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113
Jul 20, 2013
07/13
by
Xiaohui Fan
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eye 113
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We present a simulation of the spatial, luminosity and spectral distributions of four types of stellar objects. We simulate: (1) Galactic stars, based on a Galactic structure model, a stellar population synthesis model, stellar isochrones, and stellar spectral libraries; (2) white dwarfs, based on model atmospheres, the observed luminosity function, mass distribution, and Galactic distribution of white dwarfs; (3) quasars, based on their observed luminosity function and its evolution, and...
Source: http://arxiv.org/abs/astro-ph/9902063v1
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53
Sep 23, 2013
09/13
by
SDSS Collaboration; Xiaohui Fan
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eye 53
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This is the second paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from ~250 deg^2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of sky. Our success rate of identifying high-redshift quasars is...
Source: http://arxiv.org/abs/astro-ph/9909169v2
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41
Sep 23, 2013
09/13
by
SDSS Collaboration; Xiaohui Fan
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eye 41
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This paper describes the discovery of seven dwarf objects of spectral type `L' (objects cooler than the latest M dwarfs) in commissioning imaging data taken by the Sloan Digital Sky Survey (SDSS). Low-resolution spectroscopy shows that these objects have spectral types from L0 to L8. Comparison of the SDSS and 2MASS photometry for several of these objects indicates the presence of significant opacity at optical wavelengths, perhaps due to atmospheric dust. This comparison also demonstrates the...
Source: http://arxiv.org/abs/astro-ph/9909263v1
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43
Jul 20, 2013
07/13
by
SDSS Collaboration; Xiaohui Fan
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eye 43
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We report observations of a luminous unresolved object at redshift z = 4.62, with a featureless optical spectrum redward of the Lyman alpha forest region, discovered from Sloan Digital Sky Survey (SDSS) commissioning data. The redshift is determined by the onset of the Lyman-alpha forest at lambda ~ 6800 A, and a Lyman Limit System at lambda = 5120 A. A strong Ly_alpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum...
Source: http://arxiv.org/abs/astro-ph/9910001v1
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44
Sep 19, 2013
09/13
by
Neta A. Bahcall; Xiaohui Fan
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eye 44
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How much matter is there in the universe? Does the universe have the critical density needed to stop its expansion, or is the universe underweight and destined to expand forever? We show that several independent measures, especially those utilizing the largest bound systems known - clusters of galaxies - all indicate that the mass-density of the universe is insufficient to halt the expansion. A promising new method, the evolution of the number density of clusters with time, provides the most...
Source: http://arxiv.org/abs/astro-ph/9804082v1
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47
Sep 22, 2013
09/13
by
Nickolay Y. Gnedin; Xiaohui Fan
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eye 47
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We show that numerical simulations of reionization that resolve the Lyman Limit systems (and, thus, correctly count absorptions of ionizing photons) have converged to about 10% level for 5
Source: http://arxiv.org/abs/astro-ph/0603794v1
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48
Sep 18, 2013
09/13
by
Neta A. Bahcall; Xiaohui Fan
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eye 48
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The existence of the three most massive clusters of galaxies observed so far at z>0.5 is used to constrain the mass density parameter of the universe, Omega, and the amplitude of mass fluctuations, sigma_8. We find Omega=0.2 (+0.3,-0.1), and sigma_8=1.2 (+0.5,-0.4) (95 %). We show that the existence of even the single most distant cluster at z=0.83, MS1054-03, with its large gravitational lensing mass, high temperature, and large velocity dispersion, is sufficient to establish powerful...
Source: http://arxiv.org/abs/astro-ph/9803277v1
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45
Sep 20, 2013
09/13
by
Linhua Jiang; Xiaohui Fan; M. Vestergaard
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We report on 293 quasars with strong NIV] lambda 1486 or NIII] lambda 1750 emission lines (rest-frame equivalent width > 3 \AA) at 1.7 < z < 4.0 selected from the Sloan Digital Sky Survey (SDSS) Fifth Data Release. These nitrogen-rich (N-rich) objects comprise ~1.1% of the SDSS quasars. The comparison between the N-rich quasars and other quasars shows that the two quasar subsets share many common properties. We also confirm previous results that N-rich quasars have much stronger Lya...
