威廉·赫歇尔深场中8.4GHz的亚毫米源识别和微Jansky源群
Sub-millimetre source identifications and the micro-Jansky source population at 8.4 GHz in the William Herschel Deep Field
摘要：
[摘要]使用LABOCA对威廉·赫歇尔深场进行的亚毫米观测揭示了2个X射线吸收类星体的可能对应物。这里的目的是利用EVLA成像在8.4 GHz的无线电/亚毫米源建立类星体。减少EVLA数据的挑战是现场存在强4C源。采用一种新的定标算法对数据进行相减，得到了覆盖16'x16'扩展WHDF的热噪声受限射电图。它包含41个高于4 σ极限的源，其中17个具有初级束校正通量。射电观测表明，LABOCA探测到的活动星系核与射电源相吻合，证实了活动星系核X射线吸收后亮度有亚毫米的趋势。这些来源显示出强烈的紫外线过剩（UVX），表明核视线是气体吸收的，而不是灰尘。在剩下的3个在~5'半功率束宽范围内的LABOCA源中，1个被确认为附近星系中的微弱核X射线/射电源，1个是微弱的射电源，1个在任何其他波段都没有被确认。更一般地说，差分射电源计数与以前的观测结果吻合得很好，在S<50 micro-Jy时比纯活动星系核模型有明显的超出。在整个区域，10个比这个极限更暗的源中，6个有光学对应物，其中3个是UVX（即可能的类星体），包括2个吸收类星体LABOCA源。其他微弱的射电对应物不是UVX，但只是稍微少一点蓝色，很可能是恒星形成/合并的星系，主要是在较低的光度和红移。这4个微弱的、光学上无法识别的射电源可能是尘埃遮蔽的类星体或星系。因此，这些高z遮蔽的活动星系核和低z恒星形成群体是解释观测到的过量微弱源计数的主要候选者，因此也是解释先前ARCADE 2实验发现的过量射电背景的主要候选者。
英文摘要：
[Abridged] Sub-mm observations of the William Herschel Deep Field using LABOCA revealed possible counterparts for 2 X-ray absorbed QSOs. The aim here is to exploit EVLA imaging at 8.4 GHz to establish the QSOs as radio/sub-mm sources. The challenge in reducing the EVLA data was the presence of a strong 4C source in the field. A new calibration algorithm was applied to the data to subtract it. The resulting thermal noise limited radio map covers the 16'x16' Extended WHDF. It contains 41 sources above a 4-sigma limit, 17 of which have primary beam corrected flux. The radio observations show that the absorbed AGN with LABOCA detections are coincident with radio sources, confirming the tendency for X-ray absorbed AGN to be sub-mm bright. These sources show strong ultraviolet excess (UVX) suggesting the nuclear sightline is gas- but not dust-absorbed. Of the 3 remaining LABOCA sources within the ~5' half-power beam width, 1 is identified with a faint nuclear X-ray/radio source in a nearby galaxy, 1 with a faint radio source and 1 is unidentified in any other band. More generally, differential radio source counts are in good agreement with previous observations, showing at S<50 micro-Jy a significant excess over a pure AGN model. In the full area, of 10 sources fainter than this limit, 6 have optical counterparts of which 3 are UVX (i.e. likely QSOs) including the 2 absorbed quasar LABOCA sources. The other faint radio counterparts are not UVX but are only slightly less blue and likely to be star-forming/merging galaxies, predominantly at lower luminosities and redshifts. The 4 faint, optically unidentified radio sources may be either dust obscured QSOs or galaxies. These high-z obscured AGN and lower-z star-forming populations are thus the main candidates to explain the observed excess in faint source counts and hence the excess radio background found previously by the ARCADE2 experiment.
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