Browsing by Subject "quasars: general"
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Item Accretion Disk Temperatures Of QSOs: Constraints From The Emission Lines(2013-06) Bonning, E. W.; Shields, Gregory A.; Stevens, A. C.; Salviander, Sarah; Shields, Gregory A.; Stevens, A. C.; Salviander, SarahWe compare QSO emission-line spectra to predictions based on theoretical ionizing continua of accretion disks. The observed line intensities do not show the expected trend of higher ionization with theoretical accretion disk temperature as predicted from the black hole mass and accretion rate. Consistent with earlier studies, this suggests that the inner disk does not reach temperatures as high as expected from standard disk theory. Modified radial temperature profiles, taking account of winds or advection in the inner disk, achieve better agreement with observation. The emission lines of radio-detected and radio-undetected sources show different trends as a function of the theoretically predicted disk temperature.Item Accretion Onto "Seed" Black Holes In The First Galaxies(2009-06) Milosavljevic, Milos; Bromm, Volker; Couch, Sean M.; Oh, S. Peng; Milosavljevic, Milos; Bromm, Volker; Couch, Sean M.The validity of the hypothesis that the massive black holes in high redshift quasars grew from stellar-sized "seeds" is contingent on a seed's ability to double its mass every few 10 million years. This requires that the seed accrete at approximately the Eddington-limited rate. In the specific case of radiatively efficient quasi-radial accretion in a metal-poor protogalactic medium, for which the Bondi accretion rate is often prescribed in cosmological simulations of massive black hole formation, we examine the effects of the radiation emitted near the black hole's event horizon on the structure of the surrounding gas flow. We find that photoheating and radiation pressure from photoionization significantly reduce the steady-Stateaccretion rate and potentially render the quasi-radial accretion flow unsteady and inefficient. The time-averaged accretion rate is always a small fraction of the "Bondi" accretion rate calculated ignoring radiative feedback. The pressure of Ly alpha photons trapped near the H II region surrounding the black hole may further attenuate the inflow. These results suggest that an alternative to quasi-radial, radiatively efficient Bondi-like accretion should be sought to explain the rapid growth of quasar-progenitor seed black holes.Item Accretion onto Intermediate-Mass Black Holes in Dense Protogalactic Clouds(2009-05) Milosavljevi?, Miloš; Couch, Sean M.; Bromm, Volker; Milosavljevi?, Miloš; Couch, Sean M.; Bromm, VolkerWe present the first results from two-dimensional simulations of radiatively efficient accretion of metal-free gas onto intermediate-mass black holes. We fix the shape of the spectral energy distribution of the radiation produced near the event horizon and study the structure of the irradiated low-angular-momentum accretion flow over 3 orders of magnitude in radius from the black hole, 10(14)-10(17) cm for a 100 M(circle dot) black hole. The luminosity of the central source is made to be proportional to the rate at which gas accretes across the inner boundary, which we set just inside the sonic radius. We find that photoionization heating and radiation pressure modify the structure of the flow. When the ambient gas density is 10(7) cm(-3), accretion is intermittent and on average reduced to 32% of the Eddington-limited rate, over 2 orders of magnitude below the "Bondi" rate evaluated ignoring radiation, in agreement with theoretical models. Even if the vicinity of the black hole is supplied with high-density gas, accretion is rendered inefficient through heating and radiation pressure.Item Black Hole Mass And Eddington Ratio Distribution Functions Of X-Ray-Selected Broad-Line AGNs At Z Similar To 1.4 In The Subaru XMM-Newton Deep Field(2012-12) Nobuta, K.; Akiyama, M.; Ueda, Y.; Watson, M. G.; Silverman, J.; Hiroi, K.; Ohta, K.; Iwamuro, F.; Yabe, K.; Tamura, N.; Moritani, Y.; Sumiyoshi, M.; Takato, N.; Kimura, M.; Maihara, T.; Dalton, G.; Lewis, I.; Bonfield, D.; Lee, H.; Curtis-Lake, E.; Macaulay, E.; Clarke, F.; Sekiguchi, K.; Simpson, C.; Croom, S.; Ouchi, Masami; Hanami, H.; Yamada, T.; Lee, H.In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z similar to 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 angstrom monochromatic luminosity. We supplement the Mg II FWHM values with the H alpha FWHM obtained from our NIR spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V-max method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF at z = 1.4 has a higher number density above 10(8) M-circle dot but a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.Item The Black Hole Mass-Galaxy Luminosity Relationship For Sloan Digital Sky Survey Quasars(2015-02) Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.We investigate the relationship between the mass of the central supermassive black hole, M-BH, and the host galaxy luminosity, L-gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M-BH-L-gal relationship by examining the redshift dependence of Delta log M-BH, the offset in M-BH from the local M-BH-L-gal relationship. There is little systematic trend in. log MBH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, sigma(*), we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for sigma(*) in statistical studies.Item The Black Hole Mass-Stellar Velocity Dispersion Relationship For Quasars In The Sloan Digital Sky Survey Data Release 7(2013-02) Salviander, Sarah; Shields, Gregory A.; Salviander, Sarah; Shields, Gregory A.We assess evolution in the M-BH-sigma(*) relationship for quasars in the Sloan Digital Sky Survey Data Release 7 for the redshift range 0.1 < z < 1.2. We estimate the black hole mass, M-BH, using the "photoionization method," with the broad H beta or Mg II emission line and the quasar continuum luminosity. For the stellar velocity dispersion, we use the narrow [O III] or [O II] emission line as a surrogate. This study is a follow-up to an earlier study in which we investigated evolution in the M-BH-sigma(*) relationship in quasars from Data Release 3. The greatly increased number of quasars in our new sample has allowed us to break our lower-redshift subsample into black hole mass bins and probe the M-BH-sigma(*) relationship for constant black hole mass. The M-BH-sigma(*) relationship for the highest-mass (M-BH > 10(9.0) M-circle dot) and lowest-mass (M-BH < 10(7.5) M-circle dot) black holes appears to evolve significantly; however, most or all of this apparent evolution can be accounted for by various observational biases due to intrinsic scatter in the relationship and to uncertainties in observed quantities. The M-BH-sigma(*) relationship for black holes in the middle mass range (10(7.5) < M-BH < 10(9.0) M-circle dot) shows minimal change with redshift. The overall results suggest a limit of +/-0.2 dex on any evolution in the M-BH-sigma(*) relationship for quasars out to z approximate to 1 compared with the relationship observed in the local universe. Intrinsic scatter may also provide a plausible way to reconcile the wide range of results of several different studies of the black hole-galaxy relationships.Item A Captured Runaway Black Hole in NGC 1277?(2013-07) Shields, G. A.; Bonning, E. W.; Shields, G. A.Recent results indicate that the compact lenticular galaxy NGC 1277 in the Perseus Cluster contains a black hole of mass similar to 10(10) M-circle dot. This far exceeds the expected mass of the central black hole in a galaxy of the modest dimensions of NGC 1277. We suggest that this giant black hole was ejected from the nearby giant galaxy NGC 1275 and subsequently captured by NGC 1277. The ejection was the result of gravitational radiation recoil when two large black holes merged following the merger of two giant ellipticals that helped to form NGC 1275. The black hole wandered in the cluster core until it was captured in a close encounter with NGC 1277. The migration of black holes in clusters may be a common occurrence.Item Comment On The Black Hole Recoil Candidate Quasar SDSS J092712.65+294344.0(2009-05) Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, SarahThe Sloan Digital Sky Survey (SDSS) quasar J092712.65+294344.0 has been proposed as a candidate for a supermassive black hole (similar to 10(8.8) M(circle dot)) ejected at high speed from the host galactic nucleus by gravitational radiation recoil, or alternatively for a supermassive black hole binary. This is based on a blueshift of 2650 km s(-1) of the broad emission lines ("b-system") relative to the narrow emission lines ("r-system") presumed to reflect the galaxy velocity. New observations with the Hobby-Eberly Telescope (HET) confirm the essential features of the spectrum. We note a third redshift system, characterized by weak, narrow emission lines of [O III] and [O II] at an intermediate velocity 900 km s(-1) redward of the broad-line velocity ("i-system"). A composite spectrum of SDSS QSOs similar to J0927+2943 illustrates the feasibility of detecting the calcium K absorption line in spectra of sufficient quality. The i-system may represent the QSO host galaxy or a companion. Photoionization requires the black hole