Interpretation of neutral hydrogen spin temperature measurements
H. E. Payne, E. E. Salpeter, Y. Terzian;
ApJ, 1983, 272, 540
ABSTRACT:Arecibo 3-arcsec beam neutral hydrogen emission-absorption observations are analyzed, and spin temperature results in the direction of 'small'
and 'large' extragalactic sources are found to be statistically
similar.
The variations in derived spin temperature from case to case are
threrefore real.
The mean emission temperature as a function of velocity is
determined for widely dispersed warm material which is independent of a cloud and
not strongly absorbing.
Correcting the emission-absorption data for
the contribution of this material's emission yields harmonic mean cloud
spin temperatures which vary approximately as the -1/3 power of the cloud
optical depth.
It is not yet known whether a measured cloud spin temperature
represents a single gas temperature or a composite, as in the type of model proposed
by McKee and Ostriker (1977).
KEYWORDS: hydrogen clouds, interstellar matter, radio sources (astronomy), spin temperature, absorption spectra, centimeter waves, temperature measurement
PERSOKEY:h_i, ,
CODE: payne83