

Kraemer, Steven B.

The Sd IV dwarf galaxy NGC 4395 is the nearest (d approx. 2.6 Mpc) and least luminous (L_bol < 1041 ergs s-1) example of a Seyfert 1 galaxy. This unique object possesses all of the classic Seyfert 1 properties in miniature, including broad and narrow emission lines, a non-stellar continuum, and highly variable X-ray emission, presumably powered by a small (105 M_sun) black hole. Furthermore, there is evidence for blue-shifted, intrinsic absorption lines in the UV (C IV lambda lambda 1548.2, 1550.8), while X-ray spectra show the presence of bound-free edges from O VII and O VIII and evidence for even more highly ionized gas. The UV absorption could arise within the X-ray absorbers or, alternatively, within the emission-line gas, which we have determined to have a high covering factor. The unique capabilities of FUSE provide the means with which to constrain the ionization state, column density, and covering factor of the absorbers and, hence, distinguish between these two possibilities. By extending our investigation of intrinsic absorption to the low luminosity extreme of the Seyfert population, we will obtain crucial insight into the effects of luminosity, global covering factor, and central black hole mass on the intrinsic absorbers. A second goal of this project is to constrain the spectral energy distribution of the non-stellar continuum radiation, which may be unique in this object as a consequence of its small black hole mass.

Applying a physical continuum model to describe the broadband X-ray spectra of accreting pulsars at high luminosity

NASA Astrophysics Data System (ADS)

Pottschmidt, Katja; Hemphill, Paul B.; Wolff, Michael T.; Cheatham, Diana M.; Iwakiri, Wataru; Gottlieb, Amy M.; Falkner, Sebastian; Ballhausen, Ralf; Fuerst, Felix; Kuehnel, Matthias; Ferrigno, Carlo; Becker, Peter A.; Wood, Kent S.; Wilms, Joern

2018-01-01

A new window for better understanding the accretion onto strongly magnetized neutron stars in X-ray binaries is opening. In these systems the accreted material follows the magnetic field lines as it approaches the neutron star, forming accretion columns above the magnetic poles. The plasma falls toward the neutron star surface at near-relativistic speeds, losing energy by emitting X-rays. The X-ray spectral continua are commonly described using phenomenological models, i.e., power laws with different types of curved cut-offs at higher energies. Here we consider high luminosity pulsars. In these systems the mass transfer rate is high enough that the accreting plasma is thought to be decelerated in a radiation-dominated radiative shock in the accretion columns. While the theory of the emission from such shocks had already been developed by 2007, a model for direct comparison with X-ray continuum spectra in xspec or isis has only recently become available. Characteristic parameters of this model are the accretion column radius and the plasma temperature, among others. Here we analyze the broadband X-ray spectra of the accreting pulsars Centaurus X-3 and 4U 1626-67 obtained with NuSTAR. We present results from traditional empirical modeling as well as successfully apply the radiation-dominated radiative shock model. We also take the opportunity to compare to similar recent analyses of both sources using these and other observations.

The spectral energy distribution of powerful starburst galaxies - I. Modelling the radio continuum

NASA Astrophysics Data System (ADS)

Galvin, T. J.; Seymour, N.; Marvil, J.; Filipović, M. D.; Tothill, N. F. H.; McDermid, R. M.; Hurley-Walker, N.; Hancock, P. J.; Callingham, J. R.; Cook, R. H.; Norris, R. P.; Bell, M. E.; Dwarakanath, K. S.; For, B.; Gaensler, B. M.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

2018-02-01

We have acquired radio-continuum data between 70 MHz and 48 GHz for a sample of 19 southern starburst galaxies at moderate redshifts (0.067 < z < 0.227) with the aim of separating synchrotron and free-free emission components. Using a Bayesian framework, we find the radio continuum is rarely characterized well by a single power law, instead often exhibiting low-frequency turnovers below 500 MHz, steepening at mid to high frequencies, and a flattening at high frequencies where free-free emission begins to dominate over the synchrotron emission. These higher order curvature components may be attributed to free-free absorption across multiple regions of star formation with varying optical depths. The decomposed synchrotron and free-free emission components in our sample of galaxies form strong correlations with the total-infrared bolometric luminosities. Finally, we find that without accounting for free-free absorption with turnovers between 90 and 500 MHz the radio continuum at low frequency (ν < 200 MHz) could be overestimated by upwards of a factor of 12 if a simple power-law extrapolation is used from higher frequencies. The mean synchrotron spectral index of our sample is constrained to be α = -1.06, which is steeper than the canonical value of -0.8 for normal galaxies. We suggest this may be caused by an intrinsically steeper cosmic ray distribution.

Luminosity and surface brightness distribution of K-band galaxies from the UKIDSS Large Area Survey

NASA Astrophysics Data System (ADS)

Smith, Anthony J.; Loveday, Jon; Cross, Nicholas J. G.

2009-08-01

We present luminosity and surface-brightness distributions of 40111 galaxies with K-band photometry from the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS), Data Release 3 and optical photometry from Data Release 5 of the Sloan Digital Sky Survey (SDSS). Various features and limitations of the new UKIDSS data are examined, such as a problem affecting Petrosian magnitudes of extended sources. Selection limits in K- and r-band magnitude, K-band surface brightness and K-band radius are included explicitly in the 1/Vmax estimate of the space density and luminosity function. The bivariate brightness distribution in K-band absolute magnitude and surface brightness is presented and found to display a clear luminosity-surface brightness correlation that flattens at high luminosity and broadens at low luminosity, consistent with similar analyses at optical wavelengths. Best-fitting Schechter function parameters for the K-band luminosity function are found to be M* - 5 logh = -23.19 +/- 0.04,α = -0.81 +/- 0.04 and φ* = (0.0166 +/- 0.0008)h3Mpc-3, although the Schechter function provides a poor fit to the data at high and low luminosity, while the luminosity density in the K band is found to be j = (6.305 +/- 0.067) × 108LsolarhMpc-3. However, we caution that there are various known sources of incompleteness and uncertainty in our results. Using mass-to-light ratios determined from the optical colours, we estimate the stellar mass function, finding good agreement with previous results. Possible improvements are discussed that could be implemented when extending this analysis to the full LAS.

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2016-04-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of AGN evolution stretching back to z˜5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function - all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is demonstrated at z ≈0 and 0.9, and clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z. The results support the idea that there are at least two different modes of AGN triggering: one, at high luminosity, that only occurs in high mass, highly biased haloes, and one that can occur over a wide range of halo masses and leads to luminosities that are correlated with halo mass. This latter mode dominates at z<0.9. The CLFs for Type 2 and Type 1 AGNs are also constrained at z ≈0, and we find evidence that unobscured quasars are more likely to be found in higher mass halos than obscured quasars. Thus, the AGN unification model seems to fail at quasar luminosities.

THE LICK AGN MONITORING PROJECT 2011: SPECTROSCOPIC CAMPAIGN AND EMISSION-LINE LIGHT CURVES

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

Barth, Aaron J.; Bennert, Vardha N.; Canalizo, Gabriela

2015-04-15

In the Spring of 2011 we carried out a 2.5 month reverberation mapping campaign using the 3 m Shane telescope at Lick Observatory, monitoring 15 low-redshift Seyfert 1 galaxies. This paper describes the observations, reductions and measurements, and data products from the spectroscopic campaign. The reduced spectra were fitted with a multicomponent model in order to isolate the contributions of various continuum and emission-line components. We present light curves of broad emission lines and the active galactic nucleus (AGN) continuum, and measurements of the broad Hβ line widths in mean and rms spectra. For the most highly variable AGNs wemore » also measured broad Hβ line widths and velocity centroids from the nightly spectra. In four AGNs exhibiting the highest variability amplitudes, we detect anticorrelations between broad Hβ width and luminosity, demonstrating that the broad-line region “breathes” on short timescales of days to weeks in response to continuum variations. We also find that broad Hβ velocity centroids can undergo substantial changes in response to continuum variations; in NGC 4593, the broad Hβ velocity shifted by ∼250 km s{sup −1} over a 1 month period. This reverberation-induced velocity shift effect is likely to contribute a significant source of confusion noise to binary black hole searches that use multi-epoch quasar spectroscopy to detect binary orbital motion. We also present results from simulations that examine biases that can occur in measurement of broad-line widths from rms spectra due to the contributions of continuum variations and photon-counting noise.« less

Excavating black hole continuum spectrum: Possible signatures of scalar hairs and of higher dimensions

NASA Astrophysics Data System (ADS)

Banerjee, Indrani; Chakraborty, Sumanta; SenGupta, Soumitra

2017-10-01

Continuum spectrum from black hole accretion disc holds enormous information regarding the strong gravity regime around the black hole and hence about the nature of gravitational interaction in extreme situations. Since in such strong gravity regime the dynamics of gravity should be modified from the Einstein-Hilbert one, its effect should be imprinted on the continuum spectrum originating from the black hole accretion. To explore the effects of these alternative theories on the black hole continuum spectrum in an explicit manner, we have discussed three alternative gravitational models having their origin in three distinct paradigms—(a) higher dimensions, (b) higher curvature gravity, and (c) generalized Horndeski theories. All of them can have signatures sculptured on the black hole continuum spectrum, distinct from the standard general relativistic scenario. Interestingly all these models exhibit black hole solutions with tidal charge parameter which in these alternative gravity scenarios can become negative, in sharp contrast with the Reissner-Nordström black hole. Using the observational data of optical luminosity for eighty Palomer Green quasars we have illustrated that the difference between the theoretical estimates and the observational results gets minimized for negative values of the tidal charge parameter. As a quantitative estimate of this result we concentrate on several error estimators, including reduced χ2 , Nash-Sutcliffe efficiency, index of agreement etc. Remarkably, all of them indicates a negative value of the tidal charge parameter, signaling the possibility of higher dimensions as well as scalar charge at play in those high gravity regimes.

RADIO IMAGING OF THE NGC 2024 FIR 5/6 REGION: A HYPERCOMPACT H II REGION CANDIDATE IN ORION

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

Choi, Minho; Kang, Miju; Lee, Jeong-Eun, E-mail: minho@kasi.re.kr

The NGC 2024 FIR 5/6 region was observed in the 6.9 mm continuum with an angular resolution of about 1.5 arcsec. The 6.9 mm continuum map shows four compact sources, FIR 5w, 5e, 6c, and 6n, as well as an extended structure of the ionization front associated with the optical nebulosity. FIR 6c has a source size of about 0.4 arcsec or 150 AU. The spectral energy distribution (SED) of FIR 6c is peculiar: rising steeply around 6.9 mm and flat around 1 mm. The possibility of a hypercompact H II region is explored. If the millimeter flux of FIRmore » 6c comes from hot ionized gas heated by a single object at the center, the central object may be a B1 star of about 5800 solar luminosities and about 13 solar masses. The 6.9 mm continuum of FIR 6n may be a mixture of free-free emission and dust continuum emission. Archival data show that both FIR 6n and 6c exhibit water maser activity, suggesting the existence of shocked gas around them. The 6.9 mm continuum emission from FIR 5w has a size of about 1.8 arcsec or 760 AU. The SEDs suggest that the 6.9 mm emission of FIR 5w and 5e comes from dust, and the masses of the dense molecular gas are about 0.6 and 0.5 solar masses, respectively.« less

The Lick AGN Monitoring Project 2011: Spectroscopic Campaign and Emission-line Light Curves

NASA Technical Reports Server (NTRS)

Barth, Aaron J.; Bennert, Vardha N.; Canalizo, Gabriela; Filippenko, Alexei V.; Gates, Elinor L.; Greene, Jenny E..; Li, Weidong; Malkan, Matthew A.; Pancoast, Anna; Sand, David J.;

Consistency between the luminosity function of resolved millisecond pulsars and the galactic center excess

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

Ploeg, Harrison; Gordon, Chris; Crocker, Roland

Fermi Large Area Telescope data reveal an excess of GeV gamma rays from the direction of the Galactic Center and bulge. Several explanations have been proposed for this excess including an unresolved population of millisecond pulsars (MSPs) and self-annihilating dark matter. It has been claimed that a key discriminant for or against the MSP explanation can be extracted from the properties of the luminosity function describing this source population. Specifically, is the luminosity function of the putative MSPs in the Galactic Center consistent with that characterizing the resolved MSPs in the Galactic disk? To investigate this we have used amore » Bayesian Markov Chain Monte Carlo to evaluate the posterior distribution of the parameters of the MSP luminosity function describing both resolved MSPs and the Galactic Center excess. At variance with some other claims, our analysis reveals that, within current uncertainties, both data sets can be well fit with the same luminosity function.« less

Space Telescope and Optical Reverberation Mapping Project: Unraveling the Broad Line Region and the Intrinsic Absorption in NGC 5548

NASA Astrophysics Data System (ADS)

Kriss, G.; Storm Team

2015-07-01

The Space Telescope and Optical Reverberation Mapping (STORM) project monitored the Seyfert 1 galaxy NGC 5548 over a six-month period, obtaining 171 far-ultraviolet HST/COS spectra at approximately daily intervals. We find significant correlated variability in the continuum and broad emission lines, with amplitudes ranging from a factor of two in the emission lines to a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He II lagging by ˜ 2.5 days and Ly&alpha,; C IV, and Si IV lagging by 5 to 6 days. The broad UV absorption lines discovered by Kaastra et al. (2014) and associated with the new soft X-ray obscurer are continuously present in the STORM campaign COS spectra. Their strength varies with the degree of soft X-ray obscuration as revealed by the Swift X-ray spectra. The narrow absorption lines associated with the historical warm absorber varied in response to the changing UV flux on a daily basis with lags of 3 to 8 days. The ionization response allows precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

The 5-10 keV AGN luminosity function at 0.01 < z < 4.0

NASA Astrophysics Data System (ADS)

Fotopoulou, S.; Buchner, J.; Georgantopoulos, I.; Hasinger, G.; Salvato, M.; Georgakakis, A.; Cappelluti, N.; Ranalli, P.; Hsu, L. T.; Brusa, M.; Comastri, A.; Miyaji, T.; Nandra, K.; Aird, J.; Paltani, S.

2016-03-01

The active galactic nuclei (AGN) X-ray luminosity function traces actively accreting supermassive black holes and is essential for the study of the properties of the AGN population, black hole evolution, and galaxy-black hole coevolution. Up to now, the AGN luminosity function has been estimated several times in soft (0.5-2 keV) and hard X-rays (2-10 keV). AGN selection in these energy ranges often suffers from identification and redshift incompleteness and, at the same time, photoelectric absorption can obscure a significant amount of the X-ray radiation. We estimate the evolution of the luminosity function in the 5-10 keV band, where we effectively avoid the absorbed part of the spectrum, rendering absorption corrections unnecessary up to NH ~ 1023 cm-2. Our dataset is a compilation of six wide, and deep fields: MAXI, HBSS, XMM-COSMOS, Lockman Hole, XMM-CDFS, AEGIS-XD, Chandra-COSMOS, and Chandra-CDFS. This extensive sample of ~1110 AGN (0.01 < z < 4.0, 41 < log Lx < 46) is 98% redshift complete with 68% spectroscopic redshifts. For sources lacking a spectroscopic redshift estimation we use the probability distribution function of photometric redshift estimation specifically tuned for AGN, and a flat probability distribution function for sources with no redshift information. We use Bayesian analysis to select the best parametric model from simple pure luminosity and pure density evolution to more complicated luminosity and density evolution and luminosity-dependent density evolution (LDDE). We estimate the model parameters that describe best our dataset separately for each survey and for the combined sample. We show that, according to Bayesian model selection, the preferred model for our dataset is the LDDE. Our estimation of the AGN luminosity function does not require any assumption on the AGN absorption and is in good agreement with previous works in the 2-10 keV energy band based on X-ray hardness ratios to model the absorption in AGN up to redshift three. Our sample does not show evidence of a rapid decline of the AGN luminosity function up to redshift four.

A volume-limited ROSAT survey of extreme ultraviolet emission from all nondegenerate stars within 10 parsecs

NASA Technical Reports Server (NTRS)

Wood, Brian E.; Brown, Alexander; Linsky, Jeffrey L.; Kellett, Barry J.; Bromage, Gordon E.; Hodgkin, Simon T.; Pye, John P.

1994-01-01

We report the results of a volume-limited ROSAT Wide Field Camera (WFC) survey of all nondegenerate stars within 10 pc. Of the 220 known star systems within 10 pc, we find that 41 are positive detections in at least one of the two WFC filter bandpasses (S1 and S2), while we consider another 14 to be marginal detections. We compute X-ray luminosities for the WFC detections using Einstein Imaging Proportional Counter (IPC) data, and these IPC luminosities are discussed along with the WFC luminosities throughout the paper for purposes of comparison. Extreme ultraviolet (EUV) luminosity functions are computed for single stars of different spectral types using both S1 and S2 luminosities, and these luminosity functions are compared with X-ray luminosity functions derived by previous authors using IPC data. We also analyze the S1 and S2 luminosity functions of the binary stars within 10 pc. We find that most stars in binary systems do not emit EUV radiation at levels different from those of single stars, but there may be a few EUV-luminous multiple-star systems which emit excess EUV radiation due to some effect of binarity. In general, the ratio of X-ray luminosity to EUV luminosity increases with increasing coronal emission, suggesting that coronally active stars have higher coronal temperatures. We find that our S1, S2, and IPC luminosities are well correlated with rotational velocity, and we compare activity-rotation relations determined using these different luminosities. Late M stars are found to be significantly less luminous in the EUV than other late-type stars. The most natural explanation for this results is the concept of coronal saturation -- the idea that late-type stars can emit only a limited fraction of their total luminosity in X-ray and EUV radiation, which means stars with very low bolometric luminosities must have relatively low X-ray and EUV luminosities as well. The maximum level of coronal emission from stars with earlier spectral types is studied also. To understand the saturation levels for these stars, we have compiled a large number of IPC luminosities for stars with a wide variety of spectral types and luminosity classes. We show quantitatively that if the Sun were completely covered with X-ray-emitting coronal loops, it would be near the saturation limit implied by this compilation, supporting the idea that stars near upper limits in coronal activity are completely covered with active regions.

The red and blue galaxy populations in the GOODS field: evidence for an excess of red dwarfs

NASA Astrophysics Data System (ADS)

Salimbeni, S.; Giallongo, E.; Menci, N.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.; Trevese, D.; Cristiani, S.; Nonino, M.; Vanzella, E.

2008-01-01

Aims: We study the evolution of the galaxy population up to z˜ 3 as a function of its colour properties. In particular, luminosity functions and luminosity densities were derived as a function of redshift for the blue/late and red/early populations. Methods: We use data from the GOODS-MUSIC catalogue, which have typical magnitude limits z850≤ 26 and K_s≤ 23.5 for most of the sample. About 8% of the galaxies have spectroscopic redshifts; the remaining have well calibrated photometric redshifts derived from the extremely wide multi-wavelength coverage in 14 bands (from the U band to the Spitzer 8~ μm band). We have derived a catalogue of galaxies complete in the rest-frame B-band, which has been divided into two subsamples according to their rest-frame U-V colour (or derived specific star formation rate) properties. Results: We confirm a bimodality in the U-V colour and specific star formation rate of the galaxy sample up to z˜ 3. This bimodality is used to compute the luminosity functions of the blue/late and red/early subsamples. The luminosity functions of the blue/late and total samples are well represented by steep Schechter functions evolving in luminosity with increasing redshifts. The volume density of the luminosity functions of the red/early populations decreases with increasing redshift. The shape of the red/early luminosity functions shows an excess of faint red dwarfs with respect to the extrapolation of a flat Schechter function and can be represented by the sum of two Schechter functions. Our model for galaxy formation in the hierarchical clustering scenario, which also includes external feedback due to a diffuse UV background, shows a general broad agreement with the luminosity functions of both populations, the larger discrepancies being present at the faint end for the red population. Hints on the nature of the red dwarf population are given on the basis of their stellar mass and spatial distributions.

Reverberation Mapping of the Continuum Source in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Fausnaugh, Michael Martin

I present results from a monitoring campaign of 11 active galactic nuclei (AGN) conducted in Spring of 2014. I use the reverberation mapping method to probe the interior structures of the AGN, specifically the broad line regions (BLRs) and accretion disks. One of these AGN, NGC 5548, was also subject to multi-wavelength (X-ray, UV, optical, and near-IR) monitoring using 25 ground-based telescopes and four space-based facilities. For NGC 5548, I detect lags between the continuum emission at different wavelengths that follow a trend consistent with the prediction for continuum reprocessing by an accretion disk with temperature profile T ∝ R -3/4. However, the lags imply a disk radius that is 3 times larger than the prediction from standard thin-disk models. The lags at wavelengths longer than the Vband are also equal to or greater than the lags of high-ionization-state emission lines (such as HeII lambda1640 and lambda4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region. Using optical spectra from the Large Binocular Telescope, I estimate the bias of the interband continuum lags due to BLR emission observed in the filters, and I find that the bias for filters with high levels of BLR contamination (˜20%) can be important for the shortest continuum lags. This likely has a significant impact on the u and U bands owing to Balmer continuum emission. I then develop a new procedure for the internal (night-to-night) calibration of time series spectra that can reach precisions of ˜1 millimagnitude and improves traditional techniques by up to a factor of 5. At this level, other systematic issues (e.g., the nightly sensitivity functions and Fe II contamination) limit the final precision of the observed light curves. Using the new calibration method, I next present the data and first results from the optical spectroscopic monitoring component of the reverberation mapping campaign. Five AGN were sufficiently variable to measure continuum-Hbeta lags and super-massive black hole masses: MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. I also obtain Hgamma and HeII lags for all objects except 3C 382. The HeII lags indicate radial stratification of the BLR, and the masses derived from different emission lines are in general agreement. The relative responsivities of these lines to continuum variations are also in qualitative agreement with photoionization models. Finally, I measure optical continuum lags for the two most variable targets, MCG+08-11-011 and NGC 2617. I again find lags consistent with geometrically thin accretion-disk models that have temperature profiles T ∝ R-3/4. The observed lags are larger than predictions based on standard thin-disk theory by factors of 3.3 for MCG+08-11-011 and 2.3 for NGC 2617. Using a physical model, these differences can be explained if the mass accretion rates are larger than inferred from the optical continuum luminosity by a factor of 4.3 in MCG+08-11-011 and a factor of 1.3 in NGC 2617. While the X-ray variability in NGC 2617 precedes the UV/optical variability, the long 2.6 day lag is problematic for coronal reprocessing models.

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

Mendigutía, I.; Brittain, S.; Eiroa, C.

This work presents X-Shooter/Very Large Telescope spectra of the prototypical, isolated Herbig Ae stars HD 31648 (MWC 480) and HD 163296 over five epochs separated by timescales ranging from days to months. Each spectrum spans over a wide wavelength range covering from 310 to 2475 nm. We have monitored the continuum excess in the Balmer region of the spectra and the luminosity of 12 ultraviolet, optical, and near-infrared spectral lines that are commonly used as accretion tracers for T Tauri stars. The observed strengths of the Balmer excesses have been reproduced from a magnetospheric accretion shock model, providing a meanmore » mass accretion rate of 1.11 × 10{sup –7} and 4.50 × 10{sup –7} M{sub ☉} yr{sup –1} for HD 31648 and HD 163296, respectively. Accretion rate variations are observed, being more pronounced for HD 31648 (up to 0.5 dex). However, from the comparison with previous results it is found that the accretion rate of HD 163296 has increased by more than 1 dex, on a timescale of ∼15 yr. Averaged accretion luminosities derived from the Balmer excess are consistent with the ones inferred from the empirical calibrations with the emission line luminosities, indicating that those can be extrapolated to HAe stars. In spite of that, the accretion rate variations do not generally coincide with those estimated from the line luminosities, suggesting that the empirical calibrations are not useful to accurately quantify accretion rate variability.« less

Effects of variability of X-ray binaries on the X-ray luminosity functions of Milky Way

NASA Astrophysics Data System (ADS)

Islam, Nazma; Paul, Biswajit

2016-08-01

The X-ray luminosity functions of galaxies have become a useful tool for population studies of X-ray binaries in them. The availability of long term light-curves of X-ray binaries with the All Sky X-ray Monitors opens up the possibility of constructing X-ray luminosity functions, by also including the intensity variation effects of the galactic X-ray binaries. We have constructed multiple realizations of the X-ray luminosity functions (XLFs) of Milky Way, using the long term light-curves of sources obtained in the 2-10 keV energy band with the RXTE-ASM. The observed spread seen in the value of slope of both HMXB and LMXB XLFs are due to inclusion of variable luminosities of X-ray binaries in construction of these XLFs as well as finite sample effects. XLFs constructed for galactic HMXBs in the luminosity range 1036-1039 erg/sec is described by a power-law model with a mean power-law index of -0.48 and a spread due to variability of HMXBs as 0.19. XLFs constructed for galactic LMXBs in the luminosity range 1036-1039 erg/sec has a shape of cut-off power-law with mean power-law index of -0.31 and a spread due to variability of LMXBs as 0.07.

Padé Approximant and Minimax Rational Approximation in Standard Cosmology

NASA Astrophysics Data System (ADS)

Zaninetti, Lorenzo

2016-02-01

The luminosity distance in the standard cosmology as given by $\\Lambda$CDM and consequently the distance modulus for supernovae can be defined by the Pad\\'e approximant. A comparison with a known analytical solution shows that the Pad\\'e approximant for the luminosity distance has an error of $4\\%$ at redshift $= 10$. A similar procedure for the Taylor expansion of the luminosity distance gives an error of $4\\%$ at redshift $=0.7 $; this means that for the luminosity distance, the Pad\\'e approximation is superior to the Taylor series. The availability of an analytical expression for the distance modulus allows applying the Levenberg--Marquardt method to derive the fundamental parameters from the available compilations for supernovae. A new luminosity function for galaxies derived from the truncated gamma probability density function models the observed luminosity function for galaxies when the observed range in absolute magnitude is modeled by the Pad\\'e approximant. A comparison of $\\Lambda$CDM with other cosmologies is done adopting a statistical point of view.

Spectroscopy of luminous infrared galaxies at 2 microns: 1. The ultraluminous galaxies (L(sub IR) approximately greater than 10 (exp 12) solar luminosity)

NASA Technical Reports Server (NTRS)

Goldader, Jeffrey D.; Joseph, R. D.; Doyon, Rene; Sanders, D. B.

1995-01-01

We present high-quality spectra covering the K window at a resolving power of 340 for a sample of 13 ultraluminous (L(sub IR) approximately greater than 10(exp 12) solar luminosity) infrared-selected galaxies, and line fluxes for a comparison sample of 24 lower luminosity galaxies. The 2 micrometers spectra of 10 of the ultraluminous galaxies are characterized by emission and absorption features commonly associated with stars and star formation; two others have the red power-law spectra and Br gamma line widths of Seyfert 1 galaxies; the final galaxy has strong emission from hot dust. We have found no broad-line active nuclei not already known from optical observations, despite the fact that the extinction at 2 micrometers is 1/10 that at optical wavelengths; any putative Seyfert 1 nuclei must be deeply buried. Powerful continua and emission lines from H2 and Br gamma are detected in all the ultraluminous galaxies. Comparing the H2 1-0 S(1), Br gamma, and 2 micrometers and far-infrared luminosities to those of the lower luminosity galaxies yields several major results. First, the dereddened Br gamma emission, relative to the far-infrared luminosity is significantly depressed in the ultraluminous sample, when compared to the lower luminosity galaxies. Five of the ultraluminous galaxies have L(sub Br gamma)L(sub IR) ratios lower than for any of the comparison objects. Second, the H2 1-0 S(1) luminosity is also responsible, directly or indirectly, for producing the excited H2, and that the H2 apparently comes from optically thin regions in both classes of objects. Third, eight of the 13 ultraluminous systems have lower 2 micrometers/far-infrared luminosity ratios than any of the lower luminosity galaxies, and five of these are the galaxies also deficient in Br gamma. These three findings may be understood if the the H2, Br gamma, and 2 mircometers continua in the ultraluminous galaxies arise from spatially distinct regions, with the continuum and Br gamma largely coming from volumes optically thick even at 2 micrometers, and obscured in such a fashion that the extinctions measured using optical spectroscopy do not properly measure the true optical depths. If this is the case, then even near-infrared spectroscopy may be unable to exclude the presence of undetected powerful active galactive nuclei in the ultraluminous galaxies.

a Study of the AGB in Local Group Bulge Populations

NASA Astrophysics Data System (ADS)

Rich, R.

1994-01-01

We propose to survey the bolometric luminosities, colors, and space distribution of the most luminous asymptotic giant branch (AGB) stars in the bulges of M31, M32, and M33. We seek to discover whether the bulges of these galaxies are relatively young, of order 10 Gyr rather than 15 Gyr. We will use WFPC2 and the R, I, and F1042M (1 micron) filters. Knowing that F1042M falls on the first continuum point of M giants, we have shown that we can use 1.04 micron fluxes to reliably calculate bolometric magnitudes for these very red stars. Color information from R and I will permit (1) comparison with Galactic bulge M giants, (2) an estimate of the spread of abundance and (3) increase the accuracy of the bolometric magnitudes. Frames with the damaged HST show signs of resolution to within 3" of the M31 nucleus; Red images with the aberrated HST show a red star cluster associated with the nucleus. Ground-based studies of M32 find an intermediate-age population from spectroscopy and infrared photometry. The repaired HST should resolve stars close to the nuclei of these galaxies. We will measure bolometric luminosity functions to determine if the populations are intermediate age, and attempt to measure the abundance range for stars near the nuclei of these galaxies. If metals have been lost due to winds, theory predicts that we should see a substantial spread of abundances even near the nucleus.

Light propagation through black-hole lattices

NASA Astrophysics Data System (ADS)

Bentivegna, Eloisa; Korzyński, Mikołaj; Hinder, Ian; Gerlicher, Daniel

2017-03-01

The apparent properties of distant objects encode information about the way the light they emit propagates to an observer, and therefore about the curvature of the underlying spacetime. Measuring the relationship between the redshift z and the luminosity distance DL of a standard candle, for example, yields information on the Universe's matter content. In practice, however, in order to decode this information the observer needs to make an assumption about the functional form of the DL(z) relation; in other words, a cosmological model needs to be assumed. In this work, we use numerical-relativity simulations, equipped with a new ray-tracing module, to numerically obtain this relation for a few black-hole-lattice cosmologies and compare it to the well-known Friedmann-Lema{ȋtre-Robertson-Walker case, as well as to other relevant cosmologies and to the Empty-Beam Approximation. We find that the latter provides the best estimate of the luminosity distance and formulate a simple argument to account for this agreement. We also find that a Friedmann-Lema{ȋtre-Robertson-Walker model can reproduce this observable exactly, as long as a time-dependent cosmological constant is included in the fit. Finally, the dependence of these results on the lattice mass-to-spacing ratio μ is discussed: we discover that, unlike the expansion rate, the DL(z) relation in a black-hole lattice does not tend to that measured in the corresponding continuum spacetime as 0μ → .

Light propagation through black-hole lattices

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

Bentivegna, Eloisa; Korzyński, Mikołaj; Hinder, Ian

The apparent properties of distant objects encode information about the way the light they emit propagates to an observer, and therefore about the curvature of the underlying spacetime. Measuring the relationship between the redshift z and the luminosity distance D {sub L} of a standard candle, for example, yields information on the Universe's matter content. In practice, however, in order to decode this information the observer needs to make an assumption about the functional form of the D {sub L}( z ) relation; in other words, a cosmological model needs to be assumed. In this work, we use numerical-relativity simulations,more » equipped with a new ray-tracing module, to numerically obtain this relation for a few black-hole-lattice cosmologies and compare it to the well-known Friedmann-Lema(ȋtre-Robertson-Walker case, as well as to other relevant cosmologies and to the Empty-Beam Approximation. We find that the latter provides the best estimate of the luminosity distance and formulate a simple argument to account for this agreement. We also find that a Friedmann-Lema(ȋtre-Robertson-Walker model can reproduce this observable exactly, as long as a time-dependent cosmological constant is included in the fit. Finally, the dependence of these results on the lattice mass-to-spacing ratio μ is discussed: we discover that, unlike the expansion rate, the D {sub L}( z ) relation in a black-hole lattice does not tend to that measured in the corresponding continuum spacetime as 0μ → .« less

A Physically based Model of the Ionizing Radiation from Active Galaxies for Photoionization Modeling

NASA Astrophysics Data System (ADS)

Thomas, A. D.; Groves, B. A.; Sutherland, R. S.; Dopita, M. A.; Kewley, L. J.; Jin, C.

2016-12-01

We present a simplified model of active galactic nucleus (AGN) continuum emission designed for photoionization modeling. The new model oxaf reproduces the diversity of spectral shapes that arise in physically based models. We identify and explain degeneracies in the effects of AGN parameters on model spectral shapes, with a focus on the complete degeneracy between the black hole mass and AGN luminosity. Our reparametrized model oxaf removes these degeneracies and accepts three parameters that directly describe the output spectral shape: the energy of the peak of the accretion disk emission {E}{peak}, the photon power-law index of the non-thermal emission Γ, and the proportion of the total flux that is emitted in the non-thermal component {p}{NT}. The parameter {E}{peak} is presented as a function of the black hole mass, AGN luminosity, and “coronal radius” of the optxagnf model upon which oxaf is based. We show that the soft X-ray excess does not significantly affect photoionization modeling predictions of strong emission lines in Seyfert narrow-line regions. Despite its simplicity, oxaf accounts for opacity effects where the accretion disk is ionized because it inherits the “color correction” of optxagnf. We use a grid of mappings photoionization models with oxaf ionizing spectra to demonstrate how predicted emission-line ratios on standard optical diagnostic diagrams are sensitive to each of the three oxaf parameters. The oxaf code is publicly available in the Astrophysics Source Code Library.

DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

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

Kim, Yongjung; Im, Myungshin; Jeon, Yiseul

2015-11-10

Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to zmore » = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.« less

MUSE deep-fields: the Ly α luminosity function in the Hubble Deep Field-South at 2.91 < z < 6.64

NASA Astrophysics Data System (ADS)

Drake, Alyssa B.; Guiderdoni, Bruno; Blaizot, Jérémy; Wisotzki, Lutz; Herenz, Edmund Christian; Garel, Thibault; Richard, Johan; Bacon, Roland; Bina, David; Cantalupo, Sebastiano; Contini, Thierry; den Brok, Mark; Hashimoto, Takuya; Marino, Raffaella Anna; Pelló, Roser; Schaye, Joop; Schmidt, Kasper B.

2017-10-01

We present the first estimate of the Ly α luminosity function using blind spectroscopy from the Multi Unit Spectroscopic Explorer, MUSE, in the Hubble Deep Field-South. Using automatic source-detection software, we assemble a homogeneously detected sample of 59 Ly α emitters covering a flux range of -18.0 < log10 (F) < -16.3 (erg s-1 cm-2), corresponding to luminosities of 41.4 < log10 (L) < 42.8 (erg s-1). As recent studies have shown, Ly α fluxes can be underestimated by a factor of 2 or more via traditional methods, and so we undertake a careful assessment of each object's Ly α flux using a curve-of-growth analysis to account for extended emission. We describe our self-consistent method for determining the completeness of the sample, and present an estimate of the global Ly α luminosity function between redshifts 2.91 < z < 6.64 using the 1/Vmax estimator. We find that the luminosity function is higher than many number densities reported in the literature by a factor of 2-3, although our result is consistent at the 1σ level with most of these studies. Our observed luminosity function is also in good agreement with predictions from semi-analytic models, and shows no evidence for strong evolution between the high- and low-redshift halves of the data. We demonstrate that one's approach to Ly α flux estimation does alter the observed luminosity function, and caution that accurate flux assessments will be crucial in measurements of the faint-end slope. This is a pilot study for the Ly α luminosity function in the MUSE deep-fields, to be built on with data from the Hubble Ultra Deep Field that will increase the size of our sample by almost a factor of 10.

Cosmic reionization on computers: The faint end of the galaxy luminosity function

DOE PAGES

Gnedin, Nickolay Y.

2016-07-01

Using numerical cosmological simulations completed under the “Cosmic Reionization On Computers” project, I explore theoretical predictions for the faint end of the galaxy UV luminosity functions atmore » $$z\\gtrsim 6$$. A commonly used Schechter function approximation with the magnitude cut at $${M}_{{\\rm{cut}}}\\sim -13$$ provides a reasonable fit to the actual luminosity function of simulated galaxies. When the Schechter functional form is forced on the luminosity functions from the simulations, the magnitude cut $${M}_{{\\rm{cut}}}$$ is found to vary between -12 and -14 with a mild redshift dependence. Here, an analytical model of reionization from Madau et al., as used by Robertson et al., provides a good description of the simulated results, which can be improved even further by adding two physically motivated modifications to the original Madau et al. equation.« less

Cosmic reionization on computers: The faint end of the galaxy luminosity function

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

Gnedin, Nickolay Y.

Using numerical cosmological simulations completed under the “Cosmic Reionization On Computers” project, I explore theoretical predictions for the faint end of the galaxy UV luminosity functions atmore » $$z\\gtrsim 6$$. A commonly used Schechter function approximation with the magnitude cut at $${M}_{{\\rm{cut}}}\\sim -13$$ provides a reasonable fit to the actual luminosity function of simulated galaxies. When the Schechter functional form is forced on the luminosity functions from the simulations, the magnitude cut $${M}_{{\\rm{cut}}}$$ is found to vary between -12 and -14 with a mild redshift dependence. Here, an analytical model of reionization from Madau et al., as used by Robertson et al., provides a good description of the simulated results, which can be improved even further by adding two physically motivated modifications to the original Madau et al. equation.« less

A multiparametric analysis of the Einstein sample of early-type galaxies. 1: Luminosity and ISM parameters

NASA Technical Reports Server (NTRS)

Eskridge, Paul B.; Fabbiano, Giuseppina; Kim, Dong-Woo

1995-01-01

We have conducted bivariate and multivariate statistical analysis of data measuring the luminosity and interstellar medium of the Einstein sample of early-type galaxies (presented by Fabbiano, Kim, & Trinchieri 1992). We find a strong nonlinear correlation between L(sub B) and L(sub X), with a power-law slope of 1.8 +/- 0.1, steepening to 2.0 +/- if we do not consider the Local Group dwarf galaxies M32 and NGC 205. Considering only galaxies with log L(sub X) less than or equal to 40.5, we instead find a slope of 1.0 +/- 0.2 (with or without the Local Group dwarfs). Although E and S0 galaxies have consistent slopes for their L(sub B)-L(sub X) relationships, the mean values of the distribution functions of both L(sub X) and L(sub X)/L(sub B) for the S0 galaxies are lower than those for the E galaxies at the 2.8 sigma and 3.5 sigma levels, respectively. We find clear evidence for a correlation between L(sub X) and the X-ray color C(sub 21), defined by Kim, Fabbiano, & Trinchieri (1992b), which indicates that X-ray luminosity is correlated with the spectral shape below 1 keV in the sense that low-L(sub X) systems have relatively large contributions from a soft component compared with high-L(sub X) systems. We find evidence from our analysis of the 12 micron IRAS data for our sample that our S0 sample has excess 12 micron emission compared with the E sample, scaled by their optical luminosities. This may be due to emission from dust heated in star-forming regions in S0 disks. This interpretation is reinforced by the existence of a strong L(sub 12)-L(sub 100) correlation for our S0 sample that is not found for the E galaxies, and by an analysis of optical-IR colors. We find steep slopes for power-law relationships between radio luminosity and optical, X-ray, and far-IR (FIR) properties. This last point argues that the presence of an FIR-emitting interstellar medium (ISM) in early-type galaxies is coupled to their ability to generate nonthermal radio continuum, as previously argued by, e.g., Walsh et al. (1989). We also find that, for a given L(sub 100), galaxies with larger L(sub X)/L(sub B) tend to be stronger nonthermal radio sources, as originally suggested by Kim & Fabbiano (1990). We note that, while L(sub B) is most strongly correlated with L(sub 6), the total radio luminosity, both L(sub X) and L(sub X)/L(sub B) are more strongly correlated with L(sub 6 CO), the core radio luminosity. These points support the argument (proposed by Fabbiano, Gioia, & Trinchieri 1989) that radio cores in early-type galaxies are fueled by the hot ISM.

Local Luminosity Function at 15 micro m and Galaxy Evolution Seen by ISOCAM 15 micro m Surveys

NASA Technical Reports Server (NTRS)

Xu, C.

2000-01-01

A local luminosity function at 15 micro m is derived using the bivariate (15 micro m vs. 60 micro m luminosities) method, based on the newly published ISOCAM LW3-band (15 micro m) survey of the very deep IRAS 60 micro m sample in the north ecliptic pole region (NEPR).

The white dwarf luminosity function - A possible probe of the galactic halo

NASA Technical Reports Server (NTRS)

Tamanaha, Christopher M.; Silk, Joseph; Wood, M. A.; Winget, D. E.

1990-01-01

The dynamically inferred dark halo mass density, amounting to above 0.01 solar masses/cu pc at the sun's Galactocentric radius, can be composed of faint white dwarfs provided that the halo formed in a sufficiently early burst of star formation. The model is constrained by the observed disk white dwarf luminosity function which falls off below log (L/solar L) = -4.4, due to the onset of star formation in the disk. By using a narrow range for the initial mass function and an exponentially decaying halo star formation rate with an e-folding time equal to the free-fall time, all the halo dark matter is allowed to be in cool white dwarfs which lie beyond the falloff in the disk luminosity function. Although it is unlikely that all the dark matter is in these dim white dwarfs, a definite signature in the low-luminosity end of the white dwarf luminosity function is predicted even if they comprise only 1 percent of the dark matter. Current CCD surveys should answer the question of the existence of this population within the next few years.

Lyman-break Galaxies at z ˜ 3 in the Subaru Deep Field: Luminosity Function, Clustering, and [O III] Emission

NASA Astrophysics Data System (ADS)

Malkan, Matthew A.; Cohen, Daniel P.; Maruyama, Miyoko; Kashikawa, Nobunari; Ly, Chun; Ishikawa, Shogo; Shimasaku, Kazuhiro; Hayashi, Masao; Motohara, Kentaro

2017-11-01

We combined deep U-band and optical/near-infrared imaging, in order to select Lyman Break Galaxies (LBGs) at z˜ 3 using U - V and V-{R}c colors in the Subaru Deep Field. The resulting sample of 5161 LBGs gives a UV luminosity function (LF) down to {M}{UV}=-18, with a steep faint-end slope of α =-1.78+/- 0.05. We analyze UV-to-NIR energy distributions (SEDs) from optical photometry and photometry on IR median-stacked images. In the stacks, we find a systematic background depression centered on the LBGs. This results from the difficulty of finding faint galaxies in regions with higher-than-average surface densities of foreground galaxies, so we corrected for this deficit. Best-fit stellar population models for the LBG SEDs indicate stellar masses and star formation rates of {{log}}10({M}* /{M}⊙ )≃ 10 and ≃ 50 M ⊙ yr-1 at < {i}{AB}{\\prime }> =24, down to {{log}}10({M}* /{M}⊙ )≃ 8 and ≃ 3 {M}⊙ yr-1 at < {i}{AB}{\\prime }> =27. The faint LBGs show a ˜1 mag excess over the stellar continuum in K-band. We interpret this excess flux as redshifted [O III]λ λ {4959,5007} lines. The observed excesses imply equivalent widths that increase with decreasing mass, reaching {{EW}}0([{{O}} {{iii}}]4959,5007+{{H}}β )≳ 1500 Å (rest-frame). Such strong [O III] emission is seen only in a miniscule fraction of local emission-line galaxies, but is probably universal in the faint galaxies that reionized the universe. Our halo occupation distribution analysis of the angular correlation function gives a halo mass of {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.29+/- 0.12 for the full sample of LBGs, and {{log}}10(< {M}{{h}}> /{h}-1{M}⊙ )=11.49+/- 0.1 for the brightest half of the sample.

Disk Evaporation in Star Forming Regions

NASA Technical Reports Server (NTRS)

Hollenbach, David; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

Young stars produce sufficient ultraviolet photon luminosity and mechanical luminosity in their winds to significantly affect the structure and evolution of the accretion disks surrounding them. The Lyman continuum photons create a nearly static, ionized, isothermal 10(exp 4) K atmosphere forms above the neutral disk at small distances from the star. Further out, they create a photoevaporative flow which relatively rapidly destroys the disk. The resulting slow (10-50 km/s) ionized outflow, which persists for approx. greater than 10(exp 5) years for disk masses M(sub d) approx. 0.3M(sub *), may explain the observational characteristics of many ultracompact HII regions. We compare model results to the observed radio free-free spectra and luminosities of ultracompact HII regions and to the interesting source MWC349, which is observed to produce hydrogen masers. We apply the results to Ae and Be stars in order to determine the lifetimes of disks around such stars. We also apply the results to the early solar nebula to explain the the dispersal of the solar nebula and the differences in hydrogen content in the giant planets. Finally, we model the small bright objects ("proplyds") observed in the Orion Nebula as disks around young, low mass stars which are externally illuminated by the UV photons from the nearby massive star Theta(sup 1) C.

Star-formation rate in compact star-forming galaxies

NASA Astrophysics Data System (ADS)

Izotova, I. Y.; Izotov, Y. I.

2018-03-01

We use the data for the Hβ emission-line, far-ultraviolet (FUV) and mid-infrared 22 μm continuum luminosities to estimate star formation rates < SFR > averaged over the galaxy lifetime for a sample of about 14000 bursting compact star-forming galaxies (CSFGs) selected from the Data Release 12 (DR12) of the Sloan Digital Sky Survey (SDSS). The average coefficient linking < SFR > and the star formation rate SFR0 derived from the Hβ luminosity at zero starburst age is found to be 0.04. We compare < SFR > s with some commonly used SFRs which are derived adopting a continuous star formation during a period of {˜} 100 Myr, and find that the latter ones are 2-3 times higher. It is shown that the relations between SFRs derived using a geometric mean of two star-formation indicators in the UV and IR ranges and reduced to zero starburst age have considerably lower dispersion compared to those with single star-formation indicators. We suggest that our relations for < SFR > determination are more appropriate for CSFGs because they take into account a proper temporal evolution of their luminosities. On the other hand, we show that commonly used SFR relations can be applied for approximate estimation within a factor of {˜} 2 of the < SFR > averaged over the lifetime of the bursting compact galaxy.

An order statistics approach to the halo model for galaxies

NASA Astrophysics Data System (ADS)

Paul, Niladri; Paranjape, Aseem; Sheth, Ravi K.

2017-04-01

We use the halo model to explore the implications of assuming that galaxy luminosities in groups are randomly drawn from an underlying luminosity function. We show that even the simplest of such order statistics models - one in which this luminosity function p(L) is universal - naturally produces a number of features associated with previous analyses based on the 'central plus Poisson satellites' hypothesis. These include the monotonic relation of mean central luminosity with halo mass, the lognormal distribution around this mean and the tight relation between the central and satellite mass scales. In stark contrast to observations of galaxy clustering; however, this model predicts no luminosity dependence of large-scale clustering. We then show that an extended version of this model, based on the order statistics of a halo mass dependent luminosity function p(L|m), is in much better agreement with the clustering data as well as satellite luminosities, but systematically underpredicts central luminosities. This brings into focus the idea that central galaxies constitute a distinct population that is affected by different physical processes than are the satellites. We model this physical difference as a statistical brightening of the central luminosities, over and above the order statistics prediction. The magnitude gap between the brightest and second brightest group galaxy is predicted as a by-product, and is also in good agreement with observations. We propose that this order statistics framework provides a useful language in which to compare the halo model for galaxies with more physically motivated galaxy formation models.

Infrared emission of young HII regions: a Herschel/Hi-GAL study

NASA Astrophysics Data System (ADS)

Cesaroni, R.; Pestalozzi, M.; Beltrán, M. T.; Hoare, M. G.; Molinari, S.; Olmi, L.; Smith, M. D.; Stringfellow, G. S.; Testi, L.; Thompson, M. A.

2015-07-01

Context. Investigating the relationship between radio and infrared emission of Hii regions may help shed light on the nature of the ionizing stars and the formation mechanism of early-type stars in general. Aims: We have taken advantage of recent unbiased surveys of the Galactic plane such as Herschel/Hi-GAL and VLA/CORNISH to study a bona fide sample of young Hii regions located in the Galactic longitude range 10°-65° by comparing the mid- and far-IR continuum emission to the radio free-free emission at 5 GHz. Methods: We have identified the Hi-GAL counterparts of 230 CORNISH Hii regions and reconstructed the spectral energy distributions of 204 of these by complementing the Hi-GAL fluxes with ancillary data at longer and shorter wavelengths. Using literature data, we obtained a kinematical distance estimate for 200 Hii regions with Hi-GAL counterparts and determined their luminosities by integrating the emission of the corresponding spectral energy distributions. We have also estimated the mass of the associated molecular clumps from the (sub)millimeter flux densities. Results: Our main finding is that for ~1/3 of the Hii regions the Lyman continuum luminosity appears to be greater than the value expected for a zero-age main-sequence star with the same bolometric luminosity. This result indicates that a considerable fraction of young, embedded early-type stars presents a "Lyman excess" possibly due to UV photons emitted from shocked material infalling onto the star itself and/or a circumstellar disk. Finally, by comparing the bolometric and Lyman continuum luminosities with the mass of the associated clump, we derive a star formation efficiency of 5%. Conclusions: The results obtained suggest that accretion may still be present during the early stages of the evolution of Hii regions, with important effects on the production of ionizing photons and thus on the circumstellar environment. More reliable numerical models describing the accretion process onto massive stars are required to shed light on the origin of the observed Lyman excess. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. PACS has been developed by a consortium of institutes led by MPE (Germany) and including UVIE (Austria); KUL, CSL, IMEC (Belgium); CEA, OAM P (France); MPIA (Germany); IAPS, OAP/OAT, OAA/CAISMI, LENS, SISSA (Italy); IAC (Spain). This development has been supported by the funding agencies BMVIT (Austria), ESA-PRODEX (Belgium), CEA/CNES (France), DLR (Germany), ASI (Italy), and CICYT/MCYT (Spain). SPIRE has been developed by a consortium of institutes led by Cardiff Univ. (UK) and including Univ. Lethbridge (Canada); NAOC (China); CEA , LAM (France); IAPS, Univ. Padua (Italy); IAC (Spain); Stockholm Observatory (Sweden); Imperial College London, RAL, UCL-MSSL, UKATC, Univ. Sussex (UK); Caltech, JPL, NHSC, Univ. Colorado (USA). This development has been supported by national funding agencies: CSA (Canada); NA OC (China); CEA, CNES, CNRS (France); ASI (Italy); MCINN (Spain); Stockholm Observatory (Sweden); STFC (UK); and NASA (USA).Appendix A is available in electronic form at http://www.aanda.org

Haro 11: Where is the Lyman Continuum Source?

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

Keenan, Ryan P.; Oey, M. S.; Jaskot, Anne E.

2017-10-10

Identifying the mechanism by which high-energy Lyman continuum (LyC) photons escaped from early galaxies is one of the most pressing questions in cosmic evolution. Haro 11 is the best known local LyC-leaking galaxy, providing an important opportunity to test our understanding of LyC escape. The observed LyC emission in this galaxy presumably originates from one of the three bright, photoionizing knots known as A, B, and C. It is known that Knot C has strong Ly α emission, and Knot B hosts an unusually bright ultraluminous X-ray source, which may be a low-luminosity active galactic nucleus. To clarify the LyCmore » source, we carry out ionization-parameter mapping (IPM) by obtaining narrow-band imaging from the Hubble Space Telescope WFC3 and ACS cameras to construct spatially resolved ratio maps of [O iii]/[O ii] emission from the galaxy. IPM traces the ionization structure of the interstellar medium and allows us to identify optically thin regions. To optimize the continuum subtraction, we introduce a new method for determining the best continuum scale factor derived from the mode of the continuum-subtracted, image flux distribution. We find no conclusive evidence of LyC escape from Knots B or C, but instead we identify a high-ionization region extending over at least 1 kpc from Knot A. This knot shows evidence of an extremely young age (≲1 Myr), perhaps containing very massive stars (>100 M {sub ⊙}). It is weak in Ly α , so if it is confirmed as the LyC source, our results imply that LyC emission may be independent of Ly α emission.« less

SPT0346-52: Negligible AGN Activity in a Compact, Hyper-starburst Galaxy at z = 5.7

NASA Astrophysics Data System (ADS)

Ma, Jingzhe; Gonzalez, Anthony. H.; Vieira, J. D.; Aravena, M.; Ashby, M. L. N.; Béthermin, M.; Bothwell, M. S.; Brandt, W. N.; de Breuck, C.; Carlstrom, J. E.; Chapman, S. C.; Gullberg, B.; Hezaveh, Y.; Litke, K.; Malkan, M.; Marrone, D. P.; McDonald, M.; Murphy, E. J.; Spilker, J. S.; Sreevani, J.; Stark, A. A.; Strandet, M.; Wang, S. X.

