Marc Davis

University of California, Berkeley

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Christopher N. A. Willmer

University of Arizona

Michael C. Cooper

University of California, Irvine

Alison L. Coil

University of California, San Diego

Jeffrey A. Newman

University of Pittsburgh

Renbin Yan

Chinese University of Hong Kong

Benjamin J. Weiner

University of Arizona

David C. Koo

University of California, Santa Cruz

Brian F. Gerke

Lawrence Berkeley National Laboratory

Puragra Guhathakurta

University of California, Santa Cruz

S. M. Faber

University of California, Santa Cruz

Cooperative Institutions

University of California, Berkeley

University of California, Santa Cruz

Max Planck Society

Max Planck Institute for Astronomy

University of Arizona

Center for Astrophysics Harvard & Smithsonian

Centre National de la Recherche Scientifique

California Institute of Technology

The University of Tokyo

Max Planck Institute for Extraterrestrial Physics

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The DEEP3 Galaxy Redshift Survey: the impact of environment on the size evolution of massive early-type galaxies at intermediate redshift★†

Monthly Notices of the Royal Astronomical Society (2011)

Michael C. Cooper Roger L. Griffith Jeffrey A. Newman Alison L. Coil Marc Davis

Using data drawn from the DEEP2 and DEEP3 Galaxy Redshift Surveys, we investigate the relationship between the environment and the structure of galaxies residing on the red sequence at intermediate redshift. Within the massive (10 < log(M*/Msun) < 11) early-type population at 0.4 < z <1.2, we find a significant correlation between local galaxy overdensity (or environment) and galaxy size, such that early-type systems in higher-density regions tend to have larger effective radii (by ~0.5 kpc or 25% larger) than their counterparts of equal stellar mass and Sersic index in lower-density environments. This observed size-density relation is consistent with a model of galaxy formation in which the evolution of early-type systems at z < 2 is accelerated in high-density environments such as groups and clusters and in which dry, minor mergers (versus mechanisms such as quasar feedback) play a central role in the structural evolution of the massive, early-type galaxy population.

10.1111/j.1365-2966.2011.19938.x

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Citations (128)

A Summary of the Observations of the Twin QSOs, 0957+561 A,B

Springer eBooks (1980)

Frederic H. Chaffee R. J. Weymann Marc Davis N. P. Carleton D. Walsh

QSOS

10.1007/978-94-009-9040-1_30

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Citations (0)

Absence of evidence is not evidence of absence: the colour-density relation at fixed stellar mass persists to z∼ 1★

Monthly Notices of the Royal Astronomical Society (2010)

Michael C. Cooper Alison L. Coil Brian F. Gerke Jeffrey A. Newman Kevin Bundy

We use data drawn from the DEEP2 Galaxy Redshift Survey to investigate the relationship between local galaxy density, stellar mass, and rest-frame galaxy color. At z ~ 0.9, we find that the shape of the stellar mass function at the high-mass (log (M*/Msun) > 10.1) end depends on the local environment, with high-density regions favoring more massive systems. Accounting for this stellar mass-environment relation (i.e., working at fixed stellar mass), we find a significant color-density relation for galaxies with 10.6 < log(M*/Msun) < 11.1 and 0.75 < z < 0.95. This result is shown to be robust to variations in the sample selection and to extend to even lower masses (down to log(M*/Msun) ~ 10.4). We conclude by discussing our results in comparison to recent works in the literature, which report no significant correlation between galaxy properties and environment at fixed stellar mass for the same redshift and stellar mass domain. The non-detection of environmental dependence found in other data sets is largely attributable to their smaller samples size and lower sampling density, as well as systematic effects such as inaccurate redshifts and biased analysis techniques. Ultimately, our results based on DEEP2 data illustrate that the evolutionary state of a galaxy at z ~ 1 is not exclusively determined by the stellar mass of the galaxy. Instead, we show that local environment appears to play a distinct role in the transformation of galaxy properties at z > 1.

