High-resolution VLA observations of FR0 radio galaxies: the properties and nature of compact radio sources
High-resolution VLA observations of FR0 radio galaxies: the properties and nature of compact radio sources
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FR0 射电星系的高分辨率 VLA 观测：紧凑射电源的特性和性质
DOI：
10.1093/mnras/sty2703
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发表时间：
2018
影响因子：
4.8
通讯作者：
Baldi R
中科院分区：
文献类型：
--
作者：
Baldi R
本文介绍了Karl G. Jansky甚大阵列（VLA）观测有关FR 0射电星系的性质，与早期型星系有关的致密射电源，代表了活动星系核的大部分局部射电大声人口。我们从FR 0 CAT样本中获得了18个FR 0的1.5，4.5和7.5 GHz的A阵列观测：这些是< 0.05的源，在FIRST图像中无法分辨，光谱分类为低激发星系（LEG）。虽然我们达到了0.3角秒的角分辨率，但18个FR 0中的大多数仍然没有得到解决。只有四个物体显示出扩展发射。六个有陡峭的无线电频谱，11个有平坦的核心，而一个显示出倒置的频谱。我们发现，（i）FR 0的核心和总排放量之间的比率是FRI的2.30倍，（ii）从核和宿主的角度来看，FR 0具有与FRI相同的性质。FR 0与FRI的区别仅在于缺乏扩展的无线电发射。对各种演变设想进行了研究：（一）所有FR 0都是年轻源，最终演变成扩展源的可能性被射电大小的分布所排除;（二）同样，一种依赖时间的设想，即吸积或喷流发射的变化阻止了大规模射电结构的形成，由于千秒差距以下天体的大量存在，似乎是不可信的;（iii）FR 0由轻度相对论性喷流产生的情景与数据一致，但如果要进行适当的测试，则需要对更大样本进行观测。
We present the results of Karl G. Jansky Very Large Array (VLA) observations regarding the properties of FR0 radio galaxies, the compact radio sources associated with early-type galaxies that represent the bulk of the local radio-loud population of active galactic nuclei. We obtained A-array observations at 1.5, 4.5 and 7.5 GHz for 18 FR0s from the FR0CATsample: these are sources at< 0.05, which are unresolved in the FIRST images and spectroscopically classified as low-excitation galaxies (LEGs). Although we reach an angular resolution of ∼0.3 arcsec, the majority of the 18 FR0s are still unresolved. Only four objects show extended emission. Six have steep radio spectra, 11 have flat cores, while one shows an inverted spectrum. We find that (i) the ratio between the core and total emission in FR0s is ∼30 times higher than that in FRIs, and (ii) FR0s have the same properties as FRIs from the nuclear and host points of view. FR0s differ from FRIs only in the paucity of extended radio emission. Various evolutionary scenarios were investigated: (i) the possibility that all FR0s are young sources eventually evolving into extended sources was ruled out by the distribution of radio sizes; (ii) similarly, a time-dependent scenario, in which a variation of accretion or jet launching prevents the formation of large-scale radio structures, appears to be implausible owing to the large abundance of subkiloparsec objects; (iii) a scenario in which FR0s are produced by mildly relativistic jets is consistent with the data but requires observations of a larger sample if it is to be properly tested.
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