2000A&A...355..891L -
Astronomy and Astrophysics, volume 355, 891-899 (2000/3-3)
A continuous low star formation rate in I Zw 18?
LEGRAND F., KUNTH D., ROY J.-R., MAS-HESSE J.M. and WALSH J.R.
Abstract (from CDS):
Deep long-slit spectroscopic observations of the blue compact galaxy I Zw 18 obtained with the CFH 3.6 m Telescope are presented. The very low value of oxygen abundance previously reported is confirmed and a very homogeneous abundance distribution is found (no variation larger than 0.05 dex) over the whole ionized region. We concur with Tenorio-Tagle (
1996AJ....111.1641T) and Devost et al. (
1997ApJ...482..765D) that the observed abundance level cannot result from the material ejected by the stars formed in the current burst, and propose that the observed metals were formed in a previous star formation episode. Metals ejected in the current burst of star formation remain most probably hidden in a hot phase and are undetectable using optical spectroscopy. We discuss different scenarios of star formation in I Zw 18. Combining various observational facts, for instance the faint star formation rate observed in low surface brightness galaxies (Van Zee et al. 1997c), it is proposed that a low and continuous rate of star formation occurring during quiescent phases between bursts could be a significant source of metal enrichment of the interstellar medium.
Abstract Copyright:
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Journal keyword(s):
galaxies: dwarf - galaxies: individual: I Zw 18 - galaxies: ISM
Simbad objects:
9
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