Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1970
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1970ap%26ss...7..160m&link_type=abstract
Astrophysics and Space Science, Volume 7, Issue 1, pp.160-173
Astronomy and Astrophysics
Astrophysics
1
Scientific paper
The physical state of a moderately dense, uniform, pure hydrogen medium, pervading the metagalaxy and partaking in the general cosmic expansion, is considered. The cosmic X-ray photon spectrum, which is now observed down to about 0.25 keV, together with various plausible extrapolations down to the Lyman limit, is invoked as the source of ionization and heating of this medium. Isothermal and adiabatic modes of expansion of the intergalactic medium are studied as limiting cases of the present mode of expansion. The isothermal mode generates highly ionized but ‘lukewarm’ (7700 K≤T≤25000 K) models of the medium, with the, so far unknown, turnover point in the cosmic X-ray spectrum as the parameter required to fix the temperature and degree of ionization uniquely, for any assumed value of the present density. The adiabatic mode, while giving rise to high degrees of ionization, also produces significantly higher temperatures which are independent of density and always greater than about 28000 K. In conclusion, a possible explanation for the anomalous 3C 9 result is adduced.
Axford Wiliam Ian
Mendis Asoka D.
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