Search

Galactic winds are a prime suspect for the metal enrichment of the intergalactic medium and may have a strong influence on the chemical evolution of galaxies and the nature of QSO absorption line systems. We use a sample of 1406 galaxy spectra at z~1.4 from the DEEP2 redshift survey to show that blueshifted Mg II 2796, 2803 A absorption is ubiquitous in starforming galaxies at this epoch. This is the first detection of frequent outflowing galactic winds at z~1. The presence and depth of absorption are independent of AGN spectral signatures or galaxy morphology; major mergers are not a prerequisite for driving a galactic wind from massive galaxies. Outflows are found in coadded spectra of galaxies spanning a range of 30x in stellar mass and 10x in star formation rate (SFR), calibrated from K-band and from MIPS IR fluxes. The outflows have column densities of order N_H ~ 10^20 cm^-2 and characteristic velocities of ~ 300-500 km/sec, with absorption seen out to 1000 km/sec in the most massive, highest SFR galaxies. The velocities suggest that the outflowing gas can escape into the IGM and that massive galaxies can produce cosmologically and chemically significant outflows. Both the Mg II equivalent width and the outflow velocity are larger for galaxies of higher stellar mass and SFR, with V_wind ~ SFR^0.3, similar to the scaling in low redshift IR-luminous galaxies. The high frequency of outflows in the star-forming galaxy population at z~1 indicates that galactic winds occur in the progenitors of massive spirals as well as those of ellipticals. The increase of outflow velocity with mass and SFR constrains theoretical models of galaxy evolution that include feedback from galactic winds, and may favor momentum-driven models for the wind physics., Comment: Accepted by ApJ. 25 pages, 17 figures. Revised to add discussions of intervening absorbers and AGN-driven outflows; conclusions unchanged

We present the first results of a search for Lyman-alpha emitters (LAEs) in the DEEP2 spectroscopic database that uses a search technique that is different from but complementary to traditional narrowband imaging surveys. We have visually inspected ~20% of the available DEEP2 spectroscopic data and have found nine high-quality LAEs with clearly asymmetric line profiles and an additional ten objects of lower quality, some of which may also be LAEs. Our survey is most sensitive to LAEs at z=4.4-4.9 and that is indeed where all but one of our high-quality objects are found. We find the number density of our spectroscopically-discovered LAEs to be consistent with those found in narrowband imaging searches. The combined, averaged spectrum of our nine high-quality objects is well fit by a two-component model, with a second, lower-amplitude component redshifted by ~420 km/s with respect to the primary Lyman-alpha line, consistent with large-scale outflows from these objects. We conclude by discussing the advantages and future prospects of blank-sky spectroscopic surveys for high-z LAEs.

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.

Using the first 25% of DEEP2 Redshift Survey data, we probe the line-of-sight velocity dispersion profile for isolated galaxies with absolute B-band magnitude -22

DEEP2 is a major new Keck spectroscopic survey of 50,000 galaxies that aims to provide a detailed map of the cosmos at redshift z ∼ 1. We present an overview of DEEP2 and its relation to DEEP and its predecessor (DEEP1) in terms of science goals, of the instrument DEIMOS that enables completion of this survey in only a few years, and of the current status of the project. First science projects that use the first 10% of the survey data and their early results are highlighted.

We present a set of mock redshift catalogs, constructed from N-body simulations, designed to mimic the DEEP2 survey. Galaxies with a range of luminosities are placed within virialized halos in the simulation using a variant of the halo model. The halo model parameters are chosen to reproduce local clustering and abundance data and assumed to be independent of redshift. This allows us to predict the luminosity function, two-point correlation function, luminosity- and scale-dependent bias, redshift space distortions etc. of our galaxies at higher redshifts. We show that the low order clustering properties are consistent with preliminary DEEP2 data. The catalogs can be used to evaluate the selection effects of the survey and to test new algorithms and statistics that are to be used in the analysis of DEEP2 data., Comment: 13 pages, 14 figures. Revised version accepted by ApJ. Added a figure showing agreement with COMBO-17 Luminosity Function

We present a Principal Component Analysis (PCA)-based spectral classification, eta, for the first 5600 galaxies observed in the DEEP2 Redshift Survey. This parameter provides a very pronounced separation between absorption and emission dominated galaxy spectra - corresponding to passively evolving and actively star-forming galaxies in the survey respectively. In addition it is shown that despite the high resolution of the observed spectra, this parameter alone can be used to quite accurately reconstruct any given galaxy spectrum, suggesting there are not many `degrees of freedom' in the observed spectra of this galaxy population. It is argued that this form of classification, eta, will be particularly valuable in making future comparisons between high and low-redshift galaxy surveys for which very large spectroscopic samples are now readily available, particularly when used in conjunction with high-resolution spectral synthesis models which will be made public in the near future. We also discuss the relative advantages of this approach to distant galaxy classification compared to other methods such as colors and morphologies. Finally, we compare the classification derived here with that adopted for the 2dF Galaxy Redshift Survey and in so doing show that the two systems are very similar. This will be particularly useful in subsequent analyses when making comparisons between results from each of these surveys to study evolution in the galaxy populations and large-scale structure.

