Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

Journal article

We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 10$^{11}$ $M_\odot$ that already have optical AGN signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured ($N_H \lesssim 1.1 \times 10^{22}$ cm$^{-2}$) X-ray nuclei are relatively common (8/12), but the detections are too faint ($< 40$ counts per nucleus; $f_{2-10 keV} \lesssim 1.2 \times 10^{-13}$ erg s$^{-1}$ cm$^{-2}$) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGN in these mergers are rare (0-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

Authors: Teng, S; Schawinski, K; Urry, C; Darg, D; Kaviraj, S

• Publisher: Institute of Physics Publishing
• Journal: Astrophysical Journal
• Volume: 753
• Issue: 2
• Pages: 165-165
• Publication date: 2012-06-06
• DOI: 10.1088/0004-637X/753/2/165
• EISSN: 1538-4357
• ISSN: 0004-637X
• Language: English
• Keywords: astro-ph.GA; astro-ph.CO