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Gordon T Richards - One of the best experts on this subject based on the ideXlab platform.
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The SDSS-III Baryon Oscillation Spectroscopic Survey: Quasar Target Selection for Data Release Nine
Astrophysical Journal Supplement, 2012Co-Authors: N.p. Ross, Adam D. Myers, Gordon T Richards, Jo Bovy, Michael A. Strauss, Jessica A Kirkpatrick, Christophe Yeche, E. Aubourg, Erin S. Sheldon, Michael R. BlantonAbstract:The SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), a five-year spectroscopic survey of 10,000 deg2, achieved first light in late 2009. One of the key goals of BOSS is to measure the signature of baryon acoustic oscillations (BAOs) in the distribution of Lyα absorption from the spectra of a sample of ~150,000 z > 2.2 Quasars. Along with measuring the angular diameter distance at z ≈ 2.5, BOSS will provide the first direct measurement of the expansion rate of the universe at z > 2. One of the biggest challenges in achieving this goal is an efficient target selection algorithm for Quasars in the redshift range 2.2 < z < 3.5, where their colors tend to overlap those of the far more numerous stars. During the first year of the BOSS survey, quasar target selection (QTS) methods were developed and tested to meet the requirement of delivering at least 15 Quasars deg-2 in this redshift range, with a goal of 20 out of 40 targets deg-2 allocated to the quasar survey. To achieve these surface densities, the magnitude limit of the quasar targets was set at g 2.20 Quasars were spectroscopically confirmed by BOSS, roughly double the number of previously known Quasars with z > 2.20. Our current algorithms select an average of 15 z > 2.20 Quasars deg-2 from 40 targets deg-2 using single-epoch SDSS imaging. Multi-epoch optical data and data at other wavelengths can further improve the efficiency and completeness of BOSS QTS.
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dust free Quasars in the early universe
Nature, 2010Co-Authors: Linhua Jiang, Gordon T Richards, W. N. Brandt, Michael A. Strauss, C L Carilli, E Egami, Dean C Hines, Jaron Kurk, Yue Shen, M VestergaardAbstract:More than 40 Quasars have been discovered at redshifts of z ≈ 6, at an epoch when the Universe was less than a billion years old or just 7% of its current age. Surprisingly, the properties of these distant Quasars seem almost indistinguishable from those at lower redshifts, suggesting that they are evolved objects. Now with the discovery of a second z ≈ 6 quasar without hot-dust emission, and evidence from others that hot dust accumulates in tandem with the growth of the central black hole, comes confirmation that these extremely distant Quasars are indeed less evolved than their lower-redshift equivalents. The two dust-free Quasars may be first-generation Quasars born in dust-free environments that are too young to have formed a detectable amount of hot dust around them. The most distant Quasars known, at redshifts z ≈ 6, generally have the same properties as lower-redshift Quasars, implying that although the Universe was young at z ≈ 6, such Quasars are still evolved objects. One z ≈ 6 quasar was shown to have no detectable emission from hot dust, but it was not clear whether it was an outlier. Now, a second quasar without hot-dust emission has been discovered in a sample of 21 z ≈ 6 Quasars. Moreover, hot-dust abundance in these Quasars builds up as the central black hole grows. The most distant Quasars known, at redshifts z ≈ 6, generally have properties indistinguishable from those of lower-redshift Quasars in the rest-frame ultraviolet/optical and X-ray bands1,2,3. This puzzling result suggests that these distant Quasars are evolved objects even though the Universe was only seven per cent of its current age at these redshifts. Recently one z ≈ 6 quasar was shown not to have any detectable emission from hot dust4, but it was unclear whether that indicated different hot-dust properties at high redshift or if it is simply an outlier. Here we report the discovery of a second quasar without hot-dust emission in a sample of 21 z ≈ 6 Quasars. Such apparently hot-dust-free Quasars have no counterparts at low redshift. Moreover, we demonstrate that the hot-dust abundance in the 21 Quasars builds up in tandem with the growth of the central black hole, whereas at low redshift it is almost independent of the black hole mass. Thus z ≈ 6 Quasars are indeed at an early evolutionary stage, with rapid mass accretion and dust formation. The two hot-dust-free Quasars are likely to be first-generation Quasars born in dust-free environments and are too young to have formed a detectable amount of hot dust around them.
