The DEEP2 and COMBO-17 surveys are compared to study luminosity functions of red and blue galaxies to z $ 1. The two surveys have different methods and sensitivities, but nevertheless results agree. After z $ 1, M à B has dimmed by 1.2Y1.3 mag for all colors of galaxies, à for blue galaxies has hardly changed, and à for red galaxies has at least doubled (our formal value is $0.5 dex). Luminosity density j B has fallen by 0.6 dex for blue galaxies but has remained nearly constant for red galaxies. These results imply that the number and total stellar mass of blue galaxies have been substantially constant since z $ 1, whereas those of red galaxies (near L à ) have been significantly rising. To explain the new red galaxies, a ''mixed'' scenario is proposed in which star formation in blue cloud galaxies is quenched, causing them to migrate to the red sequence, where they merge further in a small number of stellar mergers. This mixed scenario matches the local boxy-disky transition for nearby ellipticals, as well as red sequence stellar population scaling laws such as the color-magnitude and Mg-relations (which are explained as fossil relics from blue progenitors). Blue galaxies enter the red sequence via different quenching modes, each of which peaks at a different characteristic mass and time. The red sequence therefore likely builds up in different ways at different times and masses, and the concept of a single process that is ''downsizing'' (or upsizing) probably does not apply. Our claim in this paper of a rise in the number of red galaxies applies to galaxies near L à . Accurate counts of brighter galaxies on the steep part of the Schechter function require more accurate photometry than is currently available.

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In this paper, we describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ∼ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude M B = −20 at z ∼ 1 via ∼ 90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg 2 divided into four separate fields observed to a limiting apparent magnitude of R AB = 24.1. Objects with z < ∼ 0.7 are readily identifiable using BRI photometry and rejected in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ∼ 2.5 times more efficiently than in a purely magnitude-limited sample. Approximately sixty percent of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets which fail to yield secure redshifts are blue objects that lie beyond z ∼ 1.45, where the [O II] 3727 Å doublet lies in the infrared. The DEIMOS 1200-line/mm grating used for the survey delivers high spectral resolution (R ∼ 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful b-spline modeling methods. Summary data are given that demonstrate the superiority of DEEP2 over other deep redshift surveys at z ∼ 1 in terms of galaxy numbers, redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far.

We derive the close, kinematic pair fraction and merger rate up to redshift from the initial data of the z ∼ 1.2 DEEP2 Redshift Survey. Assuming a mild luminosity evolution, the number of companions per luminous galaxy is found to evolve as , with ; assuming no evolution, . Our results m(1 ϩ z) m p 0.51 ‫ע‬ 0.28 m p 1.60 ‫ע‬ 0.29 imply that only 9% of present-day galaxies have undergone major mergers since and that the average * L z ∼ 1.2 major merger rate is about Mpc Ϫ3 Gyr Ϫ1 for . Most previous studies have yielded higherSubject headings: galaxies: evolution -galaxies: interactions -large-scale structure of universe 1 Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

We study the dependence of star-formation quenching on galaxy mass and environment, in the SDSS (z ∼ 0.1) and the AEGIS (z ∼ 1). It is crucial that we define quenching by low star-formation rate rather than by red colour, given that one third of the red galaxies are star forming. We address stellar mass M * , halo mass M h , density over the nearest N neighbours δ N , and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with M h at fixed M * than with M * at fixed M h , while for satellites quenching also depends on D. We present the M * -M h relation for centrals at z ∼ 1. At z ∼ 1, the dependence of quenching on M * at fixed M h is somewhat more pronouced than at z ∼ 0, but the quenched fraction is low (10%) and the haloes are less massive. For satellites, M * -dependent quenching is noticeable at high D, suggesting a quenching dependence on sub-halo mass for recently captured satellites. At small D, where satellites likely fell in more than a few Gyr ago, quenching strongly depends on M h , and not on M * . The M h -dependence of quenching is consistent with theoretical wisdom where virial shock heating in massive haloes shuts down accretion and triggers ram-pressure stripping, causing quenching. The interpretation of δ N is complicated by the fact that it depends on the number of observed group members compared to N , motivating the use of D as a better measure of local environment.