Study of Radio Continuum, Ammonia, and Water Maser Observations of Bright, Unassociated IRAS Point Sources

Details Study of Radio Continuum, Ammonia, and Water Maser Observations of Bright, Unassociated IRAS Point Sources Study of Radio Continuum, Ammonia, and Water Maser Observations of Bright, Unassociated IRAS Point Sources

Dec 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993phdt.......257m&link_type=abstract

Ph.D. Thesis, Universidad Complutense de Madrid, Spain (1993)

Computer Science

Scientific paper

This work is based on the results provided by IRAS infrared satellite. In the IRAS point source catalog there were a considerable number of bright sources, namely 146 (with flux densities larger than 1000 Jy at 60 or 100 microns), which were not associated with known objects, that is to say, they did not appear in any of the 37 catalogs considered when looking for associations with IRAS sources; and only 23 of them showed water maser emission. In this thesis we continue the study of a subset of these objects (in total 12, one half with associated water maser emission) by means of: matching-beam VLA observations at 6 and 2 cm, single-dish observations at the Haystack Observatory in the (1,1) and (2,2) inversion transitions of ammonia, and in the rotational transition 6_(16)-5_(23) of water vapor. The radio continuum observations revealed the presence of associated sources in ten of the twelve cases, and we were able to determine their nature, parameters and morphology. In the ammonia and water vapor observations we detected the dense gas associated with most of these regions; at the same time we obtained a good determination of the kinematic distance to the objects, and consequently, the first reliable estimation of their luminosity. Most of these regions have flat spectral indices (derived from radio data) consistent with optically thin H II regions; and the temperature derived for the ammonia (~20 K) suggests the association of dense molecular gas with embedded heating sources. The high percentage of association of the radio continuum emission and molecular gas with these sources, together with the IRAS fluxes and colors, is consistent with these unassociated, bright IRAS sources being sites of recent star formation containing late O or early B-type stars.

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