INITIAL CONDITIONS FOR STAR FORMATION IN CLUSTERS: PHYSICAL AND KINEMATICAL STRUCTURE OF THE STARLESS CORE Oph A-N6

Journal Article · Wed Feb 01 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/745/2/117· OSTI ID:22011920

Bourke, Tyler L; Myers, Philip C; Wilner, David J ^[1]; Caselli, Paola ^[2]; Di Francesco, James ^[3]; Belloche, Arnaud ^[4]; Plume, Rene ^[5]

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1. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
2. School of Physics and Astronomy, E.C. Stoner Building, University of Leeds, Leeds LS2 9JT (United Kingdom)
3. National Research Council Canada, Herzberg Institute of Astrophysics, Victoria, BC (Canada)
4. Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)
5. Department of Physics and Astronomy, University of Calgary, Calgary, AB (Canada)

We present high spatial (<300 AU) and spectral (0.07 km s{sup -1}) resolution Submillimeter Array observations of the dense starless cluster core Oph A-N6 in the 1 mm dust continuum and the 3-2 line of N{sub 2}H{sup +} and N{sub 2}D{sup +}. The dust continuum observations reveal a compact source not seen in single-dish observations, of size {approx}1000 AU and mass 0.005-0.01 M{sub Sun }. The combined line and single-dish observations reveal a core of size 3000 Multiplication-Sign 1400 AU elongated in a NW-SE direction, with almost no variation in either line width nor line center velocity across the map, and very small non-thermal motions. The deuterium fraction has a peak value of {approx}0.15 and is >0.05 over much of the core. The N{sub 2}H{sup +} column density profile across the major axis of Oph A-N6 is well represented by an isothermal cylinder, with temperature 20 K, peak density 7.1 Multiplication-Sign 10{sup 6} cm{sup -3}, and N{sub 2}H{sup +} abundance 2.7 Multiplication-Sign 10{sup -10}. The mass of Oph A-N6 is estimated to be 0.29 M{sub Sun }, compared to a value of 0.18 M{sub Sun} from the isothermal cylinder analysis, and 0.63 M{sub Sun} for the critical mass for fragmentation of an isothermal cylinder. Compared to isolated low-mass cores, Oph A-N6 shows similar narrow line widths and small velocity variation, with a deuterium fraction similar to 'evolved' dense cores. It is significantly smaller than isolated cores, with larger peak column and volume density. The available evidence suggests that Oph A-N6 has formed through the fragmentation of the Oph A filament and is the precursor to a low-mass star. The dust continuum emission suggests that it may already have begun to form a star.

• OSTI ID: 22011920
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 745; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
CRITICAL MASS
DEUTERIUM
DUSTS
STARS