The Sloan Digital Sky Survey: The Cosmic Spectrum and Star-Formation History

Astrophysics, abstract
astro-ph/0301005

From: Karl Glazebrook <kgb@pha.jhu.edu>

Date: Wed, 1 Jan 2003 00:18:04 GMT   (192kb)

The Sloan Digital Sky Survey: The Cosmic Spectrum and Star-Formation History

We present a determination of the `Cosmic Optical Spectrum’ of the Universe,
i.e. the ensemble emission from galaxies, as determined from the red-selected
Sloan Digital Sky Survey main galaxy sample and compare with previous results
of the blue-selected 2dF Galaxy Redshift Survey. Broadly we find good agreement
in both the spectrum and the derived star-formation histories. If we use a
power-law star-formation history model where star-formation rate $propto
(1+z)^eta$ out to z=1, then we find that $eta$ of 2 to 3 is still the most
likely model and there is no evidence for current surveys missing large amounts
of star formation at high redshift. In particular `Fossil Cosmology’ of the
local universe gives measures of star-formation history which are consistent
with direct observations at high redshift. Using the photometry of SDSS we are
able to derive the cosmic spectrum in absolute units (i.e.$ W AA$^{-1}$
Mpc$^{-3}$) at 2–5AA resolution and find good agreement with published
broad-band luminosity densities. For a Salpeter IMF the best fit stellar
mass/light ratio is 3.7–7.5 $Msun/Lsun$ in the r-band (corresponding to
$omstars h = 0.0025$–0.0055) and from both the stellar emission history and
the H$alpha$ luminosity density independently we find a cosmological
star-formation rate of 0.03–0.04 h $Msun$ yr$^{-1}$ Mpc$^{-3}$ today.

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