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Title: The dynamical state of the Serpens South filamentary infrared dark cloud

We present the results of N{sub 2}H{sup +} (J = 1-0) observations toward Serpens South, the nearest cluster-forming, infrared dark cloud. The physical quantities are derived by fitting the hyperfine structure of N{sub 2}H{sup +}. The Herschel and 1.1 mm continuum maps show that a parsec-scale filament fragments into three clumps with radii of 0.1-0.2 pc and masses of 40-230 M {sub ☉}. We find that the clumps contain smaller-scale (∼0.04 pc) structures, i.e., dense cores. We identify 70 cores by applying CLUMPFIND to the N{sub 2}H{sup +} data cube. In the central cluster-forming clump, the excitation temperature and line-width tend to be large, presumably due to protostellar outflow feedback and stellar radiation. However, for all the clumps, the virial ratios are evaluated to be 0.1-0.3, indicating that the internal motions play only a minor role in the clump support. The clumps exhibit no free fall but exhibit low-velocity infall, and thus the clumps should be supported by additional forces. The most promising force is the globally ordered magnetic field observed toward this region. We propose that the Serpens South filament was close to magnetically critical and ambipolar diffusion triggered the cluster formation. We find that the northern clump, whichmore » shows no active star formation, has a mass and radius comparable to the central cluster-forming clump and is therefore a likely candidate of a pre-protocluster clump. The initial condition for cluster formation is likely to be a magnetically supported clump of cold, quiescent gas. This appears to contradict the accretion-driven turbulence scenario, for which the turbulence in the clumps is maintained by the accretion flow.« less
Authors:
; ;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Physical Science, Osaka Prefecture University, Gakuen 1-1, Sakai, Osaka 599-8531 (Japan)
  2. National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)
  3. Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1805 (Japan)
  4. Graduate School of Natural Sciences, Nagoya City University, Mizuho-ku, Nagoya 467-8501 (Japan)
  5. Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States)
  6. Joint ALMA Observatory, Alonso de Cordova 3107 OFC 129, Vitacura (Chile)
Publication Date:
OSTI Identifier:
22342029
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMBIPOLAR DIFFUSION; COMPARATIVE EVALUATIONS; EXCITATION; FEEDBACK; FILAMENTS; HYPERFINE STRUCTURE; LINE WIDTHS; MAGNETIC FIELDS; MASS; STAR CLUSTERS; STARS; STELLAR RADIATION; TURBULENCE; VELOCITY