2016-12-01

We present Chandra ACIS-S and Australia Telescope Compact Array (ATCA) radio continuum observations of the strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter SPT0346-52) at z = 5.656. This galaxy has also been observed with ALMA, HST, Spitzer, Herschel, Atacama Pathfinder EXperiment, and the Very Large Telescope. Previous observations indicate that if the infrared (IR) emission is driven by star formation, then the inferred lensing-corrected star formation rate (SFR) (˜4500 M ⊙ yr-1) and SFR surface density ΣSFR (˜2000 M ⊙ yr-1 kpc-2) are both exceptionally high. It remained unclear from the previous data, however, whether a central active galactic nucleus (AGN) contributes appreciably to the IR luminosity. The Chandra upper limit shows that SPT0346-52 is consistent with being star formation dominated in the X-ray, and any AGN contribution to the IR emission is negligible. The ATCA radio continuum upper limits are also consistent with the FIR-to-radio correlation for star-forming galaxies with no indication of an additional AGN contribution. The observed prodigious intrinsic IR luminosity of (3.6 ± 0.3) × 1013 L ⊙ originates almost solely from vigorous star formation activity. With an intrinsic source size of 0.61 ± 0.03 kpc, SPT0346-52 is confirmed to have one of the highest ΣSFR of any known galaxy. This high ΣSFR, which approaches the Eddington limit for a radiation pressure supported starburst, may be explained by a combination of very high star formation efficiency and gas fraction.

Probing star formation relations of mergers and normal galaxies across the CO ladder

NASA Astrophysics Data System (ADS)

Greve, Thomas R.

We examine integrated luminosity relations between the IR continuum and the CO rotational ladder observed for local (ultra) luminous infra-red galaxies ((U)LIRGs, L IR >= 1011 M⊙) and normal star forming galaxies in the context of radiation pressure regulated star formation proposed by Andrews & Thompson (2011). This can account for the normalization and linear slopes of the luminosity relations (log L IR = α log L'CO + β) of both low- and high-J CO lines observed for normal galaxies. Super-linear slopes occur for galaxy samples with significantly different dense gas fractions. Local (U)LIRGs are observed to have sub-linear high-J (J up > 6) slopes or, equivalently, increasing L COhigh-J /L IR with L IR. In the extreme ISM conditions of local (U)LIRGs, the high-J CO lines no longer trace individual hot spots of star formation (which gave rise to the linear slopes for normal galaxies) but a more widespread warm and dense gas phase mechanically heated by powerful supernovae-driven turbulence and shocks.

Interstellar matter in early-type galaxies. II - The relationship between gaseous components and galaxy types

NASA Technical Reports Server (NTRS)

Bregman, Joel N.; Hogg, David E.; Roberts, Morton S.

1992-01-01

Interstellar components of early-type galaxies are established by galactic type and luminosity in order to search for relationships between the different interstellar components and to test the predictions of theoretical models. Some of the data include observations of neutral hydrogen, carbon monoxide, and radio continuum emission. An alternative distance model which yields LX varies as LB sup 2.45, a relation which is in conflict with simple cooling flow models, is discussed. The dispersion of the X-ray luminosity about this regression line is unlikely to result from stripping. The striking lack of clear correlations between hot and cold interstellar components, taken together with their morphologies, suggests that the cold gas is a disk phenomenon while the hot gas is a bulge phenomenon, with little interaction between the two. The progression of galaxy type from E to Sa is not only a sequence of decreasing stellar bulge-to-disk ratio, but also of hot-to-cold-gas ratio.

Luminosity Function of Faint Globular Clusters in M87

NASA Astrophysics Data System (ADS)

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

2006-10-01

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

Clustering, Cosmology and a New Era of Black Hole Demographics: The Conditional Luminosity Function of AGNs

NASA Astrophysics Data System (ADS)

Ballantyne, David R.

2017-01-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z~5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, we present a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z≈0 and 0.9 using the limited data that is currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z≈0.9 quasars may be commonly hosted by haloes with Mh ~ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGNs of different luminosities in cosmological simulations.

The luminosity function for different morphological types in the CfA Redshift Survey

NASA Technical Reports Server (NTRS)

Marzke, Ronald O.; Geller, Margaret J.; Huchra, John P.; Corwin, Harold G., Jr.

1994-01-01

We derive the luminosity function for different morphological types in the original CfA Redshift Survey (CfA1) and in the first two slices of the CfA Redshift Survey Extension (CfA2). CfA1 is a complete sample containing 2397 galaxies distributed over 2.7 steradians with m(sub z) less than or equal 14.5. The first two complete slices of CfA2 contain 1862 galaxies distributed over 0.42 steradians with m(sub z)=15.5. The shapes of the E-S0 and spiral luminosity functions (LF) are indistinguishable. We do not confirm the steeply decreasing faint end in the E-S0 luminosity function found by Loveday et al. for an independent sample in the southern hemisphere. We demonstrate that incomplete classification in deep redshift surveys can lead to underestimates of the faint end of the elliptical luminosity function and could be partially responsible for the difference between the CfA survey and other local field surveys. The faint end of the LF for the Magellanic spirals and irregulars is very steep. The Sm-Im luminosity function is well fit by a Schechter function with M*=-18.79, alpha=-1.87, and phi*=0.6x10(exp -3) for M(sub z) less than or equal to -13. These galaxies are largely responsible for the excess at the faint end of the general CfA luminosity function. The abundance of intrinsically faint, blue galaxies nearby affects the interpretation of deep number counts. The dwarf population increases the expected counts at B=25 in a no-evolution, q(sub 0)=0.05 model by a factor of two over standard no-evolution estimates. These dwarfs change the expected median redshift in deep redshift surveys by less than 10 percent . Thus the steep Sm-Im LF may contribute to the reconciliation of deep number counts with deep redshift surveys.

On the luminosity function, lifetimes, and origin of blue stragglers in globular clusters

NASA Technical Reports Server (NTRS)

Bailyn, Charles D.; Pinsonneault, Marc H.

1995-01-01

We compute theoretical evolutionary tracks of blue stragglers created by mergers. Two formation scenarios are considered: mergers of primordial binaries, and stellar collisions. These two scenarios predict strikingly different luminosity functions, which are potentially distinguishable observationally. Tabulated theoretical luminosity functions and lifetimes are presented for blue stragglers formed under a variety of input conditions. We compare our results with observations of the blue straggler sequences in 47 Tucanae and M3. In the case of 47 Tuc, the luminosity function and the formation rate are compatible with the hypothesis that the blue stragglers formed through the collision of single stars. Mergers of primordial binaries are only marginally cosistent with the data, and a significant enhancement of the collision cross section by binary-single-star encounters appears to be ruled out. In the case of M3, we find that the innermost blue stragglers have a luminosity function significantly different from that of the outer stragglers, thus confirming earlier suggestions that there are two distinct populations of blue stragglers in this cluster. The inner stragglers are preferentially brighter and bluer, as would be expected if they were made by collisions, but there are so many of them that the collision rate would need to be enhanced by interactions involving wide binaries. The luminosity function of the outer stragglers is almost identical to the predictions of mergers from primordial binaries and is inconsistent with the collision hypothesis.

Photodissociation Regions in the Interstellar Medium of Galaxies

NASA Technical Reports Server (NTRS)

Hollenbach, David J.; Tielens, A. G. G. M.; DeVincenzi, Donald L. (Technical Monitor)

1999-01-01

The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eV less than h(nu) less than 13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed Photo-Dissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C+, and O; rovibrational lines of H2, rotational lines of CO; broad middle features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H2 and C+ to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158 microns with the COJ = 1-0 emission, the COJ = 1-0 luminosity with the interstellar molecular mass, and the [CII] 158 microns plus [OI] 63 microns luminosity with the IR continuum luminosity. On a more global scale, MR models predict the existence of two stable neutral phases of the interstellar medium, elucidate the formation and destruction of star-forming molecular clouds, and suggest radiation-induced feedback mechanisms that may regulate star formation rates and the column density of gas through giant molecular clouds.

PKS 0537-286, carrying the information of the environment of SMBHs in the early Universe

NASA Astrophysics Data System (ADS)

Bottacini, E.; Ajello, M.; Greiner, J.; Pian, E.; Rau, A.; Palazzi, E.; Covino, S.; Ghisellini, G.; Krühler, T.; Küpcü Yoldaş, A.; Cappelluti, N.; Afonso, P.

2010-01-01

Context. The high-redshift (z = 3.1) blazar PKS 0537-286, belonging to the flat spectrum radio quasar blazar subclass, is one of the most luminous active galactic nuclei (AGN) in the Universe. Blazars are very suitable candidates for multiwavelength observations. Indeed, the relativistic beaming effect at work within the jet enhances their luminosity. This in turn allows the properties of the extragalactic jets, the powering central engine, and the surrounding environment to be derived. Aims: Our aim is to present the results of a multifrequency campaign from the near-IR to hard X-ray energies on PKS 0537-286 and give insight into the physical environment where the radiation processes take place. Methods: We observed the source at different epochs from 2006 to 2008 with INTEGRAL and Swift, and nearly simultaneously with ground-based optical telescopes. We also analyzed two archival spectra taken with XMM-Newton in 1999 and 2005. A comparative analysis of the results is performed. Results: The X-ray continuum of the blazar, as sampled by XMM, is described by a power law of index Γ = 1.2, modified by variable absorption at the soft X-rays, as found in other high-redshift QSOs. Modest X-ray continuum variability is found in the Swift observations. The combined Swift/BAT and Swift/XRT spectrum is very hard (Γ = 1.3). This, together with the non simultaneous EGRET detection and the more recent non detection by Fermi-LAT, constrains the peak of the high-energy component robustly. The optical/UV data, heavily affected by intervening Ly α absorption, indicate the presence of a bright thermal accretion disk that decreased in luminosity between 2006 and 2008. We infer from this a reduction of the BLR radius. When taking this into account, the 2006 and 2008 SEDs are compatible with a model based on synchrotron radiation and external inverse Compton scattering where the accretion-disk luminosity decreases between the 2 epochs by a factor 2, while the bulk Lorentz factor remains unchanged and the magnetic field changed only marginally.

An ALMA [C II] Survey of 27 Quasars at z > 5.94

NASA Astrophysics Data System (ADS)

Decarli, Roberto; Walter, Fabian; Venemans, Bram P.; Bañados, Eduardo; Bertoldi, Frank; Carilli, Chris; Fan, Xiaohui; Farina, Emanuele Paolo; Mazzucchelli, Chiara; Riechers, Dominik; Rix, Hans-Walter; Strauss, Michael A.; Wang, Ran; Yang, Yujin

2018-02-01

We present a survey of the [C II] 158 μm line and underlying far-infrared (FIR) dust continuum emission in a sample of 27 z≳ 6 quasars using the Atacama Large Millimeter Array (ALMA) at ∼ 1\\prime\\prime resolution. The [C II] line was significantly detected (at > 5-σ) in 23 sources (85%). We find typical line luminosities of {L}[{{C}{{II}}]}={10}9-10 {L}ȯ , and an average line width of ∼385 {km} {{{s}}}-1. The [C II]-to-far-infrared luminosity ratios ([C II]/FIR) in our sources span one order of magnitude, highlighting a variety of conditions in the star-forming medium. Four quasar host galaxies are clearly resolved in their [C II] emission on a few kpc scales. Basic estimates of the dynamical masses of the host galaxies give masses between 2 × 1010 and 2 × 1011 {M}ȯ , i.e., more than an order of magnitude below what is expected from local scaling relations, given the available limits on the masses of the central black holes (> 3× {10}8 {M}ȯ , assuming Eddington-limited accretion). In stacked ALMA [C II] spectra of individual sources in our sample, we find no evidence of a deviation from a single Gaussian profile. The quasar luminosity does not strongly correlate with either the [C II] luminosity or equivalent width. This survey (with typical on-source integration times of 8 minutes) showcases the unparalleled sensitivity of ALMA at millimeter wavelengths, and offers a unique reference sample for the study of the first massive galaxies in the universe.

Calibrating Star Formation in WISE Using Total Infrared Luminosity

NASA Astrophysics Data System (ADS)

Cluver, M. E.; Jarrett, T. H.; Dale, D. A.; Smith, J.-D. T.; August, Tamlyn; Brown, M. J. I.

2017-11-01

We present accurate resolved WISE photometry of galaxies in the combined SINGS and KINGFISH sample. The luminosities in the W3 12 μm and W4 23 μm bands are calibrated to star formation rates (SFRs) derived using the total infrared luminosity, avoiding UV/optical uncertainties due to dust extinction corrections. The W3 relation has a 1σ scatter of 0.15 dex that is over nearly 5 orders of magnitude in SFR and 12 μm luminosity, and a range in host stellar mass from dwarfs (107 {M}⊙ ) to ˜ 3× {M}{\\star } (1011.5 {M}⊙ ) galaxies. In the absence of deep silicate absorption features and powerful active galactic nuclei, we expect this to be a reliable SFR indicator chiefly due to the broad nature of the W3 band. By contrast, the W4 SFR relation shows more scatter (1σ =0.18 dex). Both relations show reasonable agreement with radio-continuum-derived SFRs and excellent accordance with so-called “hybrid” Hα + 24 μm and FUV+24 μm indicators. Moreover, the WISE SFR relations appear to be insensitive to the metallicity range in the sample. We also compare our results with IRAS-selected luminous infrared galaxies, showing that the WISE relations maintain concordance, but systematically deviate for the most extreme galaxies. Given the all-sky coverage of WISE and the performance of the W3 band as an SFR indicator, the {L}12μ {{m}} SFR relation could be of great use to studies of nearby galaxies and forthcoming large-area surveys at optical and radio wavelengths.

Monitoring the Violent Activity from the Inner Accretion Disk of the Seyfert 1.9 Galaxy NGC 2992 with RXTE

NASA Technical Reports Server (NTRS)

Mruphy, Kendrah D.; Yaqoob, Tahir; Terashima, Yuichi

2007-01-01

We present the results of a one year monitoring campaign of the Seyfert 1.9 galaxy NGC 2992 with RXTE. Historically, the source has been shown to vary dramatically in 2-10 keV flux over timescales of years and was thought to be slowly transitioning between periods of quiescence and active accretion. Our results show that in one year the source continuum flux covered almost the entire historical range, making it unlikely that the low-luminosity states correspond to the accretion mechanism switching off. During flaring episodes we found that a highly redshifted Fe K line appears, implying that the violent activity is occurring in the inner accretion disk, within 100 gravitational radii of the central black hole. We also found that the Compton y parameter for the X-ray continuum remained approximately constant during the large amplitude variability. These observations make NGC 2992 well-suited for future multi-waveband monitoring, as a test-bed for constraining accretion models.

SWIFT Observations of a Far UV Luminosity Component in SS433

NASA Technical Reports Server (NTRS)

Cannizzo, J. K.; Boyd, P. T.; Dolan, J. F.

2007-01-01

SS433 is a binary system showing relativistic Doppler shifts in its two sets of emission lines. The origin of its UV continuum is not well established. We observed SS433 to determine the emission mechanism responsible for its far UV spectrum. The source was observed at several different phases of both its 13 d orbital period and 162.5 d precession period using the UVOT and XRT detector systems on Swift. The far UV spectrum down to 1880 Angstrom lies significantly above the spectral flux distribution predicted by extrapolating the reddened blackbody continuum that fits the spectrum above 3500 Angstroms. The intensity of the far UV flux varies over a period of days and the variability is correlated with the variability of the soft X-ray flux from the source. An emission mechanism in addition to those previously detected in the optical and X-ray regions must exist in the far UV spectrum of SS433.

Lyman continuum leaking AGN in the SSA22 field

NASA Astrophysics Data System (ADS)

Micheva, Genoveva; Iwata, Ikuru; Inoue, Akio K.

2017-02-01

Subaru/SuprimeCam narrow-band photometry of the SSA22 field reveals the presence of four Lyman continuum (LyC) candidates among a sample of 14 active galactic nuclei (AGNs). Two show offsets and likely have stellar LyCin nature or are foreground contaminants. The remaining two LyC candidates are type I AGN. We argue that the average LyC escape fraction of high-redshift, low-luminosity AGN is not likely to be unity, as often assumed in the literature. From direct measurement we obtain the average LyC-to-UV flux density ratio and ionizing emissivity for a number of AGN classes and find it at least a factor of 2 lower than values obtained assuming fesc = 1. Comparing to recent Ly α forest measurements, AGNs at redshift z ˜ 3 make up at most ˜12 per cent and as little as ˜5 per cent of the total ionizing budget. Our results suggest that AGNs are unlikely to dominate the ionization budget of the Universe at high redshifts.

ALMA [N ii] 205 μ m Imaging Spectroscopy of the Interacting Galaxy System BRI 1202-0725 at Redshift 4.7

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

Lu, Nanyao; Xu, C. Kevin; Zhu, Lei

We present the results from Atacama Large Millimeter/submillimeter Array imaging in the [N ii] 205 μ m fine-structure line (hereafter [N ii]) and the underlying continuum of BRI 1202-0725, an interacting galaxy system at z = 4.7, consisting of a quasi-stellar object (QSO), a submillimeter galaxy (SMG), and two Ly α emitters, all within ∼25 kpc of the QSO. We detect the QSO and SMG in both [N ii] and continuum. At the ∼1″ (or 6.6 kpc) resolution, both the QSO and SMG are resolved in [N ii], with the de-convolved major axes of ∼9 and ∼14 kpc, respectively. Inmore » contrast, their continuum emissions are much more compact and unresolved even at an enhanced resolution of ∼0.″7. The ratio of the [N ii] flux to the existing CO(7−6) flux is used to constrain the dust temperature ( T {sub dust}) for a more accurate determination of the FIR luminosity L {sub FIR}. Our best estimated T {sub dust} equals 43 (±2) K for both galaxies (assuming an emissivity index β = 1.8). The resulting L {sub CO(7−6)}/ L {sub FIR} ratios are statistically consistent with that of local luminous infrared galaxies, confirming that L {sub CO(7−6)} traces the star formation (SF) rate (SFR) in these galaxies. We estimate that the ongoing SF of the QSO (SMG) has an SFR of 5.1 (6.9) × 10{sup 3} M {sub ⊙} yr{sup −1} (±30%) assuming Chabrier initial mass function, takes place within a diameter (at half maximum) of 1.3 (1.5) kpc, and will consume the existing 5 (5) × 10{sup 11} M {sub ⊙} of molecular gas in 10 (7) × 10{sup 7} years.« less

The physical and chemical structure of Sagittarius B2. II. Continuum millimeter emission of Sgr B2(M) and Sgr B2(N) with ALMA

NASA Astrophysics Data System (ADS)

Sánchez-Monge, Á.; Schilke, P.; Schmiedeke, A.; Ginsburg, A.; Cesaroni, R.; Lis, D. C.; Qin, S.-L.; Müller, H. S. P.; Bergin, E.; Comito, C.; Möller, Th.

2017-07-01

Context. The two hot molecular cores Sgr B2(M) and Sgr B2(N), which are located at the center of the giant molecular cloud complex Sagittarius B2, have been the targets of numerous spectral line surveys, revealing a rich and complex chemistry. Aims: We seek to characterize the physical and chemical structure of the two high-mass star-forming sites Sgr B2(M) and Sgr B2(N) using high-angular resolution observations at millimeter wavelengths, reaching spatial scales of about 4000 au. Methods: We used the Atacama Large Millimeter/submillimeter Array (ALMA) to perform an unbiased spectral line survey of both regions in the ALMA band 6 with a frequency coverage from 211 GHz to 275 GHz. The achieved angular resolution is 0.̋4, which probes spatial scales of about 4000 au, I.e., able to resolve different cores and fragments. In order to determine the continuum emission in these line-rich sources, we used a new statistical method, STATCONT, which has been applied successfully to this and other ALMA datasets and to synthetic observations. Results: We detect 27 continuum sources in Sgr B2(M) and 20 sources in Sgr B2(N). We study the continuum emission variation across the ALMA band 6 (I.e., spectral index) and compare the ALMA 1.3 mm continuum emission with previous SMA 345 GHz and VLA 40 GHz observations to study the nature of the sources detected. The brightest sources are dominated by (partially optically thick) dust emission, while there is an important degree of contamination from ionized gas free-free emission in weaker sources. While the total mass in Sgr B2(M) is distributed in many fragments, most of the mass in Sgr B2(N) arises from a single object, with filamentary-like structures converging toward the center. There seems to be a lack of low-mass dense cores in both regions. We determine H2 volume densities for the cores of about 107-109 cm-3 (or 105-107 M⊙ pc-3), I.e., one to two orders of magnitude higher than the stellar densities of super star clusters. We perform a statistical study of the chemical content of the identified sources. In general, Sgr B2(N) is chemically richer than Sgr B2(M). The chemically richest sources have about 100 lines per GHz and the fraction of luminosity contained in spectral lines at millimeter wavelengths with respect to the total luminosity is about 20%-40%. There seems to be a correlation between the chemical richness and the mass of the fragments, where more massive clumps are more chemically rich. Both Sgr B2(N) and Sgr B2(M) harbor a cluster of hot molecular cores. We compare the continuum images with predictions from a detailed 3D radiative transfer model that reproduces the structure of Sgr B2 from 45 pc down to 100 au. Conclusions: This ALMA dataset, together with other ongoing observational projects in the range 5 GHz to 200 GHz, better constrain the 3D structure of Sgr B2 and allow us to understand its physical and chemical structure. FITS files of the continuum images as well as the spectral index are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A6

Baldwin Effect and Additional BLR Component in AGN with Superluminal Jets

NASA Astrophysics Data System (ADS)

Patiño Álvarez, Víctor; Torrealba, Janet; Chavushyan, Vahram; Cruz González, Irene; Arshakian, Tigran; León Tavares, Jonathan; Popovic, Luka

2016-06-01

We study the Baldwin Effect (BE) in 96 core-jet blazars with optical and ultraviolet spectroscopic data from a radio-loud AGN sample obtained from the MOJAVE 2cm survey. A statistical analysis is presented of the equivalent widths W_lambda of emission lines H beta 4861, Mg II 2798, C IV 1549, and continuum luminosities at 5100, 3000, and 1350 angstroms. The BE is found statistically significant (with confidence level c.l. > 95%) in H beta and C IV emission lines, while for Mg II the trend is slightly less significant (c.l. = 94.5%). The slopes of the BE in the studied samples for H beta and Mg II are found steeper and with statistically significant difference than those of a comparison radio-quiet sample. We present simulations of the expected BE slopes produced by the contribution to the total continuum of the non-thermal boosted emission from the relativistic jet, and by variability of the continuum components. We find that the slopes of the BE between radio-quiet and radio-loud AGN should not be different, under the assumption that the broad line is only being emitted by the canonical broad line region around the black hole. We discuss that the BE slope steepening in radio AGN is due to a jet associated broad-line region.

Observations of Herbig Ae/Be Stars with Herschel/PACS: The Atomic and Molecular Contents of Their Protoplanetary Discs

NASA Technical Reports Server (NTRS)

Meeus, G.; Montesinos, B.; Mendigutia, I.; Kamp, I.; Thi, W. F.; Eiroa, C.; Grady, C. A.; Mathews, G.; Sandell, G.; Martin-Zaidi, C.;

Level Density in the Complex Scaling Method

NASA Astrophysics Data System (ADS)

Suzuki, R.; Myo, T.; Katō, K.

2005-06-01

It is shown that the continuum level density (CLD) at unbound energies can be calculated with the complex scaling method (CSM), in which the energy spectra of bound states, resonances and continuum states are obtained in terms of L(2) basis functions. In this method, the extended completeness relation is applied to the calculation of the Green functions, and the continuum-state part is approximately expressed in terms of discretized complex scaled continuum solutions. The obtained result is compared with the CLD calculated exactly from the scattering phase shift. The discretization in the CSM is shown to give a very good description of continuum states. We discuss how the scattering phase shifts can inversely be calculated from the discretized CLD using a basis function technique in the CSM.

CONSTRAINTS ON THE FAINT END OF THE QUASAR LUMINOSITY FUNCTION AT z {approx} 5 IN THE COSMOS FIELD

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

Ikeda, H.; Matsuoka, K.; Kajisawa, M.

2012-09-10

We present the result of our low-luminosity quasar survey in the redshift range of 4.5 {approx}< z {approx}< 5.5 in the COSMOS field. Using the COSMOS photometric catalog, we selected 15 quasar candidates with 22 < i' < 24 at z {approx} 5 that are {approx}3 mag fainter than the Sloan Digital Sky Survey quasars in the same redshift range. We obtained optical spectra for 14 of the 15 candidates using FOCAS on the Subaru Telescope and did not identify any low-luminosity type-1 quasars at z {approx} 5, while a low-luminosity type-2 quasar at z {approx} 5.07 was discovered. Inmore » order to constrain the faint end of the quasar luminosity function at z {approx} 5, we calculated the 1{sigma} confidence upper limits of the space density of type-1 quasars. As a result, the 1{sigma} confidence upper limits on the quasar space density are {Phi} < 1.33 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -24.52 < M{sub 1450} < -23.52 and {Phi} < 2.88 Multiplication-Sign 10{sup -7} Mpc{sup -3} mag{sup -1} for -23.52 < M{sub 1450} < -22.52. The inferred 1{sigma} confidence upper limits of the space density are then used to provide constraints on the faint-end slope and the break absolute magnitude of the quasar luminosity function at z {approx} 5. We find that the quasar space density decreases gradually as a function of redshift at low luminosity (M{sub 1450} {approx} -23), being similar to the trend found for quasars with high luminosity (M{sub 1450} < -26). This result is consistent with the so-called downsizing evolution of quasars seen at lower redshifts.« less

Early Science with the Large Millimeter Telescope: CO and [C II] Emission in the z = 4.3 AzTEC J095942.9+022938 (COSMOS AzTEC-1)

NASA Astrophysics Data System (ADS)

Yun, Min S.; Aretxaga, I.; Gurwell, M. A.; Hughes, D. H.; Montaña, A.; Narayanan, G.; Rosa-González, D.; Sánchez-Argüelles, D.; Schloerb, F. P.; Snell, R. L.; Vega, O.; Wilson, G. W.; Zeballos, M.; Chavez, M.; Cybulski, R.; Díaz-Santos, T.; De La Luz, V.; Erickson, N.; Ferrusca, D.; Gim, H. B.; Heyer, M. H.; Iono, D.; Pope, A.; Rogstad, S. M.; Scott, K. S.; Souccar, K.; Terlevich, E.; Terlevich, R.; Wilner, D.; Zavala, J. A.

2015-12-01

Measuring redshifted CO line emission is an unambiguous method for obtaining an accurate redshift and total cold gas content of optically faint, dusty starburst systems. Here, we report the first successful spectroscopic redshift determination of AzTEC J095942.9+022938 (`COSMOS AzTEC-1'), the brightest 1.1 mm continuum source found in the AzTEC/James Clerk Maxwell Telescope survey (Scott et al.), through a clear detection of the redshifted CO (4-3) and CO (5-4) lines using the Redshift Search Receiver on the Large Millimeter Telescope. The CO redshift of z = 4.3420 ± 0.0004 is confirmed by the detection of the redshifted 158 μm [C II] line using the Submillimeter Array. The new redshift and Herschel photometry yield LFIR = (1.1 ± 0.1) × 1013 L⊙ and SFR ≈ 1300 M⊙ yr-1. Its molecular gas mass derived using the ultraluminous infrared galaxy conversion factor is 1.4 ± 0.2 × 1011M⊙ while the total interstellar medium mass derived from the 1.1 mm dust continuum is 3.7 ± 0.7 × 1011M⊙ assuming Td = 35 K. Our dynamical mass analysis suggests that the compact gas disc (r ≈ 1.1 kpc, inferred from dust continuum and spectral energy distribution analysis) has to be nearly face-on, providing a natural explanation for the uncommonly bright, compact stellar light seen by the HST. The [C II] line luminosity L_[C II]= 7.8± 1.1 × 10^9 L_{⊙} is remarkably high, but it is only 0.04 per cent of the total IR luminosity. AzTEC COSMOS-1 and other high redshift sources with a spatially resolved size extend the tight trend seen between [C II]/FIR ratio and ΣFIR among IR-bright galaxies reported by Díaz-Santos et al. by more than an order of magnitude, supporting the explanation that the higher intensity of the IR radiation field is responsible for the `[C II] deficiency' seen among luminous starburst galaxies.

Weak and Compact Radio Emission in Early High-Mass Star Forming Regions

NASA Astrophysics Data System (ADS)

Rosero, Viviana; P. Hofner, M. Claussen, S. Kurtz, R. Cesaroni, E. D. Araya, C. Carrasco-González, L. F. Rodríguez, K. M. Menten, F. Wyrowski, L. Loinard, S. P. Ellingsen

2018-01-01

High-mass protostars are difficult to detect: they have short evolutionary timescales, they tend to be located at large distances, and they are usually embedded within complicated cluster environments. In this work, we aimed to identify and analyze candidates at the earliest stages of high-mass star formation, where only low-level (< 1 mJy) radio emission is expected. We used the Karl G. Jansky Very Large Array to achieve one of the most sensitive (image RMS < 3 -- 10 μJy/beam) centimeter continuum surveys towards high-mass star forming regions to date, with observations at 1.3 and 6 cm and an angular resolution < 0.5". The sample is composed of cold molecular clumps with and without infrared sources (CMC--IRs and CMCs, respectively) and hot molecular cores (HMCs), covering a wide range of parameters such as bolometric luminosity and distance. We detected 70 radio continuum sources that are associated with dust clumps, most of which are weak and compact. We detected centimeter wavelength sources in 100% of our HMCs, which is a higher fraction than previously expected and suggests that radio continuum may be detectable at weak levels in all HMCs. The lack of radio detections for some objects in the sample (including most CMCs) contributes strong evidence that these are prestellar clumps, providing interesting constraints and ideal follow up candidates for studies of the earliest stages of high-mass stars. Our results show further evidence for an evolutionary sequence in the formation of high-mass stars, from starless cores (i.e., CMCs) to relatively more evolved ones (i.e., HMCs). Many of our detections have morphologies and other observational parameters that resemble collimated ionized jets, which is highly relevant for recent theoretical models based on core accretion that predict that the first stages of ionization from high-mass stars are in the form of jets. Additionally, we found that properties of ionized jets from low and high-mass stars are extremely well correlated; our data improves upon previous studies of this nature and provides further evidence of a common origin for jets of any luminosity.

Night Airglow Observations from Orbiting Spacecraft Compared with Measurements from Rockets.

PubMed

Koomen, M J; Gulledge, I S; Packer, D M; Tousey, R

1963-06-07

A luminous band around the night-time horizon, observed from orbiting capsules by J. H. Glenn and M. S. Carpenter, and identified as the horizon enhancement of the night airglow, is detected regularly in rocket-borne studies of night airglow. Values of luminance and dip angle of this band derived from Carpenter's observations agree remarkably well with values obtained from rocket data. The rocket results, however, do not support Carpenter's observation that the emission which he saw was largely the atomic oxygen line at 5577 A, but assign the principal luminosity to the green continuum.

An Interferometric Study of the Post-AGB Binary 89 Herculis. 1: Spatially Resolving the Continuum Circumstellar Environment at Optical and Near-IR Wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array

DTIC Science & Technology

2013-01-01

evolution of binaries as well as the structure of circumstellar disks. Aims. A multiwavelength high angular resolution study of the prototypical object...optical to mid-IR wave- lengths. For YSOs this has led to the discovery of an empiri- cal size-luminosity relation (Millan-Gabet et al. 2001; Monnier...Millan-Gabet 2002), which in turn has led to the current paradigm (Dullemond & Monnier 2010) of a passive dusty disk with an optically thin cavity and the

Clustering, cosmology and a new era of black hole demographics- I. The conditional luminosity function of active galactic nuclei

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2017-01-01

Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to z ˜ 5. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGN inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGN and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the conditional luminosity function (CLF) of AGN at a specific z. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method is illustrated at z ≈ 0 and 0.9 using the limited data that are currently available, and a clear luminosity dependence in the AGN bias and mean halo mass is predicted at both z, supporting the idea that there are at least two different modes of AGN triggering. In addition, the CLF predicts that z ≈ 0.9 quasars may be commonly hosted by haloes with Mh ˜ 1014 M⊙. These `young cluster' environments may provide the necessary interactions between gas-rich galaxies to fuel luminous accretion. The results derived from this method will be useful to populate AGN of different luminosities in cosmological simulations.

Keck Deep Fields. II. The Ultraviolet Galaxy Luminosity Function at z ~ 4, 3, and 2

NASA Astrophysics Data System (ADS)

Sawicki, Marcin; Thompson, David

2006-05-01

We use very deep UnGRI multifield imaging obtained at the Keck telescope to study the evolution of the rest-frame 1700 Å galaxy luminosity function as the universe doubles its age from z~4 to ~2. We use exactly the same filters and color-color selection as those used by the Steidel team but probe significantly fainter limits, well below L*. The depth of our imaging allows us to constrain the faint end of the luminosity function, reaching M1700~-18.5 at z~3 (equivalent to ~1 Msolar yr-1), accounting for both N1/2 uncertainty in the number of galaxies and cosmic variance. We carefully examine many potential sources of systematic bias in our LF measurements before drawing the following conclusions. We find that the luminosity function of Lyman break galaxies evolves with time and that this evolution is differential with luminosity. The result is best constrained between the epochs at z~4 and ~3, where we find that the number density of sub-L* galaxies increases with time by at least a factor of 2.3 (11 σ statistical confidence); while the faint end of the LF evolves, the bright end appears to remain virtually unchanged, indicating that there may be differential, luminosity-dependent evolution (98.5% statistical probability). Potential systematic biases restrict our ability to draw strong conclusions about continued evolution of the luminosity function to lower redshifts, z~2.2 and ~1.7, but, nevertheless, it appears certain that the number density of z~2.2 galaxies at all luminosities we studied, -22>M1700>-18, is at least as high as that of their counterparts at z~3. While it is not yet clear what mechanism underlies the observed evolution, the fact that this evolution is differential with luminosity opens up new avenues of improving our understanding of how galaxies form and evolve at high redshift. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA and was made possible by the generous financial support of the W. M. Keck Foundation.

Correlation function of the luminosity distances

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

Biern, Sang Gyu; Yoo, Jaiyul, E-mail: sgbiern@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch

We present the correlation function of the luminosity distances in a flat ΛCDM universe. Decomposing the luminosity distance fluctuation into the velocity, the gravitational potential, and the lensing contributions in linear perturbation theory, we study their individual contributions to the correlation function. The lensing contribution is important at large redshift ( z ∼> 0.5) but only for small angular separation (θ ∼< 3°), while the velocity contribution dominates over the other contributions at low redshift or at larger separation. However, the gravitational potential contribution is always subdominant at all scale, if the correct gauge-invariant expression is used. The correlation functionmore » of the luminosity distances depends significantly on the matter content, especially for the lensing contribution, thus providing a novel tool of estimating cosmological parameters.« less

Star formation in the inner galaxy: A far-infrared and radio study of two H2 regions

NASA Technical Reports Server (NTRS)

Lester, D. F.; Dinerstein, H. L.; Werner, M. W.; Harvey, P. M.; Evans, N. J.; Brown, R. L.

1985-01-01

Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy HII regions G30.8-0.0 (in the W43 complex) and G25.4-0.2, along with radio and molecular line measurements at selected positions. The purpose of this study is an effort to understand star formation in the molecular ring at 5 kpc in galactic radius. Measurements at several far infrared wavelengths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. Using radio recombination line and CO line data for G25.4-0.2, the distance ambiguity for this source is resolved. The large distance previously ascribed to the entire complex is found to apply to only one of the two main components. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright HII regions. Using the revised distances of 4.3 kpc for G25.4SE and 12 kpc for G25.4NW, it is found that the latter, which is apparently the fainter of the two sources, is actually the more luminous. The ratio of total luminosity to ionizing luminosity is very similar to that of HII regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated.

Evolution of the Blue and Far-Infrared Galaxy Luminosity Functions

NASA Technical Reports Server (NTRS)

Lonsdale, Carol J.; Chokshi, Arati

1993-01-01

The space density of blue-selected galaxies at moderate redshifts is determined here directly by deriving the luminosity function. Evidence is found for density evolution for moderate luminosity galaxies at a rate of (1+z) exp delta, with a best fit of delta + 4 +/- 2, between the current epoch and Z greater than about 0.1. At M(b) less than -22 evidence is found for about 0.5-1.5 mag of luminosity evolution in addition to the density evolution, corresponding to an evolutionary rate of about (1+z) exp gamma, with gamma = 0.5-2.5, but a redshift of about 0.4. Assuming a steeper faint end slope of alpha = -1.3 similar to that observed in the Virgo cluster, could explain the data with a luminosity evolution rate of gamma = 1-2, without need for any density evolution. Acceptable fits are found by comparing composite density and luminosity evolution models to faint IRAS 60 micron source counts, implying that the blue and far-IR evolutionary rates may be similar.

The Lyman continuum escape fraction of low mass star-forming galaxies at z~1.

NASA Astrophysics Data System (ADS)

Rutkowski, Michael J.; Scarlata, Claudia; Haardt, Francesco; Siana, Brian D.; Rafelski, Marc; Henry, Alaina L.; Hayes, Matthew; Salvato, Mara; Pahl, Anthony; Mehta, Vihang; Beck, Melanie; Malkan, Matthew Arnold; Teplitz, Harry I.

2016-01-01

Star-forming galaxies (SFGs) in the high redshift universe (z>6) are believed to ionize neutral hydrogen in the intergalactic medium during the epoch of reionization. We tested this assumption by studying likely analogs of these SFGs in archival HST grism spectroscopy with GALEX UV and ground-based optical images at the redshift range in which we can directly measure the rest-frame Lyman continuum (λ<912Å, LyC) emission. We selected ~1400 SFGs for study on the presence of strong Hα emission and strongly selected against those SFGs whose GALEX FUV photometry could be contaminated by low redshift interlopers along the line of sight to produce a sample of ~600 z~1 SFGs. We made no unambiguous detection of escaping Lyman continuum radiation in individual galaxies in this sample, and stacked the individual non-detections in order to constrain the absolute Lyman continuum escape fraction, fesc<2% (3σ). We sub-divided this sample and stacked SFGs to measure upper limits to fesc with respect to stellar mass,luminosity and relative orientation. For z~1 high Hα equivalent width (EW>200Å) SFGs, we found for the first time an upper limit to fesc<9%. We discuss the implications of these limits for the ionizing emissivity of high redshift SFGs during the epoch of reionization. We conclude that reionization by SFGs is only marginally consistent with independent Planck observations of the CMB electron scattering opacity unless the LyC escape fraction of SFGs increases with redshift and an unobserved population of faint (MUV<-13 AB) SFGs contributes significantly to the UV background.

The luminosity function at the end of the main sequence: Results of a deep, large-area, CCD survey for cool dwarfs

NASA Technical Reports Server (NTRS)

Kirkpatrick, J. Davy; Mcgraw, John T.; Hess, Thomas R.; Liebert, James; Mccarthy, Donald W., Jr.

1994-01-01

The luminosity function at the end of the main sequence is determined from V, R, and I data taken by the charge coupled devices (CCD)/Transit Instrument, a dedicated telescope surveying an 8.25 min wide strip of sky centered at delta = +28 deg, thus sampling Galactic latitudes of +90 deg down to -35 deg. A selection of 133 objects chosen via R - I and V - I colors has been observed spectroscopically at the 4.5 m Multiple Mirror Telescope to assess contributions by giants and subdwarfs and to verify that the reddest targets are objects of extremely late spectral class. Eighteen dwarfs of type M6 or later have been discovered, with the latest being of type M8.5. Data used for the determination of the luminosity function cover 27.3 sq. deg down to a completeness limit of R = 19.0. This luminosity function, computed at V, I, and bolometric magnitudes, shows an increase at the lowest luminosities, corresponding to spectral types later than M6- an effect suggested in earlier work by Reid & Gilmore and Legget & Hawkins. When the luminosity function is segregated into north Galactic and south Galactic portions, it is found that the upturn at faint magnitudes exists only in the southern sample. In fact, no dwarfs with M(sub I) is greater than or equal to 12.0 are found within the limiting volume of the 19.4 sq deg northern sample, in stark contrast to the smaller 7.9 sq deg area at southerly latitudes where seven such dwarfs are found. This fact, combined with the fact that the Sun is located approximately 10-40 pc north of the midplane, suggests that the latest dwarfs are part of a young population with a scale height much smaller than the 350 pc value generally adopted for other M dwarfs. These objects comprise a young population either because the lower metallicities prevelant at earlier epochs inhibited the formation of late M dwarfs or because the older counterparts of this population have cooled beyond current detection limits. The latter scenario would hold if these late-type M dwarfs are substellar. The luminosity function data together with an empirical derivation of the mass-luminosity relation (from Henry & McCarthy) are used to compute a mass function independent of theory. This mass function increases toward the end of the main sequence, but the observed density of M dwarfs is still insufficient to account for the missing mass. If the increases seen in the luminosity and mass functions are indicative of a large, unseen, substellar population, brown dwarfs may yet add significantly to the mass of the Galaxy.

Models of the hard X-ray spectrum of AM Herculis and implications for the accretion rate

NASA Technical Reports Server (NTRS)

Swank, J. H.; Fabian, A. C.; Ross, R. R.

1983-01-01

Phenomenological fits to the hard X-ray spectrum of AM Herculis left unexplained the high equivalent width (0.8 + or - 0.1 keV) of Fe K alpha emission. A purely thermal origin implies a much steeper spectrum than was observed. With Monte Carlo calculations, scattering and fluorescent line production in a cold or partially ionized accretion column of hard X-rays emitted at the base were investigated. The strength of the iron emission and the flat spectral continuum can be explained by the effects of fluorescence and absorption within the accretion column and the surface of the white dwarf on a thermal X-ray spectrum. Thomson optical depths across the column in the range 0.2 to 0.7 are acceptable. The accretion rate and gravitational power can be deduced from the optical depth across the column, if the column size is known, and, together with the observed hard X-ray and polarized light luminosities, imply a lower limit for the luminosity in the UV to soft X-ray range, for which the observations give model-dependent values. Estimates of the column size differ by a factor of 40. Small spot sizes and low luminosities would be consistent with the soft component being the expected reprocessed bremsstrahlung and cyclotron radiation, although the constraint of matching the spectrum confines one to solutions with fluxes exceeding 20% the Eddington limits.

The kinetically dominated quasar 3C 418

NASA Astrophysics Data System (ADS)

Punsly, Brian; Kharb, Preeti

2017-06-01

The existence of quasars that are kinetically dominated, where the jet kinetic luminosity, Q, is larger than the total (infrared to X-ray) thermal luminosity of the accretion flow, Lbol, provides a strong constraint on the fundamental physics of relativistic jet formation. Since quasars have high values of Lbol by definition, only ˜10 kinetically dominated quasars (with \\overline{Q}/L_{bol}>1) have been found, where \\overline{Q} is the long-term time-averaged jet power. We use low-frequency (151 MHz-1.66 GHz) observations of the quasar 3C 418 to determine \\overline{Q}≈ 5.5 ± 1.3 × 10^{46} {erg s^{-1}}. Analysis of the rest-frame ultraviolet spectrum indicates that this equates to 0.57 ± 0.28 times the Eddington luminosity of the central supermassive black hole and \\overline{Q}/L_{bol} ≈ 4.8 ± 3.1, making 3C 418 one of the most kinetically dominated quasars found to date. It is shown that this maximal \\overline{Q}/L_{bol} is consistent with models of magnetically arrested accretion of jet production in which the jet production reproduces the observed trend of a decrement in the extreme ultraviolet continuum as the jet power increases. This maximal condition corresponds to an almost complete saturation of the inner accretion flow with vertical large-scale magnetic flux (maximum saturation).

ROSAT HRI and ASCA Observations of the Spiral Galaxy NGC 6946 and its Northeast Complex of Luminous Supernova Remnants

NASA Technical Reports Server (NTRS)

Schlegel, E.; Swank, Jean (Technical Monitor)

2001-01-01

Analysis of 80 ks ASCA (Advanced Satellite for Cosmology and Astrophysics) and 60 ks ROSAT HRI (High Resolution Image) observations of the face-on spiral galaxy NGC 6946 are presented. The ASCA image is the first observation of this galaxy above approximately 2 keV. Diffuse emission may be present in the inner approximately 4' extending to energies above approximately 2-3 keV. In the HRI data, 14 pointlike sources are detected, the brightest two being a source very close to the nucleus and a source to the northeast that corresponds to a luminous complex of interacting supernova remnants (SNRs). We detect a point source that lies approximately 30" west of the SNR complex but with a luminosity -1115 of the SNR complex. None of the point sources show evidence of strong variability; weak variability would escape our detection. The ASCA spectrum of the SNR complex shows evidence for an emission line at approximately 0.9 keV that could be either Ne IX at approximately 0.915 keV or a blend of ion stages of Fe L-shell emission if the continuum is fitted with a power law. However, a two-component, Raymond-Smith thermal spectrum with no lines gives an equally valid continuum fit and may be more physically plausible given the observed spectrum below 3 keV. Adopting this latter model, we derive a density for the SNR complex of 10-35 cm(exp -3), consistent with estimates inferred from optical emission-line ratios. The complex's extraordinary X-ray luminosity may be related more to the high density of the surrounding medium than to a small but intense interaction region where two of the complex's SNRs are apparently colliding.

Physical Properties of 15 Quasars at z ≳ 6.5

NASA Astrophysics Data System (ADS)

Mazzucchelli, C.; Bañados, E.; Venemans, B. P.; Decarli, R.; Farina, E. P.; Walter, F.; Eilers, A.-C.; Rix, H.-W.; Simcoe, R.; Stern, D.; Fan, X.; Schlafly, E.; De Rosa, G.; Hennawi, J.; Chambers, K. C.; Greiner, J.; Burgett, W.; Draper, P. W.; Kaiser, N.; Kudritzki, R.-P.; Magnier, E.; Metcalfe, N.; Waters, C.; Wainscoat, R. J.

2017-11-01

Quasars are galaxies hosting accreting supermassive black holes; due to their brightness, they are unique probes of the early universe. To date, only a few quasars have been reported at z> 6.5 (<800 Myr after the big bang). In this work, we present six additional z≳ 6.5 quasars discovered using the Pan-STARRS1 survey. We use a sample of 15 z≳ 6.5 quasars to perform a homogeneous and comprehensive analysis of this highest-redshift quasar population. We report four main results: (1) the majority of z≳ 6.5 quasars show large blueshifts of the broad C IV λ1549 emission line compared to the systemic redshift of the quasars, with a median value ˜3× higher than a quasar sample at z˜ 1; (2) we estimate the quasars’ black hole masses ({M}{BH} ˜ (0.3-5) × 109 M ⊙) via modeling of the Mg II λ2798 emission line and rest-frame UV continuum and find that quasars at high redshift accrete their material (with < ({L}{bol}/{L}{Edd})> =0.39) at a rate comparable to a luminosity-matched sample at lower redshift, albeit with significant scatter (0.4 dex); (3) we recover no evolution of the Fe II/Mg II abundance ratio with cosmic time; and (4) we derive near-zone sizes and, together with measurements for z˜ 6 quasars from recent work, confirm a shallow evolution of the decreasing quasar near-zone sizes with redshift. Finally, we present new millimeter observations of the [C II] 158 μm emission line and underlying dust continuum from NOEMA for four quasars and provide new accurate redshifts and [C II]/infrared luminosity estimates. The analysis presented here shows the large range of properties of the most distant quasars.

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

Ma, Jingzhe; Gonzalez, Anthony H.; Vieira, J. D.

We present Chandra ACIS-S and Australia Telescope Compact Array (ATCA) radio continuum observations of the strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter SPT0346-52) at z = 5.656. This galaxy has also been observed with ALMA, HST , Spitzer , Herschel , Atacama Pathfinder EXperiment, and the Very Large Telescope. Previous observations indicate that if the infrared (IR) emission is driven by star formation, then the inferred lensing-corrected star formation rate (SFR) (∼4500 M {sub ☉} yr{sup −1}) and SFR surface density Σ{sub SFR} (∼2000 M {sub ☉} yr{sup −1} kpc{sup −2}) are both exceptionally high. It remained unclear frommore » the previous data, however, whether a central active galactic nucleus (AGN) contributes appreciably to the IR luminosity. The Chandra upper limit shows that SPT0346-52 is consistent with being star formation dominated in the X-ray, and any AGN contribution to the IR emission is negligible. The ATCA radio continuum upper limits are also consistent with the FIR-to-radio correlation for star-forming galaxies with no indication of an additional AGN contribution. The observed prodigious intrinsic IR luminosity of (3.6 ± 0.3) × 10{sup 13} L {sub ☉} originates almost solely from vigorous star formation activity. With an intrinsic source size of 0.61 ± 0.03 kpc, SPT0346-52 is confirmed to have one of the highest Σ{sub SFR} of any known galaxy. This high Σ{sub SFR}, which approaches the Eddington limit for a radiation pressure supported starburst, may be explained by a combination of very high star formation efficiency and gas fraction.« less

Resolved Structure of the Arp 220 Nuclei at λ ≈ 3 mm

NASA Astrophysics Data System (ADS)

Sakamoto, Kazushi; Aalto, Susanne; Barcos-Muñoz, Loreto; Costagliola, Francesco; Evans, Aaron S.; Harada, Nanase; Martín, Sergio; Wiedner, Martina; Wilner, David

2017-11-01

We analyze the 3 mm emission of the ultraluminous infrared galaxy Arp 220 for the spatially resolved structure and the spectral properties of the merger nuclei. ALMA archival data at ˜0.″05 resolution are used for extensive visibility fitting and deep imaging of the continuum emission. The data are fitted well by two concentric components for each nucleus, such as two Gaussians or one Gaussian plus one exponential disk. The larger components in the individual nuclei are similar in shape and extent, ˜100-150 pc, to the centimeter wave emission due to supernovae. They are therefore identified with the known starburst nuclear disks. The smaller components in both nuclei have about a few 10 pc sizes and peak brightness temperatures ({T}{{b}}) more than twice higher than those in previous single-Gaussian fitting. They correspond to the dust emission that we find centrally concentrated in both nuclei by subtracting the plasma emission measured at 33 GHz. The dust emission in the western nucleus is found to have a peak {T}{{b}}≈ 530 K and an FWHM of about 20 pc. This component is estimated to have a bolometric luminosity on the order of {10}12.5 {L}⊙ and a 20 pc scale luminosity surface density {10}15.5 {{L}}⊙ {{{k}}{{p}}{{c}}}-2. A luminous active galactic nucleus is a plausible energy source for these high values while other explanations remain to be explored. Our continuum image also reveals a third structural component of the western nucleus—a pair of faint spurs perpendicular to the disk major axis. We attribute it to a bipolar outflow from the highly inclined (I≈ 60^\\circ ) western nuclear disk.

Observations of CO isotopic emission and the far-infrared continuum of Centaurus A

NASA Technical Reports Server (NTRS)

Eckart, A.; Cameron, M.; Rothermel, H.; Wild, W.; Zinnecker, H.; Olberg, M.; Rydbeck, G.; Wiklind, T.

1990-01-01

Researchers present maps of the CO-12(1=0) line and the 100 micron and 50 micron far-infrared emission of Centaurus A, as well as measurements of the CO-12(2-1), CO-13(1-0), and the C-18O(1-0) lines at selected positions. The observations were taken with the Swedish-ESO Submillimeter Telescope (SEST) and the CPC instrument on board the Infrared Astronomy Satellite (IRAS). The millimeter data show that the bulk molecular material is closely associated with the dust lane and contained in a disk of about 180 seconds diameter and a total molecular mass of about 2 x 10 to the 8th power solar mass. The total molecular mass of the disk and bulge is of the order of 3 x 10 to the 8th power solar mass. The molecular gas in the nucleus is warm with a kinetic temperature of the order of 15 K and a number density of 10 to the 3rd power to 3 x 10 to the 4th power cm(-3). Absorption features in the CO-12 and CO-13 lines against the nuclear continuum emission indicate that the properties of giant molecular clouds are comparable to those of the Galaxy. The far-infrared data show that to a good approximation the dust temperature is constant across the dust lane at a value of about 42 K. The ratio between the far-infrared luminosity and the total molecular mass is 18 solar luminosity/solar mass and close to the mean value obtained for isolated galaxies. A comparison of the CO-12(1-0) and the far-infrared data indicates that a considerable amount of the far-infrared emission is not intimately associated with massive star formation.