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EIGHT-DIMENSIONAL MID-INFRARED/OPTICAL BAYESIAN QUASAR SELECTION
The Astronomical Journal, 2009Co-Authors: Gordon T Richards, Randhir P. Deo, Adam D. Myers, William Nielsen Brandt, Mark Lacy, Robert J Brunner, Nadia L Zakamska, Robert C. Nichol, Alexander G. Gray, John K. ParejkoAbstract:We explore the multidimensional, multiwavelength selection of Quasars from mid-infrared (MIR) plus optical data, specifically from Spitzer-Infrared Array Camera (IRAC) and the Sloan Digital Sky Survey (SDSS). Traditionally, quasar selection relies on cuts in two-dimensional color space despite the fact that most modern surveys (optical and IR) are done in more than three bandpasses. In this paper, we apply modern statistical techniques to combined Spitzer MIR and SDSS optical data, allowing up to eight-dimensional (8-D) color selection of Quasars. Using a Bayesian selection method, we catalog 5546 quasar candidates to an 8.0 μm depth of 56 μJy over an area of ~24 deg2. Roughly 70% of these candidates are not identified by applying the same Bayesian algorithm to 4-color SDSS optical data alone. The 8-D optical+MIR selection on this data set recovers 97.7% of known type 1 Quasars in this area and greatly improves the effectiveness of identifying 3.5 < z < 5 Quasars which are challenging to identify (without considerable contamination) using MIR data alone. We demonstrate that, even using only the two shortest wavelength IRAC bandpasses (3.6 and 4.5 μm), it is possible to use our Bayesian techniques to select Quasars with 97% completeness and as little as 10% contamination (as compared to ~60% contamination using color cuts alone). We compute photometric redshifts for our sample; comparison with known objects suggests a photometric redshift accuracy of 93.6% (Δz ± 0.3), remaining roughly constant when the two reddest MIR bands are excluded. Despite the fact that our methods are designed to find type 1 (unobscured) Quasars, as many as 1200 of the objects are type 2 (obscured) quasar candidates. Coupling deep optical imaging data, with deep MIR data, could enable selection of Quasars in significant numbers past the peak of the quasar luminosity function (QLF) to at least z ~ 4. Such a sample would constrain the shape of the QLF both above and below the break luminosity (L* Q ) and enable quasar clustering studies over the largest range of redshift and luminosity to date, yielding significant gains in our understanding of the physics of Quasars and their contribution to galaxy evolution.
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the small scale environment of Quasars
The Astrophysical Journal, 2006Co-Authors: W Serber, Neta A Bahcall, Brice Menard, Gordon T RichardsAbstract:Where do Quasars reside? Are Quasars located in environments similar to those of typical L* galaxies, and, if not, how do they differ? An answer to this question will help shed light on the triggering process of quasar activity. We use the Sloan Digital Sky Survey to study the environment of Quasars and compare it directly with the environment of galaxies. We find that Quasars (Mi ? -22, z ? 0.4) are located in higher local overdensity regions than are typical L* galaxies. The enhanced environment around Quasars is a local phenomenon; the overdensity relative to that around L* galaxies is strongest within 100 kpc of the Quasars. In this region, the overdensity is a factor of 1.4 larger than around L* galaxies. The overdensity declines monotonically with scale to nearly unity at ~1 h Mpc, where Quasars inhabit environments comparable to those of L* galaxies. The small-scale density enhancement depends on quasar luminosity, but only at the brightest end: the most luminous Quasars reside in higher local overdensity regions than do fainter Quasars. The mean overdensity around the brightest Quasars (Mi ? -23.3) is nearly 3 times larger than around L* galaxies, while the density around dimmer Quasars (Mi = -22.0 to -23.3) is ~1.4 times that of L* galaxies. By ~0.5 Mpc, the dependence on quasar luminosity is no longer significant. The overdensity on all scales is independent of redshift to z ? 0.4. The results suggest a picture in which Quasars typically reside in L* galaxies but have a local excess of neighbors within ~0.1-0.5 Mpc; this local density excess likely contributes to the triggering of quasar activity through mergers and other interactions.