to be similar to 3 kpc from the r-system emitting gas, implying that we are observing the system only 10(6) yr after the recoil event and contributing to the low probability of observing such a system. The HET observations give an upper limit of 10 km s(-1) per year on the rate of change of the velocity difference between the r- and b-systems, constraining the orbital phase in the binary model. These considerations and the presence of a cluster of galaxies apparently containing J0927+2943 favor the idea that this system represents a superposition of two active galactic nuclei.Item Discovery Of Polarization Reverberation In NGC 4151(2012-04) Gaskell, C. Martin; Goosmann, Rene W.; Merkulova, Nelly I.; Shakhovskoy, Nikolay M.; Shoji, Masatoshi; Gaskell, C. Martin; Shoji, MasatoshiObservations of the optical polarization of NGC 4151 in 1997-2003 show variations of an order of magnitude in the polarized flux while the polarization position angle remains constant. The amplitude of variability of the polarized flux is comparable to the amplitude of variability of the total U-band flux, except that the polarized flux follows the total flux with a lag of 8 +/- 3 days. The time lag and the constancy of the position angle strongly favor a scattering origin for the variable polarization rather than a non-thermal synchrotron origin. The orientation of the position angle of the polarized flux (parallel to the radio axis) and the size of the lag imply that the polarization arises from electron scattering in a flattened region within the low-ionization component of the broad-line region. Polarization from dust scattering in the equatorial torus is ruled out as the source of the lag in polarized flux because it would produce a larger lag and, unless the half-opening angle of the torus is >53 degrees, the polarization would be perpendicular to the radio axis. We note a long-term change in the percentage of polarization at similar total flux levels, and this could be due either to changing non-axisymmetry in the optical continuum emission or a change in the number of scatterers on a timescale of years.Item Dissipation and Extra Light in Galactic Nuclei. II. "Cusp" Ellipticals(2009-03) Hopkins, Philip F.; Cox, Thomas J.; Dutta, Suvendra N.; Hernquist, Lars; Kormendy, John; Lauer, Tod R.; Kormendy, JohnWe study the origin and properties of "extra" or "excess" central light in the surface brightness profiles of cusp or power-law elliptical galaxies. Dissipational mergers give rise to two-component profiles: an outer profile established by violent relaxation acting on stars already present in the progenitor galaxies prior to the final stages of the merger, and an inner stellar population comprising the extra light, formed in a compact central starburst. By combining a large set of hydrodynamical simulations with data that span a broad range of profiles at various masses, we show that observed cusp ellipticals appear consistent with the predicted "extra light" structure, and we use our simulations to motivate a two-component description of the observations that allows us to examine how the properties and mass of this component scale with, e. g., the mass, gas content, and other properties of the galaxies. We show how to robustly separate the physically meaningful extra light and outer, violently relaxed profile, and demonstrate that the observed cusps and "extra light" are reliable tracers of the degree of dissipation in the spheroid-forming merger. We show that the typical degree of dissipation is a strong function of stellar mass, roughly tracing the observed gas fractions of disks of the same mass over the redshift range z similar to 0-2. We demonstrate a correlation between the strength of this component and effective radius at fixed mass, in the sense that systems with more dissipation are more compact, sufficient to explain the discrepancy in the maximum phase-space and mass densities of ellipticals and their progenitor spirals. We show that the outer shape of the light profile in simulated and observed systems (when fit to properly account for the central light) does not depend on mass, with a mean outer Sersic index similar to 2.5. We also explore how this relates to, e. g., the shapes, kinematic properties, and stellar population gradients of ellipticals. Extra light contributes to making remnants rounder and diskier, and imprints stellar population gradients. Simulations with the gas content needed to match observed surface brightness profiles reproduce the observed age, metallicity, and color gradients of cusp ellipticals, and we make predictions for how these can be used as tracers of the degree of dissipation in spheroid Formation.Item Double-Peaked Narrow-Line Active Galactic Nuclei. II. The Case Of Equal Peaks(2012-06) Smith, K. L.; Shields, Gregory A.; Salviander, Sarah; Stevens, A. C.; Rosario, D. J.; Smith, K. L.; Shields, Gregory A.; Salviander, Sarah; Stevens, A. C.Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs in which the two narrow-line components have closely similar intensity as being especially likely to involve disks or jets. Two spectroscopic indicators support this likelihood. For DPAGNs from Smith et al., the "equal-peaked" objects (EPAGNs) have [Ne V]/[O III] ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs in a galactic merger, but may be consistent with [O III] emission from a rotating ring with relatively little gas at small radii. Also, [O III]/H beta ratios of the redshifted and blueshifted systems in the EPAGN are more similar to each other than in a control sample, suggestive of a single ionizing source and inconsistent with the binary interpretation.Item Fe II Emission In Active Galactic Nuclei: The Role Of Total And Gas-Phase Iron Abundance(2010-10) Shields, Gregory A.; Ludwig, Randi R.; Salviander, Sarah; Shields, Gregory A.; Ludwig, Randi R.; Salviander, SarahActive galactic nuclei (AGNs) have Fe II emission from the broad-line region (BLR) that differs greatly in strength from object to object. We examine the role of the total and gas-phase iron abundance in determining Fe II strength. Using AGN spectra from the Sloan Digital Sky Survey (SDSS) in the redshift range of 0.2 < z < 0.35, we measure the Fe/Ne abundance of the narrow-line region (NLR) using the [Fe VII]/[Ne v] line intensity ratio. We find no significant difference in the abundance of Fe relative to Ne in the NLR as a function of Fe II/H beta. However, the [N II]/[S II] ratio increases by a factor of 2 with increasing Fe II strength. This indicates a trend in N/S abundance ratio, and by implication in the overall metallicity of the NLR gas, with increasing Fe II strength. We propose that the wide range of Fe II strength in AGN largely results from the selective depletion of Fe into grains in the low ionization portion of the BLR. Photoionization models show that the strength of the optical Fe II lines varies almost linearly with gas-phase Fe abundance, while the ultraviolet Fe II strength varies more weakly. Interstellar depletions of Fe can be as large as 2 orders of magnitude, sufficient to explain the wide range of optical Fe II strength in AGNs. This picture is consistent with the similarity of the BLR radius to the dust sublimation radius and with indications of Fe II emitting gas flowing inward from the dusty torus.Item Five-Year Wilkinson Microwave Anisotropy Probe Observations: Source Catalog(2009-02) Wright, E. L.; Chen, X.; Odegard, N.; Bennett, C. L.; Hill, R. S.; Hinshaw, G.; Jarosik, N.; Komatsu, Eiichiro; Nolta, M. R.; Page, L.; Spergel, D. N.; Weiland, J. L.; Wollack, E.; Dunkley, J.; Gold, B.; Halpern, M.; Kogut, A.; Larson, D.; Limon, M.; Meyer, S. S.; Tucker, G. S.; Komatsu, EiichiroWe present the list of point sources found in the Wilkinson Microwave Anisotropy Probe (WMAP) five-year maps. The technique used in the first-year and three-year analyses now finds 390 point sources, and the five-year source catalog is complete for regions of the sky away from the Galactic plane to a 2 Jy limit, with SNR > 4.7 in all bands in the least covered parts of the sky. The noise at high frequencies is still mainly radiometer noise, but at low frequencies the cosmic microwave background (CMB) anisotropy is the largest uncertainty. A separate search of CMB-free V-W maps finds 99 sources of which all but one can be identified with known radio sources. The sources seen by WMAP are not strongly polarized. Many of the WMAP sources show significant variability from year to year, with more than a 2: 1 range between the minimum and maximum fluxes.Item LBQS 0103-2753: A Binary Quasar In A Major Merger(2012-01) Shields, Gregory A.; Rosario, D. J.; Junkkarinen, V.; Chapman, S. C.; Bonning, E. W.; Chiba, T.; Shields, Gregory A.We present Hubble Space Telescope (HST) and United Kingdom Infrared Telescope spectra and images of the 2 kpc (0.'' 