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Detection of H53-alpha emission from M82 - A reliable measure of the ionization rate and its implications

1989; IOP Publishing; Volume: 345; Linguagem: Inglês

10.1086/167891

1538-4357

P. J. Puxley, P. W. J. L. Brand, T. J. T. Moore, C. M. Mountain, Naomasa Nakai, Takuji Yamashita,

Astronomy and Astrophysical Research

view Abstract Citations (63) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of H53 alpha Emission from M82: A Reliable Measure of the Ionization Rate and Its Implications Puxley, P. J. ; Brand, P. W. J. L. ; Moore, T. J. T. ; Mountain, C. M. ; Nakai, N. ; Yamashita, T. Abstract Emission in the hydrogen recombination line H53α has been detected, for the first time, in another galaxy: the nearby "starburst" system M82. This line is produced primarily by spontaneous emission and provides the most direct, extinction-independent estimate of the ionization rate in the star-forming complex. The line strength implies an ionization rate of 1.1 x 10^54^ s^-1^, approximately 5 times larger than that inferred from Brα observations, and indicates a dust extinction at 4 microns of more than 1 mag (A_v_ ~ 27 mag). Comparison of the 3.3 mm free-free continuum and H53α fluxes implies an average electron temperature of T_e_ ~ 5 x 10^3^ K. Analysis of the line excitation conditions, using the H53α emission in conjunction with that in the far-IR O^2+^ and N21 forbidden lines, together with the IR luminosity, suggests that only a very restricted range of stellar masses are formed. Less plausible interpretations are (1) that approximately two-thirds of the direct stellar emission escapes from the central 40" without encountering dust and (2) that much of the line emission and IR luminosity arises via fast (~ 100 km s^-1^) shocks. Publication: The Astrophysical Journal Pub Date: October 1989 DOI: 10.1086/167891 Bibcode: 1989ApJ...345..163P Keywords: Emission Spectra; Interstellar Matter; Irregular Galaxies; Star Formation; Electron Energy; Far Infrared Radiation; Forbidden Bands; Ionization; Recombination Reactions; Stellar Mass; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M82; GALAXIES: INTERSTELLAR MATTER; INTERSTELLAR: GRAINS full text sources ADS | data products SIMBAD (1) NED (1)