A recent addition to the astronomical taxonomy, courtesy of JWST, is a mysterious population of compact, dust-reddened galaxies at redshifts 3 < z < 9, termed ‘Little Red Dots’ (LRDs). Determining the true nature of LRDs could be an important piece of the puzzle of the formation and evolution of the first galaxies, and Tonima Ananna and colleagues analyse X-ray observations to investigate whether their emission is primarily flux from accreting supermassive black holes (SMBHs) in active galactic nuclei, or might be better accounted for by an alternative scenario such as young stars associated with vigorous star formation.

The team uses ultra-deep observations from the Chandra X-ray Observatory to look at LRDs previously identified from JWST infra-red observations, all located behind the lensing galaxy cluster Abell 2744. Individual LRDs are not detected in the X-ray data, allowing the authors to place upper limits of ≲ (1.5−16) × 10⁶ M_⊙ (assuming Eddington-limited accretion) on the masses of supermassive black holes in these galaxies.

最近由 JWST 提供的天文学分类学中新增了一组神秘的致密、尘红色星系，其红移为 3 < z < 9，被称为“小红点”(LRD)。确定 LRD 的真实性质可能是解开第一批星系形成和演化之谜的一个重要部分，Tonima Ananna 及其同事分析了 X 射线观测结果，以研究它们的发射是否主要来自吸积超大质量黑洞 (SMBH) 的通量在活跃的星系核中，或者可以通过另一种情况更好地解释，例如与活跃的恒星形成相关的年轻恒星。

该团队利用钱德拉 X 射线天文台的超深度观测来观察先前通过 JWST 红外观测发现的 LRD，这些 LRD 均位于透镜星系团 Abell 2744 的后面。在 X 射线数据中未检测到单个 LRD，从而允许作者对这些星系中超大质量黑洞的质量设定了上限 ≲ (1.5−16) × 10 ⁶ M _⊙ （假设爱丁顿有限吸积）。