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The Small-Scale Environment of Quasars
The Astrophysical Journal, 2006Co-Authors: W Serber, Neta A Bahcall, Brice Menard, Gordon T RichardsAbstract:Where do Quasars reside? Are Quasars located in environments similar to those of typical L* galaxies, and, if not, how do they differ? An answer to this question will help shed light on the triggering process of quasar activity. We use the Sloan Digital Sky Survey to study the environment of Quasars and compare it directly with the environment of galaxies. We find that Quasars (M_i < -22, z < 0.4) are located in higher local overdensity regions than are typical L* galaxies. The enhanced environment around Quasars is a local phenomenon; the overdensity relative to that around L* galaxies is strongest within 100 kpc of the Quasars. In this region, the overdensity is a factor of 1.4 larger than around L* galaxies. The overdensity declines monotonically with scale to nearly unity at ~1 Mpc, where Quasars inhabit environments comparable to those of L* galaxies. The small-scale density enhancement depends on quasar luminosity, but only at the brightest end: the most luminous Quasars reside in higher local overdensity regions than do fainter Quasars. The mean overdensity around the brightest Quasars (M_i < -23.3) is nearly three times larger than around L* galaxies while the density around dimmer Quasars (M_i = -22.0 to -23.3) is ~1.4 times that of L* galaxies. By ~0.5 Mpc, the dependence on quasar luminosity is no longer significant. The overdensity on all scales is independent of redshift to z = 0.4. The results suggest a picture in which Quasars typically reside in L* galaxies, but have a local excess of neighbors within ~0.1 - 0.5 Mpc; this local density excess likely contributes to the triggering of quasar activity through mergers and other interactions.
Xiaohui Fan - One of the best experts on this subject based on the ideXlab platform.
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the extremely luminous quasar survey in the pan starrs 1 footprint ps elqs
arXiv: Astrophysics of Galaxies, 2019Co-Authors: Jan Torge Schindler, Patrick B. Hall, Xiaohui Fan, Yun Hsin Huang, Minghao Yue, Jinyi Yang, Lukas Wenzl, Allison Hughes, Katrina C Litke, Jon M ReesAbstract:We present the results of the Extremely Luminous Quasar Survey in the $3\pi$ survey of the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS; PS1). This effort applies the successful quasar selection strategy of the Extremely Luminous Survey in the Sloan Digital Sky Survey footprint ($\sim12,000\,\rm{deg}^2$) to a much larger area ($\sim\rm{21486}\,\rm{deg}^2$). This spectroscopic survey targets the most luminous Quasars ($M_{1450}\le-26.5$; $m_{i}\le18.5$) at intermediate redshifts ($z\ge2.8$). Candidates are selected based on a near-infrared JKW2 color cut using WISE AllWISE and 2MASS photometry to mainly reject stellar contaminants. Photometric redshifts ($z_{\rm{reg}}$) and star-quasar classifications for each candidate are calculated from near-infrared and optical photometry using the supervised machine learning technique random forests. We select 806 quasar candidates at $z_{\rm{reg}}\ge2.8$ from a parent sample of 74318 sources. After exclusion of known sources and rejection of candidates with unreliable photometry, we have taken optical identification spectra for 290 of our 334 good PS-ELQS candidates. We report the discovery of 190 new $z\ge2.8$ Quasars and an additional 28 Quasars at lower redshifts. A total of 44 good PS-ELQS candidates remain unobserved. Including all known Quasars at $z\ge2.8$, our quasar selection method has a selection efficiency of at least $77\%$. At lower declinations $-30\le\rm{Decl.}\le0$ we approximately triple the known population of extremely luminous Quasars. We provide the PS-ELQS quasar catalog with a total of 592 luminous Quasars ($m_{i}\le18.5$, $z\ge2.8$). This unique sample will not only be able to provide constraints on the volume density and quasar clustering of extremely luminous Quasars, but also offers valuable targets for studies of the intergalactic medium.
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the extremely luminous quasar survey in the sloan digital sky survey footprint iii the south galactic cap sample and the quasar luminosity function at cosmic noon
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Jan Torge Schindler, Xiaohui Fan, Jinyi Yang, Ian D Mcgreer, Feige Wang, Richard F Green, J P U Fynbo, Jens Kristian Krogager, E M Green, Yun Hsin HuangAbstract:We have designed the Extremely Luminous Quasar Survey (ELQS) to provide a highly complete census of unobscured UV-bright Quasars during the cosmic noon, $z=2.8-5.0$. Here we report the discovery of 70 new Quasars in the ELQS South Galactic Cap (ELQS-S) quasar sample, doubling the number of known extremely luminous Quasars in $4,237.3\,\rm{deg}^2$ of the SDSS footprint. These observations conclude the ELQS and we present the properties of the full ELQS quasar catalog, containing 407 Quasars over $11,838.5\,\rm{deg}^2$. Our novel ELQS quasar selection strategy resulted in unprecedented completeness at the bright end and allowed us to discover 109 new Quasars in total. This marks an increase of $\sim36\%$ (109/298) to the known population at these redshifts and magnitudes, while we further are able to retain a selection efficiency of $\sim80\%$. On the basis of 166 Quasars from the full ELQS quasar catalog, who adhere to the uniform criteria of the 2MASS point source catalog, we measure the bright-end quasar luminosity function (QLF) and extend it one magnitude brighter than previous studies. Assuming a single power law with exponential density evolution for the functional form of the QLF, we retrieve the best fit parameters from a maximum likelihood analysis. We find a steep bright-end slope of $\beta\approx-4.1$ and we can constrain the bright-end slope to $\beta\leq-3.4$ with $99\%$ confidence. The density is well modeled by the exponential redshift evolution, resulting in a moderate decrease with redshift ($\gamma\approx-0.4$).
