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  Droplets. I. Pressure-dominated coherent structures in L1688 and B18

Chen, H.-H.-H., Pineda, J. E., Goodman, A. A., Burkert, A., Offner, S. S. R., Friesen, R. K., et al. (2019). Droplets. I. Pressure-dominated coherent structures in L1688 and B18. The Astrophysical Journal, 877(2): 93. doi:10.3847/1538-4357/ab1a40.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0003-D934-E Version Permalink: http://hdl.handle.net/21.11116/0000-0003-D935-D
Genre: Journal Article

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 Creators:
Chen, Hope How-Huan, Author
Pineda, Jaime E.1, Author              
Goodman, Alyssa A., Author
Burkert, Andreas, Author
Offner, Stella S. R., Author
Friesen, Rachel K., Author
Myers, Philip C., Author
Alves, Felipe1, Author              
Arce, Héctor G., Author
Caselli, Paola1, Author              
Chacón-Tanarro, Ana1, Author              
Chen, Michael Chun-Yuan, Author
Francesco, James Di, Author
Ginsburg, Adam, Author
Keown, Jared, Author
Kirk, Helen, Author
Martin, Peter G., Author
Matzner, Christopher, Author
Punanova, Anna, Author
Redaelli, Elena1, Author              
Rosolowsky, Erik, AuthorScibelli, Samantha, AuthorSeo, Youngmin, AuthorShirley, Yancy, AuthorSingh, Ayushi, Author more..
Affiliations:
1Center for Astrochemical Studies at MPE, MPI for Extraterrestrial Physics, Max Planck Society, ou_1950287              

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 Abstract: We present the observation and analysis of newly discovered coherent structures in the L1688 region of Ophiuchus and the B18 region of Taurus. Using data from the Green Bank Ammonia Survey, we identify regions of high density and near-constant, almost-thermal velocity dispersion. We reveal 18 coherent structures are revealed, 12 in L1688 and 6 in B18, each of which shows a sharp "transition to coherence" in velocity dispersion around its periphery. The identification of these structures provides a chance to statistically study the coherent structures in molecular clouds. The identified coherent structures have a typical radius of 0.04 pc and a typical mass of 0.4 M, generally smaller than previously known coherent cores identified by Goodman et al., Caselli et al., and Pineda et al. We call these structures "droplets." We find that, unlike previously known coherent cores, these structures are not virially bound by self-gravity and are instead predominantly confined by ambient pressure. The droplets have density profiles shallower than a critical Bonnor–Ebert sphere, and they have a velocity (V LSR) distribution consistent with the dense gas motions traced by NH3 emission. These results point to a potential formation mechanism through pressure compression and turbulent processes in the dense gas. We present a comparison with a magnetohydrodynamic simulation of a star-forming region, and we speculate on the relationship of droplets with larger, gravitationally bound coherent cores, as well as on the role that droplets and other coherent structures play in the star formation process.

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 Dates: 2019-05-29
 Publication Status: Published online
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 Identifiers: DOI: 10.3847/1538-4357/ab1a40
Other: LOCALID: 3072988
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Title: The Astrophysical Journal
Source Genre: Journal
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Publ. Info: Bristol, England : IOP Publishing LTD
Pages: - Volume / Issue: 877 (2) Sequence Number: 93 Start / End Page: - Identifier: ISSN: 1538-4357
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215_3