Iršič V, Slosar A, Bailey S, Eisenstein DJ, Font-Ribera A, Le Goff J-M, Lundgren B, McDonald P, O'Connell R, Palanque-Delabrouille N, et al. Detection of Lyβ auto-correlations and Lyα-Lyβ cross-correlations in BOSS Data Release 9. Journal of Cosmology and Astro-Particle Physics. 2013;09 :016. Publisher's VersionAbstract
The Lyman-β forest refers to a region in the spectra of distantquasars that lies between the rest-frame Lyman-β and Lyman-γemissions. The forest in this region is dominated by a combination ofabsorption due to resonant Lyα and Lyβ scattering. Whenconsidering the 1D Lyβ forest in addition to the 1D Lyαforest, the full statistical description of the data requires four 1Dpower spectra: Lyα and Lyβ auto-power spectra and theLyα-Lyβ real and imaginary cross-power spectra. We describehow these can be measured using an optimal quadratic estimator thatnaturally disentangles Lyα and Lyβ contributions. Using asample of approximately 60,000 quasar sight-lines from the BOSS DataRelease 9, we make the measurement of the one-dimensional power spectrumof fluctuations due to the Lyβ resonant scattering. While we havenot corrected our measurements for resolution damping of the power andother systematic effects carefully enough to use them for cosmologicalconstraints, we can robustly conclude the following: i) Lyβ powerspectrum and Lyα-Lyβ cross spectra are detected with highstatistical significance; ii) the cross-correlation coefficient is ≈1 on large scales; iii) the Lyβ measurements are contaminated bythe associated OVI absorption, which is analogous to the SiIIIcontamination of the Lyα forest. Measurements of the Lyβforest will allow extension of the usable path-length for the Lyαmeasurements while allowing a better understanding of the physics ofintergalactic medium and thus more robust cosmological constraints.
Majewski SR, Hasselquist S, Łokas EL, Nidever DL, Frinchaboy PM, García Pérez AE, Johnston KV, Mészáros S, Shetrone M, Allende Prieto C, et al. Discovery of a Dynamical Cold Point in the Heart of the Sagittarius dSph Galaxy with Observations from the APOGEE Project. The Astrophysical Journal Letters. 2013;777 :L13. Publisher's VersionAbstract
The dynamics of the core of the Sagittarius (Sgr) dwarf spheroidal(dSph) galaxy are explored using high-resolution (R ~ 22, 500), H-band,near-infrared spectra of over 1000 giant stars in the central 3deg2 of the system, of which 328 are identified as Sgrmembers. These data, among some of the earliest observations from theSloan Digital Sky Survey III/Apache Point Observatory Galactic EvolutionExperiment (APOGEE) and the largest published sample of high resolutionSgr dSph spectra to date, reveal a distinct gradient in the velocitydispersion of Sgr from 11 to 14 km s–1 for radii>0.°8 from center to a dynamical cold point of 8 kms–1 in the Sgr center—a trend differing from thatfound in previous kinematical analyses of Sgr over larger scales thatsuggests a more or less flat dispersion profile at these radii.Well-fitting mass models with either cored and cusped dark matterdistributions can be found to match the kinematical results, althoughthe cored profile succeeds with significantly more isotropic stellarorbits than required for a cusped profile. It is unlikely that the coldpoint reflects an unusual mass distribution. The dispersion gradient mayarise from variations in the mixture of populations with distinctkinematics within the dSph; this explanation is suggested (e.g., bydetection of a metallicity gradient across similar radii), but notconfirmed, by the present data. Despite these remaining uncertaintiesabout their interpretation, these early test data (including some frominstrument commissioning) demonstrate APOGEE's usefulness for precisiondynamical studies, even for fields observed at extreme airmasses.