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the pan starrs1 distant z 5 6 quasar survey more than 100 Quasars within the first gyr of the universe
Astrophysical Journal Supplement Series, 2016Co-Authors: Xiaohui Fan, Roberto Decarli, Eduardo Banados, B P Venemans, Emanuele Paolo Farina, Chiara Mazzucchelli, Frederick M Walter, Daniel Stern, Edward F SchlaflyAbstract:Luminous Quasars at z > 5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far, these studies have been statistically limited by the number of Quasars known at these redshifts. Such Quasars are rare, and therefore, wide-field surveys are required to identify them, and multiwavelength data are required to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for the z ~ 6 Quasars presented in Banados et al. (2014) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 Quasars in the redshift range 5.6 ≾ z ≾ 6.7 that satisfy our selection criteria. Of these Quasars, 77 have been discovered with PS1, and 63 of them are newly identified in this paper. We present the composite spectra of the PS1 distant quasar sample. This sample spans a factor of ~20 in luminosity and shows a variety of emission line properties. The number of Quasars at z > 5.6 presented in this work almost doubles the previously known Quasars at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.
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the final sdss high redshift quasar sample of 52 Quasars at z 5 7
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Linhua Jiang, Robert H. Becker, Xiaohui Fan, M Strauss, Ian D Mcgreer, Eduardo Banados, Fuyan Bian, Kara Farnsworth, Yue ShenAbstract:We present the discovery of nine Quasars at $z\sim6$ identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of $z\sim6$ Quasars in the SDSS footprint. Our final sample consists of 52 Quasars at $5.7
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the pan starrs1 distant z 5 6 quasar survey more than 100 Quasars within the first gyr of the universe
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Xiaohui Fan, Roberto Decarli, Eduardo Banados, B P Venemans, Emanuele Paolo Farina, Chiara Mazzucchelli, Frederick M Walter, Daniel Stern, Edward F SchlaflyAbstract:Luminous Quasars at z>5.6 can be studied in detail with the current generation of telescopes and provide us with unique information on the first gigayear of the universe. Thus far these studies have been statistically limited by the number of Quasars known at these redshifts. Such Quasars are rare and therefore wide-field surveys are required to identify them and multiwavelength data are needed to separate them efficiently from their main contaminants, the far more numerous cool dwarfs. In this paper, we update and extend the selection for z~6 Quasars presented in Banados et al. (2014) using the Pan-STARRS1 (PS1) survey. We present the PS1 distant quasar sample, which currently consists of 124 Quasars in the redshift range 5.6 5.6 presented in this work almost double the Quasars previously known at these redshifts, marking a transition phase from studies of individual sources to statistical studies of the high-redshift quasar population, which was impossible with earlier, smaller samples.
Donald P. Schneider - One of the best experts on this subject based on the ideXlab platform.
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the correlations between optical uv broad lines and x ray emission for a large sample of Quasars
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: John D Timlin, W. N. Brandt, Donald P. Schneider, Bin Luo, M VivekAbstract:We present Chandra observations of 2106 radio-quiet Quasars in the redshift range 1.7 99.99% level) between $\alpha_{ox}$ and these emission-line parameters, as well as between $\Delta\alpha_{ox}$ and CIV EW. Slight correlations are found between $\Delta\alpha_{ox}$ and CIV blueshift, MgII EW, and the CIV EW to MgII EW ratio. The best-fit trend in each parameter space is used to compare the X-ray weakness ($\Delta\alpha_{ox}$) and optical/UV emission properties of typical Quasars and weak-line Quasars (WLQs). The WLQs typically exhibit weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical Quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs compared to our typical Quasars can be explained by an X-ray "shielding" model.
