What obscures low X-ray-scattering active galactic nuclei?

Abstract

X-ray surveys have revealed a new class of active galactic nuclei (AGN) with a very low observed fraction of scattered soft X-rays, f_scat < 0.5%. Based on X-ray modeling these "X-ray new-type", or low observed X-ray scattering (hereafter:"low-scattering") sources have been interpreted as deeply-buried AGN with a high covering factor of gas. In this paper we address the questions whether the host galaxies of low-scattering AGN may contribute to the observed X-ray properties, and whether we can find any direct evidence for high covering factors from the infrared (IR) emission. We find that X-ray low-scattering AGN are preferentially hosted by highly-inclined galaxies or merger systems as compared to other Seyfert galaxies, increasing the likelihood that the line-of-sight toward the AGN intersects with high columns of host-galactic gas and dust. Moreover, while a detailed analysis of the IR emission of low-scattering AGN ESO 103-G35 remains inconclusive, we do not find any indication of systematically higher dust covering factors in a sample of low-scattering AGN based on their IR emission. For ESO 103-G35, we constrained the temperature, mass and location of the IR emitting dust which is consistent with expectations for the dusty torus. However, a deep silicate absorption feature probably from much cooler dust suggests an additional screen absorber on larger scales within the host galaxy. Taking these findings together, we propose that the low f_scat observed in low-scattering AGN is not necessarily the result of circumnuclear dust but could originate from interference of host-galactic gas with a column density of the order of 10^22 cm^-2 with the line-of-sight. We discuss implications of this hypothesis for X-ray models, high-ionization emission lines, and observed star-formation activity in these objects.

10 pages, 5 figures, 2 tables; accepted for publication in MNRAS

References in corpus (15)

• The XMM-Newton Serendipitous Survey. V. The Second XMM-Newton Serendipitous Source Catalogue
• Swift BAT Survey of AGN
• A diversity of dusty AGN tori: Data release for the VLTI/MIDI AGN Large Program and first results for 23 galaxies
• Radiative Transfer Modeling of Three-Dimensional Clumpy AGN Tori and its Application to NGC 1068
• Dust in the polar region as a major contributor to the IR emission of AGN
• Three-dimensional radiative transfer models of clumpy tori in Seyfert galaxies
• The subarcsecond mid-infrared view of local active galactic nuclei: I. The N- and Q-band imaging atlas
• The distribution of silicate strength in Spitzer spectra of AGNs and ULIRGs
• Suzaku Observations of Active Galactic Nuclei Detected in the Swift/BAT Survey: Discovery of "New Type" of Buried Supermassive Black Holes
• The characteristic blue spectra of accretion disks in quasars as uncovered in the infrared
• Spitzer IRS spectra of a large sample of Seyfert galaxies: a variety of infrared SEDs in the local AGN population
• The Size of the Narrow-Line Emitting Region in the Seyfert 1 Galaxy NGC 5548 from Emission-Line Variability
• The mid IR -- hard X-ray correlation in AGN and its implications for dusty torus models
• The Origin of the Silicate Emission Features in the Seyfert 2 Galaxy, NGC 2110
• The small dispersion of the mid IR -- hard X-ray correlation in AGN

Cited by in corpus (15)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• The subarcsecond mid-infrared view of local active galactic nuclei: II. The mid-infrared--X-ray correlation
• Nuclear 11.3$\mu$m PAH emission in local active galactic nuclei
• On the difference of torus geometry between hidden and non-hidden broad line active galactic nuclei
• BAT AGN Spectroscopic Survey - XI. The Covering Factor of Dust and Gas in Swift/BAT Active Galactic Nuclei
• NuSTAR unveils a Compton-thick Type 2 quasar in Mrk 34
• [O III]$\lambda 5007$ and X-ray Properties of a Complete Sample of Hard X-ray Selected AGNs in the Local Universe
• Herschel Far-Infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. PACS Observations
• Herschel Far-Infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. II. SPIRE Observations
• BAT AGN Spectroscopic Survey XXVII: Scattered X-Ray Radiation in Obscured Active Galactic Nuclei
• The nuclear dust lane of Circinus: collimation without a torus
• Suzaku Follow-up of Heavily Obscured Active Galactic Nuclei Detected in Swift/BAT Survey: NGC 1106, UGC 03752, and NGC 2788A
• Submm-bright X-ray absorbed QSOs at z~2: insights into the co-evolution of AGN and star-formation
• Ray-tracing simulations of the Soft X-ray Scattered Emission in obscured Active Galactic Nuclei
• The SRG/eROSITA all-sky survey: Hard X-ray selected Active Galactic Nuclei