Stellar mass

10.1111/j.1365-2966.2010.17312.x

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Citations (61)

The DEEP2 galaxy redshift survey: evolution of the colour–density relation at 0.4 < z < 1.35

Monthly Notices of the Royal Astronomical Society (2007)

Michael C. Cooper Jeffrey A. Newman Alison L. Coil Darren Croton Brian F. Gerke

Using a sample of 19 464 galaxies drawn from the DEEP2 Galaxy Redshift Survey, we study the relationship between galaxy colour and environment at 0.4 < z < 1.35. We find that the fraction of galaxies on the red sequence depends strongly on local environment out to z > 1, being larger in regions of greater galaxy density. At all epochs probed, we also find a small population of red, morphologically early-type galaxies residing in regions of low measured overdensity. The observed correlations between the red fraction and local overdensity are highly significant, with the trend at z > 1 detected at a greater than 5σ level. Over the entire redshift regime studied, we find that the colour–density relation evolves continuously, with red galaxies more strongly favouring overdense regions at low z relative to their red-sequence counterparts at high redshift. At z≳ 1.3, the red fraction only weakly correlates with overdensity, implying that any colour dependence to the clustering of ∼L* galaxies at that epoch must be small. Our findings add weight to existing evidence that the build-up of galaxies on the red sequence has occurred preferentially in overdense environments (i.e. galaxy groups) at z≲ 1.5. Furthermore, we identify the epoch (z∼ 2) at which typical ∼L* galaxies began quenching and moved on to the red sequence in significant number. The strength of the observed evolutionary trends at 0 < z < 1.35 suggests that the correlations observed locally, such as the morphology–density and colour–density relations, are the result of environment-driven mechanisms (i.e. 'nurture') and do not appear to have been imprinted (by 'nature') upon the galaxy population during their epoch of formation.

10.1111/j.1365-2966.2007.11534.x

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Citations (190)

Gravitational clustering from scale-free initial conditions

Monthly Notices of the Royal Astronomical Society (1988)

G. Efstathiou Carlos S. Frenk Simon D. M. White Marc Davis

We present results of a series of N-body experiments designed to study gravitational clustering from scale-free initial conditions in an Einstein–de Sitter universe. The initial density fluctuations are assumed to be Gaussian with power spectra of the form |$|\delta_\text k|^2\propto k^n$| where n = 1, 0, −1 and −2. Evolution from such initial conditions is expected to be self-similar in time, and we are able to verify the expected similarity scalings for a wide range of properties. As expected, we obtain steeper autocorrelation functions for more positive values of n, but in no case do we find power law behaviour over the range of clustering strengths for which it is exhibited by the real galaxy distribution. Deviations from the asymptotic scaling predicted for a stable clustering hierarchy are related to the behaviour of the mean relative velocity of particle pairs. For all n the reduced three-point correlation is well modelled by the standard quadratic form but the coefficient Q is anticorrelated with n. The abundance of non-linear clumps as a function of mass (the multiplicity function) is a strong function of n and is in good agreement with the theory of Press & Schechter. At high density contrast most clumps show a monolithic core–halo structure rather than a hierarchical arrangement of sub-clumps. After its first collapse a typical clump survives until the mean mass of clusters has increased by about a factor of 100 before it is disrupted by incorporation into a larger system. Massive clumps at any time tend to be made preferentially of the largest clumps which were present at earlier times; this effect could be important in biasing the galaxy distribution relative to that of the mass. We show how such biases can be understood using a simple modification of the Press–Schechter theory. The density profiles of clumps are shallower for more negative n, but the corresponding circular velocity curves are poorly represented by power laws. Their slopes depend on the overdensity at which they are measured as well as on n. At high overdensities the circular velocity curves for n=−2 are approximately flat; at overdensities of a few hundred they are falling for all values of n. We investigate the three-dimensional shapes, the angular momenta and the internal velocity distribution of clumps. Our results show that these quantities depend only slightly on n. In general, although non-linear clustering destroys the hierarchical arrangement of the initial conditions, we find that their scaling properties still determine the scaling properties of the mass distribution at high density contrast. Thus it should be possible to infer the initial conditions for galaxy formation from the structure of galaxy halos at radii r≳50 kpc.

Peculiar velocity

10.1093/mnras/235.3.715

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Citations (353)

The DEEP2 galaxy redshift survey: the evolution of the blue fraction in groups and the field

Monthly Notices of the Royal Astronomical Society (2007)

