A closer look at the deep radio sky: Multi-component radio sources at 3 GHz VLA-COSMOS
A closer look at the deep radio sky: Multi-component radio sources at 3 GHz VLA-COSMOS
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DOI：
10.1051/0004-6361/201832982
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发表时间：
2019-01
影响因子：
6.5
通讯作者：
E. Vardoulaki;E. F. J. Andrade;A. Karim;M. Novak;Sarah K. Leslie;K. Tisanić;V. Smolčić;E. Schinnerer
中科院分区：
文献类型：
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作者：
E. Vardoulaki;E. F. J. Andrade;A. Karim;M. Novak;Sarah K. Leslie;K. Tisanić;V. Smolčić;E. Schinnerer
上下文鉴于目前的大型无线电调查达到了前所未有的深度，我们开始探索过去没有研究过的无线电源群。然而，识别和分类这些大小、形状和物理性质不同的物体正成为一项更加困难的任务。目标。在这篇数据论文中，我们介绍和分析了VLA-COSMOS大型项目中确定的3 GHz（0.75 arcsec分辨率，2.3 μJy波束-1 rms）的多分量射电源，即由两个或多个射电源组成的射电源。方法.将物体分类为多组分是通过从自动代码BLOBCAT识别的10，899个斑点样本中目视检查351个最亮和最长的斑点来完成的。为此，我们使用了该领域的多波长信息，如1.4 GHz VLA-COSMOS数据和超深调查与VISTA望远镜（UltraVISTA）堆叠马赛克可用于COSMOS。结果我们已经确定了67个多分量无线电源在3 GHz：58个源与活动星系核（AGN）供电的无线电发射和9个恒星形成星系。我们报告了八个新的检测，没有观察到的VLA-COSMOS大型项目在1.4 GHz，由于在3 GHz的覆盖面积略大。增加的空间分辨率为0.75角秒，使我们能够解决（和隔离）多个发射峰的28个扩展的无线电源没有确定在1.4 GHz的VLA-COSMOS地图。我们报告的多频率通量密度（324兆赫，325兆赫，1.4千兆赫和3千兆赫），星星的形成率，和这些对象的恒星质量。我们发现，在3 GHz的VLA-COSMOS的多组分对象居住主要是大质量星系（> 1010.5 M）。大多数的多成分活动星系核位于恒星形成星系（SFG）的主序列之下，在绿色谷和静止区。此外，我们提供了详细的描述对象，并发现在活动星系核中有两个头-尾，10个核瓣，9个广角尾（WAT），8个双-双或Z-/X-形，3个双尾射电源，和26个对称源，而在SFG中，我们发现唯一的恒星形成环的射电辐射在宇宙中看到。此外，我们还报道了大量（58个中的32个）扰动/弯曲多分量活动星系核，其中18个不属于COSMOS的X射线群（红移范围0.08 ≤ z < 1.53）。结论3 GHz VLA-COSMOS数据集的高角分辨率和灵敏度使我们有机会确定多组分物体的特殊射电结构和子结构，并将它们与活动星系核或恒星形成星系等物理现象联系起来。这项研究说明了μJy射电源群的复杂性;在3 GHz VLA-COSMOS的灵敏度和分辨率下，活动星系核和SFG的射电结构都发射射电连续辐射，在没有清晰对称喷流的情况下变得相当。因此，在许多情况下，仅仅使用射电观测来解开活动星系核和SFG的贡献可能会产生误导。这对今后的调查有影响，例如通过平方公里阵列和前体进行的调查，这些调查将查明数十万个多组成物体。
Context. Given the unprecedented depth achieved in current large radio surveys, we are starting to probe populations of radio sources that have not been studied in the past. However, identifying and categorising these objects, differing in size, shape and physical properties, is becoming a more difficult task. Aims. In this data paper we present and characterise the multi-component radio sources identified in the VLA-COSMOS Large Project at 3 GHz (0.75 arcsec resolution, 2.3 μJy beam−1 rms), i.e. the radio sources which are composed of two or more radio blobs. Methods. The classification of objects into multi-components was done by visual inspection of 351 of the brightest and most extended blobs from a sample of 10,899 blobs identified by the automatic code BLOBCAT. For that purpose we used multi-wavelength information of the field, such as the 1.4 GHz VLA-COSMOS data and the Ultra Deep Survey with the VISTA telescope (UltraVISTA) stacked mosaic available for COSMOS. Results. We have identified 67 multi-component radio sources at 3 GHz: 58 sources with active galactic nucleus (AGN) powered radio emission and nine star-forming galaxies. We report eight new detections that were not observed by the VLA-COSMOS Large Project at 1.4 GHz, due to the slightly larger area coverage at 3 GHz. The increased spatial resolution of 0.75 arcsec has allowed us to resolve (and isolate) multiple emission peaks of 28 extended radio sources not identified in the 1.4 GHz VLA-COSMOS map. We report the multi-frequency flux densities (324 MHz, 325 MHz, 1.4 GHz & 3 GHz), star formation rates, and stellar masses of these objects. We find that multi-component objects at 3 GHz VLA-COSMOS inhabit mainly massive galaxies (> 1010.5 M⊙). The majority of the multi-component AGN lie below the main sequence of star-forming galaxies (SFGs), in the green valley and the quiescent region. Furthermore, we provide detailed descriptions of the objects and find that amongst the AGN there are two head-tail, ten core-lobe, nine wide-angle-tail (WAT), eight double-double or Z-/X-shaped, three bent-tail radio sources, and 26 symmetric sources, while amongst the SFGs we find the only star-forming ring seen in radio emission in COSMOS. Additionally, we report a large number (32 out of 58) of disturbed/bent multi-component AGN, 18 of which do not lie within X-ray groups in COSMOS (redshift range 0.08 ≤ z < 1.53). Conclusion. The high angular resolution and sensitivity of the 3 GHz VLA-COSMOS data set give us the opportunity to identify peculiar radio structures and sub-structures of multi-component objects, and relate them to physical phenomena such as AGN or star-forming galaxies. This study illustrates the complexity of the μJy radio-source population; at the sensitivity and resolution of 3 GHz VLA-COSMOS, the radio structures of AGN and SFG both emitting radio continuum emission, become comparable in the absence of clear, symmetrical jets. Thus, disentangling the AGN and SFG contributions using solely radio observations can be misleading in a number of cases. This has implications for future surveys, such as those done by square kilometre array (SKA) and precursors, which will identify hundreds of thousands of multi-component objects.