Detection of far-infrared forbidden O I and forbidden O III emission from the galaxy M82

Observations in M82 of the lowest-lying transitions of neutral and doubly ionized oxygen, forbidden O I 63.2 microns and forbidden O III 88.4 microns, which have wavelengths at which the extinction toward M82 is negligible, are reported. For O III, the +220 km/s velocity of the line center with respect to the local standard of rest, the 300 km/s intrinsic line width, and the asymmetry of the profile are consistent with the systemic velocity and rotational broadening seen in other ionic lines in the nucleus of M82. The fraction of oxygen that is present in doubly ionized form, indicates that the ionization state is similar to that found in H II regions in the disk of the Milky Way Galaxy. The central velocity of the O I line is +130 km/s, and no broadening in excess of instrumental resolution is seen. This result appears to rule out association of this emission with the periphery of the central H II region.