EPoS Contribution
EPoS Contribution
Leaving the neighborhood: the connection between the structure and the star formation rate of giant molecular clouds in the nearby spiral galaxy NGC 300

Jan Forbrich
U Vienna, Vienna, AT
The recent recognition of massive nearby clouds with little star formation activity - the Pipe Nebula and the California Cloud - indicates that the star formation rates in even nearby clouds of similar mass can vary by as much as an order of magnitude. Expanding these results, we found evidence for the dependence of star formation activity on the cloud density structure. Since star formation in local molecular clouds may not be representative for the Galaxy as a whole, these results call for studies of a larger sample of molecular clouds. One exciting possibility is to significantly expand this study by encompassing resolved giant molecular cloud populations in nearby galaxies. The main challenges are to measure the cloud structure and the star formation rates in ways that can be directly compared to local clouds. Here, we will summarize our continuing effort to characterize star formation in a sample of currently 76 H II regions in the nearby spiral galaxy NGC 300 (d=2 Mpc) on scales of 250 pc. We have obtained CO observations of the associated molecular clouds in these regions with the APEX telescope, and additionally, we have mapped the galaxy with the Herschel Space Observatory. To determine the star formation rates of these regions, we use a novel combination of multi-wavelength photometry and population synthesis models to constrain the masses and ages of the associated young clusters. With comparable levels of scatter that reflect physical cloud properties, our NGC 300 sample extends the relation between total gas mass and star formation rate in local Galactic clouds toward larger masses and star formation rates. Connecting small and large scales, we will finally present an outlook with first results of our ongoing high-resolution studies of selected regions in NGC 300, using millimeter interferometry and optical/infrared imaging.
Caption: Star formation rate vs. molecular gas mass for the 42 APEX CO-detected NGC 300 H II regions (filled circles) and 34 upper limits plotted in the context of the local Milky Way clouds (open circles; Lada et al. 2010, 2012). Dotted lines indicate constant depletion times of 20 Myr, 200 Myr, and 2 Gyr. The NGC 300 clouds demonstrate a similar characteristic molecular gas depletion time (~270 Myr) and level of scatter (0.5 dex) as the local clouds. From Faesi, Lada, Forbrich, & Menten (2014, submitted).
Collaborators:
C. Faesi, CfA, US
C. Lada, CfA, US
K. Menten, MPIfR, Germany
J. Alves, U Vienna, Austria
Key publication

Suggested Sessions: Molecular Clouds