VLA observations of the (N-15)H3 maser associated with NGC 7538 IRS 1

Abstract

Emission in the (J, K) = (3, 3) inversion line of ortho- (N-15)H3 associated with NGC 7538 IRS 1 has been found to be coincident with the continuum peak emission. The brightness temperature of the most intense feature, at -60 km/s, is larger than 5200 K. This maser emission may be due to amplification of the background H II region. The maser emission arises from many discrete sources distributed over a north-south extent of roughly 0.3 arcsec. The (N-15)H3, H2CO, and OH (1665 MHz) emission probably all originate in a common highly clumped compact region that is in front of the H II region. The H II region appears to be optically thick at centimeter wavelengths and maser emission from these molecules may be a good probe of neutral gas near ultracompact H II regions.