天空中的大环
A Big Ring on the Sky
AI总结：
本研究在MgII吸收体星表中发现第二个超大大尺度结构“天空中的大环”，它与巨弧红移相近、天球间隔小，经多种方法验证显著性最高达5.2σ，为超大大尺度结构起源及宇宙学研究提供新线索。
摘要：
我们公布了“天空中的大环”（BR）的发现，这是继此前报道的巨弧（GA）之后，在MgII吸收体星表中发现的第二个超大大尺度结构（uLSS）。从宇宙学角度来看，BR与GA距离很近——处于相同的红移z~0.8，在天球上的间隔仅约12度。两个非同寻常的uLSS以如此近的构型存在，提升了它们共同构成一个更为非凡的宇宙学系统的可能性。BR是一个引人注目的圆形、环状结构，直径约400 Mpc（固有尺度，对应当前历元）。其发现方法与GA论文中描述的方法一致，但本次使用了限定于DR16Q类星体的新MgII吸收体星表。借助成员球凸包（CHMS）算法，我们估算得出，在对照场的密度下，BR的环体与内部吸收体偏离随机预期的显著性最高达5.2σ。我们公布BR的发现，采用CHMS、最小生成树（MST）、FilFinder以及Cuzick & Edwards（CE）方法评估其显著性，在GA+BR系统的背景下展示该结构，并提出其对uLSS起源及我们宇宙学认知的若干启示。例如，这类uLSS所呈现的特殊几何模式，可能起源于宇宙弦。
英文摘要：
We present the discovery of `A Big Ring on the Sky' (BR), the second ultra-large large-scale structure (uLSS) found in MgII-absorber catalogues, following the previously reported Giant Arc (GA). In cosmological terms the BR is close to the GA - at the same redshift $z \sim 0.8$ and with a separation on the sky of only $\sim 12^\circ$. Two extraordinary uLSSs in such close configuration raises the possibility that together they form an even more extraordinary cosmological system. The BR is a striking circular, annulus-like, structure of diameter $\sim 400$ Mpc (proper size, present epoch). The method of discovery is as described in the GA paper, but here using the new MgII-absorber catalogues restricted to DR16Q quasars. Using the Convex Hull of Member Spheres (CHMS) algorithm, we estimate that the annulus and inner absorbers of the BR have departures from random expectations, at the density of the control field, of up to $5.2σ$. We present the discovery of the BR, assess its significance using the CHMS, Minimal Spanning Tree (MST), FilFinder and Cuzick & Edwards (CE) methods, show it in the context of the GA+BR system, and suggest some implications for the origins of uLSS and for our understanding of cosmology. For example, it may be that unusual geometric patterns, such as these uLSSs, have an origin in cosmic strings.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
