发表机构
University of Cape Town; IUCAA（开普敦大学; 印度宇宙学研究与天文学中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用MeerKAT在PKS 1158+007方向发现两个HI 21厘米吸收体，其中一个贫金属，揭示盲巡天可发现光学选择遗漏的冷气体。
AI 中文摘要
我们报道了一条朝向耀变体PKS 1158+007（J1201+0028）（$z_{\rm em}$ = 1.369）的有趣视线，利用MeerKAT射电望远镜在狭窄的红移间隔（$\Delta z \sim 0.04$）内罕见地探测到两个介入的HI 21厘米吸收系统。较强的吸收体位于$z_{\rm abs}$ $=0.5653$（$\int\tau dv = 1.31\pm0.04$ km/s），与斯隆数字巡天（SDSS）和暗能量光谱仪（DESI）光谱中看到的强MgII $\lambda2796$系统相关联，其静止系等值宽度分别为$W_{2796} = 1.40\pm0.07$ Å和$1.21\pm0.11$ Å。截然相反的是，第二个探测位于$z_{\rm abs}$ $= 0.5305$，揭示了一个独特的HI 21厘米吸收特征（$\int\tau dv = 0.31 \pm 0.04$ km/s），在光学光谱中没有可探测到的相关金属吸收。该系统代表了“贫金属”HI 21厘米吸收体的典型例子。利用Hyper Suprime-Cam（HSC）PDR3和DESI Legacy Surveys DR10的光度红移，我们识别出一个与这些吸收体重合的广泛星系超密度（在$z \sim0.53\pm0.06$），表明该视线穿透了一个复杂的大尺度结构或丝状结构，这值得通过后续观测加以确认。这些结果凸显了盲HI 21厘米巡天在揭示宇宙中光学/紫外金属线选择可能系统性遗漏的“不可见”冷气体相方面的能力。
英文摘要
We report an interesting line of sight towards the blazar PKS 1158+007 (J1201+0028) ($z_{\rm em}$ = 1.369), revealing the rare detection of two intervening HI 21-cm absorption systems within a narrow redshift interval ($Δz \sim 0.04$) using the MeerKAT radio telescope. The stronger absorber at $z_{\rm abs}$ $=0.5653$ ($\intτdv = 1.31\pm0.04$ \kms) is associated with a strong MgII $\lambda2796$ system seen in the Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) spectra, with rest-frame equivalent widths of $W_{2796} = 1.40\pm0.07$~Å and $1.21\pm0.11$~Å, respectively. In stark contrast, the second detection at $z_{\rm abs}$ $= 0.5305$ reveals a distinct HI 21-cm absorption feature ($\intτdv = 0.31 \pm 0.04$ \kms) with no associated metal absorption detectable in the optical spectra. This system represents a prime example of a "metal-poor'' HI 21-cm absorber. Using photometric redshifts from Hyper Suprime-Cam (HSC) PDR3 and DESI Legacy Surveys DR10, we identify a broad galaxy overdensity (at $z \sim0.53\pm0.06$) coincident with these absorbers, suggesting the sightline pierces a complex large-scale structure or filament, which would be interesting to confirm with follow-up observations. These results underscore the power of blind HI 21-cm surveys to uncover the "invisible'' cold gas phase of the Universe that optical/UV metal-line selection may systematically miss.
Comments12 pages, 5 figures, 3 tables. Accepted for publication in ApJ
