We bring out the identity between two ways of defining a single parameter to combine positional & strength asymmetries of extended extragalactic double radio sources associated with active galaxies. Thus, (r.s - 1)/[(1 + r).(1 + s)], combining arm ratio r (defined to be <= 1, i.e., shorter to longer arm) & strength ratio s (in the sense closer to farther, so that it may be <, > or = 1), is identical to -(1/2)[(1 - fr)/(1 + fr) - t], where fr is strength ratio defined >= 1 (i.e., stronger to weaker), & t = +/- (Q - 1)/(Q + 1), +/- signs applying respectively to doubles with closer hotspot fainter & those with closer hotspot brighter, while Q is arm ratio defined >= 1.
Keywords: active galaxies - double radio sources - bilateral symmetry - arm ratio - flux ratio
Asymmetries in Extragalactic Double Radio Sources: Clues from 3D Simulations of Jet - Disc Interaction
河外射电源的观测和理论研究表明，一个不均匀的环境可能是负责观测臂长不对称的喷流和扩展的发射线区域的高红移射电星系的属性。我们进行三维流体动力学模拟的相互作用的强大的河外双极射流与盘状clusius星际介质的对数正态密度分布和分析的不对称性。此外，我们计算射流的不对称性和ISM属性之间的关系，通过蒙特卡罗模拟的基础上通过致密介质的一维传播模型的射流。我们发现，ISM的属性可以与喷射臂长度不对称性的概率分布：磁盘密度和高度被发现有最大的影响不对称性的现实参数范围内，而傅立叶能谱的ISM和湍流马赫数只有较小的影响。流体动力学模拟表明，由于射流及其弓形激波与气体团块的复杂相互作用，不对称性通常可能比1D模型预期的更大，这远远超出了简单的能量处理。根据我们的结果，观测到的中等大小的局域射电星系的不对称性可以用大质量椭圆星系中10^9到10^10太阳质量的气体质量来解释。此外，模拟结果还为观测到的相关性提供了理论基础，即在高红移射电星系中，发射线星云通常在短叶一侧更亮（McCarthy et al. 1991）。喷流与冷气体相的这种相互作用表明，在不断发展的高红移星系中，恒星的形成可能会受到喷流活动的相当大的影响。
Size measurements and characterization of the astrophysical properties of multiple-component radio-AGNs in the ROGUE I catalog
Astronomical Observatory of the Jagiellonian University（雅盖隆大学天文台）；National Center for Nuclear Research（国家核研究中心）；Wits Centre for Astrophysics, School of Physics, University of the Witwatersrand（威特沃特斯兰德大学物理学院天体物理中心）；Department of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University（马萨里克大学理学院理论物理与天体物理学系）；LUX, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS（巴黎天文台，PSL大学，索邦大学，法国国家科学研究中心）；Departamento de Fìsica–CFM, Universidade Federal de Santa Catarina（圣卡塔琳娜联邦大学物理系）；Department of Physics, Indian Institute of Technology Madras（印度金奈理工学院物理系）
Observations of dust-enshrouded evolved stars selected from infrared catalogs requiring high positional accuracy, like infrared spectroscopy or long baseline radio interferometric observations, often require preparational observational steps determining a position with an accuracy much better than 1". Using phase-referencing observations with the Very Large Array at its highest resolution, we have compared the positions of SiO 43 GHz masers in evolved stars, assumed to originate in their infrared detected circumstellar shells, with the positions listed in the MSX, WISE, 2MASS, and Gaia catalog…
Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion of distant extragalactic targets allow us to realize the fundamental celestial reference frame with VLBI observations. However, long-term astrometric monitoring may reveal extreme changes in some AGN positions. Using new VLBI observations in 2018-2021, we show here that four extragalactic radio sources (3C48, CTA21, 1144+352, 1328+254) have a dramatic shift in their positions by 20-130 mill…
By discovering a narrow-line emitter embedded in an extended Ly-alpha nebula, Husemann et al. (2018) found that the luminous radio-quiet quasar LBQS 0302-0019 is a dual active galactic nucleus (AGN) system. By combining available archival radio interferometric data taken at 8.4 GHz with the Very Large Array (VLA), we found that the weak 0.4-mJy radio source in this system positionally coincides with the unobscured optical quasar while its newly discovered obscured companion has no detectable radio emission (<0.045 mJy/beam, 3-sigma image noise level). However, the non-detection of this object …
In this paper, we exploit the gravitational lensing effect to detect proper motion in the highly magnified gravitationally lensed source MG B2016+112. We find positional shifts up to 6 mas in the lensed images by comparing two Very Long Baseline Interferometric (VLBI) radio observations at 1.7 GHz that are separated by 14.359 years, and provide an astrometric accuracy of the order of tens of $μ$as. From lens modelling, we exclude a shift in the lensing galaxy as the cause of the positional change of the lensed images, and we assign it to the background source. The source consists of four sub-c…
New Signs Pointing Toward a Correlation Between Astrophysical Neutrinos and Radio Flares
University of Wisconsin-Madison（威斯康星大学麦迪逊分校）；University of Washington（华盛顿大学）；University of Wisconsin-Whitewater（威斯康星大学惠特沃分校）；University of California, Merced（加州大学默塞德分校）
The X-ray emission mechanism of powerful extragalactic jets, which has important implications for their environmental impact, is poorly understood. The X-ray/radio positional offsets in individual features of jets provide important clues. Extending the previous work in Reddy et al. 2021, we present a detailed comparison between X-ray maps deconvolved using the Low Count Image Reconstruction and Analysis (LIRA) tool and radio maps of 164 components from 77 Chandra-detected X-ray jets. We detect 94 offsets (57%), with 58 new detections. In FR II-type jet knots, the X-rays peak and decay before t…
High-energy astrophysical neutrinos have been observed by several telescopes in the last decade, but their sources still remained unknown. We address the problem of locating astrophysical neutrinos' sources in a statistical manner. We show that blazars positionally associated with IceCube neutrino detections have stronger parsec-scale radio cores than the rest of the sample. The probability of a chance coincidence is only 4*10^-5 corresponding to a significance of 4.1 sigma. We explicitly list four strong radio blazars as highly probable sources of neutrinos above 200 TeV: 3C 279, NRAO 530, PK…
The nature of the ASCA/INTEGRAL source AX J183039-1002: a new Compton-thick AGN?
