2008 Supplement: Frascati Workshop 2007 / Dado

Gamma-Ray Bursts, Supernovae and Metallicity in the Intergalactic Medium

S. Dado, A. Dar, A. de Rújula


The mean iron abundance observed in the intergalactic medium (IGM)
within galaxy clusters and without galaxy clusters is consistent with
the mean amount of iron per unit volume in the Universe which has been
produced by standard supernova (SN) explosions with a rate proportional
to the cosmic star-formation rate. If most SNe took place inside
galaxies, then the IGM could have been enriched with their metals by
galactic winds and jets that swept most of the galactic gas with the SNe
ejecta into the IGM. A significant fraction of the early SNe, however,
could have taken place outside galaxies or within dwarf galaxies, which
were later disrupted by tidal interactions, and/or mass loss through
fast winds, SN ejecta and jets. Little is known about such
intergalactic SNe at high red-shifts. They could have occurred primarily
in highly obscured environments, avoiding detection. Supporting evidence
for intergalactic SNe is provided by SNe associated with gamma ray
bursts (GRBs) without a host galaxy and from the ratio of well localized
GRBs with and without a host galaxy. A direct test of whether a
significant contribution to the iron abundance in the IGM came from
intergalactic SNe would require the measurement of their rate per
comoving unit volume as function of red-shift. This may be feasible
with IR telescopes, such as the Spitzer Space Telescope.


supernova gamma ray bursts metalicity intergalactic space

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