Contributed Talk - Splinter EScience

Friday, 17 September 2021, 09:00   (virtual ESc)

Probabilistic flux variation gradient

Francisco Pozo Nunes, Nikos Gianniotis, Kai Lars Polsterer
Astroinformatics, Heidelberg Institute for Theoretical Studies (HITS)

We present a probabilistic reformulation of the flux variation gradient (FVG) method in the context of photometric reverberation mapping of active galactic nuclei (AGN). The FVG is used to disentangle the AGN and host-galaxy contributions to the total flux in different photometric bands. The method relies on the “observed bluer when brighter phenomena” attributed to the superimposition of a red-host galaxy whose luminosity is constant in time, and a blue AGN whose luminosity does vary over time. Our main motivation for reformulating the existing FVG method is our wish of quantifying the uncertainty of the galaxy contribution estimate. Additionally, the presented probabilistic extension makes it possible to consider observations in multiple bands in a joint manner, and also to account for observational noise. We present details of the probabilistic recasting of the FVG and its application on a select set of AGN.