We perform halo occupation distribution (HOD) modeling to interpretsmall-scale and intermediate-scale clustering of 35,000 luminousearly-type galaxies and their cross-correlation with a reference imagingsample of normal L * galaxies in the Sloan Digital SkySurvey. The modeling results show that most of these luminous redgalaxies (LRGs) are central galaxies residing in massive halos oftypical mass M~ a few times 1013-1014 h-1 M sun, while a few percent of them have to besatellites within halos in order to produce the strong auto-correlationsexhibited on smaller scales. The mean luminosity Lc ofcentral LRGs increases with the host halo mass, with a rough scalingrelation of Lc vprop M 0.5. The halo mass requiredto host on average one satellite LRG above a luminosity threshold isfound to be about 10 times higher than that required to host a centralLRG above the same threshold. We find that in massive halos thedistribution of L * galaxies roughly follows that of the darkmatter and their mean occupation number scales with halo mass as M1.5. The HOD modeling results also allow for an intuitiveunderstanding of the scale-dependent luminosity dependence of thecross-correlation between LRGs and L * galaxies. Constraintson the LRG HOD provide tests for models of formation and evolution ofmassive galaxies, and they are also useful for cosmological parameterinvestigations. In one of the appendices, we provide LRG HOD parameterswith dependence on cosmology inferred from modeling the two-pointauto-correlation functions of LRGs.
We explore the connection between different classes of active galacticnuclei (AGNs) and the evolution of their host galaxies, by deriving hostgalaxy properties, clustering, and Eddington ratios of AGNs selected inthe radio, X-ray, and infrared (IR) wavebands. We study a sample of 585AGNs at 0.25 < z < 0.8 using redshifts from the AGN and GalaxyEvolution Survey (AGES). We select AGNs with observations in the radioat 1.4 GHz from the Westerbork Synthesis Radio Telescope, X-rays fromthe Chandra XBoötes Survey, and mid-IR from the Spitzer IRACShallow Survey. The radio, X-ray, and IR AGN samples show only modestoverlap, indicating that to the flux limits of the survey, theyrepresent largely distinct classes of AGNs. We derive host galaxy colorsand luminosities, as well as Eddington ratios, for obscured or opticallyfaint AGNs. We also measure the two-point cross-correlation between AGNsand galaxies on scales of 0.3-10 h -1 Mpc, and derive typicaldark matter halo masses. We find that: (1) radio AGNs are mainly foundin luminous red sequence galaxies, are strongly clustered (with Mhalo ~ 3 × 1013 h -1 Msun), and have very low Eddington ratios λ lsim10-3 (2) X-ray-selected AGNs are preferentially found ingalaxies that lie in the "green valley" of color-magnitude space and areclustered similar to the typical AGES galaxies (M halo ~1013 h -1 M sun), with 10-3lsim λ lsim 1; (3) IR AGNs reside in slightly bluer, slightlyless luminous galaxies than X-ray AGNs, are weakly clustered (Mhalo lsim 1012 h -1 M sun),and have λ>10-2. We interpret these results interms of a simple model of AGN and galaxy evolution, whereby a "quasar"phase and the growth of the stellar bulge occurs when a galaxy's darkmatter halo reaches a critical mass between ~1012 and1013 M sun. After this event, star formationceases and AGN accretion shifts from radiatively efficient (optical- andIR-bright) to radiatively inefficient (optically faint, radio-bright)modes.
