The Epoch of IGM heating by early sources of X-rays
The Epoch of IGM heating by early sources of X-rays
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早期 X 射线源 IGM 加热时代
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
T. Matteo
中科院分区：
文献类型：
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作者：
Marius B. Eide;L. Graziani;B. Ciardi;Yu Feng;K. Kakiichi;T. Matteo
对中性氢 21 厘米线的观察表明，加热纪元 (EoH) 可能先于后来的再电离纪元 (EoR)。在这里，我们研究了高红移宇宙中电离源的不同假设对EoH期间星际介质（IGM）的电离态和热历史的影响：（i）恒星，（ii）X射线双星（XRB），（iii）热星际介质（ISM）的热韧致辐射，以及（iv）吸积核黑洞（BH）。为此，我们使用宇宙学 3D 辐射传输代码 CRASH 对 (100 h−1 cMpc)3 流体动力学模拟 MassiveBlack-II 的输出进行后处理，该代码跟踪 UV 和 X 射线光子的传播，通过 EoH 计算氢和氦的热态和电离态。我们发现恒星决定了 IGM 的完全电离形态，而光谱硬的 XRB 则为光谱较软的 ISM 进行有效的后续加热和电离铺平了道路。根据 MassiveBlack-II 中的播种处方，BH 对电离或加热没有显着贡献。在只有恒星的情况下，大部分 IGM 仍处于冷状态（在 z = 10 时，中位 T = 11 K），然而，能量更高的源的存在使最亮和更聚集的源周围区域的温度升高到高于 CMB 的温度，从而为观测发射中的 21 cm 信号提供了可能性。
Observations of the 21 cm line from neutral hydrogen indicate that an Epoch of Heating (EoH) might have preceded the later Epoch of Reionization (EoR). Here we study the effects on the ionization state and the thermal history of the Intergalactic Medium (IGM) during the EoH induced by different assumptions on ionizing sources in the high redshift Universe: (i) stars, (ii) X-ray binaries (XRBs), (iii) thermal bremsstrahlung of the hot Interstellar Medium (ISM), and (iv) accreting nuclear black holes (BHs). To this aim, we post-process outputs from the (100 h−1 cMpc)3 hydrodynamical simulation MassiveBlack-II with the cosmological 3D radiative transfer code CRASH, which follows the propagation of UV and X-ray photons, computing the thermal and ionization state of hydrogen and helium through the EoH. We find that stars determine the fully ionized morphology of the IGM, while the spectrally hard XRBs pave way for efficient subsequent heating and ionization by the spectrally softer ISM. With the seeding prescription in MassiveBlack-II, BHs do not contribute significantly to either ionization or heating. With only stars, most of the IGM remains in a cold state (with a median T = 11 K at z = 10), however, the presence of more energetic sources raises the temperature of regions around the brightest and more clustered sources above that of the CMB, opening the possibility to observing the 21 cm signal in emission.