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arXiv 2102.05464astro-ph.GAastro-ph.SR
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NGC 6357中一个可能的远紫外通量相关核质量函数

A possible far-ultraviolet flux-dependent core mass function in NGC 6357

J. Brand, A. Giannetti, F. Massi, J. G. A. Wouterloot, C. Verdirame

备注：
16 pages, 18 figures, 3 tables (1 only at CDS); accepted by Astronomy & Astrophysics
发表信息：
A&A 647, A154 (2021)
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摘要：

为了推导银河系恒星形成复合体NGC 6357中致密核心的性质，并研究强烈的远紫外辐射场对其性质的影响，我们用JCMT绘制了450和850微米的区域，以及CO（3-2）线。我们还利用了70和160微米的Herschel Hi-GAL数据。我们使用Gaussclumps检索686个嵌入在漫射亚毫米发射中的紧凑核心，并构建了70至850微米的SED，从中我们推导出质量和温度。估计的质量完整性极限为~ 5 Mo。我们将观察到的区域划分为“活跃”区域和“静止”区域，前者暴露于来自三个星团（411个核心）的更大质量成员的远紫外辐射，后者受远紫外辐射影响较小（275个核心）。我们还试图选择一个样本的前恒星核心的基础上互相关与70微米的排放和红色的智慧点源。大多数超过质量完整性极限的核心很可能受到重力束缚。致密岩心中的气体含量很低，为1.4%。发现质量-尺寸关系log（M/Mo）~（2.0-2.4）× log（D/arcsec），取决于样品的精确选择。两个子区域的温度分布明显不同，在静止区的峰值在~ 25 K，在活动区的峰值在~ 35 K。核心质量函数是不同的，以及，在2西格玛水平，一致的Salpeter IMF在静止区和平坦的比在活动区。位于靠近HII区域的致密核心与先前存在的核心逐渐被PDR和光蒸发吞没是一致的。我们把这两个亚区致密核的不同的整体性质归因于远紫外辐射场的影响。

英文摘要：

To derive the properties of the dense cores in the galactic star-forming complex NGC6357 and to investigate the effects of an intense far-UV radiation field on their properties, we mapped the region at 450 and 850 micron, and in the CO(3-2) line with the JCMT. We also made use of the Herschel Hi-GAL data at 70 and 160 micron. We used Gaussclumps to retrieve 686 compact cores embedded in the diffuse sub-mm emission and constructed their SED from 70 to 850 micron, from which we derived mass and temperature. The estimated mass completeness limit is ~5Mo. We divided the observed area in an 'active' region, exposed to the far-UV radiation from the more massive members of three star clusters (411 cores), and a 'quiescent' region, less affected by far-UV radiation (275 cores). We also attempted to select a sample of pre-stellar cores based on cross-correlation with 70 micron emission and red WISE point sources. Most of the cores above the mass completeness limit are likely to be gravitationally bound. The fraction of gas in dense cores is very low, 1.4%. We found a mass-size relation log(M/Mo) ~ (2.0-2.4) x log (D/arcsec), depending on the precise selection of the sample. The temperature distributions in the two sub-regions are clearly different, peaking at ~25K in the quiescent region and at ~35K in the active region. The core mass functions are different as well, at a 2sigma level, consistent with a Salpeter IMF in the quiescent region and flatter than that in the active region. The dense cores lying close to the HII regions are consistent with pre-existing cores being gradually engulfed by a PDR and photoevaporating. We attribute the different global properties of dense cores in the two sub-regions to the influence of the far-UV radiation field.

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