The Diversity of Diffuse Ly α Nebulae around Star-forming Galaxies at High Redshift

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

Xue, Rui; Lee, Kyoung-Soo; Dey, Arjun

2017-03-10

We report the detection of diffuse Ly α emission, or Ly α halos (LAHs), around star-forming galaxies at z ≈ 3.78 and 2.66 in the NOAO Deep Wide-Field Survey Boötes field. Our samples consist of a total of ∼1400 galaxies, within two separate regions containing spectroscopically confirmed galaxy overdensities. They provide a unique opportunity to investigate how the LAH characteristics vary with host galaxy large-scale environment and physical properties. We stack Ly α images of different samples defined by these properties and measure their median LAH sizes by decomposing the stacked Ly α radial profile into a compact galaxy-like andmore » an extended halo-like component. We find that the exponential scale-length of LAHs depends on UV continuum and Ly α luminosities, but not on Ly α equivalent widths or galaxy overdensity parameters. The full samples, which are dominated by low UV-continuum luminosity Ly α emitters ( M {sub UV} ≳ −21), exhibit LAH sizes of 5–6 kpc. However, the most UV- or Ly α- luminous galaxies have more extended halos with scale-lengths of 7–9 kpc. The stacked Ly α radial profiles decline more steeply than recent theoretical predictions that include the contributions from gravitational cooling of infalling gas and from low-level star formation in satellites. However, the LAH extent matches what one would expect for photons produced in the galaxy and then resonantly scattered by gas in an outflowing envelope. The observed trends of LAH sizes with host galaxy properties suggest that the physical conditions of the circumgalactic medium (covering fraction, H i column density, and outflow velocity) change with halo mass and/or star formation rates.« less

The global star formation law of galaxies revisited in the radio continuum

NASA Astrophysics Data System (ADS)

Liu, LiJie; Gao, Yu

2012-02-01

We study the global star formation law, the relation between the gas and star formation rate (SFR) in a sample of 130 local galaxies with infrared (IR) luminosities spanning over three orders of magnitude (109-1012 L⊙), which includes 91 normal spiral galaxies and 39 (ultra)luminous IR galaxies [(U)LIRGs]. We derive their total (atomic and molecular) gas and dense molecular gas masses using newly available HI, CO and HCN data from the literature. The SFR of galaxies is determined from total IR (8-1000 μm) and 1.4 GHz radio continuum (RC) luminosities. The galaxy disk sizes are defined by the de-convolved elliptical Gaussian FWHM of the RC maps. We derive the galaxy disk-averaged SFRs and various gas surface densities, and investigate their relationships. We find that the galaxy disk-averaged surface density of dense molecular gas mass has the tightest correlation with that of SFR (scatter ˜0.26 dex), and is linear in log-log space (power-law slope of N=1.03±0.02) across the full galaxy sample. The correlation between the total gas and SFR surface densities for the full sample has a somewhat larger scatter (˜0.48 dex), and is best fit by a power-law with slope 1.45±0.02. However, the slope changes from ˜1 when only normal spirals are considered, to ˜1.5 when more and more (U)LIRGs are included in the fitting. When different CO-to-H2 conversion factors are used to infer molecular gas masses for normal galaxies and (U)LIRGs, the bi-modal relations claimed recently in CO observations of high-redshift galaxies appear to also exist in local populations of star-forming galaxies.

The Diversity of Diffuse Lyα Nebulae around Star-forming Galaxies at High Redshift

NASA Astrophysics Data System (ADS)

Xue, Rui; Lee, Kyoung-Soo; Dey, Arjun; Reddy, Naveen; Hong, Sungryong; Prescott, Moire K. M.; Inami, Hanae; Jannuzi, Buell T.; Gonzalez, Anthony H.

2017-03-01

We report the detection of diffuse Lyα emission, or Lyα halos (LAHs), around star-forming galaxies at z ≈ 3.78 and 2.66 in the NOAO Deep Wide-Field Survey Boötes field. Our samples consist of a total of ˜1400 galaxies, within two separate regions containing spectroscopically confirmed galaxy overdensities. They provide a unique opportunity to investigate how the LAH characteristics vary with host galaxy large-scale environment and physical properties. We stack Lyα images of different samples defined by these properties and measure their median LAH sizes by decomposing the stacked Lyα radial profile into a compact galaxy-like and an extended halo-like component. We find that the exponential scale-length of LAHs depends on UV continuum and Lyα luminosities, but not on Lyα equivalent widths or galaxy overdensity parameters. The full samples, which are dominated by low UV-continuum luminosity Lyα emitters (M UV ≳ -21), exhibit LAH sizes of 5-6 kpc. However, the most UV- or Lyα-luminous galaxies have more extended halos with scale-lengths of 7-9 kpc. The stacked Lyα radial profiles decline more steeply than recent theoretical predictions that include the contributions from gravitational cooling of infalling gas and from low-level star formation in satellites. However, the LAH extent matches what one would expect for photons produced in the galaxy and then resonantly scattered by gas in an outflowing envelope. The observed trends of LAH sizes with host galaxy properties suggest that the physical conditions of the circumgalactic medium (covering fraction, H I column density, and outflow velocity) change with halo mass and/or star formation rates.

ALMA 0.1–0.2 arcsec resolution imaging of the NGC 1068 Nucleus: compact dense molecular gas emission at the putative AGN location

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

Imanishi, Masatoshi; Nakanishi, Kouichiro; Izumi, Takuma, E-mail: masa.imanishi@nao.ac.jp

2016-05-01

We present the results of our ALMA Cycle 2 high angular resolution (0.″1–0.″2) observations of the nuclear region of the nearby well-studied type-2 active galactic nucleus (AGN), NGC 1068, at HCN J = 3–2 and HCO{sup +} J = 3–2 emission lines. For the first time, due to a higher angular resolution than previous studies, we clearly detected dense molecular gas emission at the putative AGN location, identified as a ∼1.1 mm (∼266 GHz) continuum emission peak, by separating this emission from brighter emission located at 0.″5–2.″0 on the eastern and western sides of the AGN. The estimated intrinsic molecularmore » emission size and dense molecular mass, which are thought to be associated with the putative dusty molecular torus around an AGN, were ∼10 pc and ∼several × 10{sup 5} M {sub ⊙}, respectively. HCN-to-HCO{sup +} J = 3–2 flux ratios substantially higher than unity were found throughout the nuclear region of NGC 1068. The continuum emission displayed an elongated morphology along the direction of the radio jet located at the northern side of the AGN, as well as a weak spatially-resolved component at ∼2.″0 on the southwestern side of the AGN. The latter component most likely originated from star formation, with the estimated luminosity more than one order of magnitude lower than the luminosity of the central AGN. No vibrationally excited ( v {sub 2} = 1f) J = 3–2 emission lines were detected for HCN and HCO{sup +} across the field of view.« less

ALMA 0.1-0.2 arcsec Resolution Imaging of the NGC 1068 Nucleus: Compact Dense Molecular Gas Emission at the Putative AGN Location

NASA Astrophysics Data System (ADS)

Imanishi, Masatoshi; Nakanishi, Kouichiro; Izumi, Takuma

2016-05-01

We present the results of our ALMA Cycle 2 high angular resolution (0.″1-0.″2) observations of the nuclear region of the nearby well-studied type-2 active galactic nucleus (AGN), NGC 1068, at HCN J = 3-2 and HCO+ J = 3-2 emission lines. For the first time, due to a higher angular resolution than previous studies, we clearly detected dense molecular gas emission at the putative AGN location, identified as a ˜1.1 mm (˜266 GHz) continuum emission peak, by separating this emission from brighter emission located at 0.″5-2.″0 on the eastern and western sides of the AGN. The estimated intrinsic molecular emission size and dense molecular mass, which are thought to be associated with the putative dusty molecular torus around an AGN, were ˜10 pc and ˜several × 105 M ⊙, respectively. HCN-to-HCO+ J = 3-2 flux ratios substantially higher than unity were found throughout the nuclear region of NGC 1068. The continuum emission displayed an elongated morphology along the direction of the radio jet located at the northern side of the AGN, as well as a weak spatially-resolved component at ˜2.″0 on the southwestern side of the AGN. The latter component most likely originated from star formation, with the estimated luminosity more than one order of magnitude lower than the luminosity of the central AGN. No vibrationally excited (v 2 = 1f) J = 3-2 emission lines were detected for HCN and HCO+ across the field of view.

UNVEILING THE PHYSICS OF LOW-LUMINOSITY AGNs THROUGH X-RAY VARIABILITY: LINER VERSUS SEYFERT 2

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

Hernández-García, L.; Masegosa, J.; Márquez, I.

X-ray variability is very common in active galactic nuclei (AGNs), but these variations may not occur similarly in different families of AGNs. We aim to disentangle the structure of low-ionization nuclear emission-line regions (LINERs) compared to Seyfert 2s by the study of their spectral properties and X-ray variations. We assembled the X-ray spectral parameters and variability patterns, which were obtained from simultaneous spectral fittings. Major differences are observed in the X-ray luminosities and the Eddington ratios, which are higher in Seyfert 2s. Short-term X-ray variations were not detected, while long-term changes are common in LINERs and Seyfert 2s. Compton-thick sourcesmore » generally do not show variations, most probably because the AGN is not accesible in the 0.5–10 keV energy band. The changes are mostly related to variations in the nuclear continuum, but other patterns of variability show that variations in the absorbers and at soft energies can be present in a few cases. We conclude that the X-ray variations may occur similarly in LINERs and Seyfert 2s, i.e., they are related to the nuclear continuum, although they might have different accretion mechanisms. Variations at UV frequencies are detected in LINER nuclei but not in Seyfert 2s. This is suggestive of at least some LINERs having an unobstructed view of the inner disk where the UV emission might take place, with UV variations being common in them. This result might be compatible with the disappeareance of the torus and/or the broad-line region in at least some LINERs.« less

Revealing H2D+ Depletion and Compact Structure in Starless and Protostellar Cores with ALMA

NASA Astrophysics Data System (ADS)

Friesen, R. K.; Di Francesco, J.; Bourke, T. L.; Caselli, P.; Jørgensen, J. K.; Pineda, J. E.; Wong, M.

2014-12-01

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the submillimeter dust continuum and H2D+ 110-111 emission toward two evolved, potentially protostellar cores within the Ophiuchus molecular cloud, Oph A SM1 and SM1N. The data reveal small-scale condensations within both cores, with mass upper limits of M <~ 0.02 M ⊙ (~20 M Jup). The SM1 condensation is consistent with a nearly symmetric Gaussian source with a width of only 37 AU. The SM1N condensation is elongated and extends 500 AU along its major axis. No evidence for substructure is seen in either source. A Jeans analysis indicates that these sources are unlikely to fragment, suggesting that both will form single stars. H2D+ is only detected toward SM1N, offset from the continuum peak by ~150-200 AU. This offset may be due to either heating from an undetected, young, low-luminosity protostellar source or first hydrostatic core, or HD (and consequently H2D+) depletion in the cold center of the condensation. We propose that SM1 is protostellar and that the condensation detected by ALMA is a warm (T ~ 30-50 K) accretion disk. The less concentrated emission of the SM1N condensation suggests that it is still starless, but we cannot rule out the presence of a low-luminosity source, perhaps surrounded by a pseudodisk. These data observationally reveal the earliest stages of the formation of circumstellar accretion regions and agree with theoretical predictions that disk formation can occur very early in the star formation process, coeval with or just after the formation of a first hydrostatic core or protostar.

Galaxy And Mass Assembly: evolution of the Hα luminosity function and star formation rate density up to z < 0.35

NASA Astrophysics Data System (ADS)

Gunawardhana, M. L. P.; Hopkins, A. M.; Bland-Hawthorn, J.; Brough, S.; Sharp, R.; Loveday, J.; Taylor, E.; Jones, D. H.; Lara-López, M. A.; Bauer, A. E.; Colless, M.; Owers, M.; Baldry, I. K.; López-Sánchez, A. R.; Foster, C.; Bamford, S.; Brown, M. J. I.; Driver, S. P.; Drinkwater, M. J.; Liske, J.; Meyer, M.; Norberg, P.; Robotham, A. S. G.; Ching, J. H. Y.; Cluver, M. E.; Croom, S.; Kelvin, L.; Prescott, M.; Steele, O.; Thomas, D.; Wang, L.

2013-08-01

Measurements of the low-z Hα luminosity function, Φ, have a large dispersion in the local number density of sources (˜0.5-1 Mpc-3 dex-1), and correspondingly in the star formation rate density (SFRD). The possible causes for these discrepancies include limited volume sampling, biases arising from survey sample selection, different methods of correcting for dust obscuration and active galactic nucleus contamination. The Galaxy And Mass Assembly (GAMA) survey and Sloan Digital Sky Survey (SDSS) provide deep spectroscopic observations over a wide sky area enabling detection of a large sample of star-forming galaxies spanning 0.001 < SFRHα (M⊙ yr- 1) < 100 with which to robustly measure the evolution of the SFRD in the low-z Universe. The large number of high-SFR galaxies present in our sample allow an improved measurement of the bright end of the luminosity function, indicating that the decrease in Φ at bright luminosities is best described by a Saunders functional form rather than the traditional Schechter function. This result is consistent with other published luminosity functions in the far-infrared and radio. For GAMA and SDSS, we find the r-band apparent magnitude limit, combined with the subsequent requirement for Hα detection leads to an incompleteness due to missing bright Hα sources with faint r-band magnitudes.

Mass functions for globular cluster main sequences based on CCD photometry and stellar models

NASA Astrophysics Data System (ADS)

McClure, Robert D.; Vandenberg, Don A.; Smith, Graeme H.; Fahlman, Gregory G.; Richer, Harvey B.; Hesser, James E.; Harris, William E.; Stetson, Peter B.; Bell, R. A.

1986-08-01

Main-sequence luminosity functions constructed from CCD observations of globular clusters reveal a strong trend in slope with metal abundance. Theoretical luminosity functions constructed from VandenBerg and Bell's (1985) isochrones have been fitted to the observations and reveal a trend between x, the power-law index of the mass function, and metal abundance. The most metal-poor clusters require an index of about x = 2.5, whereas the most metal-rich clusters exhibit an index of x of roughly -0.5. The luminosity functions for two sparse clusters, E3 and Pal 5, are distinct from those of the more massive clusters, in that they show a turndown which is possibly a result of mass loss or tidal disruption.

Toward a Unified View of Black-Hole High-Energy States

NASA Technical Reports Server (NTRS)

Nowak, Michael A.

1995-01-01

We present here a review of high-energy (greater than 1 keV) observations of seven black-hole candidates, six of which have estimated masses. In this review we focus on two parameters of interest: the ratio of 'nonthermal' to total luminosity as a function of the total luminosity divided by the Eddington luminosity, and the root-mean-square (rms) variability as a function of the nonthermal-to-total luminosity ratio. Below approx. 10% Eddington luminosity, the sources tend to be strictly nonthermal (the so called 'off' and 'low' states). Above this luminosity the sources become mostly thermal (the 'high' state). with the nonthermal component increasing with luminosity (the 'very high' and 'flare' states). There are important exceptions to this behavior, however, and no steady - as opposed to transient - source has been observed over a wide range of parameter space. In addition, the rms variability is positively correlated with the ratio of nonthermal to total luminosity, although there may be a minimum level of variability associated with 'thermal' states. We discuss these results in light of theoretical models and find that currently no single model describes the full range of black-hole high-energy behavior. In fact, the observations are exactly opposite from what one expects based upon simple notions of accretion disk instabilities.

Photoevaporating Disks around Young Stars: Ultracompact HII Regions and Protoplanetary Disks.

NASA Astrophysics Data System (ADS)

Johnstone, Douglas Ian

1995-01-01

Newly formed stars produce sufficient Lyman continuum luminosity phi to significantly alter the structure and evolution of the accretion disk surrounding them. In the absence of a stellar wind, a nearly static, photoionized, 10^4 K, disk atmosphere, with a scale height that increases with disk radius varpi as varpi^{3/2 }, forms inside the gravitational radius varpig ~ 1014(M_*/ M_odot) cm where M _* is the mass of the central star. This ionized atmosphere is maintained by both the direct radiation from the central star and the diffuse field produced in the disk atmosphere by the significant fraction of hydrogen recombinations directly to the ground state. Beyond varpig the material evaporated from the disk is capable of escaping from the system and produces an ionized disk wind. The mass-loss due to this disk wind peaks at varpig . The inclusion of a stellar wind into the basic picture reduces the height of the inner disk atmosphere and introduces a new scale radius varpi_ {w} where the thermal pressure of the material evaporated from the disk balances the ram pressure in the wind. In this case the mass-loss due to the disk wind peaks at varpiw and is enhanced over the no-wind case. The photoevaporation of disks around newly formed stars has significance to both ultracompact HII regions and the dispersal of solar-type nebulae. High mass stars are intrinsically hot and thus yield sufficient Lyman luminosity to create, even without a stellar wind, disk mass-loss rates of order 2 times 10 ^{-5}phi_sp{49} {1/2} M_odotyr ^{-1}, where phi 49 = phi/(10 49 Lyman continuum photons s^{-1}). This wind, which will last until the disk is dispersed, ~ 10^5 yrs if the disk mass is M_ {d}~0.3M_*, yields sizes, emission measures and ages consistent with observations of ultracompact HII regions. The well-observed high mass star MWC 349 may be the best example to date of an evaporating disk around a high mass star. On the other end of the stellar scale, many newly formed low-mass stars are known to have enhanced extreme ultraviolet luminosity suggested to be due to boundary layer accretion. Assuming that most low mass stars have such an enhanced Lyman luminosity phi ~ 1041 s ^{-1}, for ~ 3 times 10^7 yrs it is possible to remove most of the gas in the outer disk. A diagnostic of this mass loss may be the low-velocity forbidden oxygen, nitrogen, and sulphur line emission observed around young stars with disks. Photoevaporating disk models yield reasonable agreement with the flux seen in these lines. The process of photoevaporation also has implications for the formation of the giant planets within the solar nebula. Within young stellar clusters a few high mass stars may overwhelm the internal Lyman continuum flux from low mass stars and externally evaporated disks may result. The Trapezium region presents the best studied example of such a cluster. Photoionization due to high energy photons from the high mass stars erode the disks around nearby low mass stars. The resulting short destruction times for these disks constrain the gestation period for creating planets.

The quasar luminosity function from a variability-selected sample

NASA Astrophysics Data System (ADS)

Hawkins, M. R. S.; Veron, P.

1993-01-01

A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sign of the 'break' found in the recent UVX sample of Boyle et al. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.

Is the Ratio of Observed X-ray Luminosity to Bolometric Luminosity in Early-type Stars Really a Constant?

NASA Technical Reports Server (NTRS)

Waldron, W. L.

1985-01-01

The observed X-ray emission from early-type stars can be explained by the recombination stellar wind model (or base coronal model). The model predicts that the true X-ray luminosity from the base coronal zone can be 10 to 1000 times greater than the observed X-ray luminosity. From the models, scaling laws were found for the true and observed X-ray luminosities. These scaling laws predict that the ratio of the observed X-ray luminosity to the bolometric luminosity is functionally dependent on several stellar parameters. When applied to several other O and B stars, it is found that the values of the predicted ratio agree very well with the observed values.

A simultaneous search for High-z LAEs and LBGs in the SHARDS survey

NASA Astrophysics Data System (ADS)

Haro, P. Arrabal; Espinosa, J. M. Rodríguez; Muñoz-Tuñón, C.; Pérez-González, P. G.; Dannerbauer, H.; Bongiovann, Á.; Barro, G.; Cava, A.; Lumbreras-Calle, A.; Hernán-Caballero, A.; Eliche-Moral, M. C.; Sánchez, H. Dománguez; Conselice, C. J.; Tresse, L.; Pampliega, B. Alcalde; Balcells, M.; Daddi, E.; Rodighiero, G.

2018-05-01

We have undertaken a comprehensive search for both Lyman Alpha Emitters (LAEs) and Lyman Break Galaxies (LBGs) in the SHARDS Survey of the GOODS-N field. SHARDS is a deep imaging survey, made with the 10.4 m Gran Telescopio Canarias (GTC), employing 25 medium band filters in the range from 500 to 941 nm. This is the first time that both LAEs and LBGs are surveyed simultaneously in a systematic way in a large field. We draw a sample of 1558 sources; 528 of them are LAEs. Most of the sources (1434) show rest-frame UV continua. A minority of them (124) are pure LAEs with virtually no continuum detected in SHARDS. We study these sources from z ˜ 3.35 up to z ˜ 6.8, well into the epoch of reionization. Note that surveys done with just one or two narrow band filters lack the possibility to spot the rest-frame UV continuum present in most of our LAEs. We derive redshifts, Star Formation Rates (SFRs), Lyα Equivalent Widths (EWs) and Luminosity Functions (LFs). Grouping within our sample is also studied, finding 92 pairs or groups of galaxies at the same redshift separated by less than 60 comoving kpc. In addition, we relate 87 and 55 UV-selected objects with two known overdensities at z = 4.05 and z = 5.198, respectively. Finally, we show that surveys made with broad band filters are prone to introduce many unwanted sources (˜20% interlopers), which means that previous studies may be overestimating the calculated LFs, specially at the faint end.

THE CANADA-FRANCE HIGH-z QUASAR SURVEY: NINE NEW QUASARS AND THE LUMINOSITY FUNCTION AT REDSHIFT 6

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

Willott, Chris J.; Crampton, David; Hutchings, John B.

2010-03-15

We present discovery imaging and spectroscopy for nine new z {approx} 6 quasars found in the Canada-France High-z Quasar Survey (CFHQS) bringing the total number of CFHQS quasars to 19. By combining the CFHQS with the more luminous Sloan Digital Sky Survey sample, we are able to derive the quasar luminosity function from a sample of 40 quasars at redshifts 5.74 < z < 6.42. Our binned luminosity function shows a slightly lower normalization and flatter slope than found in previous work. The binned data also suggest a break in the luminosity function at M {sub 1450} {approx} -25. Amore » double power-law maximum likelihood fit to the data is consistent with the binned results. The luminosity function is strongly constrained (1{sigma} uncertainty <0.1 dex) over the range -27.5 < M {sub 1450} < -24.7. The best-fit parameters are {phi}(M*{sub 1450}) = 1.14 x 10{sup -8} Mpc{sup -3} mag{sup -1}, break magnitude M*{sub 1450} = -25.13, and bright end slope {beta} = -2.81. However, the covariance between {beta} and M*{sub 1450} prevents strong constraints being placed on either parameter. For a break magnitude in the range -26 < M*{sub 1450} < -24, we find -3.8 < {beta} < -2.3 at 95% confidence. We calculate the z = 6 quasar intergalactic ionizing flux and show it is between 20 and 100 times lower than that necessary for reionization. Finally, we use the luminosity function to predict how many higher redshift quasars may be discovered in future near-IR imaging surveys.« less

FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

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

Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L., E-mail: hess@ast.uct.ac.za, E-mail: ewilcots@astro.wisc.edu, E-mail: vhartwick@wisc.edu

2012-08-15

We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleusmore » (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.« less

The Radio Spectral Energy Distribution and Star-formation Rate Calibration in Galaxies

NASA Astrophysics Data System (ADS)

Tabatabaei, F. S.; Schinnerer, E.; Krause, M.; Dumas, G.; Meidt, S.; Damas-Segovia, A.; Beck, R.; Murphy, E. J.; Mulcahy, D. D.; Groves, B.; Bolatto, A.; Dale, D.; Galametz, M.; Sandstrom, K.; Boquien, M.; Calzetti, D.; Kennicutt, R. C.; Hunt, L. K.; De Looze, I.; Pellegrini, E. W.

2017-02-01

We study the spectral energy distribution (SED) of the radio continuum (RC) emission from the Key Insight in Nearby Galaxies Emitting in Radio (KINGFISHER) sample of nearby galaxies to understand the energetics and origin of this emission. Effelsberg multi-wavelength observations at 1.4, 4.8, 8.4, and 10.5 GHz combined with archive data allow us, for the first time, to determine the mid-RC (1-10 GHz, MRC) bolometric luminosities and further present calibration relations versus the monochromatic radio luminosities. The 1-10 GHz radio SED is fitted using a Bayesian Markov Chain Monte Carlo technique leading to measurements for the nonthermal spectral index ({S}ν ˜ {ν }-{α {nt}}) and the thermal fraction ({f}{th}) with mean values of {α }{nt}=0.97 +/- 0.16(0.79 +/- 0.15 for the total spectral index) and {f}{th} = (10 ± 9)% at 1.4 GHz. The MRC luminosity changes over ˜3 orders of magnitude in the sample, 4.3× {10}2 {L}⊙ < MRC < 3.9× {10}5 {L}⊙ . The thermal emission is responsible for ˜23% of the MRC on average. We also compare the extinction-corrected diagnostics of the star-formation rate (SFR) with the thermal and nonthermal radio tracers and derive the first star-formation calibration relations using the MRC radio luminosity. The nonthermal spectral index flattens with increasing SFR surface density, indicating the effect of the star-formation feedback on the cosmic-ray electron population in galaxies. Comparing the radio and IR SEDs, we find that the FIR-to-MRC ratio could decrease with SFR, due to the amplification of the magnetic fields in star-forming regions. This particularly implies a decrease in the ratio at high redshifts, where mostly luminous/star-forming galaxies are detected.

Six months of multiwavelength follow-up of the tidal disruption candidate ASASSN-14li and implied TDE rates from ASAS-SN

NASA Astrophysics Data System (ADS)

Holoien, T. W.-S.; Kochanek, C. S.; Prieto, J. L.; Stanek, K. Z.; Dong, Subo; Shappee, B. J.; Grupe, D.; Brown, J. S.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Danilet, A. B.; Falco, E.; Guo, Z.; Jose, J.; Herczeg, G. J.; Long, F.; Pojmanski, G.; Simonian, G. V.; Szczygieł, D. M.; Thompson, T. A.; Thorstensen, J. R.; Wagner, R. M.; Woźniak, P. R.

2016-01-01

We present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the centre of PGC 043234 (d ≃ 90 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of L ≃ 1044 erg s-1 and a total integrated energy of E ≃ 7 × 1050 erg radiated over the ˜6 months of observations presented. The UV/optical emission of the source is well fitted by a blackbody with roughly constant temperature of T ˜ 35 000 K, while the luminosity declines by roughly a factor of 16 over this time. The optical/UV luminosity decline is broadly consistent with an exponential decline, L∝ e^{-t/t_0}, with t0 ≃ 60 d. ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the optical and UV emission but declining at a slower rate, and the X-ray emission now dominates. Spectra of the source show broad Balmer and helium lines in emission as well as strong blue continuum emission at all epochs. We use the discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by ASAS-SN, finding an average rate of r ≃ 4.1 × 10-5 yr-1 per galaxy with a 90 per cent confidence interval of (2.2-17.0) × 10-5 yr-1 per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia supernovae in 2014, a rate that is much higher than that of other surveys.

Luminosities of Radio Pulsars

NASA Astrophysics Data System (ADS)

Bagchi, Manjari

2013-08-01

Luminosity is an intrinsic property of radio pulsars related to the properties of the magnetospheric plasma and the beam geometry, and inversely proportional to the observing frequency. In traditional models, luminosity has been considered as a function of the spin parameters of pulsars. On the other hand, parameter independent models like power law and lognormal have been also used to fit the observed luminosities. Some of the older studies on pulsar luminosities neglected observational biases, but all of the recent studies tried to model observational effects as accurately as possible. Luminosities of pulsars in globular clusters (GCs) and in the Galactic disk have been studied separately. Older studies concluded that these two categories of pulsars have different luminosity distributions, but the most recent study concluded that those are the same. This paper reviews all significant works on pulsar luminosities and discusses open questions.

The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

NASA Technical Reports Server (NTRS)

Finkelstein, Steven L.; Ryan, Russell E., Jr.; Papovich, Casey; Dickinson, Mark; Song, Mimi; Somerville, Rachel; Ferguson, Henry C.; Salmon, Brett; Giavalisco, Mauro; Koekomoer, Anton M.;

The Luminosity Function of QSO Host Galaxies

NASA Technical Reports Server (NTRS)

Hamilton, Timothy S.; Casertano, Stefano; Turnshek, David A.; White, Nicholas E. (Technical Monitor)

2002-01-01

We present some results from our HST archival image study of 71 QSO host galaxies. The objects are selected to have z less than or equal to 0.46 and total absolute magnitude M(sub v) less than or equal to -23 in our adopted cosmology (H(sub 0) = 50 kilometers per second Mpc(sup-1), q(sub 0) = 0.5, lambda = 0)). The aim of this initial study is to investigate the composition of the sample with respect to host morphology and radio loudness, as well as derive the QSO host galaxy luminosity function. We have analyzed available WFPC2 images in R or I band (U in one case), using a uniform set of procedures. The host galaxies span a narrow range of luminosities and are exceptionally bright, much more so than normal galaxies, usually L greater than L*(sub v). The QSOs are almost equally divided among three subclasses: radio-loud QSOs with elliptical hosts, radio-quiet QSOs with elliptical hosts, and radio-quiet QSOs with spiral hosts. Radio-loud QSOs with spiral hosts are extremely rare. Using a weighting procedure, we derive the combined luminosity function of QSO host galaxies. We find that the luminosity function of QSO hosts differs in shape from that of normal galaxies but that they coincide at the highest luminosities. The ratio of the number of quasar hosts to the number of normal galaxies at a luminosity L*(sub v) is R = (Lv/11.48L*(sub v))(sup 2.46), where L*(sub v) corresponds to M*(sub v)= -22.35, and a QSO is defined to be an object with total nuclear plus host light M(sub v) less than or equal to -23. This ratio can be interpreted as the probability that a galaxy with luminosity L(sub V) will host a QSO at redshift z approximately equal to 0.26.

JVLA Observations of Young Brown Dwarfs

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

Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina, E-mail: l.rodriguez@crya.unam.mx, E-mail: l.zapata@crya.unam.mx, E-mail: a.palau@crya.unam.mx

We present sensitive 3.0 cm JVLA radio continuum observations of six regions of low-mass star formation that include twelve young brown dwarfs (BDs) and four young BD candidates. We detect a total of 49 compact radio sources in the fields observed, of which 24 have no reported counterparts and are considered new detections. Twelve of the radio sources show variability in timescales of weeks to months, suggesting gyrosynchrotron emission produced in active magnetospheres. Only one of the target BDs, FU Tau A, was detected. However, we detected radio emission associated with two of the BD candidates, WL 20S and CHLTmore » 2. The radio flux densities of the sources associated with these BD candidates are more than an order of magnitude larger than expected for a BD and suggest a revision of their classification. In contrast, FU Tau A falls on the well-known correlation between radio luminosity and bolometric luminosity, suggesting that the emission comes from a thermal jet and that this BD seems to be forming as a scaled-down version of low-mass stars.« less

Photoionization of the diffuse interstellar medium and galactic halo by OB associtations

NASA Technical Reports Server (NTRS)

Dove, James B.; Shull, J. Michael

1994-01-01

Assuming smoothly varying H I distributions in te Galactic disk, we have calculated the geometry of diffuse II regions due to OB associations in the Galactic plane. Near the solar circle, OB associations with a Lyman continuum (Lyc) photon luminosity Psi(sub Lyc) = 3.3 x 10(exp 7) cm(exp -2) s(exp -1), produce H II regions that are density bounded in the vertical direction (H II chimneys) allowing Lyc to escape the gaseous disk and penetrate into the Galactic halo. We provide analytic formulae for the Lyc escape fraction as functions of S(sub 0) O-star catalog of Garmany and a new Lyc stellar stellar Lyc stellar flux calibration, we find a production rate of Lyc photons by OB associations within 2.5 kpc of Psi(sub Lyc) = 3.3 x 10(exp 7) cm(exp -2) s(exp -1). Integrating the fraction of Lyc photons that escape the disk over our adopted luminosity function of OB associations, we estimate that approximately 7% of the ionizing photons, or Phi(sub Lyc) = 2.3 x 10(exp 6) cm(exp -2) s(exp -1), escape each side of the H I disk layer and penetrate the diffuse ionized medium ('Reynolds layer'). This flux is sufficient to explain the potoionization of this, although we have not constructed a model for the observed H-alpha emission and pulsar dispersion measures that is fully consistent with the absorption rate of Lyc in the H II layer. Since our quiescent model does not account for the effects of dynamic chimneys and superbubbles, which should enhance Lyc escape, we conclude the O stars are the probable source of ionizing radiation for the Reynolds layer. For a random distribution of OB associations throughout the disk, the Lyc flux is nearly uniform for heights Z is greater than approximately 0.8 kpc above the midplane.

The Evolution of Ly-alpha Emitting Galaxies Between z = 2.1 and z = 3.l

NASA Technical Reports Server (NTRS)

Ciardullo, Robin; Gronwall,Caryl; Wolf, Christopher; McCathran, Emily; Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Feldmeier, John J.; Treister, Ezequiel; Padilla, Nelson;

X-ray studies of quasars with the Einstein Observatory. IV - X-ray dependence on radio emission

NASA Technical Reports Server (NTRS)

Worrall, D. M.; Tananbaum, H.; Giommi, P.; Zamorani, G.

1987-01-01

The X-ray properties of a sample of 114 radio-loud quasars observed with the Einstein Observatory are examined, and the results are compared with those obtained from a large sample of radio-quiet quasars. The results of statistical analysis of the dependence of X-ray luminosity on combined functions of optical and radio luminosity show that the dependence on both luminosities is important. However, statistically significant differences are found between subsamples of flat radio spectra quasars and steep radio spectra quasars with regard to dependence of X-ray luminosity on only radio luminosity. The data are consistent with radio-loud quasars having a physical component, not directly related to the optical luminosity, which produces the core radio luminosity plus 'extra' X-ray emission.

High Sensitivity, High Angular Resolution Far-infrared Photometry from the KAO

NASA Technical Reports Server (NTRS)

Lester, D.; Harvey, P. M.; Wilking, B. A.; Joy, M.

1984-01-01

Most of the luminosity of embedded sources is reemitted in the far-infrared continuum. Measurements in the far-infrared are essential to understand the energetics of the interstellar medium, and of star formation regions in particular. Measurements from the KAO, are made in diffraction limited beams that sample a spatial scale considerably smaller than that given by IRAS. The KAO instrument technology has matured to the point that the single scan limiting flux of IRAS at 100 micro can be reached in a diffraction limited beam in a single typical KAO observing leg. The far-infrared photometer system and selections of recent observations are presented.

On the origin of power-law X-ray spectra of active galactic nuclei

NASA Technical Reports Server (NTRS)

Schlosman, I.; Shaham, J.; Shaviv, G.

1984-01-01

In the present analytical model for a power law X-ray continuum production in active galactic nuclei, the dissipation of turbulent energy flux above the accretion disk forms an optically thin transition layer with an inverted temperature gradient. The emitted thermal radiation has a power law spectrum in the 0.1-100 keV range, with a photon energy spectral index gamma of about 0.4-1.0. Thermal X-ray contribution from the layer is 5-10 percent of the total disk luminosity. The gamma value of 0.75 is suggested as a 'natural' power law index for Seyfert galaxies and QSOs.

Cyclotron Lines in Accreting Neutron Star Spectra

NASA Astrophysics Data System (ADS)

Wilms, Jörn; Schönherr, Gabriele; Schmid, Julia; Dauser, Thomas; Kreykenbohm, Ingo

2009-05-01

Cyclotron lines are formed through transitions of electrons between discrete Landau levels in the accretion columns of accreting neutron stars with strong (1012 G) magnetic fields. We summarize recent results on the formation of the spectral continuum of such systems, describe recent advances in the modeling of the lines based on a modification of the commonly used Monte Carlo approach, and discuss new results on the dependence of the measured cyclotron line energy from the luminosity of transient neutron star systems. Finally, we show that Simbol-X will be ideally suited to build and improve the observational database of accreting and strongly magnetized neutron stars.

FRAGMENTATION AND EVOLUTION OF MOLECULAR CLOUDS. II. THE EFFECT OF DUST HEATING

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

Urban, Andrea; Evans, Neal J.; Martel, Hugo

2010-02-20

We investigate the effect of heating by luminosity sources in a simulation of clustered star formation. Our heating method involves a simplified continuum radiative transfer method that calculates the dust temperature. The gas temperature is set by the dust temperature. We present the results of four simulations; two simulations assume an isothermal equation of state and the two other simulations include dust heating. We investigate two mass regimes, i.e., 84 M{sub sun} and 671 M{sub sun}, using these two different energetics algorithms. The mass functions for the isothermal simulations and simulations that include dust heating are drastically different. In themore » isothermal simulation, we do not form any objects with masses above 1 M{sub sun}. However, the simulation with dust heating, while missing some of the low-mass objects, forms high-mass objects ({approx}20 M{sub sun}) which have a distribution similar to the Salpeter initial mass function. The envelope density profiles around the stars formed in our simulation match observed values around isolated, low-mass star-forming cores. We find the accretion rates to be highly variable and, on average, increasing with final stellar mass. By including radiative feedback from stars in a cluster-scale simulation, we have determined that it is a very important effect which drastically affects the mass function and yields important insights into the formation of massive stars.« less

VizieR Online Data Catalog: Quasar luminosity function (Hawkins+, 1993)

NASA Astrophysics Data System (ADS)

Hawkins, M. R. S.; Veron, P.

1994-11-01

A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved. (1 data file).

A large sample of Kohonen-selected SDSS quasars with weak emission lines: selection effects and statistical properties

NASA Astrophysics Data System (ADS)

Meusinger, H.; Balafkan, N.

2014-08-01

Aims: A tiny fraction of the quasar population shows remarkably weak emission lines. Several hypotheses have been developed, but the weak line quasar (WLQ) phenomenon still remains puzzling. The aim of this study was to create a sizeable sample of WLQs and WLQ-like objects and to evaluate various properties of this sample. Methods: We performed a search for WLQs in the spectroscopic data from the Sloan Digital Sky Survey Data Release 7 based on Kohonen self-organising maps for nearly 105 quasar spectra. The final sample consists of 365 quasars in the redshift range z = 0.6 - 4.2 (z¯ = 1.50 ± 0.45) and includes in particular a subsample of 46 WLQs with equivalent widths WMg ii< 11 Å and WC iv< 4.8 Å. We compared the luminosities, black hole masses, Eddington ratios, accretion rates, variability, spectral slopes, and radio properties of the WLQs with those of control samples of ordinary quasars. Particular attention was paid to selection effects. Results: The WLQs have, on average, significantly higher luminosities, Eddington ratios, and accretion rates. About half of the excess comes from a selection bias, but an intrinsic excess remains probably caused primarily by higher accretion rates. The spectral energy distribution shows a bluer continuum at rest-frame wavelengths ≳1500 Å. The variability in the optical and UV is relatively low, even taking the variability-luminosity anti-correlation into account. The percentage of radio detected quasars and of core-dominant radio sources is significantly higher than for the control sample, whereas the mean radio-loudness is lower. Conclusions: The properties of our WLQ sample can be consistently understood assuming that it consists of a mix of quasars at the beginning of a stage of increased accretion activity and of beamed radio-quiet quasars. The higher luminosities and Eddington ratios in combination with a bluer spectral energy distribution can be explained by hotter continua, i.e. higher accretion rates. If quasar activity consists of subphases with different accretion rates, a change towards a higher rate is probably accompanied by an only slow development of the broad line region. The composite WLQ spectrum can be reasonably matched by the ordinary quasar composite where the continuum has been replaced by that of a hotter disk. A similar effect can be achieved by an additional power-law component in relativistically boosted radio-quiet quasars, which may explain the high percentage of radio quasars. The full catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/A114

Observations of Herbig Ae/Be stars with Herschel/PACS. The atomic and molecular contents of their protoplanetary discs

NASA Astrophysics Data System (ADS)

Meeus, G.; Montesinos, B.; Mendigutía, I.; Kamp, I.; Thi, W. F.; Eiroa, C.; Grady, C. A.; Mathews, G.; Sandell, G.; Martin-Zaïdi, C.; Brittain, S.; Dent, W. R. F.; Howard, C.; Ménard, F.; Pinte, C.; Roberge, A.; Vandenbussche, B.; Williams, J. P.

2012-08-01

We observed a sample of 20 representative Herbig Ae/Be stars and 5 A-type debris discs with PACS onboard Herschel, as part of the GAS in Protoplanetary Systems (GASPS) project. The observations were done in spectroscopic mode, and cover the far-infrared lines of [O i], [C ii], CO, CH+, H2O, and OH. We have a [O i] 63 μm detection rate of 100% for the Herbig Ae/Be and 0% for the debris discs. The [O i] 145 μm line is only detected in 25% and CO J = 18-17 in 45% (and fewer cases for higher J transitions) of the Herbig Ae/Be stars, while for [C ii] 157 μm, we often find spatially variable background contamination. We show the first detection of water in a Herbig Ae disc, HD 163296, which has a settled disc. Hydroxyl is detected as well in this disc. First seen in HD 100546, CH+ emission is now detected for the second time in a Herbig Ae star, HD 97048. We report fluxes for each line and use the observations as line diagnostics of the gas properties. Furthermore, we look for correlations between the strength of the emission lines and either the stellar or disc parameters, such as stellar luminosity, ultraviolet and X-ray flux, accretion rate, polycyclic aromatic hydrocarbon (PAH) band strength, and flaring. We find that the stellar ultraviolet flux is the dominant excitation mechanism of [O i] 63 μm, with the highest line fluxes being found in objects with a large amount of flaring and among the largest PAH strengths. Neither the amount of accretion nor the X-ray luminosity has an influence on the line strength. We find correlations between the line flux of [O i] 63 μm and [O i] 145 μm, CO J = 18-17 and [O i] 6300 Å, and between the continuum flux at 63 μm and at 1.3 mm, while we find weak correlations between the line flux of [O i] 63 μm and the PAH luminosity, the line flux of CO J = 3-2, the continuum flux at 63 μm, the stellar effective temperature, and the Brγ luminosity. Finally, we use a combination of the[O i] 63 μm and 12CO J = 2-1 line fluxes to obtain order of magnitude estimates of the disc gas masses, in agreement with the values that we find from detailed modelling of two Herbig Ae/Be stars, HD 163296 and HD 169142. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The Luminosity Function and Star Formation Rate Between Redshifts of 0.07 and 1.47 for Narrow-band Emitters in the Subaru Deep Field

NASA Astrophysics Data System (ADS)

Ly, Chun; Malkan, M.; Kashikawa, N.; Shimasaku, K.; Doi, M.; Nagao, T.; Iye, M.; Kodama, T.; Morokuma, T.; Motohara, K.

2006-06-01

Subaru Deep Field line-emitting galaxies in four narrow-band filters at low and intermediate redshifts are presented. Broad-band colors, follow-up optical spectroscopy, and multiple narrow-band filters are used to distinguish Hα, [OII], and [OIII] emitters between redshifts of 0.07 and 1.47 to construct their averaged rest-frame optical-to-UV SED and luminosity functions. These luminosity functions are derived down to faint magnitudes, which allows for a more accurate determination of the faint end slope. With a large (N 200-900) sample for each redshift interval, a Schechter profile is fitted to each luminosity function. Prior to dust extinction corrections, the [OIII] and [OII] luminosity functions reported in this paper agree reasonably well with those of Hippelein et al (2003). The z=0.066-0.092 Hα LF agrees with those of Jones & Bland-Hawthorn (2001), but for z=0.24 and 0.40, their number density is higher by a factor of two or more. The z=0.08 Hα LF, which reaches two orders of magnitude fainter than Gallego et al. (1995), is steeper by 25%. This indicates that there are more low luminosity star-forming galaxies for z<0.1 than predicted. The faint end slope α and φ* show a strong evolution with redshift while L* show little evolution. The evolution in α indicates that low-luminosity galaxies have a stronger evolution compared to brighter ones. Integrated star formation rate densities are derived via Hα for 0.07

A multi-wavelength census of star formation activity in the young embedded cluster around Serpens/G3-G6

NASA Astrophysics Data System (ADS)

Djupvik, A. A.; André, Ph.; Bontemps, S.; Motte, F.; Olofsson, G.; Gålfalk, M.; Florén, H.-G.

2006-11-01

Aims.The aim of this paper is to characterise the star formation activity in the poorly studied embedded cluster Serpens/G3-G6, located ~45 arcmin (3 pc) to the south of the Serpens Cloud Core, and to determine the luminosity and mass functions of its population of Young Stellar Objects (YSOs). Methods: .Multi-wavelength broadband photometry was obtained to sample the near and mid-IR spectral energy distributions to separate YSOs from field stars and classify the YSO evolutionary stage. ISOCAM mapping in the two filters LW2 (5-8.5 μm) and LW3 (12-18 μm) of a 19 arcmin × 16 arcmin field was combined with JHKS data from 2MASS, KS data from Arnica/NOT, and L arcmin data from SIRCA/NOT. Continuum emission at 1.3 mm (IRAM) and 3.6 cm (VLA) was mapped to study the cloud structure and the coldest/youngest sources. Deep narrow band imaging at the 2.12 μm S(1) line of H2 from NOTCam/NOT was obtained to search for signs of bipolar outflows. Results: .We have strong evidence for a stellar population of 31 Class II sources, 5 flat-spectrum sources, 5 Class I sources, and two Class 0 sources. Our method does not sample the Class III sources. The cloud is composed of two main dense clumps aligned along a ridge over ~0.5 pc plus a starless core coinciding with absorption features seen in the ISOCAM maps. We find two S-shaped bipolar collimated flows embedded in the NE clump, and propose the two driving sources to be a Class 0 candidate (MMS3) and a double Class I (MMS2). For the Class II population we find a best age of ~2 Myr and compatibility with recent Initial Mass Functions (IMFs) by comparing the observed Class II luminosity function (LF), which is complete to 0.08 L⊙, to various model LFs with different star formation scenarios and input IMFs.

Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

DOE PAGES

Pei, L.; Fausnaugh, M. M.; Barth, A. J.; ...

2017-03-10

Here, we present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He II λ4686 broad emission-line light curves lag that of the 5100 Å optical continuum bymore » $${4.17}_{-0.36}^{+0.36}\\,\\mathrm{days}$$ and $${0.79}_{-0.34}^{+0.35}\\,\\mathrm{days}$$, respectively. The Hβ lag relative to the 1158 Å ultraviolet continuum light curve measured by the Hubble Space Telescope is ~50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ~50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He II(+O III]), and Si Iv(+O Iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the R BLR–L AGN relation based on the past behavior of NGC 5548.« less

Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

NASA Astrophysics Data System (ADS)

Pei, L.; Fausnaugh, M. M.; Barth, A. J.; Peterson, B. M.; Bentz, M. C.; De Rosa, G.; Denney, K. D.; Goad, M. R.; Kochanek, C. S.; Korista, K. T.; Kriss, G. A.; Pogge, R. W.; Bennert, V. N.; Brotherton, M.; Clubb, K. I.; Dalla Bontà, E.; Filippenko, A. V.; Greene, J. E.; Grier, C. J.; Vestergaard, M.; Zheng, W.; Adams, Scott M.; Beatty, Thomas G.; Bigley, A.; Brown, Jacob E.; Brown, Jonathan S.; Canalizo, G.; Comerford, J. M.; Coker, Carl T.; Corsini, E. M.; Croft, S.; Croxall, K. V.; Deason, A. J.; Eracleous, Michael; Fox, O. D.; Gates, E. L.; Henderson, C. B.; Holmbeck, E.; Holoien, T. W.-S.; Jensen, J. J.; Johnson, C. A.; Kelly, P. L.; Kim, S.; King, A.; Lau, M. W.; Li, Miao; Lochhaas, Cassandra; Ma, Zhiyuan; Manne-Nicholas, E. R.; Mauerhan, J. C.; Malkan, M. A.; McGurk, R.; Morelli, L.; Mosquera, Ana; Mudd, Dale; Muller Sanchez, F.; Nguyen, M. L.; Ochner, P.; Ou-Yang, B.; Pancoast, A.; Penny, Matthew T.; Pizzella, A.; Poleski, Radosław; Runnoe, Jessie; Scott, B.; Schimoia, Jaderson S.; Shappee, B. J.; Shivvers, I.; Simonian, Gregory V.; Siviero, A.; Somers, Garrett; Stevens, Daniel J.; Strauss, M. A.; Tayar, Jamie; Tejos, N.; Treu, T.; Van Saders, J.; Vican, L.; Villanueva, S., Jr.; Yuk, H.; Zakamska, N. L.; Zhu, W.; Anderson, M. D.; Arévalo, P.; Bazhaw, C.; Bisogni, S.; Borman, G. A.; Bottorff, M. C.; Brandt, W. N.; Breeveld, A. A.; Cackett, E. M.; Carini, M. T.; Crenshaw, D. M.; De Lorenzo-Cáceres, A.; Dietrich, M.; Edelson, R.; Efimova, N. V.; Ely, J.; Evans, P. A.; Ferland, G. J.; Flatland, K.; Gehrels, N.; Geier, S.; Gelbord, J. M.; Grupe, D.; Gupta, A.; Hall, P. B.; Hicks, S.; Horenstein, D.; Horne, Keith; Hutchison, T.; Im, M.; Joner, M. D.; Jones, J.; Kaastra, J.; Kaspi, S.; Kelly, B. C.; Kennea, J. A.; Kim, M.; Kim, S. C.; Klimanov, S. A.; Lee, J. C.; Leonard, D. C.; Lira, P.; MacInnis, F.; Mathur, S.; McHardy, I. M.; Montouri, C.; Musso, R.; Nazarov, S. V.; Netzer, H.; Norris, R. P.; Nousek, J. A.; Okhmat, D. N.; Papadakis, I.; Parks, J. R.; Pott, J.-U.; Rafter, S. E.; Rix, H.-W.; Saylor, D. A.; Schnülle, K.; Sergeev, S. G.; Siegel, M.; Skielboe, A.; Spencer, M.; Starkey, D.; Sung, H.-I.; Teems, K. G.; Turner, C. S.; Uttley, P.; Villforth, C.; Weiss, Y.; Woo, J.-H.; Yan, H.; Young, S.; Zu, Y.

2017-03-01

We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He II λ4686 broad emission-line light curves lag that of the 5100 Å optical continuum by {4.17}-0.36+0.36 {days} and {0.79}-0.34+0.35 {days}, respectively. The Hβ lag relative to the 1158 Å ultraviolet continuum light curve measured by the Hubble Space Telescope is ˜50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ˜50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He II emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C IV, Lyα, He II(+O III]), and Si IV(+O IV]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the R BLR-L AGN relation based on the past behavior of NGC 5548.

Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548

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

Pei, L.; Fausnaugh, M. M.; Barth, A. J.

Here, we present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The Hβ and He II λ4686 broad emission-line light curves lag that of the 5100 Å optical continuum bymore » $${4.17}_{-0.36}^{+0.36}\\,\\mathrm{days}$$ and $${0.79}_{-0.34}^{+0.35}\\,\\mathrm{days}$$, respectively. The Hβ lag relative to the 1158 Å ultraviolet continuum light curve measured by the Hubble Space Telescope is ~50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is ~50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for Hβ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the Hβ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He II(+O III]), and Si Iv(+O Iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured Hβ lag is a factor of five shorter than the expected value implied by the R BLR–L AGN relation based on the past behavior of NGC 5548.« less

Evidence for a mass-dependent AGN Eddington ratio distribution via the flat relationship between SFR and AGN luminosity

NASA Astrophysics Data System (ADS)

Bernhard, E.; Mullaney, J. R.; Aird, J.; Hickox, R. C.; Jones, M. L.; Stanley, F.; Grimmett, L. P.; Daddi, E.

2018-05-01

The lack of a strong correlation between AGN X-ray luminosity (LX; a proxy for AGN power) and the star formation rate (SFR) of their host galaxies has recently been attributed to stochastic AGN variability. Studies using population synthesis models have incorporated this by assuming a broad, universal (i.e. does not depend on the host galaxy properties) probability distribution for AGN specific X-ray luminosities (i.e. the ratio of LX to host stellar mass; a common proxy for Eddington ratio). However, recent studies have demonstrated that this universal Eddington ratio distribution fails to reproduce the observed X-ray luminosity functions beyond z ˜ 1.2. Furthermore, empirical studies have recently shown that the Eddington ratio distribution may instead depend upon host galaxy properties, such as SFR and/or stellar mass. To investigate this further, we develop a population synthesis model in which the Eddington ratio distribution is different for star-forming and quiescent host galaxies. We show that, although this model is able to reproduce the observed X-ray luminosity functions out to z ˜ 2, it fails to simultaneously reproduce the observed flat relationship between SFR and X-ray luminosity. We can solve this, however, by incorporating a mass dependency in the AGN Eddington ratio distribution for star-forming host galaxies. Overall, our models indicate that a relative suppression of low Eddington ratios (λEdd ≲ 0.1) in lower mass galaxies (M* ≲ 1010 - 11 M⊙) is required to reproduce both the observed X-ray luminosity functions and the observed flat SFR/X-ray relationship.

Binary Systems and the Initial Mass Function

NASA Astrophysics Data System (ADS)

Malkov, O. Yu.

2017-07-01

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

Sensitivity of the Properties of Ruthenium “Blue Dimer” to Method, Basis Set, and Continuum Model

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

Ozkanlar, Abdullah; Clark, Aurora E.

2012-05-23

The ruthenium “blue dimer” [(bpy)2RuIIIOH2]2O4+ is best known as the first well-defined molecular catalyst for water oxidation. It has been subject to numerous computational studies primarily employing density functional theory. However, those studies have been limited in the functionals, basis sets, and continuum models employed. The controversy in the calculated electronic structure and the reaction energetics of this catalyst highlights the necessity of benchmark calculations that explore the role of density functionals, basis sets, and continuum models upon the essential features of blue-dimer reactivity. In this paper, we report Kohn-Sham complete basis set (KS-CBS) limit extrapolations of the electronic structuremore » of “blue dimer” using GGA (BPW91 and BP86), hybrid-GGA (B3LYP), and meta-GGA (M06-L) density functionals. The dependence of solvation free energy corrections on the different cavity types (UFF, UA0, UAHF, UAKS, Bondi, and Pauling) within polarizable and conductor-like polarizable continuum model has also been investigated. The most common basis sets of double-zeta quality are shown to yield results close to the KS-CBS limit; however, large variations are observed in the reaction energetics as a function of density functional and continuum cavity model employed.« less

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

NASA Astrophysics Data System (ADS)

Tzanavaris, Panayiotis

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

On the Disappearance of a Cold Molecular Torus around the Low-luminosity Active Galactic Nucleus of NGC 1097

NASA Astrophysics Data System (ADS)

Izumi, T.; Kohno, K.; Fathi, K.; Hatziminaoglou, E.; Davies, R. I.; Martín, S.; Matsushita, S.; Schinnerer, E.; Espada, D.; Aalto, S.; Onishi, K.; Turner, J. L.; Imanishi, M.; Nakanishi, K.; Meier, D. S.; Wada, K.; Kawakatu, N.; Nakajima, T.

