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We report results from a panoramic spectroscopic survey of 955 objects in thefield of the rich cluster Cl 0024+1654 (z~0.4), complementing the HST imagingpresented in the first paper in this series. Our new spectroscopic sampleincludes over 200 high quality spectra of cluster members, spread across anarea 10 Mpc in diameter. We examine the properties of a large sample of 104cluster early-types as a function of cluster radius and local density, usingthem as sensitive tracers of the various physical processes that may beresponsible for galaxy evolution. By constructing the Fundamental Plane of Cl0024, we infer an evolution in the mean mass to light ratio of early-typesequal to \Delta<Log (M/L_V)> = -0.14 +- 0.02. In the cluster center, we detecta significantly increased scatter in the relationship compared to that seen inlocal clusters. Moreover, we observe a clear radial trend in the mass to lightratios of individual early types, with the oldest galaxies located in thecluster core. Galaxies are apparently younger at larger radius, with E+S0s inthe periphery having M/L_V ratios that nearly match values seen in the field ata similar redshift. Independent spectral indicators used in combination revealan abrupt interaction with the cluster environment which occurs near the virialradius of Cl 0024, revealed by small bursts of star formation in a populationof dim early-types, as well as by enhanced Balmer absorption for a set oflarger E+S0s closer to the cluster core. We construct a simple infall modelused to compare the timescales and strengths of the observed interactions inthis cluster. We examine the possibility that bursts of star formation aretriggered when galaxies suffer shocks as they encounter the intra-clustermedium, or by the onset of galaxy harassment.Comment: 27 pages, 14 figures, Accepted by Ap

the astrophysical journal

A Wide‐Field<i>Hubble Space Telescope</i>Survey of the Cluster Cl 0024+16 at<i>z</i>= 0.4. III. Spectroscopic Signatures of Environmental Evolution in Early‐Type Galaxies

A Wide‐FieldHubble Space TelescopeSurvey of the Cluster Cl 0024+16 atz= 0.4. III. Spectroscopic Signatures of Environmental Evolution in Early‐Type Galaxies