ABSTRACT We identify 885,503 type 1 quasar candidates to using the combination of optical and mid-IR photometry. Optical photometry is taken from the Sloan Digital Sky Survey-III: Baryon Oscillation ...Spectroscopic Survey (SDSS-III/BOSS), while mid-IR photometry comes from a combination of data from the Wide-field Infrared Survey Explorer (WISE) "AllWISE" data release and several large-area Spitzer Space Telescope fields. Selection is based on a Bayesian kernel density algorithm with a training sample of 157,701 spectroscopically confirmed type 1 quasars with both optical and mid-IR data. Of the quasar candidates, 733,713 lack spectroscopic confirmation (and 305,623 are objects that we have not previously classified as photometric quasar candidates). These candidates include 7874 objects targeted as high-probability potential quasars with (of which 6779 are new photometric candidates). Our algorithm is more complete to than the traditional mid-IR selection "wedges" and to quasars than the SDSS-III/BOSS project. Number counts and luminosity function analysis suggest that the resulting catalog is relatively complete to known quasars and is identifying new high-z quasars at . This catalog paves the way for luminosity-dependent clustering investigations of large numbers of faint, high-redshift quasars and for further machine-learning quasar selection using Spitzer and WISE data combined with other large-area optical imaging surveys.
We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based quasar target selection down to the faint limit of the Sloan Digital Sky Survey (SDSS) catalog, even at medium redshifts ...(2.5 z 3) where the stellar contamination is significant. We build models of the distributions of stars and quasars in flux space down to the flux limit by applying the extreme-deconvolution method to estimate the underlying density. We convolve this density with the flux uncertainties when evaluating the probability that an object is a quasar. This approach results in a targeting algorithm that is more principled, more efficient, and faster than other similar methods. We apply the algorithm to derive low-redshift (z < 2.2), medium-redshift (2.2 <= z <= 3.5), and high-redshift (z>3.5) quasar probabilities for all 160,904,060 point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in the 14,555 deg2 of imaging from SDSS Data Release 8. The catalog can be used to define a uniformly selected and efficient low- or medium-redshift quasar survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic Survey project. We show that the XDQSO technique performs as well as the current best photometric quasar-selection technique at low redshift, and outperforms all other flux-based methods for selecting the medium-redshift quasars of our primary interest. We make code to reproduce the XDQSO quasar target selection publicly available.
We present a detailed study of an unusually bright, lensed galaxy at z = 5.424 discovered within the CFHTLS imaging survey. With an observed flux ofiAB =23.0, J141446.82+544631.9 is one of the ...brightest galaxies known at z > 5. It is characterized by strong Ly α emission, reaching a peak in (observed) flux density of >10−16erg s−1 cm−2Å−1. A deep optical spectrum from the Large Binocular Telescope places strong constraints on NV and C IV emission, disfavouring an Active Galactic Nucleus (AGN) source for the emission. However, a detection of the NIV λ1486 emission line indicates a hard ionizing continuum, possibly from hot, massive stars. Resolved imaging from HST deblends the galaxy from a foreground interloper; these observations include narrowband imaging of the Ly α emission, which is marginally resolved on approximately few kpc scales and has EW0 ∼ 260 Å. The Ly α emission extends over ∼2000 km s−1 and is broadly consistent with expanding shell models. Spectral energy distribution fitting that includes Spitzer/IRAC photometry suggests a complex star formation history that includes both a recent burst and an evolved population. J1414+5446 lies 30 arcsec from the centre of a known lensing cluster in the CFHTLS; combined with the foreground contribution, this leads to a highly uncertain estimate for the lensing magnification in the range 5 μ 25. Because of its unusual brightness, J1414+5446 affords unique opportunities for detailed study of an individual galaxy near the epoch of re-ionization and a preview of what can be expected from upcoming wide-area surveys that will yield hundreds of similar objects.
We report the serendipitous discoveries of companion galaxies to two high-redshift quasars. SDSS J025617.7+001904 is a z = 4.79 quasar included in our recent survey of faint quasars in the SDSS ...Stripe 82 region. The initial MMT slit spectroscopy shows excess Ly alpha emission extending well beyond the quasar's light profile. Further imaging and spectroscopy with LBT/MODS1 confirms the presence of a bright galaxy (i sub(AB) = 23.6) located 2" (12 kpc projected) from the quasar with strong Ly alpha emission (EW sub(0) asymptotically = 100 Angstrom) at the redshift of the quasar, as well as faint continuum. The second quasar, CFHQS J005006.6+344522 (z = 6.25), is included in our recent HST SNAP survey of z ~ 6 quasars searching for evidence of gravitational lensing. Deep imaging with ACS and WFC3 confirms an optical dropout ~4.5 mag fainter than the quasar (Y sub(AB) = 25) at a separation of 0".9. The red i sub(775) - Y sub(105) color of the galaxy and its proximity to the quasar (5 kpc projected if at the quasar redshift) strongly favor an association with the quasar. Although it is much fainter than the quasar, it is remarkably bright when compared to field galaxies at this redshift, while showing no evidence for lensing. Both systems may represent late-stage mergers of two massive galaxies, with the observed light for one dominated by powerful ongoing star formation and for the other by rapid black hole growth. Observations of close companions are rare; if major mergers are primarily responsible for high-redshift quasar fueling then the phase when progenitor galaxies can be observed as bright companions is relatively short.