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photometric redshifts and quasar probabilities from a single data driven generative model
arXiv: Cosmology and Nongalactic Astrophysics, 2011Co-Authors: Jo Bovy, Adam D. Myers, Joseph F. Hennawi, David W. Hogg, R G Mcmahon, Erin S. Sheldon, David Schiminovich, Jon Brinkmann, Donald P. SchneiderAbstract:We describe a technique for simultaneously classifying and estimating the redshift of Quasars. It can separate Quasars from stars in arbitrary redshift ranges, estimate full posterior distribution functions for the redshift, and naturally incorporate flux uncertainties, missing data, and multi-wavelength photometry. We build models of Quasars in flux-redshift space by applying the extreme deconvolution technique to estimate the underlying density. By integrating this density over redshift one can obtain quasar flux-densities in different redshift ranges. This approach allows for efficient, consistent, and fast classification and photometric redshift estimation. This is achieved by combining the speed obtained by choosing simple analytical forms as the basis of our density model with the flexibility of non-parametric models through the use of many simple components with many parameters. We show that this technique is competitive with the best photometric quasar classification techniques---which are limited to fixed, broad redshift ranges and high signal-to-noise ratio data---and with the best photometric redshift techniques when applied to broadband optical data. We demonstrate that the inclusion of UV and NIR data significantly improves photometric quasar--star separation and essentially resolves all of the redshift degeneracies for Quasars inherent to the ugriz filter system, even when included data have a low signal-to-noise ratio. For Quasars spectroscopically confirmed by the SDSS 84 and 97 percent of the objects with GALEX UV and UKIDSS NIR data have photometric redshifts within 0.1 and 0.3, respectively, of the spectroscopic redshift; this amounts to about a factor of three improvement over ugriz-only photometric redshifts. Our code to calculate quasar probabilities and redshift probability distributions is publicly available.
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Quasars Probing Quasars I: Optically Thick Absorbers Near Luminous Quasars
The Astrophysical Journal, 2006Co-Authors: Joseph F. Hennawi, Gordon T Richards, Nadia L Zakamska, Jason X. Prochaska, Scott Burles, Michael A. Strauss, David J. Schlegel, Xiaohui Fan, Donald P. Schneider, Masamune OguriAbstract:With close pairs of Quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We search 149 moderate resolution background quasar spectra, from Gemini, Keck, the MMT, and the SDSS to survey Lyman Limit Systems (LLSs) and Damped Ly-alpha systems (DLAs) in the vicinity of 1.8 10^19. The covering factor of log N_HI > 10^19 absorbers is thus ~ 50 % (4/8) on these small scales, whereas < 2% would have been expected at random. There are many cosmological applications of these new sightlines: they provide laboratories for studying fluorescent Ly-alpha recombination radiation from LLSs, constrain the environments, emission geometry, and radiative histories of Quasars, and shed light on the physical nature of LLSs and DLAs.
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a survey of z 5 7 Quasars in the sloan digital sky survey ii discovery of three additional Quasars at z 6
The Astronomical Journal, 2003Co-Authors: Robert H. Becker, Richard L. White, Xiaohui Fan, Donald P. Schneider, M Strauss, Michael D. Gregg, Zoltan HaimanAbstract:We present the discovery of three new Quasars at z > 6 in ~ 1300 deg2 of Sloan Digital Sky Survey imaging data, J114816.64+525150.3 (z = 6.43), J104845.05+463718.3 (z = 6.23), and J163033.90+401209.6 (z = 6.05). The first two objects have weak Lyα emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to ~0.05 and could be affected by the presence of broad absorption line systems. The last object has a Lyα strength more typical of lower redshift Quasars. Based on a sample of six Quasars at z > 5.7 that cover 2870 deg2 presented in this paper and in Paper I, we estimate the comoving density of luminous Quasars at z ~ 6 and M1450 5.7 Quasars and high-resolution, ground-based images (seeing ~04) of three additional z > 5.7 Quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshift quasar sample suggests the bright-end slope of the quasar luminosity function at z ~ 6 is shallower than Ψ ∝ L-3.5 (2 σ), consistent with the absence of strongly lensed objects.
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a survey of z 5 7 Quasars in the sloan digital sky survey ii discovery of three additional Quasars at z 6
arXiv: Astrophysics, 2003Co-Authors: Xiaohui Fan, Robert H. Becker, Richard L. White, Donald P. Schneider, M Strauss, Laura Pentericci, Zoltan Haiman, M D Gregg, Eva K Grebe, Vijay K NarayananAbstract:We present the discovery of three new Quasars at z>6 in 1300 deg^2 of SDSS imaging data, J114816.64+525150.3 (z=6.43), J104845.05+463718.3 (z=6.23) and J163033.90+401209.6 (z=6.05). The first two objects have weak Ly alpha emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to 0.05 and could be affected by the presence of broad absorption line systems. The last object has a Ly alpha strength more typical of lower redshift Quasars. Based on a sample of six Quasars at z>5.7 that cover 2870 deg^2 presented in this paper and in Paper I, we estimate the comoving density of luminous Quasars at z 6 and M_{1450} 5.7 Quasars and high-resolution ground-based images (seeing 0.4'') of three additional z>5.7 Quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshfit quasar sample suggests the bright end slope of the quasar luminosity function at z 6 is shallower than Psi L^{-3.5} (2-sigma), consistent with the absence of strongly lensed objects.