2017-08-01

We used the Atacama Large Millimeter/Submillimeter Array to map the CO(3-2) and the underlying continuum emissions around the type-1 low-luminosity active galactic nucleus (LLAGN; bolometric luminosity ≲ {10}42 erg s-1) of NGC 1097 at ˜10 pc resolution. These observations revealed a detailed cold gas distribution within a ˜100 pc of this LLAGN. In contrast to the luminous Seyfert galaxy NGC 1068, where a ˜7 pc cold molecular torus was recently revealed, a distinctively dense and compact torus is missing in our CO(3-2) integrated intensity map of NGC 1097. Based on the CO(3-2) flux, the gas mass of the torus of NGC 1097 would be a factor of ≳2-3 less than that found for NGC 1068 by using the same CO-to-H2 conversion factor, which implies less active nuclear star formation and/or inflows in NGC 1097. Our dynamical modeling of the CO(3-2) velocity field implies that the cold molecular gas is concentrated in a thin layer as compared to the hot gas traced by the 2.12 μm H2 emission in and around the torus. Furthermore, we suggest that NGC 1097 hosts a geometrically thinner torus than NGC 1068. Although the physical origin of the torus thickness remains unclear, our observations support a theoretical prediction that geometrically thick tori with high opacity will become deficient as AGNs evolve from luminous Seyferts to LLAGNs.

A distance-limited sample of massive star-forming cores from the RMS

NASA Astrophysics Data System (ADS)

Maud, L. T.; Lumsden, S. L.; Moore, T. J. T.; Mottram, J. C.; Urquhart, J. S.; Cicchini, A.

2015-09-01

We analyse C18O (J = 3-2) data from a sample of 99 infrared (IR)-bright massive young stellar objects (MYSOs) and compact H II regions that were identified as potential molecular-outflow sources in the Red MSX Source survey. We extract a distance-limited (D < 6 kpc) sample shown to be representative of star formation covering the transition between the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, though the alternative explanation, that Larson's relations arise where surface-density-limited samples are considered, is also consistent with our data. There are no significant differences found between source properties for the MYSOs and H II regions, suggesting that the core properties are established prior to the formation of massive stars, which subsequently have little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuum and C18O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. A clear linear relationship is seen between the independently established core masses and luminosities. The position of MYSOs and compact H II regions in the mass-luminosity plane is consistent with the luminosity expected from the most massive protostar in the cluster when using an ˜40 per cent star formation efficiency and indicates that they are at a similar evolutionary stage, near the end of the accretion phase.

A clumpy stellar wind and luminosity-dependent cyclotron line revealed by the first Suzaku observation of the high-mass X-ray binary 4U 1538–522

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

Hemphill, Paul B.; Rothschild, Richard E.; Markowitz, Alex

2014-09-01

We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538–522. The broadband spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at 23.0 ± 0.4 keV and the iron Kα line at 6.426 ± 0.008 keV, as well as placing limits on the strengths of the iron Kβ line and the iron K edge. We track the evolution of the spectral parameters both in time and in luminosity, notably finding a significant positive correlation between cyclotron line energy and luminosity. A dip and spike in the light curvemore » is shown to be associated with an order-of-magnitude increase in column density along the line of sight, as well as significant variation in the underlying continuum, implying the accretion of a overdense region of a clumpy stellar wind. We also present a phase-resolved analysis, with most spectral parameters of interest showing significant variation with phase. Notably, both the cyclotron line energy and the iron Kα line intensity vary significantly with phase, with the iron line intensity significantly out of phase with the pulse profile. We discuss the implications of these findings in the context of recent work in the areas of accretion column physics and cyclotron resonance scattering feature formation.« less

Low-luminosity stellar mass functions in globular clusters

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

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

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

Gamma-Ray Burst Host Galaxies Have "Normal" Luminosities.

PubMed

Schaefer

2000-04-10

The galactic environment of gamma-ray bursts can provide good evidence about the nature of the progenitor system, with two old arguments implying that the burst host galaxies are significantly subluminous. New data and new analysis have now reversed this picture: (1) Even though the first two known host galaxies are indeed greatly subluminous, the next eight hosts have absolute magnitudes typical for a population of field galaxies. A detailed analysis of the 16 known hosts (10 with redshifts) shows them to be consistent with a Schechter luminosity function with R*=-21.8+/-1.0, as expected for normal galaxies. (2) Bright bursts from the Interplanetary Network are typically 18 times brighter than the faint bursts with redshifts; however, the bright bursts do not have galaxies inside their error boxes to limits deeper than expected based on the luminosities for the two samples being identical. A new solution to this dilemma is that a broad burst luminosity function along with a burst number density varying as the star formation rate will require the average luminosity of the bright sample (>6x1058 photons s-1 or>1.7x1052 ergs s-1) to be much greater than the average luminosity of the faint sample ( approximately 1058 photons s-1 or approximately 3x1051 ergs s-1). This places the bright bursts at distances for which host galaxies with a normal luminosity will not violate the observed limits. In conclusion, all current evidence points to gamma-ray burst host galaxies being normal in luminosity.

The galaxy luminosity function around groups

NASA Astrophysics Data System (ADS)

González, R. E.; Padilla, N. D.; Galaz, G.; Infante, L.

2005-11-01

We present a study on the variations of the luminosity function of galaxies around clusters in a numerical simulation with semi-analytic galaxies, attempting to detect these variations in the 2dF Galaxy Redshift Survey. We subdivide the simulation box into equal-density regions around clusters, which we assume can be achieved by selecting objects at a given normalized distance (r/rrms, where rrms is an estimate of the halo radius) from the group centre. The semi-analytic model predicts important variations in the luminosity function out to r/rrms~= 5. In brief, variations in the mass function of haloes around clusters (large dark matter haloes with M > 1012h-1Msolar) lead to cluster central regions that present a high abundance of bright galaxies (high M* values) as well as low-luminosity galaxies (high α) at r/rrms~= 3 there is a lack of bright galaxies, which shows the depletion of galaxies in the regions surrounding clusters (minimum in M* and α), and a tendency to constant luminosity function parameters at larger cluster-centric distances. We take into account the observational biases present in the real data by reproducing the peculiar velocity effect on the redshifts of galaxies in the simulation box, and also by producing mock catalogues. We find that excluding from the analysis galaxies which in projection are close to the centres of the groups provides results that are qualitatively consistent with the full simulation box results. When we apply this method to mock catalogues of the 2dF Galaxy Redshift Survey (2dFGRS) and the 2PIGG catalogue of groups, we find that the variations in the luminosity function are almost completely erased by the Finger of God effect; only a lack of bright galaxies at r/rrms~= 3 can be marginally detected in the mock catalogues. The results from the real 2dFGRS data show a clearer detection of a dip in M* and α for r/rrms= 3, consistent with the semi-analytic predictions.

Collapsar γ-ray bursts: how the luminosity function dictates the duration distribution

NASA Astrophysics Data System (ADS)

Petropoulou, Maria; Barniol Duran, Rodolfo; Giannios, Dimitrios

2017-12-01

Jets in long-duration γ-ray bursts (GRBs) have to drill through the collapsing star in order to break out of it and produce the γ-ray signal while the central engine is still active. If the breakout time is shorter for more powerful engines, then the jet-collapsar interaction acts as a filter of less luminous jets. We show that the observed broken power-law GRB luminosity function is a natural outcome of this process. For a theoretically motivated breakout time that scales with jet luminosity as L-χ with χ ∼ 1/3-1/2, we show that the shape of the γ-ray duration distribution can be uniquely determined by the GRB luminosity function and matches the observed one. This analysis has also interesting implications about the supernova-central engine connection. We show that not only successful jets can deposit sufficient energy in the stellar envelope to power the GRB-associated supernovae, but also failed jets may operate in all Type Ib/c supernovae.

Ultra-faint ultraviolet galaxies at z ∼ 2 behind the lensing cluster A1689: The luminosity function, dust extinction, and star formation rate density

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

Alavi, Anahita; Siana, Brian; Freeman, William R.

We have obtained deep ultraviolet imaging of the lensing cluster A1689 with the WFC3/UVIS camera onboard the Hubble Space Telescope in the F275W (30 orbits) and F336W (4 orbits) filters. These images are used to identify z ∼ 2 star-forming galaxies via their Lyman break, in the same manner that galaxies are typically selected at z ≥ 3. Because of the unprecedented depth of the images and the large magnification provided by the lensing cluster, we detect galaxies 100× fainter than previous surveys at this redshift. After removing all multiple images, we have 58 galaxies in our sample in themore » range –19.5 < M {sub 1500} < –13 AB mag. Because the mass distribution of A1689 is well constrained, we are able to calculate the intrinsic sensitivity of the observations as a function of source plane position, allowing for accurate determinations of effective volume as a function of luminosity. We fit the faint-end slope of the luminosity function to be α = –1.74 ± 0.08, which is consistent with the values obtained for 2.5 < z < 6. Notably, there is no turnover in the luminosity function down to M {sub 1500} = –13 AB mag. We fit the UV spectral slopes with photometry from existing Hubble optical imaging. The observed trend of increasingly redder slopes with luminosity at higher redshifts is observed in our sample, but with redder slopes at all luminosities and average reddening of (E(B – V)) = 0.15 mag. We assume the stars in these galaxies are metal poor (0.2 Z {sub ☉}) compared to their brighter counterparts (Z {sub ☉}), resulting in bluer assumed intrinsic UV slopes and larger derived values for dust extinction. The total UV luminosity density at z ∼ 2 is 4.31{sub −0.60}{sup +0.68}×10{sup 26} erg s{sup –1} Hz{sup –1} Mpc{sup –3}, more than 70% of which is emitted by galaxies in the luminosity range of our sample. Finally, we determine the global star formation rate density from UV-selected galaxies at z ∼ 2 (assuming a constant dust extinction correction of 4.2 over all luminosities and a Kroupa initial mass function) of 0.148{sub −0.020}{sup +0.023} M {sub ☉} yr{sup –1} Mpc{sup –3}, significantly higher than previous determinations because of the additional population of fainter galaxies and the larger dust correction factors.« less

The Hadean, Through a Glass Telescopically: Observations of Young Solar Analogs

NASA Technical Reports Server (NTRS)

Gaidos, E. J.

1998-01-01

Investigations into the Earth's surface environment during the Hadean eon (prior to 3.8 Ga) are hampered by the paucity of the geological and geochemical record and the relative inaccessibility of better-preserved surfaces with possibly similar early histories (i.e., Mars). One approach is to observe nearby, young solar-mass stars as analogs to the Hadean Sun and its environment. A catalog of 38 G and early K stars within 25 pc was constructed based on main-sequence status, bolometric luminosity, lack of known stellar companions within 800 AU, and coronal X-ray luminosities commensurate with the higher activity of solar-mass stars <0.8 b.y. old. Spectroscopic data support the assignment of ages of 0.2 - 0.8 Ga for most of these stars. Observations of these objects will provide insight into external forces that influenced Hadean atmosphere, ocean, and surface evolution (and potential ecosystems), including solar luminosity evolution, the flux and spectrum of solar ultraviolet radiation, the intensity of the solar wind, and the intensity and duration of a late period of heavy bombardment. The standard model of solar evolution predicts a luminosity of 0.75 solar luminosity at the end of the Hadean, implying a terrestrial surface temperature inconsistent with the presence of liquid water and motivating atmospheric greenhouse models. An alternative model fo solar evolution that invokes mass loss, constructed to explain solar Li depletion, attenuates or reverses this luminosity evolution of the atmospheres of Earth and the other terrestrial planets. This model can be tested by Li abundance measurements. The continuum emission from stellar wind plasma during significant mass loss may be detectable at millimeter and radio wavelengths. The Earth (and Moon) experienced a period of intense bombardment prior to 3.8 Ga, long after accretion was completed in the inner solar system and possibly associated with the clearing of residual planetesimals in the outer solar system. Such a bombardment may have contributed volatiles and organics to the surface, but also have limited the appearacne of a biosphere. While planetary systems around solar systems cannot be detected directly with present technology, the thermal emission from the interplanetary dust generated during a similar heavy bombardment period can be. Midinfrared observations of a large uniform sample of solar analogs are used to constrain the frequency and duration of such events.

Galaxies at z~7-8: z850-Dropouts in the Hubble Ultra Deep Field

NASA Astrophysics Data System (ADS)

Bouwens, R. J.; Thompson, R. I.; Illingworth, G. D.; Franx, M.; van Dokkum, P. G.; Fan, X.; Dickinson, M. E.; Eisenstein, D. J.; Rieke, M. J.

2004-12-01

We have detected likely z~7-8 galaxies in the 144''×144'' Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) observations of the Hubble Ultra Deep Field. Objects are required to be >=3 σ detections in both NICMOS bands, J110 and H160. The selection criteria for this sample are (z850-J110)AB>0.8, (z850-J110)AB>0.66(J110-H160)AB+0.8, (J110-H160)AB<1.2 and no detection at less than 8500 Å. The five selected sources have total magnitudes H160,AB~27. Four of the five sources are quite blue compared to typical lower redshift dropout galaxies and are clustered within a 1 arcmin2 region. Because all five sources are near the limit of the NICMOS data, we have carefully evaluated their reality. Each of the candidates is visible in different splits of the data and a median stack. We analyzed several noise images and estimate the number of spurious sources to be 1+/-1. A search using an independent reduction of this same data set clearly revealed three of the five candidates and weakly detected a fourth candidate, suggesting that the contamination could be higher. For comparison with predictions from lower redshift samples, we take a conservative approach and adopt four z~7-8 galaxies as our sample. With the same detection criteria on simulated data sets, assuming no evolution from z~3.8, we predict 10 sources at z~7-8, or 14 if we use a more realistic (1+z)-1 size scaling. We estimate that the rest-frame continuum UV (~1800 Å) luminosity density at z~7.5 (integrated down to 0.3L*z=3) is just 0.20+0.12-0.08 times that found at z~3.8 (or 0.20+0.23-0.12 times this quantity including cosmic variance). Effectively this sets an upper limit on the luminosity density down to 0.3L*z=3 and is consistent with significant evolution at the bright end of the luminosity function from z~7.5 to 3.8. Even with the lower UV luminosity density at z~7.5, it appears that galaxies could still play an important role in reionization at these redshifts, although definitive measurements remain to be made. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

VLTI/AMBER spectro-interferometry of the late-type supergiants V766 Cen (=HR 5171 A), σ Oph, BM Sco, and HD 206859

NASA Astrophysics Data System (ADS)

Wittkowski, M.; Arroyo-Torres, B.; Marcaide, J. M.; Abellan, F. J.; Chiavassa, A.; Guirado, J. C.

2017-01-01

Aims: We add four warmer late-type supergiants to our previous spectro-interferometric studies of red giants and supergiants. Methods: We measure the near-continuum angular diameter, derive fundamental parameters, discuss the evolutionary stage, and study extended atmospheric atomic and molecular layers. Results: V766 Cen (=HR 5171 A) is found to be a high-luminosity (log L/L⊙ = 5.8 ± 0.4) source of effective temperature 4290 ± 760 K and radius 1490 ± 540 R⊙, located in the Hertzsprung-Russell (HR) diagram close to both the Hayashi limit and Eddington limit; this source is consistent with a 40 M⊙ evolutionary track without rotation and current mass 27-36 M⊙. V766 Cen exhibits Na I in emission arising from a shell of radius 1.5 RPhot and a photocenter displacement of about 0.1 RPhot. It shows strong extended molecular (CO) layers and a dusty circumstellar background component. The other three sources are found to have lower luminosities of about log L/L⊙ = 3.4-3.5, corresponding to 5-9 M⊙ evolutionary tracks. They cover effective temperatures of 3900 K to 5300 K and radii of 60-120 R⊙. They do not show extended molecular layers as observed for higher luminosity RSGs of our sample. BM Sco shows an unusually strong contribution by an over-resolved circumstellar dust component. Conclusions: V766 Cen is a red supergiant located close to the Hayashi limit instead of a yellow hypergiant already evolving back toward warmer effective temperatures as discussed in the literature. Our observations of the Na I line and the extended molecular layers suggest an optically thick pseudo-photosphere at about 1.5 RPhot at the onset of the wind. The stars σ Oph, BM Sco, and HD 206859 are more likely high-mass red giants instead of RSGs as implied by their luminosity class Ib. This leaves us with an unsampled locus in the HR diagram corresponding to luminosities log L/L⊙ 3.8-4.8 or masses 10-13 M⊙, possibly corresponding to the mass region where stars explode as (type II-P) supernovae during the red supergiant stage. With V766 Cen, we now confirm that our previously found relation of increasing strength of extended molecular layers with increasing luminosities extends to double our previous luminosities and up to the Eddington limit. This might further point to steadily increasing radiative winds with increasing luminosity. Based on observations made with the VLT Interferometer (VLTI) at Paranal Observatory under program ID 093.D-0014.

The properties of the extended warm ionised gas around low-redshift QSOs and the lack of extended high-velocity outflows

NASA Astrophysics Data System (ADS)

Husemann, B.; Wisotzki, L.; Sánchez, S. F.; Jahnke, K.

2013-01-01

We present a detailed analysis of a large sample of 31 low-redshift, mostly radio-quiet type 1 quasi-stellar objects (QSOs) observed with integral field spectroscopy to study their extended emission-line regions (EELRs). We focus on the ionisation state of the gas, size and luminosity of extended narrow line regions (ENLRs), which corresponds to those parts of the EELR dominated by ionisation from the QSO, as well as the kinematics of the ionised gas. We detect EELRs around 19 of our 31 QSOs (61%) after deblending the unresolved QSO emission and the extended host galaxy light in the integral field data with a new dedicated algorithm. Based on standard emission-line diagnostics we identify 13 EELRs to be entirely ionised by the QSO radiation, 3 EELRs are composed of H ii regions and 3 EELRs display signatures of both ionisation mechanisms at different locations. The typical size of the ENLR is ~10 kpc at a median nuclear [O iii] luminosity of log (L([O iii])/ [ergs-1]) = 42.7 ± 0.15. We show that the ENLR sizes are least a factor of ~2 larger than determined with the Hubble Space Telescope, but are consistent with those of recently reported type 2 QSOs at matching [O iii] luminosities. The ENLR of type 1 and type 2 QSOs therefore appear to follow the same size-luminosity relation. Furthermore, we show for the first time that the ENLR size is much better correlated with the QSO continuum luminosity than with the total/nuclear [O iii] luminosity. We show that ENLR luminosity and radio luminosity are correlated, and argue that radio jets even in radio-quiet QSOs are important for shaping the properties of the ENLR. Strikingly, the kinematics of the ionised gas is quiescent and likely gravitationally driven in the majority of cases and we find only 3 objects with radial gas velocities exceeding >400 km s-1 in specific regions of the EELR that can be associate with radio jets. In general, these are significantly lower outflow velocities and detection rates compared to starburst galaxies or radio-loud QSOs. This represent a challenge for some theoretical feedback models in which luminous QSOs are expected to radiatively drive an outflow out to scales of the entire host galaxy. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max- Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC).Tables 3, 4, and 7 are available in electronic form at http://www.aanda.org

H2O from R Cas: ISO LWS-SWS observations and detailed modelling

NASA Astrophysics Data System (ADS)

Truong-Bach; Sylvester, R. J.; Barlow, M. J.; Nguyen-Q-Rieu; Lim, T.; Liu, X. W.; Baluteau, J. P.; Deguchi, S.; Justtanont, K.; Tielens, A. G. G. M.

1999-05-01

We present 29-197 mu m spectra of the oxygen-rich Mira variable star, R Cas, obtained with the Long- and Short- Wavelength Spectrometers (LWS and SWS) on board the Infrared Space Observatory (ISO). The LWS grating observations were made during two pulsational stellar phases, phi { ~ } 0.5 and 0.2 in August 1996 and June 1997 when the stellar luminosity was near its minimum and mean values, respectively. The infrared flux at the latter epoch was { ~ } 30-40% stronger than at the former. SWS grating observations were also made in June 1997. The spectrum presents a strong far-infrared (FIR) continuum and is rich in water lines suitable for use as circumstellar diagnostics. We have constructed a circumstellar model which consistently treats radiative transfer, chemical exchanges, photodissociation, and heating and cooling effects. The overall FIR excitation field was scaled by a factor which varied with the stellar phase. By fitting the model to the observed FIR water line fluxes and continuum while adopting the stellar parameters based on the Hipparcos distance we have found a mass-loss rate of dot {M} { ~ } 3.4*E(-7) Msun yr(-1) and a total ortho and para water vapour abundance (relative to {H_2} ) of f { ~ } 1.1x\\ex{-5}. The kinetic temperature and the relative abundances of {H2O} , OH, and O in chemical equilibrium have been derived as functions of radial distance r. {H2O} excitation is mainly dominated by FIR emitted by dust grains. The deduced model continuum flux at 29-197 mu m for the phi ~ 0.5 phase was 61% of the flux at phi ~ 0.2. Photodissociation by the FUV interstellar field and CO cooling effects operate farther out than the {H2O} excitation region. Our derived mass-loss rate of R Cas is similar to the value 6x\\ex{-7} Msun yr(-1) previously published for WHya, another oxygen-rich AGB star. Based on observations with ISO, an ESA project with instruments funded by ESA Members States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Can the Lyman Continuum Leaked Out of H II Regions Explain Diffuse Ionized Gas?

NASA Astrophysics Data System (ADS)

Seon, Kwang-Il

2009-09-01

We present an attempt to explain the diffuse Hα emission of a face-on galaxy M 51 with the "standard" photoionization model, in which the Lyman continuum (Lyc) escaping from H II regions propagates large distances into the diffuse interstellar medium (ISM). The diffuse Hα emission of M 51 is analyzed using thin slab models and exponential disk models in the context of the "on-the-spot" approximation. The scale height of the ionized gas needed to explain the diffuse Hα emission with the scenario is found to be of the order of ~1-2 kpc, consistent with those of our Galaxy and edge-on galaxies. The model also provides a vertical profile, when the galaxy is viewed edge-on, consisting of two-exponential components. However, it is found that an incredibly low absorption coefficient of κ0 ≈ 0.4-0.8 kpc-1 at the galactic plane, or, equivalently, an effective cross section as low as σeff ~ 10-5 of the photoionization cross section at 912 Å is required to allow the stellar Lyc photons to travel through the H I disk. Such a low absorption coefficient is out of accord with the properties of the ISM. Furthermore, we found that even the model that has the diffuse ionized gas (DIG) phase only and no H I gas phase shows highly concentrated Hα emissions around H II regions, and can account for only lsim26% of the Hα luminosity of the DIG. This result places a strong constraint on the ionizing source of the DIG. We also report that the Hα intensity distribution functions not only of the DIG, but also of H II regions in M 51, appear to be lognormal.

COLLIMATION AND SCATTERING OF THE ACTIVE GALACTIC NUCLEUS EMISSION IN THE SOMBRERO GALAXY

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

Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br

2013-03-10

We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{alpha} emission line. The collimation and scattering of this broad H{alpha} component was also revealed by fitting the [N II] {lambda}{lambda}6548, 6583 and H{alpha} emission linesmore » as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18 Degree-Sign {+-} 13 Degree-Sign and P.A. = 162 Degree-Sign {+-} 13 Degree-Sign ) along a direction perpendicular to the torus/disk (P.A. = 72 Degree-Sign {+-} 14 Degree-Sign ) suggests that this structure is approximately edge-on and collimates the AGN emission. The edge-on torus/disk also hides the broad-line region. The proposed scenario is compatible with the unified model and explains why only a weak broad component of the H{alpha} emission line is visible and also why many previous studies detected no broad H{alpha}. The technique used here proved to be an efficient method not only for detecting scattered light, but also for testing the unified model in low-luminosity AGNs.« less

Revealing structure and evolution within the corona of the Seyfert galaxy I Zw 1

NASA Astrophysics Data System (ADS)

Wilkins, D. R.; Gallo, L. C.; Silva, C. V.; Costantini, E.; Brandt, W. N.; Kriss, G. A.

2017-11-01

X-ray spectral timing analysis is presented of XMM-Newton observations of the narrow-line Seyfert 1 galaxy I Zwicky 1 taken in 2015 January. After exploring the effect of background flaring on timing analyses, X-ray time lags between the reflection-dominated 0.3-1.0 keV energy and continuum-dominated 1.0-4.0 keV band are measured, indicative of reverberation off the inner accretion disc. The reverberation lag time is seen to vary as a step function in frequency; across lower frequency components of the variability, 3 × 10-4-1.2 × 10-3 Hz a lag of 160 s is measured, but the lag shortens to (59 ± 4) s above 1.2 × 10-3 Hz. The lag-energy spectrum reveals differing profiles between these ranges with a change in the dip showing the earliest arriving photons. The low-frequency signal indicates reverberation of X-rays emitted from a corona extended at low height over the disc, while at high frequencies, variability is generated in a collimated core of the corona through which luminosity fluctuations propagate upwards. Principal component analysis of the variability supports this interpretation, showing uncorrelated variation in the spectral slope of two power-law continuum components. The distinct evolution of the two components of the corona is seen as a flare passes inwards from the extended to the collimated portion. An increase in variability in the extended corona was found preceding the initial increase in X-ray flux. Variability from the extended corona was seen to die away as the flare passed into the collimated core leading to a second sharper increase in the X-ray count rate.

Alma Survey of Circumstellar Disks in the Young Stellar Cluster IC 348

NASA Astrophysics Data System (ADS)

Ruíz-Rodríguez, D.; Cieza, L. A.; Williams, J. P.; Andrews, S. M.; Principe, D. A.; Caceres, C.; Canovas, H.; Casassus, S.; Schreiber, M. R.; Kastner, J. H.

2018-05-01

We present a 1.3 mm continuum survey of the young (2-3 Myr) stellar cluster IC 348, which lies at a distance of 310 pc, and is dominated by low-mass stars (M⋆ ˜ 0.1-0.6 M⊙). We observed 136 Class II sources (disks that are optically thick in the infrared) at 0.8″ (200 au) resolution with a 3σ sensitivity of ˜ 0.45 mJy (Mdust ˜ 1.3 M⊕). We detect 40 of the targets and construct a mm-continuum luminosity function. We compare the disk mass distribution in IC 348 to those of younger and older regions, taking into account the dependence on stellar mass. We find a clear evolution in disk masses from 1 to 5-10 Myr. The disk masses in IC 348 are significantly lower than those in Taurus (1-3 Myr) and Lupus (1-3 Myr), similar to those of Chamaleon I, (2-3 Myr) and σ Ori (3-5 Myr) and significantly higher than in Upper Scorpius (5-10 Myr). About 20 disks in our sample (˜5% of the cluster members) have estimated masses (dust + gas) >1 MJup and hence might be the precursors of giant planets in the cluster. Some of the most massive disks include transition objects with inner opacity holes based on their infrared SEDs. From a stacking analysis of the 96 non-detections, we find that these disks have a typical dust mass of just ≲ 0.4 M⊕, even though the vast majority of their infrared SEDs remain optically thick and show little signs of evolution. Such low-mass disks may be the precursors of the small rocky planets found by Kepler around M-type stars.

The NGC 7742 star cluster luminosity function: a population analysis revisited

NASA Astrophysics Data System (ADS)

de Grijs, Richard; Ma, Chao

2018-02-01

We re-examine the properties of the star cluster population in the circumnuclear starburst ring in the face-on spiral galaxy NGC 7742, whose young cluster mass function has been reported to exhibit significant deviations from the canonical power law. We base our reassessment on the clusters’ luminosities (an observational quantity) rather than their masses (a derived quantity), and confirm conclusively that the galaxy’s starburst-ring clusters—and particularly the youngest subsample, {log}(t {{{yr}}}-1)≤ 7.2—show evidence of a turnover in the cluster luminosity function well above the 90% completeness limit adopted to ensure the reliability of our results. This confirmation emphasizes the unique conundrum posed by this unusual cluster population.

Dark-ages reionization and galaxy formation simulation - IV. UV luminosity functions of high-redshift galaxies

NASA Astrophysics Data System (ADS)

Liu, Chuanwu; Mutch, Simon J.; Angel, P. W.; Duffy, Alan R.; Geil, Paul M.; Poole, Gregory B.; Mesinger, Andrei; Wyithe, J. Stuart B.

2016-10-01

In this paper, we present calculations of the UV luminosity function (LF) from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations project, which combines N-body, semi-analytic and seminumerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from z ˜ 5 through to z ˜ 10. We investigate the luminosity-star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of 0.1-0.3 dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our calculated luminosities to investigate the LF below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below current detection limits and becomes flat at MUV ≳ -14. We find that 48 (17) per cent of the total UV flux at z ˜ 6 (10) has been detected above an observational limit of MUV ˜ -17, and that galaxies fainter than MUV ˜ -17 are the main source of ionizing photons for reionization. We investigate the luminosity-stellar mass relation, and find a correlation for galaxies with MUV < -14 that has the form M_{ast } ∝ 10^{-0.47M_UV}, in good agreement with observations, but which flattens for fainter galaxies. We determine the luminosity-halo mass relation to be M_vir ∝ 10^{-0.35M_UV}, finding that galaxies with MUV = -20 reside in host dark matter haloes of 1011.0±0.1 M⊙ at z ˜ 6, and that this mass decreases towards high redshift.

MEASURING THE LUMINOSITY AND VIRIAL BLACK HOLE MASS DEPENDENCE OF QUASAR–GALAXY CLUSTERING AT z ∼ 0.8

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

Krolewski, Alex G.; Eisenstein, Daniel J., E-mail: akrolewski@college.harvard.edu

2015-04-10

We study the dependence of quasar clustering on quasar luminosity and black hole mass by measuring the angular overdensity of photometrically selected galaxies imaged by the Wide-field Infrared Survey Explorer (WISE) about z ∼ 0.8 quasars from SDSS. By measuring the quasar–galaxy cross-correlation function and using photometrically selected galaxies, we achieve a higher density of tracer objects and a more sensitive detection of clustering than measurements of the quasar autocorrelation function. We test models of quasar formation and evolution by measuring the luminosity dependence of clustering amplitude. We find a significant overdensity of WISE galaxies about z ∼ 0.8 quasarsmore » at 0.2–6.4 h{sup −1} Mpc in projected comoving separation. We find no appreciable increase in clustering amplitude with quasar luminosity across a decade in luminosity, and a power-law fit between luminosity and clustering amplitude gives an exponent of −0.01 ± 0.06 (1 σ error). We also fail to find a significant relationship between clustering amplitude and black hole mass, although our dynamic range in true mass is suppressed due to the large uncertainties in virial black hole mass estimates. Our results indicate that a small range in host dark matter halo mass maps to a large range in quasar luminosity.« less

The 2-10 keV unabsorbed luminosity function of AGN from the LSS, CDFS, and COSMOS surveys

NASA Astrophysics Data System (ADS)

Ranalli, P.; Koulouridis, E.; Georgantopoulos, I.; Fotopoulou, S.; Hsu, L.-T.; Salvato, M.; Comastri, A.; Pierre, M.; Cappelluti, N.; Carrera, F. J.; Chiappetti, L.; Clerc, N.; Gilli, R.; Iwasawa, K.; Pacaud, F.; Paltani, S.; Plionis, E.; Vignali, C.

2016-05-01

The XMM-Large scale structure (XMM-LSS), XMM-Cosmological evolution survey (XMM-COSMOS), and XMM-Chandra deep field south (XMM-CDFS) surveys are complementary in terms of sky coverage and depth. Together, they form a clean sample with the least possible variance in instrument effective areas and point spread function. Therefore this is one of the best samples available to determine the 2-10 keV luminosity function of active galactic nuclei (AGN) and their evolution. The samples and the relevant corrections for incompleteness are described. A total of 2887 AGN is used to build the LF in the luminosity interval 1042-1046 erg s-1 and in the redshift interval 0.001-4. A new method to correct for absorption by considering the probability distribution for the column density conditioned on the hardness ratio is presented. The binned luminosity function and its evolution is determined with a variant of the Page-Carrera method, which is improved to include corrections for absorption and to account for the full probability distribution of photometric redshifts. Parametric models, namely a double power law with luminosity and density evolution (LADE) or luminosity-dependent density evolution (LDDE), are explored using Bayesian inference. We introduce the Watanabe-Akaike information criterion (WAIC) to compare the models and estimate their predictive power. Our data are best described by the LADE model, as hinted by the WAIC indicator. We also explore the recently proposed 15-parameter extended LDDE model and find that this extension is not supported by our data. The strength of our method is that it provides unabsorbed, non-parametric estimates, credible intervals for luminosity function parameters, and a model choice based on predictive power for future data. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and NASA.Tables with the samples of the posterior probability distributions are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A80

Molecular continua for polymeric liquids in large-amplitude oscillatory shear flow

NASA Astrophysics Data System (ADS)

Giacomin, A. Jeffrey; Saengow, Chaimongkol

2018-05-01

In this paper, we connect a molecular description of the rheology of a polymeric liquid to a continuum description, and then test this connection for large-amplitude oscillatory shear (LAOS) flow. Specifically, for the continuum description, we use the 6-constant Oldroyd framework, and for the molecular, we use the simplest relevant molecular model, the suspension of rigid dumbbells. By relevant, we mean predicting at least higher harmonics in the shear stress response in LAOS. We call this connection a molecular continuum, and we examine two ways of arriving at this connection. The first goes through the retarded motion expansion, and the second expands each of a set of specific material functions (complex, steady shear, and steady uniaxial extensional viscosities). Both ways involve in comparing the coefficients of expansions and then solve for the six constants of the continuum framework in terms of the two constants of the rigid dumbbell suspension. The purpose of a molecular continuum is that many well-known results for rigid dumbbell suspensions in other flow fields can also be easily obtained, without having to firstly find the orientation distribution function. In this paper, we focus on the recent result for the rigid dumbbell suspension in LAOS. We compare the accuracies of the retarded motion molecular continuum (RMMC) with the material function molecular continuum (MFMC). We find the RMMC to be the most accurate for LAOS.

Spectroscopic properties of luminous Ly α emitters at z ≈ 6-7 and comparison to the Lyman-break population

NASA Astrophysics Data System (ADS)

Matthee, Jorryt; Sobral, David; Darvish, Behnam; Santos, Sérgio; Mobasher, Bahram; Paulino-Afonso, Ana; Röttgering, Huub; Alegre, Lara

2017-11-01

We present spectroscopic follow-up of candidate luminous Ly α emitters (LAEs) at z = 5.7-6.6 in the SA22 field with VLT/X-SHOOTER. We confirm two new luminous LAEs at z = 5.676 (SR6) and z = 6.532 (VR7), and also present HST follow-up of both sources. These sources have luminosities LLy α ≈ 3 × 1043 erg s-1, very high rest-frame equivalent widths of EW0 ≳ 200 Å and narrow Ly α lines (200-340 km s-1). VR7 is the most UV-luminous LAE at z > 6.5, with M1500 = -22.5, even brighter in the UV than CR7. Besides Ly α, we do not detect any other rest-frame UV lines in the spectra of SR6 and VR7, and argue that rest-frame UV lines are easier to observe in bright galaxies with low Ly α equivalent widths. We confirm that Ly α line widths increase with Ly α luminosity at z = 5.7, while there are indications that Ly α lines of faint LAEs become broader at z = 6.6, potentially due to reionization. We find a large spread of up to 3 dex in UV luminosity for >L⋆ LAEs, but find that the Ly α luminosity of the brightest LAEs is strongly related to UV luminosity at z = 6.6. Under basic assumptions, we find that several LAEs at z ≈ 6-7 have Ly α escape fractions ≳ 100 per cent, indicating bursty star formation histories, alternative Ly α production mechanisms, or dust attenuating Ly α emission differently than UV emission. Finally, we present a method to compute ξion, the production efficiency of ionizing photons, and find that LAEs at z ≈ 6-7 have high values of log10(ξion/Hz erg-1) ≈ 25.51 ± 0.09 that may alleviate the need for high Lyman-Continuum escape fractions required for reionization.

The Keck/OSIRIS Nearby AGN Survey (KONA). I. The Nuclear K-band Properties of Nearby AGN

NASA Astrophysics Data System (ADS)

Müller-Sánchez, F.; Hicks, E. K. S.; Malkan, M.; Davies, R.; Yu, P. C.; Shaver, S.; Davis, B.

2018-05-01

We introduce the Keck OSIRIS Nearby AGN survey (KONA), a new adaptive optics-assisted integral-field spectroscopic survey of Seyfert galaxies. KONA permits at ∼0.″1 resolution a detailed study of the nuclear kinematic structure of gas and stars in a representative sample of 40 local bona fide active galactic nucleus (AGN). KONA seeks to characterize the physical processes responsible for the coevolution of supermassive black holes and galaxies, principally inflows and outflows. With these IFU data of the nuclear regions of 40 Seyfert galaxies, the KONA survey will be able to study, for the first time, a number of key topics with meaningful statistics. In this paper we study the nuclear K-band properties of nearby AGN. We find that the K-band (2.1 μm) luminosities of the compact Seyfert 1 nuclei are correlated with the hard X-ray luminosities, implying a non-stellar origin for the majority of the continuum emission. The best-fit correlation is log L K = 0.9log L 2–10 keV + 4 over three orders of magnitude in both K-band and X-ray luminosities. We find no strong correlation between 2.1 μm luminosity and hard X-ray luminosity for the Seyfert 2 galaxies. The spatial extent and spectral slope of the Seyfert 2 galaxies indicate the presence of nuclear star formation and attenuating material (gas and dust), which in some cases is compact and in some galaxies extended. We detect coronal-line emission in 36 galaxies and for the first time in 5 galaxies. Finally, we find 4/20 galaxies that are usually classified as Seyfert 2 based on their optical spectra exhibit a broad component of Brγ emission, and one galaxy (NGC 7465) shows evidence of a double nucleus. Based on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Galaxy and Mass Assembly (GAMA): ugriz galaxy luminosity functions

NASA Astrophysics Data System (ADS)

Loveday, J.; Norberg, P.; Baldry, I. K.; Driver, S. P.; Hopkins, A. M.; Peacock, J. A.; Bamford, S. P.; Liske, J.; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cameron, E.; Conselice, C. J.; Croom, S. M.; Frenk, C. S.; Gunawardhana, M.; Hill, D. T.; Jones, D. H.; Kelvin, L. S.; Kuijken, K.; Nichol, R. C.; Parkinson, H. R.; Phillipps, S.; Pimbblet, K. A.; Popescu, C. C.; Prescott, M.; Robotham, A. S. G.; Sharp, R. G.; Sutherland, W. J.; Taylor, E. N.; Thomas, D.; Tuffs, R. J.; van Kampen, E.; Wijesinghe, D.

2012-02-01

Galaxy and Mass Assembly (GAMA) is a project to study galaxy formation and evolution, combining imaging data from ultraviolet to radio with spectroscopic data from the AAOmega spectrograph on the Anglo-Australian Telescope. Using data from Phase 1 of GAMA, taken over three observing seasons, and correcting for various minor sources of incompleteness, we calculate galaxy luminosity functions (LFs) and their evolution in the ugriz passbands. At low redshift, z < 0.1, we find that blue galaxies, defined according to a magnitude-dependent but non-evolving colour cut, are reasonably well fitted over a range of more than 10 magnitudes by simple Schechter functions in all bands. Red galaxies, and the combined blue plus red sample, require double power-law Schechter functions to fit a dip in their LF faintwards of the characteristic magnitude M* before a steepening faint end. This upturn is at least partly due to dust-reddened disc galaxies. We measure the evolution of the galaxy LF over the redshift range 0.002 < z < 0.5 both by using a parametric fit and by measuring binned LFs in redshift slices. The characteristic luminosity L* is found to increase with redshift in all bands, with red galaxies showing stronger luminosity evolution than blue galaxies. The comoving number density of blue galaxies increases with redshift, while that of red galaxies decreases, consistent with prevailing movement from blue cloud to red sequence. As well as being more numerous at higher redshift, blue galaxies also dominate the overall luminosity density beyond redshifts z≃ 0.2. At lower redshifts, the luminosity density is dominated by red galaxies in the riz bands, and by blue galaxies in u and g.

The discovery of nonthermal radio emission from magnetic Bp-Ap stars

NASA Technical Reports Server (NTRS)

Drake, Stephen A.; Abbott, David C.; Bastian, T. S.; Bieging, J. H.; Churchwell, E.

1987-01-01

In a VLA survey of chemically peculiar B- and A-type stars with strong magnetic fields, five of the 34 stars observed have been identified as 6 cm continuum sources. Three of the detections are helium-strong early Bp stars (Sigma Ori E, HR 1890, and Delta Ori C), and two are helium weak, silicon-strong stars with spectral types near A0p (IQ Aur = HD 34452, Babcock's star = HD 215441). The 6 cm luminosities L6 (ergs/s Hz) range from log L6 = 16.2 to 17.9, somewhat less than the OB supergiants and W-R stars. Three-frequency observations indicate that the helium-strong Bp stars are variable nonthermal sources.

An X-ray image of the violent interstellar medium in 30 Doradus

NASA Technical Reports Server (NTRS)

Wang, Q.; Helfand, D. J.

1991-01-01

A detailed analysis of the X-ray emission from the largest H II region complex in the Local Group, 30 Dor, is presented. Applying a new maximum entropy deconvolution algorithm to the Einstein Observatory data, reveals striking correlations among the X-ray, radio, and optical morphologies of the region, with X-ray-emitting bubbles filling cavities surrounded by H-alpha shells and coextensive diffuse X-ray and radio continuum emission from throughout the region. The total X-ray luminosity in the 0.16-3.5 keV band from an area within 160 pc of the central cluster R136 is about 2 x 10 to the 37th ergs/sec.

Documentation for the machine-readable version of the Stellar Spectrophotometric Atlas, 3130 A lambda 10800 A of Gunn and Stryker (1983)

NASA Technical Reports Server (NTRS)

Warren, W. H., Jr.

1984-01-01

The machine-readable version of the Atlas as it is currently being distributed from the Astronomical Data Center is described. The data were obtained with the Oke multichannel scanner on the 5-meter Hale reflector for purposes of synthesizing galaxy spectra, and the digitized Atlas contains normalized spectral energy distributions, computed colors, scan line and continuum indices for 175 selected stars covering the complete ranges of spectral type and luminosity class. The documentation includes a byte-by-byte format description, a table of the indigenous characteristics of the magnetic tape file, and a sample listing of logical records exactly as they are recorded on the tape.

A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Third Data Release

NASA Astrophysics Data System (ADS)

Trump, Jonathan R.; Hall, Patrick B.; Reichard, Timothy A.; Richards, Gordon T.; Schneider, Donald P.; Vanden Berk, Daniel E.; Knapp, Gillian R.; Anderson, Scott F.; Fan, Xiaohui; Brinkman, J.; Kleinman, S. J.; Nitta, Atsuko

2006-07-01

We present a total of 4784 unique broad absorption line quasars from the Sloan Digital Sky Survey Third Data Release. An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000 km s-1 in the C IV and Mg II absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift, with the power-law spectral index and amount of dust reddening as additional free parameters. We characterize our sample through the traditional ``balnicity'' index and a revised absorption index, as well as through parameters such as the width, outflow velocity, fractional depth, and number of troughs. From a sample of 16,883 quasars at 1.7<=z<=4.38, we identify 4386 (26.0%) quasars with broad C IV absorption, of which 1756 (10.4%) satisfy traditional selection criteria. From a sample of 34,973 quasars at 0.5<=z<=2.15, we identify 457 (1.31%) quasars with broad Mg II absorption, 191 (0.55%) of which satisfy traditional selection criteria. We also provide a supplementary list of 39 visually identified z>4.38 quasars with broad C IV absorption. We find that broad absorption line quasars may have broader emission lines on average than other quasars.

Accelerated Evolution of the Lyα Luminosity Function at z >~ 7 Revealed by the Subaru Ultra-deep Survey for Lyα Emitters at z = 7.3

NASA Astrophysics Data System (ADS)

Konno, Akira; Ouchi, Masami; Ono, Yoshiaki; Shimasaku, Kazuhiro; Shibuya, Takatoshi; Furusawa, Hisanori; Nakajima, Kimihiko; Naito, Yoshiaki; Momose, Rieko; Yuma, Suraphong; Iye, Masanori

2014-12-01

We present the ultra-deep Subaru narrowband imaging survey for Lyα emitters (LAEs) at z = 7.3 in the Subaru/XMM-Newton Deep Survey (SXDS) and Cosmic Evolution Survey (COSMOS) fields (~0.5 deg2) with a total integration time of 106 hr. Exploiting our new sharp bandwidth filter, NB101, installed on the Suprime-Cam, we have reached L(Lyα) = 2.4 × 1042 erg s-1 (5σ) for z = 7.3 LAEs, about four times deeper than previous Subaru z >~ 7 studies, which allows us to reliably investigate the evolution of the Lyα luminosity function (LF) for the first time down to the luminosity limit same as those of Subaru z = 3.1-6.6 LAE samples. Surprisingly, we only find three and four LAEs in the SXDS and COSMOS fields, respectively, while one expects a total of ~65 LAEs by our survey in the case of no Lyα LF evolution from z = 6.6 to 7.3. We identify a decrease of the Lyα LF from z = 6.6 to 7.3 at the >90% confidence level from our z = 7.3 Lyα LF with the best-fit Schechter parameters of L*{Lyα } = 2.7+8.0-1.2 × 1042 {erg} {s}-1 and φ * = 3.7+17.6-3.3 × 10-4 {Mpc}-3 for a fixed α = -1.5. Moreover, the evolution of the Lyα LF is clearly accelerated at z > 6.6 beyond the measurement uncertainties including cosmic variance. Because no such accelerated evolution of the UV-continuum LF or the cosmic star formation rate (SFR) is found at z ~ 7, but suggested only at z > 8, this accelerated Lyα LF evolution is explained by physical mechanisms different from a pure SFR decrease but related to the Lyα production and escape in the process of cosmic reionization. Because a simple accelerating increase of intergalactic medium neutral hydrogen absorbing Lyα cannot be reconciled with Thomson scattering of optical depth measurements from WMAP and Planck, our findings may support new physical pictures suggested by recent theoretical studies, such as the existence of HI clumpy clouds within cosmic ionized bubbles that are selectively absorbing Lyα and the large ionizing photon escape fraction of galaxies causing weak Lyα emission.

LUMINOSITY FUNCTIONS OF LMXBs IN CENTAURUS A: GLOBULAR CLUSTERS VERSUS THE FIELD

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

Voss, Rasmus; Gilfanov, Marat; Sivakoff, Gregory R.

2009-08-10

We study the X-ray luminosity function (XLF) of low-mass X-ray binaries (LMXB) in the nearby early-type galaxy Centaurus A, concentrating primarily on two aspects of binary populations: the XLF behavior at the low-luminosity limit and the comparison between globular cluster and field sources. The 800 ksec exposure of the deep Chandra VLP program allows us to reach a limiting luminosity of {approx}8 x 10{sup 35} erg s{sup -1}, about {approx}2-3 times deeper than previous investigations. We confirm the presence of the low-luminosity break of the overall LMXB XLF at log(L{sub X} ) {approx} 37.2-37.6, below which the luminosity distribution followsmore » a dN/d(ln L) {approx} const law. Separating globular cluster and field sources, we find a statistically significant difference between the two luminosity distributions with a relative underabundance of faint sources in the globular cluster population. This demonstrates that the samples are drawn from distinct parent populations and may disprove the hypothesis that the entire LMXB population in early-type galaxies is created dynamically in globular clusters. As a plausible explanation for this difference in the XLFs, we suggest an enhanced fraction of helium-accreting systems in globular clusters, which are created in collisions between red giants and neutron stars. Due to the four times higher ionization temperature of He, such systems are subject to accretion disk instabilities at {approx}20 times higher mass accretion rate and, therefore, are not observed as persistent sources at low luminosities.« less

The Abundance of Low-Luminosity Lyα Emitters at High Redshift

NASA Astrophysics Data System (ADS)

Santos, Michael R.; Ellis, Richard S.; Kneib, Jean-Paul; Richard, Johan; Kuijken, Konrad

2004-05-01

We derive the luminosity function of high-redshift Lyα-emitting sources from a deep, blind, spectroscopic survey that utilized strong-lensing magnification by intermediate-redshift clusters of galaxies. We observed carefully selected regions near nine clusters, consistent with magnification factors generally greater than 10 for the redshift range 4.5L)~L-1 over 1041-1042.5 ergs s-1. When combined with the results of other surveys, limited at higher luminosities, our results suggest evidence for the suppression of star formation in low-mass halos, as predicted in popular models of galaxy formation. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Recalculating the quasar luminosity function of the extended Baryon Oscillation Spectroscopic Survey

NASA Astrophysics Data System (ADS)

Caditz, David M.

2017-12-01

Aims: The extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey provides a uniform sample of over 13 000 variability selected quasi-stellar objects (QSOs) in the redshift range 0.68

The mysterious age invariance of the planetary nebula luminosity function bright cut-off

NASA Astrophysics Data System (ADS)

Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M.

2018-05-01

Planetary nebulae mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models1,2 predicted that only stars above approximately twice the solar mass could form a bright nebula. But the ubiquitous presence of bright planetary nebulae in old stellar populations, such as elliptical galaxies, contradicts this: such high-mass stars are not present in old systems. The planetary nebula luminosity function, and especially its bright cut-off, is almost invariant between young spiral galaxies, with high-mass stars, and old elliptical galaxies, with only low-mass stars. Here, we show that new evolutionary tracks of low-mass stars are capable of explaining in a simple manner this decades-old mystery. The agreement between the observed luminosity function and computed stellar evolution validates the latest theoretical modelling. With these models, the planetary nebula luminosity function provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a planetary nebula, but it will be faint.

The fraction of AGNs in major merger galaxies and its luminosity dependence

NASA Astrophysics Data System (ADS)

Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Trakhtenbrot, Benny; Sanders, David B.

2018-05-01

We use a phenomenological model which connects the galaxy and active galactic nucleus (AGN) populations to investigate the process of AGNs triggering through major galaxy mergers at z ˜ 0. The model uses stellar mass functions as input and allows the prediction of AGN luminosity functions based on assumed Eddington ratio distribution functions (ERDFs). We show that the number of AGNs hosted by merger galaxies relative to the total number of AGNs increases as a function of AGN luminosity. This is due to more massive galaxies being more likely to undergo a merger and does not require the assumption that mergers lead to higher Eddington ratios than secular processes. Our qualitative analysis also shows that to match the observations, the probability of a merger galaxy hosting an AGN and accreting at a given Eddington value has to be increased by a factor ˜10 relative to the general AGN population. An additional significant increase of the fraction of high Eddington ratio AGNs among merger host galaxies leads to inconsistency with the observed X-ray luminosity function. Physically our results imply that, compared to the general galaxy population, the AGN fraction among merger galaxies is ˜10 times higher. On average, merger triggering does however not lead to significantly higher Eddington ratios.

X-ray Reverberation Mapping in Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Kara, Erin

2018-01-01

Active Galactic Nuclei can produce as much or more electromagnetic and kinetic luminosities than the combined stellar luminosity of an entire galaxy. The energy output from AGN comes from the gravitational potential energy of the infalling material and the rotational energy of the black hole, both of which are released very close to the black hole. Therefore, probing the relativistic region of the inner accretion flow is essential to understanding how AGN work and effect their environments. In this talk, I will present a new technique for probing these relativistic environments: X-ray reverberation mapping. Similar to Optical reverberation mapping, where time delays of days or weeks between the continuum and Broad Line Region lines map out centiparsec scales, X-ray reverberation reveals time delays of tens of seconds, which map out microparsec scales in the accretion flow—well beyond the spatial resolution power of any instrument. This technique has been discovered in the past decade, so I will give a brief overview of how the measurements are made, and highlight some recent discoveries, which allow us to map the gas falling on to the black hole and measure the effects of strongly curved spacetime close to the event horizon.

HOT-DUST-POOR TYPE 1 ACTIVE GALACTIC NUCLEI IN THE COSMOS SURVEY

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

Hao Heng; Elvis, Martin; Civano, Francesca

2010-11-20

We report a sizable class of type 1 active galactic nuclei (AGNs) with unusually weak near-infrared (1-3 {mu}m) emission in the XMM-COSMOS type 1 AGN sample. The fraction of these 'hot-dust-poor' AGNs increases with redshift from 6% at low redshift (z < 2) to 20% at moderate high redshift (2 < z < 3.5). There is no clear trend of the fraction with other parameters: bolometric luminosity, Eddington ratio, black hole mass, and X-ray luminosity. The 3 {mu}m emission relative to the 1 {mu}m emission is a factor of 2-4 smaller than the typical Elvis et al. AGN spectral energymore » distribution (SED), which indicates a 'torus' covering factor of 2%-29%, a factor of 3-40 smaller than required by unified models. The weak hot dust emission seems to expose an extension of the accretion disk continuum in some of the source SEDs. We estimate the outer edge of their accretion disks to lie at (0.3-2.0) x 10{sup 4} Schwarzschild radii, {approx}10-23 times the gravitational stability radii. Formation scenarios for these sources are discussed.« less

A redshift survey of IRAS galaxies

NASA Astrophysics Data System (ADS)

Smith, Beverly J.; Kleinmann, S. G.; Huchra, J. P.; Low, F. J.