Source: http://arxiv.org/abs/0802.4234v1
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54
Sep 21, 2013
09/13
by
Xiaohui Fan; C. L. Carilli; B. Keating
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eye 54
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Recent observations have set the first constraints on the epoch of reionization (EoR), corresponding to the formation epoch of the first luminous objects. Studies of Gunn-Peterson (GP) absorption, and related phenomena, suggest a qualitative change in the state of the intergalactic medium (IGM) at $z \sim 6$, indicating a rapid increase in the neutral fraction of the IGM, from $x_{HI} < 10^{-4}$ at $z \le 5.5$, to $x_{HI} > 10^{-3}$, perhaps up to 0.1, at $z \ge 6$. Conversely,...
Source: http://arxiv.org/abs/astro-ph/0602375v2
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55
Sep 22, 2013
09/13
by
Ian D. McGreer; Andrei Mesinger; Xiaohui Fan
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eye 55
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Cosmic reionization is expected to be complex, extended and very inhomogeneous. Existing constraints at z~6 on the volume-averaged neutral hydrogen fraction, , are highly model-dependent and controversial. Constraints at z
Source: http://arxiv.org/abs/1101.3314v1
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47
Sep 22, 2013
09/13
by
Brandon C. Kelly; Marianne Vestergaard; Xiaohui Fan
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eye 47
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We describe a Bayesian approach to estimating quasar black hole mass functions (BHMF) when using the broad emission lines to estimate black hole mass. We show how using the broad line mass estimates in combination with statistical techniques developed for luminosity function estimation leads to statistically biased results. We derive the likelihood function for the BHMF based on the broad line mass estimates, and derive the posterior distribution for the BHMF, given the observed data. We...
Source: http://arxiv.org/abs/0811.2001v1
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49
Sep 22, 2013
09/13
by
Brandon C. Kelly; Xiaohui Fan; Marianne Vestergaard
texts
eye 49
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We describe a Bayesian approach to estimating luminosity functions. We derive the likelihood function and posterior probability distribution for the luminosity function, given the observed data, and we compare the Bayesian approach with maximum-likelihood by simulating sources from a Schechter function. For our simulations confidence intervals derived from bootstrapping the maximum-likelihood estimate can be too narrow, while confidence intervals derived from the Bayesian approach are valid. We...
Source: http://arxiv.org/abs/0805.2946v1
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67
Sep 19, 2013
09/13
by
Xiaohui Fan; Neta A. Bahcall; Renyue Cen
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eye 67
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We present a method for determining the rms mass fluctuations on 8 h^-1 Mpc scale, sigma8. The method utilizes the rate of evolution of the abundance of rich clusters of galaxies. Using the Press-Schechter approximation, we show that the cluster abundance evolution is a strong function of sigma8: d log n/dz ~ -1/sigma8^2; low sigma8 models evolve exponentially faster than high sigma8 models, for a given mass cluster. For example, the number density of Coma-like clusters decreases by a factor of...
Source: http://arxiv.org/abs/astro-ph/9709265v1
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6.0
Jun 29, 2018
06/18
by
Ian McGreer; Sarah Eftekharzadeh; Adam Myers; Xiaohui Fan
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eye 6
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We report the discovery of a quasar pair at z=5 separated by 21 arcsec. Both objects were identified as quasar candidates using simple color selection techniques applied to photometric catalogs from the CFHT Legacy Survey (CFHTLS). Spectra obtained with the MMT present no discernible offset in redshift between the two objects; on the other hand, there are clear differences in the emission line profiles and in the multiwavelength spectral energy distributions that strongly disfavor the...
