Low Velocity Ionized Winds from Regions Around Young O Stars

Details Low Velocity Ionized Winds from Regions Around Young O Stars Low Velocity Ionized Winds from Regions Around Young O Stars

Dec 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998aas...193.1602j&link_type=abstract

American Astronomical Society, 193rd AAS Meeting, #16.02; Bulletin of the American Astronomical Society, Vol. 30, p.1277

Astronomy and Astrophysics

Astronomy

Scientific paper

We have observed seven ultracompact H II regions in hydrogen recombinaton lines in the millimeter band. Toward four of these regions, there is a high velocity (60-80 km s(-1) wide) component in the line profiles. The high velocity gas accounts for 35%-70% of the emission measure within the beam. We compare these objects to an additional seven similar sources we have found in the literature. The broad recombination line objects (BRLOs) make up about 30% of all sources in complexes containing ultracompact H II regions. Comparison of spectral line and continuum data implies that the BRLOs coincide with sources with rising spectral indices. Both the numbers of BRLOs and their frequency of occurrence within H II region complexes, when coupled with their small size and large internal motions, mean that the apparent contradiction between the dynamical and population lifetime for BRLOs is even more severe than for ultracompact H II regions as a whole. We evaluate a number of possible models for the origin of the broad recombination line emission. The lifetime, morphology and rising spectral index of the sources argue for photoevaporated disks as the cause for BRLOs. Existing models for such regions, however, contain only ad hoc arguments as to why it should be possible to produce the observed supersonic motions in the wind arising from a photoevaporated disk. This work was supported in part by National Science Foundation grant 95-30695 to the University of Texas at Austin.

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