Spatial disconnection between stellar and dust emissions: The test of the Antennae Galaxies (Arp 244)

Abstract

Context. The detection of dust-rich high-redshift galaxies with the Atacama Large Millimeter Array (ALMA), the cold dust emission of which is spatially disconnected from the ultraviolet emission, bears a challenge for modelling their spectral energy distributions (SEDs) with codes based on an energy budget between the stellar and dust components. Aims. We want to test the validity of energy balance modelling on a nearby resolved galaxy with vastly different ultraviolet and infrared spatial distributions and to decipher the kinds of information that can be reliably retrieved from the analysis of the full SED. Methods. We used 15 broadband images of the Antennae Galaxies ranging from far-ultraviolet to far-infrared and divided Arp 244 into 58 square ∼1 kpc2 regions. We fit the data with CIGALE to determine the star formation rate, stellar mass, and dust attenuation of each region. We compared these quantities to those obtained for Arp 244 as a whole. Results. The SEDs of the 58 regions and Arp 244 are well fitted. The estimates of the star formation rate and stellar mass for the whole galaxy are found to be consistent – within one sigma – with the same parameters summed over the 58 regions. We present the spatial distribution of these physical parameters as well as the shape of the attenuation curve across the Antennae Galaxies. We find that the Overlap Region exhibits a high star formation rate, attenuation, and a shallow attenuation curve. We observe a flattening of the attenuation curves with increasing attenuation and dust surface density in agreement with the predictions of hydrodynamical simulations coupled with radiative transfer modelling.