3) binary quasar LBQS 0103-2753 (z = 0.858). The HST images (V and I bands) show tidal features demonstrating that this system is a major galaxy merger in progress. A two-color composite image brings out knots of star formation along the tidal arc and elsewhere. The infrared spectrum shows that both objects are at the same redshift and that the discrepant redshift of C IV in component A is not representative of the true systemic redshift of this component. LBQS 0103-2753 is one of the most closely spaced binary QSOs known and is one of the relatively few dual active galactic nuclei showing confirmed broad emission lines from both components. While statistical studies of binary QSOs suggest that simultaneous fueling of both black holes during a merger may be relatively rare, LBQS 0103-2753 demonstrates that such fueling can occur at high luminosity at a late stage in the merger at nuclear spacing of only a few kpc, without severe obscuration of the nuclei.Item A Massive, Distant Proto-Cluster at Z=2.47 Caught in a Phase of Rapid Formation?(2015-08) Casey, C. M.; Cooray, A.; Capak, P.; Fu, H.; Kovac, K.; Lilly, S.; Sanders, D. B.; Scoville, N. Z.; Treister, E.; Casey, C. M.Numerical simulations of cosmological structure Formation show that the universe's most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times (2.5 < z < 4). While more than 20 proto-clusters have been observed at z greater than or similar to 2 based on associations of 5-40 galaxies around rare sources, the observational evidence for rapid cluster Formation is weak. Here we report observations of an asymmetric filamentary structure at z = 2.47 containing 7 starbursting, submillimeter-luminous galaxies and 5 additional active galactic nuclei (AGNs) within a comoving volume of 15,000 Mpc(3). As the expected lifetime of both the luminous AGN and starburst phase of a galaxy is similar to 100 Myr, we conclude that these sources were likely triggered in rapid succession by environmental factors or, alternatively, the duration of these cosmologically rare phenomena is much longer than prior direct measurements suggest. The stellar mass already built up in the structure is similar to 10(12) M-circle dot and we estimate that the cluster mass will exceed that of the Coma supercluster at z similar to 0. The filamentary structure is in line with hierarchical growth simulations that predict that the peak of cluster activity occurs rapidly at z > 2.Item McDonald Observatory Archive of Optical Linear Polarization Measurements(2011-06) Wills, Beverley J.; Wills, D.; Breger, Michael; Wills, Beverley J.; Wills, D.; Breger, MichaelWe present 990 previously unpublished optical linear polarization measurements of quasars, active galactic nuclei, and some stars observed for interstellar polarization. The observations, covering the period 1981-2000, were made with McDonald Observatory's 2.1 m Struve reflector and the Breger photopolarimeter.Item Millimeter Observations Of A Sample Of High-Redshift Obscured Quasars(2009-11) Martinez-Sansigre, Alejo; Karim, Alexander; Schinnerer, Eva; Omont, Alain; Smith, Daniel J. B.; Wu, Jingwen; Hill, Gary J.; Klockner, Hans-rainer; Lacy, Mark; Rawlings, Steve; Willott, Chris J.; Hill, Gary J.We present observations at 1.2 mm with Max-Planck Millimetre Bolometer Array (MAMBO-II) of a sample of z greater than or similar to 2 radio-intermediate obscured quasars, as well as CO observations of two sources with the Plateau de Bure Interferometer. The typical rms noise achieved by the MAMBO observations is 0.55 mJy beam(-1) and five out of 21 sources (24%) are detected at a significance of >= 3 sigma. Stacking all sources leads to a statistical detection of < S(1.2 mm)> = 0.96 +/- 0.11 mJy and stacking only the non-detections also yields a statistical detection, with < S(1.2 mm)> = 0.51 +/- 0.13 mJy. At the typical redshift of the sample, z = 2, 1 mJy corresponds to a far-infrared luminosity L(FIR) similar to 4 x 10(12) L(circle dot). If the far-infrared luminosity is powered entirely by star formation, and not by active galactic nucleus heated dust, then the characteristic inferred star formation rate is similar to 700 M(circle dot) yr(-1). This far-infrared luminosity implies a dust mass of M(d) similar to 3 x 10(8) M(circle dot), which is expected to be distributed on similar to kpc scales. We estimate that such large dust masses on kpc scales can plausibly cause the obscuration of the quasars. Combining our observations at 1.2 mm with mid-and far-infrared data, and additional observations for two objects at 350 mu m using SHARC-II, we present dust spectral energy distributions (SEDs) for our sample and derive a mean SED for our sample. This mean SED is not well fitted by clumpy torus models, unless additional extinction and far-infrared re-emission due to cool dust are included. This additional extinction can be consistently achieved by the mass of cool dust responsible for the far-infrared emission, provided the bulk of the dust is within a radius similar to 2-3 kpc. Comparison of our sample to other samples of z similar to 2 quasars suggests