Aird J, Coil AL, Moustakas J, Diamond-Stanic AM, Blanton MR, Cool RJ, Eisenstein DJ, Wong KC, Zhu G. PRIMUS: An Observationally Motivated Model to Connect the Evolution of the Active Galactic Nucleus and Galaxy Populations out to z ~ 1. The Astrophysical Journal. 2013;775 :41. Publisher's VersionAbstract
We present an observationally motivated model to connect the activegalactic nucleus (AGN) and galaxy populations at 0.2 < z < 1.0 andpredict the AGN X-ray luminosity function (XLF). We start withmeasurements of the stellar mass function of galaxies (from the PrismMulti-object Survey) and populate galaxies with AGNs using models forthe probability of a galaxy hosting an AGN as a function of specificaccretion rate. Our model is based on measurements indicating that thespecific accretion rate distribution is a universal function across awide range of host stellar masses with slope γ1 ≈-0.65 and an overall normalization that evolves with redshift. Wetest several simple assumptions to extend this model to high specificaccretion rates (beyond the measurements) and compare the predictionsfor the XLF with the observed data. We find good agreement with a modelthat allows for a break in the specific accretion rate distribution at apoint corresponding to the Eddington limit, a steep power-law tail tosuper-Eddington ratios with slope \gamma _2=-2.1^{+0.3}_{-0.5}, and ascatter of 0.38 dex in the scaling between black hole and host stellarmass. Our results show that samples of low luminosity AGNs are dominatedby moderately massive galaxies ( {M_*}\sim 10^{10}{--}10^{11} {M}_\odot)growing with a wide range of accretion rates due to the shape of thegalaxy stellar mass function rather than a preference for AGN activityat a particular stellar mass. Luminous AGNs may be a severely skewedpopulation with elevated black hole masses relative to their hostgalaxies and in rare phases of rapid accretion.
Tassev S, Zaldarriaga M, Eisenstein DJ. Solving large scale structure in ten easy steps with COLA. Journal of Cosmology and Astro-Particle Physics. 2013;06 :036. Publisher's VersionAbstract
We present the COmoving Lagrangian Acceleration (COLA) method: an N-bodymethod for solving for Large Scale Structure (LSS) in a frame that iscomoving with observers following trajectories calculated in LagrangianPerturbation Theory (LPT). Unlike standard N-body methods, the COLAmethod can straightforwardly trade accuracy at small-scales in order togain computational speed without sacrificing accuracy at large scales.This is especially useful for cheaply generating large ensembles ofaccurate mock halo catalogs required to study galaxy clustering and weaklensing, as those catalogs are essential for performing detailed erroranalysis for ongoing and future surveys of LSS. As an illustration, weran a COLA-based N-body code on a box of size 100 Mpc/h with particlesof mass ≈ 5 × 109Msolar/h. Running thecode with only 10 timesteps was sufficient to obtain an accuratedescription of halo statistics down to halo masses of at least1011Msolar/h. This is only at a modest speedpenalty when compared to mocks obtained with LPT. A standard detailedN-body run is orders of magnitude slower than our COLA-based code. Thespeed-up we obtain with COLA is due to the fact that we calculate thelarge-scale dynamics exactly using LPT, while letting the N-body codesolve for the small scales, without requiring it to capture exactly theinternal dynamics of halos. Achieving a similar level of accuracy inhalo statistics without the COLA method requires at least 3 times moretimesteps than when COLA is employed.
