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

IF 2.5 4区 物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS Universe Pub Date : 2024-06-28 DOI:10.3390/universe10070282
Minxuan Cai, Zhen Wan, Zhenyi Cai, Lulu Fan, Junxian Wang
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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.
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通量变化梯度法普遍高估了活动星系核的宿主星系通量
针对正常活动星系核(AGN)和大光类星体的可变性,一种所谓的通量变化梯度(FVG)方法被广泛用于估算基本的非可变宿主星系通量。FVG方法假定AGN颜色不变,但类星体和本地赛弗星系的内在颜色变化对这一假定提出了质疑。在这里,我们利用最新的热波动模型模拟了多波长AGN的变异,从理论上证明了FVG方法通常会高估宿主星系的通量;也就是说,对于亮度较高的AGN/类星体来说,这种高估更为明显。此外,通过与其他独立方法估算出的宿主星系通量进行比较,我们从观测上证实了FVG方法确实高估了宿主星系通量。因此,我们提醒大家,在时域天文学时代,应用FVG方法应该小心谨慎。
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来源期刊
Universe
Universe Physics and Astronomy-General Physics and Astronomy
CiteScore
4.30
自引率
17.20%
发文量
562
审稿时长
24.38 days
期刊介绍: Universe (ISSN 2218-1997) is an international peer-reviewed open access journal focused on fundamental principles in physics. It publishes reviews, research papers, communications, conference reports and short notes. Our aim is to encourage scientists to publish their research results in as much detail as possible. There is no restriction on the length of the papers.
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