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Abstract:
We present the first complete far-infrared spectrum (43-197 micrometers) of M82, the brightest infrared galaxy in the sky, taken with the Long Wavelength Spectrometer of the Infrared Space Observatory (ISO). We detected seven fine structure emission lines, [O I] 63 and 145 micrometers, [O III] 52 and 88 micrometers , [N II] 122 micrometers, [N III] 57 micrometers, and [C II] 158 micrometers, and fitted their ratios to a combination starburst and photodissociation region (PDR) model. The best fit is obtained with H II regions with n=250/cu cm, an ionization parameter of 10(exp -3.5), and PDRs with n=10(exp 3.3)/cu cm and a far-ultraviolet flux of Go=10(exp 2.8). We applied both continuous and instantaneous starburst models, with our best fit being a 3-5 Myr old instantaneous burst model with a 100 M (sun) cutoff. We also detected the ground-state rotational line of OH in absorption at 119.4 micrometers. No excited level OH transitions are apparent, indicating that the OH is almost entirely in its ground state with a column density ~4x10(exp 14) sq cm. The spectral energy distribution over the long-wavelength spectrometer wavelength range is well fitted with a 48 K dust temperature and an optical depth, Tau(sub Dust) proportional to varies as gamma (exp -1).
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Journal article |
| Pages: |
10 |
| Report Date: |
1999 |
| Report Number: |
A976464 |
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