Date: Monday 4-Nov-2013
Speaker: Vianney Taquet (NPP Fellow at GSFC)
Title: Chemical evolution at the early stages of low-mass star formation: deuterium fractionation and chemical complexity
No abstract available.
Date: Monday 9-Dec-2013
Speaker: Marissa Rosenberg (Leiden U)
Title: CO Excitation in Luminous Infrared Galaxies
(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. CO transitions from J=4-3 to 13-12 are observed and together, these lines trace the excitation of CO. By studying the CO excitation ladder and comparing the CO intensities to models, we can determine whether the gas is excited by UV radiation, Xrays, or mechanical heating as well as the density and strength of the radiation field. However the models suffer from degeneracies. In order to understand the nature of the model degeneracies, we perform a chi^2 minimized fit of the CO excitation ladder of distinct, well studied starburst galaxies and map the chi^2 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.
