Computer Science – Sound
Scientific paper
Apr 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991aipc..222..357m&link_type=abstract
After the first three minutes. AIP Conference Proceedings, Volume 222, pp. 357-360 (1991).
Computer Science
Sound
Hydrodynamics, Origin And Formation Of The Universe
Scientific paper
Discrete sources of photoionizing radiation present at the time the intergalactic medium is largely neutral will create expanding H ii regions. A source which turns off or dims quickly enough will not be able to maintain the advance of its ionization front indefinitely. The high pressure of the relict H ii region will then drive a shock into the cold, neutral ambient medium. We discuss the hydrodynamical evolution of relict cosmological H ii regions generated at redshifts z~5-15. A thin shell of shocked material develops around the H ii region. The peculiar velocity of the shell is typically 10-20 km s-1. The dense shell may cool and fragment into objects with baryonic masses as high as 106-108 Msolar and column densities of order 1019 cm-2. These values are independent of the nature of the photoionizing source. They are set only by the density of the IGM, the sound speed of 104 K gas, and the age of the shell. The shock propagation ceases once the filling factor of the H ii regions reaches unity and the IGM is photoionized. The clouds formed may account for the Lyα forest seen in the spectra of high redshift QSOs. Gravitationally bound fragments may be candidates for blue-excess galaxies at high redshift.
Madau Piero
Meiksin Avery
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