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arXiv 2402.09405astro-ph.GA
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物理条件对恒星初始质量函数的影响:低金属度恒星形成区 Sh 2-209

Effects of physical conditions on the stellar initial mass function: The low-metallicity star-forming region Sh 2-209

Marie Zinnkann, Henriette Wirth, Pavel Kroupa

AI总结:

本文研究低金属度 HII 区 S209 的两个星团,通过银心距、密度和半质量半径等检验物理条件对 IMF 的影响,结果支持低金属度形成更致密星团及顶端偏重 IMF。

摘要:

近期研究表明,恒星初始质量函数(IMF)的变化取决于物理条件,尤其是金属度和气体密度。我们基于最近推导得到的 IMF,研究了低金属度 HII 区 Sh 2-209(S209)中两个星团的性质,即主星团(MC)和子星团(SC)。我们利用以往观测检验了三个此前已发表的相关关系:IMF 的顶端偏重程度对金属度的依赖、半质量半径,以及最大质量恒星对嵌入星团恒星质量的依赖。对于该区域,研究考虑了两个不同的银心距,即 10.5 kpc 和 18 kpc;在假设银心距为 18 kpc 时发现,此前确定的 IMF 存在年龄—距离简并,以使其与其他已建立的、依赖金属度和密度的 IMF 保持一致。在 S209 中,年龄为 0.5 Myr 的 MC 所确定的半质量半径为(0.080 ± 0.005)pc,嵌入星团密度为(0.2 ± 0.1)×10^6 Msun pc^-3,这支持了以下假设:低金属度环境会产生更致密的星团,从而导致顶端偏重的 IMF。因此,全部三项检验均与此前发表的相关关系一致。S209 的结果被置于小麦哲伦云恒星形成区 NGC 346 中贫金属星团的 IMF 测定这一背景下进行比较。

英文摘要:

Recent work suggested that the variation of the initial mass function (IMF) of stars depends on the physical conditions, notably, the metallicity and gas density. We investigated the properties of two clusters, namely the main cluster (MC) and the subcluster (SC), in the low-metallicity HII region Sh 2-209 (S209) based on recently derived IMFs. We tested three previously published correlations using previous observations: the top-heaviness of the IMF in dependence on metallicity, the half-mass radius, and the most massive star in dependence on the stellar mass of the embedded clusters. For this region, two different galactocentric distances, namely 10.5 kpc and 18 kpc, were considered, where an age-distance-degeneracy was found for the previously determined IMF to be consistent with other formulated metallicity and density dependent IMFs. The determined half-mass radius (0.080 +/- 0.005) pc and the embedded cluster density (0.2 +/- 0.1) 10^6 Msun pc^-3 for the MC with an age of 0.5 Myr in S209 assuming a galactocentric distance of 18 kpc support the assumption that a low-metallicity environment results in a denser cluster, which leads to a top-heavy IMF. Thus, all three tests are consistent with the previously published correlations. The results for S209 are placed in the context with the IMF determination within the metal-poor cluster in the star-forming region NGC 346 in the Small Magellanic Cloud.

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