A UV to X-ray view of soft excess in type 1 AGNs: I. sample selection and spectral profile

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Main Authors: Chen, Shi-Jiang, Wang, Jun-Xian, Kang, Jia-Lai, Kang, Wen-Yong, Sou, Hao, Liu, Teng, Cai, Zhen-Yi, Su, Zhen-Bo
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Published: 2024
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author Chen, Shi-Jiang
Wang, Jun-Xian
Kang, Jia-Lai
Kang, Wen-Yong
Sou, Hao
Liu, Teng
Cai, Zhen-Yi
Su, Zhen-Bo
author_facet Chen, Shi-Jiang
Wang, Jun-Xian
Kang, Jia-Lai
Kang, Wen-Yong
Sou, Hao
Liu, Teng
Cai, Zhen-Yi
Su, Zhen-Bo
contents A core sample of 59 unobscured type 1 AGNs with simultaneous XMM-Newton X-ray and UV observations is compiled from archive to probe the nature of soft X-ray excess (SE). In the first paper of this series, our focus centers on scrutinizing the spectral profile of the soft excess. Of the sources, $\approx$ 71% (42/59) exhibit powerlaw-like (po-like) soft excess, while $\approx$ 29% (17/59) exhibit blackbody-like (bb-like) soft excess. We show a cut-off powerlaw could uniformly characterize both types of soft excesses, with median Ecut of 1.40 keV for po-like and 0.14 keV for bb-like. For the first time, we report a robust and quantitative correlation between the SE profile and SE strength (the ratio of SE luminosity to that of the primary powerlaw continuum in 0.5 - 2.0 keV), indicating that stronger soft excess is more likely to be po-like, or effectively has a higher Ecut. This correlation cannot be explained by ionized disk reflection alone, which produces mostly bb-like soft excess (Ecut $\sim$ 0.1 keV) as revealed by relxilllp simulation. Remarkably, we show with simulations that a toy hybrid scenario, where both ionized disk reflection (relxilllp, with all reflection parameters fixed at default values except for ionization of the disk) and warm corona (compTT, with temperature fixed at 1 keV) contribute to the observed soft excess, can successfully reproduce the observed correlation. This highlights the ubiquitous hybrid nature of the soft X-ray excess in AGNs, and underscores the importance of considering both components while fitting the spectra of soft excess.
format Preprint
id arxiv_https___arxiv_org_abs_2412_11178
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A UV to X-ray view of soft excess in type 1 AGNs: I. sample selection and spectral profile
Chen, Shi-Jiang
Wang, Jun-Xian
Kang, Jia-Lai
Kang, Wen-Yong
Sou, Hao
Liu, Teng
Cai, Zhen-Yi
Su, Zhen-Bo
High Energy Astrophysical Phenomena
Astrophysics of Galaxies
A core sample of 59 unobscured type 1 AGNs with simultaneous XMM-Newton X-ray and UV observations is compiled from archive to probe the nature of soft X-ray excess (SE). In the first paper of this series, our focus centers on scrutinizing the spectral profile of the soft excess. Of the sources, $\approx$ 71% (42/59) exhibit powerlaw-like (po-like) soft excess, while $\approx$ 29% (17/59) exhibit blackbody-like (bb-like) soft excess. We show a cut-off powerlaw could uniformly characterize both types of soft excesses, with median Ecut of 1.40 keV for po-like and 0.14 keV for bb-like. For the first time, we report a robust and quantitative correlation between the SE profile and SE strength (the ratio of SE luminosity to that of the primary powerlaw continuum in 0.5 - 2.0 keV), indicating that stronger soft excess is more likely to be po-like, or effectively has a higher Ecut. This correlation cannot be explained by ionized disk reflection alone, which produces mostly bb-like soft excess (Ecut $\sim$ 0.1 keV) as revealed by relxilllp simulation. Remarkably, we show with simulations that a toy hybrid scenario, where both ionized disk reflection (relxilllp, with all reflection parameters fixed at default values except for ionization of the disk) and warm corona (compTT, with temperature fixed at 1 keV) contribute to the observed soft excess, can successfully reproduce the observed correlation. This highlights the ubiquitous hybrid nature of the soft X-ray excess in AGNs, and underscores the importance of considering both components while fitting the spectra of soft excess.
title A UV to X-ray view of soft excess in type 1 AGNs: I. sample selection and spectral profile
topic High Energy Astrophysical Phenomena
Astrophysics of Galaxies
url https://arxiv.org/abs/2412.11178