AAS 200th meeting, Albuquerque, NM, June 2002
Session 27. Properties and Evolution of Galaxies
Oral, Monday, June 3, 2002, 2:00-3:30pm, Ruidoso/Pecos

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[27.03] The Luminosity-Metallicity Relation, Effective Yields, and Metal Loss in Galaxies

D. Garnett (Steward Observatory)

I present results on the correlation between galaxy mass, luminosity, and metallicity for a sample of spiral and irregular galaxies having well-measured abundance profiles, distances, and rotation speeds. These data are combined to study the metallicity-luminosity and metallicity-rotation speed correlations for spiral and irregular galaxies.

The metallicity luminosity correlation shows its familiar form for these galaxies, a roughly uniform change in the average present-day O/H abundance of about a factor 100 over 11 magnitudes in B luminosity. However, the O/H - V(rot) relation shows a change in slope at a rotation speed of about 125 km/sec. At faster V(rot), there appears to be no relation between average metallicity and rotation speed. At lower V(rot), the metallicity correlates with rotation speed. This change in behavior could be the result of increasing loss of metals from the smaller galaxies in supernova-driven winds. This idea is tested by looking at the variation in effective yield, derived from observed abundances and gas fractions assuming closed box chemical evolution. The effective yields derived for spiral and irregular galaxies increase by a factor of 30 from V(rot) approx. 10 km/sec to V(rot) approx. 300 km/sec, asymptotically approaching a constant value for V(rot) > 150 km/sec. The trend suggests that galaxies with V(rot) < 150 km/sec can lose a large fraction of their SN ejecta in galactic winds, while galaxies above this value tend to retain metals.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.