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The impact of metallicity and X-rays on star formation

Published online by Cambridge University Press:  27 April 2011

Marco Spaans ,
Aycin Aykutalp  and
Seyit Hocuk
Marco Spaans
Affiliation:
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, the Netherlands email: spaans@astro.rug.nl
Aycin Aykutalp
Affiliation:
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, the Netherlands email: spaans@astro.rug.nl
Seyit Hocuk
Affiliation:
Kapteyn Astronomical Institute, University of Groningen, P.O. Box 800, 9700 AV Groningen, the Netherlands email: spaans@astro.rug.nl
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Abstract

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Star formation is regulated through a variety of feedback processes. In this study, we treat feedback by metal injection and a UV background as well as by X-ray irradiation. Our aim is to investigate whether star formation is significantly affected when the ISM of a proto-galaxxy enjoys different metallicities and when a star forming cloud resides in the vicinity of a strong X-ray source. We perform cosmological Enzo simulations with a detailed treatment of non-zero metallicity chemistry and thermal balance. We also perform FLASH simulations with embedded Lagrangian sink particles of a collapsing molecular cloud near a massive, 107 M⊙, black hole that produces X-ray radiation.

We find that a multi-phase ISM forms for metallicites as small as 10−4 Solar at z = 6, with higher (10−2Z⊙) metallicities supporting a cold (<100 K) and dense (>103 cm−3) phase at higher (z = 20) redshift. A star formation recipe based on the presence of a cold dense phase leads to a self-regulating mode in the presence of supernova and radiation feedback. We also find that when there is strong X-ray feedback a collapsing cloud fragments into larger clumps whereby fewer but more massive protostellar cores are formed. This is a consequence of the higher Jeans mass in the warm (50 K, due to ionization heating) molecular gas. Accretion processes dominate the mass function and a near-flat, non-Salpeter IMF results.

Keywords

stars: formation — hydrodynamics — chemistry — IMF
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S270: Computational Star Formation , May 2010 , pp. 507 - 510
Copyright
Copyright © International Astronomical Union 2011

References

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