The University of Southampton
University of Southampton Institutional Repository

A growth-rate indicator for Compton-thick active galactic nuclei

A growth-rate indicator for Compton-thick active galactic nuclei
A growth-rate indicator for Compton-thick active galactic nuclei
Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, ? Edd, and the X-ray power-law index, ?, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic ? is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic ? values and X-ray luminosities, L X. With a simple bolometric correction to L X to calculate ? Edd, we find a statistically significant correlation between ? and ? Edd (p = 0.007). A linear fit to the data yields ? = (0.41 ± 0.18)log10 ? Edd + (2.38 ± 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M BH ? 106–107 M ?) and are highly inclined, our results extend the ?–? Edd relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of ? as a growth-rate indicator for accreting black holes, even for CT AGNs.
1538-4357
1-6
Brightman, M.
eb110ae1-9a2c-4968-b9ef-e7955feba535
Masini, A.
dec115b8-de67-47e6-ba62-b6cd1f112cd3
Ballantyne, D.R.
1b937c4a-8584-4b91-bec0-12fdf75c0886
Baloković, M.
aab173bc-002d-417d-aae0-2c0fddb46745
Brandt, W.N.
2ccd8265-d819-4b7a-8ec8-ced4bfb7baeb
Chen, C.-T.
c4ca76c9-080b-4a5d-8dae-657b5b082802
Comastri, A.
8068001f-aff5-4dcd-906c-1c91af4bad97
Farrah, D.
8ed6de23-8b72-4f38-aace-5de818bfe015
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Harrison, F.A.
b71f286a-75db-46ef-8953-bd41865e74bc
Ricci, C.
82c8f75d-8215-4054-8b69-4cd30ab2d774
Stern, D.
a573010b-ca8e-4018-b0f5-4621657713b3
Walton, D.J.
a1a36b18-a77b-48e8-8665-45bbef0c7bd1
Brightman, M.
eb110ae1-9a2c-4968-b9ef-e7955feba535
Masini, A.
dec115b8-de67-47e6-ba62-b6cd1f112cd3
Ballantyne, D.R.
1b937c4a-8584-4b91-bec0-12fdf75c0886
Baloković, M.
aab173bc-002d-417d-aae0-2c0fddb46745
Brandt, W.N.
2ccd8265-d819-4b7a-8ec8-ced4bfb7baeb
Chen, C.-T.
c4ca76c9-080b-4a5d-8dae-657b5b082802
Comastri, A.
8068001f-aff5-4dcd-906c-1c91af4bad97
Farrah, D.
8ed6de23-8b72-4f38-aace-5de818bfe015
Gandhi, P.
5bc3b5af-42b0-4dd8-8f1f-f74048d4d4a9
Harrison, F.A.
b71f286a-75db-46ef-8953-bd41865e74bc
Ricci, C.
82c8f75d-8215-4054-8b69-4cd30ab2d774
Stern, D.
a573010b-ca8e-4018-b0f5-4621657713b3
Walton, D.J.
a1a36b18-a77b-48e8-8665-45bbef0c7bd1

Brightman, M., Masini, A., Ballantyne, D.R., Baloković, M., Brandt, W.N., Chen, C.-T., Comastri, A., Farrah, D., Gandhi, P., Harrison, F.A., Ricci, C., Stern, D. and Walton, D.J. (2016) A growth-rate indicator for Compton-thick active galactic nuclei. The Astrophysical Journal, 826 (1), 1-6. (doi:10.3847/0004-637X/826/1/93).

Record type: Article

Abstract

Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, ? Edd, and the X-ray power-law index, ?, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic ? is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic ? values and X-ray luminosities, L X. With a simple bolometric correction to L X to calculate ? Edd, we find a statistically significant correlation between ? and ? Edd (p = 0.007). A linear fit to the data yields ? = (0.41 ± 0.18)log10 ? Edd + (2.38 ± 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M BH ? 106–107 M ?) and are highly inclined, our results extend the ?–? Edd relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of ? as a growth-rate indicator for accreting black holes, even for CT AGNs.

Text
1606.09265v1.pdf - Accepted Manuscript
Download (495kB)

More information

Accepted/In Press date: 11 June 2016
e-pub ahead of print date: 25 July 2016
Published date: 25 July 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 399900
URI: https://eprints.soton.ac.uk/id/eprint/399900
ISSN: 1538-4357
PURE UUID: 86fa1835-5ad2-4185-a670-1aace262b8d9
ORCID for P. Gandhi: ORCID iD orcid.org/0000-0003-3105-2615

Catalogue record

Date deposited: 02 Sep 2016 10:48
Last modified: 06 Jun 2018 12:21

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×