Constrained simulations of the Antennae galaxies: comparison with Herschel-PACS observations

Abstract

We present a set of hydro-dynamical numerical simulations of the Antennae galaxies in order to understand the origin of the central overlap starburst. Our dynamical model provides a good match to the observed nuclear and overlap star formation, especially when using a range of rather inefficient stellar feedback efficiencies (0.01 ≲ q_EoS ≲ 0.1). In this case a simple conversion of local star formation to molecular hydrogen surface density motivated by observations accounts well for the observed distribution of CO. Using radiative transfer post-processing we model synthetic far-infrared spectral energy distributions (SEDs) and two-dimensional emission maps for direct comparison with Herschel-PACS observations. For a gas-to-dust ratio of 62:1 and the best matching range of stellar feedback efficiencies the synthetic far-infrared SEDs of the central star-forming region peak at values of ∼65-81 Jy at 99-116 μm, similar to a three-component modified blackbody fit to infrared observations. Also the spatial distribution of the far-infrared emission at 70 μm, 100 μm and 160 μm compares well with the observations: ≳50 per cent (≳35 per cent) of the emission in each band is concentrated in the overlap region while only <30 per cent (<15 per cent) is distributed to the combined emission from the two galactic nuclei in the simulations (observations). As a proof of principle we show that parameter variations in the feedback model result in unambiguous changes both in the global and in the spatially resolved observable far-infrared properties of Antennae galaxy models. Our results strengthen the importance of direct, spatially resolved comparative studies of matched galaxy merger simulations as a valuable tool to constrain the fundamental star formation and feedback physics.