Caltech Faint Galaxy Redshift Survey. XVI. The Luminosity Function for Galaxies in the Region of the Hubble Deep Field–North to z = 1.5
We have carried out a study of the luminosity function (LF) of galaxies in the region of the Hubble Deep Field-North using our very complete redshift catalog. We divide the sample into five redshift bins covering the range 0.01 < z < 1.5 and consider three primary galaxy spectral classes. We solve for the LF at four rest-frame wavelengths from 0.24 to 2.2 μm. We find that the LFs for quiescent galaxies have shallow faint-end slopes while those of galaxies with detectable emission lines have steeper faint-end slopes. Furthermore, these slopes appear to be independent of redshift out to z = 1.05 for each galaxy spectral grouping and agree well with comparable local determinations. We then fix α to obtain values of L* for each galaxy spectral grouping as a function of redshift. We find that galaxies with strong absorption lines become brighter with z with Q ~ 0.6 at all rest-frame bands studied here, where Q = Δ log [L*(z)]/Δz, while galaxies with detectable emission lines (i.e., star-forming galaxies) show a smaller change in L* with redshift at all bands, Q ~ 0.3, with Q becoming significantly larger at rest-frame 2400 Å. Passive evolution models of galaxies are in reasonable agreement with these results for absorption-line-dominated galaxies, while plausible star formation histories can reproduce the behavior of the emission-line galaxies. We find a constant comoving number density and stellar mass in galaxies out to z ~ 1.05. By stretching all the correction factors applied to the galaxy counts in the highest redshift bin to their maximum possible values, we can just barely achieve this between z = 1.05 and 1.3. The major epoch(s) of star formation and of galaxy formation must have occurred even earlier. The UV luminosity density, an indicator of the star formation rate, has increased by a factor of ~4 over the period z = 0-1.
Additional Information© 2002 The American Astronomical Society. Received 2001 July 5; accepted 2001 October 22. Based in large part on observations obtained at the W. M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and NASA. The entire Keck/LRIS user community owes a huge debt to Jerry Nelson, Gerry Smith, Bev Oke, and many other people who have worked to make the Keck Telescope and LRIS a reality. We are grateful to the W. M. Keck Foundation, and particularly its late president, Howard Keck, for the vision to fund the construction of the W. M. Keck Observatory. We thank Roger Blandford and George Efstathiou for helpful discussions. We thank Amy Barger and Len Cowie for access to their unpublished photometric database for the region of the HDF. We thank the referee for constructive and helpful suggestions. This work was not supported by any federal agency.
Published - Cohen_2002_ApJ_567_672.pdf
Accepted Version - 0107107.pdf