Topics: Astrophysics, Cosmology and Nongalactic Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1601.03056
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43
Sep 19, 2013
09/13
by
Weihsueh A. Chiu; Xiaohui Fan; Jeremiah P. Ostriker
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eye 43
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We present constraints on cosmological and star formation parameters based on combining observations of the Wilkinson Microwave Anisotropy Probe (WMAP) and high-redshift quasars from the Sloan Digital Sky Survey (SDSS). We use a semi-analytic model for reionization (Chiu and Ostriker 2000) that takes into account a number of important physical processes both within collapsing halos and in the intergalactic medium. Assuming that the efficiency of producing UV photons per baryon is constant, we...
Source: http://arxiv.org/abs/astro-ph/0304234v1
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4.0
Jun 29, 2018
06/18
by
Jan-Torge Schindler; Xiaohui Fan; Wolfgang J. Duschl
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eye 4
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At redshifts beyond $z{\sim}1$ measuring the black hole galaxy relations proves to be a difficult task. The bright light of the AGN aggravates deconvolution of black hole and galaxy properties. On the other hand high redshift data on these relations is vital to understand in what ways galaxies and black holes co-evolve and in what ways they don't. In this work we use black hole (BHMDs) and stellar mass densities (SMDs) to constrain the possible co-evolution of black holes with their host...
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1604.05333
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55
Sep 22, 2013
09/13
by
S. K. Leggett; T. R. Geballe; Xiaohui Fan
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eye 55
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We report the discovery of three cool brown dwarfs which fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands in the 1-2.5um range, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water. The newly discovered objects were detected as very red objects in the Sloan Digital Sky Survey imaging data and have JHK colors between the red L dwarfs and the blue Gl229B-like T dwarfs. They show both CO and...
Source: http://arxiv.org/abs/astro-ph/0004408v1
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7.0
Jun 30, 2018
06/18
by
Fuyan Bian; Xiaohui Fan; Ian McGreer; Zheng Cai; Linhua Jiang
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eye 7
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We present the HST WFC3/F275W UV imaging observations of A2218-Flanking, a lensed compact dwarf galaxy at redshift $z\approx2.5$. The stellar mass of A2218-Flanking is $\log(M/M_{\odot}=9.14$ and SFR is 12.5$M_\odot$yr$^{-1}$ after correcting the magnification. This galaxy has a young galaxy age of 127 Myr and a compact galaxy size of $r_{1/2}=2.4$kpc. The HST UV imaging observations cover the rest-frame Lyman continuum (LyC) emission ($\sim800${\AA}) from A2218-Flanking. We firmly detect...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1702.06540
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128
Sep 23, 2013
09/13
by
Rodger I. Thompson; Daniel Eisenstein; Xiaohui Fan; Marcia Rieke; Robert Kennicutt
texts
eye 128
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This paper addresses the nature of the near infrared background. We investigate whether there is an excess background at 1.4 microns, what is the source of the near infrared background and whether that background after the subtraction of all known sources contains the signature of high redshift objects (Z > 10). Based on NICMOS observations in the Hubble Ultra Deep Field and the Northern Hubble Deep Field we find that there is no excess in the background at 1.4 microns and that the claimed...
Source: http://arxiv.org/abs/0801.3825v1
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43
Sep 19, 2013
09/13
by
Richard L. White; Robert H. Becker; Xiaohui Fan; Michael A. Strauss
texts
eye 43
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We present high signal-to-noise ratio Keck ESI spectra of the two quasars known to have Gunn-Peterson absorption troughs, SDSS J1030+0524 (z=6.28) and SDSS J1148+5251 (z=6.37). The Ly alpha and Ly beta troughs for SDSS J1030+0524 are very black and show no evidence for any emission over a redshift interval of ~0.2 starting at z=6. On the other hand, SDSS J1148+5251 shows a number of emission peaks in the Ly beta Gunn-Peterson trough along with a single weak peak in the Ly alpha trough. The Ly...
Source: http://arxiv.org/abs/astro-ph/0303476v2
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55
Sep 23, 2013
09/13
by
Richard L. White; Robert H. Becker; Xiaohui Fan; Michael A. Strauss
texts
eye 55
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The Hubble Advanced Camera for Surveys has been used to obtain a narrow-band image of the weak emission peak seen at lambda=7205 A in the Gunn-Peterson Ly beta absorption trough of the highest redshift quasar, SDSS J1148+5251. The emission looks perfectly point-like; there is no evidence for the intervening galaxy that we previously suggested might be contaminating the quasar spectrum. We derive a more accurate astrometric position for the quasar in the two filters and see no indication of...
