Distribution to the Astronomy Community of the Compressed Digitized Sky Survey

The Space Telescope Science Institute has compressed an all-sky collection of ground-based images and has printed the data on a two volume, 102 CD-ROM disc set. The first part of the survey (containing images of the southern sky) was published in May 1994. The second volume (containing images of the northern sky) was published in January 1995. Software which manages the image retrieval is included with each volume. The Astronomical Society of the Pacific (ASP) is handling the distribution of the lOx compressed data and has sold 310 sets as of October 1996. ASP is also handling the distribution of the recently published 100x version of the northern sky survey which is publicly available at a low cost. The target markets for the 100x compressed data set are the amateur astronomy community, educational institutions, and the general public. During the next year, we plan to publish the first version of a photometric calibration database which will allow users of the compressed sky survey to determine the brightness of stars in the images

ATLAST: Advanced Technology Large-Aperture Space Telescope

The technologies needed to build an affordable larger Ultraviolet/Optical Space Telescope are presented

An 8 Meter Monolithic UV/Optical Space Telescope

The planned Ares V launch vehicle with its 10 meter fairing and at least 55,600 kg capacity to Earth Sun L2 enables entirely new classes of space telescopes. A consortium from NASA, Space Telescope Science Institute, and aerospace industry are studying an 8-meter monolithic primary mirror UV/optical/NIR space telescope to enable new astrophysical research that is not feasible with existing or near-term missions, either space or ground. This paper briefly reviews the science case for such a mission and presents the results of an on-going technical feasibility study, including: optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; launch vehicle performance and trajectory; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; operations & servicing; mass budget and cost

Brightest Cluster Galaxies at the Present Epoch

We have observed 433 z<=0.08 brightest cluster galaxies (BCGs) in a full-sky survey of Abell clusters. The BCG Hubble diagram is consistent to within 2% of a Omega_m=0.3, Lambda=0.7 Hubble relation. The L_m-alpha relation for BCGs, which uses alpha, the log-slope of the BCG photometric curve of growth, to predict metric luminosity, L_m, has 0.27 mag residuals. We measure central stellar velocity dispersions, sigma, of the BCGs, finding the Faber-Jackson relation to flatten as the metric aperture grows to include an increasing fraction of the total BCG luminosity. A 3-parameter "metric plane" relation using alpha and sigma together gives the best prediction of L_m, with 0.21 mag residuals. The projected spatial offset, r_x, of BCGs from the X-ray-defined cluster center is a gamma=-2.33 power-law over 1<r_x<10^3 kpc. The median offset is ~10 kpc, but ~15% of the BCGs have r_x>100 kpc. The absolute cluster-dispersion normalized BCG peculiar velocity |Delta V_1|/sigma_c follows an exponential distribution with scale length 0.39+/-0.03. Both L_m and alpha increase with sigma_c. The alpha parameter is further moderated by both the spatial and velocity offset from the cluster center, with larger alpha correlated with the proximity of the BCG to the cluster mean velocity or potential center. At the same time, position in the cluster has little effect on L_m. The luminosity difference between the BCG and second-ranked galaxy, M2, increases as the peculiar velocity of the BCG within the cluster decreases. Further, when M2 is a close luminosity "rival" of the BCG, the galaxy that is closest to either the velocity or X-ray center of the cluster is most likely to have the larger alpha. We conclude that the inner portions of the BCGs are formed outside the cluster, but interactions in the heart of the galaxy cluster grow and extend the envelopes of the BCGs.Comment: Accepted for publication in the Astrophysical Journa

Discovery of a new fundamental plane dictating galaxy cluster evolution from gravitational lensing

In cold dark matter (CDM) cosmology, objects in the Universe have grown under the effect of gravity of dark matter. The intracluster gas in a galaxy cluster was heated when the dark-matter halo formed through gravitational collapse. The potential energy of the gas was converted to thermal energy through this process. However, this process and the thermodynamic history of the gas have not been clearly characterized in connection with with the formation and evolution of the internal structure of dark-matter halos. Here, we show that observational CLASH data of high-mass galaxy clusters lie on a plane in the three-dimensional logarithmic space of their characteristic radius $r_s$, mass $M_s$, and X-ray temperature $T_X$ with a very small orthogonal scatter. The tight correlation indicates that the gas temperature was determined at a specific cluster formation time, which is encoded in $r_s$ and $M_s$. The plane is tilted with respect to $T_X \propto M_s/r_s$, which is the plane expected in case of simplified virial equilibrium. We show that this tilt can be explained by a similarity solution, which indicates that clusters are not isolated but continuously growing through matter accretion from their outer environments. Numerical simulations reproduce the observed plane and its angle. This result holds independently of the gas physics implemented in the code, revealing the fundamental origin of this plane.Comment: Replaced with a revised version to match the ApJ accepted versio