We present galaxy luminosity functions at 3.6, 4.5, 5.8, and 8.0 μmmeasured by combining photometry from the IRAC Shallow Survey withredshifts from the AGN and Galaxy Evolution Survey (AGES) of the NOAODeep Wide-Field Survey Boötes field. The well defined IRAC samplescontain 3800-5800 galaxies for the 3.6-8.0 μm bands withspectroscopic redshifts and z < 0.6. We obtained relatively completeluminosity functions in the local redshift bin of z < 0.2 for allfour IRAC channels that are well fitted by Schechter functions. Afteranalyzing the samples for the whole redshift range, we found significantevolution in the luminosity functions for all four IRAC channels thatcan be fitted as an evolution in M * with redshift, ΔM* = Qz. While we measured Q = 1.2 ± 0.4 and 1.1± 0.4 in the 3.6 and 4.5 μm bands consistent with thepredictions from a passively evolving population, we obtained Q = 1.8± 1.1 in the 8.0 μm band consistent with other evolving starformation rate estimates. We compared our luminosity functions with thepredictions of semianalytical galaxy formation and found the bestagreement at 3.6 and 4.5 μm, rough agreement at 8.0 μm, and alarge mismatch at 5.8 μm. These models also predicted a comparableQ-value to our luminosity functions at 8.0 μm, but predicted smallervalues at 3.6 and 4.5 μm. We also measured the luminosity functionsseparately for early- and late-type galaxies. While the luminosityfunctions of late-type galaxies resemble those for the total population,the luminosity functions of early-type galaxies in the 3.6 and 4.5 μmbands indicate deviations from the passive evolution model, especiallyfrom the measured flat luminosity density evolution. Combining ourestimates with other measurements in the literature, we found 53
In an effort to resolve the discrepancy between two measurements of thefundamental constant μ, the proton to electron mass ratio, at earlytimes in the universe we reanalyze the same data used in the earlierstudies. Our analysis of the molecular hydrogen absorption lines inarchival Very Large Telescope/Ultraviolet and Visible EchelleSpectrometer (UVES) spectra of the damped Lyman alpha systems in thequasi-stellar objects Q0347-383 and Q0405-443 yields a combinedmeasurement of a Δμ/μ value of (-7 ± 8) ×10-6, consistent with no change in the value of μ over atime span of 11.5 Gyr. Here, we define Δμ as (μ z - μ0) where μ z is the value of μat a redshift of z and μ0 is the present-day value. Ournull result is consistent with the recent measurements of King et al.,Δμ/μ = (2.6 ± 3.0) × 10-6, andinconsistent with the positive detection of a change in μ by Reinholdet al. Both of the previous studies and this study are based on the samedata but with differing analysis methods. Improvements in the wavelengthcalibration over the UVES pipeline calibration is a key element in bothof the null results. This leads to the conclusion that the fundamentalconstant μ is unchanged to an accuracy of 10-5 over the
This paper describes the Seventh Data Release of the Sloan Digital SkySurvey (SDSS), marking the completion of the original goals of the SDSSand the end of the phase known as SDSS-II. It includes 11,663deg2 of imaging data, with most of the ~2000 deg2increment over the previous data release lying in regions of lowGalactic latitude. The catalog contains five-band photometry for 357million distinct objects. The survey also includes repeat photometry ona 120° long, 2fdg5 wide stripe along the celestial equator in theSouthern Galactic Cap, with some regions covered by as many as 90individual imaging runs. We include a co-addition of the best of thesedata, going roughly 2 mag fainter than the main survey over 250deg2. The survey has completed spectroscopy over 9380deg2 the spectroscopy is now complete over a large contiguousarea of the Northern Galactic Cap, closing the gap that was present inprevious data releases. There are over 1.6 million spectra in total,including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The datarelease includes improved stellar photometry at low Galactic latitude.The astrometry has all been recalibrated with the second version of theUSNO CCD Astrograph Catalog, reducing the rms statistical errors at thebright end to 45 milliarcseconds per coordinate. We further quantify asystematic error in bright galaxy photometry due to poor skydetermination; this problem is less severe than previously reported forthe majority of galaxies. Finally, we describe a series of improvementsto the spectroscopic reductions, including better flat fielding andimproved wavelength calibration at the blue end, better processing ofobjects with extremely strong narrow emission lines, and an improveddetermination of stellar metallicities.
