Astronomy and Astrophysics Seminars

ALMA reveals molecular cloud N55 in the Large Magellanic Cloud as a site of massive star formation

by Dr. Naslim Neelamkodan (ALMA Regional Center, NAOJ, Japan)

Friday, March 24, 2017 from to (Asia/Kolkata)
at DAA ( A269 )
TIFR
Description
The star-forming region, N55, in the Large Magellanic Cloud galaxy is
observed with Atacama Large Millimeter Array (ALMA) in band 3 and band 6
receivers, at spectral windows centered at 12CO(1-0), 13CO(1-0),
12CO(2-1) and 13CO(2-1). We examine the molecular clump properties
such as size, velocity dispersion, mass, and their association to star
formation. This region is less extreme than the well studied 30Doradus
or N159 environments. We choose this cloud based on our infrared
spectroscopic and photometric observations with Spitzer and Hershel
space telescopes. With infrared spectrograph on Spitzer, we have
detected the H2 rotational transitions at 28.2 and 17.1 micron in
N55. The clumpy and filamentary structures of H2 emission in N55
spatially resemble the distribution of polycyclic aromatic hydrocarbon
(PAH) emission traced by Spitzer InfraRed Array Camera (IRAC)
8.0 micron as well as the dust emission traced by Herschel
Photodetector Array Camera and Spectrometer (PACS) 100 micron. Our goal
is to determine how (dis-)similar the N55 clumps are from Milky Way
clouds and 30Doradus. We find that massive clumps are associated with
high and intermediate-mass YSOs. The size-linewidth relation of N55
shows a similar trend as in many Milky Way quiescent clouds. The trend
shows a power law relation with the index of 0.5+/-0.05. This result
suggests that N55 clouds are gravitationally bound and the effect of
any external pressure may be negligible. We derive a CO-to-H2 conversion
factor, Xco, twice the value of Galactic Clouds.  The clump mass
function in N55 shows a similar trend as that found in Milky Way
clouds and 30Doradus in the LMC. Our studies show that the mass
spectrum index is not dependent on the environments sampled.  This
study confirms a universal behavior of the clump mass function at
smaller spatial scales in a sub-solar metallicity galaxy.