The Cygnus X region. XVIII. A detailed investigation of radio-continuum structure on large and small scales.
Abstract
The Cygnus X region has been observed at 408 and 1420 MHz with angular resolution 3.5 X 5.2 and 1.0 x 1.% arcmin. Maps of continuum emission at these two frequencies are presented. The 408 MHz map, covering a 9^deg^ field. has been compared with the 4800 MHz data of Wendker (1984). A map of temperature spectral index β has been computed over the area common to the two observations. The emission from Cygnus X is primarily optically thin thermal radiation. superimposed on a smooth non-thermal background of brightness 50 +/- 10 K at 408 MHz with β = 2.8. No new supernova remnants of large angular extent have been detected brighter than {SIGMA}_408_ = 5 10^21^ W m^-2^ Hz^-1^ sr^-1^. In the Cyg OB2 association at the centre of the field, the limit is three times lower. The absence of a detectable supernova remnant in the association is combined with other evidence to conclude that the association is young and that no supernova has occurred within it. The properties of the known supernova remnant G78.2 + 2.1 are discussed in detail. Properties of small-diameter sources at 408, 1420 and 4800 MHz are tabulated, and some are discussed in detail, including a possible new supernova remnant and a thermal shell source, possibly a wind-blown bubble. A prominent feature of the extended thermal emission is its filamentary structure. Thirteen emission ridges are identified, which show steep outer edges and contain compact thermal sources. They may be ionized by strings of B stars which have formed inside them. The new high-resolution data have been combined with other observations to yield new conclusions about many extended thermal emission regions. An H II, region of extent ~2 arcmin has been detected around Cyg X-3.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1991
- Bibcode:
- 1991A&A...241..551W
- Keywords:
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- Continuous Radiation;
- Radio Sources (Astronomy);
- Supernova Remnants;
- Astronomical Spectroscopy;
- B Stars;
- Brightness Distribution;
- Cygnus Constellation;
- H Ii Regions;
- survey;
- Cygnus X;
- radio sources;
- supernova remnants;
- H II regions.;
- Astrophysics