The selective effect of environment on the atomic and molecular
  gas-to-dust ratio of nearby galaxies in the Herschel Reference Survey
  We combine dust, atomic (HI) and molecular (H$_{2}$) hydrogen mass
measurements for 176 galaxies in the Herschel Reference Survey to investigate
the effect of environment on the gas-to-dust mass ($M_{\rm gas}/M_{\rm dust}$)
ratio of nearby galaxies. We find that, at fixed stellar mass, the average
$M_{\rm gas}/M_{\rm dust}$ ratio varies by no more than a factor of $\sim$2
when moving from field to cluster galaxies, with Virgo galaxies being slightly
more dust rich (per unit of gas) than isolated systems. Remarkably, once the
molecular and atomic hydrogen phases are investigated separately, we find that
\hi-deficient galaxies have at the same time lower $M_{\rm HI}/M_{\rm dust}$
ratio but higher $M_{\rm H_{2}}/M_{\rm dust}$ ratio than \hi-normal systems. In
other words, they are poorer in atomic but richer in molecular hydrogen if
normalized to their dust content. By comparing our findings with the
predictions of theoretical models, we show that the opposite behavior observed
in the $M_{\rm HI}/M_{\rm dust}$ and $M_{\rm H_{2}}/M_{\rm dust}$ ratios is
fully consistent with outside-in stripping of the interstellar medium (ISM),
and is simply a consequence of the different distribution of dust, \hi\ and
H$_{2}$ across the disk. Our results demonstrate that the small environmental
variations in the total $M_{\rm gas}/M_{\rm dust}$ ratio, as well as in the
gas-phase metallicity, do not automatically imply that environmental mechanisms
are not able to affect the dust and metal content of the ISM in galaxies.
