Probing the CIV continuum size luminosity relation in active galactic nuclei with photometric reverberation mapping

TL;DR

This paper proposes an efficient photometric reverberation mapping method to determine the size-luminosity relation of the CIV continuum in active galactic nuclei, enabling faster black hole mass estimates at high redshifts.

Contribution

It introduces a new approach using continuum size-luminosity relation via photometric reverberation mapping, reducing observation time significantly for high-redshift quasars.

Findings

Simulations demonstrate the method's feasibility.

An observational strategy with meter-class telescopes is outlined.

The approach can accelerate size measurements by up to 150 times.

Abstract

Reverberation mapping accurately determines virial black hole masses only for redshifts $z <$ 0.2 by utilizing the relationship between the H$\beta$ broad-line region (BLR) size and the 5100 Angstroms continuum luminosity established with $\sim 200$ active galactic nuclei (AGN). For quasars at $z \sim 2-3$ determining the BLR size is time-consuming and limited by seasonal gaps, requiring e.g., $\sim$ 20 years of monitoring of the CIV emission lines. In this work, we demonstrate that an efficient alternative is to use a continuum size-luminosity relation, which can be obtained up to 150 times faster than BLR sizes using photometric reverberation mapping (PRM). We outline the method and its feasibility based on simulations and propose an observational strategy that can be carried out with meter-class telescopes. In particular, we focus on the ESO La Silla 2.2 meter telescope as it is suitable for an efficient PRM campaign. These observations will provide the scaling factor between the accretion disk and the BLR size (for CIV-1350 Angstroms), which is crucial for estimating the masses of black holes at higher redshifts ($z \gtrsim 2-3$).