论文标题
追踪10 $^7 $ K热旋转型与紫外线吸收线
Tracing the 10$^7$K Warm-Hot Intergalactic Medium with UV absorption lines
论文作者
论文摘要
如今，宇宙中的大多数宇宙重子都没有直接观察到，导致低红移的“失踪重子”问题。宇宙学水动力学模拟表明，其中很大一部分将转换为所谓的热热层间培养基（WHIM），气温在10 $^5 $ -10 $^7 $ K之间。尽管使用O VI和NE VIII吸收器在UV波长处观察到了这种气体的较冷相，但热的分数检测主要依赖于OVII和O VIII在X射线波长下的观察结果。 Here, we target the forbidden line of [Fe XXI] $λ$ 1354$\unicode{x212B}$ which traces 10$^7$K gas at UV wavelengths, using more than one hundred high-spectral resolution (R$\sim$49,000) and high signal to noise VLT/UVES quasar spectra, corresponding to over 600 hrs of VLT time observations.这些堆栈处于已知DLA的位置，导致5- $σ$限制为$ \ MATHRM {log [n（[fe \，xxi]）] <} $ 17.4（$ {$ {ew_ {erw_ {rest} <22} $ \ m $ \ unicode {x212b} $ {x212b} $ {x212b} $ {x212b} $比预期的塔高。 $ \ mathrm {log [n（[fe \，xxi]）] <} $ 14.5。这项工作提出了X射线检测到的替代方案，该X射线检测到10 $^7 $ k WHIM示踪剂，通过以较高的仪器吞吐量，增强的频谱分辨率，更长的曝光时间和增加目标数量的较高的仪器吞吐量，从地面上瞄准微弱的线条。到达该理论色谱柱密度所需的类星体光谱数量，包括未来的设施，包括4个，ELT/HIRES，MSE和SpectRoscopic望远镜，目前似乎都具有挑战性。探测丢失的重子对于限制对银河系基础的积聚和反馈过程至关重要。
Today, the majority of the cosmic baryons in the Universe are not observed directly, leading to an issue of "missing baryons" at low redshift. Cosmological hydrodynamical simulations have indicated that a significant portion of them will be converted into the so-called Warm-Hot Intergalactic Medium (WHIM), with gas temperature ranging between 10$^5$-10$^7$K. While the cooler phase of this gas has been observed using O VI and Ne VIII absorbers at UV wavelengths, the hotter fraction detection relies mostly on observations of O VII and O VIII at X-ray wavelengths. Here, we target the forbidden line of [Fe XXI] $λ$ 1354$\unicode{x212B}$ which traces 10$^7$K gas at UV wavelengths, using more than one hundred high-spectral resolution (R$\sim$49,000) and high signal to noise VLT/UVES quasar spectra, corresponding to over 600 hrs of VLT time observations. A stack of these at the position of known DLAs lead to a 5-$σ$ limit of $\mathrm{log[N([Fe\,XXI])]<}$17.4 (${EW_{rest}<22}$m$\unicode{x212B}$), three orders of magnitude higher than the expected column density of the WHIM $\mathrm{log[N([Fe\,XXI])]<}$14.5. This work proposes an alternative to X-ray detected 10$^7$K WHIM tracers, by targeting faint lines at UV wavelengths from the ground benefiting from higher instrumental throughput, enhanced spectral resolution, longer exposure times and increased number of targets. The number of quasar spectra required to reach this theoretical column density with future facilities including 4MOST, ELT/HIRES, MSE and the Spectroscopic Telescope appears challenging at present. Probing the missing baryons is essential to constrain the accretion and feedback processes which are fundamental to galaxy formation.