Dawson KS, Schlegel DJ, Ahn CP, Anderson SF, Aubourg É, Bailey S, Barkhouser RH, Bautista JE, Beifiori A, Berlind AA, et al. The Baryon Oscillation Spectroscopic Survey of SDSS-III. The Astronomical Journal. 2013;145 :10. Publisher's VersionAbstract
The Baryon Oscillation Spectroscopic Survey (BOSS) is designed tomeasure the scale of baryon acoustic oscillations (BAO) in theclustering of matter over a larger volume than the combined efforts ofall previous spectroscopic surveys of large-scale structure. BOSS uses1.5 million luminous galaxies as faint as i = 19.9 over 10,000deg2 to measure BAO to redshifts z < 0.7. Observations ofneutral hydrogen in the Lyα forest in more than 150,000 quasarspectra (g < 22) will constrain BAO over the redshift range 2.15
Parejko JK, Sunayama T, Padmanabhan N, Wake DA, Berlind AA, Bizyaev D, Blanton M, Bolton AS, van den Bosch F, Brinkmann J, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: the low-redshift sample. Monthly Notices of the Royal Astronomical Society. 2013;429 :98-112. Publisher's VersionAbstract
We report on the small-scale (0.5 < r < 40 h-1 Mpc)clustering of 78 895 massive (M* ˜ 1011.3M&sun;) galaxies at 0.2 < z < 0.4 from the first twoyears of data from the Baryon Oscillation Spectroscopic Survey (BOSS),to be released as part of Sloan Digital Sky Survey (SDSS) Data Release 9(DR9). We describe the sample selection, basic properties of thegalaxies and caveats for working with the data. We calculate the real-and redshift-space two-point correlation functions of these galaxies,fit these measurements using halo occupation distribution (HOD)modelling within dark matter cosmological simulations, and estimate theerrors using mock catalogues. These galaxies lie in massive haloes, witha mean halo mass of 5.2 × 1013 h-1M&sun;, a large-scale bias of ˜2.0 and a satellitefraction of 12 ± 2 per cent. Thus, these galaxies occupy haloeswith average masses in between those of the higher redshift BOSS CMASSsample and the original SDSS I/II luminous red galaxy sample.
Ross AJ, Percival WJ, Carnero A, Zhao G-bo, Manera M, Raccanelli A, Aubourg E, Bizyaev D, Brewington H, Brinkmann J, et al. The clustering of galaxies in the SDSS-III DR9 Baryon Oscillation Spectroscopic Survey: constraints on primordial non-Gaussianity. Monthly Notices of the Royal Astronomical Society. 2013;428 :1116-1127. Publisher's VersionAbstract
We analyse the density field of 264 283 galaxies observed by the SloanDigital Sky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey(BOSS) and included in the SDSS Data Release 9 (DR9). In total, the SDSSDR9 BOSS data include spectroscopic redshifts for over 400 000 galaxiesspread over a footprint of more than 3000 deg2. We measurethe power spectrum of these galaxies with redshifts 0.43 < z < 0.7in order to constrain the amount of local non-Gaussianity,f{_N_L^local}, in the primordial density field, paying particularattention to the impact of systematic uncertainties. The BOSS galaxydensity field is systematically affected by the local stellar densityand this influences the ability to accurately measure f{_N_L^local}. Inthe absence of any correction, we find (erroneously) that theprobability that f{_N_L^local} is greater than zero, P(f{_N_L^local}> 0), is 99.5 per cent. After quantifying and correcting for thesystematic bias and including the added uncertainty, we find - 45 0) = 91.0 per cent. A more conservative approach assumes that wehave only learnt the k dependence of the systematic bias and allows anyamplitude for the systematic correction; we find that the systematiceffect is not fully degenerate with that of f{_N_L^local}, and wedetermine that -82 < f{_N_L^local} < 178 (at 95 per centconfidence) and P(f{_N_L^local} > 0) = 68 per cent. This analysisdemonstrates the importance of accounting for the impact of Galacticforegrounds on f{_N_L^local} measurements. We outline the methods thataccount for these systematic biases and uncertainties. We expect ourmethods to yield robust constraints on f{_N_L^local} for both our ownand future large-scale structure investigations.