我们报告的X/软γ射线源AX J183039-1002检测ASCA和INTEGRAL/IBIS的识别。该源的观测通量为8.6 x 10^-11 erg/cm^2/s，在20-100 keV范围内，位于一个弥散射电超新星遗迹（SNR）内，在空间上与一个致密射电源重合。我们分析了钱德拉和XMM-牛顿观测的档案，以确定ASCA/INTEGRAL源。一个点状的钱德拉X射线天体被发现与致密射电源的位置重合，并且在ASCA和INTEGRAL源的误差圆内。虽然致密的射电/X射线源与射电超新星遗迹的关联可能表明脉冲星风星云（PWN），但XMM-牛顿X射线谱与吸收的Seyfert-2活动星系核兼容，因为它提供了约1 keV等效宽度的铁发射线的证据;此外，X射线源谱与其他康普顿厚活动星系核相似，其中<2 keV data are associated to a warm reflector and the >10 keV的辐射源是冷反射体。
We consider a possibility of detecting the jitter effect of apparent celestial positions of distant sources due to local fluctuations of the Galaxy gravitational field. It is proposed to observe two samples of extragalactic sources (target and control) in different sky directions using the high-precision radio interferometry. It is shown that on a scale of ~2 years, it is possible to detect a systematic increase in the standard deviation of measured arc lengths of pairs of target sources compared to the control ones at the $3σ$-level if the accuracy of differential astrometric observations is …
We present a new catalogue of ALMA observations of 3,364 bright, compact radio sources, mostly blazars, used as calibrators. These sources were observed between May 2011 and July 2018, for a total of 47,115 pointings in different bands and epochs. We have exploited the ALMA data to validate the photometry given in the new Planck Multi-frequency Catalogue of Non-thermal sources (PCNT), for which an external validation was not possible so far. We have also assessed the positional accuracy of Planck catalogues and the PCNT completeness limits, finding them to be consistent with those of the Secon…
We report the result of optical identifications of FIRST radio sources with the Hyper Suprime-Cam Subaru Strategic Program survey (HSC-SSP). The positional cross-match within 1" between the FIRST and HSC-SSP catalogs (i ~< 26) produced more than 3600 optical counterparts in the 156 deg^2 of the HSC-SSP field. The matched counterparts account for more than 50% of the FIRST sources in the search field, which substantially exceed previously reported fractions of SDSS counterparts (i ~< 22) of ~30%. Among the matched sample, 9% are optically unresolved sources such as radio-loud quasars. The optic…
We present catalogues of discrete, compact radio sources in and around the discs of 35 edge-on galaxies in the Continuum Halos in Nearby Galaxies -- an EVLA Survey (CHANG-ES). The sources were extracted using the PyBDSF program at both 1.6 GHz (L-band) and 6.0 GHz (C-band) from matching resolution ($\approx$ 3 arcsec) data. We also present catalogues of X-ray sources from Chandra data sets for 27 of the galaxies. The sources at the two radio frequency bands were positionally cross-correlated with each other, and the result cross-correlated with the X-ray sources. All catalogues are included fo…
The Epoch of Reionisation (EoR) is the period within which the neutral universe transitioned to an ionised one. This period remains unobserved using low-frequency radio interferometers which target the 21 cm signal of neutral hydrogen emitted in this era. The Murchison Widefield Array (MWA) radio telescope was built with the detection of this signal as one of its major science goals. One of the most significant challenges towards a successful detection is that of calibration, especially in the presence of the Earth's ionosphere. By introducing refractive source shifts, distorting source shapes…
