Daniel E. Vanden Berk

Cosmological constraints from the SDSS luminous red galaxies

We measure the large-scale real-space power spectrum P(k) using luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS) and use this measurement to sharpen constraints on cosmological parameters from the Wilkinson Microwave Anisotropy Probe (WMAP). We employ a matrix-based power spectrum estimation method using Pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated minimum-variance measurements in 20 k-bands of both the clustering power and its anisotropy due to redshift-space distortions, with narrow and well-behaved window functions in the range 0.01h/Mpc 0.1h/Mpc and associated nonlinear complications, yet agree well with more aggressive published analyses where nonlinear modeling is crucial.

Spectroscopic Target Selection for the Sloan Digital Sky Survey: The Luminous Red Galaxy Sample

We describe the target selection and resulting properties of a spectroscopic sample of luminous red galaxies (LRGs) from the imaging data of the Sloan Digital Sky Survey (SDSS). These galaxies are selected on the basis of color and magnitude to yield a sample of luminous intrinsically red galaxies that extends fainter and farther than the main flux-limited portion of the SDSS galaxy spectroscopic sample. The sample is designed to impose a passively evolving luminosity and rest-frame color cut to a redshift of 0.38. Additional, yet more luminous red galaxies are included to a redshift of ~0.5. Approximately 12 of these galaxies per square degree are targeted for spectroscopy, so the sample will number over 100,000 with the full survey. SDSS commissioning data indicate that the algorithm efficiently selects luminous (M^+_g ≈ -21.4) red galaxies, that the spectroscopic success rate is very high, and that the resulting set of galaxies is approximately volume limited out to z = 0.38. When the SDSS is complete, the LRG spectroscopic sample will fill over 1 h^(-3) Gpc^3 with an approximately homogeneous population of galaxies and will therefore be well suited to studies of large-scale structure and clusters out to z = 0.5.

Cosmological parameter analysis including SDSS lyα forest and galaxy bias : Constraints on the primordial spectrum of fluctuations, neutrino mass, and dark energy

We combine the constraints from the recent Lyα forest analysis of the Sloan Digital Sky Survey (SDSS) and the SDSS galaxy bias analysis with previous constraints from SDSS galaxy clustering, the latest supernovae, and 1st year WMAP cosmic microwave background anisotropies. We find significant improvements on all of the cosmological parameters compared to previous constraints, which highlights the importance of combining Lyα forest constraints with other probes. combining WMAP and the Lyα forest we find for the primordial slope ns = 0:98±0:02. We see no evidence of running, dn/=d lnk 0:003±0:010, a factor of 3 improvement over previous constraints. We also find no evidence of tensors, r < 0:36 (95% c.l.). Inflationary models predict the absence of running and many among them satisfy these constraints, particularly negative curvature models such as those based on spontaneous symmetry breaking. A positive correlation between tensors and primordial slope disfavors chaotic inflation-type models with steep slopes: while the V αo 2 model is within the 2-sigma contour, V αo4 is outside the 3- sigma contour. For the amplitude we find σ8 = 0:90 ± 0:03 from the Lyα forest and WMAP alone. We find no evidence of neutrino mass: for the case of 3 massive neutrino families with an inflationary prior, Σmv < 0:42 eV and the mass of lightest neutrino is m1 < 0:13 eV at 95% c.l. For the 3 massless +1 massive neutrino case we find mv < 0:79 eV for the massive neutrino, excluding at 95% c.l. all neutrino mass solutions compatible with the LSND results. We explore dark energy constraints in models with a fairly general time dependence of dark energy equation of state, finding Ωλ =0:72± 0:02, w(z = 0:3) = 0:98+0.10 -0.12,the latter changing to w(z = 0:3) = -0.92+0.09-0.10 if tensors are allowed. We find no evidence for variation of the equation of state with redshift, w(z = 1) = -1.03+0.21-0.28. These results rely on the current understanding of the Lyα forest and other probes, which need to be explored further both observationally and theoretically, but extensive tests reveal no evidence of inconsistency among different data sets used here.

Spectral Energy Distributions and Multiwavelength Selection of Type 1 Quasars

We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z ~ 3, with predictions to z = 7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available. We discuss how the spectral diversity of quasars influences the determination of bolometric luminosities and accretion rates; assuming the mean SED can lead to errors as large as 50% for individual quasars when inferring a bolometric luminosity from an optical luminosity. Finally, we show that careful consideration of the shape of the mean quasar SED and its redshift dependence leads to a lower estimate of the fraction of reddened/obscured AGNs missed by optical surveys as compared to estimates derived from a single mean MIR to optical flux ratio.

