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Monday, June 15 at 2.00pm at the JAC
Stefanie Muehle
Joint Institutue for VLBI in Europe (JIVE)
"Molecular gas is cool ... or is it?
The Properties of Molecular Gas in Active Galaxies"
ABSTRACT:
There is growing evidence that the properties of the molecular gas in the
nuclei of starburst galaxies and near AGN may be very different from those
seen in Galactic star forming regions. Unfortunately, among the
fundamental parameters derived from molecular line observations, the
kinetic temperature of the molecular gas in external galaxies is often not
well determined. In this talk, I will demonstrate the diagnostic power of
selected formaldehyde (H_2CO) lines in deriving the properties of
extragalactic molecular gas. I will show new H_2CO spectra and maps of
nearby starburst galaxies and AGN and compare our findings with results
from the literature. In particular, I will discuss the results of our
multi-transition line study of the para-H_2CO emission from the
prototypical starburst galaxy M82. Using our non-LTE radiative transfer
model, we tightly constrained the physical properties of the molecular gas
in the prominent molecular lobes, completely independent of the standard
"cloud thermometer" NH_3 or other molecular tracers. Our results agree
very well with the properties of the high-excitation molecular gas
component found in the most comprehensive CO studies. In addition, the
observations also indicate the presence of methanol in at least one of the
molecular lobes.
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