The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). IV. Free–Free Emission from Protostars: Links to Infrared Properties, Outflow Tracers, and Protostellar Disk Masses
The VLA Nascent Disk and Multiplicity Survey of Perseus Protostars (VANDAM). IV. Free–Free Emission from Protostars: Links to Infrared Properties, Outflow Tracers, and Protostellar Disk Masses
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DOI：
10.3847/1538-4365/aaceae
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发表时间：
2018-06
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通讯作者：
Ł. Tychoniec;J. Tobin;A. Karska;C. Chandler;M. Dunham;R. Harris;K. Kratter;Zhi-Yun Li;L. Looney;C. Melis;L. P'erez;S. Sadavoy;D. Segura-Cox;E. V. van Dishoeck
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作者：
Ł. Tychoniec;J. Tobin;A. Karska;C. Chandler;M. Dunham;R. Harris;K. Kratter;Zhi-Yun Li;L. Looney;C. Melis;L. P'erez;S. Sadavoy;D. Segura-Cox;E. V. van Dishoeck
原恒星在厘米射电波长的发射已被证明跟踪由原恒星驱动的喷流和流出的电离冲击所产生的自由-自由发射。因此，在无线电频率上测量原恒星的性质可以为了解其流出和喷流的性质提供有价值的见解。作为VLA新生圆盘和多重性(Vandam)调查的一部分，我们提出了一项C波段(4.1和6.4厘米)调查，对英仙座所有已知的原恒星(0类和I类)进行了调查。对于我们的样本，我们检验了射电流量密度和原恒星参数之间的已知相关性，例如测辐射光度和流出力。我们还研究了射电通量密度与赫歇尔远红外线亮度之间的关系。我们发现自由-自由辐射很可能起源于J型激波；然而，大的散射表明这两种类型的辐射探测不同的时间和空间尺度。使用C波段通量，我们从相应的Ka波段(9 Mm)通量密度中去掉了对自由污染的估计，该密度主要探测嵌入磁盘的粉尘排放。我们发现，与0类源(248M⊕)相比，I类源(中位数粉尘质量96M⊕)的致密(<；1“)粉尘排放较低，但比II类源(5-15 M⊕)高几倍。如果这种致密的尘埃排放主要是跟踪嵌入的圆盘，就像许多来源可能的那样，这一结果提供了证据，证明随着原恒星的演化，圆盘质量减少，早期有足够的质量主要形成巨大的行星核心。
Emission from protostars at centimeter radio wavelengths has been shown to trace the free–free emission arising from ionizing shocks as a result of jets and outflows driven by protostars. Therefore, measuring properties of protostars at radio frequencies can provide valuable insights into the nature of their outflows and jets. We present a C-band (4.1 and 6.4 cm) survey of all known protostars (Class 0 and Class I) in Perseus as part of the VLA Nascent Disk and Multiplicity (VANDAM) Survey. We examine the known correlations between radio flux density and protostellar parameters, such as bolometric luminosity and outflow force, for our sample. We also investigate the relationship between radio flux density and far-infrared line luminosities from Herschel. We show that free–free emission most likely originates from J-type shocks; however, the large scatter indicates that those two types of emission probe different time and spatial scales. Using C-band fluxes, we removed an estimation of free–free contamination from the corresponding Ka-band (9 mm) flux densities that primarily probe dust emission from embedded disks. We find that the compact (<1″) dust emission is lower for Class I sources (median dust mass 96 M⊕) relative to Class 0 (248 M⊕), but several times higher than in Class II (5–15 M⊕). If this compact dust emission is tracing primarily the embedded disk, as is likely for many sources, this result provides evidence of decreasing disk masses with protostellar evolution, with sufficient mass for forming giant planet cores primarily at early times.