Radio continuum observations of M 82.
Abstract
The starburst galaxy M82 has been mapped at λ = 9mm with the Effelsberg 100-m telescope, with an angular resolution of 26.5". The observed distribution of the emission compared to those published at lower frequencies and can be traced out to z-distances of <~500 pc from the plane of the galaxy. The radio spectrum appears to steepen rapidly with increasing distance from the plane, indicating aging of the relativistic electrons. Further measurements obtained by mapping M82 at λ = 2.8cm, 2.0cm, and 1.2cm allow us to set more stringent limits to the thermal content of M82 which is significantly below previous estimates. A thorough analysis of the integrated spectrum of M82 including the far-infrared emission is carried out to estimate the Lyman continuum flux. The Lyman continuum flux obtained from the thermal flux density is only about 1/3 of the value derived from the far-infrared luminosity, implying that a large fraction of the Lyman flux produced by massive stars is absorbed by dust resident in numerous dense H II regions. The steepening of the radio spectrum away from the galaxy plane indicates aging times for the relativistic electrons of ~10^5^ yr and an upper limit to the wind speed of the relativistic gas of ~4000 km s^-1^. The equipartition values derived for the energy density of the relativistic electrons and the total magnetic field strength are ~60 eV cm^-3^ and ~50μG, respectively.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- January 1988
- Bibcode:
- 1988A&A...190...41K
- Keywords:
-
- Continuous Spectra;
- Irregular Galaxies;
- Radio Sources (Astronomy);
- Star Formation;
- Starburst Galaxies;
- Astronomical Maps;
- Brightness Temperature;
- Far Infrared Radiation;
- Lyman Spectra;
- Relativistic Particles;
- Astrophysics