Dust Heating by Low-mass Stars in Massive Galaxies at z<1
  Using the Hubble Space Telescope/Wide Field Camera 3 imaging data and
multi-wavelength photometric catalog, we investigated the dust temperature of
passively evolving and star-forming galaxies at 0.2<z<1.0 in the CANDELS
fields. We estimated the stellar radiation field by low-mass stars from the
stellar mass and surface brightness profile of these galaxies and then
calculated their steady-state dust temperature. At first, we tested our method
using nearby early-type galaxies with the deep FIR data by the Herschel Virgo
cluster survey and confirmed that the estimated dust temperatures are
consistent with the observed temperatures within the uncertainty. We then
applied the method to galaxies at 0.2<z<1.0, and found that most of passively
evolving galaxies with Mstar > 10^{10} Msun have a relatively high dust
temperature of Tdust > 20 K, for which the formation efficiency of molecular
hydrogen on the surface of dust grains in the diffuse ISM is expected to be
very low from the laboratory experiments. The fraction of passively evolving
galaxies strongly depends on the expected dust temperature at all redshifts and
increases rapidly with increasing the temperature around Tdust ~ 20 K. These
results suggest that the dust heating by low-mass stars in massive galaxies
plays an important role for the continuation of their passive evolution,
because the lack of the shielding effect of the molecular hydrogen on the UV
radiation can prevent the gas cooling and formation of new stars.
