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arxiv astro-ph/9902345 v1 pith:55YOWTU6 submitted 1999-02-24 astro-ph

Low Velocity Ionized Winds from Regions Around Young O Stars

classification astro-ph
keywords regionsbrloslinesourcesrecombinationspectralultracompactvelocity
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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We have observed seven ultracompact HII regions in hydrogen recombination lines in the millimeter band. Toward four of these regions, there is a high velocity (full width to half maximum 60-80 km/s) 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 HII regions. Comparison of spectral line and continuum data implies that the BRLOs coincide with sources with rising spectral indices, >=0.4 up to 100 GHz. Both the number of BRLOs and their frequency of occurrence within HII region complexes, when coupled with their small size and large internal motions, mean that the apparent contradiction between the dynamical and population lifetimes for BRLOs is even more severe than for ultracompact HII regions. We evaluate a number of models for the origin of the broad recombination line emission. The lifetime, morphology, and rising spectral index of the sources argue for photo- evaporated disks as the cause for BRLOs. Existing models for such regions, however, do not account for the large amounts of gas observed at supersonic velocities.

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Cited by 1 Pith paper

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  1. Ionized gas emission in protoplanetary disks with the SKAO

    astro-ph.SR 2026-07 conditional novelty 4.0

    Synthetic SKA-Mid observations of simulated MHD and photoevaporative disk winds show that free-free emission is detectable in hours and stacked hydrogen recombination lines are spectrally resolvable in ~10 hours.