Constraining spatial extent and temperature of dust around galaxies from
  far-infrared image stacking analysis
  We propose a novel method to constrain the spatial extent of dust around
galaxies through the measurement of dust temperature. Our method combines the
dust emission of galaxies from far-infrared (FIR) image stacking analysis and
the quasar reddening due to the dust absorption around galaxies. As a specific
application of our method, we use the stacked FIR emission profiles of SDSS
photometric galaxies over the IRAS 100$\mu$m map, and the recent measurement of
the SDSS galaxy-quasar cross-correlation. If we adopt a single-temperature dust
model, the resulting temperature is around 18K, which is consistent with a
typical dust temperature for a central part of galaxies. If we assume an
additional dust component with much lower temperature, the current data imply
the temperature of the galactic dust needs to be higher, 20K to 30K. Since the
model of the density and temperature distribution of dust adopted in the
current paper is very simple, we cannot draw any strong conclusion at this
point. Nevertheless our novel method with the elaborated theoretical model and
multi-band measurement of dust will offer an interesting constraint on the
statistical nature of galactic dust.
