Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*,Astronomy & Astrophysics

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Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*
Astronomy & Astrophysics ( IF 5.4 ) Pub Date : 2024-06-14 , DOI: 10.1051/0004-6361/202449729
F. Peißker , M. Zajaček , M. Melamed , B. Ali , M. Singhal , T. Dassel , A. Eckart , V. Karas

Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members.Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole Sgr A* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources.Methods. Based on the photometric analysis, we estimated the individual H − K and K − L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node.Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and mid-infrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of Sgr A* are much shorter (≪2 yr) than the epochs covered by the observations (≈15 yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20°, implying a common formation process.Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of Sgr A*. Alternatively, the gravitational influence of Sgr A* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement.

中文翻译：

S星团中的候选年轻恒星天体：靠近人马座A*的低质量G天体子群的运动学分析

语境。对 S 星团中几个 L 波段发射源的观察引发了对其性质的丰富讨论。然而，对尘埃物体分类的明确答案需要对紧凑多普勒频移 Brγ 发射的检测做出解释。电离氢与中红外 L 波段连续发射的观察相结合表明，这些来源中的大多数都嵌入在布满灰尘的外壳中。这些嵌入式源是 S 星团的一部分，它们与 S 星的关系仍然存在争议。迄今为止，这两个种群的起源问题一直很模糊，尽管所有解释都支持单个集群成员的迁移过程。这项工作从运动学的角度重新审视了 S 星团及其在开普勒束缚轨道上绕超大质量黑洞 Sgr A* 运行的尘埃成员。目的是探索可能暗示样本非随机分布的模式的开普勒参数。此外，还考虑了各种分析方面来解决粉尘源的性质。方法。基于光度分析，我们估计了源样本的单独 H − K 和 K − L 颜色，并将结果与已知的簇成员进行了比较。分类揭示了 S 星和尘埃源之间的明显对比。为了拟合通量密度分布，我们利用辐射传输代码 HYPERION 并实现了年轻恒星 I 类模型。我们从开普勒拟合结果得到了位置角；另外，我们还分析了升交点的倾角和经度的分布。结果。尘埃源的颜色表明其恒星性质与近红外和中红外区域的光谱能量分布一致。此外，人马座 A* 附近的尘埃和气态团块的蒸发时间尺度（≪2 年）比观测所涵盖的历元（约 15 年）要短得多。除了 D 源恒星分类的有力证据外，我们还发现了遵循文献中提出的 S 星排列的清晰的盘状图案。此外，我们发现所有尘埃源的整体固有倾角为 60 ± 20°，这意味着共同的形成过程。结论。升交点位置角、倾角和经度分布所体现的尘埃源模式强烈暗示了两种不同的情况：主序星和尘埃星S团源具有共同的形成历史或随其迁移Sgr A* 附近有类似的地层通道。或者，人马座 A* 的引力影响与一个巨大的扰动物（例如 IRS 13 星团中假定的中等质量黑洞）相结合，迫使尘埃物体和 S 星遵循特定的轨道排列。