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Astrophysics Luncheon Seminar

Radiative and Mechanical Feedback in Starburst Galaxies
Presented by M.J.F. Rosenberg
Leiden Observatory

Monday, December 16, 2013
12:00 noon in 169-336

(Ultra) Luminous Infrared Galaxies ((U)LIRGs) are galaxies exhibiting an extremely high infrared luminosity and may be the evolutionary transition phase between starburst galaxies and QSOs. Understanding the heating and cooling mechanisms in these galaxies can give us insight to the driving mechanisms that fuel this transition. Molecular emission lines play a crucial role in the cooling of excited gas, and recently with Herschel Space Observatory we are able to observe the rich molecular spectrum. Carbon monoxide (CO) is the most abundant and one of the brightest molecules in the Herschel wavelength range. 12CO and 13CO transitions are observed along with ancillary data and together, these lines trace the excitation of the molecular gas. By studying the CO excitation ladders in NGC 253 and Arp299 and comparing the CO intensities to models, we can determine whether the gas is excited by UV radiation, Xrays, cosmic rays, or mechanical (turbulent) heating as well as the density and strength of the radiation field in these two galaxies. However the models suffer from degeneracies. In order to understand the nature of the model degeneracies, we perform a χ2 minimized fit of the CO excitation ladder of distinct, well studied starburst galaxies and map the χ2 values for every possible combination of models. Then by adding ancillary data, we are able to constrain these degeneracies and understand through which mechanisms the molecular gas is being excited.

JPL Contact: Thangasamy Velusamy (4-6112)

SVCP Astrophysics

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