论文标题
NGC 4945中的积极反馈，淬火和顺序超级星团（SSC）形成
Positive feedback, quenching and sequential super star cluster (SSC) formation in NGC 4945
论文作者
论文摘要
我们已经使用了地面的ALMA成像（分辨率0.1 \ arcSec-0.4 \ arcsec）和HCN和HC $ _3 $ N的振动激发线向NGC 4945的原子核追踪超级星形群（PatoO-SSC）中的Protostellar相。在确定的SSC中，我们发现8个处于原始SSC阶段，显示了振动HCN发射，其中5个也显示了振动HC $ _3 $ n发射。我们估计原始SSC年龄为5-9.7 $ \ times $ 10 $^4 $ yr。只有HCN排放的进化越多，即将达到零年龄的主序（ZAMS； Ages $ \ gtrsim $ 10 $^5 $ yr）。父母云的激发似乎与SSC进化阶段有关，分别具有高（$ \ sim $ 65 K）和最年轻的原始和ZAMS SSC的低（$ \ sim $ 25 K）旋转温度。在SSC ZAMS阶段，HII地区的加热似乎是相当局部的。最年轻的原始SSC位于分子流出的边缘，表明震惊区域中的正反馈形成了SSC。 NGC 4945中的原始SSC似乎比Starburst Galaxy NGC 253中进化得多。我们提出，顺序SSC形成可以解释两个星系中SSC的空间分布和不同年龄。
We have used ALMA imaging (resolutions 0.1\arcsec-0.4\arcsec) of ground and vibrationally excited lines of HCN and HC$_3$N toward the nucleus of NGC 4945 to trace the protostellar phase in Super Star Clusters (proto-SSC). Out of the 14 identified SSCs, we find that 8 are in the proto-SSC phase showing vibrational HCN emission with 5 of them also showing vibrational HC$_3$N emission. We estimate proto-SSC ages of 5-9.7$\times$10$^4$ yr. The more evolved ones, with only HCN emission, are close to reach the Zero Age Main Sequence (ZAMS; ages $\gtrsim$10$^5$ yr). The excitation of the parental cloud seems to be related to the SSC evolutionary stage, with high ($\sim$65 K) and low ($\sim$25 K) rotational temperatures for the youngest proto and ZAMS SSCs, respectively. Heating by the HII regions in the SSC ZAMS phase seems to be rather local. The youngest proto-SSCs are located at the edges of the molecular outflow, indicating SSC formation by positive feedback in the shocked regions. The proto-SSCs in NGC 4945 seem to be more evolved than in the starburst galaxy NGC 253. We propose that sequential SSC formation can explain the spatial distribution and different ages of the SSCs in both galaxies.