1987-05-01

Results are presented from a redshift survey of all 72 galaxies detected by IRAS in Band 3 at flux levels equal to or greater then 2 Jy. The luminosity function at the high luminosity end is proportional to L-2, however, a flattening was observed at the low luminosity end indicating that a single power law is not a good description of the entire luminosity function. Only three galaxies in the sample have emission line spectra indicative of AGN's, suggesting that, at least in nearby galaxies, unobscured nuclear activity is not a strong contributor to the far infrared flux. Comparisons between the selected IRAS galaxies and an optically complete sample taken from the CfA redshift survey show that they are more narrowly distributed than those optically selected, in the sence that the IRAS sample includes few galaxies of low absolute blue luminosity. It was also found that the space distributions of the two samples differ: the density enhancement or IRAS galaxies is only approx. 1/3 that of the optically selected galaxies in the core of the Coma cluster.

The massive end of the luminosity and stellar mass functions and clustering from CMASS to SDSS: evidence for and against passive evolution

NASA Astrophysics Data System (ADS)

Bernardi, M.; Meert, A.; Sheth, R. K.; Huertas-Company, M.; Maraston, C.; Shankar, F.; Vikram, V.

2016-02-01

We describe the luminosity function, based on Sérsic fits to the light profiles, of CMASS galaxies at z ˜ 0.55. Compared to previous estimates, our Sérsic-based reductions imply more luminous, massive galaxies, consistent with the effects of Sérsic- rather than Petrosian or de Vaucouleur-based photometry on the Sloan Digital Sky Survey (SDSS) main galaxy sample at z ˜ 0.1. This implies a significant revision of the high-mass end of the correlation between stellar and halo mass. Inferences about the evolution of the luminosity and stellar mass functions depend strongly on the assumed, and uncertain, k + e corrections. In turn, these depend on the assumed age of the population. Applying k + e corrections taken from fitting the models of Maraston et al. to the colours of both SDSS and CMASS galaxies, the evolution of the luminosity and stellar mass functions appears impressively passive, provided that the fits are required to return old ages. However, when matched in comoving number- or luminosity-density, the SDSS galaxies are less strongly clustered compared to their counterparts in CMASS. This rules out the passive evolution scenario, and, indeed, any minor merger scenarios which preserve the rank ordering in stellar mass of the population. Potential incompletenesses in the CMASS sample would further enhance this mismatch. Our analysis highlights the virtue of combining clustering measurements with number counts.

An expanded set of brown dwarf and very low mass star models

NASA Technical Reports Server (NTRS)

Burrows, A.; Hubbard, W. B.; Saumon, D.; Lunine, J. I.

1993-01-01

We present in this paper updated and improved theoretical models of brown dwarfs and late M dwarfs. The evolution and characteristics of objects between 0.01 and 0.2 solar mass are exhaustively investigated and special emphasis is placed on their properties at early ages. The dependence on the helium fraction, deuterium fraction, and metallicity of the masses, effective temperature and luminosities at the edge of the hydrogen main sequence are calculated. We derive luminosity functions for representative mass functions and compare our predictions to recent cluster data. We show that there are distinctive features in the theoretical luminosity functions that can serve as diagnostics of brown dwarf physics. A zero-metallicity model is presented as a bound to or approximation of a putative extreme halo population.

A Correlation Between Changes in Solar Luminosity and Differential Radius Measurements

NASA Technical Reports Server (NTRS)

Kroll, R. J.; Hill, H. A.; Beardsley, B. J.

1990-01-01

Solar luminosity variations occurring during solar cycle 21 can be attributed in large part to the presence of sunspots and faculae. Nevertheless, there remains a residual portion of the luminosity variation distinctly unaccounted for by these phenomena of solar activity. At the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA), observations of the solar limb are capable of detecting changes in the solar limb darkening function by monitoring a quantity known as the differential radius. These observations are utilized in such a way that the effects of solar activity are minimized in order to reveal the more fundamental structure of the photosphere. The results of observations made during solar cycle 21 at various solar latitudes indicate that a measurable change did occur in the global photospheric limb darkening function. It is proposed that the residual luminosity change is associated in part with this change in limb darkening.

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

NASA Astrophysics Data System (ADS)

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

2016-08-01

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

Quasar evolution and the growth of black holes

NASA Technical Reports Server (NTRS)

Small, Todd A.; Blandford, Roger D.

1992-01-01

A 'minimalist' model of AGN evolution is analyzed that links the measured luminosity function to an elementary description of black hole accretion. The observed luminosity function of bright AGN is extrapolated and simple prescriptions for the growth and luminosity of black holes are introduced to infer quasar birth rates, mean fueling rates, and relict black hole distribution functions. It is deduced that the mean accretion rate scales as (M exp -1./5)(t exp -6.7) and that, for the most conservative model used, the number of relict black holes per decade declines only as M exp -0.4 for black hole masses between 3 x 10 exp 7 and 3 x 10 exp 9 solar masses. If all sufficiently massive galaxies pass through a quasar phase with asymptotic black hole mass a monotonic function of the galaxy mass, then it is possible to compare the space density of galaxies with estimated central masses to that of distant quasars.

Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age

NASA Technical Reports Server (NTRS)

Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Bookbinder, J.; Golub, L.; Harnden, F. R., Jr.; Rosner, R.

1985-01-01

The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter than the corresponding function for Hyades G dwarf stars. This finding indicates a dependence of X-ray luminosity on stellar age, which is confirmed by comparison of the same data with median X-ray luminosities of pre-main sequence and local disk population dwarf G stars. It is suggested that the significantly larger number of bright X-ray sources associated with G stars than with K stars, the lack of detection of M stars, and the relatively rapid rotation of the Pleiades K stars can be explained in terms of the onset of internal differential rotation near the convective envelope-radidative core interface after the spin-up phase during evolution to the main sequence.

Einstein Observatory survey of X-ray emission from solar-type stars - The late F and G dwarf stars

NASA Technical Reports Server (NTRS)

Maggio, A.; Sciortino, S.; Vaiana, G. S.; Majer, P.; Bookbinder, J.

1987-01-01

Results of a volume-limited X-ray survey of stars of luminosity classes IV and V in the spectral range F7-G9 observed with the Einstein Observatory are presented. Using survival analysis techniques, the stellar X-ray luminosity function in the 0.15-4.0 keV energy band for both single and multiple sources. It is shown that the difference in X-ray luminosity between these two classes of sources is consistent with the superposition of individual components in multiple-component systems, whose X-ray properties are similar to those of the single-component sources. The X-ray emission of the stars in our sample is well correlated with their chromospheric CA II H-K line emission and with their projected equatorial rotational velocity. Comparison of the X-ray luminosity function constructed for the sample of the dG stars of the local population with the corresponding functions derived elsewhere for the Hyades, the Pleiades, and the Orion Ic open cluster confirms that the level of X-ray emission decreases with stellar age.

Continuum limit of electrostatic gyrokinetic absolute equilibrium

NASA Astrophysics Data System (ADS)

Zhu, Jian-Zhou

2012-06-01

Electrostatic gyrokinetic absolute equilibria with continuum velocity field are obtained through the partition function and through the Green function of the functional integral. The new results justify and explain the prescription for quantization/discretization or taking the continuum limit of velocity. The mistakes in the Appendix D of our earlier work [J.-Z. Zhu and G. W. Hammett, Phys. Plasmas 17, 122307 (2010)] are explained and corrected. If the lattice spacing for discretizing velocity is big enough, all the invariants could concentrate at the lowest Fourier modes in a negative-temperature state, which might indicate a possible variation of the dual cascade picture in 2D plasma turbulence.

Supermassive Black Holes in Late-type Spiral Galaxies: Constraining High Mass X-ray Binary Contamination

NASA Astrophysics Data System (ADS)

Dittenber, Benjamin; Hodges-Kluck, Edmund J.; Gallo, Elena

2018-06-01

Supermassive black holes (SMBHs) are known to commonly reside in the centers of large galaxies, but it is unclear whether they reside in smaller galaxies (M_* < M_sun x 10^10). X-rays are the most efficient way to detect low-level accretion, and provide the best measurement of the occupation fraction. X-ray binaries can be nearly as bright as SMBHs that have sub-Eddington accretion rates. High-mass XRBs (HMXBs) are especially problematic because they can get brighter than low-mass XRBs. However, previous estimates of HMXB contamination (based on the optical continuum to get the fraction of HMXBs expected in the nucleus) may be too high. A better approach is to use FUV or H-alpha, which directly trace ongoing star formation. We did this in a sample of 30 late-type galaxies with Chandra data. We calculate the total Expected X-ray Luminosity from XRBs (L_x) for each sample galaxy using existing relationships between X-ray luminosity and SFR. We estimate the fraction of the stellar formation in the nucleus by measuring the fraction of nuclear UV or H-alpha light there (total SFR is from the far infrared). Our Galex data is scaled with a sample of 6 Swift UVOT galaxies to measure with the same aperture size that previous works have used in the B-band. We found that the mean L_x,c for Swift scaled FUV ratios is ~2.025 x 10^36 and the mean L_x,c for H-alpha ratios is 7.693 x 10^35. These luminosities are 1.9 and 5 times smaller than B-band measured luminosities respectively. These results suggest that HMXBs do not contribute as much contamination in these galaxies as previously thought. Therefore, with a lower contamination, estimates of the occupation fraction from late-type galaxies are more reliable.

Evidence for Black Hole Growth in Local Analogs to Lyman Break Galaxies

NASA Technical Reports Server (NTRS)

Jia, Jianjun; Ptak, Andrew; Heckman, Timothy M.; Overzier, Roderik A.; Hornschemeier, Ann; LaMassa, Stephanie M.

2011-01-01

We have used XMM-Newton to observe six Lyman break analogs (LBAs): members of the rare population of local galaxies that have properties that are very similar to distant Lyman break galaxies. Our six targets were specifically selected because they have optical emission-line properties that are intermediate between starbursts and Type 2 (obscured) active galactic nuclei (AGNs). Our new X-ray data provide an important diagnostic of the presence of an AGN. We find X-ray luminosities of order 10(sup 42) erg per second and ratios of X-ray to far-IR lummositles that are higher than values in pure starburst galaxies by factors ranging from approximately 3 to 30. This strongly suggests the presence of an AGN in at least some of the galaxies. The ratios of the luminosities of the hard (2-10 keV) X-ray to [O III] emission line are low by about an order of magnitude compared with Type 1 AGN, but are consistent with the broad range seen in Type 2 AGN. Either the AGN hard X-rays are significantly obscured or the [O III] emission is dominated by the starburst. We searched for an iron emission line at approximately 6.4 ke V, which is a key feature of obscured AGNs, but only detected emission at the approximately 2sigma level. Finally, we find that the ratios of the mid-infrared (24 micrometer) continuum to [O III]lambda 5007 luminosities in these LBAs are higher than the values for Type 2 AGN by an average of 0.8 dex. Combining all these clues, we conclude that an AGN is likely to be present, but that the bolometric luminosity is produced primarily by an intense starburst. If these black holes are radiating at the Eddington limit, their masses would lie in the range of 10(sup 5) - 10(sup 6) solar mass. These objects may offer ideal local laboratories to investigate the processes by which black holes grew in the early universe.

Quiescent Giant Molecular Cloud Cores in the Galactic Center

NASA Technical Reports Server (NTRS)

Lis, D. C.; Serabyn, E.; Zylka, R.; Li, Y.

2000-01-01

We have used the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO) to map the far-infrared continuum emission (45-175 micrometer) toward several massive Giant Molecular Cloud (GMC) cores located near the Galactic center. The observed far-infrared and submillimeter spectral energy distributions imply low temperatures (approx. 15 - 22 K) for the bulk of the dust in all the sources, consistent with external heating by the diffuse ISRF and suggest that these GMCs do not harbor high- mass star-formation sites, in spite of their large molecular mass. Observations of FIR atomic fine structure lines of C(sub II) and O(sub I) indicate an ISRF enhancement of approx. 10(exp 3) in the region. Through continuum radiative transfer modeling we show that this radiation field strength is in agreement with the observed FIR and submillimeter spectral energy distributions, assuming primarily external heating of the dust with only limited internal luminosity (approx. 2 x 10(exp 5) solar luminosity). Spectroscopic observations of millimeter-wave transitions of H2CO, CS, and C-34S carried out with the Caltech Submillimeter Observatory (CSO) and the Institut de Radio Astronomie Millimetrique (IRAM) 30-meter telescope indicate a gas temperature of approx. 80 K, significantly higher than the dust temperatures, and density of approx. 1 x 10(exp 5)/cc in GCM0.25 + 0.01, the brightest submillimeter source in the region. We suggest that shocks caused by cloud collisions in the turbulent interstellar medium in the Galactic center region are responsible for heating the molecular gas. This conclusion is supported by the presence of wide-spread emission from molecules such as SiO, SO, and CH3OH, which are considered good shock tracers. We also suggest that the GMCs studied here are representative of the "typical", pre-starforming cloud population in the Galactic center.

WPVS 007: Dramatic Broad Absorption Line Variability in a Narrow-line Seyfert 1

NASA Astrophysics Data System (ADS)

Cooper, Erin M.; Leighly, K.; Hamann, F. W.; Grupe, D.; Dietrich, M.

2014-01-01

Blue-shifted broad absorption lines are the manifestation of gaseous outflows in astrophysical phenomena. In active galaxies, these outflowing winds may play a key role in the central engine physics by removing angular momentum and in influencing host galaxy evolution by imparting energy and chemically enriched gas to the surrounding medium. AGN wind variability affords us a valuable tool to study this still poorly understood phenomenon. The existence of a high velocity broad line outflow in WPVS007 is especially extraordinary, as Seyfert-luminosity active galaxies are unexpected to produce them. With its lower luminosity and compact size, the NLS1 galaxy WPVS007 (M_V=-19.7, z=0.02882) provides us the ability to study even colossal variability on merely human timescales. Since its 1996 FOS observation, displaying miniBALs but no true broad absorption lines, WPVS007 has experienced a short but rich history of UV BAL variability. By the 2003 FUSE observation, WPVS007 had developed a BAL with v_max ~ 6000km/s, indicating an optically thick, high velocity outflow. We present the 2010 and 2013 June and December HST COS spectra. Between 2003 and 2010, both the maximum and minimum outflow velocity had increased substantially. As of 2013 June, the continuum emission has since dimmed by a factor of ~2 and the BALs have appeared to weaken, with both decreased maximum and minimum velocities. Such dramatic shifts in BAL velocity are unprecedented, as BAL variability is typically confined to changes in optical depth. What is the nature of the variability in this BAL wind? The upcoming (as of the writing of this abstract) December observation should give us more insight into tackling that question, whether it be the transient response of a continuous flow to a fluctuating continuum or perhaps the continued decline of a discrete outflow event.

ANALYSIS OF OPTICAL Fe II EMISSION IN A SAMPLE OF ACTIVE GALACTIC NUCLEUS SPECTRA

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

Kovacevic, Jelena; Popovic, Luka C.; Dimitrijevic, Milan S., E-mail: jkovacevic@aob.bg.ac.r

We present a study of optical Fe II emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest Fe II multiplets into three groups according to the lower term of the transition (b{sup 4} F, a{sup 6} S, and a{sup 4} G terms). These approximately correspond to the blue, central, and red parts, respectively, of the 'iron shelf' around H{beta}. We calculate an Fe II template that takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1.more » This Fe II template gives a more precise fit of the Fe II lines in broad-line AGNs than other templates. We extract Fe II, H{alpha}, H{beta}, [O III], and [N II] emission parameters and investigate correlations between them. We find that Fe II lines probably originate in an intermediate line region. We note that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM H{beta}, the velocity shift of Fe II, and the H{alpha}/H{beta} flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of Fe II and [O III] on continuum luminosity. We find that there is a Baldwin effect for [O III] but an inverse Baldwin effect for the Fe II emission. The [O III]/Fe II ratio thus decreases with L {sub {lambda}5100}. Since the ratio is a major component of the Boroson and Green Eigenvector 1 (EV1), this implies a connection between the Baldwin effect and EV1 and could be connected with AGN evolution. We find that spectra are different for H{beta} FWHMs greater and less than {approx}3000 km s{sup -1}, and that there are different correlation coefficients between the parameters.« less

A 33 GHz Survey of Local Major Mergers: Estimating the Sizes of the Energetically Dominant Regions from High-resolution Measurements of the Radio Continuum

NASA Astrophysics Data System (ADS)

Barcos-Muñoz, L.; Leroy, A. K.; Evans, A. S.; Condon, J.; Privon, G. C.; Thompson, T. A.; Armus, L.; Díaz-Santos, T.; Mazzarella, J. M.; Meier, D. S.; Momjian, E.; Murphy, E. J.; Ott, J.; Sanders, D. B.; Schinnerer, E.; Stierwalt, S.; Surace, J. A.; Walter, F.

2017-07-01

We present Very Large Array observations of the 33 GHz radio continuum emission from 22 local ultraluminous and luminous infrared (IR) galaxies (U/LIRGs). These observations have spatial (angular) resolutions of 30-720 pc (0.″07-0.″67) in a part of the spectrum that is likely to be optically thin. This allows us to estimate the size of the energetically dominant regions. We find half-light radii from 30 pc to 1.7 kpc. The 33 GHz flux density correlates well with the IR emission, and we take these sizes as indicative of the size of the region that produces most of the energy. Combining our 33 GHz sizes with unresolved measurements, we estimate the IR luminosity and star formation rate per area and the molecular gas surface and volume densities. These quantities span a wide range (4 dex) and include some of the highest values measured for any galaxy (e.g., {{{Σ }}}{SFR}33 {GHz}≤slant {10}4.1 {M}⊙ {{yr}}-1 {{kpc}}-2). At least 13 sources appear Compton thick ({N}{{H}}33 {GHz}≥slant {10}24 {{cm}}-2). Consistent with previous work, contrasting these data with observations of normal disk galaxies suggests a nonlinear and likely multivalued relation between star formation rate and molecular gas surface density, though this result depends on the adopted CO-to-H2 conversion factor and the assumption that our 33 GHz sizes apply to the gas. Eleven sources appear to exceed the luminosity surface density predicted for starbursts supported by radiation pressure and supernova feedback; however, we note the need for more detailed observations of the inner disk structure. U/LIRGs with higher surface brightness exhibit stronger [C II] 158 μm deficits, consistent with the suggestion that high energy densities drive this phenomenon.

Discovery of Diffuse Hard X-ray Emission associated with Jupiter

NASA Astrophysics Data System (ADS)

Ezoe, Y.; Miyoshi, Y.; Ishikawa, K.; Ohashi, T.; Terada, N.; Uchiyama, Y.; Negoro, H.

2009-12-01

Our discovery of diffuse hard (1-5 keV) X-ray emission around Jupiter is reported. Recent Chandra and XMM-Newton observations revealed several types of X-rays in the vicinity of Jupiter such as auroral and disk emission from Jupiter and faint diffuse X-rays from the Io Plasma Torus (see Bhardwaj et al. 2007 for review). To investigate possible diffuse hard X-ray emission around Jupiter with the highest sensitivity, we conducted data analysis of Suzaku XIS observations of Jupiter on Feb 2006. After removing satellite and planetary orbital motions, we detected a significant diffuse X-ray emission extending to ~6 x 3 arcmin with the 1-5 keV X-ray luminosity of ~3e15 erg/s. The emitting region very well coincided with the Jupiter's radiation belts. The 1-5 keV X-ray spectrum was represented by a simple power law model with a photon index of 1.4. Such a flat continuum strongly suggests non-thermal origin. Although such an emission can be originated from multiple background point sources, its possibility is quite low. We hence examined three mechanisms, assuming that the emission is truly diffuse: bremsstrahlung by keV electrons, synchrotron emission by TeV electrons, and inverse Compton scattering of solar photons by MeV electrons. The former two can be rejected because of the X-ray spectral shape and implausible existence of TeV electrons around Jupiter, respectively. The last possibility was found to be possible because tens MeV electrons, which have been confirmed in inner radiation belts (Bolton et al. 2002), can kick solar photons to the keV energy range and provide a simple power-law continuum. We estimated an average electron density from the X-ray luminosity assuming the oblate spheroid shaped emitting region with 8 x 8 x 4 Jovian radii. The necessary density was 0.02 1/cm3 for 50 MeV electrons. Hence, our results may suggest a new particle acceleration phenomenon around Jupiter.

Dust Properties of Local Dust-obscured Galaxies with the Submillimeter Array

NASA Astrophysics Data System (ADS)

Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J.

2013-11-01

We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S ν(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S ν(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 1011(L ⊙) and 4-14 × 107(M ⊙), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.

The ISO View of Star Forming Galaxies

NASA Astrophysics Data System (ADS)

Helou, George

1999-01-01

ISO studies of normal galaxies in the local Universe have revealed basic new properties whose significant implications for the star formation process and cosmology are only starting to be understood. This review will touch on the general results of a statistical nature, and provide a quick summary of the profusion of exciting results on individual objects. In the mid-infrared, PHT-S has established that the spectra of star forming galaxies between 6 and-13microns are dominated by the Aromatic Features in Emission (AFE), and show little variation as a function of the heating intensity. The Carriers of the AFE (CAFE) are thus a universal component of dust with standard properties, and contribute between 10 and 25% of the total dust luminosity. In addition to AFE, the spectra show a low-level continuum detectable at wavelengths longer than 3.5microns whose origin is still under investigation. The mid-infrared colors formed as the ratio of flux densities in the 6.75micron and the 15micron bands of ISO-CAM remain essentially constant and near unity for quiescent and mildly active galaxies. As dust heating increases further, the 15micron flux increases steeply compared to 6.75microns, indicating that dust heated to 100K

Evolution of Galaxy Luminosity and Stellar-Mass Functions since $z=1$ with the Dark Energy Survey Science Verification Data

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

Capozzi, D.; et al.

We present the first study of the evolution of the galaxy luminosity and stellar-mass functions (GLF and GSMF) carried out by the Dark Energy Survey (DES). We describe the COMMODORE galaxy catalogue selected from Science Verification images. This catalogue is made ofmore » $$\\sim 4\\times 10^{6}$$ galaxies at $$0« less

Multi-wavelength study of NGC 281 A

NASA Technical Reports Server (NTRS)

Henning, TH.; Martin, K.; Reimann, H.-G.; Launhardt, R.; Leisawitz, D.; Zinnecker, H.

1994-01-01

We present a study of the molecular cloud NGC 281 A and the associated compact and young star cluster NGC 281 (AS 179). Optical photometry leads to a new distance of 3500 pc for the star cluster which is in good agreement with the kinematical distance of the adjacent molecular cloud NGC 281 A. The exciting star HD 5005 of the optical nebulosity is a Trapezium system with O6 III as photometric spectral type for the component HD 5005 AB. For the age of the star cluster we estimated a value of about 3 x 10(exp 6) yr. The (12)CO (2 to 1), (13)CO (2 to 1), and (12)CO (3 to 2) emission shows that the molecular cloud NGC 281 A consists of two cloud fragments. The western fragment is more compact and massive than the eastern fragment and contains an NH3 core. This core is associated with the IRAS source 00494+5617, an H2O maser, and 1.3 millimeter dust continuum radiation. Both cloud fragments contain altogether 22 IRAS point sources which mostly share the properties of young stellar objects. They have luminosities between 150 and 8800 solar luminosity. The maxima of the 60 and 100 micrometers HIRES maps correspond to the maxima of the (12)CO (3 to 2) emission. The NGC 281 A region shares many properties with the Orion Trapezium-BN/KL region the main differences being a larger separation between the cluster centroid and the new site of star formation as well as a lower mass and luminosity of the molecular cloud and the infrared cluster.

A survey of the cold molecular gas in gravitationally lensed star-forming galaxies at z > 2

NASA Astrophysics Data System (ADS)

Aravena, M.; Spilker, J. S.; Bethermin, M.; Bothwell, M.; Chapman, S. C.; de Breuck, C.; Furstenau, R. M.; Gónzalez-López, J.; Greve, T. R.; Litke, K.; Ma, J.; Malkan, M.; Marrone, D. P.; Murphy, E. J.; Stark, A.; Strandet, M.; Vieira, J. D.; Weiss, A.; Welikala, N.; Wong, G. F.; Collier, J. D.

2016-04-01

Using the Australia Telescope Compact Array, we conducted a survey of CO J = 1 - 0 and J = 2 - 1 line emission towards strongly lensed high-redshift dusty star-forming galaxies (DSFGs) previously discovered with the South Pole Telescope (SPT). Our sample comprises 17 sources that had CO-based spectroscopic redshifts obtained with the Atacama Large Millimeter/submillimeter Array and the Atacama Pathfinder Experiment. We detect all sources with known redshifts in either CO J = 1 - 0 or J = 2 - 1. 12 sources are detected in the 7-mm continuum. The derived CO luminosities imply gas masses in the range (0.5-11) × 1010 M⊙ and gas depletion time-scales tdep < 200 Myr, using a CO to gas mass conversion factor αCO = 0.8 M⊙ (K km s-1 pc2)-1. Combining the CO luminosities and dust masses, along with a fixed gas-to-dust ratio, we derive αCO factors in the range 0.4-1.8 M⊙ (K km s-1 pc2)-1, similar to what is found in other starbursting systems. We find small scatter in αCO values within the sample, even though inherent variations in the spatial distribution of dust and gas in individual cases could bias the dust-based αCO estimates. We find that lensing magnification factors based on the CO linewidth to luminosity relation (μCO) are highly unreliable, but particularly when μ < 5. Finally, comparison of the gas and dynamical masses suggest that the average molecular gas fraction stays relatively constant at z = 2-5 in the SPT DSFG sample.

Detection of the 158 Micrometers[CII] Transition at z=1.3: Evidence for a Galaxy-Wide Starburst

NASA Technical Reports Server (NTRS)

Hailey-Dunsheath, S.; Nikola, T.; Stacey, G. J.; Oberst, T. E.; Parshley, S. C.; Benford, D. J.; Staguhn, J. G.; Tucker, C. E.

2010-01-01

We report the detection of 158 micrometer [C II] fine-structure line emission from MIPS J 142824.0+3526l9, a hyperluminous (L(sub IR) approx. 10(exp 13) Solar Luminosity starburst galaxy at z = 1.3. The line is bright, corresponding to a fraction L[C II]/L(sub FIR) approx. equals 2 x l0(exp -3) of the far-IR(FIR) continuum. The [C II], CO, and FIR continuum emission may be modeled as arising from photodissociation regions (PDRs) that have a characteristic gas density of n approx. 10(exp 4.2)/cu cm., and that are illuminated by a far-UV radiation field approx. 10(exp 3.2) times more intense than the local interstellar radiation field. The mass in these PDRs accounts for approximately half of the molecular gas mass in this galaxy. The L[C II]/L(sub F1R) ratio is higher than observed in local ultraluminous infrared galaxies or in the few high-redshift QSOs detected in [C II], but the L[CII]/L(sub FIR) and L(sub CO)/L(sub FIR) ratios are similar to the values seen in nearby starburst galaxies

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

NASA Astrophysics Data System (ADS)

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

2018-02-01

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

Functional and physical abilities in the early continuum of cognitive decline.

PubMed

Shin, Joon-Ho; Lim, Jae-Young; Kim, Ki Woong; Kim, Suyoung; Lee, Jaebong; Paik, Nam-Jong

2015-01-01

The early cognitive continuum has been emphasized recently. We sought to characterize the functional and physical aspects of the cognitive continuum in subjects with no cognitive impairment (NCI), subjective cognitive impairment (SCI), nonamnestic (NA-MCI), and amnestic mild cognitive impairment (A-MCI). Furthermore, we identified the potential diagnostic utility of specific functional tasks. A total of 702 participants, aged ≥65 years and defined as NCI, SCI, NA-MCI, and A-MCI according to the original Petersen criteria, were included. They completed the Korean basic (K-ADL) and Instrumental Activities of Daily Living Scales (K-IADL) and the Performance-Oriented Mobility Assessment (POMA). Significant differences were observed between the different cognitive status groups in three items and total scores on the K-ADL, six items and total scores on the K-IADL and POMA. Controlling for confounding factors revealed that subjects from the A-MCI group performed poorly at bathing, shopping, handling money, and the sum of assorted functional items. These findings demonstrated the declining feature of functional and physical performance according to the cognitive continuum, with A-MCI being discriminative with respect to specific functional tasks as compared to milder cognitive statuses. © 2014 S. Karger AG, Basel.

OBSERVATIONS OF Arp 220 USING HERSCHEL-SPIRE: AN UNPRECEDENTED VIEW OF THE MOLECULAR GAS IN AN EXTREME STAR FORMATION ENVIRONMENT

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

Rangwala, Naseem; Maloney, Philip R.; Glenn, Jason

2011-12-10

We present Herschel Spectral and Photometric Imaging Receiver Fourier Transform Spectrometer (Herschel SPIRE-FTS) observations of Arp 220, a nearby ultra-luminous infrared galaxy. The FTS provides continuous spectral coverage from 190 to 670 {mu}m, a wavelength region that is either very difficult to observe or completely inaccessible from the ground. The spectrum provides a good measurement of the continuum and detection of several molecular and atomic species. We detect luminous CO (J = 4-3 to 13-12) and water rotational transitions with comparable total luminosity {approx}2 Multiplication-Sign 10{sup 8} L{sub Sun }; very high-J transitions of HCN (J = 12-11 to 17-16)more » in absorption; strong absorption features of rare species such as OH{sup +}, H{sub 2}O{sup +}, and HF; and atomic lines of [C I] and [N II]. The modeling of the continuum shows that the dust is warm, with T = 66 K, and has an unusually large optical depth, with {tau}{sub dust} {approx} 5 at 100 {mu}m. The total far-infrared luminosity of Arp 220 is L{sub FIR} {approx} 2 Multiplication-Sign 10{sup 12} L{sub Sun }. Non-LTE modeling of the extinction corrected CO rotational transitions shows that the spectral line energy distribution of CO is fit well by two temperature components: cold molecular gas at T {approx} 50 K and warm molecular gas at T {approx} 1350{sup +280}{sub -100} K (the inferred temperatures are much lower if CO line fluxes are not corrected for dust extinction). These two components are not in pressure equilibrium. The mass of the warm gas is 10% of the cold gas, but it dominates the CO luminosity. The ratio of total CO luminosity to the total FIR luminosity is L{sub CO}/L{sub FIR} {approx} 10{sup -4} (the most luminous lines, such as J = 6-5, have L{sub CO,J=6-5}/L{sub FIR} {approx} 10{sup -5}). The temperature of the warm gas is in excellent agreement with the observations of H{sub 2} rotational lines. At 1350 K, H{sub 2} dominates the cooling ({approx}20 L{sub Sun} M{sup -1}{sub Sun }) in the interstellar medium compared to CO ({approx}0.4 L{sub Sun} M{sup -1}{sub Sun }). We have ruled out photodissociation regions, X-ray-dominated regions, and cosmic rays as likely sources of excitation of this warm molecular gas, and found that only a non-ionizing source can heat this gas; the mechanical energy from supernovae and stellar winds is able to satisfy the large energy budget of {approx}20 L{sub Sun} M{sup -1}{sub Sun }. Analysis of the very high-J lines of HCN strongly indicates that they are solely populated by infrared pumping of photons at 14 {mu}m. This mechanism requires an intense radiation field with T > 350 K. We detect a massive molecular outflow in Arp 220 from the analysis of strong P Cygni line profiles observed in OH{sup +}, H{sub 2}O{sup +}, and H{sub 2}O. The outflow has a mass {approx}> 10{sup 7} M{sub Sun} and is bound to the nuclei with velocity {approx}< 250 km s{sup -1}. The large column densities observed for these molecular ions strongly favor the existence of an X-ray luminous AGN (10{sup 44} erg s{sup -1}) in Arp 220.« less

Luminosity of serendipitous x-ray QSOs

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

Margon, B.; Chanan, G.A.; Downes, R.A.

1982-02-01

We have identified the optical counterparts of 47 serendipitously discovered Einstein Observatory X-ray sources with previously unreported quasi-stellar objects. The mean ratio of X-ray to optical luminosity of this sample agrees reasonably well with that derived from X-ray observations of previously known QSOs. However, despite the fact that our limiting magnitude V = 18.5 should permit detection of typical QSOs (i.e., M/sub c/ = -26) to z = 0.9, the mean redshift of our sample is only z = 0.42 Thus the mean luminosity of these objects, M/sub c/ = -24, differs significantly from that of previous QSO surveys withmore » similar optical thresholds. The existence of large numbers of these lower luminosity QSOs which are difficult to discover by previous selection techniques, provides observational confirmation of the steep luminosity function inferred indirectly from optical counts. However, possible explanations for the lack of higher luminosity QSOs in our sample prove even more interesting. If one accepts the global value of the X-ray to optical luminosity ratio proposed by Zamorani et al, and Ku, Helfand, and Lucy, then reconciliation of this ratio with our observations severely constrains the QSO space density and luminosity functions. Alternatively, the ''typical'' QSO-a radio quiet, high redshift (z>1), optically luminous but not superluminous (M/sub c/> or =-27) object-may not be a strong X-ray source. This inference is not in conflict with existing results from Einstein X-ray surveys of preselected QSOs, which also fail to detect such objects. The contribution of QSOs to the diffuse X-ray background radiation is therefore highly uncertain, but may be quite small. Current X-ray data probably do not place significant constraints on the optical number counts of faint QSOs.« less

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

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

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

LoCuSS: connecting the dominance and shape of brightest cluster galaxies with the assembly history of massive clusters

NASA Astrophysics Data System (ADS)

Smith, Graham P.; Khosroshahi, Habib G.; Dariush, A.; Sanderson, A. J. R.; Ponman, T. J.; Stott, J. P.; Haines, C. P.; Egami, E.; Stark, D. P.

2010-11-01

We study the luminosity gap, Δm12, between the first- and second-ranked galaxies in a sample of 59 massive (~1015Msolar) galaxy clusters, using data from the Hale Telescope, the Hubble Space Telescope, Chandra and Spitzer. We find that the Δm12 distribution, p(Δm12), is a declining function of Δm12 to which we fitted a straight line: p(Δm12) ~ -(0.13 +/- 0.02)Δm12. The fraction of clusters with `large' luminosity gaps is p(Δm12 >= 1) = 0.37 +/- 0.08, which represents a 3σ excess over that obtained from Monte Carlo simulations of a Schechter function that matches the mean cluster galaxy luminosity function. We also identify four clusters with `extreme' luminosity gaps, Δm12 >= 2, giving a fraction of . More generally, large luminosity gap clusters are relatively homogeneous, with elliptical/discy brightest cluster galaxies (BCGs), cuspy gas density profiles (i.e. strong cool cores), high concentrations and low substructure fractions. In contrast, small luminosity gap clusters are heterogeneous, spanning the full range of boxy/elliptical/discy BCG morphologies, the full range of cool core strengths and dark matter concentrations, and have large substructure fractions. Taken together, these results imply that the amplitude of the luminosity gap is a function of both the formation epoch and the recent infall history of the cluster. `BCG dominance' is therefore a phase that a cluster may evolve through and is not an evolutionary `cul-de-sac'. We also compare our results with semi-analytic model predictions based on the Millennium Simulation. None of the models is able to reproduce all of the observational results on Δm12, underlining the inability of the current generation of models to match the empirical properties of BCGs. We identify the strength of active galactic nucleus feedback and the efficiency with which cluster galaxies are replenished after they merge with the BCG in each model as possible causes of these discrepancies.

Fundamental properties of Fanaroff-Riley type II radio galaxies investigated via Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Kapińska, A. D.; Uttley, P.; Kaiser, C. R.

2012-08-01

Radio galaxies and quasars are among the largest and most powerful single objects known and are believed to have had a significant impact on the evolving Universe and its large-scale structure. We explore the intrinsic and extrinsic properties of the population of Fanaroff-Riley type II (FR II) objects, i.e. their kinetic luminosities, lifetimes and the central densities of their environments. In particular, the radio and kinetic luminosity functions of these powerful radio sources are investigated using the complete, flux-limited radio catalogues of the Third Cambridge Revised Revised Catalogue (3CRR) and Best et al. We construct multidimensional Monte Carlo simulations using semi-analytical models of FR II source time evolution to create artificial samples of radio galaxies. Unlike previous studies, we compare radio luminosity functions found with both the observed and simulated data to explore the best-fitting fundamental source parameters. The new Monte Carlo method we present here allows us to (i) set better limits on the predicted fundamental parameters of which confidence intervals estimated over broad ranges are presented and (ii) generate the most plausible underlying parent populations of these radio sources. Moreover, as has not been done before, we allow the source physical properties (kinetic luminosities, lifetimes and central densities) to co-evolve with redshift, and we find that all the investigated parameters most likely undergo cosmological evolution. Strikingly, we find that the break in the kinetic luminosity function must undergo redshift evolution of at least (1 + z)3. The fundamental parameters are strongly degenerate, and independent constraints are necessary to draw more precise conclusions. We use the estimated kinetic luminosity functions to set constraints on the duty cycles of these powerful radio sources. A comparison of the duty cycles of powerful FR IIs with those determined from radiative luminosities of active galactic nuclei of comparable black hole mass suggests a transition in behaviour from high to low redshifts, corresponding to either a drop in the typical black hole mass of powerful FR IIs at low redshifts, or a transition to a kinetically dominated, radiatively inefficient FR II population.

Bias Properties of Extragalactic Distance Indicators. VIII. H0 from Distance-limited Luminosity Class and Morphological Type-Specific Luminosity Functions for SB, SBC, and SC Galaxies Calibrated Using Cepheids

NASA Astrophysics Data System (ADS)

Sandage, Allan

1999-12-01

Relative, reduced to absolute, magnitude distributions are obtained for Sb, Sbc, and Sc galaxies in the flux-limited Revised Shapley-Ames Catalog (RSA2) for each van den Bergh luminosity class (L), within each Hubble type (T). The method to isolate bias-free subsets of the total sample is via Spaenhauer diagrams, as in previous papers of this series. The distance-limited type and class-specific luminosity functions are normalized to numbers of galaxies per unit volume (105 Mpc3), rather than being left as relative functions, as in Paper V. The functions are calculated using kinematic absolute magnitudes, based on an arbitrary trial value of H0=50. Gaussian fits to the individual normalized functions are listed for each T and L subclass. As in Paper V, the data can be freed from the T and L dependencies by applying a correction of 0.23T+0.5L to the individual absolute magnitudes. Here, T=3 for Sb, 4 for Sbc, and 5 for Sc galaxies, and the L values range from 1 to 6 as the luminosity class changes from I to III-IV. The total luminosity function, obtained by combining the volume-normalized Sb, Sbc, and Sc individual luminosity functions, each corrected for the T and L dependencies, has an rms dispersion of 0.67 mag, similar to much of the Tully-Fisher parameter space. Absolute calibration of the trial kinematic absolute magnitudes is made using 27 galaxies with known T and L that also have Cepheid distances. This permits the systematic correction to the H0=50 kinematic absolute magnitudes of 0.22+/-0.12 mag, givingH0=55+/-3(internal) km s-1 Mpc-1 . The Cepheid distances are based on the Madore/Freedman Cepheid period-luminosity (PL) zero point that requires (m-M)0=18.50 for the LMC. Using the modern LMC modulus of (m-M)0=18.58 requires a 4% decrease in H0, giving a final value of H0=53+/-7 (external) by this method. These values of H0, based here on the method of luminosity functions, are in good agreement with (1) H0=55+/-5 by Theureau and coworkers from their bias-corrected Tully-Fisher method of ``normalized distances'' for field galaxies; (2) H0=56+/-4 from the method through the Virgo Cluster, as corrected to the global kinematic frame (Tammann and coworkers); and (3) H0=58+/-5 from Cepheid-calibrated Type Ia supernovae (Saha and coworkers). Our value here also disagrees with the final value from the NASA ``Key Project'' group value of H0=70+/-7. Analysis of the total flux-limited sample of Sb, Sbc, and Sc galaxies in the RSA2 by the present method, but uncorrected for selection bias, would give an incorrect value of H0=71 using the same Cepheid calibration. The effect of the bias is pernicious at the 30% level; either it must be corrected by the methods in the papers of this series, or the data must be restricted to the distance-limited subset of any sample, as is done here.

A cross-correlation-based estimate of the galaxy luminosity function

NASA Astrophysics Data System (ADS)

van Daalen, Marcel P.; White, Martin

2018-06-01

We extend existing methods for using cross-correlations to derive redshift distributions for photometric galaxies, without using photometric redshifts. The model presented in this paper simultaneously yields highly accurate and unbiased redshift distributions and, for the first time, redshift-dependent luminosity functions, using only clustering information and the apparent magnitudes of the galaxies as input. In contrast to many existing techniques for recovering unbiased redshift distributions, the output of our method is not degenerate with the galaxy bias b(z), which is achieved by modelling the shape of the luminosity bias. We successfully apply our method to a mock galaxy survey and discuss improvements to be made before applying our model to real data.

Age of Local Galactic Disk from the Wdlf for Cpmbs

NASA Astrophysics Data System (ADS)

Smith, J. Allyn; Oswalt, Terry D.; Wood, Matt A.; Silvestri, Nicole M.

We present the white dwarf luminosity function (WDLF) for common proper motion systems. This WDLF was derived using the 1/Vmax method pioneered by Schmidt (1975) and detailed by Liebert Dahn and Monet (1988). New cooling models were used to determine the luminosities of the white dwarfs and the age of the local Galactic disk. Comparison to WDLFs developed using older colling models (Wood 1995) will be examined for changes in the derived disk age. Kinematic data is available for a subset of the WDs in the sample. Separate luminosity functions will be examined for each of the statistically significant subsets. JAS acknowledges support from NASA GSRP Fellowship NGT-51086.

IRAS observations of the Rho Ophiuchi infrared cluster - Spectral energy distributions and luminosity function

NASA Technical Reports Server (NTRS)

Wilking, Bruce A.; Lada, Charles J.; Young, Eric T.

1989-01-01

High-sensitivity IRAS coadded survey data, coupled with new high-sensitivity near-IR observations, are used to investigate the nature of embedded objects over an 4.3-sq-pc area comprising the central star-forming cloud of the Ophiuchi molecular complex; the area encompasses the central cloud of the Rho Ophiuchi complex and includes the core region. Seventy-eight members of the embedded cluster were identified; spectral energy distributions were constructed for 53 objects and were compared with theoretical models to gain insight into their evolutionary status. Bolometric luminosities could be estimated for nearly all of the association members, leading to a revised luminosity function for this dust-embedded cluster.

M Dwarfs from Hubble Space Telescope Star Counts. IV.

NASA Astrophysics Data System (ADS)

Zheng, Zheng; Flynn, Chris; Gould, Andrew; Bahcall, John N.; Salim, Samir

2001-07-01

We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2 fields are newly analyzed. The method of maximum likelihood is applied to derive the luminosity function and the Galactic disk parameters. At first, we use a local color-magnitude relation and a locally determined mass-luminosity relation in our analysis. The results are consistent with those of previous work but with considerably reduced statistical errors. These small statistical errors motivate us to investigate the systematic uncertainties. Considering the metallicity gradient above the Galactic plane, we introduce a modified color-magnitude relation that is a function of Galactic height. The resultant M dwarf luminosity function has a shape similar to that derived using the local color-magnitude relation but with a higher peak value. The peak occurs at MV~12, and the luminosity function drops sharply toward MV~14. We then apply a height-dependent mass-luminosity function interpolated from theoretical models with different metallicities to calculate the mass function. Unlike the mass function obtained using local relations, which has a power-law index α=0.47, the one derived from the height-dependent relations tends to be flat (α=-0.10). The resultant local surface density of disk M dwarfs (12.2+/-1.6 Msolar pc-2) is somewhat smaller than the one obtained using local relations (14.3+/-1.3 Msolar pc-2). Our measurement favors a short disk scale length, H=2.75+/-0.16 (statistical)+/-0.25 (systematic) kpc. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

The UV Luminosity Function at 6 < z < 10 from the Hubble Frontier Fields

NASA Astrophysics Data System (ADS)

Livermore, Rachael C.; Finkelstein, Steven L.; Lotz, Jennifer M.

2017-01-01

The Hubble Frontier Fields program has obtained deep optical and near-infrared Hubble Space Telescope imaging of six galaxy clusters and associated parallel fields. The depth of the imaging (m_AB ~ 29) means we can identify faint galaxies at z > 6, and those in the cluster fields also benefit from magnification due to strong gravitational lensing that allows us to reach intrinsic absolute magnitudes of M_UV ~ -12.5 at z ~ 6. Here, we present the UV luminosity functions at 6 < z < 10 from the complete Hubble Frontier Fields data, revealing a steep faint-end slope that extends to the limits of the data. The lack of any apparent turnover in the luminosity functions means that faint galaxies in the early Universe may have provided sufficient ionizing radiation to sustain reionization.

The duration of reionization constrains the ionizing sources

NASA Astrophysics Data System (ADS)

Sharma, Mahavir; Theuns, Tom; Frenk, Carlos

2018-06-01

We investigate how the nature of the galaxies that reionized the Universe affects the duration of reionization. We contrast two sets of models: one in which galaxies on the faint side of the luminosity function dominate the ionizing emissivity, and a second in which the galaxies on the bright side of the luminosity function dominate. The faint end of the luminosity function evolves slowly, therefore the transition from mostly neutral to mostly ionized state takes a much longer time in the first set of models compared to the second. Existing observational constraints on the duration of this transition are relatively weak, but taken at face value prefer the model in which galaxies on the bright side play a major role. Measurements of the kinetic Sunyaev-Zeldovich effect in the cosmic microwave background from the epoch of reionization also point in the same direction.

Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A

NASA Astrophysics Data System (ADS)

Crnojevic, Denija

2014-10-01

We request HST/ACS imaging to follow up 15 new faint candidate dwarfs around the nearest elliptical Centaurus A (3.8 Mpc). The dwarfs were found via a systematic ground-based (Magellan/Megacam) survey out to ~150 kpc, designed to directly confront the "missing satellites" problem in a wholly new environment. Current Cold Dark Matter models for structure formation fail to reproduce the shallow slope of the satellite luminosity function in spiral-dominated groups for which dwarfs fainter than M_V<-14 have been surveyed (the Local Group and the nearby, interacting M81 group). Clusters of galaxies show a better agreement with cosmological predictions, suggesting an environmental dependence of the (poorly-understood) physical processes acting on the evolution of low mass galaxies (e.g., reionization). However, the luminosity function completeness for these rich environments quickly drops due to the faintness of the satellites and to the difficult cluster membership determination. We target a yet unexplored "intermediate" environment, a nearby group dominated by an elliptical galaxy, ideal due to its proximity: accurate (10%) distance determinations for its members can be derived from resolved stellar populations. The proposed observations of the candidate dwarfs will confirm their nature, group membership, and constrain their luminosities, metallicities, and star formation histories. We will obtain the first complete census of dwarf satellites of an elliptical down to an unprecedented M_V<-9. Our results will crucially constrain cosmological predictions for the faint end of the satellite luminosity function to achieve a more complete picture of the galaxy formation process.

The Luminosity Function of Star Clusters in 20 Star-Forming Galaxies Based on Hubble Legacy Archive Photometry

NASA Astrophysics Data System (ADS)

Bowers, Ariel; Whitmore, B. C.; Chandar, R.; Larsen, S. S.

2014-01-01

Luminosity functions have been determined for star cluster populations in 20 nearby (4 - 30 Mpc), star-forming galaxies based on ACS source lists generated by the Hubble Legacy Archive (http://hla.stsci.edu). These cluster catalogs provide one of the largest sets of uniform, automatically-generated cluster candidates available in the literature at present. Comparisons are made with other recently generated cluster catalogs demonstrating that the HLA-generated catalogs are of similar quality, but in general do not go as deep. A typical cluster luminosity function can be approximated by a power-law, dN/dL ∝ Lα, with an average value for α of -2.37 and rms scatter = 0.18. A comparison of fitting results based on methods which use binned and unbinned data shows good agreement, although there may be a systematic tendency for the unbinned (maximum-likelihood) method to give slightly more negative values of α for galaxies with steper luminosity functions. Our uniform database results in a small scatter (0.5 magnitude) in the correlation between the magnitude of the brightest cluster (Mbrightest) and Log of the number of clusters brighter than MI = -9 (Log N). We also examine the magnitude of the brightest cluster vs. Log SFR for a sample including LIRGS and ULIRGS.

Analysis of RGU Photometry in Selected Area 51

NASA Astrophysics Data System (ADS)

Bilir, S.; Karaali, S.; Buser, R.

2004-09-01

A low-latitude anticenter field (l=189 °, b=+21 °) is investigated by using the full calibration tools of RGU photometry. The observed RGU data are reduced to the standard system and the separation of dwarfs and evolved stars is carried out by an empirical method. Stars are categorized into three metallicity classes, i.e. -0.25<[M/H]≤+0.50, $-1.00<[M/H]≤-0.25, and [M/H]≤-1.00 dex, and their absolute magnitudes are determined by the corresponding color-magnitude diagrams. The unusually large scattering in the two-color diagrams is reduced by excluding 153 extra-galactic objects, identifying them compared with the charts of Basel Astronomical Institute and University of Minnesota, and by the criterion and algorithm of Gaidos et al. [1]. The local logarithmic space density for giants, D*(0)=6.75, lies within the local densities of Gliese and Gliese & Jahreiss. The local luminosity function in our work for the absolute magnitude interval 3

The ALMA-PILS survey: 3D modeling of the envelope, disks and dust filament of IRAS 16293-2422

NASA Astrophysics Data System (ADS)

Jacobsen, S. K.; Jørgensen, J. K.; van der Wiel, M. H. D.; Calcutt, H.; Bourke, T. L.; Brinch, C.; Coutens, A.; Drozdovskaya, M. N.; Kristensen, L. E.; Müller, H. S. P.; Wampfler, S. F.

2018-04-01

Context. The Class 0 protostellar binary IRAS 16293-2422 is an interesting target for (sub)millimeter observations due to, both, the rich chemistry toward the two main components of the binary and its complex morphology. Its proximity to Earth allows the study of its physical and chemical structure on solar system scales using high angular resolution observations. Such data reveal a complex morphology that cannot be accounted for in traditional, spherical 1D models of the envelope. Aims: The purpose of this paper is to study the environment of the two components of the binary through 3D radiative transfer modeling and to compare with data from the Atacama Large Millimeter/submillimeter Array. Such comparisons can be used to constrain the protoplanetary disk structures, the luminosities of the two components of the binary and the chemistry of simple species. Methods: We present 13CO, C17O and C18O J = 3-2 observations from the ALMA Protostellar Interferometric Line Survey (PILS), together with a qualitative study of the dust and gas density distribution of IRAS 16293-2422. A 3D dust and gas model including disks and a dust filament between the two protostars is constructed which qualitatively reproduces the dust continuum and gas line emission. Results: Radiative transfer modeling in our sampled parameter space suggests that, while the disk around source A could not be constrained, the disk around source B has to be vertically extended. This puffed-up structure can be obtained with both a protoplanetary disk model with an unexpectedly high scale-height and with the density solution from an infalling, rotating collapse. Combined constraints on our 3D model, from observed dust continuum and CO isotopologue emission between the sources, corroborate that source A should be at least six times more luminous than source B. We also demonstrate that the volume of high-temperature regions where complex organic molecules arise is sensitive to whether or not the total luminosity is in a single radiation source or distributed into two sources, affecting the interpretation of earlier chemical modeling efforts of the IRAS 16293-2422 hot corino which used a single-source approximation. Conclusions: Radiative transfer modeling of source A and B, with the density solution of an infalling, rotating collapse or a protoplanetary disk model, can match the constraints for the disk-like emission around source A and B from the observed dust continuum and CO isotopologue gas emission. If a protoplanetary disk model is used around source B, it has to have an unusually high scale-height in order to reach the dust continuum peak emission value, while fulfilling the other observational constraints. Our 3D model requires source A to be much more luminous than source B; LA 18 L⊙ and LB 3 L⊙.

THE DISTRIBUTION OF FAINT SATELLITES AROUND CENTRAL GALAXIES IN THE CANADA-FRANCE-HAWAII TELESCOPE LEGACY SURVEY

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

Jiang, C. Y.; Jing, Y. P.; Li, Cheng

2012-11-20

We investigate the radial number density profile and the abundance distribution of faint satellites around central galaxies in the low-redshift universe using the Canada-France-Hawaii Telescope (CFHT) Legacy Survey. We consider three samples of central galaxies with magnitudes of M {sub r} = -21, -22, and -23 selected from the Sloan Digital Sky Survey group catalog of Yang et al. The satellite distribution around these central galaxies is obtained by cross-correlating these galaxies with the photometric catalog of the CFHT Legacy Survey. The projected radial number density of the satellites obeys a power-law form with the best-fit logarithmic slope of -1.05,more » independent of both the central galaxy luminosity and the satellite luminosity. The projected cross-correlation function between central and satellite galaxies exhibits a non-monotonic trend with satellite luminosity. It is most pronounced for central galaxies with M {sub r} = -21, where the decreasing trend of clustering amplitude with satellite luminosity is reversed when satellites are fainter than central galaxies by more than 2 mag. A comparison with the satellite luminosity functions in the Milky Way (MW) and M31 shows that the MW/M31 system has about twice as many satellites as around a typical central galaxy of similar luminosity. The implications for theoretical models are briefly discussed.« less

The MUSE-Wide survey: a measurement of the Ly α emitting fraction among z > 3 galaxies

NASA Astrophysics Data System (ADS)

Caruana, Joseph; Wisotzki, Lutz; Herenz, Edmund Christian; Kerutt, Josephine; Urrutia, Tanya; Schmidt, Kasper Borello; Bouwens, Rychard; Brinchmann, Jarle; Cantalupo, Sebastiano; Carollo, Marcella; Diener, Catrina; Drake, Alyssa; Garel, Thibault; Marino, Raffaella Anna; Richard, Johan; Saust, Rikke; Schaye, Joop; Verhamme, Anne

2018-01-01

We present a measurement of the fraction of Lyman α (Ly α) emitters (XLy α) amongst HST continuum-selected galaxies at 3 < z < 6 with the Multi-Unit Spectroscopic Explorer (MUSE) on the VLT. Making use of the first 24 MUSE-Wide pointings in GOODS-South, each having an integration time of 1 h, we detect 100 Ly α emitters and find XLy α ≳ 0.5 for most of the redshift range covered, with 29 per cent of the Ly α sample exhibiting rest equivalent widths (rest-EWs) ≤ 15 Å. Adopting a range of rest-EW cuts (0-75 Å), we find no evidence of a dependence of XLy α on either redshift or ultraviolet luminosity.

