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Molecular gas evolution across a spiral arm in M51

Egusa, Fumi and Koda, Jin and Scoville, Nick (2011) Molecular gas evolution across a spiral arm in M51. Astrophysical Journal, 726 (2). Art. No. 85. ISSN 0004-637X. https://resolver.caltech.edu/CaltechAUTHORS:20110201-093820842

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Abstract

We present sensitive and high angular resolution CO(1–0) data obtained by the Combined Array for Research in Millimeter-wave Astronomy observations toward the nearby grand-design spiral galaxy M51. The angular resolution of 0".7 corresponds to 30 pc, which is similar to the typical size of giant molecular clouds (GMCs), and the sensitivity is also high enough to detect typical GMCs. Within the 1' field of view centered on a spiral arm, a number of GMC-scale structures are detected as clumps. However, only a few clumps are found to be associated with each giant molecular association (GMA) and more than 90% of the total flux is resolved out in our data. Considering the high sensitivity and resolution of our data, these results indicate that GMAs are not mere confusion with GMCs but plausibly smooth structures. In addition, we have found that the most massive clumps are located downstream of the spiral arm, which suggests that they are at a later stage of molecular cloud evolution across the arm and plausibly are cores of GMAs. By comparing with Hα and Paα images, most of these cores are found to have nearby star-forming regions. We thus propose an evolutionary scenario for the interstellar medium, in which smaller molecular clouds collide to form smooth GMAs at spiral arm regions and then star formation is triggered in the GMA cores. Our new CO data have revealed the internal structure of GMAs at GMC scales, finding the most massive substructures on the downstream side of the arm in close association with the brightest H II regions.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1088/0004-637X/726/2/85DOIArticle
http://iopscience.iop.org/0004-637X/726/2/85/PublisherArticle
ORCID:
AuthorORCID
Koda, Jin0000-0002-8762-7863
Scoville, Nick0000-0002-0438-3323
Additional Information:© 2011 The American Astronomical Society. Received 2010 July 7; accepted 2010 November 10; published 2010 December 17. We are grateful to E. Schinnerer who kindly provided us a draft of her paper prior to publication. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a We are grateful to E. Schinnerer who kindly provided us a draft of her paper prior to publication. Support for CARMA construction was derived from the states of California, Illinois, and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology, and the National Science Foundation. Ongoing CARMA development and operations are supported by the National Science Foundation under a cooperative agreement and by the CARMA partner universities. This research is partially supported by HST-AR-11261.01. Facility: CARMA
Funders:
Funding AgencyGrant Number
Hubble Space Telescope (HST)HST-AR-11261.01
Subject Keywords:galaxies: individual (M51 or NGC 5194) – galaxies: spiral – ISM: clouds – ISM: molecules
Issue or Number:2
Classification Code:PACS: 98.62.Hr; 98.58.Hf; 98.52.Nr; 98.58.Db; 95.85.Bh
Record Number:CaltechAUTHORS:20110201-093820842
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20110201-093820842
Official Citation:Fumi Egusa et al. 2011 ApJ 726 85 doi: 10.1088/0004-637X/726/2/85
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21946
Collection:CaltechAUTHORS
Deposited By: Benjamin Perez
Deposited On:01 Feb 2011 19:03
Last Modified:03 Oct 2019 02:31

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