On the nature of 21 cm emission profile structure at high galactic latitude: Implications for the warm neutral medium
G. L. Verschuur, L. Magnani;
AJ, 1994, 107, 287
ABSTRACT:Gaussian analysis of neutral hydrogen emission profiles obtained with the Arecibo 309 m, the National Radio Astronomy Obsevatory (NRAO) 140
ft, and the Hat Creek 25 m radio telescopes reveal three distinct linewidth
regimes.
Component 1 is typically from 25-50 km/s wide and may be due to Galactic emission in
far sidelobes, although this remains to be proven.
The bulk of this study
concerns Component 2, a pervasive feature approx.
12 km/s wide (full width at
half maximum brightness), although somewhat narrower toward the North
Polar Spur.
If this component is due to a warm neutral medium, its linewidth
implies a temperature of approx.
3000 K, substantially lower than many of the
canonical values for this medium in the literature.
On the other hand, there is
evidence to suggest that at least some of this component may be due to the
superposition of unresolved cool features in the beam.
Component 3 encompasses
narrow fearures with linewidths in the 2-6 km/s range with the majority around
3 km/s.
KEYWORDS: emission spectra, h i regions, hydrogen, neutral gases, spectral line width, stellar temperature, hydrogen clouds, interstellar matter, line spectra, spectrum analysis, stellar spectra
PERSOKEY:h_i, 21 cm, general ism, ,
CODE: verschuur94