Description
Using a magnitude-limited, spectroscopic survey of the X-ray-luminous galaxy cluster MS 1054-03, we isolate 153 cluster galaxies and measure MS 1054's redshift and velocity dispersion to be z=0.8307+/-0.0004 and {sigma}_z_=1156+/-82km/s. The absorption-line, post-starburst ("E+A"), and emission-line galaxies, respectively, make up 63%+/-7%, 15%+/-4%, and 23%+/-4% of the cluster population. With photometry from HST ACS, we find that the absorption-line members define an exceptionally tight red sequence over a span of ~3.5mag in i775: their intrinsic scatter in (V606-i775) color is only 0.048+/-0.008, corresponding to a (U-B)z scatter of 0.041.
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