Radio studies of the ionized gas in the nucleus of M82

Journal Article · Mon Jul 15 04:00:00 EDT 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163322· OSTI ID:5373005

Seaquist, E R; Bell, M B; Bignell, R C

We report here VLA observations of the radio continuum and radio recombination lines from the nearby gas-rich galaxy M82. We have combined these data with other radio and IR data, both continuum and line, to gain further insight into the state of the interstellar gas and relativistic particles in M82. With the aid of a simple model for the distribution of the gas and synchrotron emissivity, we interpret a ''vertical'' spectral index gradient in M82 as a corresponding gradient in the age of the radiating particles. We infer that the relativistic particles are being transported out of the plane at a speed of about 2000 km s/sup -1/, possibly by a highly rarefied galactic wind. A detailed study of the radio recombination lines and the radio continuum shows that the ionized gas in M82 which is coextensive with the synchrotron emission in the central region has a maximum density of about 30 cm/sup -3/ and a volume filling factor near unity. The large filling factor indicates that the ionized gas occupies most of the volume within the nuclear region. The molecular gas in M82 is confined to small clouds which are in pressure equilibrium with the ionized gas. This configuration could have resulted from the expansion of the numerous H II regions resulting from intense star formation in M82. A compact H II complex near the compact VLBI source 41.9+58 is evident in the VLA recombination line data. It is coincident in position and velocity with features seen in CO J = 1-0 and J = 2-1 lines, as well as in the 63 ..mu..m line of (O I). The possible nature of this complex is briefly discussed.

• Research Organization: Department of Astronomy, University of Toronto
• OSTI ID: 5373005
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 294:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COSMIC GASES
COSMIC RADIO SOURCES
ELECTROMAGNETIC RADIATION
EMISSIVITY
FLUIDS
GALAXIES
GALAXY NUCLEI
GASES
H2 REGIONS
IONIZATION
MORPHOLOGY
NEBULAE
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
RADIO GALAXIES
RADIOWAVE RADIATION
RECOMBINATION
STAR EVOLUTION
SURFACE PROPERTIES