We present an optically selected catalog of 1073 galaxy cluster and group candidates at 0.3 [ z [ 1. These candidates are drawn from the Las Campanas Distant Clusters Survey (LCDCS), a drift-scan imaging survey of a 130 square degree strip of the southern sky. To construct this catalog we utilize a novel detection process in which clusters are detected as positive surface brightness Ñuctuations in the background sky. This approach permits us to Ðnd clusters with signiÐcantly shallower data than other matched-Ðlter methods that are based upon number counts of resolved galaxies. Selection criteria for the survey are fully automated so that this sample constitutes a well-deÐned, homogeneous sample that can be used to address issues of cluster evolution and cosmology. Estimated redshifts are derived for the entire sample, and an observed correlation between surface brightness and velocity dispersion, p, is used to estimate the limiting velocity dispersion of the survey as a function of redshift. We Ðnd a net surface density of 15.5 candidates per square degree at with a false-detection rate of D30%. At z D 0.3 z est º 0.3, we probe down to the level of poor groups while by z D 0.8 we detect only the most massive systems km s~1). We also present a supplemental catalog of 112 candidates that fail one or more of (p Z 1000 the automated selection criteria, but appear from visual inspection to be bona Ðde clusters.

We measure the luminosity profiles of 16 brightest cluster galaxies (BCGs) at 0.4 < z < 0.8 using high resolution F160W NICMOS and F814W WFPC2 HST imaging. The heterogeneous sample is drawn from a variety of surveys: seven from clusters in the Einstein Medium Sensitivity Survey (EMSS; Gioia & Luppino 1994), five from the Las Campanas Distant Cluster Survey and its northern hemisphere precursor (LCDCS; Dalcanton et al. 1997;Gonzalez et al. 2001;Nelson et al. 2001a), and the remaining four from traditional optical surveys (Spinrad 1980;Koo 1981;Gunn et al. 1986;Couch et al. 1991). We find that the surface brightness profiles of all but three of these BCGs are well described by a standard de Vaucouleurs (r 1/4 ) profile out to at least ∼ 2r e and that the biweight-estimated NICMOS effective radius of our high redshift BCGs (r e = 8.3 ± 1.4 kpc for H 0 = 80 km s −1 Mpc −1 , Ω m = 0.2, Ω Λ = 0.0) is ∼ 2 times smaller than that measured for a local BCG sample (Graham et al. 1996). If high redshift BCGs are in dynamical equilibrium and satisfy the same scaling relations as low redshift ones, this change in size would correspond to a mass growth of a factor of 2 since z ∼ 0.5. However, the biweight-estimated WFPC2 effective radius of our sample is 18 ± 5.1 kpc, which is fully consistent with the local sample. While we can rule out mass accretion rates higher than a factor of 2 in our sample, the discrepancy between our NICMOS and WFPC2 results, which after various tests we describe appears to be physical, does not yet allow us to place strong constraints on accretion rates below that level.

We analyze photometry and spectroscopy of a sample of 63 clusters at 0.3 ¹ z ¹ 0.9 drawn from the Las Campanas Distant Cluster Survey to empirically constrain models of cluster galaxy evolution. SpeciÐcally, (1) by combining I-band photometry of 44 of our clusters with that of 19 clusters from the literature, we parameterize the redshift dependence of in the observed frame as We suggest that M I * these observations can be explained with a model in which luminous early-type galaxies (or more precisely, the progenitors of current-day luminous early-type galaxies) form the bulk of their stellar populations at high redshifts and in which many of these galaxies, if not all, accrete mass either in the (Z5) form of evolved stellar populations or gas that causes only a short-term episode of star formation at lower redshifts (1.5 \ z \ 2). Our data are too crude to reach conclusions regarding the evolutionary state of any particular cluster or to investigate whether the morphological evolution of galaxies matches the simple scenario that we discuss, but the statistical nature of this study suggests that the observed evolutionary trends are universal in massive clusters.

We present the first high redshift (0.3 < z < 1.1) galaxy clusters found by systematically identifying optical low surface brightness fluctuations in the background sky. Using spectra obtained with the Keck telescope and I-band images from the Palomar 1.5m telescope, we conclude that at least eight of the ten candidates examined are high redshift galaxy clusters. The identification of such clusters from low surface brightness fluctuations provides a complementary alternative to classic selection methods based on overdensities of resolved galaxies, and enables us to search efficiently for rich high redshift clusters over large areas of the sky. The detections described here are the first in a survey that covers a total of nearly 140 sq. degrees of the sky and should yield, if these preliminary results are representative, over 300 such clusters.

We measure the extent of 100 micron galactic emission in two independent galaxy samples using the IRAS 100 micron Sky Survey images and constrain the distribution of dust at large ($\ltsim$30 kpc) radii. The first sample consists of 90 nearby (v < 6000 km/s) galaxies from the RC3 catalog with similar angular sizes and absolute luminosities (5 arcmin $\leq $D$_{25} \leq$ 10 arcmin and $-22.5 \leq $M$_{B} \leq -18$) that are isolated in the 100 micron images. The second sample consists of 24 local galaxies (v < 1500 km/s, 10 arcmin $\leq $D$_{25} \leq$ 30 arcmin). We rescale the 100 micron images of these galaxies using their optical diameters, D$_{25}$, rotate the images using their optical major axis position angle, construct the mean and median image, and rebin the final images into polar coordinates to study the 100 micron emission as a function of radius and azimuthal angle. We find that the 100 micron emission extends at least to radii of 27 kpc (2$\sigma$ detection) for the typical galaxy in the 5 arcmin - 10 arcmin sample and to 21 kpc (2$\sigma$ detection) in the 10 arcmin - 30 arcmin sample (H$_{0} = $75 km/s/Mpc). In both samples, the emission is preferentially elongated along the optical major axis. We fit an exponential to the 100 micron emission along the major axis and measure a scale length of $2.5 \pm$ 0.8 kpc (90% confidence interval). Using a simple model that relates the far-IR emission to the stellar distribution, we examine the range of acceptable dust mass distributions allowed by our data and conclude that the dust is more extended than the starlight.Comment: 31 pages, 9 figures, AASTEX (aaspp4), accepted for publication in the Astronomical Journa