Scalable and Robust Multiband Modeling of AGN Light Curves in Rubin-LSST

TL;DR

This paper introduces EzTaoX, a scalable and accurate multiband modeling tool for AGN light curves from LSST data, enabling detailed variability analysis and time-delay measurements across millions of AGNs.

Contribution

EzTaoX significantly improves speed and accuracy in modeling AGN light curves, leveraging multiband data to enhance variability characterization and time-delay measurement capabilities.

Findings

EzTaoX achieves 100-10,000x speed increase over existing tools.

It accurately recovers simulated variability properties.

Enables detection of low-mass AGNs through variability signatures.

Abstract

The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) will monitor tens of millions of active galactic nuclei (AGNs) for a period of 10 years with an average cadence of 3 days in six broad photometric bands. This unprecedented dataset will enable robust characterizations of AGN UV/optical variability across a wide range of AGN physical properties. However, existing tools for modeling AGN light curves are not yet capable of fully leveraging the volume, cadence, and multiband nature of LSST data. We present EzTaoX, a scalable light curve modeling tool designed to take advantage of LSST's multiband observations to simultaneously characterize AGN UV/optical stochastic variability and measure interband time delays. EzTaoX achieves a speed increase of $\sim 10^2-10^4 \times$ on CPUs over current tools with similar capabilities, while maintaining equal or better accuracy in recovering simulated variability properties. This performance gain enables continuum time-delay measurements for all AGNs discovered by LSST -- both in the Wide Fast Deep survey and the Deep Drilling Fields -- thereby opening new opportunities to probe AGN accretion-flow geometries. In addition, EzTaoX's multiband capability allows robust characterization of AGN stochastic variability down to hourly timescales, facilitating the identification of accreting low-mass AGNs -- such as those residing in dwarf galaxies -- through their distinctive variability signatures.