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Proposal Information for 2004A-0436


PI: Sheila Kannappan, The University of Texas at Austin, sheila@astro.as.utexas.edu
Address: McDonald Observatory, 1 University Station C1402, Austin, TX 78712-0259, USA

CoI: Chris Impey, University of Arizona

Title: Faint Companions and LSB Extensions of S0 Galaxies: Clues to Thick and Thin Disk Formation

Abstract: We request KPNO/CTIO 4-meter time to complete our deep MOSAIC imaging survey ((mu)_\rm V=27) of the extended disk structures and environments of S0 galaxies. As a heterogeneous population shaped to varying degrees by galaxy encounters, cluster influences, and secular evolution, S0's are ideal for studying the interplay of internally and externally driven processes in disk formation. Our sample is broadly representative of the S0 population over a wide range of luminosities and environments. Comparably sensitive data have not been available for such a sample: the proposed data will allow us to detect companions as faint as Local Group dwarf spheroidals as well as extended LSB structures as faint as the disk of Malin 1. We will evaluate the frequency of LSB extensions to S0 disks, which may indicate thin-disk regrowth. With extensive supporting data from previous surveys, the final data set will allow us to correlate disk properties (e.g., scale lengths and heights for separate disk components, truncation radii, v/\sigma ratios, and star formation rates) against indicators of different disk formation mechanisms (e.g., companion distances and sizes, global environmental densities, faint tidal features, and disk gas metallicities), to evaluate the respective roles of secular and externally driven evolution in S0 disk formation. Due to unusually poor weather, our previous MOSAIC runs have yielded deep imaging for only 6.5 of our original targets. We have access to comparably deep imaging and environmental density information for another ~10+ S0's by collaboration with the NOAO Deep Wide-Field Survey team. To round out a 35+ galaxy sample spanning a wide range of luminosities and local and global environments, we request 4 nights in 2004A and 2 in 2004B.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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