Issue |
A&A
Volume 489, Number 2, October II 2008
|
|
---|---|---|
Page(s) | 505 - 515 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:200809831 | |
Published online | 30 July 2008 |
First supernovae in dwarf protogalaxies
1
Tartu Observatory, 61602 Tõravere, Estonia
2
Institute of Physics, Southern Federal University, Stachki Ave. 194, Rostov-on-Don 344090, Russia e-mail: eugstar@mail.ru
3
Institute for Computational Astrophysics, Saint Mary's University, Halifax, B3H 3C3, Canada e-mail: vorobyov@ap.smu.ca
4
Department of Physics, Southern Federal University, Sorge St. 5, Rostov-on-Don 344090, Russia e-mail: yus@phys.rsu.ru
5
Special Astrophysical Observatory, Nizhny Arkhyz, Karachai-Cherkessia 369167, Russia
Received:
23
March
2008
Accepted:
21
July
2008
Context. This paper is motivated by the recent detection of many extremely metal-deficient
() stars in the Milky Way.
Aims. We numerically explore the chemical, thermal, and dynamical evolution of a shell formed by a high-energy supernova explosion (1053 erg) in dwarf protogalaxies with a total (dark matter plus baryonic) mass at a redshift
.
We consider two initial configurations for the baryonic matter, one without rotation and the other having the ratio of rotational to gravitational energy
. The (non-rotating) dark matter halo is described by a quasi-isothermal sphere. This choice is motivated by recently proposed mechanisms for rapid flattening of a central cuspy region in dwarf protogalaxies.
Methods. We use a finite-difference numerical hydrodynamics code to simulate supernova explosions in dwarf protogalaxies with axial symmetry. The advection is treated using a third-order piecewise parabolic scheme. The heating and cooling processes in the gas are taken into account by solving the rate equations numerically for the main atomic, molecular, and ionic species in the primordial gas.
Results. We find that the dynamics of the shell is different in protogalaxies with and those without rotation. For instance, the Rayleigh-Taylor instability in the shell develops faster in
protogalaxies without rotation. The fraction of a blown-away baryonic mass
is approximately twice as high in models with rotation than in models without rotation. We argue that these differences are
caused by different initial gas density profiles in non-rotating and rotating protogalaxies.
On the other hand, the chemical evolution of gas in protogalaxies with
and without rotation is found to be similar. The relative number
densities of molecular hydrogen and HD molecules in the cold gas
( K) saturate at typical values of 10-3 and
10-7, respectively. The saturation times in models with
rotation are somewhat longer than in models without rotation.
The clumps formed in the fragmented shell move with velocities that
are at least twice as high as the escape velocity. The mass of the
clumps is ~0.1–10
, which is lower
than the Jeans mass. We conclude that the clumps are pressure
supported.
Conclusions. A supernova explosion with energy 1053 erg destroys
our model protogalaxy. The clumps formed in the fragmented shell
are pressure supported. We conclude that protogalaxies with a total mass
are unlikely to form stars due to high-energy supernova explosions of the first stars.
Key words: cosmology: early Universe / galaxies: formation / ISM: molecules / stars: formation / shock waves
© ESO, 2008
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