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We present 3, 15, and 33 GHz imaging towards galaxy nuclei and extranuclearstar-forming regions using the Karl G. Jansky Very Large Array as part of theStar Formation in Radio Survey. With $3-33$ GHz radio spectra, we measured thespectral indices and corresponding thermal (free-free) emission fractions for asample of 335 discrete regions having significant detections in at least tworadio bands. After removing 14 likely background galaxies, we find that themedian thermal fraction at 33 GHz is $92 \pm 0.8\%$ with a median absolutedeviation of $11\%$, when a two-component power-law model is adopted to fit theradio spectrum. Limiting the sample to 238 sources that are confidentlyidentified as star-forming regions, and not affected by potential AGNcontamination (i.e., having galactocentric radii $r_{\rm G} \geq 250$ pc),results in a median thermal fraction of $93 \pm 0.8 \%$ with a median absolutedeviation of $10\%$. We further measure the thermal fraction at 33 GHz for 163regions identified at 7" resolution to be $94 \pm 0.8 \%$ with a medianabsolute deviation of $8\%$. Together, these results confirm that free-freeemission dominates the radio spectra of star-forming regions on scales up to$\sim$500 pc in normal star-forming galaxies. We additionally find a factor of$\sim$1.6 increase in the scatter of the measured spectral index and thermalfraction distributions as a function of decreasing galactocentric radius. Thistrend is likely reflective of the continuous star-formation activity occurringin the galaxy centers, resulting a larger contribution of diffuse nonthermalemission relative to star-forming regions in the disk.

The Star Formation in Radio Survey: 3 - 33 GHz Imaging of Nearby Galaxy Nuclei and Extranuclear Star-forming Regions