林德暗星云的AMI观测：异常厘米波发射的进一步证据
AMI observations of Lynds Dark Nebulae: further evidence for anomalous cm-wave emission
摘要：
本文报道了用AMI小天线阵在14.2 ~ 17.9GHz对14个林德暗星云的观测结果，分辨率为2'。这些源是从Visser等人（2001年）的SCUBA观测中选择的，作为与AMI小阵列合成波束很好匹配的小角直径云。比较AMI观测与无线电观测在较低的频率与匹配的UV平面覆盖，以寻找任何异常的过量发射，这可以归因于旋转的尘埃。来自旋转尘埃的可能辐射被确定为在林德暗星云斯库巴位置半径2'内的一个源，相对于低频射电辐射表现出过量。我们发现五个来源，显示可能的旋转尘埃成分在其光谱。这些源在14.2- 17.9GHz频率范围内具有上升的频谱指数。在这五个中，有一个已经被报道过，L1111，我们报告了一个新的明确检测，L 675，和三个新的可能检测（L944，L1103和L1246）。这些检测的相对确定性是根据三个标准进行评估的：排放的程度，排放与水肺位置的一致性以及对过量的替代解释的可能性。扩展的微波发射使得异常发射不太可能是由原恒星或原行星盘的射电对应物引起的。我们使用2'半径是为了与暗星云的IRAS识别（Parker 1988）相一致，我们的第三个标准用于L1103的情况，其中850微米处的高通量密度相对于FIR数据表明发射光谱更复杂。
英文摘要：
Observations at 14.2 to 17.9 GHz made with the AMI Small Array towards fourteen Lynds Dark Nebulae with a resolution of 2' are reported. These sources are selected from the SCUBA observations of Visser et al. (2001) as small angular diameter clouds well matched to the synthesized beam of the AMI Small Array. Comparison of the AMI observations with radio observations at lower frequencies with matched uv-plane coverage is made, in order to search for any anomalous excess emission which can be attributed to spinning dust. Possible emission from spinning dust is identified as a source within a 2' radius of the Scuba position of the Lynds dark nebula, exhibiting an excess with respect to lower frequency radio emission. We find five sources which show a possible spinning dust component in their spectra. These sources have rising spectral indices in the frequency range 14.2--17.9 GHz. Of these five one has already been reported, L1111, we report one new definite detection, L675, and three new probable detections (L944, L1103 and L1246). The relative certainty of these detections is assessed on the basis of three criteria: the extent of the emission, the coincidence of the emission with the Scuba position and the likelihood of alternative explanations for the excess. Extended microwave emission makes the likelihood of the anomalous emission arising as a consequence of a radio counterpart to a protostar or a proto-planetary disk unlikely. We use a 2' radius in order to be consistent with the IRAS identifications of dark nebulae (Parker 1988), and our third criterion is used in the case of L1103 where a high flux density at 850 microns relative to the FIR data suggests a more complicated emission spectrum.
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