Speaker
Description
The current ∧CDM model of hierarchical galaxy formation highlights the importance of galaxy
interactions and mergers in the evolution of galaxies. Galaxies undergo cycles of star forma-
tion and AGN activity induced by mergers and interactions as they evolve towards early-type
quiescent objects. However, this has not been observationally well supported. In this work, we
aim to go a step further in testing the connection between galaxy mergers, AGN activity, and
star formation in stellar mass-selected close galaxy pairs using unWISE data at low redshift
(z < 0.2). We selected galaxy pairs with mass ratio of 1:3 on average (major mergers) in
two volume-limited samples of mean mass log(M/M⊙) of 10.2 and 11.4 and at six projected
distance separations (0-20, 20-50, 50-100, 100-250, 250-500, 500-1000 kpc using thee standard
cosmology) and two velocity differences (0-500, and 500-1000 km/s). We measured the X-ray
and radio luminosities, W1-W2 colors, and optical emission lines ratios (BPT method) to study
AGN activity, and NUV-r colors to study star formation. We compare the effect of distance and
velocity separations on AGN activity and star formation. Results indicate no significant increase
in AGN fraction (selected in X-rays, radio, infrared, and optical) and a slight suppression of star
formation as pair separation decreases. We compared these results with the Illustris TNG300
simulations and obtained similar findings. This led to the conclusion that galaxy mergers and
interactions may not be the main trigger of AGN activity and may not lead to increased star
formation contrary to previous theoretical expectations.
| Stream | Science or Engineering |
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