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Resolving the nuclear obscuring disk in the Compton-thick Seyfert galaxy NGC5643 with ALMA

Resolving the nuclear obscuring disk in the Compton-thick Seyfert galaxy NGC5643 with ALMA
Resolving the nuclear obscuring disk in the Compton-thick Seyfert galaxy NGC5643 with ALMA
We present ALMA Band 6 $^{12}$CO(2--1) line and rest-frame 232GHz continuum observations of the nearby Compton-thick Seyfert galaxy NGC5643 with angular resolutions 0.11-0.26arcsec (9-21pc). The CO(2--1) integrated line map reveals emission from the nuclear and circumnuclear region with a two-arm nuclear spiral extending 10arcsec on each side. The circumnuclear CO(2--1) kinematics can be fitted with a rotating disk, although there are regions with large residual velocities and/or velocity dispersions. The CO(2--1) line profiles of these regions show two different velocity components. One is ascribed to the circular component and the other to the interaction of the AGN outflow, as traced by the [O III]5007AA emission, with molecular gas in the disk a few hundred parsecs from the AGN. On nuclear scales, we detected an inclined CO(2--1) disk (diameter 26 pc, FWHM) oriented almost in a north-south direction. The CO(2--1) nuclear kinematics can be fitted with a rotating disk which appears to be tilted with respect to the large scale disk. There are strong non-circular motions in the central 0.2-0.3 arcsec with velocities of up to 110km/s. In the absence of a nuclear bar, these motions could be explained as radial outflows in the nuclear disk. We estimate a total molecular gas mass for the nuclear disk of $M({\rm H}_2)=1.1\times 10^7\,M_\odot$ and an H$_2$ column density toward the location of the AGN of $N({\rm H}_2)\sim 5 \times 10^{23}\,{\rm cm}^{-2}$, for a standard CO-to-H$_2$ conversion factor. We interpret this nuclear molecular gas disk as the obscuring torus of NGC5643 as well as the collimating structure of the ionization cone.
Astrophysics - Astrophysics of Galaxies
0004-637X
Alonso-Herrero, A.
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Pereira-Santaella, M.
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García-Burillo, S.
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Davies, R.I.
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Combes, F.
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Asmus, D.
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Bunker, A.
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Díaz-Santos, T.
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Gandhi, P.
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González-Martín, O.
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Hernán-Caballero, A.
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Hicks, E.
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Hönig, S.
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Labiano, A.
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Levenson, N.A.
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Packham, C.
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Ramos Almeida, C.
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Ricci, C.
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Rigopoulou, D.
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Rosario, D.
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Sani, E.
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Ward, M.J.
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Alonso-Herrero, A.
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Pereira-Santaella, M.
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García-Burillo, S.
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Davies, R.I.
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Combes, F.
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Asmus, D.
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Bunker, A.
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Díaz-Santos, T.
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Gandhi, P.
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González-Martín, O.
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Hernán-Caballero, A.
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Hicks, E.
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Hönig, S.
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Labiano, A.
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Levenson, N.A.
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Packham, C.
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Ramos Almeida, C.
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Ricci, C.
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Rigopoulou, D.
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Rosario, D.
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Sani, E.
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Ward, M.J.
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Alonso-Herrero, A., Pereira-Santaella, M., García-Burillo, S., Davies, R.I., Combes, F., Asmus, D., Bunker, A., Díaz-Santos, T., Gandhi, P., González-Martín, O., Hernán-Caballero, A., Hicks, E., Hönig, S., Labiano, A., Levenson, N.A., Packham, C., Ramos Almeida, C., Ricci, C., Rigopoulou, D., Rosario, D., Sani, E. and Ward, M.J. (2018) Resolving the nuclear obscuring disk in the Compton-thick Seyfert galaxy NGC5643 with ALMA. The Astrophysical Journal, 859 (144). (doi:10.3847/1538-4357/aabe30).

Record type: Article

Abstract

We present ALMA Band 6 $^{12}$CO(2--1) line and rest-frame 232GHz continuum observations of the nearby Compton-thick Seyfert galaxy NGC5643 with angular resolutions 0.11-0.26arcsec (9-21pc). The CO(2--1) integrated line map reveals emission from the nuclear and circumnuclear region with a two-arm nuclear spiral extending 10arcsec on each side. The circumnuclear CO(2--1) kinematics can be fitted with a rotating disk, although there are regions with large residual velocities and/or velocity dispersions. The CO(2--1) line profiles of these regions show two different velocity components. One is ascribed to the circular component and the other to the interaction of the AGN outflow, as traced by the [O III]5007AA emission, with molecular gas in the disk a few hundred parsecs from the AGN. On nuclear scales, we detected an inclined CO(2--1) disk (diameter 26 pc, FWHM) oriented almost in a north-south direction. The CO(2--1) nuclear kinematics can be fitted with a rotating disk which appears to be tilted with respect to the large scale disk. There are strong non-circular motions in the central 0.2-0.3 arcsec with velocities of up to 110km/s. In the absence of a nuclear bar, these motions could be explained as radial outflows in the nuclear disk. We estimate a total molecular gas mass for the nuclear disk of $M({\rm H}_2)=1.1\times 10^7\,M_\odot$ and an H$_2$ column density toward the location of the AGN of $N({\rm H}_2)\sim 5 \times 10^{23}\,{\rm cm}^{-2}$, for a standard CO-to-H$_2$ conversion factor. We interpret this nuclear molecular gas disk as the obscuring torus of NGC5643 as well as the collimating structure of the ionization cone.

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1804.04842 - Accepted Manuscript
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Accepted/In Press date: 11 April 2018
e-pub ahead of print date: 1 June 2018
Keywords: Astrophysics - Astrophysics of Galaxies

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Local EPrints ID: 421634
URI: https://eprints.soton.ac.uk/id/eprint/421634
ISSN: 0004-637X
PURE UUID: 0b7c7379-4c44-4d73-abdb-61113e7b7d41
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 18 Jun 2018 16:30
Last modified: 14 Mar 2019 01:32

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Contributors

Author: A. Alonso-Herrero
Author: M. Pereira-Santaella
Author: S. García-Burillo
Author: R.I. Davies
Author: F. Combes
Author: D. Asmus
Author: A. Bunker
Author: T. Díaz-Santos
Author: P. Gandhi ORCID iD
Author: O. González-Martín
Author: A. Hernán-Caballero
Author: E. Hicks
Author: S. Hönig
Author: A. Labiano
Author: N.A. Levenson
Author: C. Packham
Author: C. Ramos Almeida
Author: C. Ricci
Author: D. Rigopoulou
Author: D. Rosario
Author: E. Sani
Author: M.J. Ward

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