Spectroscopic signatures of galaxy evolution in Cl0024+16 at $z\sim 0.4$
Sean M. Moran a1, Richard S. Ellis a1andTommaso Treu a2 a1 California Institute of Technology, Department of Astronomy, Mail Code 105-24, Pasadena, CA 91125, USA email: [email protected], [email protected] a2 University of California at Los Angeles, Department of Physics & Astronomy, Los Angeles, CA 90095, USA email: [email protected]
We report the first results from a panoramic spectroscopic survey of galaxies in the rich cluster Cl0024+1654 ($z\simeq 0.4$). Using HST imaging we examine the properties of early-types as a function of cluster radius. At all cluster radii, our sample lies on a self-consistent Fundamental Plane whose zero point implies evolution since $z=0$ corresponding to $\Delta[\log (M/L_V)] = 0.14 \pm 0.06$, an overall trend consistent with previous work. Using diagnostic [O II] emission and Balmer absorption lines, we locate a population of intrinsically faint galaxies at 1–2.4 Mpc radius undergoing a period of star formation. The luminosity-dependent radial trends are suggestive of the gradual quenching of star formation for infalling galaxies. We discuss physical mechanisms that may be responsible for this environmental evolution.