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Session 103 - Galaxy Evolution.
Display session, Thursday, January 16
The Fundamental Plane (FP), \log r_e =1.24 \log \sigma - 0.82 \log <\!I\!>_e + \gamma, has been established for E and S0 galaxies in the rich clusters Abell 665 and Abell 2218, based on photometry corrected to the R-band in the clusters' rest frames. Both clusters have a redshift of 0.18. The FPs for the two clusters are consistent with the slope and scatter of the FP for galaxies in nearby rich clusters. The low scatter of the FP makes it possible to measure the luminosity evolution with an accuracy of \approx 0.05 mag based on 6 to 10 galaxies observed in one cluster. Thus, the luminosity evolution may be detected for relatively small differences in the redshifts. Our results are based on 7 galaxies in A665 and 8 galaxies in A2218. A665 and A2218 have a luminosity evolution of 0.25 mag and 0.13 mag, respectively. Together with previous results for the FP for one cluster at z=0.4 and literature results for several clusters based on the Kormendy relation (\log r_e = a \log <\!I\!>_e +b) we can now study the luminosity evolution of cluster E and S0 galaxies between z=0.5 and the present. We find an average luminosity evolution of \approx 0.6 mag over this range in redshift. For a passive luminosity evolution this is consistent with a formation redshift of the galaxies of four or larger.
Program listing for Thursday