Keck/LRIS Spectroscopy of the Distant Cluster Cl\,0016+16

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Session 53 -- Clusters of Galaxies I
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[53.08] Keck/LRIS Spectroscopy of the Distant Cluster Cl\,0016+16

Gregory D. Wirth (UC Santa Cruz), David C. Koo (UCO/Lick)

The rich galaxy cluster Cl\,0016+16 at $z=0.55$ initially achieved visibility (Koo 1981) for being the original ``anti Butcher-Oemler effect'' cluster: its galaxy population was found to be almost entirely red, indistinguishable in rest-frame color from local E/S0 galaxies, despite the expectation that higher redshift clusters should have a greater proportion of blue galaxies (Butcher \& Oemler 1978, 1984). Interest in this cluster has heightened over the last decade as: \begin{itemize} \item X-ray observations found it to be among the most luminous clusters known (Henry et al. 1992); \item radio observations showed it to be among only a handful of clusters exhibiting a Sunyaev-Zel'dovich microwave decrement, useful for measuring the Hubble Constant (Lasenby 1992); \item optical spectroscopy revealed a significant population of ``E+A'' galaxies, enigmatic objects with spectra suggesting a recently-concluded episode of star formation (Dressler \& Gunn 1992). \end{itemize} Further observations by ROSAT, ASCA, and HST have established Cl\,0016+16 as among the best-studied clusters beyond Coma.

The red nature of its galaxy population makes Cl\,0016+16 a prime candidate for the study of cluster galaxy evolution. As part of an ongoing effort to study the early-type galaxies in this cluster, we recently used the Keck Telescope and Low-Resolution Imaging Spectrograph to obtain high quality spectra of 19 cluster members at 6\AA\ (FWHM) resolution. This poster describes the preliminary results from these data, which will allow us to investigate galaxy age and metallicity at lookback times nearly halfway to the Big Bang, probe the internal kinematics of galaxies at $z=0.55$, and thus perhaps trace the evolution of the ``fundamental plane'' for E/S0 galaxies.

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