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High-density disc reflection spectroscopy of low-mass active galactic nuclei

Mallick, L. and Fabian, A. C. and García, J. A. and Tomsick, J. A. and Parker, M. L. and Dauser, T. and Wilkins, D. R. and De Marco, B. and Steiner, J. F. and Connors, R. M. T. and Mastroserio, G. and Markowitz, A. G. and Pinto, C. and Alston, W. N. and Lohfink, A. M. and Gandhi, P. (2022) High-density disc reflection spectroscopy of low-mass active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 513 (3). pp. 4361-4379. ISSN 0035-8711. doi:10.1093/mnras/stac990.

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The standard alpha-disc model predicts an anticorrelation between the density of the inner accretion disc and the black hole mass times square of the accretion rate, as seen in higher mass (M_(BH) > 10⁶ M_⊙) active galactic nuclei (AGNs). In this work, we test the predictions of the alpha-disc model and study the properties of the inner accretion flow for the low-mass end (M_(BH) ≈ 10⁵⁻⁶ M_⊙) of AGNs. We utilize a new high-density disc reflection model where the density parameter varies from nₑ = 10¹⁵ to 10²⁰ cm⁻³ and apply it to the broad-band X-ray (0.3–10 keV) spectra of the low-mass AGN sample. The sources span a wide range of Eddington fractions and are consistent with being sub-Eddington or near-Eddington. The X-ray spectra reveal a soft X-ray excess below ∼1.5 keV which is well modelled by high-density reflection from an ionized accretion disc of density ne ∼ 10¹⁸ cm⁻³ on average. The results suggest a radiation pressure-dominated disc with an average of 70 per cent fraction of the disc power transferred to the corona, consistent with that observed in higher mass AGNs. We show that the disc density higher than 10¹⁵ cm⁻³ can result from the radiation pressure compression when the disc surface does not hold a strong magnetic pressure gradient. We find tentative evidence for a drop in black hole spin at low-mass regimes.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemESA XMM–Newton Science Archive ItemNASA High Energy Astrophysics Science Archive Research Center
Mallick, L.0000-0001-8624-9162
Fabian, A. C.0000-0002-9378-4072
García, J. A.0000-0003-3828-2448
Tomsick, J. A.0000-0001-5506-9855
Parker, M. L.0000-0002-8466-7317
Dauser, T.0000-0003-4583-9048
Wilkins, D. R.0000-0002-4794-5998
De Marco, B.0000-0003-2743-6632
Steiner, J. F.0000-0002-5872-6061
Connors, R. M. T.0000-0002-8908-759X
Mastroserio, G.0000-0003-4216-7936
Markowitz, A. G.0000-0002-2173-0673
Pinto, C.0000-0003-2532-7379
Alston, W. N.0000-0003-2658-6559
Gandhi, P.0000-0003-3105-2615
Additional Information:© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2022 April 5. Received 2022 April 5; in original form 2021 December 9. LM is supported by NASA ADAP grant 80NSSC21K1567. JAG acknowledges support from NASA grant 80NSSC21K1567 and from the Alexander von Humboldt Foundation. JAT acknowledges partial support from NASA ADAP grant 80NSSC19K0586. BDM acknowledges support via Ramón y Cajal Fellowship RYC2018-025950-I. AGM acknowledges partial support from Polish National Science Center (NCN) grant numbers 2016/23/B/ST9/03123 and 2018/31/G/ST9/03224. We thank the anonymous reviewer for a constructive report. We dedicate this paper to doctors and nurses fighting the COVID-19 global pandemic. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA. This research has made use of data, software and/or web tools obtained from the High Energy Astrophysics Science Archive Research Center (HEASARC), a service of the Astrophysics Science Division at NASA/GSFC and of the Smithsonian Astrophysical Observatory’s High Energy Astrophysics Division. DATA AVAILABILITY. All the data used in this article are publicly available from ESA XMM–Newton Science Archive (XSA; and NASA High Energy Astrophysics Science Archive Research Center (HEASARC;
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Alexander von Humboldt FoundationUNSPECIFIED
Ramón y Cajal ProgrammeRYC2018-025950-I
National Science Centre (Poland)2016/23/B/ST9/03123
National Science Centre (Poland)2018/31/G/ST9/03224
Subject Keywords:accretion, accretion discs, black hole physics, relativistic processes, galaxies: active, galaxies: nuclei, X-rays: galaxies
Issue or Number:3
Record Number:CaltechAUTHORS:20220709-032308938
Persistent URL:
Official Citation:L Mallick, A C Fabian, J A García, J A Tomsick, M L Parker, T Dauser, D R Wilkins, B De Marco, J F Steiner, R M T Connors, G Mastroserio, A G Markowitz, C Pinto, W N Alston, A M Lohfink, P Gandhi, High-density disc reflection spectroscopy of low-mass active galactic nuclei, Monthly Notices of the Royal Astronomical Society, Volume 513, Issue 3, July 2022, Pages 4361–4379,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115446
Deposited By: Labani Mallick
Deposited On:11 Jul 2022 17:26
Last Modified:25 Jul 2022 23:13

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