Source: http://arxiv.org/abs/astro-ph/0411195v1
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45
Sep 18, 2013
09/13
by
Jeremy Kepner; Xiaohui Fan; Neta Bahcall; James Gunn; Robert Lupton; Guohong Xu
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eye 45
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We describe an automated method for detecting clusters of galaxies in imaging and redshift galaxy surveys. The Adaptive Matched Filter (AMF) method utilizes galaxy positions, magnitudes, and---when available---photometric or spectroscopic redshifts to find clusters and determine their redshift and richness. The AMF can be applied to most types of galaxy surveys: from two-dimensional (2D) imaging surveys, to multi-band imaging surveys with photometric redshifts of any accuracy (2.5D), to...
Source: http://arxiv.org/abs/astro-ph/9803125v2
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42
Sep 21, 2013
09/13
by
Rodger I. Thompson; Daniel Eisenstein; Xiaohui Fan; Marcia Rieke; Robert C. Kennicutt
texts
eye 42
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This letter extends our previous fluctuation analysis of the near infrared background at 1.6 microns to the 1.1 micron (F110W) image of the Hubble Ultra Deep field. When all detectable sources are removed the ratio of fluctuation power in the two images is consistent with the ratio expected for faint, z 8. We also use numerically redshifted model galaxy spectral energy distributions for 50 and 10 million year old galaxies to predict the expected fluctuation power at 3.6 microns and 4.5 microns...
Source: http://arxiv.org/abs/0706.0547v1
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39
Sep 20, 2013
09/13
by
Rodger I. Thompson; Daniel Eisenstein; Xiaohui Fan; Marcia Rieke; Robert C. Kennicutt
texts
eye 39
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NICMOS observations of the resolved object fluxes in the Hubble Deep Field North and the Hubble Ultra Deep Field are significantly below the fluxes attributed to a 1.4 - 1.8 microns Near InfraRed Background Excess (NIRBE) from previous low spatial resolution NIRS measurements. Tests placing sources in the NICMOS image with fluxes sufficient to account for the NIRBE indicate that the NIRBE flux must be either flat on scales greater than 100 arc second or clumped on scales of several arc minutes...
Source: http://arxiv.org/abs/astro-ph/0612033v1
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9.0
Jun 30, 2018
06/18
by
Wenwen Zuo; Xue-Bing Wu; Xiaohui Fan; Richard Green; Ran Wang; Fuyan Bian
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eye 9
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We present new near-infrared (IR) observations of the H$\beta\ \lambda4861$ and MgII $\lambda2798$ lines for 32 luminous quasars with $3.2
Topics: Astrophysics of Galaxies, High Energy Astrophysical Phenomena, Astrophysics
Source: http://arxiv.org/abs/1412.2438
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9.0
Jun 29, 2018
06/18
by
Yanli Ai; Liming Dou; Xiaohui Fan; Feige Wang; Xue-Bing Wu; Fuyan Bian
texts
eye 9
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We report exploratory \chandra\ observation of the ultraluminous quasar SDSS J010013.02+280225.8 at redshift 6.30. The quasar is clearly detected by \chandra\ with a possible component of extended emission. The rest-frame 2-10 keV luminosity is 9.0$^{+9.1}_{-4.5}$ $\times$ 10$^{45}$ erg s$^{-1}$ with inferred photon index of $\Gamma$ = 3.03$^{+0.78}_{-0.70}$. This quasar is X-ray bright, with inferred X-ray-to-optical flux ratio \aox\ $=-1.22^{+0.07}_{-0.05}$, higher than the values found in...