We present the Data Release 10 Quasar (DR10Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were ...targeted as quasar candidates during the first 2.5 years of the survey and that are confirmed as quasars via visual inspection of the spectra, have luminosities Miz = 2 <−20.5 (in a ΛCDM cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), and either display at least one emission line with a full width at half maximum (FWHM) larger than 500 km s-1 or, if not, have interesting/complex absorption features. The catalog also includes known quasars (mostly from SDSS-I and II) that were reobserved by BOSS. The catalog contains 166 583 quasars (74 454 are new discoveries since SDSS-DR9) detected over 6373 deg2 with robust identification and redshift measured by a combination of principal component eigenspectra. The number of quasars with z > 2.15 (117 668) is ~5 times greater than the number of z > 2.15 quasars known prior to BOSS. Redshifts and FWHMs are provided for the strongest emission lines (C iv, C iii, Mg ii). The catalog identifies 16 461 broad absorption line quasars and gives their characteristics. For each object, the catalog presents five-band (u, g, r, i, z) CCD-based photometry with typical accuracy of 0.03 mag and information on the optical morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. The calibrated digital spectra cover the wavelength region 3600−10 500 Å at a spectral resolution in the range 1300 < R < 2500; the spectra can be retrieved from the SDSS Catalog Archive Server. We also provide a supplemental list of an additional 2376 quasars that have been identified among the galaxy targets of the SDSS-III/BOSS.
We use numerical simulations to investigate the importance of HD formation and cooling on the first generation of metal-free stars in a Lambda CDM cosmology. We have implemented and tested ...non-equilibrium HD chemistry in an adaptive mesh refinement simulation code and applied it to two situations. (1) It is first applied to the formation of 10 super(5)-10 super(6) M sub(image) halos which form in the absence of any ionizing source ('unperturbed' halos). We show, in agreement with previous work, that HD cooling is of only marginal importance for most halos; however, we find that for the lowest mass halos, with masses a few times 10 super(5) M sub(image), HD cooling can equal or surpass the H sub(2) cooling rate. This leads to a population of stars formed in halos with effective HD cooling that are less massive by a factor of image6 compared to halos dominated by H sub(2) cooling. (2) In the second part of the paper, we ionize the halos in order to explore the impact of HD cooling in the presence of an ample population of free electrons. This leads to cooler temperatures (due to the electron-catalyzed production of H sub(2)), implying somewhat lower resulting protostellar mass. Adding HD chemistry changes this by lowering the temperature further, to the level of the CMB. We find that HD cooling dominates over H sub(2) cooling in the density range 10 super(2)-10 super(6) cm super(-3), but above this density, the temperature rises and H sub(2) cooling dominates again. Because of this, the accretion rate on to the protostar is almost the same as in the H sub(2) case (at least for accreted masses below 50-100 M sub(image)); therefore we argue that HD cooling in ionized halos will probably not result in a population of significantly lower mass stars.
We investigate the distribution of companion galaxies around quasars using Hubble Space Telescope (HST) Advanced Camera for Surveys Wide Field Camera (ACS/WFC) archival images. Our master sample ...contains 532 quasars that have been observed by HST ACS/WFC, spanning a wide range of luminosity (−31 < Mi(z = 2) < −23) and redshift (0.3 < z < 3). We search for companions around the quasars with a projected distance of 10 kpc < d < 100 kpc. Point spread function subtraction is performed to enhance the completeness for close companions. The completeness is estimated to be high (>90%) even for the faintest companions of interest. The number of physical companions is estimated by subtracting a background density from the number density of projected companions. We divide all the companions into three groups (faint, intermediate, and bright) according to their fluxes. A control sample of galaxies is constructed to have a similar redshift distribution and stellar mass range as the quasar sample using the data from HST deep fields. We find that quasars and control sample galaxies have similar numbers of faint and bright companions, while quasars show a 3.7 deficit of intermediate companions compared to galaxies. The numbers of companions in all three groups do not show strong evolution with redshift, and the number of intermediate companions around quasars decreases with quasar luminosity. Assuming that merger-triggered quasars have entered the final coalescence stage during which individual companions are no longer detectable at large separations, our result is consistent with a picture in which a significant fraction of quasars is triggered by mergers.
We present a reverberation mapping (RM) experiment that combines broad- and intermediate-band photometry; it is the first such attempt targeting 13 quasars at 0.2 < z < 0.9. The quasars were selected ...to have strong Ha or H beta emission lines that are located in one of three intermediate bands centered at 8045, 8505, and 9171 A. The imaging observations were carried out in the intermediate bands and the broad i and z bands using the prime-focus imager 90Prime on the 2.3 m Bok telescope. The measured lags are consistent with the current BLR size-luminosity relation for H beta at z < 0.3. Finally we demonstrate that, by using a small telescope with a large FOV, intermediate-band photometric RM can be efficiently executed for a large sample of quasars at z > 0.2.
ABSTRACT We report the discovery of an ultra-luminous quasar J030642.51+185315.8 (hereafter J0306+1853) at redshift 5.363, which hosts a supermassive black hole with . With an absolute magnitude and ...a bolometric luminosity , J0306+1853 is one of the most luminous objects in the early universe. It is not likely to be a beamed source based on its small flux variability, low radio loudness, and normal broad emission lines. In addition, a damped Ly system (DLA) with , among the most metal-rich DLAs at , is detected in the absorption spectrum of this quasar. This ultra-luminous quasar puts strong constraints on the bright end of the quasar luminosity function and massive end of the black hole mass function. It will provide a unique laboratory for the study of BH growth and the co-evolution between a BH and the host galaxy with multi-wavelength follow-up observations. The future high-resolution spectra will give more insight into the DLA and other absorption systems along the line of sight of J0306+1853.
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