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How to Fuel an AGN: Mapping Circumnuclear Gas in NGC 6240 with ALMA

Medling, Anne M. and Privon, George C. and Barcos-Muñoz, Loreto and Treister, Ezequiel and Cicone, Claudia and Messias, Hugo and Sanders, David B. and Scoville, Nick and U, Vivian and Armus, Lee and Bauer, Franz E. and Chang, Chin-Shin and Comerford, Julia M. and Evans, Aaron S. and Max, Claire E. and Müller-Sánchez, Francisco and Nagar, Neil and Sheth, Kartik (2019) How to Fuel an AGN: Mapping Circumnuclear Gas in NGC 6240 with ALMA. Astrophysical Journal Letters, 885 (1). Art. No. L21. ISSN 2041-8213.

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Dynamical black hole mass measurements in some gas-rich galaxy mergers indicate that they are overmassive relative to their host galaxy properties. Overmassive black holes in these systems present a conflict with the standard progression of galaxy merger–quasar evolution; an alternative explanation is that a nuclear concentration of molecular gas driven inward by the merger is affecting these dynamical black hole mass estimates. We test for the presence of such gas near the two black holes in NGC 6240 using long-baseline ALMA Band 6 observations (beam size 0."06 × 0."03 or 30 pc × 15 pc). We find (4.2–9.8) × 10⁷ M_☉ and (1.2–7.7) × 10⁸ M_☉ of molecular gas within the resolution limit of the original black hole mass measurements for the north and south black holes, respectively. In the south nucleus, this measurement implies that 6%–89% of the original black hole mass measurement actually comes from molecular gas, resolving the tension in the original black hole scaling relations. For the north, only 5%–11% is coming from molecular gas, suggesting the north black hole is actually overmassive. Our analysis provides the first measurement of significant molecular gas masses contaminating dynamical black hole mass measurements. These high central molecular gas densities further present a challenge to theoretical black hole accretion prescriptions, which often assume accretion proceeds rapidly through the central 10 pc.

Item Type:Article
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URLURL TypeDescription Paper
Medling, Anne M.0000-0001-7421-2944
Privon, George C.0000-0003-3474-1125
Barcos-Muñoz, Loreto0000-0003-0057-8892
Treister, Ezequiel0000-0001-7568-6412
Cicone, Claudia0000-0003-0522-6941
Messias, Hugo0000-0002-2985-7994
Sanders, David B.0000-0002-1233-9998
Scoville, Nick0000-0002-0438-3323
U, Vivian0000-0002-1912-0024
Armus, Lee0000-0003-3498-2973
Bauer, Franz E.0000-0002-8686-8737
Chang, Chin-Shin0000-0001-9910-3234
Comerford, Julia M.0000-0001-8627-4907
Evans, Aaron S.0000-0003-2638-1334
Max, Claire E.0000-0003-0682-5436
Müller-Sánchez, Francisco0000-0002-2713-0628
Nagar, Neil0000-0001-6920-662X
Sheth, Kartik0000-0002-5496-4118
Additional Information:© 2019. The American Astronomical Society. Received 2019 July 31; revised 2019 October 2; accepted 2019 October 15; published 2019 October 31. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawai'ian community; we are privileged to be guests on your sacred mountain. We also wish to pay respect to the Atacameño community of the Chajnantor Plateau, whose traditional home now also includes the ALMA observatory. Support for A.M.M. is provided by NASA through Hubble Fellowship grant #HST-HF2-51377 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. G.C.P. acknowledges support from the University of Florida. E.T. acknowledges support from FONDECYT Regular 1160999 and 1190818, CONICYT PIA ACT172033, and Basal-CATA AFB170002 grants. C.C. acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 664931. C.E.M. acknowledges support from the National Science Foundation under award numbers AST-0908796 and AST-1412851. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2015.1.00370.S and ADS/JAO.ALMA#2015.1.00003.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan) and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Some of the 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 was made possible by the generous financial support of the W. M. Keck Foundation. We enthusiastically thank the staff of the W. M. Keck Observatory and its AO team for their dedication and hard work. The analysis presented herein was initiated at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. A.M.M., G.C.P., L.B.M., E.T., and N.S. also thank the Sexten Center for Astrophysics, where the bulk of this paper was written. Facilities: Keck:II (Laser Guide Star Adaptive Optics - , OSIRIS) - , ALMA. -
Group:Infrared Processing and Analysis Center (IPAC), Astronomy Department
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51377
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1160999
Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)1190818
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)ACT172033
Marie Curie Fellowship664931
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Supermassive black holes ; Active galactic nuclei ; Molecular gas ; Bondi accretion ; Accretion
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: Supermassive black holes (1663); Active galactic nuclei (16); Molecular gas (1073); Bondi accretion (174); Accretion (14)
Record Number:CaltechAUTHORS:20191031-141640155
Persistent URL:
Official Citation:Anne M. Medling et al 2019 ApJL 885 L21
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99598
Deposited By: George Porter
Deposited On:01 Nov 2019 14:29
Last Modified:01 Nov 2019 14:29

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