Topics: Astrophysics, High Energy Astrophysical Phenomena, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1605.05078
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51
Sep 23, 2013
09/13
by
Brandon C. Kelly; Marianne Vestergaard; Xiaohui Fan; Philip Hopkins; Lars Hernquist; Aneta Siemiginowska
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eye 51
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We present an estimate of the black hole mass function (BHMF) of broad line quasars (BLQSOs) that self-consistently corrects for incompleteness and the statistical uncertainty in the mass estimates, based on a sample of 9886 quasars at 1 < z < 4.5 drawn from the Sloan Digital Sky Survey. We find evidence for `cosmic downsizing' of black holes in BLQSOs, where the peak in their number density shifts to higher redshift with increasing black hole mass. The cosmic mass density for black holes...
Source: http://arxiv.org/abs/1006.3561v1
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5.0
Jun 28, 2018
06/18
by
Linhua Jiang; Yue Shen; Ian D. McGreer; Xiaohui Fan; Eric Morganson; Rogier A. Windhorst
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eye 5
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We present a reverberation mapping (RM) experiment that combines broad- and intermediate-band photometry; it is the first such attempt targeting a sample of 13 quasars at $0.20.2$.
Topics: Astrophysics, Astrophysics of Galaxies
Source: http://arxiv.org/abs/1511.01520
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60
Sep 18, 2013
09/13
by
Rodger I. Thompson; Daniel Eisenstein; Xiaohui Fan; Mark Dickinson; Garth Illingworth; Robert C. Kennicutt
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eye 60
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We use the NICMOS Treasury and ACS HUDF images to measure the extinction corrected star formation history for 4681 galaxies in the region common to both images utilizing the star formation rate distribution function and other techniques similar to those employed with the NICMOS and WFPC2 images in the HDFN. Unlike the HDFN the NICMOS region of the HUDF appears to lack highly luminous and high star formation rate galaxies at redshifts beyond 3. The HUDF provides a region that is completely...
Source: http://arxiv.org/abs/astro-ph/0605060v1
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53
Sep 17, 2013
09/13
by
Max Pettini; Piero Madau; Michael Bolte; Jason X. Prochaska; Sara L. Ellison; Xiaohui Fan
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eye 53
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In order to search for metals in the Lyman alpha forest at redshifts z > 4, we have obtained spectra of high S/N and resolution of three QSOs at z > 5.4 discovered by the Sloan Digital Sky Survey. These data allow us to probe to metal enrichment of the intergalactic medium at early times with higher sensitivity than previous studies. We find 16 C IV absorption systems with column densities log N(C IV) = 12.50 - 13.98 over a total redshift path Delta X = 3.29. In the redshift interval z =...
Source: http://arxiv.org/abs/astro-ph/0305413v1
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45
Jul 20, 2013
07/13
by
Xue-Bing Wu; Ran Wang; Kasper B. Schmidt; Fuyan Bian; Linhua Jiang; Xiaohui Fan
texts
eye 45
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The identifications of quasars in the redshift range 2.2
Source: http://arxiv.org/abs/1107.0646v1
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10.0
Jun 30, 2018
06/18
by
Zheng Cai; Xiaohui Fan; Linhua Jiang; Romeel Dave; S. Peng Oh; Yujin Yang; Ann Zabludoff
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eye 10
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Numerous theoretical models have long proposed that a strong He II 1640 emission line is the most prominent and unique feature of massive Population III (Pop III) stars in high redshift galaxies. The He II 1640 line strength can constrain the mass and IMF of Pop III stars. We use F132N narrowband filter on the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3) to look for strong He II lambda 1640 emission in the galaxy BDF-521 at z=7.01, one of the most distant...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1412.3845
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45
Sep 23, 2013
09/13
by
Xiaobo Dong; Jianguo Wang; Tinggui Wang; Huiyuan Wang; Xiaohui Fan; Hongyan Zhou; Weimin Yuan; Qian Long
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eye 45
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We have conducted a systematic investigation of the origin and underlying physics of the line--line and line--continuum correlations of AGNs, particularly the Baldwin effect. Based on the homogeneous sample of Seyfert 1s and QSOs in the SDSS DR4, we find the origin of all the emission-line regularities is Eddington ratio (L/Ledd). The essential physics is that L/Ledd regulates the distributions of the properties (particularly column density) of the clouds bound in the line-emitting region.
