THE INITIAL CONDITIONS OF CLUSTERED STAR FORMATION. II. N{sub 2}H{sup +} OBSERVATIONS OF THE OPHIUCHUS B CORE

Journal Article · Sun Jan 10 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/708/2/1002· OSTI ID:21392429

Friesen, R K; Di Francesco, J ^[1]; Shimajiri, Y ^[2]; Takakuwa, S ^[3]

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1. Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, STN CSC, Victoria, BC V8W 3P6 (Canada)
2. Department of Astronomy, School of Science, University of Tokyo, Bunkyo, Tokyo 113-0033 (Japan)
3. Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China)

We present a Nobeyama 45 m Radio Telescope map and Australia Telescope Compact Array pointed observations of N{sub 2}H{sup +} 1-0 emission toward the clustered, low-mass star-forming Oph B Core within the Ophiuchus molecular cloud. We compare these data with previously published results of high-resolution NH{sub 3} (1,1) and (2,2) observations in Oph B. We use 3D CLUMPFIND to identify emission features in the single-dish N{sub 2}H{sup +} map, and find that the N{sub 2}H{sup +} 'clumps' match well similar features previously identified in NH{sub 3} (1,1) emission, but are frequently offset to clumps identified at similar resolution in 850 mum continuum emission. Wide line widths in the Oph B2 sub-Core indicate that non-thermal motions dominate the Core kinematics, and remain transonic at densities n approx 3 x 10{sup 5} cm{sup -3} with large scatter and no trend with N(H{sub 2}). In contrast, non-thermal motions in Oph B1 and B3 are subsonic with little variation, but also show no trend with H{sub 2} column density. Over all of Oph B, non-thermal N{sub 2}H{sup +} line widths are substantially narrower than those traced by NH{sub 3}, making it unlikely NH{sub 3} and N{sub 2}H{sup +} trace the same material, but the v{sub LSR} of both species agree well. We find evidence for accretion in Oph B1 from the surrounding ambient gas. The NH{sub 3}/N{sub 2}H{sup +} abundance ratio is larger toward starless Oph B1 than toward protostellar Oph B2, similar to recent observational results in other star-forming regions. The interferometer observations reveal small-scale structure in N{sub 2}H{sup +} 1-0 emission, which are again offset from continuum emission. No interferometric N{sub 2}H{sup +} emission peaks were found to be coincident with continuum clumps. In particular, the approx1 M{sub sun} B2-MM8 clump is associated with an N{sub 2}H{sup +} emission minimum and surrounded by a broken ring-like N{sub 2}H{sup +} emission structure, suggestive of N{sub 2}H{sup +} depletion. We find a strong general trend of decreasing N{sub 2}H{sup +} abundance with increasing N(H{sub 2}) in Oph B which matches that found for NH{sub 3}.

• OSTI ID: 21392429
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 708; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
AMMONIA
ANTENNAS
ELECTRICAL EQUIPMENT
ELECTRONIC EQUIPMENT
ELEMENTS
EMISSION
EQUIPMENT
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
INTERFEROMETERS
LINE WIDTHS
MAPS
MEASURING INSTRUMENTS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
RADIO EQUIPMENT
RADIO TELESCOPES
STARS
TELESCOPES