Over the last several decades, extensive research has been conducted on the baryon cycles within cosmic structures, encompassing a broad mass range from dwarf galaxies to galaxy clusters. However, a notable gap in understanding the cosmic baryon cycle is the poor galaxy groups with halo masses around 1013 M⊙. Poor galaxy groups, like our own Local Group, are prevalent throughout the Universe, yet robust detection of their hot, X-ray-emitting intragroup medium (IGrM) has remained elusive. The presence of this hot IGrM is crucial for addressing the long-standing “missing baryons” problem. Previous ROSAT-based studies were limited by a small number of X-ray bright samples, thus restricting the scope of their findings. Here, we show a robust detection of this hot IGrM in a large, optically selected poor groups sample, based on the stacked X-ray images from the eROSITA Final Equatorial Depth Survey. These groups are identified in DESI Legacy Survey with a mass range of log(Mhalo/h−1 M⊙) = 11.5–13.5 and a redshift range of z = 0.1–0.5. Additionally, our results indicate that despite its presence in virtually groups at all sizes, this gas component is still not sufficient to recover the universal baryon fraction, and hence the “missing baryons” problem still persists in poor galaxy groups.

中文翻译：

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eROSITA 对光学选择的不良星系群中的热组内培养基进行稳健检测


在过去的几十年里，人们对宇宙结构中的重子周期进行了广泛的研究，包括从矮星系到星系团的广泛质量范围。然而，在理解宇宙重子周期方面，一个显著的差距是晕质量在 1013 M⊙ 附近的贫穷星系群。贫穷的星系群，比如我们自己的本星系群，在整个宇宙中普遍存在，但对其热的、发射 X 射线的星系群内介质 （IGrM） 的可靠探测仍然难以捉摸。这种热 IGrM 的存在对于解决长期存在的“重子缺失”问题至关重要。以前基于 ROSAT 的研究受到少量 X 射线明亮样本的限制，从而限制了他们的发现范围。在这里，我们根据 eROSITA 最终赤道深度巡天的堆叠 X 射线图像，展示了在大型光学选择的贫民群体样本中对这种热 IGrM 的稳健检测。这些组在 DESI Legacy Survey 中被确定，质量范围为 log（Mhalo/h-1 M⊙） = 11.5-13.5，红移范围为 z = 0.1-0.5。此外，我们的结果表明，尽管它存在于各种大小的虚拟星系群中，但这种气体成分仍然不足以恢复普遍的重子部分，因此“重子缺失”问题在贫穷的星系群中仍然存在。