Issue |
Astron. Astrophys. Suppl. Ser.
Volume 137, Number 1, May II 1999
|
|
---|---|---|
Page(s) | 7 - 19 | |
DOI | https://doi.org/10.1051/aas:1999239 | |
Published online | 15 May 1999 |
The radio emission from the Galaxy at 22 MHz
1
National Research Council Canada, Herzberg Institute of Astrophysics, Dominion Radio Astrophysical Observatory, Penticton, B.C. Canada V2A 6K3 e-mail: robert.roger@hia.nrc.ca
2
Now at University of Victoria, Victoria, B.C., Canada
Send offprint request to: R.S. Roger
Received:
22
October
1998
Accepted:
4
January
1999
We present maps of the 22 MHz radio emission between declinations
-28° and +80°, covering ~73% of the sky, derived
from observations with the 22 MHz radiotelescope at the Dominion Radio
Astrophysical Observatory (DRAO). The resolution of the telescope (EW
× NS) is 1.1°
× 1.7° secant(zenith angle).
The maps show the large scale features of the emission from the Galaxy
including the thick non-thermal disk, the North Polar Spur (NPS) and
absorption due to discrete Hii regions and to an extended band
of thermal electrons within 40° of the Galactic centre. We give
the flux densities of nine extended supernova remnants shown on the
maps. A comparison of the maps with the 408-MHz survey of
Haslam et al. (1982) shows a remarkable uniformity of spectral index
() of most of the Galactic emission, with
β in the range 2.40 to 2.55. Emission from the outer rim of the
NPS shows a slightly greater spectral index than the distributed
emission on either side of the feature. The mean local synchrotron
emissivity at 22 MHz deduced from the emission toward nearby extended
opaque Hii regions is
~1.5 10-40 Wm-3 Hz-1 sr-1, somewhat
greater than previous estimates.
Key words: Galaxy: structure / radio continuum: general; ISM
© European Southern Observatory (ESO), 1999