Adam D. Myers - One of the best experts on this subject based on the ideXlab platform.
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Quasars probing Quasars X: The quasar pair spectral database
The Astrophysical Journal Supplement Series, 2018Co-Authors: Joseph R. Findlay, Adam D. Myers, J. Xavier Prochaska, Joseph F. Hennawi, Michele Fumagalli, Stephanie Bartle, Ben Chehade, M. A. Dipompeo, Tom Shanks, Marie Wingyee LauAbstract:The rare close projection of two Quasars on the sky provides the opportunity to study the host galaxy environment of a foreground quasar in absorption against the continuum emission of a background quasar. For over a decade the "Quasars probing Quasars" series has utilized this technique to further the understanding of galaxy formation and evolution in the presence of a quasar at z>2, resolving scales as small as a galactic disc and from bound gas in the circumgalactic medium to the diffuse environs of intergalactic space. Presented here, is the public release of the quasar pair spectral database utilized in these studies. In addition to projected pairs at z>2, the database also includes quasar pair members at z
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THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: QUASAR TARGET SELECTION
Astrophysical Journal Supplement, 2015Co-Authors: Adam D. Myers, Jo Bovy, David J. Schlegel, Nathalie Palanque-delabrouille, Abhishek Prakash, Isabelle Pâris, Christophe Yeche, Kyle S. Dawson, Dustin Lang, Jeffrey A. NewmanAbstract:As part of the Sloan Digital Sky Survey (SDSS) IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will improve measurements of the cosmological distance scale by applying the Baryon Acoustic Oscillation (BAO) method to quasar samples. eBOSS will adopt two approaches to target Quasars over 7500 deg(2). First, a “CORE” quasar sample will combine the optical selection in ugriz using a likelihood-based routine called XDQSOz, with a mid-IR-optical color cut. eBOSS CORE selection (to g \textless 22 or r \textless 22) should return similar to 70 deg(-2) Quasars at redshifts 0.9 \textless z \textless 2.2 and similar to 7 deg(-2)z \textgreater 2.1 Quasars. Second, a selection based on variability in multi-epoch imaging from the Palomar Transient Factory should recover an additional similar to 3-4 deg(-2)z \textgreater 2.1 Quasars to g \textless 22.5 A linear model of how imaging systematics affect target density recovers the angular distribution of eBOSS CORE Quasars over 96.7% (76.7%) of the SDSS north (south) Galactic Cap area. The eBOSS CORE quasar sample should thus be sufficiently dense and homogeneous over 0.9. \textless. z. \textless. 2.2 to yield the first few-percent-level BAO constraint near \textless(z)over bar\textgreater similar to 1.5. eBOSS Quasars at z \textgreater 2.1 will be used to improve BAO measurements in the Ly alpha Forest. Beyond its key cosmological goals, eBOSS should be the next-generation quasar survey, comprising \textgreater 500,000 new Quasars and \textgreater500,000 uniformly selected spectroscopically confirmed 0.9 \textless z \textless 2.2 Quasars. At the conclusion of eBOSS, the SDSS will have provided unique spectra for more than 800,000 Quasars.
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cross correlation of sdss dr7 Quasars and dr10 boss galaxies the weak luminosity dependence of quasar clustering at z 0 5
The Astrophysical Journal, 2013Co-Authors: Adam D. Myers, Yue Shen, Cameron K Mcbride, Martin White, Zheng Zheng, Hong Guo, Jessica A KirkpatrickAbstract:We present the measurement of the two-point cross-correlation function (CCF) of 8198 Sloan Digital Sky Survey Data Release 7 Quasars and 349,608 Data Release 10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey at 0.3 Mi (z = 2) > –25.5, implying a weak luminosity dependence of clustering for luminous Quasars at . We compare our measurements with theoretical predictions, halo occupation distribution (HOD) models, and mock catalogs. These comparisons suggest that Quasars reside in a broad range of host halos. The host halo mass distributions significantly overlap with each other for Quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different satellite fractions and host halo mass distributions. These results highlight the limitations and ambiguities in modeling the distribution of Quasars with the standard HOD approach.
