An ammonia spectral map of the L1495-B218 filaments in the Taurus molecular cloud. i. physical properties of filaments and dense cores

Young Min Seo, Yancy L Shirley, Paul Goldsmith, Derek Ward-Thompson, Jason M. Kirk, Markus Schmalzl, Jeong Eun Lee, Rachel Friesen, Glen Langston, Joe Masters, Robert W. Garwood

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Abstract

We present deep NH<inf>3</inf> observations of the L1495-B218 filaments in the Taurus molecular cloud covering over a 3° angular range using the K-band focal plane array on the 100 m Green Bank Telescope. The L1495-B218 filaments form an interconnected, nearby, large complex extending over 8 pc. We observed NH<inf>3</inf> (1, 1) and (2, 2) with a spectral resolution of 0.038 km s<sup>-1</sup> and a spatial resolution of 31″. Most of the ammonia peaks coincide with intensity peaks in dust continuum maps at 350 and 500 μm. We deduced physical properties by fitting a model to the observed spectra. We find gas kinetic temperatures of 8-15 K, velocity dispersions of 0.05-0.25 km s<sup>-1</sup>, and NH<inf>3</inf> column densities of 5 × 10<sup>12</sup> to 1 × 10<sup>14</sup> cm<sup>-2</sup>. The CSAR algorithm, which is a hybrid of seeded-watershed and binary dendrogram algorithms, identifies a total of 55 NH<inf>3</inf> structures, including 39 leaves and 16 branches. The masses of the NH<inf>3</inf> sources range from 0.05 to 9.5 MO. The masses of NH<inf>3</inf> leaves are mostly smaller than their corresponding virial mass estimated from their internal and gravitational energies, which suggests that these leaves are gravitationally unbound structures. Nine out of 39 NH<inf>3</inf> leaves are gravitationally bound, and seven out of nine gravitationally bound NH<inf>3</inf> leaves are associated with star formation. We also found that 12 out of 30 gravitationally unbound leaves are pressure confined. Our data suggest that a dense core may form as a pressure-confined structure, evolve to a gravitationally bound core, and undergo collapse to form a protostar.

Original languageEnglish (US)
Article number185
JournalAstrophysical Journal
Volume805
Issue number2
DOIs
Publication statusPublished - Jun 1 2015

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Keywords

  • ISM: clouds
  • ISM: molecules
  • radio lines: ISM
  • stars: formation

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

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