Aird J, Coil AL, Moustakas J, Diamond-Stanic AM, Blanton MR, Cool RJ, Eisenstein DJ, Wong KC, Zhu G. PRIMUS: An observationally motivated model to connect the evolution of the AGN and galaxy populations out to z~1. ArXiv e-prints. 2013;1301 :1689. Publisher's VersionAbstract
We present an observationally motivated model to connect the AGN andgalaxy populations at 0.2
Moustakas J, Coil A, Aird J, Blanton MR, Cool RJ, Eisenstein DJ, Mendez AJ, Wong KC, Zhu G, Arnouts S. PRIMUS: Constraints on Star Formation Quenching and Galaxy Merging, and the Evolution of the Stellar Mass Function From z=0-1. ArXiv e-prints. 2013;1301 :1688. Publisher's VersionAbstract
We measure the evolution of the stellar mass function (SMF) from z=0-1using multi-wavelength imaging and spectroscopic redshifts from thePRism MUlti-object Survey (PRIMUS) and the Sloan Digital Sky Survey(SDSS). From PRIMUS we construct an i<23 flux-limited sample of~40,000 galaxies at z=0.2-1.0 over five fields totaling ~5.5 deg^2, andfrom the SDSS we select ~170,000 galaxies at z=0.01-0.2 that we analyzeconsistently with respect to PRIMUS to minimize systematic errors in ourevolutionary measurements. We find that the SMF of all galaxies evolvesrelatively little since z=1, although we do find evidence for mass
Kleinman SJ, Kepler SO, Koester D, Pelisoli I, Peçanha V, Nitta A, Costa JES, Krzesinski J, Dufour P, Lachapelle F-R, et al. SDSS DR7 White Dwarf Catalog. The Astrophysical Journal Supplement Series. 2013;204 :5. Publisher's VersionAbstract
We present a new catalog of spectroscopically confirmed white dwarfstars from the Sloan Digital Sky Survey (SDSS) Data Release 7spectroscopic catalog. We find 20,407 white dwarf spectra, representing19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011DB white dwarf spectra from 12,843 and 923 stars, respectively. Thesenumbers represent more than a factor of two increase in the total numberof white dwarf stars from the previous SDSS white dwarf catalogs basedon DR4 data. Our distribution of subtypes varies from previous catalogsdue to our more conservative, manual classifications of each star in ourcatalog, supplementing our automatic fits. In particular, we find alarge number of magnetic white dwarf stars whose small Zeeman splittingsmimic increased Stark broadening that would otherwise result in anoverestimated log g if fit as a non-magnetic white dwarf. We calculatemean DA and DB masses for our clean, non-magnetic sample and find the DBmean mass is statistically larger than that for the DAs.
García Pérez AE, Cunha K, Shetrone M, Majewski SR, Johnson JA, Smith VV, Schiavon RP, Holtzman J, Nidever D, Zasowski G, et al. Very Metal-poor Stars in the Outer Galactic Bulge Found by the Apogee Survey. ArXiv e-prints. 2013;1301 :1367. Publisher's VersionAbstract
Despite its importance for understanding the nature of early stellargenerations and for constraining Galactic bulge formation models, atpresent little is known about the metal-poor stellar content of thecentral Milky Way. This is a consequence of the great distances involvedand intervening dust obscuration, which challenge optical studies.However, the Apache Point Observatory Galactic Evolution Experiment(APOGEE), a wide-area, multifiber, high-resolution spectroscopic surveywithin Sloan Digital Sky Survey III (SDSS-III), is exploring thechemistry of all Galactic stellar populations at infrared wavelengths,with particular emphasis on the disk and the bulge. An automatedspectral analysis of data on 2,403 giant stars in twelve fields in thebulge obtained during APOGEE commissioning yielded five stars with lowmetallicity([Fe/H]$\le-1.7$), including two that are very metal-poor[Fe/H]$\sim-2.1$ by bulge standards. Luminosity-based distance estimatesplace the five stars within the outer bulge, where other 1,246 of theanalyzed stars may reside. A manual reanalysis of the spectra verifiesthe low metallicities, and finds these stars to be enhanced in the$\alpha$-elements O, Mg, and Si without significant $\alpha$-patterndifferences with other local halo or metal-weak thick-disk stars ofsimilar metallicity, or even with other more metal-rich bulge stars.While neither the kinematics nor chemistry of these stars can yetdefinitively determine which, if any, are truly bulge members, ratherthan denizens of other populations co-located with the bulge, thenewly-identified stars reveal that the chemistry of metal-poor stars inthe central Galaxy resembles that of metal-weak thick-disk stars atsimilar metallicity.
