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The Norris Survey of the Corona Borealis Supercluster. II. Galaxy Evolution with Redshift and Environment

1997; IOP Publishing; Volume: 487; Issue: 2 Linguagem: Inglês

10.1086/304619

1538-4357

Todd A. Small, W. L. W. Sargent, Donald Hamilton,

Stellar, planetary, and galactic studies

We measure the field galaxy luminosity function (LF) as a function of color and redshift from z = 0 to z = 0.5 using galaxies from the Norris Survey of the Corona Borealis Supercluster. The data set consists of 603 field galaxies with 0 < z ≤ 0.5 and spans a wide range in apparent magnitude (14.0 ≲ r ≲ 21.5), although our field galaxy LF analysis is limited to 493 galaxies with r ≤ 20.0 mag. We use the observed g-r colors of the galaxies to compute accurate corrections to the rest BAB and r bands. We find that our local r-band LF, when normalized to counts in high galactic latitude fields, agrees well with the local LF measured in the Las Campanas Redshift Survey. Our BAB-band local LF, however, does not match the bj-band LF from the Stromlo/APM survey, having a normalization 1.6 times higher. We see compelling evidence that the BAB-band field galaxy LF evolves with redshift. The evolution is strongest for the population of star-forming galaxies with [O II] λ3727 rest-frame equivalent widths greater than 10 Å. The population of red, quiescent galaxies shows no sign of evolution to z = 0.5. The evolution of the LF that we observe is consistent with the findings of other faint galaxy redshift surveys. The fraction of galaxies with [O II] emission increases rapidly with redshift, but the fraction of galaxies with strong Hδ absorption, a signature of a burst of star formation, does not. We thus conclude that the star formation in distant galaxies is primarily long-lived.