NOAO >   Observing Info >   Approved Programs >   2002B-0392

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Proposal Information for 2002B-0392


PI: Maritza Tavarez, University of Michigan, tavarez@astro.lsa.umich.edu
Address: P. O. Box 1090, Ann Arbor, MI 48109, USA

CoI: Mario Mateo, University of Michigan

Title: Dwarf Galaxies as probes of Dark Matter Halos

Abstract: With the advent of detailed simulations of galaxy formation cold dark matter (CDM) predicts that galaxy-sized DM halos have steep central density cusps, i.e. NFW profiles (Navarro, Frenk & White 1996, 1997). However, a wide range of observations show that real DM halos associated with LSB and dwarf Irregular (dIrr) galaxies do not exhibit such steep density profiles. Many of these galaxies appear to have nearly constant density cores at the centers of their halos or else they exhibit shallow central density cusps. Others contend that observational uncertainties, i.e. beam smearing, from HI data can produce these effects. Thus better quality, higher-resolution kinematic data is crucial to constrain the central density profiles of DM halos. Our goal is to make a significant observational contribution by analyzing the DM halo properties of a carefully selected sample of ~ 20 nearby, late-type galaxies. These systems have been chosen to minimize problems with inclination, tidal effects (all are isolated), and achievable spatial resolution. Our work so far on this sample has involved obtaining deep, multi-band surface photometry, HI 21cm synthesis data (some new and much archival), and - most relevant to this proposal - new long-slit H(alpha) spectroscopy to derive the DM halo properties down to the centers of these galaxies. A minority of the galaxies in our sample have only faint diffuse H(alpha) emission in their cores. Since our attempts to observe these at MDM have failed to produce useable kinematic data, we propose to use the KPNO 4m + RC Spectrograph to obtain H(alpha) spectroscopy of the faintest galaxies in our sample.


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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