发表机构
Waseda University; The University of Tokyo（早稻田大学; 东京大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用约3500个星系样本，研究发现小红点与恒星形成星系之间在光学连续谱斜率上存在连续序列，无明确边界，并提出中间群体作为过渡候选，支持LRD为连续群体的BH*主导极端。
AI 中文摘要
JWST发现的小红点（LRDs）通常被作为一个独特的对象类别进行分析；然而，它们是否与普通恒星形成星系之间存在真正的边界，尚未在群体层面上得到检验。利用来自DAWN JWST档案的NIRSpec/PRISM光谱，我们选取了约3500个位于3≲z≲8的星系样本，用幂律模型拟合了它们的静止系紫外到光学连续谱发射，并将源定位在β_UV-β_opt平面上。除了一个密集的恒星形成星系区域和一个可以用尘埃红化和/或静止性解释的对角线序列外，我们识别出一个从恒星形成星系区域延伸到LRD区域的垂直序列。该序列平滑且连续地分布，两个群体之间没有明确边界。其中间部分（-1≲β_opt≲0）包含一个约50个源的中间群体，该群体位于LRD选择边界之外，且在很大程度上被忽视；NIRCam成像显示，它们的静止系紫外和光学中值叠加图像介于点状LRD和延展的恒星形成星系之间。我们将垂直序列建模为叠加的恒星形成光谱与源自“The Cliff”（最有力的BH*候选体之一）的黑洞星（BH*）模板的线性混合，并推断在LRD端，黑洞与恒星质量之比η=M_BH/M_*约为0.006-0.1。我们提出将-1≲β_opt≲0作为可能的过渡候选体的实用选择窗口，并认为LRD可能是连续群体中紧凑的、以BH*为主的极端，其中宿主和BH*的相对贡献平滑变化。
英文摘要
The "Little Red Dots" (LRDs) uncovered by JWST are typically analyzed as a distinct class of objects; however, whether they are separated from ordinary star-forming galaxies by a genuine boundary has not been tested at the population level. Using a sample of $\sim3,500$ galaxies at $3 \lesssim z \lesssim 8$ with NIRSpec/PRISM spectra from the DAWN JWST Archive, we modeled their rest-frame UV-to-optical continuum emission with power laws and located the sources in the $β_{\rm{UV}}$-$β_{\rm{opt}}$ plane. Alongside a dense locus of star-forming galaxies and a diagonal sequence which can be explained by dust reddening and/or quiescence, we identify a vertical sequence extending from the locus of star-forming galaxies into the LRD region. This sequence is smoothly and continuously populated, with no clear boundary between the two populations. Its middle section, $-1 \lesssim β_{\rm{opt}} \lesssim 0$, hosts an intermediate population of $\sim50$ sources that falls outside the LRD selection boundary and has been largely overlooked; NIRCam imaging shows their rest-frame UV and optical median stacked images lie between point-like LRDs and extended star-forming galaxies. We modeled the vertical sequence as linear mixtures of stacked star-forming spectra and a black hole star (BH*) template derived from "The Cliff", one of the most compelling BH* candidates, and we infer black hole-to-stellar mass ratios $η= M_{\rm{BH}}/M_* \approx 0.006-0.1$ at the LRD end. We propose $-1 \lesssim β_{\rm{opt}} \lesssim 0$ as a practical selection window for possible transition candidates and argue that LRDs may be the compact, BH*-dominated extreme of a continuous population in which the relative contributions of the host and BH* vary smoothly.
Comments20 pages, 17 figures