Kochanek CS, Eisenstein DJ, Cool RJ, Caldwell N, Assef RJ, Jannuzi BT, Jones C, Murray SS, Forman WR, Dey A, et al. AGES: The AGN and Galaxy Evolution Survey. The Astrophysical Journal Supplement Series. 2012;200 :8. Publisher's VersionAbstract
The AGN and Galaxy Evolution Survey (AGES) is a redshift surveycovering, in its standard fields, 7.7 deg2 of the Boötesfield of the NOAO Deep Wide-Field Survey. The final sample consists of23,745 redshifts. There are well-defined galaxy samples in 10 bands (theBW , R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0 μm, and MIPS24 μm bands) to a limiting magnitude of I < 20 mag forspectroscopy. For these galaxies, we obtained 18,163 redshifts from asample of 35,200 galaxies, where random sparse sampling was used todefine statistically complete sub-samples in all 10 photometric bands.
Kochanek CS, Eisenstein DJ, Cool RJ, Caldwell N, Assef RJ, Jannuzi BT, Jones C, Murray SS, Forman WR, Dey A, et al. AGES: the AGN and Galaxy Evolution Survey (Kochanek+, 2012). VizieR Online Data Catalog. 2012;220 :00008. Publisher's VersionAbstract
The observations were made with Hectospec, a 300 fiber, 1 degree fieldof view, robotic spectrograph for the 6.5m MMT telescope at Mt. Hopkins,from 2004 April to 2007 July. The wavelength range is 3700-9200Åwith a pixel scale of 1.2Å and a spectral resolution of 6Å(i.e., roughly R~1000).(7 data files).
Ross AJ, Percival WJ, Sánchez AG, Samushia L, Ho S, Kazin E, Manera M, Reid B, White M, Tojeiro R, et al. The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: analysis of potential systematics. Monthly Notices of the Royal Astronomical Society. 2012;424 :564-590. Publisher's VersionAbstract
We analyse the density field of galaxies observed by the Sloan DigitalSky Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS)included in the SDSS Data Release Nine (DR9). DR9 includes spectroscopicredshifts for over 400 000 galaxies spread over a footprint of 3275deg2. We identify, characterize and mitigate the impact ofsources of systematic uncertainty on large-scale clusteringmeasurements, both for angular moments of the redshift-space correlationfunction, ξ(s), and the spherically averaged powerspectrum, P(k), in order to ensure that robust cosmological constraintswill be obtained from these data. A correlation between the projecteddensity of stars and the higher redshift (0.43 < z < 0.7) galaxysample (the approximately constant stellar mass threshold 'CMASS'sample) due to imaging systematics imparts a systematic error that islarger than the statistical error of the clustering measurements atscales s > 120 h-1 Mpc or k < 0.01 h Mpc-1.We find that these errors can be ameliorated by weighting galaxies basedon their surface brightness and the local stellar density. Theclustering of CMASS galaxies found in the Northern and Southern Galacticfootprints of the survey generally agrees to within 2σ. We usemock galaxy catalogues that simulate the CMASS selection function todetermine that randomly selecting galaxy redshifts in order to simulatethe radial selection function of a random sample imparts the leastsystematic error on ξ(s) measurements and that thissystematic error is negligible for the spherically averaged correlationfunction, ξ0. We find a peak in ξ0 ats˜ 200 h-1 Mpc, with a corresponding feature withperiod ˜0.03 h Mpc-1 in P(k), and find features atleast as strong in 4.8 per cent of the mock galaxy catalogues,concluding this feature is likely to be a consequence of cosmicvariance. The methods we recommend for the calculation of clusteringmeasurements using the CMASS sample are adopted in companion papers thatlocate the position of the baryon acoustic oscillation feature,constrain cosmological models using the full shape of ξ0and measure the rate of structure growth.
