Slowly cooking galaxies

Abstract

Recent spectroscopic observations of IZw~18 have revealed homogeneous abundance throughout the galaxy and several observations of other starburst galaxies have shown no significant gradient or discontinuity in the abundance distributions within the HII regions. I thus concur with Tenorio-Tagle (1996) and Devost et al. (1997) that these observed abundance homogeneities cannot be produced by the material ejected from the stars formed in the current burst and result from 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. Combining various observational facts, for instance the faint star formation rate observed in low surface brightness galaxies (van Zee et al., 1997), I propose that a low and continuous star formation rate occurring during quiescent phases between bursts is a non negligible source of new elements in the interstellar medium. Using a spectrophotometric and chemical evolution model for galaxies, I investigated the star formation history IZw~18. I demonstrate that the continuous star formation scenario reproduces all the observed parameters of IZw~18. I discuss the consequences of such a quiet star formation regime.

Proceedings of the JENAM Conference (Toulouse, September 1999). To be published in New Astronomy Reviews, Editors Daniel Schaerer and Rosa Gonzalez Delgado. 8 pages, 3 figures

References in corpus (2)

• The Distribution Of Heavy Elements In Spiral And Elliptical Galaxies
• The Star Formation History of IZw18

Cited by in corpus (4)

• A Near-Infrared Stellar Census of Blue Compact Dwarf Galaxies: The Wolf-Rayet Galaxy I Zw 36
• Enrichment of the ISM by metal-rich droplets and the abundance bias in HII regions
• Spectrophotometric investigations of Blue Compact Dwarf Galaxies: Markarian 35
• Spatial distribution and evolution of the stellar populations and candidate star clusters in the Blue Compact Dwarf I Zwicky 18