Brian F. Gerke Jeffrey A. Newman S. M. Faber Michael C. Cooper Darren Croton

We explore the behaviour of the blue galaxy fraction over the redshift range 0.75 ≤ z ≤ 1.3 in the DEEP2 Survey, both for field galaxies and for galaxies in groups. The primary aim is to determine the role that groups play in driving the evolution of galaxy colour at high z. In pursuing this aim, it is essential to define a galaxy sample that does not suffer from redshift-dependent selection effects in colour–magnitude space. We develop four such samples for this study: at all redshifts considered, each one is complete in colour–magnitude space, and the selection also accounts for evolution in the galaxy luminosity function. These samples will also be useful for future evolutionary studies in DEEP2. The colour segregation observed between local group and field samples is already in place at z ∼ 1: DEEP2 groups have a significantly lower blue fraction than the field. At fixed z, there is also a correlation between blue fraction and galaxy magnitude, such that brighter galaxies are more likely to be red, both in groups and in the field. In addition, there is a negative correlation between blue fraction and group richness. In terms of evolution, the blue fraction in groups and the field remains roughly constant from z = 0.75 to 1, but beyond this redshift the blue fraction in groups rises rapidly with z, and the group and field blue fractions become indistinguishable at z ∼ 1.3. Careful tests indicate that this effect does not arise from known systematic or selection effects. To further ensure the robustness of this result, we build on previous mock DEEP2 catalogues to develop mock catalogues that reproduce the colour–overdensity relation observed in DEEP2 and use these to test our methods. The convergence between the group and field blue fractions at z ∼ 1.3 implies that DEEP2 galaxy groups only became efficient at quenching star formation at z ∼ 2; this result is broadly consistent with other recent observations and with current models of galaxy evolution and hierarchical structure growth.

10.1111/j.1365-2966.2007.11374.x

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Citations (108)

Cold dark matter resuscitated?

Monthly Notices of the Royal Astronomical Society (1995)

Martin White D. Scott Joseph Silk Marc Davis

The Cold Dark Matter (CDM) model has an elegant simplicitly which makes it very predictive, but when its parameters are fixed at their `canonical' values its predictions are in conflict with observational data. There is, however, much leeway in the initial conditions within the CDM framework. We advocate a re-examination of the CDM model, taking into account modest variation of parameters from their canonical values. We find that CDM models with $n=0.8$--0.9 and $h=0.45$--0.50 can fit the available data. Our ``best fit'' CDM model has $n=0.9$, $h=0.45$ and $C_2^{T}/C_2^{S}=0.7$. We discuss the current state of observations which could definitely rule out this model.

Cold dark matter

10.1093/mnras/276.1.l69

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Dependence of galaxy quenching on halo mass and distance from its centre

Monthly Notices of the Royal Astronomical Society (2012)

Joanna Woo Avishai Dekel S. M. Faber K. G. Noeske David C. Koo

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 Mh, density over the nearest N neighbours deltaN, and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites quenching also depends on D. We present the M*-Mh relation for centrals at z~1. At z~1, the dependence of quenching on M* at fixed Mh is somewhat more pronounced 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 Mh, and not on M*. The Mh-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 deltaN 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.

Stellar mass

Virial mass

Ram pressure

Satellite galaxy

Mass fraction

10.1093/mnras/sts274

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Citations (190)

The DEEP2 Galaxy Redshift Survey: environments of post-starburst galaxies atz∼ 0.1 and ∼0.8

Monthly Notices of the Royal Astronomical Society (2009)

Renbin Yan Jeffrey A. Newman S. M. Faber Alison L. Coil Michael C. Cooper

Postststarburst (K+A) galaxies are candidates for galaxies in transition from a star-forming phase to a passively-evolving phase. We have spectroscopically identified large samples of K+A galaxies both in the SDSS at z~0.1 and in the DEEP2 survey at z~0.8, using a robust selection method based on a cut in Hbeta emission rather than the more problematic [OII] 3727. Based on measurements of the overdensity of galaxies around each object, we find that K+A galaxies brighter than 0.4L*_B at low-z have a similar, statistically indistinguishable environment distribution as blue galaxies, preferring underdense environments, but dramatically different from that of red galaxies. However, at higher-z, the environment distribution of K+A galaxies is more similar to red galaxies than to blue galaxies. We conclude that the quenching of star formation and the build-up of the red sequence through the K+A phase is happening in relatively overdense environments at z~1 but in relatively underdense environments at z~0. Although the relative environments where quenching occurs are decreasing with time, the corresponding absolute environment may have stayed the same along with the quenching mechanisms, because the mean absolute environments of all galaxies has to grow with time. In addition, we do not find any significant dependence on luminosity in the environment distribution of K+As. The existence of a large K+A population in the field at both redshifts indicates that cluster-specific mechanisms cannot be the dominant route by which these galaxies are formed. We also demonstrates that studying K+A-environment relations by measuring the K+A fraction in different environments is highly non-robust. Statistical comparisons of the overall environment distributions of different populations are much better behaved.

Peculiar galaxy

10.1111/j.1365-2966.2009.15192.x

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Citations (57)

Terrestrial catastrophism: Nemesis or galaxy?

Nature (1985)

Marc Davis Piet Hut Richard A. Muller

10.1038/313503a0

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Citations (8)