IRDC G351.77-0.53基准研究：Gaia DR3距离、质量分布与恒星形成含量
Benchmarking the IRDC G351.77-0.53: Gaia DR3 distance, mass distribution, and star formation content
AI总结：
本研究通过Gaia DR3视差、Herschel气体质量图与YSO统计，确定纤维状IRDC G351的距离、质量分布及恒星形成效率，发现其显著低于Orion A和局地关系。
摘要：
尽管红外暗云（IRDC）已得到深入研究，但其恒星形成（SF）与近邻云相比究竟如何仍不清楚。我们研究G351.77-0.53（以下简称G351），这是一个形成星团的纤维状IRDC。我们首先表征其年轻恒星天体（YSO）含量。基于可能成员的平均视差，我们得到约2.0±0.14 kpc的Gaia距离，解决了文献中的距离歧义。利用由Herschel得到的N(H₂)图，我们测得总气体质量为10200 M⊙（在11 pc²范围内），以及整条纤维的平均线质量轮廓，并将其建模为λ≈1660 (w/pc)^0.62 M⊙ pc⁻¹。在w<0.63 pc时，我们的λ轮廓高于Orion A及其大多数子结构中提取的λ轮廓，并且具有更陡的幂律指数。基于纤维区域内的YSO，我们估算恒星形成效率（SFE）和恒星形成率（SFR）。相对于Orion A的Spitzer巡天，我们计算出YSO目录存在5倍的不完备性修正。G351的SFE比Orion A低约1.8倍，也低于局地云的中值。我们测量SFR和气体质量以估算每自由下落时间效率ε_ff。我们发现ε_ff比先前提出的局地平均关系低约1.1 dex，比Orion A低约4.7倍。这些观测表明，局地SF关系并不能捕捉银河系中存在的变化。我们推测云的年轻程度和/或磁场可能解释G351的低效率。
英文摘要：
While intensively studied, it remains unclear how the star formation (SF) in Infrared Dark Clouds (IRDCs) compares to that of nearby clouds. We study G351.77-0.53 (henceforth G351), a cluster-forming filamentary IRDC. We begin by characterizing its young stellar object (YSO) content. Based on the average parallax of likely members, we obtain a Gaia distance of $\sim\,2.0\pm0.14$ kpc, resolving the literature distance ambiguity. Using our Herschel-derived N(H$_2$) map, we measure a total gas mass of 10200 M$_{\odot}$ (within 11 pc$^2$) and the average line-mass profile of the entire filament, which we model as $λ=~1660 (w/\rm pc )^{0.62}\,\,M_{\odot}\,\rm{pc}^{-1}$. At $w < 0.63$ pc, our $λ$ profile is higher and has a steeper power-law index than $λ$ profiles extracted in Orion A and most of its substructures. Based on the YSOs inside the filament area, we estimate the SF efficiency (SFE) and SF rate (SFR). We calculate a factor of 5 incompleteness correction for our YSO catalog relative to Spitzer surveys of Orion A. The G351 SFE is $\sim 1.8$ times lower than that of Orion A and lower than the median value for local clouds. We measure SFR and gas masses to estimate the efficiency per free-fall time, $ε_{\rm ff}$. We find that $ε_{\rm ff}$ is $\sim$ 1.1 dex below the previously proposed mean local relation, and $\sim\,4.7\times$ below Orion A. These observations indicate that local SF-relations do not capture variations present in the Galaxy. We speculate that cloud youth and/or magnetic fields might account for the G351 inefficiency.
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