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Quasars Probing Quasars. VI. Excess H I Absorption within One Proper Mpc of z ~ 2 Quasars
The Astrophysical Journal, 2013Co-Authors: J. Xavier Prochaska, Joseph F. Hennawi, K. J. Lee, Sebastiano Cantalupo, Jo Bovy, S. G. Djorgovski, Sara L. Ellison, Marie Wingyee Lau, Crystal L. Martin, Adam D. MyersAbstract:With close pairs of Quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ~ 2 Quasars at proper separations of 30 kpc 10^(17.3) cm^(-2) at separations R_⊥ < 200 kpc, which decreases to ~20% at R_⊥ ≃ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ_(QA)(r) = (r/r_0)^γ with a large correlation length r_0=12.5^(+2.7)_(-1.4)h^(-1)Mpc(comoving) and y =1.68^(+0.14)_(-0.30). The H I absorption measured around Quasars exceeds that of any previously studied population, consistent with Quasars being hosted by massive dark matter halos M_(halo) ≈ 10^(12.5) M_☉ at z ~ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ~ 2.5. The anisotropic absorption around Quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.
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cross correlation of sdss dr7 Quasars and dr10 boss galaxies the weak luminosity dependence of quasar clustering at z 0 5
arXiv: Cosmology and Nongalactic Astrophysics, 2012Co-Authors: Adam D. Myers, Yue Shen, Cameron K Mcbride, Martin White, Zheng Zheng, Hong Guo, Jessica A KirkpatrickAbstract:We present the measurement of the two-point cross-correlation function (CCF) of 8,198 Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) Quasars and 349,608 DR10 CMASS galaxies from the Baryonic Oscillation Spectroscopic Survey (BOSS) at redshift ~0.5 (0.3 =0.53 from the CCF measurements. This linear bias corresponds to a characteristic host halo mass of ~4x10^12 M_sun/h, compared to ~10^13 M_sun/h characteristic host halo mass for CMASS galaxies. We divide the quasar sample in luminosity and constrain the luminosity dependence of quasar bias to be db_Q/dlogL=0.20+-0.34 or 0.11+-0.32 (depending on different luminosity divisions) for quasar luminosities -23.5>M_i(z=2)>-25.5, implying a weak luminosity dependence of quasar clustering for the bright end of the quasar population at ~0.5. We compare our measurements with theoretical predictions, Halo Occupation Distribution (HOD) models and mock catalogs. These comparisons suggest Quasars reside in a broad range of host halos, and the host halo mass distributions significantly overlap with each other for Quasars at different luminosities, implying a poor correlation between halo mass and instantaneous quasar luminosity. We also find that the quasar HOD parameterization is largely degenerate such that different HODs can reproduce the CCF equally well, but with different outcomes such as the satellite fraction and host halo mass distribution. These results highlight the limitations and ambiguities in modeling the distribution of Quasars with the standard HOD approach and the need for additional information in populating Quasars in dark matter halos with HOD. [Abridged]
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the final sdss high redshift quasar sample of 52 Quasars at z 5 7
arXiv: Astrophysics of Galaxies, 2016Co-Authors: Linhua Jiang, Robert H. Becker, Xiaohui Fan, M Strauss, Ian D Mcgreer, Eduardo Banados, Fuyan Bian, Kara Farnsworth, Yue ShenAbstract:We present the discovery of nine Quasars at $z\sim6$ identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of $z\sim6$ Quasars in the SDSS footprint. Our final sample consists of 52 Quasars at $5.7
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Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
The Astrophysical Journal, 2008Co-Authors: Tanya Urrutia, Mark Lacy, Robert H. BeckerAbstract:We present Hubble Space Telescope ACS images of 13 dust-reddened type 1 Quasars selected from the FIRST/2MASS Red Quasar Survey. These Quasars have high intrinsic luminosities after correction for dust obscuration (–23.5 ≥ M_B ≥ − 26.2 from K-magnitude). The images show strong evidence of recent or ongoing interaction in 11 of the 13 cases, even before the quasar nucleus is subtracted. None of the host galaxies are well fit by a simple elliptical profile. The fraction of Quasars showing interaction is significantly higher than the 30% seen in samples of host galaxies of normal, unobscured Quasars. There is a weak correlation between the amount of dust reddening and the magnitude of interaction in the host galaxy, measured using the Gini coefficient and the concentration index. Although few host galaxy studies of normal Quasars are matched to ours in intrinsic quasar luminosity, no evidence has been found for a strong dependence of merger activity on host luminosity in samples of the host galaxies of normal Quasars. We thus believe that the high merger fraction in our sample is related to their obscured nature, with a significant amount of reddening occurring in the host galaxy. The red quasar phenomenon seems to have an evolutionary explanation, with the young quasar spending the early part of its lifetime enshrouded in an interacting galaxy. This might be further indication of a link between AGNs and starburst galaxies.
