Augustus Oemler

The Star formation histories of galaxies in distant clusters

We present a detailed analysis of the spectroscopic catalog of galaxies in 10 distant clusters from Dressler et al. We investigate the nature of the different spectral classes defined by Dressler et al., including star-forming, poststarburst, and passive galaxy populations, and reproduce their basic properties using our spectral synthesis model. We attempt to identify the evolutionary pathways between the various spectral classes in order to search for the progenitors of the numerous poststarburst galaxies. The comparison of the spectra of the distant galaxy populations with samples drawn from the local universe leads us to identify a significant population of dust-enshrouded starburst galaxies, showing both strong Balmer absorption and relatively modest [O II] emission, that we believe are the most likely progenitors of the poststarburst population. We present the differences between the field and cluster galaxies at z=0.4-0.5. We then compare the spectral and morphological properties of the distant cluster galaxies, exploring the connection between the quenching of star formation inferred from the spectra and the strong evolution of the S0 population discussed by Dressler et al. We conclude that either two different timescales and/or two different physical processes are responsible for the spectral and morphological transformation.

The Las Campanas Redshift Survey

The Las Campanas Redshift Survey (LCRS) consists of 26418 redshifts of galaxies selected from a CCD-based catalog obtained in the

The Homogeneity of Spheroidal Populations in Distant Clusters

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A Spectroscopic Catalog of 10 Distant Rich Clusters of Galaxies

band. The survey covers over 700 square degrees in 6 strips, each 1.5

A Wide-Field Hubble Space Telescope Study of the Cluster Cl 0024+16 at z = 0.4. I. Morphological Distributions to 5 Mpc Radius

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MORPHOLOGICAL COMPOSITION OF z ∼ 0.4 GROUPS: THE SITE OF S0 FORMATION

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A Catalog of morphological types in 10 distant rich clusters of galaxies

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A Comparison of Direct and Indirect Mass Estimates for Distant Clusters of Galaxies

, three each in the North and South galactic caps. The median redshift in the survey is about 30000 km~s

Afterglows, redshifts, and properties of Swift gamma-ray bursts

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The Dawn of the Red: Star formation histories of group galaxies over the past 5 billion years

. Essential features of the galaxy selection and redshift measurement methods are described and tabulated here. These details are important for subsequent analysis of the LCRS data. Two dimensional representations of the redshift distributions reveal many repetitions of voids, on the scale of about 5000 km~s