Was 49b: An Overmassive AGN in a Merging Dwarf Galaxy?
Abstract
We present a combined morphological and X-ray analysis of Was 49, an isolated, dual-AGN system notable for the presence of a dominant AGN, Was 49b, in the disk of the primary galaxy, Was 49a, at a projected radial distance of 8 kpc from the nucleus. Using X-ray data from Chandra, the Nuclear Spectroscopic Telescope Array, and Swift, we find that this AGN has a bolometric luminosity of L_(bol) ~ 10^(45) erg s^(−1), with a black hole mass of M_(BH) = 1.3^(+2.9)_(-0.9) x 10^8 M⊙. Despite the large mass, our analysis of optical data from the Discovery Channel Telescope shows that the supermassive black hole (SMBH) is hosted by a stellar counterpart with a mass of only 5.6^(+4.9)_(-2.6) x 10^9 M⊙, which makes the SMBH potentially larger than expected from SMBH–galaxy scaling relations, and the stellar counterpart exhibits a morphology that is consistent with dwarf elliptical galaxies. Our analysis of the system in the r and Kbands indicates that Was 49 is a minor merger, with the mass ratio of Was 49b to Was 49a between ~1:7 and ~1:15. This is in contrast with findings that the most luminous merger-triggered AGNs are found in major mergers and that minor mergers predominantly enhance AGN activity in the primary galaxy.
Additional Information
© 2017 The American Astronomical Society. Received 2016 March 23; revised 2016 December 8; accepted 2016 December 9; published 2017 February 17. We thank the anonymous referee for their thorough review of our manuscript. We also thank Shai Kaspi (Tel Aviv University) for his advice regarding the L_(2-10 KeV)–R_(BLR) relation, René Andrae (Max-Planck-Institut für Astronomie) for his helpful discussion of statistical methods, and Sara Ellison (University of Victoria) for her helpful input during the completion of this work. Finally, we are indebted to Teznie Pugh and Jason Sanborn for their invaluable guidance during our observing run at the DCT. This research has made use of the NuSTAR Data Analysis Software, jointly developed by the ASI Science Data Center (Italy) and the California Institute of Technology (USA) as well as the UK Swift Science Data Centre at the University of Leicester. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration, including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University. The UKIDSS project is defined in Lawrence et al. (2007). UKIDSS uses the UKIRT Wide-Field Camera (WFCAM; Casali et al. 2007). The photometric system is described in Hewett et al. (2006), and the calibration is described in Hodgkin et al. (2009). The WFCAM science archive is described in Hambly et al. (2008). This research made use of Astropy, a community-developed core Python package for astronomy (Astropy Collaboration et al. 2013), and APLpy, an open-source plotting package for Python hosted at http://aplpy.github.com. This research has also made use of the NASA/IPAC Extragalactic Database, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. N.J.S. held an NRC Research Associateship award at Naval Research Laboratory during the course of this research. Basic research in astronomy at the Naval Research Laboratory is funded by the Office of Naval Research.Attached Files
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- CaltechAUTHORS:20161213-111233599
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2016-12-13Created from EPrint's datestamp field
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2021-11-11Created from EPrint's last_modified field
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