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arXiv · 1309.6112

Sub-arcsec Observations of NGC 7538 IRS 1: Continuum Distribution and Dynamics of Molecular Gas

Lei Zhu·Jun-Hui Zhao·Melvyn Wright·Göran Sandell·Hui Shi·Yue-Fang Wu·Crystal Brogan·Stuartt Corder
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Abstract

We report new results based on the analysis of the SMA and CARMA observations of NGC 7538\,IRS\,1 at 1.3 and 3.4 mm with sub-arcsec resolutions. With angular resolutions $\sim$ 0\farcs7, the SMA and CARMA observations show that the continuum emission at 1.3 and 3.4 mm from the hyper-compact \ion{H}{2} 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\farcs1, we resolve the hyper-compact \ion{H}{2} region into two components: an unresolved hyper-compact core, and a north-south extension with linear sizes of $<270$ AU and $\sim$2000 AU, respectively. The fine structure observed with CARMA is in good agreement with the previous VLA results at centimeter wavelengths, suggesting that the hyper-compact \ion{H}{2} region at the center of IRS\,1 is associated with an ionized bipolar outflow. We image the molecular lines OCS(19-18) and CH$_3$CN(12-11) as well as $^{13}$CO(2-1) surrounding IRS\,1, showing a velocity gradient along the southwest-northeast direction. The spectral line profiles in $^{13}$CO(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 $3-10\times10^{-3}$ M$_\odot$ yr$^{-1}$ inferred from our observations.

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Lei Zhu, Jun-Hui Zhao, Melvyn Wright, Göran Sandell, Hui Shi, Yue-Fang Wu, Crystal Brogan, Stuartt Corder. 2013-09-24. Sub-arcsec Observations of NGC 7538 IRS 1: Continuum Distribution and Dynamics of Molecular Gas. https://doi.org/10.1088/0004-637x%2F779%2F1%2F51

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