Photoreverberation mapping of quasars in the context of LSST observing strategies

TL;DR

This paper evaluates the effectiveness of photometric reverberation mapping (PhotoRM) for quasars using simulated and real light curves, in the context of LSST observing strategies, to improve black hole mass measurements.

Contribution

It applies and tests the PhotoRM method on simulated and real data, assessing its accuracy under different LSST observing cadences.

Findings

PhotoRM can recover time lags with reasonable accuracy under LSST-like cadences.

Different observing strategies impact the precision of lag measurements.

Application to NGC 4395 shows consistency with previous studies.

Abstract

The upcoming photometric surveys, such as the Rubin Observatory's Legacy Survey of Space and Time (LSST) will monitor unprecedented number of active galactic nuclei (AGN) in a decade long campaign. Motivated by the science goals of LSST, which includes the harnessing of broadband light curves of AGN for photometric reverberation mapping (PhotoRM), we implement the existing formalism to estimate the lagged response of the emission line flux to the continuum variability using only mutli-band photometric light curves. We test the PhotoRM method on a set of 19 artificial light curves simulated using a stochastic model based on the Damped Random Walk process. These light curves are sampled using different observing strategies, including the two proposed by the LSST, in order to compare the accuracy of time-lag retrieval based on different observing cadences. Additionally, we apply the same procedure for time-lag retrieval to the observed photometric light curves of NGC 4395, and compare our results to the existing literature.