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|Title:||Radio Loud AGNs are Mergers||Authors:||Chiaberge, Marco
Lotz, Jennifer M.
|Issue Date:||2015||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||806||Issue:||2||First Page:||147||Abstract:||We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei (AGNs) at z\gt 1 using new samples. The objects have Hubble Space Telescope (HST) images taken with Wide Field Camera 3 (WFC3) in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z\gt 1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%<SUB>-14%</SUB><SUP>+8%</SUP>) radio-loud galaxies at z\gt 1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38%<SUB>-15</SUB><SUP>+16</SUP> are merging systems. The merger fraction for the sample of non-active galaxies at z\gt 1 is indistinguishable from radio-quiet objects. This is strong evidence that mergers are the triggering mechanism for the radio-loud AGN phenomenon and the launching of relativistic jets from supermassive black holes (SMBHs). We speculate that major black hole (BH)-BH mergers play a major role in spinning up the central SMBHs in these objects.||Acknowledgments:||The authors wish to thank G. Zamorani, C. O’Dea, S. Baum, and A. Capetti for insightful comments and suggestions. We acknowledge W. B. Sparks and the HST -3CR collaboration for making the images of the 3C radio galaxies available for this work. We are also indebted to M. Stiavelli and A. Mortazavi for helping out with the mergers classification. We are also greatful to the anonymous referee for their helpful comments that greatly improved the paper. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This work is based on observations taken by the CANDELS Multi-Cycle Treasury Program with the NASA/ESA HST , which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. This work is based on observations taken by the 3D- HST Treasury Program (GO 12177 and 12328) with the NASA/ESA HST . Based on observations made with the NASA/ESA HST , obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.||URI:||http://hdl.handle.net/20.500.12386/23734||URL:||https://iopscience.iop.org/article/10.1088/0004-637X/806/2/147||ISSN:||0004-637X||DOI:||10.1088/0004-637X/806/2/147||Bibcode ADS:||2015ApJ...806..147C||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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