The dust SED of dwarf galaxies I. The case of NGC 4214
  The goal of the present study is to establish the physical origin of dust
heating and emission based on radiation transfer models, which
self-consistently connect the emission components from diffuse dust and the
dust in massive star forming regions. NGC 4214 is a nearby dwarf galaxy with a
large set of ancillary data, ranging from the ultraviolet (UV) to radio,
including maps from SPITZER, HERSCHEL and detections from PLANCK. We mapped
this galaxy with MAMBO at 1.2 mm at the IRAM 30 m telescope. We extract
separate dust emission components for the HII regions (plus their associated
PDRs on pc scales) and for the diffuse dust (on kpc scales). We analyse the
full UV to FIR/submm SED of the galaxy using a radiation transfer model which
self-consistently treats the dust emission from diffuse and SF complexes
components, considering the illumination of diffuse dust both by the
distributed stellar populations, and by escaping light from the HII regions.
While maintaining consistency with the framework of this model we additionally
use a model that provides a detailed description of the dust emission from the
HII regions and their surrounding PDRs on pc scales. Due to the large amount of
available data and previous studies for NGC 4214 very few free parameters
remained in the model fitting process. We achieve a satisfactory fit for the
emission from HII+PDR regions on pc scales, with the exception of the emission
at 8\mi, which is underpredicted by the model. For the diffuse emission we
achieve a good fit if we assume that about 30-70% of the emission escaping the
HII+PDR regions is able to leave the galaxy without passing through a diffuse
ISM, which is not an unlikely scenario for a dwarf galaxy which has recently
undergone a nuclear starburst. We determine a dust-to-gas mass ratio of 350-390
which is close to the expected value based on the metallicity.
