Lihwai Lin

The All-wavelength Extended Groth Strip International Survey (AEGIS) Data Sets

In this the first of a series of Letters, we present a panchromatic data set in the Extended Groth Strip region of the sky. Our survey, the All-Wavelength Extended Groth Strip International Survey (AEGIS), aims to study the physical properties and evolutionary processes of galaxies at z ~ 1. It includes the following deep, wide-field imaging data sets: Chandra/ACIS X-ray, GALEX ultraviolet, CFHT/MegaCam Legacy Survey optical, CFHT/CFH12K optical, Hubble Space Telescope/ACS optical and NICMOS near-infrared, Palomar/WIRC near-infrared, Spitzer/IRAC mid-infrared, Spitzer/MIPS far-infrared, and VLA radio continuum. In addition, this region of the sky has been targeted for extensive spectroscopy using the Deep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II 10 m telescope. Our survey is compared to other large multiwavelength surveys in terms of depth and sky coverage.

The Deep Evolutionary Exploratory Probe 2 Galaxy Redshift Survey: The Galaxy Luminosity Function to z ~ 1*

The evolution of the B-band galaxy luminosity function is measured using a sample of more than 11,000 galaxies with spectroscopic redshifts from the DEEP2 Redshift Survey. The rest-frame MB versus U - B color-magnitude diagram of DEEP2 galaxies shows that the color-magnitude bimodality seen in galaxies locally is still present at redshifts z > 1. Dividing the sample at the trough of this color bimodality into predominantly red and blue galaxies, we find that the luminosity function of each galaxy color type evolves differently. Blue counts tend to shift to brighter magnitudes at constant number density, while the red counts remain largely constant at a fixed absolute magnitude. Using Schechter functions with fixed faint-end slopes we find that M for blue galaxies brightens by ~1.3 ? 0.14 mag per unit redshift, with no significant evolution in number density. For red galaxies M brightens somewhat less with redshift, while the formal value of * declines. When the population of blue galaxies is subdivided into two halves using the rest-frame color as the criterion, the measured evolution of both blue subpopulations is very similar.The evolution of the B-band galaxy luminosity function is measured using a sample of more than 11,000 galaxies with spectroscopic redshifts from the DEEP2 Redshift Survey. The rest-frame M_B versus U-B color-magnitude diagram of DEEP2 galaxies shows that the color-magnitude bi-modality seen in galaxies locally is still present at redshifts z > 1. Dividing the sample at the trough of this color bimodality into predominantly red and blue galaxies, we find that the luminosity function of each galaxy color type evolves differently. Blue counts tend to shift to brighter magnitudes at constant number density, while the red counts remain largely constant at a fixed absolute magnitude. Using Schechter functions with fixed faint-end slopes we find that M*_B for blue galaxies brightens by ~ 1.3 magnitudes per unit redshift, with no significant evolution in number density. For red galaxies M*_B brightens somewhat less with redshift, while the formal value of phi* declines. When the population of blue galaxies is subdivided into two halves using the rest-frame color as the criterion, the measured evolution of both blue subpopulations is very similar.

The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts

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 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z ~ 1.45, where the [O ii] 3727 A doublet lies in the infrared. The DEIMOS 1200 line mm^(−1) 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. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z ~ 1, approaching ~5%–10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z ~ 1 in terms of 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.

The Evolution of Galaxy Mergers and Morphology at z < 1.2 in the Extended Groth Strip

We present the quantitative rest-frame B morphological evolution and galaxy merger fraction at 0.2 1011 L☉ are disk galaxies, and only ~15% are classified as major merger candidates. Edge-on and dusty disk galaxies (Sb-Ir) are almost a third of the red sequence at z ~ 1.1, while E/S0/Sa make up over 90% of the red sequence at z ~ 0.3. Approximately 2% of our full sample are red mergers. We conclude (1) the merger rate does not evolve strongly between 0.2 < z < 1.2; (2) the decrease in the volume-averaged star formation rate density since z ~ 1 is a result of declining star formation in disk galaxies rather than a disappearing population of major mergers; (3) the build-up of the red sequence at z < 1 can be explained by a doubling in the number of spheroidal galaxies since z ~ 1.2.

The Redshift Evolution of Wet, Dry, and Mixed Galaxy Mergers from Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey

We study the redshift evolution of galaxy pair fractions and merger rates for different types of galaxies using kinematic pairs selected from the DEEP2 Redshift Survey, combined with other surveys at lower redshifts. By parameterizing the evolution of the pair fraction as -->(1 + z)m, we find that the companion rate increases mildly with redshift with -->m = 0.41 ± 0.20 for all galaxies with – -->21 m = 1.27 ± 0.35, while the red companion rate of red galaxies is better fitted with the negative slope -->m = − 0.92 ± 0.59. For the chosen luminosity range, we find that at low redshift the pair fraction within the red sequence exceeds that of the blue cloud, indicating a higher merger probability among red galaxies compared to that among the blue galaxies. With further assumptions on the merger timescale and the fraction of pairs that will merge, the galaxy major merger rates for -->0.1 10−3 h3 Mpc −3 Gyr −1 with a factor of 2 uncertainty. At -->z ~ 1.1, 68% of mergers are wet, 8% of mergers are dry, and 24% of mergers are mixed, compared to 31% wet mergers, 25% dry mergers, and 44% mixed mergers at -->z ~ 0.1. Wet mergers dominate merging events at -->z = 0.2–1.2, but the relative importance of dry and mixed mergers increases over time. About 22%-54% of present-day -->L* galaxies have experienced major mergers since -->z ~ 1.2, depending on the definition of major mergers. Moreover, 24% of the red galaxies at the present epoch have had dry mergers with luminosity ratios between

The DEEP2 Galaxy Redshift Survey: Evolution of close galaxy pairs and major-merger rates up to z ~ 1.2

1t{:}t 4

SEDS: The Spitzer Extended Deep Survey: survey design, photometry, and deep IRAC source counts

--> and

The relative abundance of compact and normal massive early-type galaxies and its evolution from redshift z~2 to the present

4t{:}t 1

Extragalactic science, cosmology, and Galactic archaeology with the Subaru Prime Focus Spectrograph

--> since -->z ~ 1. Our results also suggest that the wet mergers and/or mixed mergers may be partially responsible for producing red galaxies with intermediate masses, while a significant portion of massive red galaxies are assembled through dry mergers at later times.

GOODS-HERSCHEL: star formation, dust attenuation and the FIR-radio correlation on the Main Sequence of star-forming galaxies up to z~4

We derive the close, kinematic pair fraction and merger rate up to redshift z ~ 1.2 from the initial data of the DEEP2 Redshift Survey. Assuming a mild luminosity evolution, the number of companions per luminous galaxy is found to evolve as (1 + z)m, with m = 0.51 ± 0.28; assuming no evolution, m = 1.60 ± 0.29. Our results imply that only 9% of present-day L* galaxies have undergone major mergers since z ~ 1.2 and that the average major merger rate is about 4 × 10-4 h3 Mpc-3 Gyr-1 for z ~ 0.5-1.2. Most previous studies have yielded higher values.