Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004apj...600..269s&link_type=abstract
The Astrophysical Journal, Volume 600, Issue 1, pp. 269-278.
Astronomy and Astrophysics
Astronomy
25
Stars: Circumstellar Matter, Ism: Clouds, Ism: Individual: Ngc Number: Ngc 7538, Stars: Formation, Stars: Pre-Main-Sequence, Submillimeter
Scientific paper
We present high-resolution millimeter and submillimeter maps (1.3 mm and 850, 800, 450, and 350 μm) of the molecular cloud southeast of NGC 7538, obtained on the IRAM 30 m telescope at Pico Veleta, Spain and the 15 m James Clerk Maxwell Telescope on Mauna Kea, Hawaii. These maps show filamentary dust ridges extending from and connecting to the three major activity centers (IRS 1-3, NGC 7538 S, and IRS 9) in this high-mass star-forming cloud. In addition to the three already known star formation centers, we also find a fainter extended submillimeter source near the 20 μm source IRS 4, at the boundary of the optical H II region. Our high spatial resolution images resolve the young, hypercompact H II region IRS 1 and show that it coincides with a compact (<10") elliptical dust source with a mass of >=70 Msolar. It is surrounded by a cluster of submillimeter sources, none of which have near- or mid-IR counterparts. Three of the submillimeter sources are associated with H2O masers, suggesting that protostars or young stars have formed in these cloud cores. We find IRS 9 to be an extended elliptical source with a size of 13''×6'' at a position angle of -80°, with a second, fainter but more extended source about 20" south of it. The mass of the IRS 9 submillimeter source is ~150 Msolar, while the southern source has a mass of ~90 Msolar. The third activity center, NGC 7538 S, is ~80" south of IRS 1. Here we find a strong, elliptical submillimeter source of 12''×7'', with a position angle of 58°. This source coincides with OH and H2O masers and a faint VLA 6 cm source, but it shows no near- or mid-infrared emission. We find NGC 7538 S to have all the characteristics of a Class 0 source; i.e., it is a high-mass protostar. It is cold, Td~35 K, has a disklike geometry, drives a very young outflow, and is extremely massive, M~400 Msolar. Yet it has a luminosity of only 104 Lsolar.
Sandell Göran
Sievers Albrecht
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