The Relative Wavelength Independence of IR Time Lags in NGC4151 During the Years 2010-2015

Abstract

We present results of a study of the correlation between the infrared (JHKL) and optical(B) fluxes of the nucleus of the Seyfert galaxy NGC 4151 for the years 2010 - 2015 using our own data (partially published) in combination with published data of Roberts and Rumstey (2012), Guo et al. (2014) and Schnulle et al. (2013, 2015).We find similar lags for each of the HKL passbands relative to the optical of 37 +-3 days. The lags are the same to within the accuracy of measurement. We do not confirm a significant decrease in the lag for HKL in 2013-2014 previously reported by Schnulle et al. (2015), but we find that the lag of the short-lag component of J increased. We discuss our results within the framework of the standard model, where the variable infrared radiation is mainly due to the thermal re-emission of short-wave radiation by dust clouds close to a variable central source. There is also some contribution to the IR emission from the accretion disk, and this contribution increases with decreasing wavelength. The variability in J and K is not entirely simultaneous, which may be due to the differing contributions of the radiation from the accretion disk in these bands. The absence of strong wavelength-dependent changes in infrared lag across the HKL passbands can be explained by having the dust clouds during 2010-2015 be located beyond the sublimation radius. The relative wavelength independence of the infrared lags is also consistent with the hollow bi-conical outflow model of Oknyansky et al. (2015).

28 pages, 7 figures

References in corpus (8)

• AGN Dusty Tori: I. Handling of Clumpy Media
• A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
• Variation of Inner Radius of Dust Torus in NGC4151
• A New Method for Measuring Extragalactic Distances
• Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
• Modeling the Infrared Reverberation Response of the Circumnuclear Dusty Torus in AGN: The Effects of Cloud Orientation and Anisotropic Illumination
• Monitoring the temperature and reverberation delay of the circumnuclear hot dust in NGC 4151
• Calibration of AGN Reverberation Distance Measurements

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• The Dusty Heart of NGC 4151 Revealed by $\lambda \sim$1-40 $\mu$m Reverberation Mapping and Variability: A Challenge to Current Clumpy Torus Models
• The post-maximum behaviour of the changing-look Seyfert galaxy NGC 1566
• Changing looks of the nucleus of the Seyfert galaxy NGC 1566 compared with other changing-look AGNs