Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-06-02
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
10 pages, 1 table, 5 figures; in press. Minor changes done
Scientific paper
Star formation remains an unsolved problem in astrophysics. Numerical studies of large-scale structure simulations cannot resolve the whole process and their approach usually assumes that only gas denser than a typical threshold can host and form stars. We investigate the onset of cosmological star formation and compare several very-high-resolution, three-dimensional, N-body/SPH simulations that include non-equilibrium, atomic and molecular chemistry, star formation prescriptions, and feedback effects. We study how primordial star formation depends on gas density thresholds, cosmological parameters and initial set-ups. For mean-density initial conditions, we find that standard low-density star-formation threshold (0.2 h^2/cm3) models predict the onset of star formation at z~25-31, depending on the adopted cosmology. In these models stars are formed regardless of the time between the moment when the threshold is reached and the effective runaway collapse. At high redshift, this time interval represents a significant fraction of the Hubble time and thus this assumption can induce large artificial off-sets to the onset of star formation. Choosing higher density thresholds (135 h^2/cm3) allows the entire cooling process to be followed, and the onset of star formation is then estimated to be at redshift z~12-16. When isolated, rare, high-density peaks are considered, the chemical evolution is much faster and the first star formation episodes occur at z > 40, almost regardless of the choice for the density threshold. These results could have implications for the formation redshift of the first cosmological objects, as inferred from direct numerical simulations of mean-density environments, and on the studies of the reionization history of the universe.
Ciardi Benedetta
Dolag Klaus
Maio Umberto
Tornatore Luca
Yoshida Naoki
No associations
LandOfFree
The onset of star formation in primordial haloes does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The onset of star formation in primordial haloes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The onset of star formation in primordial haloes will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-235018