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HI selected galaxies in the Sloan Digital Sky Survey
We present the results from a study of HI selected galaxies that fall within both the HI Parkes All Sky Survey (HIPASS) and the Sloan Digital Sky Survey (SDSS). By comparing the optical properties derived from the SDSS five-band photometry with the HI properties from HIPASS, we are able to probe the relationship between the ...
The assembly of cluster galaxies
Clusters of galaxies are the largest bound structures in the universe. As such, they represent an important tool for testing models of structure formation. In addition, because galaxies in clusters span a range of local environments and experience the full spectrum of galaxy evolution pathways, clusters are ideal targets for ...
What's happening around Herbig Ae stars?: investigating circumstellar activity in young intermediate mass stars with optical and near-infrared spectroscopy
We have investigated the optical and near-infrared spectral behavior of the intermediate mass, pre-main sequence Herbig Ae stars, with particular emphasis on variability and evolution. The evolutionary state of Herbig Ae (HAe) stars is intermediate between very young, pre-main sequence objects and the young main sequence Vega, ...
Candidate isolated neutron stars and other stellar x-ray sources from the ROSAT all-sky and Sloan Digital Sky Surveys
Although extra-solar X-ray sources were first observed almost fifty years ago, the first all-sky imaging X-ray survey was only recently completed. The ROSAT All-Sky Survey (RASS) Bright and Faint Source Catalogs include approximately 124,000 X-ray sources detected in the 0.1--2.4 keV range. However, while X-ray source ...
A hyperbolic tetrad approach to numerical relativity
An in-depth numerical study using 3 + 1 formulations of the Einstein equations for 1D colliding plane waves reveals factors which increase accuracy and stability: using "mixed" variables, hyperbolicity, satisfying the energy and momentum constraint equations at the boundaries, and changing the speeds of "constraint" eigenmodes ...