Hand N, Addison GE, Aubourg E, Battaglia N, Battistelli ES, Bizyaev D, Bond RJ, Brewington H, Brinkmann J, Brown BR, et al. Evidence of Galaxy Cluster Motions with the Kinematic Sunyaev-Zel'dovich Effect. Physical Review Letters. 2012;109 :41101. Publisher's VersionAbstract
Using high-resolution microwave sky maps made by the Atacama CosmologyTelescope, we for the first time present strong evidence for motions ofgalaxy clusters and groups via microwave background temperaturedistortions due to the kinematic Sunyaev-Zel’dovich effect. Galaxyclusters are identified by their constituent luminous galaxies observedby the Baryon Oscillation Spectroscopic Survey, part of the SloanDigital Sky Survey III. We measure the mean pairwise momentum ofclusters, with a probability of the signal being due to random errors of0.002, and the signal is consistent with the growth of cosmic structurein the standard model of cosmology.
Cool RJ, Eisenstein DJ, Kochanek CS, Brown MJI, Caldwell N, Dey A, Forman WR, Hickox RC, Jannuzi BT, Jones C, et al. The Galaxy Optical Luminosity Function from the AGN and Galaxy Evolution Survey. The Astrophysical Journal. 2012;748 :10. Publisher's VersionAbstract
We present the galaxy optical luminosity function for the redshift range0.05 < z < 0.75 from the AGN and Galaxy Evolution Survey, aspectroscopic survey of 7.6 deg2 in the Boötes field ofthe NOAO Deep Wide-Field Survey. Our statistical sample is composed of12,473 galaxies with known redshifts down to I = 20.4 (AB). Our resultsat low redshift are consistent with those from Sloan Digital Sky Survey;at higher redshift, we find strong evidence for evolution in theluminosity function, including differential evolution between blue andred galaxies. We find that the luminosity density evolves as (1 +z)(0.54 ± 0.64) for red galaxies and (1 + z)(1.64± 0.39) for blue galaxies.
Xu X, Cuesta AJ, Padmanabhan N, Eisenstein DJ, McBride CK. Measuring D_A and H at z=0.35 from the SDSS DR7 LRGs using baryon acoustic oscillations. ArXiv e-prints. 2012;1206 :6732. Publisher's VersionAbstract
We present measurements of the angular diameter distance D_A(z) and theHubble parameter H(z) at z=0.35 using the anisotropy of the baryonacoustic oscillation (BAO) signal measured in the galaxy clusteringdistribution of the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7)Luminous Red Galaxies (LRG) sample. Our work is the first to applydensity-field reconstruction to an anisotropic analysis of the acousticpeak. Reconstruction partially removes the effects of non-linearevolution and redshift-space distortions in order to sharpen theacoustic signal. We present the theoretical framework behind theanisotropic BAO signal and give a detailed account of the fitting modelwe use to extract this signal from the data. Our method focuses only onthe acoustic peak anisotropy, rather than the more model-dependentanisotropic information from the broadband power. We test the robustnessof our analysis methods on 160 LasDamas DR7 mock catalogues and find
Weinberg DH, Mortonson MJ, Eisenstein DJ, Hirata C, Riess AG, Rozo E. Observational Probes of Cosmic Acceleration. ArXiv e-prints. 2012;1201 :2434. Publisher's VersionAbstract
The accelerating expansion of the universe is the most surprisingcosmological discovery in many decades, implying that the universe isdominated by some form of "dark energy" with exotic physical properties,or that Einstein's theory of gravity breaks down on cosmological scales.The profound implications of cosmic acceleration have inspired ambitiousexperimental efforts to measure the history of expansion and growth ofstructure with percent-level precision or higher. We review in detailthe four most well established methods for making such measurements:Type Ia supernovae, baryon acoustic oscillations (BAO), weakgravitational lensing, and galaxy clusters. We pay particular attentionto the systematic uncertainties in these techniques and to strategiesfor controlling them at the level needed to exploit "Stage IV" darkenergy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We brieflyreview a number of other approaches including redshift-spacedistortions, the Alcock-Paczynski test, and direct measurements of H_0.We present extensive forecasts for constraints on the dark energyequation of state and parameterized deviations from GR, achievable withStage III and Stage IV experimental programs that incorporatesupernovae, BAO, weak lensing, and CMB data. We also show the level ofprecision required for other methods to provide constraints competitivewith those of these fiducial programs. We emphasize the value of abalanced program that employs several of the most powerful methods incombination, both to cross-check systematic uncertainties and to takeadvantage of complementary information. Surveys to probe cosmicacceleration produce data sets with broad applications, and theycontinue the longstanding astronomical tradition of mapping the universein ever greater detail over ever larger scales.
