Home Galactic ALMA Observations of Giant Molecular Clouds in the Starburst Dwarf Galaxy Henize...

ALMA Observations of Giant Molecular Clouds in the Starburst Dwarf Galaxy Henize 2-10. (arXiv:1812.02180v1 [astro-ph.GA])


Authors: Nia Imara, Christopher M. Faesi

We present new ${}^{12}$CO(J=1-0) observations of Henize 2-10, a blue compact
dwarf galaxy about 8.7 Mpc away, taken with the Atacama Large Millimeter Array.
These are the highest spatial and spectral resolution observations, to date, of
the molecular gas in this starburst galaxy. We measure a molecular mass of
$1.2times10^8 M_odot$ in Henize 2-10, and most of the molecular gas is
contained within a region having a size of about 310 pc. We use the CPROPS
algorithm to identify 119 resolved giant molecular clouds distributed
throughout the galaxy, and the molecular gas contained within these clouds make
up between 45 to 70% of the total molecular mass. The molecular clouds in
Henize 2-10 have similar median sizes (~26 pc), luminous masses (~$ 4times
10^5$ $M_odot$), and surface densities (~$180$ $M_odot$ pc$^{-2}$) to Milky
Way clouds. We provide evidence that Henize 2-10 clouds tend to be in virial
equilibrium, with the virial and luminous masses scaling according to
$M_{vir}propto M_{lum}^{1.2pm0.1}$, similar to clouds in the Milky Way.
However, we measure a scaling relationship between luminous mass and size,
$M_{vir}propto R^{3.0pm0.3}$, that is steeper than what is observed in Milky
Way clouds. Assuming Henize 2-10 molecular clouds are virialized, we infer
values of the CO-to-H$_2$ conversion factor ranging from 0.5 to 13 times the
standard value in the Solar Neighborhood. Given star formation efficiencies as
low as 5%, the most massive molecular clouds in Henize 2-10 currently have
enough mass to form the next generation of super-star clusters in the galaxy.


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