The Host Galaxy Fluxes of Active Galaxy Nuclei Are Generally Overestimated by the Flux Variation Gradient Method

Document detail

ID

oai:arXiv.org:2407.03597

Topic

Astrophysics - Astrophysics of Gal...

Author

Cai, Minxuan Wan, Zhen Cai, Zhenyi Fan, Lulu Wang, Junxian

Year

2024

listing date

7/10/2024

Keywords

agn variation flux method fvg host

Metrics

Abstract

In terms of the variable nature of normal active galaxy nuclei (AGN) and luminous quasars, a so-called flux variation gradient (FVG) method has been widely utilized to estimate the underlying non-variable host galaxy fluxes.

The FVG method assumes an invariable AGN color, but this assumption has been questioned by the intrinsic color variation of quasars and local Seyfert galaxies.

Here, using an up-to-date thermal fluctuation model to simulate multi-wavelength AGN variability, we theoretically demonstrate that the FVG method generally overestimates the host galaxy flux; that is, it is more significant for brighter AGN/quasars.

Furthermore, we observationally confirm that the FVG method indeed overestimates the host galaxy flux by comparing it to that estimated through other independent methods.

We thus caution that applying the FVG method should be performed carefully in the era of time-domain astronomy.

Cai, Minxuan,Wan, Zhen,Cai, Zhenyi,Fan, Lulu,Wang, Junxian, 2024, The Host Galaxy Fluxes of Active Galaxy Nuclei Are Generally Overestimated by the Flux Variation Gradient Method