• DOI:10.1093/mnras/sty1147
• Corpus ID: 54007967

Characterization of a candidate dual AGN

@article{Lena2018CharacterizationOA,
  title={Characterization of a candidate dual AGN},
  author={Davide Lena and G. Panizo-Espinar and Peter G. Jonker and Manuel A P Torres and Marianne Heida},
  journal={Monthly Notices of the Royal Astronomical Society},
  year={2018},
  volume={478},
  pages={1326-1340}
}

• D. Lena, G. Panizo-Espinar, +2 authors M. Heida
• Published 30 April 2018
• Physics
• Monthly Notices of the Royal Astronomical Society

We present Chandra and optical observations of a candidate dual active galactic nucleus (AGN) discovered serendipitously while searching for recoiling black holes via a cross-correlation between the serendipitous XMM source catalogue (2XMMi) and SDSS-DR7 galaxies with a separation no larger than 10 times the sum of their Petrosian radii. The system has a stellar mass ratio M_1/M_2 ≈ 0.7. One of the galaxies (Source 1) shows clear evidence for AGN activity in the form of hard X-ray emission and optical emission-line diagnostics typical of AGN ionization. The nucleus of the other galaxy (Source 2) has a soft X-ray spectrum, bluer colours, and optical emission-line ratios dominated by stellar photoionization with a ‘composite’ signature, which might indicate the presence of a weak AGN. When plotted on a diagram with X-ray luminosity versus [OIII] luminosity, both nuclei fall within the locus defined by local Seyfert galaxies. From the optical spectrum, we estimate the electron densities finding n_1 < 27 e− cm^(−3) and n_2 ≈ 200 e− cm^(−3). From a 2D decomposition of the surface brightness distribution, we infer that both galaxies host rotationally supported bulges (Sersic index <1). While the active nature of Source 1 can be established with confidence, whether the nucleus of Source 2 is active remains a matter of debate. Evidence that a faint AGN might reside in its nucleus is, however, tantalizing.