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Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497-Hanny's Voorwerp system

Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497-Hanny's Voorwerp system
Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497-Hanny's Voorwerp system

We present new Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp. The combined fits of the Chandra (0.5-8 keV) and NuSTAR (3-24 keV) X-ray spectra, together with WISE mid-IR photometry, optical longslit spectroscopy and optical narrow-band imaging, suggest that the galaxy hosts a Compton-thick active galactic nucleus (AGN) (NH ~ 2 × 1024 cm-2, current intrinsic luminosity Lbol ~ 2-5 × 1044 erg s-1) whose luminosity dropped by a factor of ~50 within the last ~100 kyr. This corresponds to a change in Eddington ratio (ER) from λEdd ~ 0.35 to λEdd ~ 0.007. We argue that the AGN in IC 2497 should not be classified as a changinglook AGN, but rather we favour the interpretation where the AGN is undergoing a change in accretion state (from radiatively efficient to radiatively inefficient). In this scenario, the observed drop in luminosity and ER corresponds to the final stage of an AGN accretion phase. Our results are consistent with previous studies in the optical, X-ray and radio although the magnitude of the drop is lower than previously suggested. In addition, we discuss a possible analogy between X-ray binaries and an AGN.

Galaxies: active, Quasars: general, Quasars: individual (IC 2497), X-rays: galaxies
0035-8711
2444-2451
Sartori, Lia F.
20154a81-93e2-49b9-9043-ccbcea358333
Schawinski, Kevin
c2dc00fe-35d4-43f2-9462-c59a2f04efe8
Koss, Michael J.
b062518c-e649-4a3b-8bb5-21a3756cc35a
Ricci, Claudio
47c48bd5-233e-41dd-824a-3df26357d84f
Treister, Ezequiel
41255c65-540c-43de-ae46-78299b585717
Stern, Daniel
2eae31a8-424f-4084-837e-ce12a4d00437
Lansbury, George
0f188883-231b-442f-8b44-1d2bafbb5985
Peter Maksym, W.
5f01b503-b25d-4e6d-b202-13764b534834
Baloković, Mislav
159e512c-06ea-4b1c-b580-ec41392aeb3c
Gandhi, Poshak
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Keel, William C.
637aa0a5-f337-4a6f-9e88-f1fbe283f77a
Ballantyne, David R.
2e090d45-4bf6-480e-a634-6f9eb5a511b7
Sartori, Lia F.
20154a81-93e2-49b9-9043-ccbcea358333
Schawinski, Kevin
c2dc00fe-35d4-43f2-9462-c59a2f04efe8
Koss, Michael J.
b062518c-e649-4a3b-8bb5-21a3756cc35a
Ricci, Claudio
47c48bd5-233e-41dd-824a-3df26357d84f
Treister, Ezequiel
41255c65-540c-43de-ae46-78299b585717
Stern, Daniel
2eae31a8-424f-4084-837e-ce12a4d00437
Lansbury, George
0f188883-231b-442f-8b44-1d2bafbb5985
Peter Maksym, W.
5f01b503-b25d-4e6d-b202-13764b534834
Baloković, Mislav
159e512c-06ea-4b1c-b580-ec41392aeb3c
Gandhi, Poshak
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Keel, William C.
637aa0a5-f337-4a6f-9e88-f1fbe283f77a
Ballantyne, David R.
2e090d45-4bf6-480e-a634-6f9eb5a511b7

Sartori, Lia F., Schawinski, Kevin, Koss, Michael J., Ricci, Claudio, Treister, Ezequiel, Stern, Daniel, Lansbury, George, Peter Maksym, W., Baloković, Mislav, Gandhi, Poshak, Keel, William C. and Ballantyne, David R. (2018) Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497-Hanny's Voorwerp system. Monthly Notices of the Royal Astronomical Society, 474 (2), 2444-2451. (doi:10.1093/mnras/stx2952).

Record type: Article

Abstract

We present new Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp. The combined fits of the Chandra (0.5-8 keV) and NuSTAR (3-24 keV) X-ray spectra, together with WISE mid-IR photometry, optical longslit spectroscopy and optical narrow-band imaging, suggest that the galaxy hosts a Compton-thick active galactic nucleus (AGN) (NH ~ 2 × 1024 cm-2, current intrinsic luminosity Lbol ~ 2-5 × 1044 erg s-1) whose luminosity dropped by a factor of ~50 within the last ~100 kyr. This corresponds to a change in Eddington ratio (ER) from λEdd ~ 0.35 to λEdd ~ 0.007. We argue that the AGN in IC 2497 should not be classified as a changinglook AGN, but rather we favour the interpretation where the AGN is undergoing a change in accretion state (from radiatively efficient to radiatively inefficient). In this scenario, the observed drop in luminosity and ER corresponds to the final stage of an AGN accretion phase. Our results are consistent with previous studies in the optical, X-ray and radio although the magnitude of the drop is lower than previously suggested. In addition, we discuss a possible analogy between X-ray binaries and an AGN.

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More information

Accepted/In Press date: 14 November 2017
e-pub ahead of print date: 17 November 2017
Published date: 21 February 2018
Keywords: Galaxies: active, Quasars: general, Quasars: individual (IC 2497), X-rays: galaxies

Identifiers

Local EPrints ID: 418656
URI: http://eprints.soton.ac.uk/id/eprint/418656
ISSN: 0035-8711
PURE UUID: bde4b54d-5a95-4cba-a8b5-daa286d1296e
ORCID for Poshak Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

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Date deposited: 15 Mar 2018 17:30
Last modified: 09 Oct 2020 16:36

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Contributors

Author: Lia F. Sartori
Author: Kevin Schawinski
Author: Michael J. Koss
Author: Claudio Ricci
Author: Ezequiel Treister
Author: Daniel Stern
Author: George Lansbury
Author: W. Peter Maksym
Author: Mislav Baloković
Author: Poshak Gandhi ORCID iD
Author: William C. Keel
Author: David R. Ballantyne

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