paper

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

arXiv:astro-ph/0301005 · doi:10.1086/368161

Abstract

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 $\propto (1 + z)^{2}$ out to z=1, then we find that $I^^{2}$ 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. $W A ~$ ^{-1} $M p c$ ^{-3} $) a t 2 - - 5 A ~ r eso l u t i o nan df in d g oo d a g r ee m e n tw i t h p u b l i s h e d b r o a d - ban d l u min os i t y d e n s i t i es . F or a S a l p e t er I M F t h e b es t f i t s t e l l a r ma ss / l i g h t r a t i o i s 3.7 - - 7.5$ \Msun/\Lsun $in t h er - ban d (cor r es p o n d in g t o$ \omstars h = 0.0025 $- - 0.0055) an df r o mb o t h t h es t e l l a r e mi ss i o nhi s t or y an d t h eH$ Î± $l u min os i t y d e n s i t y in d e p e n d e n tl y w e f in d a cos m o l o g i c a l s t a r - f or ma t i o n r a t eo f 0.03 - - 0.04 h$ \Msun $y r$ ^{-1} $M p c$ ^{-3}$ today.

17 pages, 11 figures, ApJ in press (April 10th 2003)