The Spitzer Deep, Wide-Field Survey (SDWFS) is a four-epoch infraredsurvey of 10 deg2 in the Boötes field of the NOAO DeepWide-Field Survey using the IRAC instrument on the Spitzer SpaceTelescope. SDWFS, a Spitzer Cycle 4 Legacy project, occupies a uniqueposition in the area-depth survey space defined by other Spitzersurveys. The four epochs that make up SDWFS permit—for the firsttime—the selection of infrared-variable and high proper motionobjects over a wide field on timescales of years. Because of its largesurvey volume, SDWFS is sensitive to galaxies out to z ~ 3 withrelatively little impact from cosmic variance for all but the richestsystems. The SDWFS data sets will thus be especially useful forcharacterizing galaxy evolution beyond z ~ 1.5. This paper explains theSDWFS observing strategy and data processing, presents the SDWFS mosaicsand source catalogs, and discusses some early scientific findings. Thepublicly released, full-depth catalogs contain 6.78, 5.23, 1.20, and0.96 × 105 distinct sources detected to the average5σ, 4''-diameter, aperture-corrected limits of 19.77, 18.83,16.50, and 15.82 Vega mag at 3.6, 4.5, 5.8, and 8.0 μm, respectively.The SDWFS number counts and color-color distribution are consistent withother, earlier Spitzer surveys. At the 6 minute integration time of the
We combine IR, optical, and X-ray data from the overlapping, 9.3deg2 NOAO Deep Wide-Field Survey, AGN and Galaxy EvolutionSurvey (AGES), and XBoötes Survey to measure the X-ray evolution of6146 normal galaxies as a function of absolute optical luminosity,redshift, and spectral type over the largely unexplored redshift range0.1 lsim z lsim 0.5. Because only the closest or brightest of thegalaxies are individually detected in X-rays, we use a stacking analysisto determine the mean properties of the sample. Our results suggest thatX-ray emission from spectroscopically late-type galaxies is dominated bystar formation, while that from early-type galaxies is dominated by acombination of hot gas and active galactic nucleus (AGN) emission. Wefind that the mean star formation and supermassive black hole accretionrate densities evolve like ~(1 + z)3±1, in agreementwith the trends found for samples of bright, individually detectablestarburst galaxies and AGN. Our work also corroborates the results ofmany previous stacking analyses of faint source populations, withimproved statistics.
We have studied the feasibility and scientific potential of zenithobserving liquid-mirror telescopes having 20-100 m diameters located onthe Moon. They would carry out deep infrared surveys to study thedistant universe and follow up discoveries made with the 6 m James WebbSpace Telescope (JWST), with more detailed images and spectroscopicstudies. They could detect objects 100 times fainter than JWST,observing the first high-redshift stars in the early universe and theirassembly into galaxies. We explored the scientific opportunities, keytechnologies, and optimum location of such telescopes. We havedemonstrated critical technologies. For example, the primary mirrorwould necessitate a high-reflectivity liquid that does not evaporate inthe lunar vacuum and remains liquid at less than 100 K. We have made acrucial demonstration by successfully coating an ionic liquid that hasnegligible vapor pressure. We also successfully experimented with aliquid mirror spinning on a superconducting bearing, as will be neededfor the cryogenic, vacuum environment of the telescope. We haveinvestigated issues related to lunar locations, concluding thatlocations within a few kilometers of a pole are ideal for deep sky coverand long integration times. We have located ridges and crater rimswithin 0.5° of the north pole that are illuminated for at least somesun angles during lunar winter, providing power and temperature control.We also have identified potential problems, like lunar dust. Issuesraised by our preliminary study demand additional in-depth analyses.These issues must be fully examined as part of a scientific debate thatwe hope to start with the present article.