that obscured quasars have, on average, higher far-infrared luminosities than unobscured quasars. There is a hint that the host galaxies of obscured quasars must have higher cool-dustmasses and are therefore often found at an earlier evolutionary phase than those of unobscured quasars. For one source at z = 2.767, we detect the CO(3-2) transition, with S(CO)Delta nu = 630 +/- 50 mJy km s(-1), corresponding to L(CO(3-2)) = 3.2 x 10(7) L(circle dot), or a brightness-temperature luminosity of L'(CO(3-2)) = 2.4 x 10(10) K km s(-1) pc(2). For another source at z = 4.17, the lack of detection of the CO(4-3) line suggests the line to have a brightness-temperature luminosity L'(CO(4-3)) < 1 x 10(10) K km s(-1) pc(2). Under the assumption that in these objects the high-J transitions are thermalized, we can estimate the molecular gas contents to be M(II2) = 1.9 x 10(10) M(circle dot) and < 8 x 10(9) M(circle dot), respectively. The estimated gas depletion timescales are tau(g) = 4 Myr and <16 Myr, and low gas-to-dust mass ratios of M(g)/M(d) = 19 and <20 are inferred. These values are at the low end but consistent with those of other high-redshift galaxies.Item The Next Generation Atlas of Quasar Spectral Energy Distributions from Radio To X-Rays(2011-09) Shang, Zhaohui; Brotherton, Michael S.; Wills, Beverley J.; Wills, D.; Cales, Sabrina L.; Dale, Daniel A.; Green, Richard F.; Runnoe, Jessie C.; Nemmen, Rodrigo S.; Gallagher, Sarah C.; Ganguly, Rajib; Hines, Dean C.; Kelly, Benjamin J.; Kriss, Gerard A.; Li, Jun; Tang, Baitian; Xie, Yanxia; Wills, Beverley J.; Wills, D.We have produced the next generation of quasar spectral energy distributions (SEDs), essentially updating the work of Elvis et al. by using high-quality data obtained with several space-and ground-based telescopes, including NASA's Great Observatories. We present an atlas of SEDs of 85 optically bright, non-blazar quasars over the electromagnetic spectrum from radio to X-rays. The heterogeneous sample includes 27 radio-quiet and 58 radio-loud quasars. Most objects have quasi-simultaneous ultraviolet-optical spectroscopic data, supplemented with some far-ultraviolet spectra, and more than half also have Spitzer mid-infrared Infrared Spectrograph spectra. The X-ray spectral parameters are collected from the literature where available. The radio, far-infrared, and near-infrared photometric data are also obtained from either the literature or new observations. We construct composite SEDs for radio-loud and radio-quiet objects and compare these to those of Elvis et al., finding that ours have similar overall shapes, but our improved spectral resolution reveals more detailed features, especially in the mid-and near-infrared.Item Optical Spectroscopy Of X-Ray Sources In The Extended Chandra Deep Field South(2009-03) Treister, Ezequiel; Virani, Shanil; Gawiser, Eric; Urry, C. Megan; Lira, Paulina; Francke, Ilarold; Blanc, Guillermo A.; Cardamone, Carolin N.; Damen, Maaike; Taylor, Edward N.; Schawinski, Kevin; Blanc, Guillermo A.We present the first results of our optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South. A total of 339 sources were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. We measured redshifts for 186 X-ray sources, including archival data and a literature search. We find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley." The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity.Item The Quasar SDSS J105041.35+345631.3: Black Hole Recoil Or Extreme Double-Peaked Emitter?(2009-12) Shields, Gregory A.; Rosario, D. J.; Smith, K. L.; Bonning, E. W.; Salviander, Sarah; Kalirai, J. S.; Strickler, R.; Ramirez-Ruiz, E.; Dutton, A. A.; Treu, T.; Marshall, P. J.; Shields, Gregory A.; Smith, K. L.; Salviander, SarahThe quasar SDSS J105041.35+345631.3 (z = 0.272) has broad emission lines blueshifted by 3500 km s(-1) relative to the narrow lines and the host galaxy. Such an object may be a candidate for a recoiling supermassive black hole, a binary black hole, a superposition of two objects, or an unusual geometry for the broad emission-line region. The absence of narrow lines at the broad line redshift argues against superposition. New Keck spectra of J1050+3456 place tight constraints on the binary model. The combination of large velocity shift and symmetrical H beta profile, as well as aspects of the narrow line spectrum, make J1050+3456 an interesting candidate for black hole recoil. Other aspects of the spectrum, however, suggest that the object is most likely an extreme case of a "double-peaked emitter." We discuss possible observational tests to determine the true nature of this exceptional object.