HEAO-A2 observations of the X-ray spectra of the Centaurus and A1060 clusters of galaxies

NASA Technical Reports Server (NTRS)

Mitchell, R.; Mushotzky, R.

1979-01-01

The X-ray spectral observations of two low luminosity clusters of galaxies, Centaurus and A1060, are presented. An emission feature of the Centaurus cluster at 7.9 keV is detected at about one third of the strength of the 6.7 keV line. This higher energy line represents K sub beta emission from highly ionized iron. An isothermal model with an Fe emission line is discussed and it is shown that the model cannot fit the data of the Centaurus or the A1060 clusters. The implications of the two component nature of the continuum on the Fe abundance and the X-ray surface brightness distribution are discussed.

Detection of a new extended soft X-ray source H1538-32 - A possible old supernova remnant

NASA Technical Reports Server (NTRS)

Riegler, G. R.; Agrawal, P. C.; Gull, S. F.

1980-01-01

The discovery in the Lupus region of a new, extended soft X-ray source, H1538-32, is reported, having a distance of approximately 340 pc, and a luminosity of 1 to 2 x 10 to the 34th ergs/sec. The observed energy spectrum of the source is well fitted either by a thermal bremsstrahlung spectrum with Gaunt factor but without line emission, or by a coronal plasma model which includes the X-ray emission lines of various elements and the continuum as outlined by Raymond and Smith (1977). On the basis of the extended nature of the source and its thermal spectrum, it is suggested that H1538-32 may be an old supernova remnant.

Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?

PubMed Central

Cook, J L; Rio, E; Purdam, C R; Docking, S I

2016-01-01

The pathogenesis of tendinopathy and the primary biological change in the tendon that precipitates pathology have generated several pathoaetiological models in the literature. The continuum model of tendon pathology, proposed in 2009, synthesised clinical and laboratory-based research to guide treatment choices for the clinical presentations of tendinopathy. While the continuum has been cited extensively in the literature, its clinical utility has yet to be fully elucidated. The continuum model proposed a model for staging tendinopathy based on the changes and distribution of disorganisation within the tendon. However, classifying tendinopathy based on structure in what is primarily a pain condition has been challenged. The interplay between structure, pain and function is not yet fully understood, which has partly contributed to the complex clinical picture of tendinopathy. Here we revisit and assess the merit of the continuum model in the context of new evidence. We (1) summarise new evidence in tendinopathy research in the context of the continuum, (2) discuss tendon pain and the relevance of a model based on structure and (3) describe relevant clinical elements (pain, function and structure) to begin to build a better understanding of the condition. Our goal is that the continuum model may help guide targeted treatments and improved patient outcomes. PMID:27127294

UV-continuum slopes of >4000 z ∼ 4-8 galaxies from the HUDF/XDF, HUDF09, ERS, CANDELS-SOUTH, and CANDELS-NORTH fields

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

Bouwens, R. J.; Labbé, I.; Franx, M.

2014-10-01

We measure the UV-continuum slope β for over 4000 high-redshift galaxies over a wide range of redshifts z ∼ 4-8 and luminosities from the HST HUDF/XDF, HUDF09-1, HUDF09-2, ERS, CANDELS-N, and CANDELS-S data sets. Our new β results reach very faint levels at z ∼ 4 (–15.5 mag: 0.006 L{sub z=3}{sup ∗}), z ∼ 5 (–16.5 mag: 0.014 L{sub z=3}{sup ∗}), and z ∼ 6 and z ∼ 7 (–17 mag: 0.025 L{sub z=3}{sup ∗}). Inconsistencies between previous studies led us to conduct a comprehensive review of systematic errors and develop a new technique for measuring β that is robustmore » against biases that arise from the impact of noise. We demonstrate, by object-by-object comparisons, that all previous studies, including our own and those done on the latest HUDF12 data set, suffered from small systematic errors in β. We find that after correcting for the systematic errors (typically Δβ ∼ 0.1-0.2) all β results at z ∼ 7 from different groups are in excellent agreement. The mean β we measure for faint (–18 mag: 0.1 L{sub z=3}{sup ∗}) z ∼ 4, z ∼ 5, z ∼ 6, and z ∼ 7 galaxies is –2.03 ± 0.03 ± 0.06 (random and systematic errors), –2.14 ± 0.06 ± 0.06, –2.24 ± 0.11 ± 0.08, and –2.30 ± 0.18 ± 0.13, respectively. Our new β values are redder than we have reported in the past, but bluer than other recent results. Our previously reported trend of bluer β's at lower luminosities is confirmed, as is the evolution to bluer β's at high redshifts. β appears to show only a mild luminosity dependence faintward of M {sub UV,AB} ∼ –19 mag, suggesting that the mean β asymptotes to ∼–2.2 to –2.4 for faint z ≥ 4 galaxies. At z ∼ 7, the observed β's suggest non-zero, but low dust extinction, and they agree well with values predicted in cosmological hydrodynamical simulations.« less

Predicting the Redshift 2 H-Alpha Luminosity Function Using [OIII] Emission Line Galaxies

NASA Technical Reports Server (NTRS)

Mehta, Vihang; Scarlata, Claudia; Colbert, James W.; Dai, Y. S.; Dressler, Alan; Henry, Alaina; Malkan, Matt; Rafelski, Marc; Siana, Brian; Teplitz, Harry I.;

Full-data Results of Hubble Frontier Fields: UV Luminosity Functions at z ∼ 6–10 and a Consistent Picture of Cosmic Reionization

NASA Astrophysics Data System (ADS)

Ishigaki, Masafumi; Kawamata, Ryota; Ouchi, Masami; Oguri, Masamune; Shimasaku, Kazuhiro; Ono, Yoshiaki

2018-02-01

We present UV luminosity functions of dropout galaxies at z∼ 6{--}10 with the complete Hubble Frontier Fields data. We obtain a catalog of ∼450 dropout-galaxy candidates (350, 66, and 40 at z∼ 6{--}7, 8, and 9, respectively), with UV absolute magnitudes that reach ∼ -14 mag, ∼2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at z∼ 6{--}8 have steep faint-end slopes, α ∼ -2, and likely steeper slopes, α ≲ -2 at z∼ 9{--}10. We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond z∼ 8 in the case of {M}trunc}=-15, but an accelerated one in the case of {M}trunc}=-17. We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction Q H II at z≲ 7 based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of {f}esc}={0.17}-0.03+0.07 and {M}trunc}> -14.0 for {log}{ξ }ion}/[{erg}}-1 {Hz}]=25.34, where {f}esc} is the escape fraction, M trunc is the faint limit of the UV luminosity function, and {ξ }ion} is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be {{Δ }}z={3.9}-1.6+2.0 (for 0.1< {Q}{{H}{{II}}}< 0.99), consistent with the recent estimate from Planck.

The Radio Luminosity Function and Galaxy Evolution in the Coma Cluster

NASA Technical Reports Server (NTRS)

Miller, Neal A.; Hornschemeier, Ann E.; Mabasher, Bahram; Brudgesm Terrry J.; Hudson, Michael J.; Marzke, Ronald O.; Smith, Russell J.

2008-01-01

We investigate the radio luminosity function and radio source population for two fields within the Coma cluster of galaxies, with the fields centered on the cluster core and southwest infall region and each covering about half a square degree. Using VLA data with a typical rms sensitivity of 28 (mu)Jy per 4.4" beam, we identify 249 radio sources with optical counterparts brighter than r = 22 (equivalent to M(sub r) = -13 for cluster member galaxies). Comprehensive optical spectroscopy identifies 38 of these as members of the Coma cluster, evenly split between sources powered by an active nucleus and sources powered by active star formation. The radio-detected star-forming galaxies are restricted to radio luminosities between about 10(exp 21) and 10(exp 22) W/Hz, an interesting result given that star formation dominates field radio luminosity functions below about 10(exp 23) W/Hz. The majority of the radio-detected star-forming galaxies have characteristics of starbursts, including high specific star formation rates and optical spectra with strong emission lines. In conjunction with prior studies on post-starburst galaxies within the Coma cluster, this is consistent with a picture in which late-type galaxies entering Coma undergo a starburst prior to a rapid cessation of star formation. Optically bright elliptical galaxies (Mr less than or equals -20.5) make the largest contribution to the radio luminosity function at both the high (> approx. 3x10(exp 22) W/Hz) and low (< approx. 10(exp 21) W/Hz) ends. Through a stacking analysis of these optically-bright ellipticals we find that they continue to harbor radio sources down to luminosities as faint as 3x10(exp 19) W/Hz. However, contrary to published results for the Virgo cluster we find no evidence for the existence of a population of optically faint (M(sub r) approx. equals -14) dwarf ellipticals hosting strong radio AGN.

Clustering, cosmology and a new era of black hole demographics- II. The conditional luminosity functions of Type 2 and Type 1 active galactic nuclei

NASA Astrophysics Data System (ADS)

Ballantyne, D. R.

2017-01-01

The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line of sight into the central engine. If this model is correct then there should be no difference in many of the properties of AGN host galaxies (e.g. the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the conditional luminosity function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g. radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO Luminosity Functions and the Evolution of the Cosmic Density of Molecular Gas

NASA Astrophysics Data System (ADS)

Decarli, Roberto; Walter, Fabian; Aravena, Manuel; Carilli, Chris; Bouwens, Rychard; da Cunha, Elisabete; Daddi, Emanuele; Ivison, R. J.; Popping, Gergö; Riechers, Dominik; Smail, Ian R.; Swinbank, Mark; Weiss, Axel; Anguita, Timo; Assef, Roberto J.; Bauer, Franz E.; Bell, Eric F.; Bertoldi, Frank; Chapman, Scott; Colina, Luis; Cortes, Paulo C.; Cox, Pierre; Dickinson, Mark; Elbaz, David; Gónzalez-López, Jorge; Ibar, Edo; Infante, Leopoldo; Hodge, Jacqueline; Karim, Alex; Le Fevre, Olivier; Magnelli, Benjamin; Neri, Roberto; Oesch, Pascal; Ota, Kazuaki; Rix, Hans-Walter; Sargent, Mark; Sheth, Kartik; van der Wel, Arjen; van der Werf, Paul; Wagg, Jeff

2016-12-01

In this paper we use ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to z ˜ 4.5. This study is based on galaxies that have been selected solely through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted “knee” of the CO luminosity function (around 5 × 109 K km s-1 pc2). We find clear evidence of an evolution in the CO luminosity function with respect to z ˜ 0, with more CO-luminous galaxies present at z ˜ 2. The observed galaxies at z ˜ 2 also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a drop by a factor of 3-10 from z ˜ 2 to z ˜ 0 (with significant error bars), and possibly a decline at z > 3. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation (z ˜ 2).

An oculomotor continuum from exploration to fixation

PubMed Central

Otero-Millan, Jorge; Macknik, Stephen L.; Langston, Rachel E.; Martinez-Conde, Susana

2013-01-01

During visual exploration, saccadic eye movements scan the scene for objects of interest. During attempted fixation, the eyes are relatively still but often produce microsaccades. Saccadic rates during exploration are higher than those of microsaccades during fixation, reinforcing the classic view that exploration and fixation are two distinct oculomotor behaviors. An alternative model is that fixation and exploration are not dichotomous, but are instead two extremes of a functional continuum. Here, we measured the eye movements of human observers as they either fixed their gaze on a small spot or scanned natural scenes of varying sizes. As scene size diminished, so did saccade rates, until they were continuous with microsaccadic rates during fixation. Other saccadic properties varied as function of image size as well, forming a continuum with microsaccadic parameters during fixation. This saccadic continuum extended to nonrestrictive, ecological viewing conditions that allowed all types of saccades and fixation positions. Eye movement simulations moreover showed that a single model of oculomotor behavior can explain the saccadic continuum from exploration to fixation, for images of all sizes. These findings challenge the view that exploration and fixation are dichotomous, suggesting instead that visual fixation is functionally equivalent to visual exploration on a spatially focused scale. PMID:23533278

Stonefly (Plecoptera) Feeding Modes: Variation Along a California River Continuum

Treesearch

Richard L. Bottorff; Allen W. Knight

1989-01-01

The distribution of Plecoptera along a California river was used to test several predictions of the River Continuum Concept about how functional feeding groups should change along a stream's length. Stoneflies were collected from stream orders 1-6 (123 km) of the Cosumnes River continuum in the central Sierra Nevada. The 69 stonefly species collected were...

HST Imaging of the Brightest z ∼ 8–9 Galaxies from UltraVISTA: The Extreme Bright End of the UV Luminosity Function

NASA Astrophysics Data System (ADS)

Stefanon, Mauro; Labbé, Ivo; Bouwens, Rychard J.; Brammer, Gabriel B.; Oesch, Pascal; Franx, Marijn; Fynbo, Johan P. U.; Milvang-Jensen, Bo; Muzzin, Adam; Illingworth, Garth D.; Le Fèvre, Olivier; Caputi, Karina I.; Holwerda, Benne W.; McCracken, Henry J.; Smit, Renske; Magee, Dan

2017-12-01

We report on the discovery of three especially bright candidate {z}{phot}≳ 8 galaxies. Five sources were targeted for follow-up with the Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3), selected from a larger sample of 16 bright (24.8≲ H≲ 25.5 mag) candidate z≳ 8 Lyman break galaxies (LBGs) identified over 1.6 degrees2 of the COSMOS/UltraVISTA field. These were selected as Y and J dropouts by leveraging the deep (Y-to-{K}{{S}}∼ 25.3{--}24.8 mag, 5σ ) NIR data from the UltraVISTA DR3 release, deep ground-based optical imaging from the CFHTLS and Suprime-Cam programs, and Spitzer/IRAC mosaics combining observations from the SMUVS and SPLASH programs. Through the refined spectral energy distributions, which now also include new HyperSuprimeCam g-, r-, i-, z-, and Y-band data, we confirm that 3/5 galaxies have robust {z}{phot}∼ 8.0{--}8.7, consistent with the initial selection. The remaining 2/5 galaxies have a nominal {z}{phot}∼ 2. However, with HST data alone, these objects have increased probability of being at z∼ 9. We measure mean UV continuum slopes β =-1.74+/- 0.35 for the three z∼ 8{--}9 galaxies, marginally bluer than similarly luminous z∼ 4{--}6 in CANDELS but consistent with previous measurements of similarly luminous galaxies at z∼ 7. The circularized effective radius for our brightest source is 0.9 ± 0.3 kpc, similar to previous measurements for a bright z∼ 11 galaxy and bright z∼ 7 galaxies. Finally, enlarging our sample to include the six brightest z∼ 8 LBGs identified over UltraVISTA (i.e., including three other sources from Labbé et al.) we estimate for the first time the volume density of galaxies at the extreme bright end ({M}{UV}∼ -22 mag) of the z∼ 8 UV luminosity function. Despite this exceptional result, the still large statistical uncertainties do not allow us to discriminate between a Schechter and a double-power-law form.

Precision Fe K-Alpha and Fe K-Beta Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku

NASA Technical Reports Server (NTRS)

Yaqoob, Tahir; Murphy, Kendrah D.; Griffiths, Richard E.; Haba, Yoshito; Inoue, Hajime; Itoh, Takeshi; Kelley, Richard; Kokubun, Motohide; Markowitz, Alex; Mushotzky, Richard;

An advanced kinetic theory for morphing continuum with inner structures

NASA Astrophysics Data System (ADS)

Chen, James

2017-12-01

Advanced kinetic theory with the Boltzmann-Curtiss equation provides a promising tool for polyatomic gas flows, especially for fluid flows containing inner structures, such as turbulence, polyatomic gas flows and others. Although a Hamiltonian-based distribution function was proposed for diatomic gas flow, a general distribution function for the generalized Boltzmann-Curtiss equations and polyatomic gas flow is still out of reach. With assistance from Boltzmann's entropy principle, a generalized Boltzmann-Curtiss distribution for polyatomic gas flow is introduced. The corresponding governing equations at equilibrium state are derived and compared with Eringen's morphing (micropolar) continuum theory derived under the framework of rational continuum thermomechanics. Although rational continuum thermomechanics has the advantages of mathematical rigor and simplicity, the presented statistical kinetic theory approach provides a clear physical picture for what the governing equations represent.

IUEAGN: A database of ultraviolet spectra of active galactic nuclei

NASA Technical Reports Server (NTRS)

Pike, G.; Edelson, R.; Shull, J. M.; Saken, J.

1993-01-01

In 13 years of operation, IUE has gathered approximately 5000 spectra of almost 600 Active Galactic Nuclei (AGN). In order to undertake AGN studies which require large amounts of data, we are consistently reducing this entire archive and creating a homogeneous, easy-to-use database. First, the spectra are extracted using the Optimal extraction algorithm. Continuum fluxes are then measured across predefined bands, and line fluxes are measured with a multi-component fit. These results, along with source information such as redshifts and positions, are placed in the IUEAGN relational database. Analysis algorithms, statistical tests, and plotting packages run within the structure, and this flexible database can accommodate future data when they are released. This archival approach has already been used to survey line and continuum variability in six bright Seyfert 1s and rapid continuum variability in 14 blazars. Among the results that could only be obtained using a large archival study is evidence that blazars show a positive correlation between degree of variability and apparent luminosity, while Seyfert 1s show an anti-correlation. This suggests that beaming dominates the ultraviolet properties for blazars, while thermal emission from an accretion disk dominates for Seyfert 1s. Our future plans include a survey of line ratios in Seyfert 1s, to be fitted with photoionization models to test the models and determine the range of temperatures, densities and ionization parameters. We will also include data from IRAS, Einstein, EXOSAT, and ground-based telescopes to measure multi-wavelength correlations and broadband spectral energy distributions.

Multi-wavelength Radio Continuum Emission Studies of Dust-free Red Giants

NASA Technical Reports Server (NTRS)

O'Gorman, Eamon; Harper, Graham M.; Brown, Alexander; Dranke, Stephen; Richards, Anita M. S.

2013-01-01

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (alpha Boo: K2 III) and Aldebaran (alpha Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained a snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for alpha Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of alpha Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For alpha Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of alpha Boo. Finally, we develop a simple analytical wind model for alpha Boo based on our new long-wavelength flux measurements.

The Association of Molecular Gas and Natal Super Star Clusters in Henize 2–10

NASA Astrophysics Data System (ADS)

Johnson, Kelsey E.; Brogan, Crystal L.; Indebetouw, Remy; Testi, Leonardo; Wilner, David J.; Reines, Amy E.; Chen, C.-H. Rosie; Vanzi, Leonardo

2018-02-01

We present ALMA observations of the dwarf starburst galaxy He 2–10 in combination with previous SMA CO observations to probe the molecular environments of natal super star clusters (SSCs). These observations include the HCO+(1-0), HCN(1-0), HNC(1-0), and CCH(1-0) molecular lines, as well as 88 GHz continuum with a spatial resolution of 1\\buildrel{\\prime\\prime}\\over{.} 7× 1\\buildrel{\\prime\\prime}\\over{.} 6. After correcting for the contribution from free–free emission to the 88 GHz continuum flux density (∼60% of the 88 GHz emission), we derive a total gas mass for He 2–10 of {M}{gas}=4{--}6× {10}8 M ⊙, roughly 5%–20% of the dynamical mass. Based on a principle component analysis, HCO+ is found to be the best “general” tracer of molecular emission. The line widths and luminosities of the CO emission suggests that the molecular clouds could either be as small as ∼8 pc, or alternately have enhanced line widths. The CO emission and 88 GHz continuum are anti-correlated, suggesting that either the dust and molecular gas are not cospatial, which could reflect that the 88 GHz continuum is dominated by free–free emission. The CO and CCH emission are also relatively anti-correlated, which is consistent with the CCH being photo-enhanced, and/or the CO being dissociated in the regions near the natal SSCs. The molecular line ratios of regions containing the natal star clusters are different from the line ratios observed for regions elsewhere in the galaxy. In particular, the regions with thermal radio emission all have {CO}(2{--}1)/{{HCO}}+(1-0)< 16, and the HCO+/CO ratio appears to be correlated with the evolutionary stage of the clusters.

MULTI-WAVELENGTH RADIO CONTINUUM EMISSION STUDIES OF DUST-FREE RED GIANTS

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

O'Gorman, Eamon; Harper, Graham M.; Brown, Alexander

2013-10-01

Multi-wavelength centimeter continuum observations of non-dusty, non-pulsating K spectral-type red giants directly sample their chromospheres and wind acceleration zones. Such stars are feeble emitters at these wavelengths, however, and previous observations have provided only a small number of modest signal-to-noise measurements slowly accumulated over three decades. We present multi-wavelength Karl G. Jansky Very Large Array thermal continuum observations of the wind acceleration zones of two dust-free red giants, Arcturus (α Boo: K2 III) and Aldebaran (α Tau: K5 III). Importantly, most of our observations of each star were carried out over just a few days, so that we obtained amore » snapshot of the different stellar atmospheric layers sampled at different wavelengths, independent of any long-term variability. We report the first detections at several wavelengths for each star including a detection at 10 cm (3.0 GHz: S band) for both stars and a 20 cm (1.5 GHz: L band) detection for α Boo. This is the first time single (non-binary) luminosity class III red giants have been detected at these continuum wavelengths. Our long-wavelength data sample the outer layers of α Boo's atmosphere where its wind velocity is approaching (or possibly has reached) its terminal value and the ionization balance is becoming frozen-in. For α Tau, however, our long-wavelength data are still sampling its inner atmosphere, where the wind is still accelerating probably due to its lower mass-loss rate. We compare our data with published semi-empirical models based on ultraviolet data, and the marked deviations highlight the need for new atmospheric models to be developed. Spectral indices are used to discuss the possible properties of the stellar atmospheres, and we find evidence for a rapidly cooling wind in the case of α Boo. Finally, we develop a simple analytical wind model for α Boo based on our new long-wavelength flux measurements.« less

The CALYMHA survey: Lyα luminosity function and global escape fraction of Lyα photons at z = 2.23

NASA Astrophysics Data System (ADS)

Sobral, David; Matthee, Jorryt; Best, Philip; Stroe, Andra; Röttgering, Huub; Oteo, Iván; Smail, Ian; Morabito, Leah; Paulino-Afonso, Ana

2017-04-01

We present the CAlibrating LYMan-α with Hα (CALYMHA) pilot survey and new results on Lyman α (Lyα) selected galaxies at z ˜ 2. We use a custom-built Lyα narrow-band filter at the Isaac Newton Telescope, designed to provide a matched volume coverage to the z = 2.23 Hα HiZELS survey. Here, we present the first results for the COSMOS and UDS fields. Our survey currently reaches a 3σ line flux limit of ˜4 × 10-17 erg s-1 cm-2, and a Lyα luminosity limit of ˜1042.3 erg s-1. We find 188 Lyα emitters over 7.3 × 105 Mpc3, but also find significant numbers of other line-emitting sources corresponding to He II, C III] and C IV emission lines. These sources are important contaminants, and we carefully remove them, unlike most previous studies. We find that the Lyα luminosity function at z = 2.23 is very well described by a Schechter function up to LLy α ≈ 1043 erg s-1 with L^{ast }=10^{42.59^{+0.16}_{-0.08}} erg s-1, φ ^{ast }=10^{-3.09^{+0.14}_{-0.34}} Mpc-3 and α = -1.75 ± 0.25. Above LLy α ≈ 1043 erg s-1, the Lyα luminosity function becomes power-law like, driven by X-ray AGN. We find that Lyα-selected emitters have a high escape fraction of 37 ± 7 per cent, anticorrelated with Lyα luminosity and correlated with Lyα equivalent width. Lyα emitters have ubiquitous large (≈40 kpc) Lyα haloes, ˜2 times larger than their Hα extents. By directly comparing our Lyα and Hα luminosity functions, we find that the global/overall escape fraction of Lyα photons (within a 13 kpc radius) from the full population of star-forming galaxies is 5.1 ± 0.2 per cent at the peak of the star formation history. An extra 3.3 ± 0.3 per cent of Lyα photons likely still escape, but at larger radii.

A Chandra observation of the interacting pair of galaxies NGC 4485/4490

NASA Astrophysics Data System (ADS)

Roberts, T. P.; Warwick, R. S.; Ward, M. J.; Murray, S. S.

2002-12-01

We report the results of a 20-ks Chandra ACIS-S observation of the galaxy pair NGC 4485/4490. This is an interacting system containing a late-type spiral with an enhanced star formation rate (NGC 4490), and an irregular companion that possesses a disturbed morphology. A total of 29 discrete X-ray sources are found coincident with NGC 4490, but only one is found within NGC 4485. The sources range in observed X-ray luminosity from ~2 × 1037 to 4 × 1039 erg s-1. The more luminous sources appear, on average, to be spectrally harder than the fainter sources, an effect that is attributable to increased absorption in their spectra. Extensive diffuse X-ray emission is detected coincident with the disc of NGC 4490, and in the tidal tail of NGC 4485, which appears to be thermal in nature and hence the signature of a hot interstellar medium in both galaxies. However, the diffuse component accounts for only ~10 per cent of the total X-ray luminosity of the system (2 × 1040 erg s-1, 0.5-8 keV), which arises predominantly in a handful of the brightest discrete sources. This diffuse emission fraction is unusually low for a galaxy pair which has many characteristics that would lead it to be classified as a starburst system, possibly as a consequence of the small gravitational potential well of the system. The discrete source population, on the other hand, is similar to that observed in other starburst systems, possessing a flat luminosity function slope of ~-0.6 and a total of six ultraluminous X-ray sources (ULX). Five of the ULX are identified as probable black hole X-ray binary systems, and the sixth (which is coincident with a radio continuum source) is identified as an X-ray luminous supernova remnant. The ULX all lie in star formation regions, providing further evidence of the link between the ULX phenomenon and active star formation. Importantly, this shows that even in star-forming regions, the ULX population is dominated by accreting systems. We discuss the implications of this work for physical models of the nature of ULX, and in particular how it argues against the intermediate-mass black hole hypothesis.

The Bivariate Luminosity--HI Mass Distribution Function of Galaxies based on the NIBLES Survey

NASA Astrophysics Data System (ADS)

Butcher, Zhon; Schneider, Stephen E.; van Driel, Wim; Lehnert, Matt

2016-01-01

We use 21cm HI line observations for 2610 galaxies from the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) to derive a bivariate luminosity--HI mass distribution function. Our HI survey was selected to randomly probe the local (900 < cz < 12,000 km/s) galaxy population in each 0.5 mag wide bin for the absolute z-band magnitude range of -13.5 < Mz < -24 without regard to morphology or color. This targeted survey allowed more on-source integration time for weak and non-detected sources, enabling us to probe lower HI mass fractions and apply lower upper limits for non-detections than would be possible with the larger blind HI surveys. Additionally, we obtained a factor of four higher sensitivity follow-up observations at Arecibo of 90 galaxies from our non-detected and marginally detected categories to quantify the underlying HI distribution of sources not detected at Nançay. Using the optical luminosity function and our higher sensitivity follow up observations as priors, we use a 2D stepwise maximum likelihood technique to derive the two dimensional volume density distribution of luminosity and HI mass in each SDSS band.

ROSAT all-sky survey on the Einstein EMSS sample

NASA Technical Reports Server (NTRS)

Maccacaro, Tomasso

1992-01-01

The cosmological evolution and the luminosity function (XLF) of X ray selected Active Galactic Nuclei (AGN's) are discussed. The sample used is extracted from the Einstein Observatory Extended Medium Sensitivity Surveys (EMSS) and consists of more than 420 objects. Preliminary results from the ROSAT All-Sky Survey data confirm the correctness of the optical identification of the EMSS sources, thus giving confidence to the results obtained from the analysis of the AGN's sample. The XLF observed at different redshifts (up to z approx. 2) gives direct evidence of cosmological evolution. Data have been analyzed within the framework of luminosity evolution models and the two most common evolutionary forms, L sub x(Z) = L sub x(0) x e(sup Cr) and L sub x(Z) = L sub x(0) x (1 + z)(exp C), have been considered. Luminosity dependent evolution is required if the evolution function has the exponential form, whereas the simpler pure luminosity evolution model is still acceptable if the evolution function has the power law form. Using the whole sample of objects the number-counts and the de-evolved (z = 0) XLF have been derived. A comparison of the EMSS data with preliminary ROSAT results presented at this meeting indicates an overall agreement.

A space-time tensor formulation for continuum mechanics in general curvilinear, moving, and deforming coordinate systems

NASA Technical Reports Server (NTRS)

Avis, L. M.

1976-01-01

Tensor methods are used to express the continuum equations of motion in general curvilinear, moving, and deforming coordinate systems. The space-time tensor formulation is applicable to situations in which, for example, the boundaries move and deform. Placing a coordinate surface on such a boundary simplifies the boundary condition treatment. The space-time tensor formulation is also applicable to coordinate systems with coordinate surfaces defined as surfaces of constant pressure, density, temperature, or any other scalar continuum field function. The vanishing of the function gradient components along the coordinate surfaces may simplify the set of governing equations. In numerical integration of the equations of motion, the freedom of motion of the coordinate surfaces provides a potential for enhanced resolution of the continuum field function. An example problem of an incompressible, inviscid fluid with a top free surface is considered, where the surfaces of constant pressure (including the top free surface) are coordinate surfaces.

Shape dependence of two-cylinder Rényi entropies for free bosons on a lattice

NASA Astrophysics Data System (ADS)

Chojnacki, Leilee; Cook, Caleb Q.; Dalidovich, Denis; Hayward Sierens, Lauren E.; Lantagne-Hurtubise, Étienne; Melko, Roger G.; Vlaar, Tiffany J.

2016-10-01

Universal scaling terms occurring in Rényi entanglement entropies have the potential to bring new understanding to quantum critical points in free and interacting systems. Quantitative comparisons between analytical continuum theories and numerical calculations on lattice models play a crucial role in advancing such studies. In this paper, we exactly calculate the universal two-cylinder shape dependence of entanglement entropies for free bosons on finite-size square lattices, and compare to approximate functions derived in the continuum using several different Ansätze. Although none of these Ansätze are exact in the thermodynamic limit, we find that numerical fits are in good agreement with continuum functions derived using the anti-de Sitter/conformal field theory correspondence, an extensive mutual information model, and a quantum Lifshitz model. We use fits of our lattice data to these functions to calculate universal scalars defined in the thin-cylinder limit, and compare to values previously obtained for the free boson field theory in the continuum.

The Cool White Dwarf Luminosity Function and the Age of the Galactic Disk

NASA Astrophysics Data System (ADS)

Leggett, S. K.; Ruiz, Maria Teresa; Bergeron, P.

1998-04-01

We present new optical and infrared data for the cool white dwarfs in the proper motion sample of Liebert, Dahn, & Monet. Stellar properties--surface chemical composition, effective temperature, radius, surface gravity, mass, and luminosity--are determined from these data by using the model atmospheres of Bergeron, Saumon, & Wesemael. The space density contribution is calculated for each star and the luminosity function (LF) for cool white dwarfs is determined. Comparing the LF to the most recent cooling sequences by Wood implies that the age of the local region of the Galactic disk is 8 +/- 1.5 Gyr. This result is consistent with the younger ages now being derived for the globular clusters and the universe itself.

Primeval galaxies and cold dark matter

NASA Technical Reports Server (NTRS)

Silk, Joseph; Szalay, Alexander S.

1987-01-01

In the context of the cold dark matter theory for the large-scale matter distribution, the onset of galaxy formation is a gradual process, with star formation being initiated at z = about 10 and reaching a peak for luminous galaxies at z = about 1. The mass function of galaxy cores matches the observed quasar luminosity function at z = 2-3. Primeval galaxies are envisaged as a collection of many interacting and merging clumps, attaining a peak luminosity that is an order of magnitude below that achieved in models in which galaxy formation is initiated abruptly. Hence, ongoing searches for primeval galaxies would not necessarily have been successful unless they are designed to find moderately low-luminosity, low-surface-brigtness extended objects at low redshift.

LFlGRB: Luminosity function of long gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFlGRB models the luminosity function (LF) of long Gamma Ray Bursts (lGRBs) by using a sample of Swift and Fermi lGRBs to re-derive the parameters of the Yonetoku correlation and self-consistently estimate pseudo-redshifts of all the bursts with unknown redshifts. The GRB formation rate is modeled as the product of the cosmic star formation rate and a GRB formation efficiency for a given stellar mass.

Luminosity determination in pp collisions at $$\\sqrt{s} = 7$$ TeV using the ATLAS detector at the LHC

DOE PAGES

Aad, G.; Abbott, B.; Abdallah, J.; ...

2011-04-27

Measurements of luminosity obtained using the ATLAS detector during early running of the Large Hadron Collider (LHC) at √s = 7 TeV are presented. The luminosity is independently determined using several detectors and multiple algorithms, each having different acceptances, systematic uncertainties and sensitivity to background. The ratios of the luminosities obtained from these methods are monitored as a function of time and of μ, the average number of inelastic interactions per bunch crossing. Residual time- and μ-dependence between the methods is less than 2% for 0 < μ < 2.5. Absolute luminosity calibrations, performed using beam separation scans, have amore » common systematic uncertainty of ±11%, dominated by the measurement of the LHC beam currents. After calibration, the luminosities obtained from the different methods differ by at most ±2%. The visible cross sections measured using the beam scans are compared to predictions obtained with the PYTHIA and PHOJET event generators and the ATLAS detector simulation.« less

Precision Luminosity of LHC Proton-Proton Collisions at 13 TeV Using Hit Counting With TPX Pixel Devices

NASA Astrophysics Data System (ADS)

Sopczak, André; Ali, Babar; Asawatavonvanich, Thanawat; Begera, Jakub; Bergmann, Benedikt; Billoud, Thomas; Burian, Petr; Caicedo, Ivan; Caforio, Davide; Heijne, Erik; Janeček, Josef; Leroy, Claude; Mánek, Petr; Mochizuki, Kazuya; Mora, Yesid; Pacík, Josef; Papadatos, Costa; Platkevič, Michal; Polanský, Štěpán; Pospíšil, Stanislav; Suk, Michal; Svoboda, Zdeněk

2017-03-01

A network of Timepix (TPX) devices installed in the ATLAS cavern measures the LHC luminosity as a function of time as a stand-alone system. The data were recorded from 13-TeV proton-proton collisions in 2015. Using two TPX devices, the number of hits created by particles passing the pixel matrices was counted. A van der Meer scan of the LHC beams was analyzed using bunch-integrated luminosity averages over the different bunch profiles for an approximate absolute luminosity normalization. It is demonstrated that the TPX network has the capability to measure the reduction of LHC luminosity with precision. Comparative studies were performed among four sensors (two sensors in each TPX device) and the relative short-term precision of the luminosity measurement was determined to be 0.1% for 10-s time intervals. The internal long-term time stability of the measurements was below 0.5% for the data-taking period.

A study of the luminosity function for field galaxies. [non-rich-cluster galaxies

NASA Technical Reports Server (NTRS)

Felten, J. E.

1977-01-01

Nine determinations of the luminosity function (LF) for field galaxies are analyzed and compared. Corrections for differences in Hubble constants, magnitude systems, galactic absorption functions, and definitions of the LF are necessary prior to comparison. Errors in previous comparisons are pointed out. After these corrections, eight of the nine determinations are in fairly good agreement. The discrepancy in the ninth appears to be mainly an incompleteness effect. The LF data suggest that there is little if any distinction between field galaxies and those in small groups.

A study of the discrepant QSO X-ray luminosity function from the HEAO-2 data archive

NASA Technical Reports Server (NTRS)

Margon, B.

1984-01-01

An in-progress investigation aimed at characterizing the X-ray luminosity of very faint QSOs is described. More than 100 faint, previously uncataloged QSOs which lie in areas imaged in X rays at very high sensitivity were discovered.

Reverberation Mapping the Dusty Torus in Active Galactic Nuclei: the Influence of Torus Geometry and Structure on the Measured Reverberation Radius

NASA Astrophysics Data System (ADS)

Almeyda, Triana

2018-01-01

The obscuring circumnuclear dusty torus is a cornerstone of AGN unification, yet its shape, composition, and structure have not been well constrained. Infrared (IR) interferometry can partially resolve the dust structures in nearby AGN. However, the size and structure of the torus can also be investigated at all redshifts by reverberation mapping, that is, analyzing the temporal variability of the torus dust emission in response to changes in the AGN luminosity. In simple models, the lag between the AGN optical continuum variations and the torus IR response is directly related to the effective size of the emitting region. However, the IR response is sensitive to many poorly constrained variables including the geometry and illumination of the torus, which complicates the interpretation of measured reverberation lags. I will present results from the first comprehensive analysis of the multi-wavelength IR torus response, showing how various structural and geometrical torus parameters influence the measured lag. A library of torus response functions has been computed using a new code, TORMAC, which simulates the temporal response of the IR emission of a 3D ensemble of dust clouds given an input optical light curve. TORMAC accounts for anisotropic emission from the dust clouds, inter-cloud and AGN-cloud shadowing, and anisotropic illumination of the torus by the AGN continuum source. We can use the model grid to quantify the relationship between the lag and the effective size of the torus for various torus parameters at any selected wavelength. Although the shapes of the response functions vary widely over our grid parameter range, the reverberation lag provides an estimate of the effective torus radius that is always within a factor of 2.5. TORMAC can also be used to model observed IR light curves; we present preliminary simulations for the “changing-look” Seyfert galaxy, NGC 6418, which exhibited large IR variability during a recent Spitzer monitoring campaign. This work will aid in the interpretation of reverberation mapping measurements, especially for the new VEILS wide field near-IR extragalactic time domain survey, whose aim is to use AGN IR reverberation mapping lags as cosmological standard candles.

Assessment and Therapeutic Application of the Expressive Therapies Continuum: Implications for Brain Structures and Functions

ERIC Educational Resources Information Center

Lusebrink, Vija B.

2010-01-01

The Expressive Therapies Continuum (ETC) provides a theoretical model for art-based assessments and applications of media in art therapy. The three levels of the ETC (Kinesthetic/Sensory, Perceptual/Affective, and Cognitive/Symbolic) appear to reflect different functions and structures in the brain that process visual and affective information.…

X-ray studies of quasars with the Einstein Observatory. II

NASA Technical Reports Server (NTRS)

Zamorani, G.; Maccacaro, T.; Henry, J. P.; Tananbaum, H.; Soltan, A.; Liebert, J.; Stocke, J.; Strittmatter, P. A.; Weymann, R. J.; Smith, M. G.

1981-01-01

X-ray observations of 107 quasars have been carried out with the Einstein Observatory, and 79 have been detected. A correlation between optical emission and X-ray emission is found; and for radio-loud quasars, the data show a correlation between radio emission and X-ray emission. For a given optical luminosity, the average X-ray emission of radio-loud quasars is about three times higher than that of radio-quiet quasars. The data also suggest that the ratio of X-ray to optical luminosity is decreasing with increasing redshift and/or optical luminosity. The data support the picture in which luminosity evolution, rather than pure density evolution, describes the quasar behavior as a function of redshift.

The Seven Sisters DANCe. I. Empirical isochrones, luminosity, and mass functions of the Pleiades cluster

NASA Astrophysics Data System (ADS)

Bouy, H.; Bertin, E.; Sarro, L. M.; Barrado, D.; Moraux, E.; Bouvier, J.; Cuillandre, J.-C.; Berihuete, A.; Olivares, J.; Beletsky, Y.

2015-05-01

Context. The DANCe survey provides photometric and astrometric (position and proper motion) measurements for approximately 2 million unique sources in a region encompassing ~80 deg2 centered on the Pleiades cluster. Aims: We aim at deriving a complete census of the Pleiades and measure the mass and luminosity functions of the cluster. Methods: Using the probabilistic selection method previously described, we identified high probability members in the DANCe (i ≥ 14 mag) and Tycho-2 (V ≲ 12 mag) catalogues and studied the properties of the cluster over the corresponding luminosity range. Results: We find a total of 2109 high-probability members, of which 812 are new, making it the most extensive and complete census of the cluster to date. The luminosity and mass functions of the cluster are computed from the most massive members down to ~0.025 M⊙. The size, sensitivity, and quality of the sample result in the most precise luminosity and mass functions observed to date for a cluster. Conclusions: Our census supersedes previous studies of the Pleiades cluster populations, in terms of both sensitivity and accuracy. Based on service observations made with the William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Table 1 and Appendices are available in electronic form at http://www.aanda.orgDANCe catalogs (Tables 6 and 7) and full Tables 2-5 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A148

Stochastic simulation tools and continuum models for describing two-dimensional collective cell spreading with universal growth functions

NASA Astrophysics Data System (ADS)

Jin, Wang; Penington, Catherine J.; McCue, Scott W.; Simpson, Matthew J.

2016-10-01

Two-dimensional collective cell migration assays are used to study cancer and tissue repair. These assays involve combined cell migration and cell proliferation processes, both of which are modulated by cell-to-cell crowding. Previous discrete models of collective cell migration assays involve a nearest-neighbour proliferation mechanism where crowding effects are incorporated by aborting potential proliferation events if the randomly chosen target site is occupied. There are two limitations of this traditional approach: (i) it seems unreasonable to abort a potential proliferation event based on the occupancy of a single, randomly chosen target site; and, (ii) the continuum limit description of this mechanism leads to the standard logistic growth function, but some experimental evidence suggests that cells do not always proliferate logistically. Motivated by these observations, we introduce a generalised proliferation mechanism which allows non-nearest neighbour proliferation events to take place over a template of r≥slant 1 concentric rings of lattice sites. Further, the decision to abort potential proliferation events is made using a crowding function, f(C), which accounts for the density of agents within a group of sites rather than dealing with the occupancy of a single randomly chosen site. Analysing the continuum limit description of the stochastic model shows that the standard logistic source term, λ C(1-C), where λ is the proliferation rate, is generalised to a universal growth function, λ C f(C). Comparing the solution of the continuum description with averaged simulation data indicates that the continuum model performs well for many choices of f(C) and r. For nonlinear f(C), the quality of the continuum-discrete match increases with r.

Evolution of plastic anisotropy for high-strain-rate computations

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

Schiferl, S.K.; Maudlin, P.J.

1994-12-01

A model for anisotropic material strength, and for changes in the anisotropy due to plastic strain, is described. This model has been developed for use in high-rate, explicit, Lagrangian multidimensional continuum-mechanics codes. The model handles anisotropies in single-phase materials, in particular the anisotropies due to crystallographic texture--preferred orientations of the single-crystal grains. Textural anisotropies, and the changes in these anisotropies, depend overwhelmingly no the crystal structure of the material and on the deformation history. The changes, particularly for a complex deformations, are not amenable to simple analytical forms. To handle this problem, the material model described here includes a texturemore » code, or micromechanical calculation, coupled to a continuum code. The texture code updates grain orientations as a function of tensor plastic strain, and calculates the yield strength in different directions. A yield function is fitted to these yield points. For each computational cell in the continuum simulation, the texture code tracks a particular set of grain orientations. The orientations will change due to the tensor strain history, and the yield function will change accordingly. Hence, the continuum code supplies a tensor strain to the texture code, and the texture code supplies an updated yield function to the continuum code. Since significant texture changes require relatively large strains--typically, a few percent or more--the texture code is not called very often, and the increase in computer time is not excessive. The model was implemented, using a finite-element continuum code and a texture code specialized for hexagonal-close-packed crystal structures. The results for several uniaxial stress problems and an explosive-forming problem are shown.« less

Stochastic simulation tools and continuum models for describing two-dimensional collective cell spreading with universal growth functions.

PubMed

Jin, Wang; Penington, Catherine J; McCue, Scott W; Simpson, Matthew J

2016-10-07

Two-dimensional collective cell migration assays are used to study cancer and tissue repair. These assays involve combined cell migration and cell proliferation processes, both of which are modulated by cell-to-cell crowding. Previous discrete models of collective cell migration assays involve a nearest-neighbour proliferation mechanism where crowding effects are incorporated by aborting potential proliferation events if the randomly chosen target site is occupied. There are two limitations of this traditional approach: (i) it seems unreasonable to abort a potential proliferation event based on the occupancy of a single, randomly chosen target site; and, (ii) the continuum limit description of this mechanism leads to the standard logistic growth function, but some experimental evidence suggests that cells do not always proliferate logistically. Motivated by these observations, we introduce a generalised proliferation mechanism which allows non-nearest neighbour proliferation events to take place over a template of [Formula: see text] concentric rings of lattice sites. Further, the decision to abort potential proliferation events is made using a crowding function, f(C), which accounts for the density of agents within a group of sites rather than dealing with the occupancy of a single randomly chosen site. Analysing the continuum limit description of the stochastic model shows that the standard logistic source term, [Formula: see text], where λ is the proliferation rate, is generalised to a universal growth function, [Formula: see text]. Comparing the solution of the continuum description with averaged simulation data indicates that the continuum model performs well for many choices of f(C) and r. For nonlinear f(C), the quality of the continuum-discrete match increases with r.

The luminosity function of quasars

NASA Technical Reports Server (NTRS)

Pei, Yichuan C.

1995-01-01

We propose a new evolutionary model for the optical luminosity function of quasars. Our analytical model is derived from fits to the empirical luminosity function estimated by Hartwick and Schade and Warren, Hewett, and Osmer on the basis of more than 1200 quasars over the range of redshifts 0 approximately less than z approximately less than 4.5. We find that the evolution of quasars over this entire redshift range can be well fitted by a Gaussian distribution, while the shape of the luminosity function can be well fitted by either a double power law or an exponential L(exp 1/4) law. The predicted number counts of quasars, as a function of either apparent magnitude or redshift, are fully consistent with the observed ones. Our model indicates that the evolution of quasars reaches its maximum at z approximately = 2.8 and declines at higher redshifts. An extrapolation of the evolution to z approximately greater than 4.5 implies that quasars may have started their cosmic fireworks at z(sub f) approximately = 5.2-5.5. Forthcoming surveys of quasars at these redshifts will be critical to constrain the epoch of quasar formation. All the results we derived are based on observed quasars and are therefore subject to the bias of obscuration by dust in damped Ly alpha systems. Future surveys of these absorption systems at z approximately greater than 3 will also be important if the formation epoch of quasars is to be known unambiguously.

THE INFLUENCE OF RED SPIRAL GALAXIES ON THE SHAPE OF THE LOCAL K-BAND LUMINOSITY FUNCTION

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

Bonne, Nicolas J.; Brown, Michael J. I.; Jones, Heath

2015-02-01

We have determined K-band luminosity functions for 13,325 local universe galaxies as a function of morphology and color (for K {sub tot} ≤ 10.75). Our sample is drawn from the Two Micron All Sky Survey Extended Source Catalog, with all sample galaxies having measured morphologies and distances (including 4219 archival redshift-independent distances). The luminosity function for our total sample is in good agreement with previous works, but is relatively smooth at faint magnitudes (due to bulk flow distance corrections). We investigated the differences due to morphological and color selection using 5417 sample galaxies with NASA Sloan Atlas optical colors and find thatmore » red spirals comprise 20%-50% of all spirals with –25 ≤ M{sub K}  < –20. Fainter than M{sub K} = –24, red spirals are as common as early types, explaining the different faint end slopes (α = –0.87 and –1.00 for red and early-types, respectively). While we find red spirals comprise more than 50% of all M{sub K}  < –25 spiral galaxies, they do not dominate the bright end of the overall red galaxy luminosity function, which is dominated by early-type galaxies. The brightest red spirals have ongoing star formation and those without are frequently misclassified as early-types. The faintest ones have an appearance and Sérsic indices consistent with faded disks, rather than true bulge-dominated galaxies.« less

Submillimetre flux as a probe of molecular ISM mass in high-z galaxies

NASA Astrophysics Data System (ADS)

Liang, Lichen; Feldmann, Robert; Faucher-Giguère, Claude-André; Kereš, Dušan; Hopkins, Philip F.; Hayward, Christopher C.; Quataert, Eliot; Scoville, Nick Z.

2018-07-01

Recent long-wavelength observations on the thermal dust continuum suggest that the Rayleigh-Jeans tail can be used as a time-efficient quantitative probe of the dust and interstellar medium (ISM) mass in high-z galaxies. We use high-resolution cosmological simulations from the Feedback in Realistic Environment (FIRE) project to analyse the dust emission of M* ≳ 1010 M⊙ galaxies at z= 2-4. Our simulations (MASSIVEFIRE) explicitly include various forms of stellar feedback, and they produce the stellar masses and star formation rates of high-z galaxies in agreement with observations. Using radiative transfer modelling, we show that sub-millimetre (sub-mm) luminosity and molecular ISM mass are tightly correlated and that the overall normalization is in quantitative agreement with observations. Notably, sub-mm luminosity traces molecular ISM mass even during starburst episodes as dust mass and mass-weighted temperature evolve only moderately between z = 4 and z = 2, including during starbursts. Our finding supports the empirical approach of using broadband sub-mm flux as a proxy for molecular gas content in high-z galaxies. We thus expect single-band sub-mm observations with ALMA to dramatically increase the sample size of high-z galaxies with reliable ISM masses in the near future.

Submillimeter flux as a probe of molecular ISM mass in high-z galaxies

NASA Astrophysics Data System (ADS)

Liang, Lichen; Feldmann, Robert; Faucher-Giguère, Claude-André; Kereš, Dušan; Hopkins, Philip F.; Hayward, Christopher C.; Quataert, Eliot; Scoville, Nick Z.

2018-04-01

Recent long wavelength observations on the thermal dust continuum suggest that the Rayleigh-Jeans (RJ) tail can be used as a time-efficient quantitative probe of the dust and ISM mass in high-z galaxies. We use high-resolution cosmological simulations from the Feedback in Realistic Environment (FIRE) project to analyze the dust emission of M* ≳ 1010M⊙ galaxies at z = 2 - 4. Our simulations (MassiveFIRE) explicitly include various forms of stellar feedback, and they produce the stellar masses and star formation rates of high-z galaxies in agreement with observations. Using radiative transfer modelling, we show that sub-millimeter (sub-mm) luminosity and molecular ISM mass are tightly correlated and that the overall normalization is in quantitative agreement with observations. Notably, sub-mm luminosity traces molecular ISM mass even during starburst episodes as dust mass and mass-weighted temperature evolve only moderately between z = 4 and z = 2, including during starbursts. Our finding supports the empirical approach of using broadband sub-mm flux as a proxy for molecular gas content in high-z galaxies. We thus expect single-band sub-mm observations with ALMA to dramatically increase the sample size of high-z galaxies with reliable ISM masses in the near future.

An X-ray survey of variable radio bright quasars

NASA Technical Reports Server (NTRS)

Henriksen, M. J.; Marshall, F. E.; Mushotzky, R. F.

1984-01-01

A sample consisting primarily of radio bright quasars was observed in X-rays with the Einstein Observatory for times ranging from 1500 to 5000 seconds. Detected sources had luminosities ranging from 0.2 to 41.0 x 10 to the 45th power ergs/sec in the 0.5 to 4.5 keV band. Three of the fourteen objects which were reobserved showed flux increases greater than a factor of two on a time scale greater than six months. No variability was detected during the individual observations. The optical and X-ray luminosities are correlated, which suggests a common origin. However, the relationship (L sub x is approximately L sub op to the (.89 + or - .15)) found for historic radio variables may be significantly different than that reported for other radio bright sources. Some of the observed X-ray fluxes were substantially below the predicted self-Compton flux, assuming incoherent synchrotron emission and using VLBI results to constrain the size of the emission region, which suggests relativistic expansion in these sources. Normal CIV emission in two of the sources with an overpredicted Compton component suggests that although they, like BL Lac objects, have highly relativistic material apparently moving at small angle to the line of sight, they have a smaller fraction of the continuum component in the beam.

The hidden quasar nucleus of a WISE-selected, hyperluminous, dust-obscured galaxy at z ~ 2.3

NASA Astrophysics Data System (ADS)

Piconcelli, E.; Vignali, C.; Bianchi, S.; Zappacosta, L.; Fritz, J.; Lanzuisi, G.; Miniutti, G.; Bongiorno, A.; Feruglio, C.; Fiore, F.; Maiolino, R.

