Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-06-22
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Proceedings IAU Symposium No. 270, 2010. 4 pages, 5 figures
Scientific paper
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, 10^{7} M\odot, 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^{-2}Z\odot) metallicities supporting a cold (< 100 K) and dense (> 10^{3} 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.
Aykutalp Aycin
Hocuk Seyit
Spaans Marco
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