ISO LWS Spectroscopy of M82: A Unified Evolutionary Model
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).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1999
- Accession Number
- ADA464679
Entities
People
- Howard A. Smith
- Jacqueline Fischer
- James W. Colbert
- Luigi Spinoglio
- Matthew A. Malkan
- Michael Luhman
- Peter E. Clegg
- Pierre Cox
- Shobita Satyapal
- Steven D. Lord
Organizations
- University of California, Los Angeles