We use the latest observations from the 2dF Galaxy Redshift Survey to fit the conditional luminosity function (CLF) formulation of the halo-model for galaxies at z=0. This fit is then used to test the extent of evolution in the halo occupation distribution (HOD) to z=0.8, by comparing the predicted clustering from this CLF to preliminary results from the DEEP2 Redshift Survey. We show that the current observations from the DEEP2 Redshift Survey are remarkably consistent with no evolution in the CLF from z=0 to z=0.8. This result is surprising, in that it suggests that there has been very little change in the way galaxies occupy their host dark matter halos over half the age of the Universe. We discuss in detail the observational constraints we have adopted and also the various different selection effects in each survey and how these impact on the galaxy populations encountered in each survey., 11 pages, 5 figures. Minor modifications to match version accepted by ApJ

In a previous paper, we described a new variant on the classical dN/dz test which could be performed using upcoming redshift surveys. By observing the velocity function of galaxies rather than their luminosity function, it is possible to avoid many of the uncertainties of galaxy evolution while employing a directly measurable quantity. We previously assumed that counting statistics would dominate the errors in this method. Here, we present the results of including cosmic variance and determine the impact of systematic effects on application of this test to the upcoming DEEP2 Redshift Survey. For DEEP2, cosmic variance should yield errors roughly twice those predicted from Poisson statistics. Through Monte Carlo simulations we find that if the functional form, but not the strength, of any of the major systematic effects (baryonic infall, velocity errors, and incompleteness) is known, the systematic may successfully be corrected for using the observed velocity function, leaving a much smaller residual error. The total uncertainty from systematics is comparable to that from cosmic variance, but correlated amongst redshift bins. We find that DEEP2 can provide a much more precise measurement of the cosmic equation of state parameter w than any available today, albeit weaker than some other proposed tests., Comment: 10 pages plus 11 figures and 2 tables; approved for publication in the Astrophysical Journal

The abundances of groups and clusters of galaxies are expected to have changed substantially since high redshift, with the strength of this evolution dependent upon fundamental cosmological parameters. Upcoming large redshift surveys of distant galaxies will make it possible to measure these quantities at z~1; when combined with the results of local redshift surveys currently underway, the evolution of cluster abundances may be determined. The DEEP2 Redshift Survey, planned to begin in Spring 2002, is particularly well-suited for this work because of the high spectroscopic resolution to be used; velocity dispersions of groups will be readily measurable. In this paper, we determine the constraints on dark energy models that counts of DEEP2 clusters should provide. We find that comparing cosmological models using the simultaneous distribution of clusters in both velocity dispersion and redshift yields significantly stronger constraints than the redshift distribution alone. The method can be made more powerful by employing a value of the fluctuation amplitude sigma_8 determined with upcoming techniques (external to DEEP2) that have no Omega_m degeneracy. The equation-of-state parameter for dark energy models, w=P/rho, can then be measured to ~0.1 from observations of clusters alone., 10 pages plus 5 figures; approved for publication in PASP

We report a Giant Metrewave Radio Telescope search for H i 21 cm emission from a large sample of massive star-forming galaxies at z ≈ 1.18–1.34, lying in sub-fields of the DEEP2 Redshift Survey. The search was carried out by co-adding ("stacking") the H i 21 cm emission spectra of 857 galaxies, after shifting each galaxy's H i 21 cm spectrum to its rest frame. We obtain the 3σ upper limit SH i 1. The implied limit on the average atomic gas mass fraction (relative to stars) is MGAS/M* < 0.5, comparable to the cold molecular gas mass fraction in similar star-forming galaxies at these redshifts. We find that the cosmological mass density of neutral atomic gas in massive star-forming galaxies at z ≈ 1.3 is ΩGAS < 3.7 × 10−4, significantly lower than ΩGAS estimates in both galaxies in the local universe and damped Lyα absorbers at z ≥ 2.2. Massive blue star-forming galaxies thus do not appear to dominate the neutral atomic gas content of the universe at z ≈ 1.3.

