Max Tegmark's cosmology library: minmass
Figure 6: The minimum mass needed to collapse.
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How small were the first cosmological objects?
Authors:
Max Tegmark,
Joseph Silk,
Martin Rees,
Alain Blanchard,
Tom Abel
& Francesco Palla
Abstract:
The minimum mass that a virialized gas cloud must have
in order to be able to cool in a Hubble time is computed,
using a detailed treatment of the chemistry
of molecular hydrogen. With a simple model for halo profiles,
we reduce the problem to that of numerically integrating
a system of chemical equations. The results agree well with
numerically expensive 3D simulations, and our approach has
the advantage of rapidly being able to explore large
regions of parameter space.
The minimum baryonic mass M_b is found to be strongly
redshift dependent, dropping from 10^6 solar masses at z=15 to
5000 solar masses at z=100 as molecular cooling becomes effective.
For z>>100, M_b rises again, as CMB photons inhibit
H_2-formation through the H^- channel. Finally, for z>>200,
the H_2^+ channel for H_2-formation becomes effective, driving
M_b down towards 10^3 solar masses.
With a standard CDM power spectrum withsigma_8=0.7,
this implies that a fraction 10^{-3} of all baryons may have
formed luminous objects by z=30, which could be sufficient to
reheat the universe.
Reference info:
Published in ApJ, 474, 1-12 (1997)
Online references:
This site also contains the latest versions of some papers that are referenced in
the text;
Tom Abel's thesis,
Max Tegmark's thesis,
Tegmark & Silk 1994,
Tegmark, Silk & Blanchard & 1994,
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This page was last modified July 1, 1998.
max@ias.edu