The Sloan Digital Sky Survey Quasar Survey: Quasar Luminosity Function from Data Release 3

We determine the number counts and z = 0-5 luminosity function for a well-defined, homogeneous sample of quasars from the Sloan Digital Sky Survey (SDSS). We conservatively define the most uniform statistical sample possible, consisting of 15,343 quasars within an effective area of 1622 deg2 that was derived from a parent sample of 46,420 spectroscopically confirmed broad-line quasars in the 5282 deg2 of imaging data from SDSS Data Release 3. The sample extends from i = 15 to 19.1 at z 3 and to i = 20.2 for z 3. The number counts and luminosity function agree well with the results of the Two Degree Field QSO Redshift Survey (2QZ) at redshifts and luminosities at which the SDSS and 2QZ quasar samples overlap, but the SDSS data probe to much higher redshifts than does the 2QZ sample. The number density of luminous quasars peaks between redshifts 2 and 3, although uncertainties in the selection function in this range do not allow us to determine the peak redshift more precisely. Our best-fit model has a flatter bright-end slope at high redshift than at low redshift. For z < 2.4 the data are best fit by a redshift-independent slope of ? = -3.1 [?(L) ? L?]. Above z = 2.4 the slope flattens with redshift to ? -2.37 at z = 5. This slope change, which is significant at the 5 ? level, must be accounted for in models of the evolution of accretion onto supermassive black holes.

The Sloan Digital Sky Survey View of the Palomar-Green Bright Quasar Survey

We investigate the extent to which the Palomar-Green (PG) Bright Quasar Survey (BQS) is complete and representative of the general quasar population by comparing it with imaging and spectroscopy from the Sloan Digital Sky Survey (SDSS). A comparison of SDSS and PG photometry of both stars and quasars reveals the need to apply a color and magnitude recalibration to the PG data. Using the SDSS photometric catalog, we define the PGs parent sample of objects that are not main-sequence stars and simulate the selection of objects from this parent sample using the PG photometric criteria and errors. This simulation shows that the effective U - B cut in the PG survey is U - B 0.5 are inherently rare in bright surveys in any case). We find no evidence for any other systematic incompleteness when comparing the distributions in color, redshift, and FIRST radio properties of the BQS and a BQS-like subsample of the SDSS quasar sample. However, the application of a bright magnitude limit biases the BQS toward the inclusion of objects that are blue in g - i, in particular compared to the full range of g - i colors found among the i-band limited SDSS quasars, and even at i-band magnitudes comparable to those of the BQS objects.

The ensemble photometric variability of ∼25,000 quasars in the Sloan Digital Sky Survey

Using a sample of over 25,000 spectroscopically confirmed quasars from the Sloan Digital Sky Survey, we show how quasar variability in the rest-frame optical/UV regime depends on rest-frame time lag, luminosity, rest wavelength, redshift, the presence of radio and X-ray emission, and the presence of broad absorption line systems. Imaging photometry is compared with three-band spectrophotometry obtained at later epochs spanning time lags up to about 2 yr. The large sample size and wide range of parameter values allow the dependence of variability to be isolated as a function of many independent parameters. The time dependence of variability (the structure function) is well fitted by a single power law with an index γ = 0.246 ± 0.008, on timescales from days to years. There is an anticorrelation of variability amplitude with rest wavelength—e.g., quasars are about twice as variable at 1000 A as at 6000 A—and quasars are systematically bluer when brighter at all redshifts. There is a strong anticorrelation of variability with quasar luminosity—variability amplitude decreases by a factor of about 4 when luminosity increases by a factor of 100. There is also a significant positive correlation of variability amplitude with redshift, indicating evolution of the quasar population or the variability mechanism. We parameterize all of these relationships. Quasars with ROSAT All-Sky Survey X-ray detections are significantly more variable (at optical/UV wavelengths) than those without, and radio-loud quasars are marginally more variable than their radio-quiet counterparts. We find no significant difference in the variability of quasars with and without broad absorption line troughs. Currently, no models of quasar variability address more than a few of these relationships. Models involving multiple discrete events or gravitational microlensing are unlikely by themselves to account for the data. So-called accretion disk instability models are promising, but more quantitative predictions are needed.

