Stellar and Gaseous Nuclear Disks Observed in Nearby (U)LIRGs

Creators: Medling, Anne M.; U, Vivian; Guedes, Javiera; Max, Claire E.; Mayer, Lucio; Armus, Lee; Holden, Bradford; Roškar, Rok; Sanders, David

Abstract

We present near-infrared integral field spectroscopy of the central kiloparsec of 17 nearby luminous and ultra-luminous infrared galaxies undergoing major mergers. These observations were taken with OSIRIS assisted by the Keck I and II Adaptive Optics systems, providing spatial resolutions of a few tens of parsecs. The resulting kinematic maps reveal gas disks in at least 16 out of 19 nuclei and stellar disks in 11 out of 11 nuclei observed in these galaxy merger systems. In our late-stages mergers, these disks are young (stellar ages <30 Myr) and likely formed as gas disks that became unstable to star formation during the merger. On average, these disks have effective radii of a few hundred parsecs, masses between 10^8 and 10^(10) M_☉, and v/σ between 1 and 5. These disks are similar to those created in high-resolution hydrodynamical simulations of gas-rich galaxy mergers, and favor short coalescence times for binary black holes. The few galaxies in our sample in earlier stages of mergers have disks that are larger (r_(eff) ~ 200-1800 pc) and are likely remnants of the galactic disks that have not yet been completely disrupted by the merger.

Additional Information

© 2014 American Astronomical Society. Received 2013 October 14; accepted 2014 January 24; published 2014 March 5. We enthusiastically thank the staff of the W. M. Keck Observatory and its AO team, for their dedication and hard work. Data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory and the Keck Laser Guide Star AO systems were both made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, the observations presented herein would not have been possible. We also thank Nate McCrady of the University of Montana for providing spectral templates in the H-band, Nicholas McConnell of the Institute for Astronomy and others for making their OSIRIS calibrations public on the wiki, Loreto Barco and Aaron Evans for making their radio data and preliminary analyses available for comparison, Andrew Green and Massimo Dotti for helpful conversations, and the anonymous referee for thoughtful feedback. This work was supported in part by the National Science Foundation Science and Technology Center for Adaptive Optics, managed by the University of California at Santa Cruz under cooperative agreement AST 98-76783. This material is based in part upon work supported by the National Science Foundation under award number AST-0908796. A.M.M. was supported in part by a Graduate Research Fellowship from the National Science Foundation and by a fellowship from the Achievement Rewards for College Scientists Foundation. V.U. acknowledges funding support from the NASA Harriet G. Jenkins Predoctoral Fellowship Project and the Smithsonian Astrophysical Observatory Predoctoral Fellowship. J.G. acknowledges funding from the ETH Zürich Postdoctoral Fellowship and the Marie Curie Actions for People COFUND Program. Facility: Keck:I,II (Laser Guide Star Adaptive Optics, OSIRIS)

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