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A photoionization instability in the early intergalactic mediumIt is argued that any fairly uniform source of ionizing photons can be the cause of an instability in the pregalactic medium on scales larger than a photon path length. Underdense regions receive more ionizing energy per atom and reach higher temperature and entropy, driving the density down still further. Fluctuations created by this instability can lead to the formation of structures resembling protogalaxies and intergalactic clouds, obviating the need for gas clouds or density perturbations of earlier cosmological provenance, as is usually assumed in theories of galaxy and structure formation. Characteristic masses for clouds produced by the instability, with log mass in solar units plotted against log radius in kpc, are illustrated.
Document ID
19920073273
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hogan, Craig J. (Washington, University Seattle, United States)
Date Acquired
August 15, 2013
Publication Date
September 3, 1992
Publication Information
Publication: Nature
Volume: 359
Issue: 6390,
ISSN: 0028-0836
Subject Category
ASTROPHYSICS
Distribution Limits
Public
Copyright
Other