FORMATION OF AN O-STAR CLUSTER BY HIERARCHICAL ACCRETION IN G20.08-0.14 N

Journal Article · Tue Dec 01 00:00:00 EST 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/706/2/1036· OSTI ID:21378118

Galvan-Madrid, Roberto; Keto, Eric; Qizhou, Zhang; Ho, Paul T. P. ^[1]; Kurtz, Stan

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

Spectral line and continuum observations of the ionized and molecular gas in G20.08-0.14 N explore the dynamics of accretion over a range of spatial scales in this massive star-forming region. Very Large Array (VLA) observations of NH{sub 3} at 4'' angular resolution show a large-scale (0.5 pc) molecular accretion flow around and into a star cluster with three small, bright H II regions. Higher resolution (0.''4) observations with the Submillimeter Array in hot core molecules (CH{sub 3}CN, OCS, and SO{sub 2}) and the VLA in NH{sub 3} show that the two brightest and smallest H II regions are themselves surrounded by smaller scale (0.05 pc) accretion flows. The axes of rotation of the large- and small-scale flows are aligned, and the timescale for the contraction of the cloud is short enough, 0.1 Myr, for the large-scale accretion flow to deliver significant mass to the smaller scales within the star formation timescale. The flow structure appears to be continuous and hierarchical from larger to smaller scales. Millimeter radio recombination line (RRL) observations at 0.''4 angular resolution indicate rotation and outflow of the ionized gas within the brightest H II region (A). The broad recombination lines and a continuum spectral energy distribution (SED) that rises continuously from cm to mm wavelengths, are both characteristic of the class of H II regions known as 'broad recombination line objects'. The SED indicates a density gradient inside this H II region, and the RRLs suggest supersonic flows. These observations are consistent with photoevaporation of the inner part of the rotationally flattened molecular accretion flow. We also report the serendipitous detection of a new NH{sub 3} (3,3) maser.

• OSTI ID: 21378118
• Journal Information: Astrophysical Journal, Vol. 706, Issue 2; Other Information: DOI: 10.1088/0004-637X/706/2/1036; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ACETONITRILE
AMMONIA
ENERGY SPECTRA
MASERS
RECOMBINATION
ROTATION
STAR CLUSTERS
STARS
SULFUR DIOXIDE
SUPERSONIC FLOW
AMPLIFIERS
CHALCOGENIDES
ELECTRONIC EQUIPMENT
EQUIPMENT
FLUID FLOW
HYDRIDES
HYDROGEN COMPOUNDS
MICROWAVE AMPLIFIERS
MICROWAVE EQUIPMENT
MOTION
NITRILES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SPECTRA
SULFUR COMPOUNDS
SULFUR OXIDES