153 research outputs found
Collapse of the Primordial Gas Clouds in the Presence of UV Radiation Field
Our goal is to study the effects of the UV radiation from the first stars,
quasars and hypothetical Super Heavy Dark Matter (SHDM) particle decays on the
formation of primordial bound objects in the Universe. We trace the evolution
of a spherically symmetric density perturbation in the Lambda Cold Dark Matter
and MOND model, solving the frequency-dependent radiative transfer equation,
non-equilibrium chemistry, and one-dimensional gas hydrodynamics. We
concentrate on the destruction and formation processes of the molecule,
which is the main coolant in the primordial objects.Comment: To appear in the proceedings of the Island Universes conference held
in Terschelling, Netherlands, July 2005, ed. R. de Jon
Thermal evolution of the primordial clouds in warm dark matter models with keV sterile neutrinos
We analyze the processes relevant for star formation in a model with dark
matter in the form of sterile neutrinos. Sterile neutrino decays produce an
X-ray background radiation that has a two-fold effect on the collapsing clouds
of hydrogen. First, the X-rays ionize the gas and cause an increase in the
fraction of molecular hydrogen, which makes it easier for the gas to cool and
to form stars. Second, the same X-rays deposit a certain amount of heat, which
could, in principle, thwart the cooling of gas. We find that, in all the cases
we have examined, the overall effect of sterile dark matter is to facilitate
the cooling of gas. Hence, we conclude that dark matter in the form of sterile
neutrinos can help the early collapse of gas clouds and the subsequent star
formation.Comment: aastex, 31 pages, 4 figures; one figure and some references added,
minor changes in the text; to appear in Astrophysical Journa
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