We study the large-scale anisotropic two-point correlation functionusing 46,760 luminous red galaxies at redshifts 0.16-0.47 from the SloanDigital Sky Survey. We measure the correlation function as a function ofseparations parallel and perpendicular to the line of sight in order totake account of anisotropy of the large-scale structure in redshiftspace. We find a slight signal of baryonic features in the anisotropiccorrelation function, i.e., a ``baryon ridge'' corresponding to a baryonacoustic peak in the spherically averaged correlation function, whichhas already been reported using the same sample. The baryon ridge hasprimarily a spherical structure with a known radius in comovingcoordinates. It enables us to divide the redshift distortion effectsinto dynamical and geometrical components and provides furtherconstraints on cosmological parameters, including the dark energyequation-of-state. With an assumption of a flat Λ cosmology, wefind the best-fit values ofΩm=0.218+0.047-0.037 and
We built an optimal basis of low-resolution templates for galaxies overthe wavelength range from 0.2 to 10 μm using a variant of thealgorithm presented by Budavari and coworkers. We derived them using 11bands of photometry from the NDWFS, FLAMEX, zBoötes, and IRACShallow surveys for 16,033 galaxies in the NDWFS Boötes field withspectroscopic redshifts measured by the AGN and Galaxy Evolution Survey.We also developed algorithms to accurately determine photometricredshifts, K-corrections, and bolometric luminosities using thesetemplates. Our photometric redshifts have an accuracy of
We measure the evolution of the luminous red galaxy (LRG) luminosityfunction in the redshift range 0.12, minimizing the impact oflarge-scale structure on our results. We find that the LRG populationhas evolved little beyond the passive fading of its stellar populationssince z~0.9. Based on our luminosity function measurements and assuminga nonevolving Salpeter stellar initial mass function, we find that themost massive (L>3L*) red galaxies have grown by less than
Many theoretical models of dark energy invoke rolling scaler fieldswhich in turn predict time varying values of the fundamental constants.Establishing the value of the fundamental constants at various times inthe universe can probe and test the various dark energy theories. One ofthe constants that is predicted to vary is the ratio of the electron toproton mass μ. It was established early on that molecular spectra aresensitive to the value of μ and can be used as probes of that value.This article describes the use of the spectrum of molecular hydrogen inhigh redshift Damped Lyman Alpha systems (DLAs) as a sensitive probe ofthe time evolution of μ.
We present high signal-to-noise ratio measurements of the acoustic scalein the presence of nonlinear growth and redshift distortions using 320h-3 Gpc3 of cosmological particle-meshsimulations. Using simple fitting methods, we obtain robust measurementsof the acoustic scale with scatter close to that predicted by the Fishermatrix. We detect and quantify the shift in the acoustic scale byanalyzing the power spectrum: we detect at greater than 5 σ adecrease in the acoustic scale in the real-space matter power spectrum
I review the observational evidence for dark energy, arguing that thelarge-scale structure observed at low redshift and in the cosmicmicrowave background offers a strong corroboration of the supernova Iaresults. The angular scale of the acoustic oscillations in the cosmicmicrowave background strongly support a nearly flat universe, while manyarguments from low-redshift cosmology support a matter density around
We present a numerical study of the evolution of galaxy clustering whengalaxies flow passively from high redshift, respecting the continuityequation throughout. While passive flow is a special case of galaxyevolution, it allows a well-defined study of galaxy ancestry and servesas an interesting limit to be compared to nonpassive cases. We usedissipationless N-body simulations, assign galaxies to massive halos atz=1 and 2 using various halo occupation distribution (HOD) models, andtrace these galaxy particles to lower redshift while conserving theirnumber. We find that passive flow results in an asymptotic convergenceat low redshift in the HOD and in galaxy clustering on scales above ~3h-1 Mpc for a wide range of initial HODs. As galaxies becomeless biased with respect to mass asymptotically with time, the HODparameters evolve such that M1/Mmin decreaseswhile α converges toward unity, whereg(M)>=exp(-Mmin/M)[1+(M/M1)α].The satellite populations converge toward the Poisson distribution atlow redshift. The convergence is robust for different number densitiesand is enhanced when galaxies evolve from higher redshift. We compareour results with the observed luminous red galaxy (LRG) sample from SDSSthat has the same number density. We claim that if LRGs have experienceda strict passive flow, their g(M)> should be close toa power law with an index of unity in halo mass. Discrepancies could bedue to dry galaxy merging or new members arising between the initial andthe final redshifts. The spatial distribution of passively flowinggalaxies within halos appears on average more concentrated than the halomass profile at low redshift. The evolution of bias for passivelyflowing galaxies is consistent with linear bias evolution onquasi-linear as well as large scales.
