A multiwavelength characterization of the obscuring medium at the center of NGC 6300

¹ Dipartimento di Fisica e Astronomia (DIFA), Università di Bologna, via Gobetti 93/2, I-40129 Bologna, Italy
² INAF-Osservatorio di Astrofisica e Scienza dello Spazio (OAS), via Gobetti 93/3, I-40129 Bologna, Italy
³ Department of Physics, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
⁴ Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634, USA
⁵ Department of Astronomy, University of Virginia, P.O. Box 400325 Charlottesville, VA 22904, USA
⁶ European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
⁷ Department of Physics, Informatics and Mathematics, University of Modena and Reggio Emilia, 41125 Modena, Italy
⁸ Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch, 7701 Cape Town, South Africa
⁹ Inter-university Institute for Data Intensive Astronomy, Department of Astronomy, University of Cape Town, 7701 Rondebosch, Cape Town, South Africa
¹⁰ INAF, Instituto di Radioastronomia-Italian ARC, Via Piero Gobetti 101, I-40129 Bologna, Italy
¹¹ Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

^⋆ Corresponding author.

Received: 30 September 2024
Accepted: 17 February 2025

Abstract

Most of the supermassive black holes in the Universe accrete material in an obscured phase. While it is commonly accepted that the “dusty torus” is responsible for the nuclear obscuration, its geometrical, physical, and chemical properties are far from being properly understood. In this paper, we take advantage of the multiple X-ray observations taken between 2007 and 2020, as well as of optical to far infra-red (FIR) observations of NGC 6300, a nearby (z = 0.0037) Seyfert 2 galaxy. The goal of this project is to study the nuclear emission and the properties of the obscuring medium, through a multiwavelength study conducted from X-ray to IR. We perform a simultaneous X-ray spectral fitting and optical-FIR spectral energy distribution (SED) fitting to investigate the obscuring torus. For the X-ray spectral fitting, physically motivated torus models, such as borus02, UXCLUMPY, and XClumpy are used. The SED fitting is done using XCIGALE. Through joint analysis, we constrain the physical parameters of the torus and the emission properties of the accreting supermassive black hole. Through X-ray observations taken in the last 13 years, we have not found any significant line-of-sight column density variability for this source, but observed the X-ray flux dropping ∼40% to 50% in 2020 with respect to previous observations. The UXCLUMPY model predicts the presence of an inner ring of Compton-thick gaseous medium, responsible for the reflection dominated spectra above 10 keV. Through multiwavelength SED fitting, we measure an Eddington accretion rate λ_Edd ∼ 2 × 10⁻³, which falls in the range of the radiatively inefficient accretion solutions.