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arXiv 2108.02791astro-ph.GAastro-ph.SR
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STEP巡天II:SMC中170个星团的结构分析

STEP Survey II: Structural Analysis of 170 star clusters in the SMC

M. Gatto, V. Ripepi, M. Bellazzini, M. Tosi, M. Cignoni, C. Tortora, S. Leccia, G. Clementini, E. K. Grebel, G. Longo, M. Marconi, I. Musella

摘要:

我们计算了主要位于银河系中心区域的170个小麦哲伦云星团(SC)在\emph{g}波段的表面亮度剖面。我们提供了一组均匀的结构参数,通过拟合Elson,Fall\& Freeman(EFF)和King模型。通过对它们的色星等图(CMD)的仔细分析,我们还提供了134个SC子样本的年龄。这是第一次,SMC中如此大的SC样本在它们的大小,亮度和质量方面均匀地表征,扩大了参数空间的探测区域,下降到数百个太阳质量。我们使用这些数据来探索SC的结构参数随时间的演变。特别是,我们确认存在一种物理机制,诱导核心半径增加后0.3 - 1.0 Gyr。我们认为,集群质量可能是驱动内部膨胀的主要参数,因为在这项工作中分析的SC具有$\log (M/M_{\odot}) \leq 3.5$~dex没有经历这样的膨胀。我们还检测到一个质量大小的关系,几乎在整个范围内的SC群众在这里调查。最后,我们的数据表明,在全球范围内的SMC SC系统是动态演变的。

英文摘要:

We derived surface brightness profiles in the \emph{g} band for 170 Small Magellanic Cloud (SMC) star clusters (SCs) mainly located in the central region of the galaxy. We provide a set of homogeneous structural parameters obtained by fitting Elson, Fall \& Freeman (EFF) and King models. Through a careful analysis of their colour-magnitude diagrams (CMDs) we also supply the ages for a subsample of 134 SCs. For the first time, such a large sample of SCs in the SMC is homogeneously characterized in terms of their sizes, luminosities and masses, widening the probed region of the parameter space, down to hundreds of solar masses. We used these data to explore the evolution of the SC's structural parameters with time. In particular, we confirm the existence of a physical mechanism that induces an increase of the core radius after 0.3-1.0 Gyr. We suggest that cluster mass could be the main parameter driving the inner expansion, as none of the SCs having $\log (M/M_{\odot}) \leq 3.5$~dex analysed in this work undergoes to such an expansion. We also detected a mass-size relationship almost over the entire range of SCs masses investigated here. Finally, our data suggest that globally the SMC SC system is dynamically evolved.

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