This paper describes the Sixth Data Release of the Sloan Digital SkySurvey. With this data release, the imaging of the northern Galactic capis now complete. The survey contains images and parameters of roughly287 million objects over 9583 deg2, including scans over alarge range of Galactic latitudes and longitudes. The survey alsoincludes 1.27 million spectra of stars, galaxies, quasars, and blank sky(for sky subtraction) selected over 7425 deg2 . This releaseincludes much more stellar spectroscopy than was available in previousdata releases and also includes detailed estimates of stellartemperatures, gravities, and metallicities. The results of improvedphotometric calibration are now available, with uncertainties of roughly
We report the first results of our systematic search for strongly lensedquasars using the spectroscopically confirmed quasars in the SloanDigital Sky Survey (SDSS). Among 46,420 quasars from the SDSS DataRelease 3 (~4188 deg2), we select a subsample of 22,683quasars that are located at redshifts between 0.6 and 2.2 and arebrighter than the Galactic extinction-corrected i-band magnitude of19.1. We identify 220 lens candidates from the quasar subsample, forwhich we conduct extensive and systematic follow-up observations inoptical and near-infrared wavebands, in order to construct a completelensed quasar sample at image separations between 1'' and 20'' and fluxratios of faint to bright lensed images larger than 10-0.5.We construct a statistical sample of 11 lensed quasars. Ten of these aregalaxy-scale lenses with small image separations (~ 1''-2'') and one isa large separation (15'') system which is produced by a massive clusterof galaxies, representing the first statistical sample of lensed quasarsincluding both galaxy- and cluster-scale lenses. The Data Release 3spectroscopic quasars contain an additional 11 lensed quasars outsidethe statistical sample.
We present cosmological results from the statistics of lensed quasars inthe Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking properaccount of the selection function, we compute the expected number ofquasars lensed by early-type galaxies and their image separationdistribution assuming a flat universe, which is then compared with sevenlenses found in the SDSS Data Release 3 to derive constraints on darkenergy under strictly controlled criteria. For a cosmological constantmodel (w = -1) we obtain ΩΛ =0.74+0.11 -0.15(stat.)+0.13-0.06(syst.). Allowing w to be a free parameter we findΩM = 0.26+0.07-0.06(stat.)+0.03 -0.05(syst.) and w =-1.1 ± 0.6(stat.)+0.3 -0.5(syst.) whencombined with the constraint from the measurement of baryon acousticoscillations in the SDSS luminous red galaxy sample. Our results are ingood agreement with earlier lensing constraints obtained using radiolenses, and provide additional confirmation of the presence of darkenergy consistent with a cosmological constant, derived independently oftype Ia supernovae.
