Probing the Dust Properties of Galaxies up to Submillimetre Wavelengths
  I. The Spectral Energy Distribution of dwarf galaxies using LABOCA
  We present 870 micron images of four low metallicity galaxies (NGC1705,
Haro11, Mrk1089 and UM311) observed with the Large APEX BOlometer CAmera
(LABOCA). We model their spectral energy distributions combining the submm
observations of LABOCA, 2MASS, IRAS, Spitzer photometric data and the IRS data
for Haro11. We find that a significant mass of dust is revealed when using
submm constraints compared to that measured with only mid-IR to far-IR
observations extending only to 160 microns. For NGC1705 and Haro11, an excess
in submillimeter wavelengths is detected and we rerun our SED procedure adding
a cold dust component (10K) to better describe the high 870 micron flux derived
from LABOCA observations, which significantly improves the fit. We find that at
least 70% of the dust mass of these two galaxies can reside in a cold dust
component. We also show that the subsequent dust-to-gas mass ratios,
considering HI and CO observations, can be strikingly high for Haro11 in
comparison with what is usually expected for these low-metallicity
environments. Furthermore, we derive the SFR of our galaxies and compare them
to the Schmidt law. Haro11 falls anomalously far from the Schmidt relation.
These results may suggest that a reservoir of hidden gas could be present in
molecular form not traced by the current CO observations. We also derive the
total IR luminosities derived from our models and compare them with relations
that derive this luminosity from Spitzer bands. We find that the Draine & Li
(2007) formula compares well to our direct IR determinations.
