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Description
We investigate the relation between star formation rate (SFR) and gas surface densities in Galactic star-forming regions using a sample of young stellar objects (YSOs) and massive dense clumps. Our YSO sample consists of objects located in 20 large molecular clouds from the Spitzer cores to disks (c2d; Evans, 2009, Cat. J/ApJS/181/321) and Gould's Belt (GB) survey (L. Allen et al. 2010, in preparation). These data allow us to probe the regime of low-mass star formation, essentially invisible to tracers of high-mass star formation used to establish extragalactic SFR-gas relations. We estimate the gas surface density ({Sigma}_gas_) from extinction (A_V_) maps and YSO SFR surface densities ({Sigma}_SFR_) from the number of YSOs, assuming a mean mass and lifetime. We also divide the clouds into evenly spaced contour levels of A_V_, counting only Class I and Flat spectral energy distribution YSOs, which have not yet migrated from their birthplace. For a sample of massive star-forming clumps, we derive SFRs from the total infrared luminosity and use HCN gas maps to estimate gas surface densities. We find that c2d and GB clouds lie above the extragalactic SFR-gas relations (e.g., Kennicutt-Schmidt law) by factors of up to 17. We use ^12^CO and ^13^CO gas maps of the Perseus and Ophiuchus clouds from the COMPLETE survey (Ridge et al. 2006AJ....131.2921R) to estimate gas surface densities and compare to measurements from A_V_ maps.
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