Radio continuum, ammonia, and water maser observations of bright, unassociated IRAS point sources
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Abstract
We present matching-beam 6 and 2 em radio continuum observations made with the Very Large Array, and ammonia and water maser observations made at the Haystack Observatory of 12 IRAS point sources selected from the survey of Scalise, Rodriguez, & Mendoza-Torres (1989) of bright, unassociated IRAS point sources. These sources have 60 or 100 m flux densities in excess of l0 Jy and have no previous reference in any of the 37 catalogs considered for association of IRAS sources with known sources. Six of the 12 sources have associated radio continuum, ammonia, and water maser emission, and all of them show at least one of these three emissions. In all sources detected, the ammonia is warm (T 20 K) and suggests the association of dense molecular gas with embedded heating sources. It is argued that all sources in the sample could be associated with time-variable H2O maser emission. The radio and far-infrared data appear to indicate that these sources are star-forming regions, powered by a late 0 or early B-type star. Several of the sources of lower luminosity ( 5 x 10 3LO) appear to have ionizing photon fluxes in excess of those expected for a zero-age main-sequence star. Possible explanations for this discrepancy are discussed. Subject headings: H II regions - infrared: ISM: continuum - infrared: ISM: lines and bands - masers - radio continuum: ISM