Continuum Reverberation Mapping of AGN Accretion Disks

Michael M Fausnaugh,David A Starkey,Bradley M Peterson,Keith Horne

doi:10.3389/fspas.2017.00055

Abstract

We show recent detections of inter-band continuum lags in three AGN (NGC~5548, NGC~2617, and MCG+08-11-011), which provide new constraints on the temperature profiles and absolute sizes of the accretion disks. We find lags larger than would be predicted for standard geometrically thin, optically thick accretion disks by factors of 2.3 to 3.3. For NGC~5548, the data span UV through optical/near-IR wavelengths, and we are able to discern a steeper temperature profile than the $T\sim R^{-3/4}$ expected for a standard thin disk . Using a physical model, we are also able to estimate the inclinations of the disks for two objects. These results are similar to those found from gravitational microlensing of strongly lensed quasars, and provide a complementary approach for investigating the accretion disk structure in local, low luminsoity AGN.

Highlights

Active galactic nuclei (AGN) are the markers of rapidly accreting super-massive black holes (SMBHs)
We again fixed the temperature profile power-law index to −3/4, and we found temperatures at the inner edge of the disk hotter than would be implied by the SMBH masses and mass accretion rates derived from the optical luminosity
We have reviewed recent detections of inter-band continuum lags in three AGN, NGC 5548, MCG+08-11-011, and NGC 2617

Summary

INTRODUCTION

Active galactic nuclei (AGN) are the markers of rapidly accreting super-massive black holes (SMBHs). Gas in the BLR reprocesses variations in the ionizing continuum flux from the accretion disk as variable emission line flux after a time delay that scales with the light-crossing time of the BLR. Measuring this time delay provides a straightforward estimate of the BLR’s spatial extent. X-ray emitting corona or the inner edge of the disk) irradiate the outer annuli and drive longer wavelength variations, we expect a time delay between the UV and optical continuum variations that is proportional to the size of the accretion disk (Krolik et al, 1991). We report on recent detections of inter-band continuum lags in two other objects, NGC 5548 and MCG+08-11-011, as well as results from continued monitoring of NGC 2617

AGN STORM

AGN 2014 REVERBERATION MAPPING

Findings

CONCLUSIONS