The radiative feedback of the first cosmological objects
Mar, 1999
16 pages
Published in:
- Astrophys.J. 534 (2000) 11-24
e-Print:
- astro-ph/9903336 [astro-ph]
DOI:
Report number:
- FERMILAB-PUB-99-041-A
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Abstract: (arXiv)
In hierarchical models of structure formation, an early cosmic UV background (UVB) is produced by the small (T_vir < 10^4 K) halos that collapse before reionization. The UVB at energies below 13.6eV suppresses the formation of stars or black holes inside small halos, by photo-dissociating their only cooling agent, molecular H2. We self-consistently compute the buildup of the early UVB in Press-Schechter models, coupled with H2 photo-dissociation both in the intergalactic medium (IGM), and inside virialized halos. We find that the intergalactic H2 has a negligible effect on the UVB, both because its initial optical depth is small (tau<0.1), and because it is photo-dissociated at an early stage. If the UV sources in the first collapsed halos are stars, then their UV flux suppresses further star-formation inside small halos. This results in a pause in the buildup of the UVB, and reionization is delayed until larger halos (T_vir> 10^4 K) collapse. If the small halos host mini-quasars with hard spectra extending to approximately 1 keV, then their X-rays balance the effects of the UVB, the negative feedback does not occur, and reionization can be caused by the small halos.Note:
- 16 pages, 16 figures included, uses emulateapj.sty. Submitted to ApJ Report-no: FERMILAB-Pub-99/041-A
- COSMOLOGY THEORY
- EARLY UNIVERSE
- GALAXIES FORMATION
- MOLECULAR PROCESSES
- RADIATIVE TRANSFER
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