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We determined the K band luminosity function (LF) of cluster galaxies at redshift z~1.2, using near-infrared images of three X-ray luminous clusters at z=1.11,1.24,1.27. The composite LF was derived down to M*+4, by means of statistical background subtraction, and is well described by a Schechter function with K*=20.5 AB mag and alpha=-1. From the K band composite LF we derived the stellar mass function of cluster galaxies. Using available X-ray mass profiles we determined the M/L ratios of these three clusters, which tend to be lower than those measured in the local universe. With these data, no significant difference can be seen between the shapes of the cluster galaxies LF and the LF of field galaxies at similar redshift. We also found no significant evolution out to z ~1.2 in the bright (2. The results obtained in this work support and extend previous findings that most of the stars in bright galaxies were formed at high redshift, and that K-bright (M>10^11 Msun) galaxies were already in place at z ~ 1.2, at least in the central regions of X-ray luminous clusters. Together with recent results on the field galaxies stellar mass function, this implies that most of the stellar mass is already assembled in massive galaxies by z ~ 1, both in low and high density environments., Comment: 16 pages, 10 figures, to appear in A&A

We analyze the ROSAT Deep Cluster Survey (RDCS) to derive cosmological constraints from the evolution of the cluster X-ray luminosity distribution. The sample contains 103 galaxy clusters out to z=0.85 and flux-limit Flim=3 10^{-14} cgs (RDCS-3) in the [0.5-2.0] keV energy band, with a high-z extension containing four clusters at 0.901 10^{-14} cgs (RDCS-1). Model predictions for the cluster mass function are converted into the X-ray luminosity function in two steps. First we convert mass into intra-cluster gas temperature by assuming hydrostatic equilibrium. Then temperature is converted into X-ray luminosity by using the most recent data on the Lx-T relation for nearby and distant clusters. These include the Chandra data for seven distant clusters at 0.57

Starlight from distant galaxies ($z > 3$) is redshifted into the near infrared band with observed wavelengths from 2-8 $\mu$m. Most of the light is emitted by stars that have a peak emission at the 1.6 $\mu$m wavelength of the minimum of the H$^-$ opacity. We present simulated images of galaxy and star fields at 3, 4.7 and 8 $\mu$m, using the expected performance of the infrared camera on the Space InfraRed Telescope Facility (SIRTF). Standard astronomical image processing tools are used to locate sources, distinguish stars from galaxies, and create color-magnitude and color-color diagrams for the galaxies., Comment: poster paper presented at the June 1994 AAS meeting, 3 pages LaTex using aaspp.sty with appended color Postscript, GIF and JPEG figures, (330 kbytes) UCLA-ASTRO-ELW-94-03