From dusty filaments to massive stars: The case of NGC 7538 S

Abstract

We report on high-sensitivity and high-angular resolution archival Submillimeter Array (SMA) observations of the large ($\sim$15000 AU) putative circumstellar disk associated with the O-type protostar NGC 7538 S. Observations of the continuum resolve this putative circumstellar disk into five compact sources, with sizes $\sim$ 3000 AU and masses $\sim 10M_{\odot }$. This confirm the results of recent millimeter observations made with CARMA/BIMA towards this object. However, we find that from most of these compact sources eject collimated bipolar outflows, revealed by our silicon monoxide (SiO {\it J}=5-4) observations and confirm that these sources have a (proto)stellar nature. All outflows are perpendicular to the large and rotating dusty structure. We propose therefore that, rather than being a single massive circumstellar disk, NGC 7538 S could be instead a large and massive contracting or rotating filament that is fragmenting at scales of 0.1 to 0.01 pc to form several B-type stars, via the standard process involving outflows and disks. As in recent high spatial resolution studies of dusty filaments, our observations also suggest that thermal pressure does not seem to be sufficient to support the filament, so that either additional support needs to be invoked, or else the filament must be in the process of collapsing. An SPH numerical simulation of the formation of a molecular cloud by converging warm neutral medium flows produces contracting filaments whose dimensions and spacings between the stars forming within them, as well as their column densities, strongly resemble those observed in the filament reported here.

submitted to ApJL

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Cited by in corpus (13)

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• ALMA reveals a candidate hot and compact disk around the O-type protostar IRAS 16547$-$4247
• The stellar contents and star formation in the NGC 7538 region
• ALMA Observations of Massive Clouds in the Central Molecular Zone: Ubiquitous Protostellar Outflows
• Magnetized converging flows towards the hot core in the intermediate/high-mass star-forming region NGC 6334 V
• Earliest Stages of Protocluster Formation: Substructure and Kinematics of Starless Cores in Orion
• Inferring the evolutionary stages of the internal structures of NGC 7538 S and IRS1 from chemistry
• Uniform Silicon Isotope Ratios Across the Milky Way Galaxy
• IRAS 19520+2759: a 10^5 Lsun massive young stellar object driving a collimated outflow
• Extremely Energetic Outflow and Decelerated Expansion in W49N