http://hdl.handle.net/1803/684 2013-05-20T00:33:09Z http://hdl.handle.net/1803/5192 Title: Simulating the universe with GPU-accelerated supercomputers: n-body methods, tests, and examples Authors: Wibking, Benjamin Abstract: We demonstrate the acceleration obtained from using GPU/CPU hybrid clusters and supercomputers for N-body simulations of gravity based in part on the author's new code development.  Validation tests are shown for cosmological simulations and for galaxy simulations, along with their respective speedups compared to traditional simulations.  Potential new applications for science enabled by this advance are highlighted. 2013-04-22T05:00:00Z http://hdl.handle.net/1803/5108 Title: Rotation periods of the Hyades open cluster using ASAS light curves : measuring the Hyades gyro-age and benchmarking tools for gyrochronology studies with LSST Authors: Kundert, Alisha Abstract: Rotation period distributions for older open clusters are difficult to obtain because of the general scarcity of clusters with ages greater than 200 Myr, as well as the challenge of measuring rotation periods for less active older stars. This has clouded our knowledge of how stars spin down as they evolve from the zero-age main sequence. A key piece of our understanding of how stellar rotation rates change over time relies on the study of the nearby (~45 pc) and old (~625 Myr) Hyades open cluster. We present the results from a detailed analysis of the rotation period distribution of the Hyades in an effort to estimate the gyro-age of this benchmark open cluster. Analyzing All Sky Automated Survey (ASAS) light curves with 14+ year baselines, we measure rotation periods for Hyades members by applying a period-finding technique that combines the Lomb-Scargle periodogram and Monte Carlo simulations to optimize period detection in long-baseline, low-cadence light curves that potentially suffer from time-dependent changes, e.g. star spot evolution. We derive 67 rotation periods for Hyades members, 40 of which are determined for the first time. These rotation periods measured from ASAS light curves allow us to characterize the rotation period distribution of the Hyades, enabling the application of current gyrochronology models to calculate a rotation-age for the cluster. Additionally, using ASAS data provides a valuable test of our ability to determine rotation periods in future low-cadence, extended duration surveys, such as the Large Synoptic Survey Telescope (LSST). 2012-04-01T05:00:00Z http://hdl.handle.net/1803/4108 Title: Density profiles of dark matter halos Authors: Robbins, Katherine Description: Highest Honors in Astronomy 2010-04-01T05:00:00Z http://hdl.handle.net/1803/2982 Title: Number density profiles of galaxy groups and clusters in the SDSS Authors: Norris, Jackson M. Abstract: We use projected number density profiles of galaxy groups to investigate the relationship between galaxy group structure and dark matter structure within halos. We primarily study a specific model of how galaxies populate dark matter halos by comparing the number density profiles of galaxy groups from the Sloan Digital Sky Survey with number density profiles of galaxy groups taken from dark matter halo simulations. We also investigate the dependence of galaxy locations within galaxy groups on luminosity and color. Description: Highest Honors in Astronomy 2008-04-20T05:00:00Z