Source: http://arxiv.org/abs/0903.0698v2
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60
Sep 23, 2013
09/13
by
Minsung Jang; Myungshin Im; Induk Lee; Yuji Urata; Lijin Huang; Hiroyuki Hirashita; Xiaohui Fan; Linhua Jiang
texts
eye 60
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At high redshift, the universe was so young that core-collapse supernovae (SNe) are suspected to be the dominant source of dust production. However, some observations indicate that the dust production by SNe is an inefficient process, casting doubts on the existence of abundant SNe-dust in the early universe. Recently, Perley et al. (2010) reported that the afterglow of GRB 071025 - an unusually red GRB at z ~ 5 - shows evidence for the SNe-produced dust. Since this is perhaps the only high...
Source: http://arxiv.org/abs/1110.3259v2
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15
Jun 27, 2018
06/18
by
Linhua Jiang; Ian D. McGreer; Xiaohui Fan; Fuyan Bian; Zheng Cai; Benjamin Clement; Ran Wang; Zhou Fan
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eye 15
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We present the discovery of eight quasars at z~6 identified in the Sloan Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have some overlap with each other, leading to repeat observations over an area spanning >4000 deg^2 (more than 1/4 of the total footprint). These overlap regions provide a unique dataset that allows us to select high-redshift quasars more than 0.5 mag fainter in the z band than those found with the SDSS single-epoch data. Our quasar candidates were...
Topics: Astrophysics of Galaxies, Astrophysics, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1504.01741
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47
Sep 23, 2013
09/13
by
Xiaobo Dong; Jianguo Wang; Luis C. Ho; Tinggui Wang; Xiaohui Fan; Huiyuan Wang; Hongyan Zhou; Weimin Yuan
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eye 47
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We used a large, homogeneous sample of 4178 z
Source: http://arxiv.org/abs/0903.5020v3
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61
Sep 19, 2013
09/13
by
Michael D. Gregg; Robert H. Becker; Richard L. White; Gordon T. Richards; Fred H. Chaffee; Xiaohui Fan
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eye 61
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In an ongoing infrared imaging survey of quasars at Keck Observatory, we have discovered that the z=1.285 quasar SDSS J233646.2-010732.6 comprises two point sources with a separation of 1.67". Resolved spectra show that one component is a standard quasar with a blue continuum and broad emission lines; the other is a broad absorption line (BAL) quasar, specifically, a BAL QSO with prominent absorption from MgII and metastable FeII, making it a member of the ``FeLoBAL'' class. The number of...
Source: http://arxiv.org/abs/astro-ph/0206163v1
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47
Sep 18, 2013
09/13
by
Linhua Jiang; Xiaohui Fan; Marianne Vestergaard; Jaron D. Kurk; Fabian Walter; Brandon C. Kelly; Michael A. Strauss
texts
eye 47
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We present Gemini near-infrared spectroscopic observations of six luminous quasars at z=5.8$\sim$6.3. Five of them were observed using Gemini-South/GNIRS, which provides a simultaneous wavelength coverage of 0.9--2.5 $\mu$m in cross dispersion mode. The other source was observed in K band with Gemini-North/NIRI. We calculate line strengths for all detected emission lines and use their ratios to estimate gas metallicity in the broad-line regions of the quasars. The metallicity is found to be...
Source: http://arxiv.org/abs/0707.1663v1
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50
Sep 21, 2013
09/13
by
Gisella De Rosa; Roberto Decarli; Fabian Walter; Xiaohui Fan; Linhua Jiang; Jaron Kurk; Anna Pasquali; Hans-Walter Rix
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eye 50
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[abridged] Quasars (QSOs) at the highest known redshift (z~6) are unique probes of the early growth of supermassive black holes (BHs). Until now, only the most luminous QSOs have been studied, often one object at a time. Here we present the most extensive consistent analysis to date of z>4 QSOs with observed NIR spectra, combining three new z~6 objects from our ongoing VLT-ISAAC program with nineteen 4=-0.37 (Lbol/LEdd~0.43) with a scatter of 0.20 dex for the z>4 sample and the =-0.80...
