  We present an optical and near-infrared (hereafter NIR) polarimetric study of
a comet C/2013 US10 (Catalina) observed on UT 2015 December 17-18 at phase
angles of $\alpha$=52.1 deg - 53.1 deg. Additionally, we obtained an optical
spectrum and multi-band images to examine the influence of gas emission. We
find that the observed optical signals are significantly influenced by gas
emission, that is, the gas-to-total intensity ratio varies from 5 to 30 % in
the $R_{\rm C}$ and 3 to 18 % in the $I_{\rm C}$ bands, depending on the
position in the coma. We derive the `gas-free dust polarization degrees' of
13.8$\pm$1.0 % in the $R_{\rm C}$ and 12.5$\pm$1.1 % in the $I_{\rm C}$ bands
and a gray polarimetric color, i.e., -8.7$\pm$9.9 % $\mu \mathrm{m}$$^{-1}$ in
optical and 1.6$\pm$0.9 % $\mu \mathrm{m}$$^{-1}$ in NIR. The increments of
polarization obtained from the gas correction show that the polarimetric
properties of the dust in this low-polarization comet are not different from
those in high-polarization comets. In this process, the cometocentric distance
dependence of polarization has disappeared. We also find that the $R_{\rm
C}$-band polarization degree of the southeast dust tail, which consists of
large dust particles (100 $\mu \mathrm{m}$ - 1 mm), is similar to that in the
outer coma where small and large ones are mixed. Our study confirms that the
dichotomy of cometary polarization does not result from the difference of dust
properties, but from depolarizing gas contamination. This conclusion can
provide a strong support for similarity in origin of comets.
