2016MNRAS.458..772Z

We present infrared (IR) spectral energy distributions (SEDs) of individual star-forming regions in four extremely metal-poor (EMP) galaxies with metallicity Z <= Z_☉/10 as observed by the HerschelSpace Observatory. With the good wavelength coverage of the SED, it is found that these EMP star-forming regions show distinct SED shapes as compared to those of grand design Spirals and higher metallicity dwarfs: they have on average much higher f_70µm/f_160 µm_ ratios at a given f_160 µm_/f250 µm_ ratio; single modified blackbody (MBB) fittings to the SED at λ >= 100 µm still reveal higher dust temperatures and lower emissivity indices compared to that of Spirals, while two MBB fittings to the full SED with a fixed emissivity index (β=2) show that even at 100 µm, about half of the emission comes from warm (50 K) dust, in contrast to the cold (∼20 K) dust component. Our spatially resolved images furthermore reveal that the far-IR colours including f_70 µm_/f160 µm_, f_160 µm_/f250 µm_ and f_250 µm_/f350 µm_ are all related to the surface densities of young stars as traced by far-UV, 24 µm and star formation rates (SFRs), but not to the stellar mass surface densities. This suggests that the dust emitting at wavelengths from 70 to 350 µm is primarily heated by radiation from young stars.