66 research outputs found
The Galaxy Luminosity Function and Luminosity Density at Redshift z=0.1
Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital Sky Survey (SDSS), we measure the galaxy luminosity density at z = 0.1 in five optical bandpasses corresponding to the SDSS bandpasses shifted to match their rest-frame shape at z = 0.1. We denote the bands (0.1)u, (0.1)g, (0.1)r, (0.1)i, (0.1)z with lambda(eff) = (3216; 4240; 5595; 6792; 8111 Angstrom), respectively. To estimate the luminosity function, we use a maximum likelihood method that allows for a general form for the shape of the luminosity function,fits for simple luminosity and number evolution, incorporates the flux uncertainties, and accounts for the flux limits of the survey. We find luminosity densities at z = 0.1 expressed in absolute AB magnitudes in a Mpc(3) to be (-14.10 +/- 0.15, -15.18 +/- 0.03, - 15.90 +/- 0.03, -16.24 +/- 0.03, -16.56 +/- 0.02) in ((0.1)u, (0.1)g, (0.1)r, (0.1)i, (0.1)z), respectively, for a cosmological model with Omega(0) = 0.3, Omega(Lambda) = 0.7, and h = 1 and using SDSS Petrosian magnitudes. Similar results are obtained using Sersic model magnitudes, suggesting that flux from outside the Petrosian apertures is not a major correction. In the (0.1)r band, the best-fit Schechter function to our results has phi* = (1.49 +/- 0.04) x 10(-2) h(3) Mpc(-3), M-* - 5 log(10) h = - 20.44 +/- 0.01, and alpha = - 1.05 +/- 0.01. In solar luminosities, the luminosity density in (0.1)r is (1.84 +/- 0.04) x 10(8) h L-0.1r,L-. Mpc(-3). Our results in the (0.1)g band are consistent with other estimates of the luminosity density, from the Two-Degree Field Galaxy Redshift Survey and the Millennium Galaxy Catalog. They represent a substantial change ( similar to 0.5 mag) from earlier SDSS luminosity density results based on commissioning data, almost entirely because of the inclusion of evolution in the luminosity function model
The shape of the SDSS DR5 galaxy power spectrum
We present a Fourier analysis of the clustering of galaxies in the combined
Main galaxy and Luminous Red Galaxy (LRG) Sloan Digital Sky Survey (SDSS) Data
Release 5 (DR5) sample. The aim of our analysis is to consider how well we can
measure the cosmological matter density using the signature of the horizon at
matter-radiation equality embedded in the large-scale power spectrum. The new
data constrains the power spectrum on scales 100--600h^-1Mpc with significantly
higher precision than previous analyses of just the SDSS Main galaxies, due to
our larger sample and the inclusion of the LRGs. This improvement means that we
can now reveal a discrepancy between the shape of the measured power and linear
CDM models on scales 0.01<k<0.15hMpc^-1, with linear model fits favouring a
lower matter density (Omega_m=0.22+/-0.04) on scales 0.01<k<0.06hMpc^-1 and a
higher matter density (Omega_m=0.32+/-0.01) when smaller scales are included,
assuming a flat LCDM model with h=0.73 and n_s=0.96. This discrepancy could be
explained by scale-dependent bias and, by analysing subsamples of galaxies, we
find that the ratio of small-scale to large-scale power increases with galaxy
luminosity, so all of the SDSS galaxies cannot trace the same power spectrum
shape over 0.01<k<0.2hMpc^-1. However, the data are insufficient to clearly
show a luminosity-dependent change in the largest scale at which a significant
increase in clustering is observed, although they do not rule out such an
effect. Significant scale-dependent galaxy bias on large-scales, which changes
with the r-band luminosity of the galaxies, could potentially explain
differences in our Omega_m estimates and differences previously observed
between 2dFGRS and SDSS power spectra and the resulting parameter constraints.Comment: 21 pages, 19 figures, minor corrections to match version accepted by
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