Astrophys. J., 779, 51 (2013/December-2)
Subarcsecond observations of NGC 7538 IRS 1: continuum distribution and dynamics of molecular gas.
ZHU L., ZHAO J.-H., WRIGHT M.C.H., SANDELL G., SHI H., WU Y.-F., BROGAN C. and CORDER S.
Abstract (from CDS):
We report new results based on the analysis of the Submillimeter Array (SMA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of NGC 7538 IRS 1 at 1.3 and 3.4 mm with subarcsecond resolutions. With angular resolutions ∼0.''7, the SMA and CARMA observations show that the continuum emission at 1.3 and 3.4 mm from the hyper-compact H II region IRS 1 is dominated by a compact source with a tail-like extended structure to the southwest of IRS 1. With a CARMA B-array image at 1.3 mm convolved to 0.''1, we resolve the hyper-compact H II region into two components: an unresolved hyper-compact core, and a north-south extension with linear sizes of <270 AU and ∼2000 AU, respectively. The fine structure observed with CARMA is in good agreement with the previous Very Large Array results at centimeter wavelengths, suggesting that the hyper-compact H II region at the center of IRS 1 is associated with an ionized bipolar outflow. We image the molecular lines OCS(19-18) and CH3CN(12-11) as well as 13CO(2-1) surrounding IRS 1, showing a velocity gradient along the southwest-northeast direction. The spectral line profiles in 13CO(2-1), CO(2-1), and HCN(1-0) observed toward IRS 1 show broad redshifted absorption, providing evidence for gas infall with rates in the range of 3-10x10–3 M☉/yr inferred from our observations.
H II regions - ISM: jets and outflows - ISM: kinematics and dynamics - ISM: molecules - radio lines: ISM - stars: formation
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