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arXiv 2007.10158astro-ph.IMastro-ph.HE
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Athena X-IFU利用伽马射线暴X射线余辉探测温热星系际介质的能力

Detection capabilities of the Athena X-IFU for the warm-hot intergalactic medium using gamma-ray burst X-ray afterglows

S. Walsh, S. McBreen, A. Martin-Carrillo, T. Dauser, N. Wijers, J. Wilms, J. Schaye, D. Barret

摘要:

在低红移时,观测到的重子密度远远低于预测的重子总数。宇宙学模拟表明,这些重子存在于被称为温热星系际介质(WHIM)的无定形气体结构中。由于这些灯丝的高温,物质被高度电离,从而吸收并发射远紫外和软X射线光子。雅典娜是拟议中的欧洲空间局X射线天文台,其目的是通过活动星系核的吸收和伽马射线暴余辉光谱,探测WHIM中“失踪”的重子,直至$z=1$的红移,从而能够研究宇宙这些大尺度结构的演变。本文利用SIXTE(SIMulationofX射线Telescopes)框架模拟了GRB X射线余辉谱中的WHIM灯丝。我们调查的可行性,他们的检测与X-IFU仪器,通过O VII($E=573$ eV)和O VIII($E=674$ eV)的吸收功能,为一系列的等效宽度印到GRB余辉光谱观察到的起始通量范围之间的$10^{-12}$和$10^{-10}$ erg cm $^{-2}$ s $^{-1}$,在0.3-10千电子伏的能带。用盲线搜索法对X-IFU谱进行分析表明,Athena能探测到具有EW $_\mathrm{O VII} > 0.13$ eV和EW $_\mathrm{O VIII} > 0.09$ eV的O VII-O VIII吸收对,余辉具有$F>2 \times 10^{-11}$ erg cm $^{-2}$ s $^{-1}$。这使得在四年飞行任务寿命期间能够探测到$\approx$ 45-137 O VII-O VIII吸收剂。这项工作表明,要获得O VII-O VIII检测的高统计意义,当地的氢柱密度应限制在$N_\mathrm{H}<8 \times 10^{20}$厘米$^{-2}$。

英文摘要:

At low redshifts, the observed baryonic density falls far short of the total number of baryons predicted. Cosmological simulations suggest that these baryons reside in filamentary gas structures, known as the warm-hot intergalactic medium (WHIM). As a result of the high temperatures of these filaments, the matter is highly ionised such that it absorbs and emits far-UV and soft X-ray photons. Athena, the proposed European Space Agency X-ray observatory, aims to detect the `missing' baryons in the WHIM up to redshifts of $z=1$ through absorption in active galactic nuclei and gamma-ray burst afterglow spectra, allowing for the study of the evolution of these large-scale structures of the Universe. This work simulates WHIM filaments in the spectra of GRB X-ray afterglows with Athena using the SImulation of X-ray TElescopes (SIXTE) framework. We investigate the feasibility of their detection with the X-IFU instrument, through O VII ($E=573$ eV) and O VIII ($E=674$ eV) absorption features, for a range of equivalent widths imprinted onto GRB afterglow spectra of observed starting fluxes ranging between $10^{-12}$ and $10^{-10}$ erg cm$^{-2}$ s$^{-1}$, in the 0.3-10 keV energy band. The analyses of X-IFU spectra by blind line search show that Athena will be able to detect O VII-O VIII absorption pairs with EW$_\mathrm{O VII} > 0.13$ eV and EW$_\mathrm{O VIII} > 0.09$ eV for afterglows with $F>2 \times 10^{-11}$ erg cm$^{-2}$ s$^{-1}$. This allows for the detection of $\approx$ 45-137 O VII-O VIII absorbers during the four-year mission lifetime. The work shows that to obtain an O VII-O VIII detection of high statistical significance, the local hydrogen column density should be limited at $N_\mathrm{H}<8 \times 10^{20}$ cm$^{-2}$.

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