Monitoring the temperature and reverberation delay of the circumnuclear hot dust in NGC 4151

Abstract

A hot, dusty torus located around the outer edge of the broad-line region of AGNs is a fundamental ingredient in unified AGN models. While the existence of circumnuclear dust around AGNs at pc-scale radii is now widely accepted, questions about the origin, evolution and long-term stability of these dust tori remain unsettled.\\ We used reverberation mapping of the hot circumnuclear dust in the Seyfert 1 galaxy NGC 4151, to monitor its temperature and reverberation lag as a function of the varying accretion disk brightness. We carried out multiband, multiepoch photometric observations of the nucleus of NGC 4151 in the z,Y,J,H, and K bands for 29 epochs from 2010 January to 2014 June, supported by new near-infrared and optical spectroscopic observations, and archived WISE data.\\ We see no signatures of dust destruction due to sublimation in our data, since they show no increase in the hot dust reverberation delay directly correlated with substantial accretion disk flux increases in the observed period. Instead, we find that the hot dust in NGC 4151 appears to merely heat up, and the hot dust temperature closely tracks the accretion disk luminosity variations. We find indications of a decreased reverberation delay within the observed period from t = 42.5 +/- 4.0 days in 2010 to t = 29.6 +/- 1.7 days in 2013-2014. Such a varying reverberation radius on longer timescales would explain the intrinsic scatter observed in the radius-luminosity relation of dust around AGNs.\\ Our observations rule out that a second, larger dust component within a 100-light-day radius from the source contributes significantly to the observed near-infrared flux in this galaxy.

Accepted for publication in Astronomy & Astrophysics. 18 pages, 15 figures, 7 tables

References in corpus (6)

• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• The innermost region of AGN tori: implications from the HST/NICMOS Type 1 point sources and near-IR reverberation
• A Reverberation-Based Mass for the Central Black Hole in NGC 4151
• Variation of Inner Radius of Dust Torus in NGC4151
• Measuring Quasar Variability with Pan-STARRS1 and SDSS
• Estimating Black Hole Masses in Hundreds of Quasars

Cited by in corpus (8)

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• Reverberation Measurements of the Inner Radii of the Dust Tori in Quasars
• The Intrinsic Far-infrared Continua of Type-1 Quasars
• Infrared Spectral Energy Distribution and Variability of Active Galactic Nuclei: Clues to the Structure of Circumnuclear Material
• The dust sublimation region of the Type 1 AGN NGC4151 at a hundred micro-arcsecond scale as resolved by the CHARA Array interferometer
• The Relative Wavelength Independence of IR Time Lags in NGC4151 During the Years 2010-2015
• A complex dust morphology in the high-luminosity AGN Mrk 876