We present 13CO(1-0) observations for the EDGE-CALIFA survey, which is a
mapping survey of 126 nearby galaxies at a typical spatial resolution of 1.5
kpc. Using detected 12CO(1-0) emission as a prior, we detect 13CO(1-0) in 41
galaxies via integrated line flux over the entire galaxy, and in 30 galaxies
via integrated line intensity in resolved synthesized beams. Incorporating our
CO observations and optical IFU spectroscopy, we perform a systematic
comparison between the line ratio R12/13 and the properties of the stars and
ionized gas. Higher R12/13 values are found in interacting galaxies than in
non-interacting galaxies. The global R12/13 slightly increases with infrared
color F60/F100, but appears insensitive to other host galaxy properties such as
morphology, stellar mass, or galaxy size. We also present annulus-averaged
R12/13 profiles for our sample up to a galactocentric radius of 0.4r25 (~6
kpc), taking into account the 13CO(1-0) non-detections by spectral stacking.
The radial profiles of R12/13 are quite flat across our sample. Within
galactocentric distances of 0.2r25, azimuthally-averaged R12/13 increases with
star formation rate. However, the Spearman rank correlation tests show the
azimuthally-averaged R12/13 does not strongly correlate with any other gas or
stellar properties in general, especially beyond 0.2r25 from the galaxy
centers. Our findings suggest that in the complex environments in galaxy disks,
R12/13 is not a sensitive tracer for ISM properties. Dynamical disturbances,
like galaxy interactions or the presence of a bar, also have an overall impact
on R12/13, which further complicate the interpretations of R12/13 variations.Comment: 35pages, 11 figure, 6 tables, accepted for publication in ApJ