Source: http://arxiv.org/abs/1106.5501v1
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48
Sep 18, 2013
09/13
by
Gordon T. Richards; Xiaohui Fan; Donald P. Schneider; Daniel E. Vanden Berk; Michael A. Strauss; Donald G. York
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eye 48
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We present an empirical investigation of the colors of quasars in the Sloan Digital Sky Survey (SDSS) photometric system. The sample studied includes 2625 quasars with SDSS photometry. The quasars are distributed in a 2.5 degree wide stripe centered on the Celestial Equator covering $\sim529$ square degrees. Positions and SDSS magnitudes are given for the 898 quasars known prior to SDSS spectroscopic commissioning. New SDSS quasars represent an increase of over 200% in the number of known...
Source: http://arxiv.org/abs/astro-ph/0012449v1
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91
Sep 18, 2013
09/13
by
Linhua Jiang; Xiaohui Fan; Zeljko Ivezic; Gordon T. Richards; Donald P. Schneider; Michael A. Strauss; Brandon C. Kelly
texts
eye 91
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Using a sample of optically-selected quasars from the Sloan Digital Sky Survey, we have determined the radio-loud fraction (RLF) of quasars as a function of redshift and optical luminosity. The sample contains more than 30,000 objects and spans a redshift range of 010 to define radio-loud quasars, we find that b_0=-0.132+/-0.116, b_z=-2.052+/-0.261, and b_M=-0.183+/-0.025. The RLF at z=0.5 declines from 24.3% to 5.6% as luminosity decreases from M_{2500}=-26 to M_{2500}=-22, and the RLF at...
Source: http://arxiv.org/abs/astro-ph/0611453v1
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44
Sep 19, 2013
09/13
by
Xiao-Bo Dong; Luis C. Ho; Jian-Guo Wang; Ting-Gui Wang; Huiyuan Wang; Xiaohui Fan; Hongyan Zhou
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eye 44
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From detailed spectral analysis of a large sample of low-redshift active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey, we demonstrate---statistically for the first time---that narrow optical Fe II emission lines, both permitted and forbidden, are prevalent in type 1 AGNs. Remarkably, these optical lines are completely absent in type 2 AGNs, across a wide luminosity range, from Seyfert 2 galaxies to type 2 quasars. We suggest that the narrow FeII-emitting gas is confined to...
Source: http://arxiv.org/abs/1009.2209v1
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49
Sep 22, 2013
09/13
by
Gordon T. Richards; Michael A. Weinstein; Donald P. Schneider; Xiaohui Fan; Michael A. Strauss; Daniel E. Vanden Berk
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eye 49
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We demonstrate that the design of the Sloan Digital Sky Survey (SDSS) filter system and the quality of the SDSS imaging data are sufficient for determining accurate and precise photometric redshifts (``photo-z''s) of quasars. Using a sample of 2625 quasars, we show that photo-z determination is even possible for z 3. The accuracy of quasar photometric redshifts does not appear to be dependent upon magnitude to nearly 21st magnitude in i'. Careful calibration of the color-redshift relation to...
Source: http://arxiv.org/abs/astro-ph/0106038v1
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49
Sep 22, 2013
09/13
by
Xiaohui Fan; Vijay K. Narayanan; Michael A. Strauss; Richard L. White; Robert H. Becker; Laura Pentericci; Hans-Walter Rix
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We study the process of cosmic reionization and estimate the ionizing background in the IGM using the Lyman series absorption in the spectra of the four quasars at 5.710^{-3} at z~6. At this redshift, the mass-averaged neutral hydrogen fraction is larger than 1%; the mildly overdense regions (delta > 3) are still mostly neutral and the comoving mean free path of ionizing photons is shorter than 8 Mpc. Comparison with simulations of cosmological reionization shows that the observed properties...
Source: http://arxiv.org/abs/astro-ph/0111184v2
6
6.0
Jun 30, 2018
06/18
by
Ian D. McGreer; Xiaohui Fan; Michael A. Strauss; Zoltan Haiman; Gordon T. Richards; Linhua Jiang; Fuyan Bian; Donald P. Schneider
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eye 6
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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 Lyman 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_AB = 23.6) located 2arcsec (12 kpc projected) from the quasar with strong Lyman...
