NGC 7538 IRS1—an O Star Driving an Ionized Jet and Giant N-S Outflow
Abstract
NGC 7538 IRS 1 is a very young embedded O star driving an ionized jet and accreting mass with an accretion rate >10-4 ${M}_{\odot }$ yr-1, which is quenching the hypercompact H II region. We use SOFIA GREAT data, Herschel PACS and SPIRE archive data, SOFIA FORCAST archive data, Onsala 20 m and CARMA data, and JCMT archive data to determine the properties of the O star and its outflow. IRS 1 appears to be a single O star with a bolometric luminosity >1 × 105 ${L}_{\odot }$ , i.e., spectral type O7 or earlier. We find that IRS 1 drives a large molecular outflow with the blueshifted northern outflow lobe extending to ∼280″ or 3.6 pc from IRS 1. Near IRS 1 the outflow is well aligned with the ionized jet. The dynamical timescale of the outflow is ∼1.3 × 105 yr. The total outflow mass is ∼130 ${M}_{\odot }$ . We determine a mass outflow rate of 1.0 × 10-3 ${M}_{\odot }$ yr-1, roughly consistent with the observed mass accretion rate. We observe strong high-velocity [C II] emission in the outflow, confirming that strong UV radiation from IRS 1 escapes into the outflow lobes and is ionizing the gas. Many O stars may form like low-mass stars, but with a higher accretion rate and in a denser environment. As long as the accretion stays high enough to quench the H II region, the star will continue to grow. When the accretion rate drops, the H II region will rapidly start to expand.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2020
- DOI:
- 10.3847/1538-4357/abbf5b
- arXiv:
- arXiv:2010.04289
- Bibcode:
- 2020ApJ...904..139S
- Keywords:
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- Radio jets;
- Compact H II region;
- Giant molecular clouds;
- Star formation;
- O stars;
- Stellar accretion;
- Stellar accretion disks;
- 1347;
- 286;
- 653;
- 1569;
- 1137;
- 1578;
- 1579;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, 19 figures. Accepted for publication in The Astrophysical Journal