Continuum Reverberation Mapping of 18 AGN Over Four Years

TL;DR

This study monitored 18 active galactic nuclei over four years to measure optical continuum lags, testing models of emission regions and confirming a luminosity-dependent size scaling consistent with reverberation theories.

Contribution

It provides a large, high-quality dataset of continuum lags in AGN, extending the sample and testing the lag-luminosity relation with new measurements.

Findings

Lag size scales with luminosity as τ ∝ L^{0.4}

Results are consistent with theoretical models of accretion disk and BLR reverberation

Supports the continuum emission region being linked to the accretion disk or BLR.

Abstract

Continuum reverberation mapping probes the size scale of the optical continuum-emitting region in active galactic nuclei (AGN). The source of this emission has long been thought to originate from the accretion disk, but recent studies suggest the broad line region (BLR) may significantly contribute to both the observed flux and continuum interband delays. We monitored 18 AGN over four years of observations to acquire high quality optical continuum light curves, measuring time lags between different photometric bands and determining continuum emission sizes for each AGN. We add this sample to existing lag measurements to test the correlation between continuum lags at $5100\r{A}$ ($\tau_{5100}$) and $5100\r{A}$ luminosity ($L_{5100}$). We observe that $\tau_{5100} \propto L_{5100}^{0.4}$, broadly consistent with the theoretical expectations of $\tau \propto L^{1/2}$ expected for continuum reverberation from either the accretion disk or the BLR.