Time & Location

Physics seminars during the academic year are held on Tuesdays at 2:50pm in OPB 234 - 237.

Special seminars, M.S. thesis, and Ph.D. dissertation talks are held at the time and location given in the announcement below.

Coffee and cookies will be served 15 minutes prior to talks.


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Spring 2018 Talks

Tuesday, 23 January 2018

Dense Molecular Gas and Star Formation in Nearby Galaxy M51

Speaker: Dr. Hao Chen (UAH Physics & Astronomy)
Location: OPB 234, 2:50pm
Abstract: Stars form in the dense cores of giant molecular clouds (GMCs). The dense cores are traced by high-dipole-moment molecules such as HCN and HCO+. The star formation rate (SFR, traced by infrared luminosity) and dense molecular gas mass (traced by HCN luminosity) show linear correlation in global galaxies. It is a front topic in astrophysics that how does the dense gas form stars in galactic disk. We mapped dense molecular gas (traced by HCN 1-0 emission) across the disk of M51 with IRAM 30m telescope and find that the star formation efficiency of dense gas (IR to HCN luminosity ratio) is lower in the center than in the outer disk. This could be caused by the stronger turbulence in the center which could prevent the formation of stars from dense gas. We also detected dense gas (traced by HCN 1-0 and HCO+ 1-0) in 6 giant molecular associations (GMAs, ~100pc) with NOEMA telescope in the spiral arms of M51. Comparing with multi-scale targets (global galaxies, 1 kpc scale regions in the disk of nearby galaxies, giant molecular associations and dense molecular cloud cores in the Milky Way), we confirm that the linear relation between IR and HCN luminosity extend to the spatial scale of 100 pc.

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