Yang Y, Zabludoff A, Tremonti C, Eisenstein D, Davé R.
Extended Lyα Nebulae at z sime 2.3: An Extremely Rare and Strongly Clustered Population?. The Astrophysical Journal. 2009;693 :1579-1587.
Publisher's VersionAbstractTo obtain an unbiased sample of bright Lyα blobs (L_{Lyα}≳ 10^{43} erg s-1), we have undertaken a blind,wide-field, narrowband imaging survey in the National Optical AstronomyObservatory Deep Wide Field Survey Boötes field with the StewardBok 2.3 m telescope. After searching over 4.82 deg2 at z =2.3, we discover four Lyα blobs with L_{Lyα} = 1.6-5.3× 1043 erg s-1, isophotal areas of 28-57⊓⊔, and broad Lyα line profiles (Δv = 900-1250km s-1). In contrast with the extended Lyα halosassociated with high-z radio galaxies, none of our four blobs areradio-loud. The X-ray luminosities and optical spectra of these blobsare diverse. Two blobs (3 and 4) are X-ray detected with LX(2-7 keV) = 2-4 × 1044 erg s-1 and havebroad optical emission lines (C IV) characteristic of active galactic
Hickox RC, Jones C, Forman WR, Murray SS, Kochanek CS, Eisenstein D, Jannuzi BT, Dey A, Brown MJI, Stern D, et al. Host Galaxies, Clustering, Eddington Ratios, and Evolution of Radio, X-Ray, and Infrared-Selected AGNs. The Astrophysical Journal. 2009;696 :891-919.
Publisher's VersionAbstractWe 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.
Watson CR, Kochanek CS, Forman WR, Hickox RC, Jones CJ, Brown MJI, Brand K, Dey A, Jannuzi BT, Kenter AT, et al. The Star Formation and Nuclear Accretion Histories of Normal Galaxies in the Ages Survey. The Astrophysical Journal. 2009;696 :2206-2219.
Publisher's VersionAbstractWe 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.
Dai X, Assef RJ, Kochanek CS, Brodwin M, Brown MJI, Caldwell N, Cool RJ, Dey A, Eisenhardt P, Eisenstein D, et al. Mid-Infrared Galaxy Luminosity Functions from the AGN and Galaxy Evolution Survey. The Astrophysical Journal. 2009;697 :506-521.
Publisher's VersionAbstractWe 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
Abazajian KN, Adelman-McCarthy JK, Agüeros MA, Allam SS, Allende Prieto C, An D, Anderson KSJ, Anderson SF, Annis J, Bahcall NA, et al. The Seventh Data Release of the Sloan Digital Sky Survey. The Astrophysical Journal Supplement Series. 2009;182 :543-558.
Publisher's VersionAbstractThis 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.
Thompson RI, Bechtold J, Black JH, Eisenstein D, Fan X, Kennicutt RC, Martins C, Prochaska XJ, Shirley YL.
An Observational Determination of the Proton to Electron Mass Ratio in the Early Universe. The Astrophysical Journal. 2009;703 :1648-1662.
Publisher's VersionAbstractIn 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
Ashby MLN, Stern D, Brodwin M, Griffith R, Eisenhardt P, Kozłowski S, Kochanek CS, Bock JJ, Borys C, Brand K, et al. The Spitzer Deep, Wide-field Survey. The Astrophysical Journal. 2009;701 :428-453.
Publisher's VersionAbstractThe 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
Zheng Z, Zehavi I, Eisenstein DJ, Weinberg DH, Jing YP.
Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies. The Astrophysical Journal. 2009;707 :554-572.
Publisher's VersionAbstractWe 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.