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FR II Broad Absorption Line Quasars and the Life Cycle of Quasars
The Astrophysical Journal, 2006Co-Authors: Michael D. Gregg, Robert H. Becker, Willem De VriesAbstract:By combining the Sloan Digitized Sky Survey Third Data Release quasar list with the VLA FIRST survey, we have identified five objects having both broad absorption lines in their optical spectra and FR-II radio morphologies. We identify an additional example of this class from the FIRST Bright Quasar Survey, J1408+3054. Including the original FR-II-BAL object, J1016+5209, brings the number of such objects to eight. These Quasars are relatively rare; finding this small handful has required the 45,000-large quasar sample of SDSS. The FR-II-BAL Quasars exhibit a significant anti-correlation between radio-loudness and the strength of the BAL features. This is easily accounted for by the evolutionary picture in which Quasars emerge from cocoons of BAL-producing material which stifle the development of radio jets and lobes. There is no such simple explanation for the observed properties of FR-II-BALs in the unification-by-orientation model of Quasars. The rarity of the FR-II-BAL class implies that the two phases do not coexist for very long in a single quasar, perhaps less than 10{sup 5} years, with the combined FR-II, high ionization broad absorption phase being even shorter by another factor of 10 or more.
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Double Lobed Radio Quasars from the Sloan Digital Sky Survey
The Astronomical Journal, 2006Co-Authors: W. H. De Vries, Robert H. Becker, Richard L. WhiteAbstract:We have combined a sample of 44 984 Quasars, selected from the Sloan Digital Sky Survey (SDSS) Data Release 3, with the FIRST radio survey. Using a novel technique where the optical quasar position is matched to the complete radio environment within 450'', we are able to characterize the radio morphological make-up of what is essentially an optically selected quasar sample, regardless of whether the quasar (nucleus) itself has been detected in the radio. About 10% of the quasar population have radio cores brighter than 0.75 mJy at 1.4 GHz, and 1.7% have double lobed FR2-like radio morphologies. About 75% of the FR2 sources have a radio core (> 0.75mJy). A significant fraction ({approx}40%) of the FR2 Quasars are bent by more than 10 degrees, indicating either interactions of the radio plasma with the ICM or IGM. We found no evidence for correlations with redshift among our FR2 Quasars: radio lobe flux densities and radio source diameters of the Quasars have similar distributions at low (mean 0.77) and high (mean 2.09) redshifts. Using a smaller high reliability FR2 sample of 422 Quasars and two comparison samples of radio-quiet and non-FR2 radio-loud Quasars, matched in their redshift distributions, we constructed compositemore » optical spectra from the SDSS spectroscopic data. Based on these spectra we can conclude that the FR2 Quasars have stronger high-ionization emission lines compared to both the radio quiet and non-FR2 radio loud sources. This is consistent with the notion that the emission lines are brightened by ongoing shock ionization of ambient gas in the quasar host as the radio source expands.« less
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a survey of z 5 7 Quasars in the sloan digital sky survey ii discovery of three additional Quasars at z 6
The Astronomical Journal, 2003Co-Authors: Robert H. Becker, Richard L. White, Xiaohui Fan, Donald P. Schneider, M Strauss, Michael D. Gregg, Zoltan HaimanAbstract:We present the discovery of three new Quasars at z > 6 in ~ 1300 deg2 of Sloan Digital Sky Survey imaging data, J114816.64+525150.3 (z = 6.43), J104845.05+463718.3 (z = 6.23), and J163033.90+401209.6 (z = 6.05). The first two objects have weak Lyα emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to ~0.05 and could be affected by the presence of broad absorption line systems. The last object has a Lyα strength more typical of lower redshift Quasars. Based on a sample of six Quasars at z > 5.7 that cover 2870 deg2 presented in this paper and in Paper I, we estimate the comoving density of luminous Quasars at z ~ 6 and M1450 5.7 Quasars and high-resolution, ground-based images (seeing ~04) of three additional z > 5.7 Quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshift quasar sample suggests the bright-end slope of the quasar luminosity function at z ~ 6 is shallower than Ψ ∝ L-3.5 (2 σ), consistent with the absence of strongly lensed objects.
