FOUR HIGHLY LUMINOUS MASSIVE STAR-FORMING REGIONS IN THE NORMA SPIRAL ARM. I. MOLECULAR GAS AND DUST OBSERVATIONS

Journal Article · Wed Feb 10 00:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/710/1/567· OSTI ID:21394491

Garay, Guido; Mardones, Diego; Bronfman, Leonardo; May, Jorge; Chavarria, Luis ^[1]; Nyman, Lars-Ake ^[2]

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1. Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Las Condes, Santiago (Chile)
2. European Southern Observatory, Casilla 19001, Santiago (Chile)

We report molecular line and dust continuum observations, made with the Swedish-ESO Submillimeter Telescope, toward four young high-mass star-forming regions associated with highly luminous (L>6x10{sup 5}L{sub odot}) Infrared Astronomical Satellite sources (15290-5546, 15502-5302, 15567-5236, and 16060-5146). Molecular emission was mapped in three lines of CS (J = 2 -> 1, 3 -> 2, and 5 -> 4), two lines of SiO (J = 2 -> 1 and 3 -> 2), two rotational transitions of CH{sub 3}OH (J{sub k} = 3{sub k} -> 2{sub k} and 2{sub k} -> 1{sub k}), and in the C{sup 34}S(J = 3 -> 2) line. In addition, single spectra at the peak position were taken in the CO(J = 1 -> 0), {sup 13}CO(J = 1 -> 0), and C{sup 18}O(J = 1 -> 0) lines. We find that the luminous star-forming regions are associated with molecular gas and dust structures with radii of typically 0.5 pc, masses of {approx}5 x 10{sup 3} M{sub sun}, column densities of {approx}5 x 10{sup 23} cm{sup -2}, molecular hydrogen densities of typically {approx}2 x 10{sup 5} cm{sup -3}, and dust temperatures of {approx}40 K. The 1.2 mm dust continuum observations further indicate that the cores are centrally condensed, having radial density profiles with power-law indices in the range 1.9-2.3. We find that under these conditions dynamical friction by the gas plays an important role in the migration of high-mass stars toward the central core region, providing an explanation for the observed stellar mass segregation within the cores. The CS profiles show two distinct emission components: a bright component, with line widths of typically 5 km s{sup -1} (FWHM), and a weaker and wider velocity component, which typically extends up to +-13 km s{sup -1} from the ambient cloud velocity. The SiO profiles also show emission from both components, but the intensity of the pedestal feature relative to that of the bright component is stronger than for CS. The narrow SiO component is likely to trace warm ambient gas close to the recently formed massive stars, whereas the high velocity emission indicates mass outflows produced by either the expansion of the H II regions, stellar winds, and/or collimated outflows. We find that the abundances of CS, CH{sub 3}OH, and SiO, relative to H{sub 2}, in the warm ambient gas of the massive cores are typically 4 x 10{sup -8}, 6 x 10{sup -9}, and 5 x 10{sup -11}, respectively.

• OSTI ID: 21394491
• Journal Information: Astrophysical Journal, Vol. 710, Issue 1; Other Information: DOI: 10.1088/0004-637X/710/1/567; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
DENSITY
DUSTS
EMISSION
HYDROGEN
LINE WIDTHS
MASS
METHANOL
SATELLITES
SILICON OXIDES
SPECTRA
STARS
STELLAR WINDS
TELESCOPES
ALCOHOLS
CHALCOGENIDES
ELEMENTS
HYDROXY COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICON COMPOUNDS
STELLAR ACTIVITY