OPTICAL AND RADIO PROPERTIES OF EXTRAGALACTIC SOURCES OBSERVED BY THE FIRST SURVEY AND THE SLOAN DIGITAL SKY SURVEY

We discuss the optical and radio properties of ~30,000 FIRST (radio, 20 cm, sensitive to 1 mJy) sources positionally associated within 15 with a Sloan Digital Sky Survey (SDSS) (optical, sensitive to r* ~ 22.2) source in 1230 deg2 of sky. The matched sample represents ~30% of the 108,000 FIRST sources and 0.1% of the 2.5 ? 107 SDSS sources in the studied region. SDSS spectra are available for 4300 galaxies and 1154 quasars from the matched sample and for a control sample of 140,000 galaxies and 20,000 quasars in 1030 deg2 of sky. Here we analyze only core sources, which dominate the sample; the fraction of SDSS-FIRST sources with complex radio morphology is determined to be less than 10%. This large and unbiased catalog of optical identifications provides much firmer statistical footing for existing results and allows several new findings. The majority (83%) of the FIRST sources identified with an SDSS source brighter than r* = 21 are optically resolved; the fraction of resolved objects among the matched sources is a function of the radio flux, increasing from ~50% at the bright end to ~90% at the FIRST faint limit. Nearly all optically unresolved radio sources have nonstellar colors indicative of quasars. We estimate an upper limit of ~5% for the fraction of quasars with broadband optical colors indistinguishable from those of stars. The distribution of quasars in the radio flux?optical flux plane suggests the existence of the quasar radio dichotomy; 8% ? 1% of all quasars with i* 2.22) galaxies, especially those with r* > 17.5. Magnitude- and redshift-limited samples show that radio galaxies have a different optical luminosity distribution than nonradio galaxies selected by the same criteria; when galaxies are further separated by their colors, this result remains valid for both blue and red galaxies. For a given optical luminosity and redshift, the observed optical colors of radio galaxies are indistinguishable from those of all SDSS galaxies selected by identical criteria. The distributions of radio-to-optical flux ratio are similar for blue and red galaxies in redshift-limited samples; this similarity implies that the difference in their luminosity functions and resulting selection effects are the dominant cause for the preponderance of red radio galaxies in flux-limited samples. The fraction of radio galaxies whose emission-line ratios indicate an AGN (30%), rather than starburst, origin is 6 times larger than the corresponding fraction for all SDSS galaxies (r* < 17.5). We confirm that the AGN-to-starburst galaxy number ratio increases with radio flux and find that radio emission from AGNs is more concentrated than radio emission from starburst galaxies.

The Linear Theory Power Spectrum from the Lyα Forest in the Sloan Digital Sky Survey

We analyze the SDSS Lyα forest PF(k, z) measurement to determine the linear theory power spectrum. Our analysis is based on fully hydrodynamic simulations, extended using hydro-particle-mesh simulations. We account for the effect of absorbers with damping wings, which leads to an increase in the slope of the linear power spectrum. We break the degeneracy between the mean level of absorption and the linear power spectrum without significant use of external constraints. We infer linear theory power spectrum amplitude Δ(kp = 0.009 s km-1, zp = 3.0) = 0.452 and slope neff(kp, zp) = -2.321 (possible systematic errors are included through nuisance parameters in the fit: a factor 5 smaller errors would be obtained on both parameters if we ignored modeling uncertainties). The errors are correlated and not perfectly Gaussian, so we provide a χ2 table to accurately describe the results. The result corresponds to σ8 = 0.85, n = 0.94 for a ΛCDM model with Ωm = 0.3, Ωb = 0.04, and h = 0.7 but is most useful in a combined fit with the CMB. The inferred curvature of the linear power spectrum and the evolution of its amplitude and slope with redshift are consistent with expectations for ΛCDM models, with the evolution of the slope, in particular, being tightly constrained. We use this information to constrain systematic contamination, e.g., fluctuations in the UV background. This paper should serve as a starting point for more work to refine the analysis, including technical improvements such as increasing the size and number of the hydrodynamic simulations and improvements in the treatment of the various forms of feedback from galaxies and quasars.

A CATALOG OF BROAD ABSORPTION LINE QUASARS IN SLOAN DIGITAL SKY SURVEY DATA RELEASE 5

We present a catalog of 5039 broad absorption line (BAL) quasars (QSOs) in the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) QSO catalog that have absorption troughs covering a continuous velocity range ≥2000 km s–1. We have fitted ultraviolet (UV) continua and line emission in each case, enabling us to report common diagnostics of BAL strengths and velocities in the range –25, 000 to 0 km s–1 for Si IV λ1400, C IV λ1549, Al III λ1857, and Mg II λ2799. We calculate these diagnostics using the spectrum listed in the DR5 QSO catalog, and also for spectra from additional SDSS observing epochs when available. In cases where BAL QSOs have been observed with Chandra or XMM-Newton, we report the X-ray monochromatic luminosities of these sources. We confirm and extend previous findings that BAL QSOs are more strongly reddened in the rest-frame UV than non-BAL QSOs, and that BAL QSOs are relatively X-ray weak compared to non-BAL QSOs. The observed BAL fraction is dependent on the spectral signal-to-noise ratio (S/N); for higher S/N sources, we find an observed BAL fraction of ≈ 15%. BAL QSOs show a similar Baldwin effect as for non-BAL QSOs, in that their C IV emission equivalent widths decrease with increasing continuum luminosity. However, BAL QSOs have weaker C IV emission in general than do non-BAL QSOs. Sources with higher UV luminosities are more likely to have higher-velocity outflows, and the BAL outflow velocity and UV absorption strength are correlated with relative X-ray weakness. These results are in qualitative agreement with models that depend on strong X-ray absorption to shield the outflow from overionization and enable radiative acceleration. In a scenario in which BAL trough shapes are primarily determined by outflow geometry, observed differences in Si IV and C IV trough shapes would suggest that some outflows have ion-dependent structure.