论文标题
Sagittarius B2 -VI的物理和化学结构。 SGR B2中的Uchii区域
The physical and chemical structure of Sagittarius B2 -- VI. UCHII regions in Sgr B2
论文作者
论文摘要
巨型分子云射手座B2（以下称SGRB2）是最大的区域，在银河系中持续的高质量星形成。在SGRB2的中央热核，SGRB2（M）和SGRB2（N）中鉴定了两个超紧凑型HII（UCHII）区域。我们的目的是表征整个SGRB2云中HII区域的属性。比较HII区域和尘埃岩心，我们的目标是描述SGRB2不同部分的进化阶段。我们使用其A，CNB和D配置中的非常大的数组，以及频率频段C（〜6 GHz）中观察整个SGRB2复合物。使用辅助VLA数据在22.4 GHz和96 GHz的ALMA数据中，我们计算了UCHII区域的物理参数及其密集的气体环境。我们在6 GHz图像中识别54个UCHII区域，其中39个在22.4 GHz时也检测到了39个区域。 54个Uchii地区中有八个是新发现的。 UCHII区域的半径在$ 0.006 {\ rm pc} $和$ 0.04 {\ rm pc} $之间，并且具有排放度量介于$ 10^{6} {6} {\ rm pc \，cm^{ - 6}}}}} $和$ 10^{9} $ rm pc \ rm pc \ rm pc \ 6}}}}}}}}}}}}}}} UCHII区域通过B0.5到O6的类型的恒星电离。我们在UCHII区域周围发现了$ \ sim10^6-10^9 {\ rm cm^{ - 3}} $的典型气体密度。 UCHII区域的压力和周围的密集气体是可比的。这些UCHII区域的扩展时间尺度确定为$ \ sim10^4-10^5 {\ rm yr} $。 SGRB2（N），SGRB2（M），SGRB2（S）和SGRB2（ds）分别与HII区域相关的灰尘芯的百分比分别为33％，73％，4％和1％。 SGRB2（DS）中三分之二的灰尘核与流出有关。我们确定的Uchii区域的电子密度与典型的UCHII区域一致，而半径小于典型的Uchii区域。 SGRB2（n）中的灰尘芯比SGRB2（DS）中的进化更具进化，但比SGRB2（M）年轻。
The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass star formation in the Galaxy. Two ultra-compact HII (UCHII) regions were identified in SgrB2's central hot cores, SgrB2(M) and SgrB2(N). Our aim is to characterize the properties of the HII regions in the entire SgrB2 cloud. Comparing the HII regions and the dust cores, we aim to depict the evolutionary stages of different parts of SgrB2. We use the Very Large Array in its A, CnB, and D configurations, and in the frequency band C (~6 GHz) to observe the whole SgrB2 complex. Using ancillary VLA data at 22.4 GHz and ALMA data at 96 GHz, we calculated the physical parameters of the UCHII regions and their dense gas environment. We identify 54 UCHII regions in the 6 GHz image, 39 of which are also detected at 22.4 GHz. Eight of the 54 UCHII regions are newly discovered. The UCHII regions have radii between $0.006 {\rm pc}$ and $0.04 {\rm pc}$, and have emission measure between $10^{6} {\rm pc\,cm^{-6}}$ and $10^{9} {\rm pc\,cm^{-6}}$. The UCHII regions are ionized by stars of types from B0.5 to O6. We found a typical gas density of $\sim10^6-10^9 {\rm cm^{-3}}$ around the UCHII regions. The pressure of the UCHII regions and the dense gas surrounding them are comparable. The expansion timescale of these UCHII regions is determined to be $\sim10^4-10^5 {\rm yr}$. The percentage of the dust cores that are associated with HII regions are 33%, 73%, 4%, and 1% for SgrB2(N), SgrB2(M), SgrB2(S), and SgrB2(DS), respectively. Two-thirds of the dust cores in SgrB2(DS) are associated with outflows. The electron densities of the UCHII regions we identified are in agreement with that of typical UCHII regions, while the radii are smaller than those of the typical UCHII regions. The dust cores in SgrB2(N) are more evolved than in SgrB2(DS) but younger than in SgrB2(M).
