Accretion disc sizes from continuum reverberation mapping of AGN selected from the ZTF survey

We present the accretion disc-size estimates for a sample of 19 active galactic nuclei (AGNs) using the optical g-, r-, and i-band light curves obtained from the Zwicky Transient Facility survey. All the AGNs have reliable supermassive black hole (SMBH) mass estimates based on previous reverberation mapping measurements. The multiband light curves are cross-correlated, and the reverberation lag is estimated using the Interpolated Cross-Correlation Function method and the Bayesian method using the javelin code. As expected from the disc-reprocessing arguments, the g - r band lags are shorter than the g - i band lags for this sample. The interband lags for all, but five sources, are larger than the sizes predicted from the standard Shakura Sunyaev (SS) analytical model. We fit the light curves directly using a thin disc model implemented through the javelin code to get the accretion disc sizes. The disc sizes obtained using this model are on an average 3.9 times larger than the prediction based on the SS disc model. We find a weak correlation between the disc sizes and the known physical parameters, namely the luminosity and the SMBH mass. In the near future, a large sample of AGNs covering broader ranges of luminosity and SMBH mass from large photometric surveys would be helpful in a better understanding of the structure and physics of the accretion disc.

Automated summary

In this study, we estimate the accretion disc sizes for a sample of 19 active galactic nuclei (AGNs) using optical light curves from the Zwicky Transient Facility survey. The findings suggest that the g-r band lags are shorter than the g-i band lags as expected from disc-reprocessing arguments. Furthermore, the interband lags for most sources are larger than the sizes predicted by the standard Shakura Sunyaev (SS) analytical model. We also observe a weak correlation between disc sizes and physical parameters such as luminosity and supermassive black hole (SMBH) mass.