Search for massive protostar candidates in the southern hemisphere. II. Dust continuum emission
Search for massive protostar candidates in the southern hemisphere. II. Dust continuum emission
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DOI：
10.1051/0004-6361:20053999
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发表时间：
2005-10
影响因子：
6.5
通讯作者：
M. Beltrán;J. Brand;R. Cesaroni;F. Fontani;S. Pezzuto;L. Testi;S. Molinari
中科院分区：
文献类型：
--
作者：
M. Beltrán;J. Brand;R. Cesaroni;F. Fontani;S. Pezzuto;L. Testi;S. Molinari
在一个持续的努力，以确定和研究高质量的原恒星候选人，我们已经观察到在各种示踪剂的样本235源选择从IRAS点源目录，主要是$\delta低源和93高，这被认为是在不同的演化阶段。通过比较它们的物理性质和形态，对这两种子样品进行了详细的研究。除了8个区域外，其他所有区域都检测到了大量的尘埃团块，每个区域通常不止一个团块。沙尘暴的释放呈现出多种复杂的形态，有时多团形成丝状或团簇。当尘埃温度T_{\rmd} = 30$ K，H2密度为9.510^5 $ cm-3，表面密度为0.4 g cm-2时，平均团簇的线性尺寸为0.5$ pc，质量为320 M_\odot$。中位值分别为0.4pc、102 × 104 cm-3、44 × 104 cm-3和0.14g cm-2。发光度与质量比的平均值$L/M \simeq 99~L_\odot/M_\odot $表明这些源处于年轻的、超致密前的Hii阶段。我们比较了毫米连续谱图与中红外MSX发射的图像，并发现了95个巨大的毫米团块非MSX发射器，无论是扩散或点状，这是潜在的星前或前集群核心。这些团块的物理性质与其他团块相似，除了质量比MSX对应物的团块低约3倍。这种差异可能是由于潜在的星前团块具有较低的尘埃温度。质量超过$M \sim 100~M\odot$的团块的质谱最符合幂律d$N/{\rm d}M \propto M^{-\alpha}$，其中$\alpha = 2.1$，与Salpeter（1955）恒星IMF一致，其中$\alpha=2.35$。另一方面，质量为10 ~M_\odot\la M \la 120~M_\odot$的团块的质量函数更好地符合斜率为$\alpha = 1.5$的幂律，与气体观测得到的分子云的质量函数更一致。
In an ongoing effort to identify and study high-mass protostellar candidates we have observed in various tracers a sample of 235 sources selected from the IRAS Point Source Catalog, mostly with $\delta Low sources and 93 High , which are believed to be in different evolutionary stages. Both sub-samples have been studied in detail by comparing their physical properties and morphologies. Massive dust clumps have been detected in all but 8 regions, with usually more than one clump per region. The dust emission shows a variety of complex morphologies, sometimes with multiple clumps forming filaments or clusters. The mean clump has a linear size of ~$ 0.5$ pc, a mass of ~$ 320~M_\odot$ for a dust temperature $T_{\rm d} = 30$ K, an H 2 density of $9.5\times10^5$ cm -3 , and a surface density of 0.4 g cm -2 . The median values are 0.4 pc, $102~M_\odot$, $4\times10^4$ cm -3 , and 0.14 g cm -2 , respectively. The mean value of the luminosity-to-mass ratio, $L/M \simeq 99~L_\odot/M_\odot$, suggests that the sources are in a young, pre-ultracompact Hii phase. We have compared the millimeter continuum maps with images of the mid-IR MSX emission, and have discovered 95 massive millimeter clumps non-MSX emitters, either diffuse or point-like, that are potential prestellar or precluster cores. The physical properties of these clumps are similar to those of the others, apart from the mass that is ~3 times lower than for clumps with MSX counterpart. Such a difference could be due to the potential prestellar clumps having a lower dust temperature. The mass spectrum of the clumps with masses above $M \sim 100~M_\odot$ is best fitted with a power-law d$N/{\rm d}M \propto M^{-\alpha}$ with $\alpha = 2.1$, consistent with the Salpeter (1955) stellar IMF, with $\alpha=2.35$. On the other hand, the mass function of clumps with masses $10~M_\odot\la M \la 120~M_\odot$ is better fitted with a power law of slope $\alpha = 1.5$, more consistent with the mass function of molecular clouds derived from gas observations.