Volume 643, November 2020
|Number of page(s)||24|
|Published online||19 November 2020|
The spatially resolved broad line region of IRAS 09149−6206
Max Planck Institute for Extraterrestrial Physics (MPE), Giessenbachstr. 1, 85748 Garching, Germany
2 LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Paris Diderot, Sorbonne Paris Cité, 5 Place Jules Janssen, 92195 Meudon, France
3 I. Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
4 Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, CA 94720, USA
5 Department of Physics and Astronomy, University of Southampton, Southampton, UK
6 Department of Physics, Kyoto Sangyo University, Kita-ku, Japan
7 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
8 School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
9 Department of Astronomy, The Ohio State University, Columbus, OH, USA
10 Center for Cosmology and AstroParticle Physics, The Ohio State University, Columbus, OH, USA
11 Space Telescope Science Institute, Baltimore, MD, USA
12 Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
13 Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel
14 Center for Computational Astrophysics, Flatiron Institute, 162 5th Ave., New York, NY 10010, USA
15 European Southern Observatory, Casilla, 19001 Santiago 19, Chile
16 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
17 Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA Leiden, The Netherlands
18 Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
19 Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
20 Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
21 CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
22 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
23 Instituto de Astrofísica de Canarias (IAC), 38200 La Laguna, Tenerife, Spain
24 Department of Astrophysical & Planetary Sciences, JILA, University of Colorado, Duane Physics Bldg., 2000 Colorado Ave, Boulder, CO 80309, USA
25 Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
Accepted: 16 September 2020
We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Brγ emission line in the nucleus of the active galaxy IRAS 09149−6206. We use these data to measure the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. This represents an offset of ∼120 μas (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3 μm continuum. The offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Brγ line. We infer the radius of the BLR to be ∼65 μas (0.075 pc), which is consistent with the radius–luminosity relation of nearby active galactic nuclei derived based on the time lag of the Hβ line from reverberation mapping campaigns. Our dynamical modelling indicates the black hole mass is ∼1 × 108 M⊙, which is a little below, but consistent with, the standard MBH–σ* relation.
Key words: galaxies: active / galaxies: nuclei / galaxies: Seyfert / quasars: supermassive black holes / techniques: interferometric
© GRAVITY Collaboration 2020
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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