2015-02-01

We present the first X-ray spectrum of a hot dust-obscured galaxy (DOG), namely W1835+4355 at z ~ 2.3. Hot DOGs represent a very rare population of hyperluminous (≥1047 erg s-1), dust-enshrouded objects at z ≥ 2 recently discovered in the WISE All Sky Survey. The 40 ks XMM-Newton spectrum reveals a continuum as flat (Γ ~ 0.8) as typically seen in heavily obscured AGN. This, along with the presence of strong Fe Kα emission, clearly suggests a reflection-dominated spectrum due to Compton-thick absorption. In this scenario, the observed luminosity of L2-10~ 2 × 1044 erg s-1 is a fraction (<10%) of the intrinsic one, which is estimated to be ≳ 5 × 1045 erg s-1 by using several proxies. The Herschel data allow us to constrain the SED up to the sub-mm band, providing a reliable estimate of the quasar contribution (~75%) to the IR luminosity as well as the amount of star formation (~2100 M⊙ yr-1). Our results thus provide additional pieces of evidence that associate Hot DOGs with an exceptionally dusty phase during which luminous quasars and massive galaxies co-evolve and a very efficient and powerful AGN-driven feedback mechanism is predicted by models.

Origin of the X-ray Spectral Variation and Seemingly Broad Iron Line Strucuture in the Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Ebisawa, Ken; Naoki, Iso

2012-07-01

X-ray intensities and spectra of the Seyfert galaxies are known to be variable. Some of the sources have characteristic seemingly broad iron line structure, and their spectral variations are small in the iron line energy band. MCG-6-30-15 is such an archetypal source, and Miyakawa (2011) proposed a "Variable Partial Covering (VPC)" model to explain its continuum spectral variation, seemingly broad iron line structure, and small spectral variation in the iron energy band simultaneously, only due to variation of a single parameter. That single parameter is the "partial covering fraction" to describe the geometrical fraction of the X-ray emitting area covered by the ionized absorbers in the line of sight. The intrinsic X-ray luminosity is hardly variable in this model. We have applied the VPC model to the 27 Seyfert galaxies observed with Suzaku, and found that spectral variations of the 22 sources are successfully explained by this model only varying the partial covering fraction. Intrinsic X-ray luminosities of Seyfert galaxies are not variable, as opposed to what they apparently seem, and gravitationally red-shifted iron line is not necessary. Those ionized absorbing clouds are most likely to be Broad Line Region (BLR) clouds, and we will be able to constrain the BLR structure from X-ray observations.

Properties of Spectrally Defined Red QSOs at z = 0.3–1.2

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

Tsai, A.-L.; Hwang, C.-Y., E-mail: altsai@astro.ncu.edu.tw, E-mail: hwangcy@astro.ncu.edu.tw

We investigated the properties of a sample of red Quasi-stellar Objects (QSOs) using optical, radio, and infrared data. These QSOs were selected from the Sloan Digital Sky Survey Data Release 7 quasar catalog. We only selected sources with sky coverage in the Very Large Array Faint Images of the Radio Sky at Twenty-centimeters survey, and searched for sources with Wide-field Infrared Survey Explorer counterparts. We defined the spectral color of the QSOs based on the flux ratio of the rest-frame 4000 to 3000 Å continuum emission to select red QSOs and typical QSOs. In accordance with this criterion, only QSOsmore » with redshifts between 0.3 and 1.2 could be selected. We found that red QSOs have stronger infrared emission than typical QSOs. We noted that the number ratios of red QSOs to typical QSOs decrease with increasing redshifts, although the number of typical QSOs increase with redshifts. Furthermore, at high redshifts, the luminosity distributions of typical QSOs and red QSOs seem to have similar peaks; however, at low redshifts, the luminosities of red QSOs seem to be lower than those of typical QSOs. These findings suggest that there might be at least two types of red QSOs in our QSO samples.« less

Photoionisation modelling of the broad line region

NASA Astrophysics Data System (ADS)

King, Anthea

2016-08-01

Two of the most fundamental questions regarding the broad line region (BLR) are "what is its structure?" and "how is it moving?" Baldwin et al. (1995) showed that by summing over an ensemble of clouds at differing densities and distances from the ionising source we can easily and naturally produce a spectrum similar to what is observed for AGN. This approach is called the `locally optimally emitting clouds' (LOC) model. This approach can also explain the well-observed stratification of emission lines in the BLR (e.g. Clavel et al. 1991, Peterson et al. 1991, Kollatschny et al. 2001) and `breathing' of BLR with changes in the continuum luminosity (Netzer & Mor 1990, Peterson et al. 2014) and is therefore a generally accepted model of the BLR. However, LOC predictions require some assumptions to be made about the distribution of the clouds within the BLR. By comparing photoionization predictions, for a distribution of cloud properties, with observed spectra we can infer something about the structure of the BLR and distribution of clouds. I use existing reverberation mapping data to constrain the structure of the BLR by observing how individual line strengths and ratios of different lines change in high and low luminosity states. I will present my initial constraints and discuss the challenges associated with the method.

POX 52: A Dwarf Seyfert 1 Galaxy with an Intermediate-Mass Black Hole

NASA Astrophysics Data System (ADS)

Barth, Aaron J.; Ho, Luis C.; Rutledge, Robert E.; Sargent, Wallace L. W.

2004-05-01

We describe new optical images and spectra of POX 52, a dwarf galaxy with an active nucleus that was originally detected in the POX objective-prism survey. While POX 52 was originally thought to be a Seyfert 2 galaxy, the new data reveal an emission-line spectrum very similar to that of the dwarf Seyfert 1 galaxy NGC 4395, with broad components to the permitted line profiles, and we classify POX 52 as a Seyfert 1 galaxy. The host galaxy appears to be a dwarf elliptical, and its brightness profile is best fit by a Sérsic model with an index of 3.6+/-0.2 and a total magnitude of MV=-17.6. Applying mass-luminosity-line width scaling relations to estimate the black hole mass from the broad Hβ line width and nonstellar continuum luminosity, we find MBH~1.6×105Msolar. The stellar velocity dispersion in the host galaxy, measured from the Ca II λ8498, 8542 lines, is 36+/-5 km s-1, also suggestive of a black hole mass of order 105Msolar. Further searches for active nuclei in dwarf galaxies can provide unique constraints on the demographics of black holes in the mass range below 106Msolar.

Swift and SALT observations of the multiple outbursts of MAXI J1957+032

NASA Astrophysics Data System (ADS)

Mata Sánchez, D.; Charles, P. A.; Armas Padilla, M.; Buckley, D. A. H.; Israel, G. L.; Linares, M.; Muñoz-Darias, T.

2017-06-01

The new recurrent X-ray transient MAXI J1957+032 has had four X-ray outbursts within 16 months, all very briefly detected (lasting <5 d). During the most recent event (2016 September/October), we obtained with the Southern African Large Telescope the first optical spectrum of the transient counterpart, showing the classic blue continuum of an X-ray irradiated disc in an LMXB and no other features. At high Galactic latitude below the plane (-13°) reddening is low but there is no quiescent counterpart visible on any of the existing sky surveys, nor any other known X-ray source in the region. Swift monitoring of three of the four events is presented, showing rapidly fading X-ray outbursts together with significant UVOT detections in the UV (W1,M2,W2), U and B bands. The optical properties are most like those of the short-period LMXBs, which, combined with the softening witnessed during the decay to quiescence would place the system at d < 13 kpc. The short duration and short recurrence time of the outbursts are reminiscent of the accreting millisecond X-ray pulsars, which exhibit peak luminosities of ˜ 1 per cent LEdd. Assuming this peak luminosity would place MAXI J1957+032 at a distance of d ˜ 5-6 kpc.

Measurements of Cyclotron Features and Pulse Periods in the High-Mass X-Ray Binaries 4U 1538-522 and 4U 1907+09 with the International Gamma-Ray Astrophysics Laboratory

NASA Technical Reports Server (NTRS)

Hemphill, Paul B.; Rothschild, Richard E.; Caballero, Isabel; Pottschmidt, Katja; Kuhnel, Matthias; Furst, Felix; Wilms, Jorn

2013-01-01

We present a spectral and timing analysis of International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of two high-mass X-ray binaries, 4U 1538-522 and 4U 1907+09. Our timing measurements for 4U 1538-522 find the pulse period to have exhibited a spin-up trend until approximately 2009, after which there is evidence for a torque reversal, with the source beginning to spin down to the most recently measured period of 525.407 plus or minus 0.001 seconds. The most recent INTEGRAL observations of 4U 1907+09 are not found to yield statistically significant pulse periods due to the significantly lower flux from the source compared with 4U 1538-522. A spectral model consisting of a power-law continuum with an exponential cutoff and modified by two cyclotron resonance scattering features is found to fit both sources well, with the cyclotron scattering features detected at approximately 22 and approximately 49 kiloelectronvolts for 4U 1538-522 and at approximately 18 and approximately 36 kiloelectronvolts for 4U 1907+09. The spectral parameters of 4U 1538-522 are generally not found to vary significantly with flux and there is little to no variation across the torque reversal. Examining our results in conjunction with previous work, we find no evidence for a correlation between cyclotron line energy and luminosity for 4U 1538-522. 4U 1907+09 shows evidence for a positive correlation between cyclotron line energy and luminosity, which would make it the fourth, and lowest luminosity, cyclotron line source to exhibit this relationship.

MEASUREMENTS OF CYCLOTRON FEATURES AND PULSE PERIODS IN THE HIGH-MASS X-RAY BINARIES 4U 1538–522 AND 4U 1907+09 WITH THE INTERNATIONAL GAMMA-RAY ASTROPHYSICS LABORATORY

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

Hemphill, Paul B.; Rothschild, Richard E.; Caballero, Isabel

We present a spectral and timing analysis of International Gamma-Ray Astrophysics Laboratory (INTEGRAL) observations of two high-mass X-ray binaries, 4U 1538–522 and 4U 1907+09. Our timing measurements for 4U 1538–522 find the pulse period to have exhibited a spin-up trend until approximately 2009, after which there is evidence for a torque reversal, with the source beginning to spin down to the most recently measured period of 525.407 ± 0.001 s. The most recent INTEGRAL observations of 4U 1907+09 are not found to yield statistically significant pulse periods due to the significantly lower flux from the source compared with 4U 1538–522.more » A spectral model consisting of a power-law continuum with an exponential cutoff and modified by two cyclotron resonance scattering features is found to fit both sources well, with the cyclotron scattering features detected at ∼22 and ∼49 keV for 4U 1538–522 and at ∼18 and ∼36 keV for 4U 1907+09. The spectral parameters of 4U 1538–522 are generally not found to vary significantly with flux and there is little to no variation across the torque reversal. Examining our results in conjunction with previous work, we find no evidence for a correlation between cyclotron line energy and luminosity for 4U 1538–522. 4U 1907+09 shows evidence for a positive correlation between cyclotron line energy and luminosity, which would make it the fourth, and lowest luminosity, cyclotron line source to exhibit this relationship.« less

EVIDENCE FOR A WIDE RANGE OF ULTRAVIOLET OBSCURATION IN z {approx} 2 DUSTY GALAXIES FROM THE GOODS-HERSCHEL SURVEY

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

Penner, Kyle; Dickinson, Mark; Dey, Arjun

Dusty galaxies at z {approx} 2 span a wide range of relative brightness between rest-frame mid-infrared (8 {mu}m) and ultraviolet wavelengths. We attempt to determine the physical mechanism responsible for this diversity. Dust-obscured galaxies (DOGs), which have rest-frame mid-IR to UV flux density ratios {approx}> 1000, might be abnormally bright in the mid-IR, perhaps due to prominent emission from active galactic nuclei and/or polycyclic aromatic hydrocarbons, or abnormally faint in the UV. We use far-infrared data from the GOODS-Herschel survey to show that most DOGs with 10{sup 12} L {sub Sun} {approx}< L {sub IR} {approx}< 10{sup 13} L {submore » Sun} are not abnormally bright in the mid-IR when compared to other dusty galaxies with similar IR (8-1000 {mu}m) luminosities. We observe a relation between the median IR to UV luminosity ratios and the median UV continuum power-law indices for these galaxies, and we find that only 24% have specific star formation rates that indicate the dominance of compact star-forming regions. This circumstantial evidence supports the idea that the UV- and IR-emitting regions in these galaxies are spatially coincident, which implies a connection between the abnormal UV faintness of DOGs and dust obscuration. We conclude that the range in rest-frame mid-IR to UV flux density ratios spanned by dusty galaxies at z {approx} 2 is due to differing amounts of UV obscuration. Of galaxies with these IR luminosities, DOGs are the most obscured. We attribute differences in UV obscuration to either (1) differences in the degree of alignment between the spatial distributions of dust and massive stars or (2) differences in the total dust content.« less

A Detached Protostellar Disk around a ˜0.2 M ⊙ Protostar in a Possible Site of a Multiple Star Formation in a Dynamical Environment in Taurus

NASA Astrophysics Data System (ADS)

Tokuda, Kazuki; Onishi, Toshikazu; Saigo, Kazuya; Hosokawa, Takashi; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro; Machida, Masahiro N.; Tomida, Kengo; Kunitomo, Masanobu; Kawamura, Akiko; Fukui, Yasuo; Tachihara, Kengo

2017-11-01

We report ALMA observations in 0.87 mm continuum and 12CO (J = 3-2) toward a very low-luminosity (<0.1 L ⊙) protostar, which is deeply embedded in one of the densest cores, MC27/L1521F, in Taurus with an indication of multiple star formation in a highly dynamical environment. The beam size corresponds to ˜20 au, and we have clearly detected blueshifted/redshifted gas in 12CO associated with the protostar. The spatial/velocity distributions of the gas show there is a rotating disk with a size scale of ˜10 au, a disk mass of ˜10-4 M ⊙, and a central stellar mass of ˜0.2 M ⊙. The observed disk seems to be detached from the surrounding dense gas, although it is still embedded at the center of the core whose density is ˜106 cm-3. The current low-outflow activity and the very low luminosity indicate that the mass accretion rate onto the protostar is extremely low in spite of a very early stage of star formation. We may be witnessing the final stage of the formation of ˜0.2 M ⊙ protostar. However, we cannot explain the observed low luminosity with the standard pre-main-sequence evolutionary track unless we assume cold accretion with an extremely small initial radius of the protostar (˜0.65 {R}⊙ ). These facts may challenge our current understanding of the low mass star formation, in particular the mass accretion process onto the protostar and the circumstellar disk.

Six months of multiwavelength follow-up of the tidal disruption candidate ASASSN-14li and implied TDE rates from ASAS-SN

DOE PAGES

Holoien, Thomas W. -S.; Kochanek, C. S.; Prieto, J. L.; ...

2015-11-25

In this paper, we present ground-based and Swift photometric and spectroscopic observations of the candidate tidal disruption event (TDE) ASASSN-14li, found at the centre of PGC 043234 (d ≃ 90 Mpc) by the All-Sky Automated Survey for SuperNovae (ASAS-SN). The source had a peak bolometric luminosity of L ≃ 10 44 erg s -1 and a total integrated energy of E ≃ 7 × 10 50 erg radiated over the ~6 months of observations presented. The UV/optical emission of the source is well fitted by a blackbody with roughly constant temperature of T ~ 35 000 K, while the luminositymore » declines by roughly a factor of 16 over this time. The optical/UV luminosity decline is broadly consistent with an exponential decline, L∝e -t/t0, with t 0 ≃ 60 d. ASASSN-14li also exhibits soft X-ray emission comparable in luminosity to the optical and UV emission but declining at a slower rate, and the X-ray emission now dominates. Spectra of the source show broad Balmer and helium lines in emission as well as strong blue continuum emission at all epochs. Finally, we use the discoveries of ASASSN-14li and ASASSN-14ae to estimate the TDE rate implied by ASAS-SN, finding an average rate of r ≃ 4.1 × 10 -5 yr -1 per galaxy with a 90 per cent confidence interval of (2.2–17.0) × 10 -5 yr -1 per galaxy. ASAS-SN found roughly 1 TDE for every 70 Type Ia supernovae in 2014, a rate that is much higher than that of other surveys.« less

Nustar Reveals an Intrinsically X-ray Weak Broad Absorption Line Quasar in the Ultraluminous Infrared Galaxy Markarian 231

NASA Technical Reports Server (NTRS)

Teng, Stacy H.; Brandt. W. N.; Harrison, F. A.; Luo, B.; Alexander, D. M.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W.;

No Sign of Strong Molecular Gas Outflow in an Infrared-bright Dust-obscured Galaxy with Strong Ionized-gas Outflow

NASA Astrophysics Data System (ADS)

Toba, Yoshiki; Komugi, Shinya; Nagao, Tohru; Yamashita, Takuji; Wang, Wei-Hao; Imanishi, Masatoshi; Sun, Ai-Lei

2017-12-01

We report the discovery of an infrared (IR)-bright dust-obscured galaxy (DOG) that shows a strong ionized-gas outflow but no significant molecular gas outflow. Based on detailed analysis of their optical spectra, we found some peculiar IR-bright DOGs that show strong ionized-gas outflow ([O III] λ5007) from the central active galactic nucleus (AGN). For one of these DOGs (WISE J102905.90+050132.4) at z spec = 0.493, we performed follow-up observations using ALMA to investigate their CO molecular gas properties. As a result, we successfully detected 12CO(J = 2–1) and 12CO(J = 4–3) lines and the continuum of this DOG. The intensity-weighted velocity map of both lines shows a gradient, and the line profile of those CO lines is well-fitted by a single narrow Gaussian, meaning that this DOG has no sign of strong molecular gas outflow. The IR luminosity of this object is log (L IR/L ⊙) = 12.40, which is classified as an ultraluminous IR galaxy (ULIRG). We found that (i) the stellar mass and star formation rate relation and (ii) the CO luminosity and far-IR luminosity relation are consistent with those of typical ULIRGs at similar redshifts. These results indicate that the molecular gas properties of this DOG are normal despite the fact that its optical spectrum shows a powerful AGN outflow. We conclude that a powerful ionized-gas outflow caused by the AGN does not necessarily affect the cold interstellar medium in the host galaxy, at least for this DOG.

A search for changing look quasars in second epoch imaging

NASA Astrophysics Data System (ADS)

Findlay, Joseph; Myers, Adam; McGreer, Ian

2018-01-01

Over nearly two decades, the Sloan Digital Sky Survey has compiled a catalog of over half a million confirmed quasars. During that period approximately ten percent of these objects have been spectroscopically observed in two or more epochs over baselines of ten or more years. This led recently to the discovery of the largest change in luminosity ever before observed in a quasar. The dimming emission was a reflection of very significant changes in continuum and broad line properties, the source had effectively transitioned from a Type I quasar to a Type II AGN. Since then several more "changing look" quasars have been discovered in multi-epoch SDSS spectroscopy. Among them are objects with rising and falling luminosities, appearing and disappearing broad lines. The origin of this behavior is still very uncertain, currently favored is the scenario in which an accreting black hole is simply starved of fuel. Other plausible scenarios include flaring due to stellar tidal disruption close to the black hole or large changes in accretion flow, which can occur during transitions between radiatively efficient and inefficient accretion regimes. Monitoring of larger numbers of changing look quasars will help to elucidate these ideas.In this poster, we report on the progress of a pilot study in which we hope to learn how to select changing look quasars in multi-epoch imaging. This will allow us to take advantage of the entire SDSS quasar catalog rather than just the ten percent of objects with multi-epoch spectroscopy. Comparing archival SDSS and more recent Legacy Survey imaging over ten-year baselines we select objects whose photometry is consistent with the large changes in luminosity expected in changing look quasars. We aim to build up a catalog of both transitioned and transitioning objects for future monitoring.

HERUS: A CO ATLAS FROM SPIRE SPECTROSCOPY OF LOCAL ULIRGs

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

Pearson, Chris; Rigopoulou, Dimitra; Hurley, Peter

We present the Herschel SPIRE Fourier Transform Spectroscopy (FTS) atlas for a complete flux-limited sample of local ultraluminous infrared galaxies (ULIRGs) as part of the HERschel Ultra Luminous InfraRed Galaxy Survey (HERUS). The data reduction is described in detail and was optimized for faint FTS sources ,with particular care being taken for the subtraction of the background, which dominates the continuum shape of the spectra. To improve the final spectra, special treatment in the data reduction has been given to any observation suffering from artifacts in the data caused by anomalous instrumental effects. Complete spectra are shown covering 200–671 μmore » m, with photometry in the SPIRE bands at 250, 350, and 500 μ m. The spectra include near complete CO ladders for over half of our sample, as well as fine structure lines from [C i] 370 μ m, [C i] 609 μ m, and [N ii] 205 μ m. We also detect H{sub 2}O lines in several objects. We construct CO spectral line energy distributions (SLEDs) for the sample, and compare their slopes with the far-infrared (FIR) colors and luminosities. We show that the CO SLEDs of ULIRGs can be broadly grouped into three classes based on their excitation. We find that the mid- J (5 <  J  < 8) lines are better correlated with the total FIR luminosity, suggesting that the warm gas component is closely linked to recent star formation. The higher J transitions do not linearly correlate with the FIR luminosity, consistent with them originating in hotter, denser gas that is unconnected to the current star formation. We conclude that in most cases more than one temperature component is required to model the CO SLEDs.« less

ASASSN-15oi: a rapidly evolving, luminous tidal disruption event at 216 Mpc

NASA Astrophysics Data System (ADS)

Holoien, T. W.-S.; Kochanek, C. S.; Prieto, J. L.; Grupe, D.; Chen, Ping; Godoy-Rivera, D.; Stanek, K. Z.; Shappee, B. J.; Dong, Subo; Brown, J. S.; Basu, U.; Beacom, J. F.; Bersier, D.; Brimacombe, J.; Carlson, E. K.; Falco, E.; Johnston, E.; Madore, B. F.; Pojmanski, G.; Seibert, M.

2016-12-01

We present ground-based and Swift photometric and spectroscopic observations of the tidal disruption event (TDE) ASASSN-15oi, discovered at the centre of 2MASX J20390918-3045201 (d ≃ 216 Mpc) by the All-Sky Automated Survey for SuperNovae. The source peaked at a bolometric luminosity of L ≃ 1.3 × 1044 erg s-1 and radiated a total energy of E ≃ 6.6 × 1050 erg over the first ˜3.5 months of observations. The early optical/UV emission of the source can be fit by a blackbody with temperature increasing from T ˜ 2 × 104 K to T ˜ 4 × 104 K while the luminosity declines from L ≃ 1.3 × 1044 erg s-1 to L ≃ 2.3 × 1043 erg s-1, requiring the photosphere to be shrinking rapidly. The optical/UV luminosity decline during this period is most consistent with an exponential decline, L∝ e^{-(t-t_0)/τ}, with τ ≃ 46.5 d for t0 ≃ 57241.6 (MJD), while a power-law decline of L ∝ (t - t0)-α with t0 ≃ 57 212.3 and α = 1.62 provides a moderately worse fit. ASASSN-15oi also exhibits roughly constant soft X-ray emission that is significantly weaker than the optical/UV emission. Spectra of the source show broad helium emission lines and strong blue continuum emission in early epochs, although these features fade rapidly and are not present ˜3 months after discovery. The early spectroscopic features and colour evolution of ASASSN-15oi are consistent with a TDE, but the rapid spectral evolution is unique among optically selected TDEs.

Short gamma-ray bursts at the dawn of the gravitational wave era

NASA Astrophysics Data System (ADS)

Ghirlanda, G.; Salafia, O. S.; Pescalli, A.; Ghisellini, G.; Salvaterra, R.; Chassande-Mottin, E.; Colpi, M.; Nappo, F.; D'Avanzo, P.; Melandri, A.; Bernardini, M. G.; Branchesi, M.; Campana, S.; Ciolfi, R.; Covino, S.; Götz, D.; Vergani, S. D.; Zennaro, M.; Tagliaferri, G.

2016-10-01

We derive the luminosity function φ(L) and redshift distribution Ψ(z) of short gamma-ray bursts (SGRBs) using all the available observer-frame constraints (I.e. peak flux, fluence, peak energy and duration distributions) of the large population of Fermi SGRBs and the rest-frame properties of a complete sample of SGRBs detected by Swift. We show that a steep φ(L) ∝ L- α with α ≥ 2.0 is excluded if the full set of constraints is considered. We implement a Markov chain Monte Carlo method to derive the φ(L) and Ψ(z) functions assuming intrinsic Ep-Liso and Ep-Eiso correlations to hold or, alternatively, that the distributions of intrinsic peak energy, luminosity, and duration are independent. To make our results independent from assumptions on the progenitor (NS-NS binary mergers or other channels) and from uncertainties on the star formation history, we assume a parametric form for the redshift distribution of the population of SGRBs. We find that a relatively flat luminosity function with slope ~0.5 below a characteristic break luminosity ~3 × 1052 erg s-1 and a redshift distribution of SGRBs peaking at z ~ 1.5-2 satisfy all our constraints. These results also hold if no Ep-Liso and Ep-Eiso correlations are assumed and they do not depend on the choice of the minimum luminosity of the SGRB population. We estimate, within ~200 Mpc (I.e. the design aLIGO range for the detection of gravitational waves produced by NS-NS merger events), that there should be 0.007-0.03 SGRBs yr-1 detectable as γ-ray events. Assuming current estimates of NS-NS merger rates and that all NS-NS mergers lead to a SGRB event, we derive a conservative estimate of the average opening angle of SGRBs ⟨ θjet ⟩ ~ 3°-6°. The luminosity function implies a prompt emission average luminosity ⟨L⟩ ~ 1.5 × 1052 erg s-1, higher by nearly two orders of magnitude than previous findings in the literature, which greatly enhances the chance of observing SGRB "orphan" afterglows. Effort should go in the direction of finding and identifying such orphan afterglows as counterparts of GW events.

Reverberation Mapping of AGN Accretion Disks

NASA Astrophysics Data System (ADS)

Fausnaugh, Michael; AGN STORM Collaboration

2017-01-01

I will discuss new reverberation mapping results that allow us to investigate the temperature structure of AGN accretion disks. By measuring time-delays between broad-band continuum light curves, we can determine the size of the disk as a function of wavelength. I will discuss the detection of continuum lags in NGC 5548 reported by the AGN STORM project and implications for the accretion disk. I will also present evidence for continuum lags in two other AGN for which we recently measured black hole masses from continuum-Hbeta reverberations. The mass measurements allow us to compare the continuum lags to predictions from standard thin disk theory, and our results indicate that the accretion disks are larger than the simplest expectations.

A Model for Protostellar Cluster Luminosities and the Impact on the CO–H2 Conversion Factor

NASA Astrophysics Data System (ADS)

Gaches, Brandt A. L.; Offner, Stella S. R.

2018-02-01

We construct a semianalytic model to study the effect of far-ultraviolet (FUV) radiation on gas chemistry from embedded protostars. We use the protostellar luminosity function (PLF) formalism of Offner & McKee to calculate the total, FUV, and ionizing cluster luminosity for various protostellar accretion histories and cluster sizes. We2 compare the model predictions with surveys of Gould Belt star-forming regions and find that the tapered turbulent core model matches best the mean luminosities and the spread in the data. We combine the cluster model with the photodissociation region astrochemistry code, 3D-PDR, to compute the impact of the FUV luminosity from embedded protostars on the CO-to-H2 conversion factor, X CO, as a function of cluster size, gas mass, and star formation efficiency. We find that X CO has a weak dependence on the FUV radiation from embedded sources for large clusters owing to high cloud optical depths. In smaller and more efficient clusters the embedded FUV increases X CO to levels consistent with the average Milky Way values. The internal physical and chemical structures of the cloud are significantly altered, and X CO depends strongly on the protostellar cluster mass for small efficient clouds.

Statistical Model of Dynamic Markers of the Alzheimer's Pathological Cascade.

PubMed

Balsis, Steve; Geraci, Lisa; Benge, Jared; Lowe, Deborah A; Choudhury, Tabina K; Tirso, Robert; Doody, Rachelle S

2018-05-05

Alzheimer's disease (AD) is a progressive disease reflected in markers across assessment modalities, including neuroimaging, cognitive testing, and evaluation of adaptive function. Identifying a single continuum of decline across assessment modalities in a single sample is statistically challenging because of the multivariate nature of the data. To address this challenge, we implemented advanced statistical analyses designed specifically to model complex data across a single continuum. We analyzed data from the Alzheimer's Disease Neuroimaging Initiative (ADNI; N = 1,056), focusing on indicators from the assessments of magnetic resonance imaging (MRI) volume, fluorodeoxyglucose positron emission tomography (FDG-PET) metabolic activity, cognitive performance, and adaptive function. Item response theory was used to identify the continuum of decline. Then, through a process of statistical scaling, indicators across all modalities were linked to that continuum and analyzed. Findings revealed that measures of MRI volume, FDG-PET metabolic activity, and adaptive function added measurement precision beyond that provided by cognitive measures, particularly in the relatively mild range of disease severity. More specifically, MRI volume, and FDG-PET metabolic activity become compromised in the very mild range of severity, followed by cognitive performance and finally adaptive function. Our statistically derived models of the AD pathological cascade are consistent with existing theoretical models.

Planetary nebulae as standard candles. IV - A test in the Leo I group

NASA Technical Reports Server (NTRS)

Ciardullo, Robin; Jacoby, George H.; Ford, Holland C.

1989-01-01

In this paper, PN are used to determine accurate distances to three galaxies in the Leo I group - The E0 giant elliptical NGC 3379, its optical companion, the SB0 spiral NGC 3384, and the smaller E6 elliptical NGC 3377. In all three galaxies, the luminosity-specific PN number densities are roughly the same, and the derived stellar death rates are in remarkable agreement with the predictions of stellar evolution theory. It is shown that the shape of the forbidden O III 5007 A PN luminosity function is the same in each galaxy and indistinguishable from that observed in M31 and M81. It is concluded that the PN luminosity function is an excellent standard candle for early-type galaxies.

Accelerated evolution of the Lyα luminosity function at z ≳ 7 revealed by the Subaru ultra-deep survey for Lyα emitters at z = 7.3

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

Konno, Akira; Ouchi, Masami; Ono, Yoshiaki

2014-12-10

We present the ultra-deep Subaru narrowband imaging survey for Lyα emitters (LAEs) at z = 7.3 in the Subaru/XMM-Newton Deep Survey (SXDS) and Cosmic Evolution Survey (COSMOS) fields (∼0.5 deg{sup 2}) with a total integration time of 106 hr. Exploiting our new sharp bandwidth filter, NB101, installed on the Suprime-Cam, we have reached L(Lyα) = 2.4 × 10{sup 42} erg s{sup –1} (5σ) for z = 7.3 LAEs, about four times deeper than previous Subaru z ≳ 7 studies, which allows us to reliably investigate the evolution of the Lyα luminosity function (LF) for the first time down to themore » luminosity limit same as those of Subaru z = 3.1-6.6 LAE samples. Surprisingly, we only find three and four LAEs in the SXDS and COSMOS fields, respectively, while one expects a total of ∼65 LAEs by our survey in the case of no Lyα LF evolution from z = 6.6 to 7.3. We identify a decrease of the Lyα LF from z = 6.6 to 7.3 at the >90% confidence level from our z = 7.3 Lyα LF with the best-fit Schechter parameters of L{sub Lyα}{sup ∗}=2.7{sub −1.2}{sup +8.0}×10{sup 42} erg s{sup −1} and ϕ{sup ∗}=3.7{sub −3.3}{sup +17.6}×10{sup −4} Mpc{sup −3} for a fixed α = –1.5. Moreover, the evolution of the Lyα LF is clearly accelerated at z > 6.6 beyond the measurement uncertainties including cosmic variance. Because no such accelerated evolution of the UV-continuum LF or the cosmic star formation rate (SFR) is found at z ∼ 7, but suggested only at z > 8, this accelerated Lyα LF evolution is explained by physical mechanisms different from a pure SFR decrease but related to the Lyα production and escape in the process of cosmic reionization. Because a simple accelerating increase of intergalactic medium neutral hydrogen absorbing Lyα cannot be reconciled with Thomson scattering of optical depth measurements from WMAP and Planck, our findings may support new physical pictures suggested by recent theoretical studies, such as the existence of HI clumpy clouds within cosmic ionized bubbles that are selectively absorbing Lyα and the large ionizing photon escape fraction of galaxies causing weak Lyα emission.« less

Quantum mechanical/molecular mechanical/continuum style solvation model: time-dependent density functional theory.

PubMed

Thellamurege, Nandun M; Cui, Fengchao; Li, Hui

2013-08-28

A combined quantum mechanical/molecular mechanical/continuum (QM/MMpol/C) style method is developed for time-dependent density functional theory (TDDFT, including long-range corrected TDDFT) method, induced dipole polarizable force field, and induced surface charge continuum model. Induced dipoles and induced charges are included in the TDDFT equations to solve for the transition energies, relaxed density, and transition density. Analytic gradient is derived and implemented for geometry optimization and molecular dynamics simulation. QM/MMpol/C style DFT and TDDFT methods are used to study the hydrogen bonding of the photoactive yellow protein chromopore in ground state and excited state.

Confirmation of a Steep Luminosity Function for Ly alpha Emitters at z 5.7: a Major Component of Reionization

NASA Technical Reports Server (NTRS)

Dressler, Alan; Henry, Alaina L.; Martin, Crystal L.; Sawicki, Marcin; McCarthy, Patrick; Villaneuva, Edward

2014-01-01

We report the first direct and robust measurement of the faint-end slope of the Ly-alpha emitter (LAE) luminosity function at z = 5.7. Candidate LAEs from a low-spectral-resolution blind search with IMACS on Magellan- Baade were targeted at higher resolution to distinguish high redshift LAEs from foreground galaxies. All but 2 of our 42 single-emission-line systems are fainter than F = 2.0×10(exp-17) ergs s(exp-1) cm(exp-2), making these the faintest emission-lines observed for a z = 5.7 sample with known completeness, an essential property for determining the faint end slope of the LAE luminosity function. We find 13 LAEs as compared to 29 foreground galaxies, in very good agreement with the modeled foreground counts predicted in Dressler et al. (2011a) that had been used to estimate a faint-end slope of alpha = -2.0 for the LAE luminosity function. A 32% LAE fraction, LAE/(LAE+foreground) within the flux interval F = 2-20 × 10(exp-18) ergs s(exp-1) cm(exp-2) constrains the faint end slope of the luminosity function to -1.95 greater than alpha greater than -2.35 (1 delta). We show how this steep LF should provide, to the limit of our observations, more than 20% of the flux necessary to maintain ionization at z = 5.7, with a factor-of-ten extrapolation in flux reaching more than 55%. We suggest that this bodes well for a comparable contribution by similar, low-mass star forming galaxies at higher-redshift - within the reionization epoch at z greater than approximately 7, only 250 Myr earlier - and that such systems provide a substantial, if not dominant, contribution to the late-stage reionization of the IGM.

A New Determination of the Luminosity Function of the Galactic Halo.

NASA Astrophysics Data System (ADS)

Dawson, Peter Charles

The luminosity function of the galactic halo is determined by subtracting from the observed numbers of proper motion stars in the LHS Catalogue the expected numbers of main-sequence, degenerate, and giant stars of the disk population. Selection effects are accounted for by Monte Carlo simulations based upon realistic colour-luminosity relations and kinematic models. The catalogue is shown to be highly complete, and a calibration of the magnitude estimates therein is presented. It is found that, locally, the ratio of disk to halo material is close to 950, and that the mass density in main sequence and subgiant halo stars with 3 < M(,v) < 14 is about 2 x 10('-5) M(,o) pc('-3). With due allowance for white dwarfs and binaries, and taking into account the possibility of a moderate rate of halo rotation, it is argued that the total density does not much exceed 5 x 10('-5) M(,o) pc('-3), in which case the total mass interior to the sun is of the order of 5 x 10('8) M(,o) for a density distribution which projects to a de Vaucouleurs r(' 1/4) law. It is demonstrated that if the Wielen luminosity function is a faithful representation of the stellar distribution in the solar neighbourhood, then the observed numbers of large proper motion stars are inconsistent with the presence of an intermediate popula- tion at the level, and with the kinematics advocated recently by Gilmore and Reid. The initial mass function (IMF) of the halo is considered, and weak evidence is presented that its slope is at least not shallower than that of the disk population IMF. A crude estimate of the halo's age, based on a comparison of the main sequence turnoff in the reduced proper motion diagram with theoretical models is obtained; a tentative lower limit is 15 Gyr with a best estimate of between 15 and 18 Gyr. Finally, the luminosity function obtained here is compared with those determined in other investigations.

The significance of turbulent flow representation in single-continuum models

USGS Publications Warehouse

Reimann, T.; Rehrl, C.; Shoemaker, W.B.; Geyer, T.; Birk, S.

2011-01-01

Karst aquifers exhibit highly conductive features caused from rock dissolution processes. Flow within these structures can become turbulent and therefore can be expressed by nonlinear gradient functions. One way to account for these effects is by coupling a continuum model with a conduit network. Alternatively, turbulent flow can be considered by adapting the hydraulic conductivity within the continuum model. Consequently, the significance of turbulent flow on the dynamic behavior of karst springs is investigated by an enhanced single-continuum model that results in conduit-type flow in continuum cells (CTFC). The single-continuum approach CTFC represents laminar and turbulent flow as well as more complex hybrid models that require additional programming and numerical efforts. A parameter study is conducted to investigate the effects of turbulent flow on the response of karst springs to recharge events using the new CTFC approach, existing hybrid models, and MODFLOW-2005. Results reflect the importance of representing (1) turbulent flow in karst conduits and (2) the exchange between conduits and continuum cells. More specifically, laminar models overestimate maximum spring discharge and underestimate hydraulic gradients within the conduit. It follows that aquifer properties inferred from spring hydrographs are potentially impaired by ignoring flow effects due to turbulence. The exchange factor used for hybrid models is necessary to account for the scale dependency between hydraulic properties of the matrix continuum and conduits. This functionality, which is not included in CTFC, can be mimicked by appropriate use of the Horizontal Flow Barrier package for MODFLOW. Copyright 2011 by the American Geophysical Union.

The LOFAR window on star-forming galaxies and AGNs - curved radio SEDs and IR-radio correlation at 0

NASA Astrophysics Data System (ADS)

Calistro Rivera, G.; Williams, W. L.; Hardcastle, M. J.; Duncan, K.; Röttgering, H. J. A.; Best, P. N.; Brüggen, M.; Chyży, K. T.; Conselice, C. J.; de Gasperin, F.; Engels, D.; Gürkan, G.; Intema, H. T.; Jarvis, M. J.; Mahony, E. K.; Miley, G. K.; Morabito, L. K.; Prandoni, I.; Sabater, J.; Smith, D. J. B.; Tasse, C.; van der Werf, P. P.; White, G. J.

2017-08-01

We present a study of the low-frequency radio properties of star-forming (SF) galaxies and active galactic nuclei (AGNs) up to redshift z = 2.5. The new spectral window probed by the Low Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of 1542 galaxies in ˜ 7 deg2 of the LOFAR Boötes field. Using the extensive multiwavelength data set available in Boötes and detailed modelling of the far-infrared to ultraviolet spectral energy distribution (SED), we are able to separate the star formation (N = 758) and the AGN (N = 784) dominated populations. We study the shape of the radio SEDs and their evolution across cosmic time and find significant differences in the spectral curvature between the SF galaxy and AGN populations. While the radio spectra of SF galaxies exhibit a weak but statistically significant flattening, AGN SEDs show a clear trend to become steeper towards lower frequencies. No evolution of the spectral curvature as a function of redshift is found for SF galaxies or AGNs. We investigate the redshift evolution of the infrared-radio correlation for SF galaxies and find that the ratio of total infrared to 1.4-GHz radio luminosities decreases with increasing redshift: q1.4 GHz = (2.45 ± 0.04) (1 + z)-0.15 ± 0.03. Similarly, q150 MHz shows a redshift evolution following q150 GHz = (1.72 ± 0.04) (1 + z)-0.22 ± 0.05. Calibration of the 150 MHz radio luminosity as a star formation rate tracer suggests that a single power-law extrapolation from q1.4 GHz is not an accurate approximation at all redshifts.

A SNAPshot of the FUV (1320 - 1460 A) Spectrum of Lambda Vel (K4Ib-II)

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.

2010-01-01

The FUV spectrum (l330-1460A) of the K4Ib-II supergiant Lambda Vel was observed with the Cosmic Origins Spectrograph (COS) on HST, as part of the Ayres and Redfield Cycle 17 SNAP program "SNAPing Coronal Iron". This spectrum covers a region not previously seen in Lambda Vel at high resolution and reveals a rich emission-line spectrum superposed on a bright continuum, with contributions from a variety of atomic and molecular sources. Evidence of the stellar wind is seen in the P Cygni profiles of selected lines and the results of fluorescence processes are visible throughout the region. The spectrum has remarkable similarities to that of Alpha Boo (K1.5 III), but significant differences as well, including substantial FUV continuum emission, reminiscent of the M2 lab supergiant Alpha Ori, but minus the CO fundamental absorption bands seen in the latter star. However, fluoresced CO emission is present and strong, as in the K-giant stars Alpha Boo and Alpha Tau (K5 III). We present the details of this spectrum, in comparison to stars of similar temperature or luminosity and discuss the implications for the structure of and the radiative processes active in, the outer atmospheres of these stars.

IRAS 21391 + 5802 - A study in intermediate mass star formation

NASA Technical Reports Server (NTRS)

Wilking, Bruce; Mundy, Lee; Mcmullin, Joseph; Hezel, Thomas; Keene, Jocelyn

1993-01-01

We present infrared and millimeter wavelength observations of the cold IRAS source 21391 + 5802 and its associated molecular core. Infrared observations at lambda = 3.5 microns reveal a heavily obscured, central point source which is coincident with a compact lambda = 2.7 mm continuum and C18O emission region. The source radiates about 310 solar luminosities, primarily at FIR wavelengths, suggesting that it is a young stellar object of intermediate mass. The steeply rising spectral energy distribution and the large fraction of the system mass residing in circumstellar material imply that IRAS 21391 + 5802 is in an early stage of evolution. The inferred dust temperature indicates a temperature gradient in the core. A comprehensive model for the surrounding core of dust and gas is devised to match the observed dust continuum emission and multitransition CS emission from this and previous studies. We find a r exp -1.5 +/- 0.2 density gradient consistent with that of a gravitationally evolved core and a total core mass of 380 solar masses. The observed dust emission is most consistent with a lambda exp -1.5 - lambda exp -2 dust emissivity law; for a lambda exp -2 law, the data are best fit by a mass opacity coefficient of 3.6 x 10 exp -3 sq cm/g at lambda = 1.25 mm.

A SUPER-EDDINGTON, COMPTON-THICK WIND IN GRO J1655–40?

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

Neilsen, J.; Homan, J.; Rahoui, F.

2016-05-01

During its 2005 outburst, GRO J1655–40 was observed at high spectral resolution with the Chandra High-Energy Transmission Grating Spectrometer, revealing a spectrum rich with blueshifted absorption lines indicative of an accretion disk wind—apparently too hot, too dense, and too close to the black hole to be driven by radiation pressure or thermal pressure (Miller et al.). However, this exotic wind represents just one piece of the puzzle in this outburst, as its presence coincides with an extremely soft and curved X-ray continuum spectrum, remarkable X-ray variability (Uttley and Klein-Wolt), and a bright, unexpected optical/infrared blackbody component that varies on themore » orbital period. Focusing on the X-ray continuum and the optical/infrared/UV spectral energy distribution, we argue that the unusual features of this “hypersoft state” are natural consequences of a super-Eddington Compton-thick wind from the disk: the optical/infrared blackbody represents the cool photosphere of a dense, extended outflow, while the X-ray emission is explained as Compton scattering by the relatively cool, optically thick wind. This wind obscures the intrinsic luminosity of the inner disk, which we suggest may have been at or above the Eddington limit.« less

ZINGRS: Understanding Hot DOGs via the resolved radio continuum of W2246-0526

NASA Astrophysics Data System (ADS)

Hershey, Deborah; Ferkinhoff, Carl; Higdon, Sarah; Higdon, James L.; Tidwell, Hannah; Brisbin, Drew; Lamarche, Cody; Vishwas, Amit; Nikola, Thomas; Stacey, Gordon J.

2018-06-01

We present new high-resolution (~0.5”) radio-continuum images of the high-redshift galaxy W2246-0526 obtained with the Jansky Very Large Array. W2246 at z~4.6 is a hot dust obscured galaxy (Hot DOG) that have extreme luminosities, LIR > 1014 L⊙ produced by hot T~450 K dust. It hosts both an active galactic nucleus and significant star formation. Having observed the [OIII] 88 micron line from W2246 with our ZEUS spectrometer, the source is part of our ZEUS INvestigate Galaxy Reference Sample (ZINGRS). The radio images are initial observations from the ZINGRS Radio Survey where we observe the free-free and non-thermal emissions of high-z galaxies. Combining the radio emission with ALMA and ZEUS observations of the [CII] 158 micron, [OIII] 88 micron and [NII] 122 micron lines we probe the metallicity, age of stellar population, and ionization parameter. For W2246 we pay special attention to gradients of the stellar age and metallicity to determine the impact of the AGN on the host galaxy. Our work here is our initial analysis. When complete for all of ZINGRS ours findings will improve our understanding of early galaxies, including helping to explain Hot DOGs like W2246.

A Moderate Resolution NIR Spectral Library of Weak-Lined T Tauri Stars

NASA Astrophysics Data System (ADS)

Cooper, Rachel; Covey, K. R.

2013-01-01

We present a spectral library of high-quality moderate resolution (R ~ 3500) NIR spectra for 44 weak-lined T Tauri Stars (WTTS) in the Taurus-Auriga Molecular Cloud. These spectra, obtained with the TripleSpec spectrograph on the Astrophysical Research Consortium (ARC) 3.5 meter telescope, provide full coverage of the J, H, and K near-infrared bands in a single epoch. Analyzing these spectra, along with those of dwarf and giant spectral type standards from the SpeX Spectral Library, we have identified several elemental and molecular absorption lines that vary in strength with respect to each star's spectral type and luminosity class. Calibrating each of these features as a spectral type indicator, we provide a detailed characterization for each of the WTTSs in our sample, identifying each star's NIR spectral type and line-of-sight extinction, estimated both from the shape of the overall continuum and from the fluxes of the Paschen beta and Brackett gamma emission lines. In addition to improving our understanding of the properties of these WTTSs, this well characterized spectral library will be a valuable resource for analyses of the NIR continuum veiling and line emission present in the spectra of accreting classical T Tauri stars. This research was made possible by NSF Grant AST-1004107.

A Deep Proper Motion Catalog Within the Sloan Digital Sky Survey Footprint. II. The White Dwarf Luminosity Function

NASA Astrophysics Data System (ADS)

Munn, Jeffrey A.; Harris, Hugh C.; von Hippel, Ted; Kilic, Mukremin; Liebert, James W.; Williams, Kurtis A.; DeGennaro, Steven; Jeffery, Elizabeth; Dame, Kyra; Gianninas, A.; Brown, Warren R.

2017-01-01

A catalog of 8472 white dwarf (WD) candidates is presented, selected using reduced proper motions from the deep proper motion catalog of Munn et al. Candidates are selected in the magnitude range 16< r< 21.5 over 980 square degrees, and 16< r< 21.3 over an additional 1276 square degrees, within the Sloan Digital Sky Survey (SDSS) imaging footprint. Distances, bolometric luminosities, and atmospheric compositions are derived by fitting SDSS ugriz photometry to pure hydrogen and helium model atmospheres (assuming surface gravities {log} {\\text{}}g=8). The disk white dwarf luminosity function (WDLF) is constructed using a sample of 2839 stars with 5.5< {M}{bol}< 17, with statistically significant numbers of stars cooler than the turnover in the luminosity function. The WDLF for the halo is also constructed, using a sample of 135 halo WDs with 5< {M}{bol}< 16. We find space densities of disk and halo WDs in the solar neighborhood of 5.5+/- 0.1× {10}-3 {{pc}}-3 and 3.5+/- 0.7× {10}-5 {{pc}}-3, respectively. We resolve the bump in the disk WDLF due to the onset of fully convective envelopes in WDs, and see indications of it in the halo WDLF as well.

The Faint End of the z = 5 Quasar Luminosity Function from the CFHTLS

NASA Astrophysics Data System (ADS)

McGreer, Ian D.; Fan, Xiaohui; Jiang, Linhua; Cai, Zheng

2018-03-01

We present results from a spectroscopic survey of z ∼ 5 quasars in the CFHT Legacy Survey. Using both optical color selection and a likelihood method, we select 97 candidates over an area of 105 deg2 to a limit of i AB < 23.2, and 7 candidates in the range 23.2 < i AB < 23.7 over an area of 18.5 deg2. Spectroscopic observations for 43 candidates were obtained with Gemini, MMT, and Large Binocular Telescope, of which 37 are z > 4 quasars. This sample extends measurements of the quasar luminosity function ∼1.5 mag fainter than our previous work in Sloan Digital Sky Survey Stripe 82. The resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. We perform a detailed examination of our survey completeness, particularly the impact of the Lyα emission assumed in our quasar spectral models, and find hints that the observed Lyα emission from faint z ∼ 5 quasars is weaker than for z ∼ 3 quasars at a similar luminosity. Our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z = 5.

Resolved stars in nearby galaxies: Ground-based photometry of M81

NASA Technical Reports Server (NTRS)

Madore, Barry F.; Freedman, Wendy L.; Lee, Myung G.

1993-01-01

Using the Canada-France-Hawaii Telescope (CFHT) we have obtained three closely spaced epochs of calibrated Blue Violet Red Infrared (BVRI) CCD imaging of two fields in M81, each known to contain a thirty-day Cepheid. Calibrated BVRI photometry of the brightest stars in these fields is presented. The slope of the luminosity function from the brightest 3-4 mag of the main-sequence blue plume is consistent with similar determinations of the apparent luminosity function in other resolved galaxies, thereby removing the one potential deviation from universality noted by Freedman in a photographic study of luminosity functions in nearby resolved galaxies. Under the assumption that the two Cepheids are representative, a reddening-law fit to the multiwavelength BVRI period-luminosity moduli give a true distance modulus of (m-M)sub 0 = 27.79 mag for M81, corresponding to a linear distance of 3.6 Mpc. An error analysis shows that the derived true distance modulus has a random error of +/- 0.28 mag (due to the photometric uncertainties in the BVRI data), with a systematic uncertainty of +/- 0.10 mag (accounting for the combined effects of unknown phasing of the data points, and the unknown positioning of these particular stars within the Cepheid instabiliy strip).

Analyzing the Spectra of Accreting X-Ray Pulsars

NASA Astrophysics Data System (ADS)

Wolff, Michael

This proposal seeks funding for the analysis of accretion-powered X-ray pulsar spectra from NASA/ HEASARC archived X-ray data. Spectral modeling of accreting X-ray pulsars can tell us a great deal about the physical conditions in and near high mass X-ray binary systems. Such systems have accretion flows where plasma is initially channeled from an accretion disk by the strong neutron star magnetic field, eventually falling onto the magnetic polar cap of the neutron star compact object. Many of these accreting X-ray pulsars have X-ray spectra that consist of broad power-law continua with superposed cyclotron resonant scattering features indicating magnetic field strengths above 10^12 G. The energies of these cyclotron line features have recently been shown to vary with X-ray luminosity in a number of sources such as Her X-1 and V 0332+53, a phenomenon not well understood. Another recent development is the relatively new analytic model for the spectral continuum formation in accretion-powered pulsar systems developed by Becker & Wolff. In their formalism the accretion flows are assumed to go through radiation- dominated radiative shocks and settle onto the neutron star surface. The radiation field consists of strongly Comptonized bremsstrahlung emission from the entire plasma, Comptonized cyclotron emission from the de-excitations of Landau-excited electrons in the neutron star magnetic field, and Comptonized black-body emission from a thermal mound near the neutron star surface. We seek to develop the data analysis tools to apply this model framework to the X-ray data from a wide set of sources to make progress characterizing the basic accretion properties (e.g., magnetic field strength, plasma temperatures, polar cap size, accretion rate per unit area, dominance of bulk vs. thermal Comptonization) as well as understanding the variations of the cyclotron line energies with X-ray luminosity. The three major goals of our proposed work are as follows: In the first year, we will develop the new software module (essentially a computer code representing the theoretical model) necessary to perform the analysis of accretion-powered pulsar X-ray spectra in the XSPEC spectral analysis environment. Also in this first year we will analyze new Suzaku Cycle 6 Target of Opportunity observations of GX 304-1 and 4U 0115+63, two known cyclotron line sources, that we have recently carried out. In the second year of this study we will apply our new XSPEC spectral continuum module to the archival X-ray observational data from a number of accreting X-ray pulsars from the RXTE/PCA/HEXTE and Suzaku/XIS/HXD instruments to extract basic accretion parameters. Our source list contains eight pulsars, seven of which have observed cyclotron scattering lines. These pulsars span a range in magnetic field strength, luminosity, expected accretion rate, expected polar cap size, and Comptonizing temperature. In the second year of this work we also plan to make our new fully tested XSPEC continuum analysis module available to the Goddard Space Flight Center HEASARC for distribution to the astrophysical research community. The development and analysis tasks proposed here will provide for the first time a physical basis for the analysis and interpretation of data on accreting X-ray pulsar spectra.

Gamma-Ray Bursts and Cosmology

NASA Technical Reports Server (NTRS)

Norris, Jay P.

2003-01-01

The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

The 2.4 μm Galaxy Luminosity Function As Measured Using WISE. I. Measurement Techniques

NASA Astrophysics Data System (ADS)

Lake, S. E.; Wright, E. L.; Tsai, C.-W.; Lam, A.

