Physical Conditions in the ISM and Star Formation in Nearby Galaxies

Date: 
Wednesday, November 16, 2016 - 3:30pm PST
Speaker: 
Adam Leroy
Affiliation: 
Ohio State University
Location: 
N232, room 103
Event Type: 
Colloquium

I will present results from several new projects using ALMA, the IRAM mm-wave telescopes, and soon the Green Bank Telescope to map physical conditions in the molecular gas of nearby galaxies. Using multi-line spectroscopy we are able to constrain the gas density distribution in each part of the galaxy, while using high resolution CO imaging we can measure the structure (density, turbulence, and self-gravity) of the interstellar medium on the scale of individual star-forming clouds. The ability to make such measurements over a large part of a star forming galaxy is new in the last few years, thanks to the IRAM programs EMPIRE and PAWS, the beginning of ALMA operations, and upgrades to the GBT. I will show how the amount of dense gas changes across the disk of galaxies, and illustrate a more nuanced role for gas density in star formation than commonly asserted. I will also show how the basic cloud-scale structure of the cold interstellar medium changes from galaxy-to-galaxy, reflecting the local environment, and I will show how these local structural conditions relate to gas density and star formation in the best studied nearby galaxies. Finally, I will highlight first results several new surveys with ALMA (the "SFNG" collaboration) that promise to give us a new view of cold gas in nearby galaxies over the next years.

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