Incidence of WISE -selected obscured AGNs in major mergers and interactions from the SDSS
Abstract
We use the Wide-field Infrared Survey Explorer (WISE) and the Sloan Digital Sky Survey (SDSS) to confirm a connection between dust-obscured active galactic nuclei (AGNs) and galaxy merging. Using a new, volume-limited (z ≤ 0.08) catalogue of visually selected major mergers and galaxy-galaxy interactions from the SDSS, with stellar masses above 2 × 1010 M⊙, we find that major mergers (interactions) are 5-17 (3-5) times more likely to have red [3.4] - [4.6] colours associated with dust-obscured or `dusty' AGNs, compared to non-merging galaxies with similar masses. Using published fibre spectral diagnostics, we map the [3.4] - [4.6] versus [4.6] - [12] colours of different emission-line galaxies and find that one-quarter of Seyferts have colours indicative of a dusty AGN. We find that AGNs are five times more likely to be obscured when hosted by a merging galaxy, half of AGNs hosted by a merger are dusty, and we find no enhanced frequency of optical AGNs in merging over non-merging galaxies. We conclude that undetected AGNs missed at shorter wavelengths are at the heart of the ongoing AGN-merger connection debate. The vast majority of mergers hosting dusty AGNs are star forming and located at the centres of Mhalo < 1013 M⊙ groups. Assuming plausibly short-duration dusty-AGN phases, we speculate that a large fraction of gas-rich mergers experience a brief obscured AGN phase, in agreement with the strong connection between central star formation and black hole growth seen in merger simulations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2017
- DOI:
- 10.1093/mnras/stw2620
- arXiv:
- arXiv:1609.04832
- Bibcode:
- 2017MNRAS.464.3882W
- Keywords:
-
- galaxies: active;
- galaxies: evolution;
- galaxies: interactions;
- infrared: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 25 pages, 18 figures, submitted second revision to MNRAS 09/12/2016