Molecular gas in supernova local environments unveiled by EDGE

CO observations allow estimation of the gas content of molecular clouds, which trace the reservoir of cold gas fuelling star formation, as well as determination of extinction via H₂ column density, N(H₂). Here, we study millimetric and optical properties at 26 supernovae (SNe) locations of different types in a sample of 23 nearby galaxies, by combining molecular ¹²C¹⁶O (J = 1 → 0) resolved maps from the Extragalactic Database for Galaxy Evolution (EDGE) survey and optical Integral Field Spectroscopy (IFS) from the Calar Alto Legacy Integral Field Area (CALIFA) survey. We found an even clearer separation between type II and type Ibc SNe in terms of molecular gas than is found in the optical using Hα emission as a proxy for the current star formation (SF) rate, which reinforces the fact that SNe Ibc are more associated with SF environments. While A_V at SN locations is similar for SNe II and SNe Ibc and higher than for SNe Ia, N(H₂) is significantly higher for SNe Ibc than for SNe II and Ia. When compared with alternative extinction estimations made directly from SN photometry and spectroscopy, we find that our SNe Ibc also have redder colour excess, but showed standard Na I D absorption pseudo-equivalent widths (∼1 Å). In some cases, we find no extinction when IT is estimated from the environment but high amounts of extinction when measured from SN observations, which suggests that circumstellar material or dust sublimation may be playing a role. This work serves as a benchmark for future studies combining last-generation millimetre and optical IFS instruments to reveal the local environmental properties of extragalactic SNe.