哈勃空间望远镜对三个边缘大质量YSO的NICMOS偏振观测
Hubble Space Telescope NICMOS Polarization Observations of Three Edge-on Massive YSOs
摘要：
大质量的年轻恒星天体（YSO），像低质量的YSO一样，似乎被光学厚的信封和/或磁盘包围，并有区域，通常是双极的，在近红外波长的偏振散射光中可以看到。我们正在使用哈勃太空望远镜上的NICMOS的0.2“空间分辨率来检查在太阳几千秒差距内的恒星形成区域中的大质量YSO的盘和流出区域的结构。在这里，我们报告2微米旋光的NGC 6334 V和S255 IRS 1。NGC 6334 V由一个双叶明亮的反射星云组成，与黑暗区域相对，可能是一个光学厚分子云。我们的偏振测量表明，照亮的恒星位于连接两个叶的线以南约2“;我们在2微米处没有探测到这颗恒星，但在这个位置有一个小的射电源和一个中红外源。S255 IRS 1由两颗YSO（NIRS 1和NIRS 3）组成，它们有重叠的散射光瓣和亮度，对应于早期的B星。IRS 1中包括一个星团，我们通过它的偏振来确定局部磁场方向。两个YSO的散射光瓣都不与该磁场对准。连接NIRS 1散射光瓣的直线绕着恒星对称地扭曲;最好的解释是，这颗恒星是一颗近距离双星的一部分，而NIRS 1的外流轴是由于非共面的盘和轨道而进动的。恒星NIRS 3也偏离了连接其两个散射光瓣的直线。我们认为，所有三个YSO显示证据的情节喷射的物质，因为它们从致密的，光学厚信封吸积。
英文摘要：
Massive young stellar objects (YSOs), like low-mass YSOs, appear to be surrounded by optically thick envelopes and/or disks and have regions, often bipolar, that are seen in polarized scattered light at near-infrared wavelengths. We are using the 0.2'' spatial resolution of NICMOS on Hubble Space Telescope to examine the structure of the disks and outflow regions of massive YSOs in star-forming regions within a few kpc of the Sun. Here we report on 2 micron polarimetry of NGC 6334 V and S255 IRS1. NGC 6334 V consists of a double-lobed bright reflection nebula seen against a dark region, probably an optically thick molecular cloud. Our polarization measurements show that the illuminating star lies ~ 2'' south of the line connecting the two lobes; we do not detect this star at 2 micron, but there are a small radio source and a mid-infrared source at this location. S255 IRS1 consists of two YSOs (NIRS1 and NIRS3) with overlapping scattered light lobes and luminosities corresponding to early B stars. Included in IRS1 is a cluster of stars from whose polarization we determine the local magnetic field direction. Neither YSO has its scattered light lobes aligned with this magnetic field. The line connecting the scattered light lobes of NIRS1 is twisted symmetrically around the star; the best explanation is that the star is part of a close binary and the outflow axis of NIRS1 is precessing as a result of non-coplanar disk and orbit. The star NIRS3 is also offset from the line connecting its two scattered light lobes. We suggest that all three YSOs show evidence of episodic ejection of material as they accrete from dense, optically thick envelopes.
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