Aird J, Coil AL, Moustakas J, Blanton MR, Burles SM, Cool RJ, Eisenstein DJ, Smith SMM, Wong KC, Zhu G. PRIMUS: The Dependence of AGN Accretion on Host Stellar Mass and Color. The Astrophysical Journal. 2012;746 :90. Publisher's VersionAbstract
We present evidence that the incidence of active galactic nuclei (AGNs)and the distribution of their accretion rates do not depend on thestellar masses of their host galaxies, contrary to previous studies. Weuse hard (2-10 keV) X-ray data from three extragalactic fields (XMM-LSS,COSMOS, and ELAIS-S1) with redshifts from the Prism Multi-object Surveyto identify 242 AGNs with L 2-10 keV = 1042-44 ergs-1 within a parent sample of ~25,000 galaxies at 0.2 < z< 1.0 over ~3.4 deg2 and to i ~ 23. We find that althoughthe fraction of galaxies hosting an AGN at fixed X-ray luminosity risesstrongly with stellar mass, the distribution of X-ray luminosities isindependent of mass. Furthermore, we show that the probability that agalaxy will host an AGN can be defined by a universal Eddington ratiodistribution that is independent of the host galaxy stellar mass and hasa power-law shape with slope -0.65. These results demonstrate that AGNsare prevalent at all stellar masses in the range 9.5 and that the samephysical processes regulate AGN activity in all galaxies in this stellarmass range. While a higher AGN fraction may be observed in massivegalaxies, this is a selection effect related to the underlying Eddingtonratio distribution. We also find that the AGN fraction drops rapidlybetween z ~ 1 and the present day and is moderately enhanced (factor ~2)in galaxies with blue or green optical colors. Consequently, while AGNactivity and star formation appear to be globally correlated, we do notfind evidence that the presence of an AGN is related to the quenching ofstar formation or the color transformation of galaxies.
Ross NP, Myers AD, Sheldon ES, Yeche C, Strauss MA, Bovy J, Kirkpatrick JA, Richards GT, Aubourg E, Blanton MR, et al. The quasars MMT-BOSS pilot survey (Ross+, 2012). VizieR Online Data Catalog. 2012;219 :90003. Publisher's VersionAbstract
The Sloan Digital Sky Survey is now in its third phase (SDSS-III;Eisenstein et al. 2011AJ....142...72E) and is carrying out a combinationof four interleaved surveys that will continue until the summer of 2014.One of those surveys, the Baryon Oscillation Spectroscopic Survey(BOSS), commenced operations in late 2009 and is using essentially allthe dark time for SDSS-III. BOSS uses the same 2.5m Sloan Foundationtelescope that was used in SDSS-I/II, but since BOSS will observefainter targets, the fiber-fed spectrographs have been significantlyupgraded. These upgrades include: new CCDs with improved blue and redresponse; 1000 2" instead of 640 3" optical diameter fibers; higherthroughput gratings over a spectral range of 3600-10000Å at aresolution of about 2000, and improved optics.Prior to the commencement of BOSS spectroscopy, we carried outspectroscopy of quasar candidates selected from co-added photometry inSDSS Stripe 82. Observations of these candidates were carried out inqueue mode between 2008 September and 2009 January using the Hectospecmulti-fiber spectrograph on the 6.5m Multiple Mirror Telescope (MMT). InTables 14 and 15, we provide positions, PSF photometry (as observed,uncorrected for Galactic extinction), and redshifts for confirmedquasars from the MMT survey. Objects that are not flagged Primary in theCAS are listed separately (table 15).(2 data files).