Dust Reverberation Mapping and Light-Curve Modelling of Zw229-015

• Main Authors: Guise, E, Hönig, S. F, Gorjian, V, Barth, A. J, Almeyda, T, Pei, L, Cenko, S. B, Edelson, R, Filippenko, A. V, Joner, M. D, Laney, C. D, Li, W, Malkan, M. A, Nguyen, M. L, Zheng, W
• Format: Journal Article
• Language: English
• Published: 03-09-2022
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2209.01409

Multiwavelength variability studies of active galactic nuclei (AGN) can be
used to probe their inner regions which are not directly resolvable. Dust
reverberation mapping (DRM) estimates the size of the dust emitting region by
measuring the delays between the infrared (IR) response to variability in the
optical light curves. We measure DRM lags of Zw229-015 between optical
ground-based and Kepler light curves and concurrent IR Spitzer 3.6 and 4.5
$\mu$m light curves from 2010-2015, finding an overall mean rest-frame lag of
18.3 $\pm$ 4.5 days. Each combination of optical and IR light curve returns
lags that are consistent with each other within 1$\sigma$, which implies that
the different wavelengths are dominated by the same hot dust emission. The lags
measured for Zw229-015 are found to be consistently smaller than predictions
using the lag-luminosity relationship. Also, the overall IR response to the
optical emission actually depends on the geometry and structure of the dust
emitting region as well, so we use Markov chain Monte Carlo (MCMC) modelling to
simulate the dust distribution to further estimate these structural and
geometrical properties. We find that a large increase in flux between the
2011-2012 observation seasons, which is more dramatic in the IR light curve, is
not well simulated by a single dust component. When excluding this increase in
flux, the modelling consistently suggests that the dust is distributed in an
extended flat disk, and finds a mean inclination angle of 49$^{+3}_{-13}$
degrees.