Speaker
Description
Galaxy mergers are expected to have a profound influence on the star formation histories of galaxies. It is generally expected
that mergers are the main drivers of galaxy mass growth through the accretion of mass and the triggering of new star formation
episodes, while the shocks and torques induced by the merger may drive gas and dust to central supermassive black holes and fuel
active galactic nuclei (AGN) activity and producing both positive and negative feedback. We test whether a merger-AGN-star formation connection exists by selecting samples of galaxy pairs of stellar masses
log(M/M⊙) ∼ 10.2 and ∼ 11.4 within redshift z < 0.25 at various projected separation and velocity differences in an increasing
order, and therefore having a decreasing probability of being truly bound and interacting. We identify galaxies in close pairs and then measure their star formation rates (SFRs) (via their NUV − r colours) and the degree of AGN activity (from X-rays, radio emission at 20cm, WISE infrared colours, and emission line ratios) as a function of their
projected separation and velocity difference. We find only weak evidence that galaxies in pairs have higher SFRs as galaxies become closer in projected and velocity separation, except possibly for pairs at closest separation of rp < 20 kpc and ∆V < 500 km/s. Similarly, we see no strong evidence that AGN are more common for galaxies in closer pairs, irrespective of the method used to detect AGN. For this sample, we do not find any clear evidence that mergers and interactions may play a significant role in triggering star formation and AGN activity, opposite to expectations from theoretical models invoking feedback episodes. Secular processes may be more important, although this may depend on the selection of galaxies and indicators for star formation and AGN activity.