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For refcode 1989MNRAS.237..461N:
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Copyright by Royal Astronomical Society. 1989MNRAS.237..461N On star formation in stellar systems - II. Photoionization in protodwarf galaxies A. Noriega-Crespo Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario, Canada P. Bodenheimer and D.N.C. Lin Lick Observatory, Board of Studies in Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA G. Tenorio-Tagle Max-Planck-Institut fur Astrophysik, D-8046 Garching bei Munchen, Federal Republic of Germany Accepted 1988 September 23. Received 1988 August 19; in original form 1988 June 17 Summary. The effects of the onset of star formation on the residual gas in a primordial low-mass Local-Group dwarf spheroidal galaxy, in the size range 0.3-l.0 kpc and in the mass range 1O^5^-10^7^ M_sun_, are investigated with a series of numerical hydrodynamical calculations. The main task is to determine the conditions under which the escape of residual gas, due to photo-ionization from an early generation of OB stars, can be prevented to allow an early epoch of self-enrichment in metals from supernova explosions in these systems. The main assumptions include: (i) a time-independent spherically symmetric gravitational potential from stars or dark matter; (ii) a low metal abundance in most cases; (iii) an initial mass function similar to that in the solar neighbourhood; (iv) an ionizing source located at the centre of the galaxy, and (v) a mass in the gaseous component which is a substantial fraction of the stellar and non-luminous mass. The dynamics are examined for the relevant ranges of mass in gas, stars and non-luminous matter, and of galactic radius. metallicity, ionizing flux and initial gas-density distribution. The results indicate that the effects of photo-ionization in the presence of a moderate gas-density gradient can easily eject the gas on a time-scale of a few times 10^7^ yr. However, with sufficiently high central gas density, combined with inefficient star formation, the effect of the ionizing flux may be localized to prevent mass ejection. In relatively diffuse systems, a flat initial density distribution may also be sufficient to suppress mass loss, even if the star-formation efficiency is relatively high. The addition of dark matter to the model galaxy has a similar effect to a reduction in the stellar ionizing flux. These results suggest that, given a normal initial mass function, many protodwarf galaxies may have been dispersed by the onset of star formation.
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