A Population of WISE-Selected Dual AGNs Revealed by Chandra
Abstract
Since the vast majority of galaxies contain supermassive black holes (SMBHs) and galaxy interactions trigger nuclear gas accretion, a direct consequence of the hierarchical model of galaxy formation would be the existence of binary active galactic nuclei (AGNs). The existence, frequency, and characteristics of such binary AGNs have important astrophysical implications on the SMBH mass function, the interplay between SMBHs and the host galaxy, and the M-σ relation. Despite decades of searching, and strong theoretical reasons that they should exist, observationally confirmed cases of binary AGNs are extremely rare, and most have been discovered serendipitously. Using the all-sky WISE survey, we identified a population of over one hundred strongly interacting galaxies that display extreme red mid-infrared colors (W1-W2 > 0.8) thus far exclusively associated in extragalactic sources with powerful AGNs. The vast majority of these galaxies are optically quiescent suggesting that they capture a population of binary AGNs that cannot be found through optical studies. In our previous pilot Chandra program, we observed the 6 brightest WISE selected dual AGN candidates with separations of a few kiloparsecs. Of the 5 observed thus far, 4 display two nuclear X-ray point sources consistent with dual AGNs, demonstrating that WISE pre-selection may be effective in identifying a new population of dual AGNs. We have obtained follow-up ground based near-IR spectroscopy of 2 targets that reveal broad Pa-α emission confirming the presence of massive black holes with masses ~ 108 M⊙. We will discuss our findings, the state of this research, and its implications for our understanding of the relationship between SMBHs and their host galaxies.
- Publication:
-
IAU General Assembly
- Pub Date:
- August 2015
- Bibcode:
- 2015IAUGA..2257017S