Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers
Abstract
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 1011 M ⊙ that already have optical active galactic nucleus (AGN) signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N H <~ 1.1 × 1022 cm-2) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f 2-10 keV <~ 1.2 × 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 AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2012
- DOI:
- 10.1088/0004-637X/753/2/165
- arXiv:
- arXiv:1206.1266
- Bibcode:
- 2012ApJ...753..165T
- Keywords:
-
- galaxies: active;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 8 pages, including 5 figures and 1 table. Accepted by ApJ