Topics: Astrophysics of Galaxies, Astrophysics, Cosmology and Nongalactic Astrophysics
Source: http://arxiv.org/abs/1404.2297
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43
Sep 19, 2013
09/13
by
A. O. Petric; C. L. Carilli; F. Bertoldi; Xiaohui Fan; P. Cox; Michael A. Strauss; A. Omont; Donald P. Schneider
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eye 43
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We present 1.4 and 5 GHz observations taken with the Very Large Array (VLA), and observations at 250 GHz obtained with the Max-Planck millimeter bolometer (MAMBO) at the IRAM 30~m telescope, of ten optically selected Quasi-stellar Objects (QSOs) at 5.0 < z < 6.28. Four sources are detected at 1.4 GHz two of which are radio loud and are also detected at 5 GHz. These results are roughly consistent with there being no evolution of the radio-loud QSO fraction out to z~6. Three sources have...
Source: http://arxiv.org/abs/astro-ph/0304097v1
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4.0
Jun 30, 2018
06/18
by
Ran Wang; Emmanuel Momjian; Chris L. Carilli; Xue-Bing Wu; Xiaohui Fan; Fabian Walter; Michael A. Strauss; Feige Wang; Linhua Jiang
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eye 4
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We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the {\it z=6.326} quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is, by far the most optically luminous, and radio-quiet quasar with the most massive black hole known at z>6. The VLBA observations have a synthesized beam size of 12.10 mas $\times$5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6+/-9.0...
Topics: Astrophysics of Galaxies, Astrophysics
Source: http://arxiv.org/abs/1701.03260
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51
Sep 23, 2013
09/13
by
Zheng Cai; Xiaohui Fan; Linhua Jiang; Fuyan Bian; Ian McGreer; Romeel Dave; Eiichi Egami; Ann Zabludoff; Yujin Yang; S. Peng Oh
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eye 51
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The He II \lambda 1640 emission line has been suggested as a direct probe of Population III (Pop III) stars at high-redshift, since it can arise from highly energetic ionizing photons associated with hot, metal free stars. We use the HST WFC3/F130N IR narrowband filter to probe He II \lambda 1640 emission in galaxy IOK-1 at z=6.96. The sensitivity of this measurement is >5x deeper than for previous measurements. From this deep narrowband imaging, combined with broadband observations in the...
Source: http://arxiv.org/abs/1105.2319v2
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50
Sep 24, 2013
09/13
by
Scott F. Anderson; Xiaohui Fan; Gordon T. Richards; Donald P. Schneider; Michael A. Strauss; Daniel E. Vanden Berk; James E. Gunn
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eye 50
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We present results on over 100 high-redshift quasars found in the Sloan Digital Sky Survey (SDSS), using automated selection algorithms applied to SDSS imaging data and with spectroscopic confirmation obtained during routine spectroscopic operations of the Sloan 2.5-m telescope. The SDSS spectra cover the wavelength range 3900--9200 Angstroms at a spectral resolution of 1800, and have been obtained for 116 quasars with redshifts greater than 3.94; 92 of these objects were previously...
Source: http://arxiv.org/abs/astro-ph/0103228v1
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56
Sep 18, 2013
09/13
by
Michael C. Liu; S. K. Leggett; David A. Golimowski; Kuenley Chiu; Xiaohui Fan; T. R. Geballe; Donald P. Schneider; J. Brinkmann
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eye 56
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We have resolved the newly discovered T dwarf SDSS J1534+1615 into a 0.11'' binary using the Keck sodium laser guide star adaptive optics system. With an integrated-light spectral type of T3.5, this binary provides a new benchmark for studying the distinctive J-band brightening previously noted among early and mid-T dwarfs, using two brown dwarfs with different spectral types but having a common metallicity and age and very similar surface gravities. We estimate spectral types of T1.5+/-0.5 and...
Source: http://arxiv.org/abs/astro-ph/0605037v1
