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Astron. Astrophys. 354, 874-880 (2000)


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The oxygen abundance deficiency in irregular galaxies

L.S. Pilyugin 1 and F. Ferrini *  2

1 Main Astronomical Observatory of National Academy of Sciences of Ukraine, Goloseevo, 03680 Kiev-127, Ukraine (pilyugin@mao.kiev.ua)
2 Department of Physics, Section of Astronomy, University of Pisa, Piazza Torricelli 2, 56100 Pisa, Italy (federico@astr2pi.difi.unipi.it)

Received 29 October 1999 / Accepted 13 December 1999

Abstract

The observed oxygen abundances in a number of irregular galaxies have been compared with predictions of the closed-box model of chemical and photometric evolution of galaxies. Oxygen is found to be deficient with respect to the predicted abundances. This is an indicator in favor of loss of heavy elements via galactic winds or/and of infall of low-abundance gas onto the galaxy.

The oxygen abundance deficiency observed within the optical edge of a galaxy cannot be explained by mixing with the gas envelope observed outside the optical limit. We confirm the widespread idea that a significant part of the heavy elements is ejected by irregular galaxies in the intergalactic medium.

Key words: galaxies: abundances – galaxies: evolution – galaxies: ISM – galaxies: irregular

* Present address: INTAS, 58 Avenue des Arts, 1000 Bruxelles, Belgium

Send offprint requests to: L.S. Pilyugin

© European Southern Observatory (ESO) 2000

Online publication: February 25, 2000

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