Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21535403e&link_type=abstract
American Astronomical Society, AAS Meeting #215, #354.03; Bulletin of the American Astronomical Society, Vol. 42, p.537
Astronomy and Astrophysics
Astronomy
Scientific paper
We present sensitive and high angular resolution CO(1-0) data obtained by CARMA observations toward the nearby grand-design spiral galaxy M51. From the data, Giant Molecular Associations (GMAs) in a spiral arm are found to be resolved into a few small clumps with mass of 106 Msun and size of 40 pc. As the densities of these clumps are estimated to be larger than 300 cm-3, we regard them as dense cores of GMAs. If GMAs were just confusion of Giant Molecular Clouds (GMCs) whose typical mass and size are almost the same as those of the detected clumps, we should have detected tens or more of them per each GMA considering the sensitivity of our data. However, only one or two cores are found in each GMA, indicating that GMAs are not ensembles of GMCs but are discrete smooth structures. This result is consistent with the conclusion by Koda et al. (2009), who worked on lower resolution CO data of M51.
In addition, we have found that these cores are located downstream of the spiral arm. This suggests that the core formation of GMAs and their evolution are triggered by the spiral structure, or density waves. Our high resolution data reveal the inner structure of GMAs and its relationships to the global structure for the first time in grand-design spiral galaxies.
Egusa Fumi
Koda Jin
Scoville Nicholas Z.
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