Arp 70: an interacting galaxy with extreme outflows

We analysed a Fabry-Pérot (FP) cube of the interacting pair of galaxies Arp 70, which was obtained from the CeSAM public repository of FP data. On the larger galaxy Arp 70b, we detected the spectral signature of two different outflows, one located in the centre and the other associated with a giant H II region in the arm region. The central outflow is especially prominent, with the flux of the secondary peaks in the emission-line profiles due to the outflowing gas being similar to that of the main peak. We used an archive fibre spectrum from SDSS to confirm this detection in H α as well as in the [N II] line and, in addition, to perform diagnostics on the nature of the ionization. The emission at the centre is consistent with a low-ionization nuclear emission-line region and a weak active galactic nucleus. Using the spatial distribution of the profiles in the FP cube, we estimated the shape of the outflow which is consistent with two cones of expanding material, one approaching and the other receding from us, and used this to estimate the physical parameters of the outflow, finding energies of order 10⁵⁷ erg and masses of order 10⁸ M_⊙. On the giant H II region, we found a very large expanding superbubble with a diameter of ∼5 kpc. The bubble has an energy of order 10⁵⁴ erg and a mass of about 4 × 10⁷ M_⊙. We discuss the possible origins for both of these features and whether they could be associated with the interaction between the galaxies.