The Spectral Energy Distributions (SEDs) of low mass-low metallicity (dwarf) galaxies are a challenging piece to the puzzle of galaxy formation in the near Universe. These SEDs show some particular features in the submillimeter to far-infrared wavelength range -as compared to normal, larger and metal-richer galaxies- that cannot be explained by the current models. These can be summarized as: 1. Broadening of the IR peak, implying the presence of a warmer dust component; 2. Excess emission in the submm ($\sim$500 $\mu$m), causing a flattening of the submm/FIR slope; 3. Less PAH emission lines. With the aim of explaining these features, the SEDs of a sample of 27 simulated dwarf galaxies have been calculated using the GRASIL-3D radiation transfer code. This code has the particularity that it separately treats the radiative transfer in dust grains from molecular clouds and from the cirrus, the respectively dense and diffuse components of the gas phase. The simulated galaxies have stellar masses ranging from 10$^6$-10$^9$ M$_\odot$, and have been run within a Local Group environment with initial conditions from the CLUES project. We report on a careful study of their IRAS, Spitzer and Herschel bands luminosities, as well as of their SFRs, dust and gas (HI and H$_2$) mass contents. We find a satisfactory agreement with observational data, with GRASIL-3D reproducing naturally the spectral features mentioned above. We conclude that the GRASIL-3D two-component dust model gives a physical interpretation to the emission of dwarf galaxies, with molecular clouds and cirrus as the respectively warm and cold dust components needed to recover observational data.
I. Santos-Santos, R. Dominguez-Tenreiro, G. Granato, et. al.
Mon, 13 Mar 17
Comments: 22 pages, 18 figures. Accepted for publication in Astronomy & Astrophysics