AAS 207th Meeting, 8-12 January 2006
Session 69 Stellar Evolution
Poster, Tuesday, 9:20am-6:30pm, January 10, 2006, Exhibit Hall

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[69.09] Horizontal Branch Stars in the Canis Major Dwarf Galaxy

A. Westfall, R. Wilhelm, W. L. Powell (Texas Tech University)

In 2003, the Canis Major Dwarf was discovered and found to be the closest satellite galaxy to our Milky Way. The object of this investigation is to explore the chemical and kinematic properties of the Canis Major Dwarf. To accomplish this we selected a a candidate population of horizontal branch stars in the direction of Canis Major, and analyzed their properties. We selected hot star candidates from several photometry fields taken on the 0.8 meter telescope at McDonald Observatory with a B-V color value of less than 0.4 and a V magnitude of 15 to 17, which corresponds to the correct distance for horizontal branch stars located in the galaxy. We observed a small selection of these candidates (N = 15) on a follow-up spectroscopy run on the 2.7 meter telescope at McDonald Observatory. After extracting, normalizing, and calculating the Doppler shift of our spectral data, we found the mean heliocentric radial velocity of our sample to be ~57 km/s, and ~35% of the candidates have a velocity of 59 +- 6 km/s, indicating a population of uniform velocity. This velocity is significantly different then the published mean velocity from surveys of M-giants, suggesting the old population of the Canis Major Dwarf has a phase space distribution different then the young population. We will be presenting these results along with an analysis of the density of the old population as a function of distance from the galaxy's center.

R.W. acknowledges partial support for this research from an AAS Small Research Grant.

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