We study the nature of faint red-selected galaxies at z~2-3 using theHubble Ultra Deep Field (HUDF) and Spitzer Infrared Array Camera (IRAC)photometry. Given the magnitude limit of the HST data, we detectcandidate galaxies to HAB<26 mag, probing lower luminosity(lower mass) galaxies at these redshifts. We identify 32 galaxiessatisfying the (J110-H160)AB>1.0 magcolor selection, 16 of which have unblended [3.6 μm] and [4.5 μm]photometry from Spitzer. Using this multiwavelength data set, we derivephotometric redshifts, masses, and stellar population parameters forthese objects. We find that the selected objects span a diverse range ofproperties over a large range of redshifts, 1<~z<~3.5. Asubstantial fraction (11/32) of the(J110-H160)AB>1.0 mag populationappear to be lower redshift (z<~2.5), heavily obscured dusty galaxiesor edge-on spiral galaxies, while others (12/32) appear to be galaxiesat 2<~z<~3.5 whose light at rest-frame optical wavelengths isdominated by evolved stellar populations. We argue that longerwavelength data (>~1 μm, rest frame) are essential forinterpreting the properties of the stellar populations in red-selectedgalaxies at these redshifts. Interestingly, by including Spitzer data,many candidates for galaxies dominated by evolved stellar populationsare rejected, and for only a subset of the sample (6/16) do the datafavor this interpretation. These objects have a surface density of ~1arcmin-2. We place an upper limit on the space density ofcandidate massive evolved galaxies with 2.5AB160<=26 mag ofn=6.6+2.0-3.0×10-4Mpc-3, with a corresponding upper limit on the stellar massdensity ofρ*=5.6+4.4-2.8×107Msolar Mpc-3. The z>2.5 objects that aredominated by evolved stellar populations have a space density at mostone-third that of z~0 red early-type galaxies. Therefore, at leasttwo-thirds of present-day early-type galaxies assemble or evolve intotheir current configuration at redshifts below 2.5. We find a dearth ofcandidates for low-mass (<~2×1010 Msolar)galaxies at 1.5
We present a clustering analysis of luminous red galaxies (LRGs) usingnearly 9000 objects from the final, three-year catalogue of the 2dF-SDSSLRG and QSO (2SLAQ) Survey. We measure the redshift-space two-pointcorrelation function, ξ(s) and find that, at the mean LRG redshift ofshows the characteristic downturn at small scales(<~1h-1Mpc) expected from line-of-sight velocitydispersion. We fit a double power law to ξ(s) and measure anamplitude and slope of s0 =17.3+2.5-2.0h-1Mpc,γ = 1.03 +/-0.07 at small scales (s < 4.5h-1Mpc) and s0 =9.40 +/- 0.19h-1Mpc,γ = 2.02 +/- 0.07 at large scales(s > 4.5h-1Mpc). In the semiprojected correlationfunction, wp(σ), we find a simple power law withγ = 1.83 +/- 0.05 and r0 = 7.30 +/-0.34h-1Mpc fits the data in the range 0.4 < σ <50h-1Mpc, although there is evidence of a steeper power lawat smaller scales. A single power law also fits the deprojectedcorrelation function ξ(r), with a correlation length of r0= 7.45 +/- 0.35h-1Mpc and a power-law slope of γ = 1.72+/- 0.06 in the 0.4 < r < 50h-1Mpc range. But it is inthe LRG angular correlation function that the strongest evidence fornon-power-law features is found where a slope of γ = -2.17 +/-0.07 is seen at 1 < r < 10h-1Mpc with a flatter γ= -1.67 +/- 0.07 slope apparent at r <~ 1h-1Mpc scales.We use the simple power-law fit to the galaxy ξ(r), under theassumption of linear bias, to model the redshift-space distortions inthe 2D redshift-space correlation function, ξ(σ, π). We fitfor the LRG velocity dispersion, wz, the density parameter,Ωm and β(z), where β(z) =Ω0.6m/b and b is the linear bias parameter.We find values of wz =330kms-1,Ωm =0.10+0.35-0.10 and β = 0.40 +/- 0.05. The lowvalues for wz and β reflect the high bias of the LRGsample. These high-redshift results, which incorporate theAlcock-Paczynski effect and the effects of dynamical infall, start tobreak the degeneracy between Ωm and β found inlow-redshift galaxy surveys such as 2dFGRS. This degeneracy is furtherbroken by introducing an additional external constraint, which is thevalue β(z = 0.1) = 0.45 from 2dFGRS, and then considering theevolution of clustering from z ~ 0 to zLRG ~ 0.55. With thesecombined methods we find Ωm(z = 0) = 0.30 +/- 0.15 andβ(z = 0.55) = 0.45 +/- 0.05. Assuming these values, we find a valuefor b(z = 0.55) = 1.66 +/- 0.35. We show that this is consistent with asimple `high-peak' bias prescription which assumes that LRGs have aconstant comoving density and their clustering evolves purely undergravity.