The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251

Jared Keown, James Di Francesco, Helen Kirk, Rachel K. Friesen, Jaime E. Pineda, Erik Rosolowsky, Adam Ginsburg, Stella S.R. Offner, Paola Caselli, Felipe Alves, Ana Chacón-Tanarro, Anna Punanova, Elena Redaelli, Young Min Seo, Christopher D. Matzner, Michael Chun Yuan Chen, Alyssa A. Goodman, How Huan Chen, Yancy L Shirley, Ayushi SinghHector G. Arce, Peter Martin, Philip C. Myers

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5 Scopus citations

Abstract

We use Green Bank Ammonia Survey observations of NH3 (1, 1) and (2, 2) emission with 32″ FWHM resolution from a ∼10 pc2 portion of the Cepheus-L1251 molecular cloud to identify hierarchical dense gas structures. Our dendrogram analysis of the NH3 data results in 22 top-level structures, which reside within 13 lower-level parent structures. The structures are compact and are spatially correlated with the highest H2 column density portions of the cloud. We also compare the ammonia data to a catalog of dense cores identified by higher-resolution (18.″2 FWHM) Herschel Space Observatory observations of dust continuum emission from Cepheus-L1251. Maps of kinetic gas temperature, velocity dispersion, and NH3 column density, derived from detailed modeling of the NH3 data, are used to investigate the stability and chemistry of the ammonia-identified and Herschel-identified structures. We show that the dust and dense gas in the structures have similar temperatures, with median T dust and T K measurements of 11.7 ± 1.1 K and 10.3 ± 2.0 K, respectively. Based on a virial analysis, we find that the ammonia-identified structures are gravitationally dominated, yet may be in or near a state of virial equilibrium. Meanwhile, the majority of the Herschel-identified dense cores appear to be not bound by their own gravity and instead confined by external pressure. CCS (20-10) and HC5N emission from the region reveal broader line widths and centroid velocity offsets when compared to the NH3 (1, 1) emission in some cases, likely due to these carbon-based molecules tracing the turbulent outer layers of the dense cores.

Original languageEnglish (US)
Article number3
JournalAstrophysical Journal
Volume850
Issue number1
DOIs
StatePublished - Nov 20 2017

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Keywords

  • ISM
  • ISM
  • kinematics and dynamics
  • stars: formation
  • structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Keown, J., Di Francesco, J., Kirk, H., Friesen, R. K., Pineda, J. E., Rosolowsky, E., Ginsburg, A., Offner, S. S. R., Caselli, P., Alves, F., Chacón-Tanarro, A., Punanova, A., Redaelli, E., Seo, Y. M., Matzner, C. D., Chen, M. C. Y., Goodman, A. A., Chen, H. H., Shirley, Y. L., ... Myers, P. C. (2017). The Green Bank Ammonia Survey: Observations of Hierarchical Dense Gas Structures in Cepheus-L1251. Astrophysical Journal, 850(1), [3]. https://doi.org/10.3847/1538-4357/aa93ec