We study the frequency of Mg II absorption in the outer haloes of galaxies at z = 0.6 - 1.4 (with median z = 0.87), using new spectra obtained of ten background quasars with galaxy impact parameters of b < 100 kpc. The quasar sightlines were selected from the SDSS DR6 QSO catalog based on proximity to galaxies in the DEEP2 redshift survey. In addition to the 10 small impact systems, we examine 40 additional galaxies at 100 < b < 500 kpc serendipitously located in the same fields. We detect Mg II absorbers with equivalent width W_r = 0.15 A - 1.0 A, though not all absorbers correlate with DEEP galaxies. We find five unique absorbers within ��v = 500 km/s and b < 100 kpc of a DEEP galaxy; this small sample contains both early and late type galaxies and has no obvious trends with star formation rate. No Mg II is detected more than 100 kpc from galaxies; inside this radius the covering fraction scales with impact parameter and galaxy luminosity in very similar fashion to samples studied at lower redshift. In all but one case, when Mg II is detected without a spectroscopically confirmed galaxy, there exists a plausible photometric candidate which was excluded because of slit collision or apparent magnitude. We do not detect any strong absorbers with W_r > 1.0 A, consistent with other samples of galaxy-selected Mg II systems. We speculate that Mg II systems with 0.3 < W_r < 1.0 trace old relic material from galactic outflows and/or the halo assembly process, and that in contrast, systems with large W_r are more likely to reflect the more recent star forming history of their associated galaxies., 19 pages, 19 figures, accepted to ApJ; v2 fixed minor errors

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. 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_B^{e} < -19. Blue galaxies show slightly faster evolution in the blue companion rate with m = 1.27+-0.35 while red galaxies have had fewer red companions in the past as evidenced by the negative slope m = -0.92+-0.59. 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 < z, 11 pages, 8 figures, ApJ Accepted, minor changes to match the journal proof version

The DEIMOS spectrograph is nearing completion in the UC Lick shops and will be delivered to the Keck Observatory in 2001. Once it is operational, a team of astronomers will initiate DEEP2, a major redshift survey of galaxies that will consume approximately 120 nights at the Keck Observatory over a three year period. Our goal is to gather high-quality spectra of ~60,000 galaxies with Z>0.7 in order to study the properties and large scale clustering of galaxies at $Z \approx 1$. The survey will be done at high spectral resolution, R=\lambda/\Delta \lambda ~3500, allowing us to work between the bright OH sky emission lines and to infer linewidths for many of the target galaxies. The linewidth data will facilitate the execution of the classical redshift-volume cosmological test, which can provide a precision measurement of the equation of state of the Universe.

We present measurements of the void probability function (VPF) at z~1 using data from the DEEP2 Redshift Survey and its evolution to z~0 using data from the Sloan Digital Sky Survey (SDSS). We measure the VPF as a function of galaxy color and luminosity in both surveys and find that it mimics trends displayed in the two-point correlation function, $\xi$; namely that samples of brighter, red galaxies have larger voids (i.e. are more strongly clustered) than fainter, blue galaxies. We also clearly detect evolution in the VPF with cosmic time, with voids being larger in comoving units at z~0. We find that the reduced VPF matches the predictions of a `negative binomial' model for galaxies of all colors, luminosities, and redshifts studied. This model lacks a physical motivation, but produces a simple analytic prediction for sources of any number density and integrated two-point correlation function, \bar{\xi}. This implies that differences in the VPF across different galaxy populations are consistent with being due entirely to differences in the population number density and \bar{\xi}. The robust result that all galaxy populations follow the negative binomial model appears to be due to primarily to the clustering of dark matter halos. The reduced VPF is insensitive to changes in the parameters of the halo occupation distribution, in the sense that halo models with the same \bar{\xi} will produce the same VPF. For the wide range of galaxies studied, the VPF therefore does not appear to provide useful constraints on galaxy evolution models that cannot be gleaned from studies of \bar{\xi} alone. (abridged), Comment: 17 pages, 15 figures, ApJ accepted

We derive the close, kinematic pair fraction and merger rate up to 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} h^{3} Mpc^{-3} Gyr^{-1} for z ~ 0.5 - 1.2. Most previous studies have yielded higher values., Comment: 12 pages, 3 figures, minor changes to match the ApJL version

The DEIMOS spectrograph has now been installed on the Keck-II telescope and commissioning is nearly complete. The DEEP2 Redshift Survey, which will take approximately 120 nights at the Keck Observatory over a three year period and has been designed to utilize the power of DEIMOS, began in the summer of 2002. The multiplexing power and high efficiency of DEIMOS enables us to target 1000 faint galaxies per clear night. Our goal is to gather high-quality spectra of \~60,000 galaxies with z>0.75 in order to study the properties and large scale clustering of galaxies at z ~ 1. The survey will be executed at high spectral resolution, $R=\lambda/\Delta \lambda \approx 5000$, allowing us to work between the bright OH sky emission lines and to infer linewidths for many of the target galaxies (for several thousand objects, we will obtain rotation curves as well). The linewidth data will facilitate the execution of the classical redshift-volume cosmological test, which can provide a precision measurement of the equation of state of the Universe. This talk reviews the project, summarizes our science goals and presents some early DEIMOS data., Comment: 12 pages, 5 figures, talk presented at SPIE conference, Aug. 2002

We present a star-formation rate calibration based on optical data that is consistent with average observed rates in both the red and blue galaxy populations at z~1. The motivation for this study is to calculate SFRs for DEEP2 Redshift Survey galaxies in the 0.7, Comment: 16 pages, 15 figures, emulateapj format, to be submitted to ApJ