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We present a $^{13}mathrm{CO} (J = 1 rightarrow 0)$ mapping survey of 12 nearby galaxies from the CARMA STING sample. The line intensity ratio $mathcal{R} equiv I[^{12}mathrm{CO} (J = 1 rightarrow 0)]/I[^{13}mathrm{CO} (J = 1 rightarrow 0)]$ is derived to study the variations in molecular gas properties. For 11 galaxies where it can be measured with high significance, the spatially resolved $mathcal{R}$ on (sub-)kiloparsec scales varies by up to a factor of 3--5 within a galaxy. Lower $mathcal{R}$ values are usually found in regions with weaker $^{12}rm CO$. We attribute this apparent trend to a bias against measuring large $mathcal{R}$ values when $^{12}rm CO$ is weak. Limiting our analysis to the $^{12}rm CO$ bright regions that are less biased, we do not find $mathcal{R}$ on (sub)kpc scales correlate with galactocentric distance, velocity dispersion or the star formation rate. The lack of correlation between SFR and $mathcal{R}$ indicates that the CO optical depth is not sensitive to stellar energy input, or that any such sensitivity is easily masked by other factors. Extending the analysis to all regions with $rm ^{12}CO$ emission by spectral stacking, we find that 5 out of 11 galaxies show higher stacked $mathcal{R}$ for galactocentric radii of $gtrsim 1$ kpc and $Sigma_{mathrm{SFR}} lesssim 0.1 rm M_{sun} yr^{-1} kpc^{-2}$, which could result from a greater contribution from diffuse gas. Moreover, significant galaxy-to-galaxy variations are found in $mathcal{R}$, but the global $mathcal{R}$ does not strongly depend on dust temperature, inclination, or metallicity of the galaxy.
This study explores the effects of different assumptions and systematics on the determination of the local, spatially resolved star formation law. Using four star formation rate (SFR) tracers (Halpha with azimuthally averaged extinction correction, m
We investigate the correlation between CO and HI emission in 18 nearby galaxies from the CARMA Survey Toward IR-Bright Nearby Galaxies (STING) at sub-kpc and kpc scales. Our sample, spanning a wide range in stellar mass and metallicity, reveals evide
Dust attenuation in star-forming spiral galaxies affects stars and gas in different ways due to local variations in dust geometry. We present spatially resolved measurements of dust attenuation for a sample of 232 such star-forming spiral galaxies, d
We present the results of our ALMA HCN J=3-2 and HCO+ J=3-2 line observations of a uniformly selected sample (>25) of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. The emission of these dense molecular gas tracers and continuum are spa
The global Schmidt law of star formation provides a power-law relation between the surface densities of star-formation rate (SFR) and gas, and successfully explains plausible scenarios of galaxy formation and evolution. However, star formation being