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2010MNRAS.406.1238E - Mon. Not. R. Astron. Soc., 406, 1238-1247 (2010/August-1)
When are extremely metal-deficient galaxies extremely metal deficient ?
EKTA B. and CHENGALUR J.N.
Abstract (from CDS):
We also determine the gas mass fractions and chemical yields of galaxies in all three samples. We find that the effective chemical yield increases with increasing baryonic mass, consistent with what is expected if outflows of metal-enriched gas are important in determining the effective yield. XMD galaxies have lower effective yield than BCG/dI galaxies of similar baryonic mass. This suggests that some process, peculiar to XMD galaxies, has resulted in their low measured metallicities. Motivated by the fact that interactions are common in XMD galaxies, we suggest that improved (tidally driven) mixing of the interstellar media (ISM) in XMD galaxies leads to a lowering of both, the measured metallicity and the calculated effective yield. In isolated dwarf galaxies, the outer parts of the stellar envelope probably do not participate in the star formation, but are still generally included in the calculation of effective yield. This results in an overestimate of the effective yield. We suggest that XMD galaxies are deviant from the L-Z relation because of a combination of being gas rich (i.e. having processed less gas into stars) and having more uniform mixing of metals in their ISM.
Abstract Copyright: © 2010 The Authors. Journal compilation © 2010 RAS
Journal keyword(s): galaxies: abundances - galaxies: dwarf - galaxies: evolution
Simbad objects: 122
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