2017-04-01

The astronomy community has at its disposal a large back catalog of public spectroscopic galaxy redshift surveys that can be used for the measurement of luminosity functions (LFs). Utilizing the back catalog with new photometric surveys to maximum efficiency requires modeling the color selection bias imposed on the selection of target galaxies by flux limits at multiple wavelengths. The likelihood derived herein can address, in principle, all possible color selection biases through the use of a generalization of the LF, {{Φ }}(L), over the space of all spectra: the spectro-luminosity functional, {{\\Psi }}[{L}ν ]. It is, therefore, the first estimator capable of simultaneously analyzing multiple redshift surveys in a consistent way. We also propose a new way of parametrizing the evolution of the classic Schechter function parameters, L ⋆ and ϕ ⋆, that improves both the physical realism and statistical performance of the model. The techniques derived in this paper are used in a companion paper by Lake et al. to measure the LF of galaxies at the rest-frame wavelength of 2.4 μ {{m}} using the Widefield Infrared Survey Explorer (WISE).

DUST PROPERTIES OF LOCAL DUST-OBSCURED GALAXIES WITH THE SUBMILLIMETER ARRAY

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

Hwang, Ho Seong; Andrews, Sean M.; Geller, Margaret J., E-mail: hhwang@cfa.harvard.edu, E-mail: sandrews@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu

We report Submillimeter Array observations of the 880 μm dust continuum emission for four dust-obscured galaxies (DOGs) in the local universe. Two DOGs are clearly detected with S{sub ν}(880 μm) =10-13 mJy and S/N > 5, but the other two are not detected with 3σ upper limits of S{sub ν}(880 μm) =5-9 mJy. Including an additional two local DOGs with submillimeter data from the literature, we determine the dust masses and temperatures for six local DOGs. The infrared luminosities and dust masses for these DOGs are in the ranges of 1.2-4.9 × 10{sup 11}(L{sub ☉}) and 4-14 × 10{sup 7}(M{submore » ☉}), respectively. The dust temperatures derived from a two-component modified blackbody function are 23-26 K and 60-124 K for the cold and warm dust components, respectively. Comparison of local DOGs with other infrared luminous galaxies with submillimeter detections shows that the dust temperatures and masses do not differ significantly among these objects. Thus, as argued previously, local DOGs are not a distinctive population among dusty galaxies, but simply represent the high-end tail of the dust obscuration distribution.« less

The gamma-ray luminosity function of millisecond pulsars and implications for the GeV excess

DOE PAGES

Hooper, Dan; Mohlabeng, Gopolang

2016-03-29

It has been proposed that a large population of unresolved millisecond pulsars (MSPs) could potentially account for the excess of GeV-scale gamma-rays observed from the region surrounding the Galactic Center. The viability of this scenario depends critically on the gamma-ray luminosity function of this source population, which determines how many MSPs Fermi should have already detected as resolved point sources. In this paper, we revisit the gamma-ray luminosity function of MSPs, without relying on uncertain distance measurements. Our determination, based on a comparison of models with the observed characteristics of the MSP population, suggests that Fermi should have already detectedmore » a significant number of sources associated with such a hypothesized Inner Galaxy population. As a result, we cannot rule out a scenario in which the MSPs residing near the Galactic Center are systematically less luminous than those present in the Galactic Plane or within globular clusters.« less

Cosmic Evolution of Accretion Power and Fusion Power: AGN and Starbursts at High Redshifts

NASA Astrophysics Data System (ADS)

Arnold Malkan, Matthew

2009-05-01

Extragalactic astronomers have been working for decades on obtaining robust measures of the luminosities galaxies produce from stars, and from active galactic nuclei. Our ultimate goal is deriving the cosmic evolution of all radiation produced by fusion and by black hole accretion. The combined effects of dust reddening and redshift make it impossible to achieve this with optical observations alone. Fortunately, infrared thermal continuum and forbidden line emission--from warm dust grains and ionized gas, respectively--can now be measured with excellent sensitivity. However, when measuring entire galaxies, these dust and gas emissions are powered by both active galactic nuclei and starbursts, which may be hard to separate spatially. We must use the fact that the patterns of IR energy output from AGN and SBs differ, with AGN making more ionized gas and hotter dust grains. Low-resolution spectroscopy, or even narrow-band filters can sort out the line emission from both processes when they are mixed in the same galaxy. The hope is that these spectroscopic determinations of star formation rate, and mass accretion rate in relatively small samples of bright galaxies will allow a calibration of broadband continuum measures. The dust continuum emission will then be measured in enormous samples of galaxies spanning their full range of masses, metallicities, environments and redshifts. Along the way, we should learn the astrophysical basis of black hole/galaxy "co-evolution." I will summarize some of the first specific infrared steps of this ambitious agenda, taken with IRAS and ISO to 2MASS, Akari and Spitzer and other telescopes. Time permitting, some of the exciting upcoming observational prospects will be advertised.

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

NASA Astrophysics Data System (ADS)

Shlosman, Isaac

2016-10-01

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

High-resolution Observations of the Massive Protostar in IRAS 18566+0408

NASA Astrophysics Data System (ADS)

Hofner, P.; Cesaroni, R.; Kurtz, S.; Rosero, V.; Anderson, C.; Furuya, R. S.; Araya, E. D.; Molinari, S.

2017-07-01

We report 3 mm continuum, CH3CN(5-4) and 13CS(2-1) line observations with CARMA (Combined Array for Research in Millimeter-wave Astronomy), in conjunction with 6 and 1.3 cm continuum VLA data, and 12 and 25 μm broadband data from the Subaru Telescope toward the massive proto-star IRAS 18566+0408. The VLA data resolve the ionized jet into four components aligned in the E-W direction. Radio components A, C, and D have flat centimeter SEDs indicative of optically thin emission from ionized gas, and component B has a spectral index α = 1.0, and a decreasing size with frequency \\propto {ν }-0.5. Emission from the CARMA 3 mm continuum and from the 13CS(2-1) and CH3CN(5-4) spectral lines is compact (I.e., < 6700 {au}) and peaks near the position of the VLA centimeter source, component B. Analysis of these lines indicates hot and dense molecular gas, which is typical for HMCs. Our Subaru telescope observations detect a single compact source, coincident with radio component B, demonstrating that most of the energy in IRAS 18566+0408 originates from a region of size < 2400 {au}. We also present UKIRT near-infrared archival data for IRAS 18566+0408, which show extended K-band emission along the jet direction. We detect an E-W velocity shift of about 10 km s-1 over the HMC in the CH3CN lines possibly tracing the interface of the ionized jet with the surrounding core gas. Our data demonstrate the presence of an ionized jet at the base of the molecular outflow and support the hypothesis that massive protostars with O-type luminosity form with a mechanism similar to lower mass stars.

Binarity and Accretion in AGB Stars: HST/STIS Observations of UV Flickering in Y Gem

NASA Astrophysics Data System (ADS)

Sahai, R.; Sánchez Contreras, C.; Mangan, A. S.; Sanz-Forcada, J.; Muthumariappan, C.; Claussen, M. J.

2018-06-01

Binarity is believed to dramatically affect the history and geometry of mass loss in AGB and post-AGB stars, but observational evidence of binarity is sorely lacking. As part of a project to search for hot binary companions to cool AGB stars using the GALEX archive, we discovered a late-M star, Y Gem, to be a source of strong and variable UV and X-ray emission. Here we report UV spectroscopic observations of Y Gem obtained with the Hubble Space Telescope that show strong flickering in the UV continuum on timescales of ≲20 s, characteristic of an active accretion disk. Several UV lines with P-Cygni-type profiles from species such as Si IV and C IV are also observed, with emission and absorption features that are red- and blueshifted by velocities of ∼500 {km} {{{s}}}-1 from the systemic velocity. Our model for these (and previous) observations is that material from the primary star is gravitationally captured by a companion, producing a hot accretion disk. The latter powers a fast outflow that produces blueshifted features due to the absorption of UV continuum emitted by the disk, whereas the redshifted emission features arise in heated infalling material from the primary. The outflow velocities support a previous inference by Sahai et al. that Y Gem’s companion is a low-mass main-sequence star. Blackbody fitting of the UV continuum implies an accretion luminosity of about 13 L ⊙, and thus a mass-accretion rate >5 × 10‑7 M ⊙ yr‑1 we infer that Roche-lobe overflow is the most likely binary accretion mode for Y Gem.

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

Hunter, T. R.; Brogan, C. L.; Indebetouw, R.

Based on sub-arcsecond Atacama Large Millimeter/submillimeter Array (ALMA) and Submillimeter Array (SMA) 1.3 mm continuum images of the massive protocluster NGC 6334I obtained in 2015 and 2008, we find that the dust emission from MM1 has increased by a factor of 4.0 ± 0.3 during the intervening years, and undergone a significant change in morphology. The continuum emission from the other cluster members (MM2, MM4, and the UCH ii region MM3 = NGC 6334F) has remained constant. Long-term single-dish maser monitoring at HartRAO finds that multiple maser species toward NGC 6334I flared beginning in early 2015, a few months beforemore » our ALMA observation, and some persist in that state. New ALMA images obtained in 2016 July–August at 1.1 and 0.87 mm confirm the changes with respect to SMA 0.87 mm images from 2008, and indicate that the (sub)millimeter flaring has continued for at least a year. The excess continuum emission, centered on the hypercompact H ii region MM1B, is extended and elongated (1.″6 × 1.″0 ≈ 2100 × 1300 au) with multiple peaks, suggestive of general heating of the surrounding subcomponents of MM1, some of which may trace clumps in a fragmented disk rather than separate protostars. In either case, these remarkable increases in maser and dust emission provide direct observational evidence of a sudden accretion event in the growth of a massive protostar yielding a sustained luminosity surge by a factor of 70 ± 20, analogous to the largest events in simulations by Meyer et al. This target provides an excellent opportunity to assess the impact of such a rare event on a protocluster over many years.« less

THE LUMINOSITY FUNCTION OF FERMI-DETECTED FLAT-SPECTRUM RADIO QUASARS

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

Ajello, M.; Shaw, M. S.; Romani, R. W.

2012-06-01

Fermi has provided the largest sample of {gamma}-ray-selected blazars to date. In this work we use a complete sample of flat spectrum radio quasars (FSRQs) detected during the first year of operation to determine the luminosity function (LF) and its evolution with cosmic time. The number density of FSRQs grows dramatically up to redshift {approx}0.5-2.0 and declines thereafter. The redshift of the peak in the density is luminosity dependent, with more luminous sources peaking at earlier times; thus the LF of {gamma}-ray FSRQs follows a luminosity-dependent density evolution similar to that of radio-quiet active galactic nuclei. Also, using data frommore » the Swift Burst Alert Telescope we derive the average spectral energy distribution (SED) of FSRQs in the 10 keV-300 GeV band and show that there is no correlation between the luminosity at the peak of the {gamma}-ray emission component and its peak frequency. Using this luminosity-independent SED with the derived LF allows us to predict that the contribution of FSRQs to the Fermi isotropic {gamma}-ray background is 9.3{sup +1.6}{sub -1.0}% ({+-}3% systematic uncertainty) in the 0.1-100 GeV band. Finally we determine the LF of unbeamed FSRQs, finding that FSRQs have an average Lorentz factor of {gamma} = 11.7{sup +3.3}{sub -2.2}, that most are seen within 5 Degree-Sign of the jet axis, and that they represent only {approx}0.1% of the parent population.« less

The SAGA Survey. I. Satellite Galaxy Populations around Eight Milky Way Analogs

NASA Astrophysics Data System (ADS)

Geha, Marla; Wechsler, Risa H.; Mao, Yao-Yuan; Tollerud, Erik J.; Weiner, Benjamin; Bernstein, Rebecca; Hoyle, Ben; Marchi, Sebastian; Marshall, Phil J.; Muñoz, Ricardo; Lu, Yu

2017-09-01

We present the survey strategy and early results of the “Satellites Around Galactic Analogs” (SAGA) Survey. The SAGA Survey’s goal is to measure the distribution of satellite galaxies around 100 systems analogous to the Milky Way down to the luminosity of the Leo I dwarf galaxy ({M}r< -12.3). We define a Milky Way analog based on K-band luminosity and local environment. Here, we present satellite luminosity functions for eight Milky-Way-analog galaxies between 20 and 40 Mpc. These systems have nearly complete spectroscopic coverage of candidate satellites within the projected host virial radius down to {r}o< 20.75 using low-redshift gri color criteria. We have discovered a total of 25 new satellite galaxies: 14 new satellite galaxies meet our formal criteria around our complete host systems, plus 11 additional satellites in either incompletely surveyed hosts or below our formal magnitude limit. Combined with 13 previously known satellites, there are a total of 27 satellites around 8 complete Milky-Way-analog hosts. We find a wide distribution in the number of satellites per host, from 1 to 9, in the luminosity range for which there are 5 Milky Way satellites. Standard abundance matching extrapolated from higher luminosities predicts less scatter between hosts and a steeper luminosity function slope than observed. We find that the majority of satellites (26 of 27) are star-forming. These early results indicate that the Milky Way has a different satellite population than typical in our sample, potentially changing the physical interpretation of measurements based only on the Milky Way’s satellite galaxies.

The spectral energy distribution of the redshift 7.1 quasar ULAS J1120+0641

NASA Astrophysics Data System (ADS)

Barnett, R.; Warren, S. J.; Banerji, M.; McMahon, R. G.; Hewett, P. C.; Mortlock, D. J.; Simpson, C.; Venemans, B. P.; Ota, K.; Shibuya, T.

2015-03-01

We present new observations of the highest-redshift quasar known, ULAS J1120+0641, redshift z = 7.084, obtained in the optical, at near-, mid-, and far-infrared wavelengths, and in the sub-mm. We combine these results with published X-ray and radio observations to create the multiwavelength spectral energy distribution (SED), with the goals of measuring the bolometric luminosity Lbol, and quantifying the respective contributions from the AGN and star formation. We find three components are needed to fit the data over the wavelength range 0.12-1000 μm: the unobscured quasar accretion disk and broad-line region, a dusty clumpy AGN torus, and a cool 47K modified black body to characterise star formation. Despite the low signal-to-noise ratio of the new long-wavelength data, the normalisation of any dusty torus model is constrained within ±40%. We measure a bolometric luminosity Lbol = 2.6 ± 0.6 × 1047 erg s-1 = 6.7 ± 1.6 × 1013 L⊙, to which the three components contribute 31%,32%,3%, respectively, with the remainder provided by the extreme UV < 0.12 μm. We tabulate the best-fit model SED. We use local scaling relations to estimate a star formation rate (SFR) in the range 60-270 M⊙/yr from the [C ii] line luminosity and the 158 μm continuum luminosity. An analysis of the equivalent widths of the [C ii] line in a sample of z> 5.7 quasars suggests that these indicators are promising tools for estimating the SFR in high-redshift quasars in general. At the time observed the black hole was growing in mass more than 100 times faster than the stellar bulge, relative to the mass ratio measured in the local universe, i.e. compared to MBH/Mbulge ≃ 1.4 × 10-3, for ULAS J1120+0641 we measure ṀBH/Ṁbulge ≃ 0.2. Full Table 3 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/575/A31

Cosmic Star Formation History and Evolution of the Galaxy UV Luminosity Function for z < 1

NASA Astrophysics Data System (ADS)

Zhang, Keming; Schiminovich, David

2018-01-01

We present the latest constraints on the evolution of the far-ultraviolet luminosity function of galaxies (1500 Å, UVLF hereafter) for 0 < z < 1 based on GALEX photometry, with redshift measurements from four spectroscopic and photometric-redshift catalogs: NSA, GAMA, VIPERS, and COSMOS photo-z. Our final sample consists of ~170000 galaxies, which represents the largest sample used in such studies. By integrating wide NSA and GAMA data and deep VIPERS and COSMOS photo-z data, we have been able to constrain both the bright end and the faint end of the luminosity function with high accuracy over the entire redshift range. We fit a Schechter function to our measurements of the UVLF, both to parameterize its evolution, and to integrate for SFR densities. From z~1 to z~0, the characteristic absolute magnitude of the UVLF increases linearly by ~1.5 magnitudes, while the faint end slope remains shallow (alpha < 1.5). However, the Schechter function fit exhibits an excess of galaxies at the bright end, which is accounted for by contributions from AGN. We also describe our methodology, which can be applied more generally to any combination of wide-shallow and deep-narrow surveys.

ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: CO LUMINOSITY FUNCTIONS AND THE EVOLUTION OF THE COSMIC DENSITY OF MOLECULAR GAS

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

Decarli, Roberto; Walter, Fabian; Aravena, Manuel

2016-12-10

In this paper we use ASPECS, the ALMA Spectroscopic Survey in the Hubble Ultra Deep Field in band 3 and band 6, to place blind constraints on the CO luminosity function and the evolution of the cosmic molecular gas density as a function of redshift up to z  ∼ 4.5. This study is based on galaxies that have been selected solely through their CO emission and not through any other property. In all of the redshift bins the ASPECS measurements reach the predicted “knee” of the CO luminosity function (around 5 × 10{sup 9} K km s{sup −1} pc{sup 2}). We find clear evidence ofmore » an evolution in the CO luminosity function with respect to z  ∼ 0, with more CO-luminous galaxies present at z  ∼ 2. The observed galaxies at z  ∼ 2 also appear more gas-rich than predicted by recent semi-analytical models. The comoving cosmic molecular gas density within galaxies as a function of redshift shows a drop by a factor of 3–10 from z  ∼ 2 to z  ∼ 0 (with significant error bars), and possibly a decline at z  > 3. This trend is similar to the observed evolution of the cosmic star formation rate density. The latter therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation ( z  ∼ 2).« less

The gamma-ray pulsar population of globular clusters: implications for the GeV excess

NASA Astrophysics Data System (ADS)

Hooper, Dan; Linden, Tim

2016-08-01

It has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecond pulsars in the Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their luminosity function to depart from the steady-state distribution. Using this luminosity function and a model for the globular cluster disruption rate, we show that millisecond pulsars born in globular clusters can account for only a few percent or less of the observed GeV excess. Among other challenges, scenarios in which the entire GeV excess is generated from such pulsars are in conflict with the observed mass of the Milky Way's Central Stellar Cluster.

The gamma-ray pulsar population of globular clusters: implications for the GeV excess

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

Hooper, Dan; Linden, Tim, E-mail: dhooper@fnal.gov, E-mail: linden.70@osu.edu

It has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecond pulsars in themore » Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their luminosity function to depart from the steady-state distribution. Using this luminosity function and a model for the globular cluster disruption rate, we show that millisecond pulsars born in globular clusters can account for only a few percent or less of the observed GeV excess. Among other challenges, scenarios in which the entire GeV excess is generated from such pulsars are in conflict with the observed mass of the Milky Way's Central Stellar Cluster.« less

The gamma-ray pulsar population of globular clusters: Implications for the GeV excess

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

Hooper, Dan; Linden, Tim

In this study, it has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecondmore » pulsars in the Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their luminosity function to depart from the steady-state distribution. Using this luminosity function and a model for the globular cluster disruption rate, we show that millisecond pulsars born in globular clusters can account for only a few percent or less of the observed GeV excess. Among other challenges, scenarios in which the entire GeV excess is generated from such pulsars are in conflict with the observed mass of the Milky Way's Central Stellar Cluster.« less

The gamma-ray pulsar population of globular clusters: Implications for the GeV excess

DOE PAGES

Hooper, Dan; Linden, Tim

2016-08-09

In this study, it has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecondmore » pulsars in the Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their luminosity function to depart from the steady-state distribution. Using this luminosity function and a model for the globular cluster disruption rate, we show that millisecond pulsars born in globular clusters can account for only a few percent or less of the observed GeV excess. Among other challenges, scenarios in which the entire GeV excess is generated from such pulsars are in conflict with the observed mass of the Milky Way's Central Stellar Cluster.« less

Compton scattering of the microwave background by quasar-blown bubbles

NASA Technical Reports Server (NTRS)

Voit, G. Mark

1994-01-01

At least 10% of quasars drive rapid outflows from the central regions of their host galaxies. The mass and energy flow rates in these winds are difficult to measure, but their kinetic luminosities probably exceed 10(exp 45) ergs/s. This kind of outflow easily sunders the interstellar medium of the host and blows a bubble in the intergalactic medium. After the quasar shuts off, the hot bubble continues to shock intergalactic gas until its leading edge merges with the Hubble flow. The interior hot gas Compton scatters microwave background photons, potentially providing a way to detect these bubbles. Assuming that quasar kinetic luminosities scale with their blue luminosities, we integrate over the quasar luminosity function to find the total distortion (y) of the microwave background produced by the entire population of quasar wind bubbles. This calculation of y distortion is remarkably insensitive to the properties of the intergalactic medium (IGM), quasar lifetimes, and cosmological parameters. Current Cosmic Background Explorer (COBE) limits on y constrain the kinetic luminosities of quasars to be less than several times their bolometric radiative luminosities. Within this constraint, quasars can still expel enough kinetic luminosity to shock the entire IGM by z = 0, but cannot heat and ionize the IGM by z = 4 unless omega(sub IGM) much less than 10(exp -2).

Angular resolution and range of dipole-dipole correlations in water

NASA Astrophysics Data System (ADS)

Mathias, Gerald; Tavan, Paul

2004-03-01

We investigate the dipolar correlations in liquid water at angular resolution by molecular-dynamics simulations of a large periodic simulation system containing about 40 000 molecules. Because we are particularly interested in the long-range ordering, we use a simple three-point model for these molecules. The electrostatics is treated both by Ewald summation and by minimum image truncation combined with a reaction field approach. To gain insight into the angular dependence of the simulated dipolar ordering we introduce a suitable expansion of the molecular pair distribution function into a set of two-dimensional correlation functions. We show that these functions enable detailed insights into the shell structure of the dipolar ordering around a given water molecule. For these functions we derive analytical expressions in the particular case in which liquid water is conceived as a dielectric continuum. Comparisons of these continuum models with the correlation functions derived from the simulations yield the key result that liquid water behaves like a continuum dielectric beyond distances of about 15 Å from a given water molecule. We argue that this should be a generic property of water independent of our modeling. By comparison of the results of the two different electrostatics treatments with the continuum description we show that the boundary artifacts occurring in both methods are isotropically distributed and are locally small in the respective boundary regions.

THE STELLAR POPULATION AND STAR FORMATION RATES OF z Almost-Equal-To 1.5-1.6 [O II]-EMITTING GALAXIES SELECTED FROM NARROWBAND EMISSION-LINE SURVEYS

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

Ly, Chun; Malkan, Matthew A.; Ross, Nathaniel R.

We present the first detailed study of the stellar populations of star-forming galaxies at z {approx} 1.5, which are selected by their [O II] emission line, detected in narrowband surveys. We identified {approx}1300 [O II] emitters at z = 1.47 and z = 1.62 in the Subaru Deep Field with rest-frame equivalent widths (EWs) above 13 A. Optical and near-infrared spectroscopic observations for Almost-Equal-To 10% of our samples show that our separation of [O II] from [O III] emission-line galaxies in two-color space is 99% successful. We analyze the multi-wavelength properties of a subset of {approx}1200 galaxies with the bestmore » photometry. They have average rest-frame EW of 45 A, stellar mass of 3 Multiplication-Sign 10{sup 9} M{sub Sun }, and stellar age of 100 Myr. In addition, our spectral energy distribution (SED) fitting and broadband colors indicate that [O II] emitters span the full range of galaxy populations at z {approx} 1.5. We also find that 80% of [O II] emitters are also photometrically classified as 'BX/BM' (UV) galaxies and/or the star-forming 'BzK' (near-IR) galaxies. Our [O II] emission line survey produces a far more complete and somewhat deeper sample of z {approx} 1.5 galaxies than either the BX/BM or sBzK selection alone. We constructed average SEDs and find that higher [O II] EW galaxies have somewhat bluer continua. SED model-fitting shows that they have on average half the stellar mass of galaxies with lower [O II] EW. The observed [O II] luminosity is well correlated with the far-UV continuum with a logarithmic slope of 0.89 {+-} 0.22. The scatter of the [O II] luminosity against the far-UV continuum suggests that [O II] can be used as a star formation rate indicator with a reliability of 0.23 dex.« less

Black hole mass estimates and emission-line properties of a sample of redshift z > 6.5 quasars

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

De Rosa, Gisella; Peterson, Bradley M.; Frank, Stephan

We present the analysis of optical and near-infrared spectra of the only four z > 6.5 quasars known to date, discovered in the UKIDSS-LAS and VISTA-VIKING surveys. Our data set consists of new Very Large Telescope/X-Shooter and Magellan/FIRE observations. These are the best optical/NIR spectroscopic data that are likely to be obtained for the z > 6.5 sample using current 6-10 m facilities. We estimate the black hole (BH) mass, the Eddington ratio, and the Si IV/C IV, C III]/C IV, and Fe II/Mg II emission-line flux ratios. We perform spectral modeling using a procedure that allows us to derivemore » a probability distribution for the continuum components and to obtain the quasar properties weighted upon the underlying distribution of continuum models. The z > 6.5 quasars show the same emission properties as their counterparts at lower redshifts. The z > 6.5 quasars host BHs with masses of ∼10{sup 9} M{sub ☉} that are accreting close to the Eddington luminosity ((log(L{sub Bol}/L{sub Edd})) = –0.4 ± 0.2), in agreement with what has been observed for a sample of 4.0 < z < 6.5 quasars. By comparing the Si IV/C IV and C III]/C IV flux ratios with the results obtained from luminosity-matched samples at z ∼ 6 and 2 ≤ z ≤ 4.5, we find no evidence of evolution of the line ratios with cosmic time. We compare the measured Fe II/Mg II flux ratios with those obtained for a sample of 4.0 < z < 6.4 sources. The two samples are analyzed using a consistent procedure. There is no evidence that the Fe II/Mg II flux ratio evolves between z = 7 and z = 4. Under the assumption that the Fe II/Mg II traces the Fe/Mg abundance ratio, this implies the presence of major episodes of chemical enrichment in the quasar hosts in the first ∼0.8 Gyr after the Big Bang.« less

Detection of [O III] at z ∼ 3: A Galaxy Above the Main Sequence, Rapidly Assembling Its Stellar Mass

NASA Astrophysics Data System (ADS)

Vishwas, Amit; Ferkinhoff, Carl; Nikola, Thomas; Parshley, Stephen C.; Schoenwald, Justin P.; Stacey, Gordon J.; Higdon, Sarah J. U.; Higdon, James L.; Weiss, Axel; Güsten, Rolf; Menten, Karl M.

2018-04-01

We detect bright emission in the far-infrared (far-IR) fine structure [O III] 88 μm line from a strong lensing candidate galaxy, H-ATLAS J113526.3-014605, hereafter G12v2.43, at z = 3.127, using the second-generation Redshift (z) and Early Universe Spectrometer (ZEUS-2) at the Atacama Pathfinder Experiment Telescope (APEX). This is only the fifth detection of this far-IR line from a submillimeter galaxy at the epoch of galaxy assembly. The observed [O III] luminosity of 7.1 × 109 ≤ft(\\tfrac{10}{μ }\\right) L ⊙ likely arises from H II regions around massive stars, and the amount of Lyman continuum photons required to support the ionization indicate the presence of (1.2–5.2) × 106 ≤ft(\\tfrac{10}{μ }\\right) equivalent O5.5 or higher stars, where μ would be the lensing magnification factor. The observed line luminosity also requires a minimum mass of ∼2 × 108 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ in ionized gas, that is 0.33% of the estimated total molecular gas mass of 6 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We compile multi-band photometry tracing rest-frame ultraviolet to millimeter continuum emission to further constrain the properties of this dusty high-redshift, star-forming galaxy. Via SED modeling we find G12v2.43 is forming stars at a rate of 916 ≤ft(\\tfrac{10}{μ }\\right) M ⊙ yr‑1 and already has a stellar mass of 8 × 1010 ≤ft(\\tfrac{10}{μ }\\right) M ⊙. We also constrain the age of the current starburst to be ≤slant 5 Myr, making G12v2.43 a gas-rich galaxy lying above the star-forming main sequence at z ∼ 3, undergoing a growth spurt, and it could be on the main sequence within the derived gas depletion timescale of ∼66 Myr.

Two extreme young objects in Barnard 1-b

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

Hirano, Naomi; Liu, Fang-chun, E-mail: hirano@asiaa.sinica.edu.tw

2014-07-01

Two submillimeter/millimeter sources in the Barnard 1b (B1-b) core, B1-bN and B1-bS, have been studied in dust continuum, H{sup 13}CO{sup +} J = 1-0, CO J = 2-1, {sup 13}CO J = 2-1, and C{sup 18}O J = 2-1. The spectral energy distributions of these sources from the mid-IR to 7 mm are characterized by very cold temperatures of T {sub dust} < 20 K and low bolometric luminosities of 0.15-0.31 L {sub ☉}. The internal luminosities of B1-bN and B1-bS are estimated to be <0.01-0.03 L {sub ☉} and ∼0.1-0.2 L {sub ☉}, respectively. Millimeter interferometric observations have shownmore » that these sources have already formed central compact objects of ∼100 AU sizes. Both B1-bN and B1-bS are driving the CO outflows with low characteristic velocities of ∼2-4 km s{sup –1}. The fractional abundance of H{sup 13}CO{sup +} at the positions of B1-bN and B1-bS is lower than the canonical value by a factor of four to eight. This implies that a significant fraction of CO is depleted onto dust grains in the dense gas surrounding these sources. The observed physical and chemical properties suggest that B1-bN and B1-bS are in an earlier evolutionary stage than most of the known class 0 protostars. In particular, the properties of B1-bN agree with those of the first hydrostatic core predicted by the MHD simulations. The CO outflow was also detected in the mid-IR source located at ∼15'' from B1-bS. Since the dust continuum emission was not detected in this source, the circumstellar material surrounding this source is less than 0.01 M {sub ☉}. It is likely that the envelope of this source was dissipated by the outflow from the protostar that is located to the southwest of B1-b.« less

Measuring the Stellar Populations of Individual Lyman Alpha Emitters During the Epoch of Peak Star Formation

NASA Astrophysics Data System (ADS)

Reddy, Naveen

2010-09-01

Selecting galaxies by their strong Lyman-alpha emission provides a powerful means of probing the reionization epoch and the faint/low-mass galaxies that dominate star formation at high redshift. Yet, our understanding of high-redshift Lyman-alpha emitters {LAEs} has lagged behind that of other well-studied populations {e.g., Lyman break galaxies} due to their continuum faintness and the shifting of age/mass-sensitive features into the near-IR where the high terrestrial background inhibits deep observations. All existing studies of LAEs at z>2 have used stacked optical and/or Spitzer infrared data to discern their median properties, but the actual distributions of ages, reddenings, and stellar masses for these populations are poorly characterized. To fill this glaring gap in the observations and advance our understanding of this important population, we propose WFC3/IR+F160W imaging of fields where we have conducted a survey of low redshift {z 1.9} Lyman-alpha emitters {LAEs}, in order to measure their ages and stellar masses at an epoch where such observations directly probe the age-sensitive Balmer/4000 AA breaks. The targeted sample will include 45-50 spectroscopically confirmed LAEs at z=1.7-2.1 and roughly twice as many candidates, making it the largest sample of homogeneously selected LAEs with individual measurements of the ages, masses, and dust extinction. With these data we will {1} carefully take into account the age-dependence of the extinction curve to make robust comparisons between LAEs and continuum-selected galaxies at the same redshifts; {2} combine clustering and stellar mass measurements to infer the duty cycles of LAEs and determine if they are triggered in the presence of large-scale structures; and {3} quantify the importance of the LAE phase at different galaxy luminosity and mass scales, over a large dynamic range in these properties. An economical investment of just 12 orbits will allow us to accomplish these goals, and remains the only hope of efficiently studying such low luminosity high-redshift galaxies in the near-IR prior to the JWST-era.

Massive Star Formation of the SGR a East H (sub II) Regions Near the Galactic Center

NASA Technical Reports Server (NTRS)

Yusef-Zadeh, F.; Lacy, J. H.; Wardle, M.; Whitney, B.; Bushouse, H.; Roberts, D. A.; Arendt, R. G.

2010-01-01

A group of four compact H II regions associated with the well-known 50 km/s molecular cloud is the closest site of on-going star formation to the dynamical center of the Galaxy, at a projected distance of approximately 6 pc. We present a study of ionized gas based on the [Ne II] (12.8 micron) line, as well as multi-frequency radio continuum, Hubble Space Telescope Pa alpha, and Spitzer Infrared Array Camera observations of the most compact member of the H II group, Sgr A East H II D. The radio continuum image at 6 cm shows that this source breaks up into two equally bright ionized features, D1 and D2. The spectral energy distribution of the D source is consistent with it being due to a 25 =/- 3 solar mass star with a luminosity of 8 +/- 3 x 10(exp 4) Solar luminosity . The inferred mass, effective temperature of the UV source, and the ionization rate are compatible with a young O9-B0 star. The ionized features D1 and D2 are considered to be ionized by UV radiation collimated by an accretion disk. We consider that the central massive star photoevaporates its circumstellar disk on a timescale of 3x (exp 4) years giving a mass flux approximately 3 x 10(exp -5) Solar Mass / year and producing the ionized material in D1 and D2 expanding in an inhomogeneous medium. The ionized gas kinematics, as traced by the [Ne II] emission, is difficult to interpret, but it could be explained by the interaction of a bipolar jet with surrounding gas along with what appears to be a conical wall of lower velocity gas. The other H II regions, Sgr A East A-C, have morphologies and kinematics that more closely resemble cometary flows seen in other compact H II regions, where gas moves along a paraboloidal surface formed by the interaction of a stellar wind with a molecular cloud.

Optical, IUE, and ROSAT observations of the eclipsing nova-like variable V347 Puppis (LB 1800)

NASA Technical Reports Server (NTRS)

Mauche, Christopher W.; Raymond, John C.; Buckley, David A. H.; Mouchet, Martine; Bonnell, Jerry; Sullivan, Denis J.; Bonnet-Bidaud, Jean-Marc; Bunk, Wolfram H.

1994-01-01

Using time-resolved optical spectroscopy and UBVRI and high-speed photometry obtained at Mount Stromlo Observatory, Mount John University Observatory, and the South African Astronomical Observatory; International Ultraviolet Explorer (IUE) ultraviolet spectroscopy; and Roentgen Satellite (ROSAT) survey X-ray fluxes, we present a study of the accretion disk, hot spot, and emission line regions in the bright eclipsing nova-like variable V347 Pup (LB 1800). In the optical and UV, V347 Pup is a strong emission line source with a continuum spectrum which is remarkably red for a high-M cataclysmic variable. Consistent with its high inclination, we interpret the continuum spectrum as the superposition of the spectrum of the cool (T(sub eff) approximately 7000 K) outer edge and the hot (T(sub eff) approximately 100,000 K) inner regions of a self-eclipsed accretion disk. For the assumed parameters, the model matches the level and shape of the observed spectrum for an inclination of approximately 88 and a distance of approximately 300 pc. The prominent hump in the optical and UV light curves just before eclipse manifests the presence of the hot spot where the accretion stream strikes the edge of the disk. The wavelength dependence of the amplitude of the hump is best modeled by a spot having an effective temperature of approximately 25,000 K and an area of approximately 3 x 10(exp 18) sq cm if the spot radiates like a blackbody, or an effective temperatue of approximately 14,000 K and an area of approximately 3 x 10(exp 19) sq cm if it radiates with a stellar spectrum. In either case, the hot spot produces only one-tenth of the predicted luminosity for the assumed mass-transfer rate of 10(exp -8) solar mass/yr. Either the hot spot is 'buried' in the edge of the accretion disk, or a significant fraction of its luminosity is radiated away in lines. The difference in azimuth between the peak of the hump and the dynamically expected location of the hot spot suggests that the spot's emitting surface is rotated forward by approximately 36 deg relative to the edge of the disk.

Optical, IUE, and ROSAT observations of the eclipsing nova-like variable V347 Puppis (LB 1800)

NASA Astrophysics Data System (ADS)

Mauche, Christopher W.; Raymond, John C.; Buckley, David A. H.; Mouchet, Martine; Bonnell, Jerry; Sullivan, Denis J.; Bonnet-Bidaud, Jean-Marc; Bunk, Wolfram H.

1994-03-01

Using time-resolved optical spectroscopy and UBVRI and high-speed photometry obtained at Mount Stromlo Observatory, Mount John University Observatory, and the South African Astronomical Observatory; International Ultraviolet Explorer (IUE) ultraviolet spectroscopy; and Roentgen Satellite (ROSAT) survey X-ray fluxes, we present a study of the accretion disk, hot spot, and emission line regions in the bright eclipsing nova-like variable V347 Pup (LB 1800). In the optical and UV, V347 Pup is a strong emission line source with a continuum spectrum which is remarkably red for a high-M cataclysmic variable. Consistent with its high inclination, we interpret the continuum spectrum as the superposition of the spectrum of the cool (Teff approximately 7000 K) outer edge and the hot (Teff approximately 100,000 K) inner regions of a self-eclipsed accretion disk. For the assumed parameters, the model matches the level and shape of the observed spectrum for an inclination of approximately 88 and a distance of approximately 300 pc. The prominent hump in the optical and UV light curves just before eclipse manifests the presence of the hot spot where the accretion stream strikes the edge of the disk. The wavelength dependence of the amplitude of the hump is best modeled by a spot having an effective temperature of approximately 25,000 K and an area of approximately 3 x 1018 sq cm if the spot radiates like a blackbody, or an effective temperatue of approximately 14,000 K and an area of approximately 3 x 1019 sq cm if it radiates with a stellar spectrum. In either case, the hot spot produces only one-tenth of the predicted luminosity for the assumed mass-transfer rate of 10-8 solar mass/yr. Either the hot spot is 'buried' in the edge of the accretion disk, or a significant fraction of its luminosity is radiated away in lines. The difference in azimuth between the peak of the hump and the dynamically expected location of the hot spot suggests that the spot's emitting surface is rotated forward by approximately 36 deg relative to the edge of the disk.

Calculation of photoionization differential cross sections using complex Gauss-type orbitals.

PubMed

Matsuzaki, Rei; Yabushita, Satoshi

2017-09-05

Accurate theoretical calculation of photoelectron angular distributions for general molecules is becoming an important tool to image various chemical reactions in real time. We show in this article that not only photoionization total cross sections but also photoelectron angular distributions can be accurately calculated using complex Gauss-type orbital (cGTO) basis functions. Our method can be easily combined with existing quantum chemistry techniques including electron correlation effects, and applied to various molecules. The so-called two-potential formula is applied to represent the transition dipole moment from an initial bound state to a final continuum state in the molecular coordinate frame. The two required continuum functions, the zeroth-order final continuum state and the first-order wave function induced by the photon field, have been variationally obtained using the complex basis function method with a mixture of appropriate cGTOs and conventional real Gauss-type orbitals (GTOs) to represent the continuum orbitals as well as the remaining bound orbitals. The complex orbital exponents of the cGTOs are optimized by fitting to the outgoing Coulomb functions. The efficiency of the current method is demonstrated through the calculations of the asymmetry parameters and molecular-frame photoelectron angular distributions of H2+ and H2 . In the calculations of H2 , the static exchange and random phase approximations are employed, and the dependence of the results on the basis functions is discussed. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Dual number algebra method for Green's function derivatives in 3D magneto-electro-elasticity

NASA Astrophysics Data System (ADS)

Dziatkiewicz, Grzegorz

2018-01-01

The Green functions are the basic elements of the boundary element method. To obtain the boundary integral formulation the Green function and its derivative should be known for the considered differential operator. Today the interesting group of materials are electronic composites. The special case of the electronic composite is the magnetoelectroelastic continuum. The mentioned continuum is a model of the piezoelectric-piezomagnetic composites. The anisotropy of their physical properties makes the problem of Green's function determination very difficult. For that reason Green's functions for the magnetoelectroelastic continuum are not known in the closed form and numerical methods should be applied to determine such Green's functions. These means that the problem of the accurate and simply determination of Green's function derivatives is even harder. Therefore in the present work the dual number algebra method is applied to calculate numerically the derivatives of 3D Green's functions for the magnetoelectroelastic materials. The introduced method is independent on the step size and it can be treated as a special case of the automatic differentiation method. Therefore, the dual number algebra method can be applied as a tool for checking the accuracy of the well-known finite difference schemes.

A singular finite element technique for calculating continuum damping of Alfvén eigenmodes

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

Bowden, G. W.; Hole, M. J.

2015-02-15

Damping due to continuum resonances can be calculated using dissipation-less ideal magnetohydrodynamics provided that the poles due to these resonances are properly treated. We describe a singular finite element technique for calculating the continuum damping of Alfvén waves. A Frobenius expansion is used to determine appropriate finite element basis functions on an inner region surrounding a pole due to the continuum resonance. The location of the pole due to the continuum resonance and mode frequency is calculated iteratively using a Galerkin method. This method is used to find the complex frequency and mode structure of a toroidicity-induced Alfvén eigenmode inmore » a large aspect ratio circular tokamak and is shown to agree closely with a complex contour technique.« less

Modeling the evolution of infrared galaxies: a parametric backward evolution model

NASA Astrophysics Data System (ADS)

Béthermin, M.; Dole, H.; Lagache, G.; Le Borgne, D.; Penin, A.

2011-05-01

Aims: We attempt to model the infrared galaxy evolution in as simple a way as possible and reproduce statistical properties such as the number counts between 15 μm and 1.1 mm, the luminosity functions, and the redshift distributions. We then use the fitted model to interpret observations from Spitzer, AKARI, BLAST, LABOCA, AzTEC, SPT, and Herschel, and make predictions for Planck and future experiments such as CCAT or SPICA. Methods: This model uses an evolution in density and luminosity of the luminosity function parametrized by broken power-laws with two breaks at redshift ~0.9 and 2, and contains the two populations of the Lagache model: normal and starburst galaxies. We also take into account the effect of the strong lensing of high-redshift sub-millimeter galaxies. This effect is significant in the sub-mm and mm range near 50 mJy. It has 13 free parameters and eight additional calibration parameters. We fit the parameters to the IRAS, Spitzer, Herschel, and AzTEC measurements with a Monte Carlo Markov chain. Results: The model adjusted to deep counts at key wavelengths reproduces the counts from mid-infrared to millimeter wavelengths, as well as the mid-infrared luminosity functions. We discuss the contribution to both the cosmic infrared background (CIB) and the infrared luminosity density of the different populations. We also estimate the effect of the lensing on the number counts, and discuss the discovery by the South Pole Telescope (SPT) of a very bright population lying at high redshift. We predict the contribution of the lensed sources to the Planck number counts, the confusion level for future missions using a P(D) formalism, and the Universe opacity to TeV photons caused by the CIB. Material of the model (software, tables and predictions) is available online.

Modeling the Redshift Evolution of the Normal Galaxy X-Ray Luminosity Function

NASA Technical Reports Server (NTRS)

Tremmel, M.; Fragos, T.; Lehmer, B. D.; Tzanavaris, P.; Belczynski, K.; Kalogera, V.; Basu-Zych, A. R.; Farr, W. M.; Hornschemeier, A.; Jenkins, L.;

The number counts and infrared backgrounds from infrared-bright galaxies

NASA Technical Reports Server (NTRS)

Hacking, P. B.; Soifer, B. T.

1991-01-01

Extragalactic number counts and diffuse backgrounds at 25, 60, and 100 microns are predicted using new luminosity functions and improved spectral-energy distribution density functions derived from IRAS observations of nearby galaxies. Galaxies at redshifts z less than 3 that are like those in the local universe should produce a minimum diffuse background of 0.0085, 0.038, and 0.13 MJy/sr at 25, 60, and 100 microns, respectively. Models with significant luminosity evolution predict backgrounds about a factor of 4 greater than this minimum.

The small numbers of large Kuiper Belt objects

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

Schwamb, Megan E.; Brown, Michael E.; Fraser, Wesley C., E-mail: mschwamb@asiaa.sinica.edu.tw

2014-01-01

We explore the brightness distribution of the largest and brightest (m(R) < 22) Kuiper Belt Objects (KBOs). We construct a luminosity function of the dynamically excited or hot Kuiper Belt (orbits with inclinations >5°) from the very brightest to m(R) = 23. We find for m(R) ≲ 23, a single slope appears to describe the luminosity function. We estimate that ∼12 KBOs brighter than m(R) ∼ 19.5 are present in the Kuiper Belt today. With nine bodies already discovered this suggests that the inventory of bright KBOs is nearly complete.

A Synthesis Of Cosmic X-ray And Infrared Background

NASA Astrophysics Data System (ADS)

Shi, Yong; Helou, G.; Armus, L.; Stierwalt, S.

2012-01-01

We present a synthesis model of cosmic IR and X-ray background, with the goal to derive a complete census of cosmic evolution of star formation (SF) and black-hole (BH) growth by complementing advantages of X-ray and IR surveys to each other. By assuming that individual galaxies are experiencing both SF and BH accretion, our model decomposes the total IR LF into SF and BH components while taking into account the luminosity-dependent SED and its dispersion of the SF component, and the extinction-dependent SED of the BH component. The best-fit parameters are derived by fitting to the number counts and redshift distributions at X-ray including both hard and soft bands, and mid-IR to submm bands including IRAS, Spitzer, Herschel, SCUBA, Aztec and MAMBO. Based on the fit result, our models provide a series of predictions on galaxy evolution and black-hole growth. For evolution of infrared galaxies, the model predicts that the total infrared luminosity function is best described through evolution in both luminosity and density. For evolution of AGN populations, the model predicts that the evolution of X-ray LF also shows luminosity and density dependent, that the type-1/type-2 AGN fraction is a function of both luminosity and redshift, and that the Compton-thick AGN number density evolves strongly with redshift, contributing about 20% to the total cosmic BH growth. For BH growth in IR galaxies, the model predicts that the majority of BH growth at z>1 occurs in infrared luminous galaxies and the AGN fraction as a function of IR survey is a strong function of the survey depth, ranging from >50% at bright end to below 10% at faint end. We also evaluates various AGN selection techniques at X-ray and IR wavelengths and offer predictions for future missions at X-ray and IR.

Extragalactic High-energy Transients: Event Rate Densities and Luminosity Functions

NASA Astrophysics Data System (ADS)

Sun, Hui; Zhang, Bing; Li, Zhuo

2015-10-01

Several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with an associated relativistic jet. In this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (GLFs; ignoring redshift evolution) of these transients. We introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its GLF. Long GRBs (LGRBs) have a large enough sample to reveal features in the GLF, which is best charaterized as a triple power law (PL). All the other transients are consistent with having a single-power-law (SPL) LF. The total event rate density depends on the minimum luminosity, and we obtain the following values in units of Gpc-3 yr-1: {0.8}-0.1+0.1 for high-luminosity LGRBs above 1050 erg s-1 {164}-65+98 for low-luminosity LGRBs above 5 × 1046 erg s-1 {1.3}-0.3+0.4, {1.2}-0.3+0.4, and {3.3}-0.8+1.0 above 1050 erg s-1 for short GRBs with three different merger delay models (Gaussian, lognormal, and PL); {1.9}-1.2+2.4× {10}4 above 1044 erg s-1 for SBOs, {4.8}-2.1+3.2× {10}2 for normal TDEs above 1044 erg s-1 and {0.03}-0.02+0.04 above 1048 erg s-1 for TDE jets as discovered by Swift. Intriguingly, the GLFs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an SPL with an index of -1.6.

The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

NASA Astrophysics Data System (ADS)

Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

2011-02-01

We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Einstein X-ray observations of Herbig Ae/Be stars

NASA Technical Reports Server (NTRS)

Damiani, F.; Micela, G.; Sciortino, S.; Harnden, F. R., Jr.

1994-01-01

We have investigated the X-ray emission from Herbig Ae/Be stars, using the full set of Einstein Imaging Proportional Counter (IPC) observations. Of a total of 31 observed Herbig stars, 11 are confidently identified with X-ray sources, with four additonal dubious identifications. We have used maximum likelihood luminosity functions to study the distribution of X-ray luminosity, and we find that Be stars are significantly brighter in X-rays than Ae stars and that their X-ray luminosity is independent of projected rotational velocity v sin i. The X-ray emission is instead correlated with stellar bolometric luminosity and with effective temperature, and also with the kinetic luminosity of the stellar wind. These results seem to exclude a solar-like origin for the X-ray emission, a possibility suggested by the most recent models of Herbig stars' structure, and suggest an analogy with the X-ray emission of O (and early B) stars. We also observe correlations between X-ray luminosity and the emission at 2.2 microns (K band) and 25 microns, which strengthen the case for X-ray emission of Herbig stars originating in their circumstellar envelopes.

The Ionized Gas and Nuclear Environment in NGC 3783. IV; Variability and Modeling of the 900 ks CHANDRA Spectrum

NASA Technical Reports Server (NTRS)

Netzer, Hagai; Kaspi, Shai; Behar, Ehud; Brandt, W. N.; Chelouche, Doron; George, Ian M.; Crenshaw, D. Michael; Gabel, Jack R.; Hamann, Frederick W.; George, Steven B.

2003-01-01

We present a detailed analysis of the 900 ks spectrum of NGC3783 obtained by Chandra in 2000-2001 (Kaspi et al. 2002). We split the data in various ways to look for time dependent and luminosity dependent spectral variations. This analysis, the measured equivalent widths of a large number of X-ray lines, and our photoionization calculations, lead us to the following conclusions: 1) NGC 3783 fluctuated in luminosity, by a factor N 1.5, during individual 170 ks observations. The fluctuations were not associated with significant spectral variations. 2) On a longer time scale, of 20-120 days, we discovered two very different spectral shapes that are noted the high state and the low state spectra. The observed changes between the two can be described as the appearance and disappearance of a soft continuum component. The spectral variations are not related, in a simple way, to the brightening or the fading of the short wavelength continuum, as observed in other objects. NGC3783 seems to be the first AGN to show this unusual behavior. 3) The appearance of the soft continuum component is consistent with beeing the only spectral variation and there is no need to invoke changes in the absorber s opacity. In particular, all absorption lines with reliable measurements show the same equivalent width, within the observational uncertainties, during high and low states. 4) Photoionization model calculations show that a combination of three ionization components, each split into two kinematic components, explain very well the intensity of almost all absorption lines and the bound-free absorption. The components span a large range of ionization and a total column of about 3 x 10(exp 22) per square centimeter Moreover, all components are thermally stable and are situated on the vertical branch of the stability curve.. This means that they are in pressure equilibrium and perhaps occupy the same volume of space. This is the first detection of such a multi-component equilibrium gas in AGN. 5) The only real discrepancy between the model and the observations is the wavelength of the iron M-shell UTA feature. This is most likely due to an underestimation of the dielectronic recombination O VI and discuss its possible origin. 6) The lower limit on the distance of the absorbing gas in NGC3783 is between 0.2 and 3.2 pc, depending of the specific ionization component. The constant pressure assumption imposes an upper limit of about 25 pc on the distance of the least ionized gas from the central sourec.

Photoionization of furan from the ground and excited electronic states.

PubMed

Ponzi, Aurora; Sapunar, Marin; Angeli, Celestino; Cimiraglia, Renzo; Došlić, Nađa; Decleva, Piero

2016-02-28

Here we present a comparative computational study of the photoionization of furan from the ground and the two lowest-lying excited electronic states. The study aims to assess the quality of the computational methods currently employed for treating bound and continuum states in photoionization. For the ionization from the ground electronic state, we show that the Dyson orbital approach combined with an accurate solution of the continuum one particle wave functions in a multicenter B-spline basis, at the density functional theory (DFT) level, provides cross sections and asymmetry parameters in excellent agreement with experimental data. On the contrary, when the Dyson orbitals approach is combined with the Coulomb and orthogonalized Coulomb treatments of the continuum, the results are qualitatively different. In excited electronic states, three electronic structure methods, TDDFT, ADC(2), and CASSCF, have been used for the computation of the Dyson orbitals, while the continuum was treated at the B-spline/DFT level. We show that photoionization observables are sensitive probes of the nature of the excited states as well as of the quality of excited state wave functions. This paves the way for applications in more complex situations such as time resolved photoionization spectroscopy.

Far-infrared emission and star formation in spiral galaxies

NASA Technical Reports Server (NTRS)

Trinchieri, G.; Fabbiano, G.; Bandiera, R.

1989-01-01

The correlations between the emission in the far-IR, H-alpha, and blue in a sample of normal spiral galaxies are investigated. It is found that the luminosities in these three bands are all tightly correlated, although both the strength of the correlations and their functional dependencies are a function of the galaxies' morphological types. The best-fit power laws to these correlations are different for the comparison of different quantities and deviate significantly from linearity in some cases, implying the presence of additional emission mechanisms not related to the general increase of luminosity with galactic mass. Clear evidence is found of two independent effects in the incidence of warm far-IR emission in late-type spirals. One is a luminosity effect shown by the presence of excess far-IR relative to H-alpha or optical emission in the more luminous galaxies. The other is a dependence on widespread star-formation activity.

LFsGRB: Binary neutron star merger rate via the luminosity function of short gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFsGRB models the luminosity function (LF) of short Gamma Ray Bursts (sGRBs) by using the available catalog data of all short GRBs (sGRBs) detected till 2017 October, estimating the luminosities via pseudo-redshifts obtained from the Yonetoku correlation, and then assuming a standard delay distribution between the cosmic star formation rate and the production rate of their progenitors. The data are fit well both by exponential cutoff powerlaw and broken powerlaw models. Using the derived parameters of these models along with conservative values in the jet opening angles seen from afterglow observations, the true rate of short GRBs is derived. Assuming a short GRB is produced from each binary neutron star merger (BNSM), the rate of gravitational wave (GW) detections from these mergers are derived for the past, present and future configurations of the GW detector networks.