Based on the ATLBS survey we present a sample of extended radio sources and derive morphological properties of faint radio sources. 119 radio galaxies form the ATLBS-Extended Source Sample (ATLBS-ESS) consisting of all sources exceeding 30" in extent and integrated flux densities exceeding 1 mJy. We give structural details along with information on galaxy identifications and source classifications. The ATLBS-ESS, unlike samples with higher flux-density limits, has almost equal fractions of FR-I and FR-II radio galaxies with a large fraction of the FR-I population exhibiting 3C31-type structures. Significant asymmetry in lobe extents appears to be a common occurrence in the ATLBS-ESS FR-I sources compared to FR-II sources. We present a sample of 22 FR-Is at z>0.5 with good structural information. The detection of several giant radio sources, with size exceeding 0.7 Mpc, at z>1 suggests that giant radio sources are not less common at high redshifts. The ESS also includes a sample of 28 restarted radio galaxies. The relative abundance of dying and restarting sources is indicative of a model where radio sources undergo episodic activity in which an active phase is followed by a brief dying phase that terminates with restarting of the central activity; in any massive elliptical a few such activity cycles wherein adjacent events blend may constitute the lifetime of a radio source and such bursts of blended activity cycles may be repeated over the age of the host. The ATLBS-ESS includes a 2-Mpc giant radio galaxy with the lowest surface brightness lobes known to date.
We present a study of the environments of extended radio sources in the Australia Telescope Low Brightness Survey (ATLBS). The radio sources were selected from the Extended Source Sample (ATLBS-ESS), which is a well defined sample containing the most extended of radio sources in the ATLBS sky survey regions. The environments were analyzed using 4-m CTIO Blanco telescope observations carried out for ATLBS fields in the SDSS ${\rm r}^{\prime}$ band. We have estimated the properties of the environments using smoothed density maps derived from galaxy catalogs constructed using these optical imagin…
We present a radio survey carried out with the Australia Telescope Compact Array. A motivation for the survey was to make a complete inventory of the diffuse emission components as a step towards a study of the cosmic evolution in radio source structure and the contribution from radio-mode feedback on galaxy evolution. The Australia Telescope low-brightness survey (ATLBS) at 1388 MHz covers 8.42 sq deg of the sky in an observing mode designed to yield images with exceptional surface brightness sensitivity and low confusion. The ATLBS radio images, made with 0.08 mJy/beam rms noise and 50" beam…
The Australia Telescope Low-brightness survey (ATLBS; \cite{SESS10}) regions have been mosaic imaged at a radio frequency of 1.4 GHz with $6\arcsec$ angular resolution and 72 $μ$Jy beam$^{-1}$ rms noise. The images (centered at RA: $00^{h}\ 35^{m}\ 00^{s}$, DEC: $-67^{\circ}\ 00^{'}\ 00^{"}$ and RA: $00^{h}\ 59^{m}\ 17^{s}$, DEC: $-67^{\circ}\ 00^{'}\ 00^{"}$ (J2000 epoch)) cover 8.42 square degrees sky area and have no artifacts or imaging errors above the image thermal noise. Multi-resolution radio and optical r-band images (made using the 4-m CTIO Blanco telescope) were used to recognize mu…
The goal of this work is to determine the nature of the relation between morphology and accretion mode in radio galaxies, including environmental parameters. The CoNFIG extended catalogue (improved by new Ks-band identifications and estimated redshifts from UKIDSS, and spectral index measurements from new GMRT observations) is used to select a sub-sample of 206 radio galaxies with z<0.3 over a wide range of radio luminosity, which are morphology-classified using the Fanaroff-Riley (FR) classification of extended radio sources. For each galaxy, spectroscopic data are retrieved to determine the …
We discuss a model of formation of extragalactic radio sources when the parent optical galaxy has a large-scale dipolar magnetic field. The study of dynamics of ejected from the central part of optical galaxy clouds of relativistic particles in dipolar magnetic field gives a possibility to explain main morphological features and physical properties of formed extragalactic radio sources. We bring some results of statistical analyses and correlations between physical parameters for more than 500 radio sources. In appendix we present the data of all used extragalactic radio sources with the refer…
(Abridged) With the largest homogeneous quasar sample with optical spectra and robust radio morphology classifications assembled to date, we investigate quasar radio and optical properties with unprecedented statistical power. The data consist of 4714 radio quasars from FIRST with S_{20}>2mJy and SDSS spectra. Radio morphology classes include core-only (core), core-lobe (lobe), core-jet (jet), lobe-core-lobe (triple), and double-lobe. We examine the optical colors of radio-morphology subsamples and find that radio quasars with core emission unresolved by FIRST (on 5" scale) have a redder color…
The FRI/FRII dichotomy is a much debated issue in the astrophysics of extragalactic radio sources. Study of the properties of HYbrid MOrphology Radio Sources (HYMORS) may bring crucial information and lead to a step forward in understanding the origin of FRI/FRII dichotomy. HYMORS are a rare class of double-lobed radio sources where each of the two lobes clearly exhibits a different FR morphology. This article describes follow-up high resolution VLBA observations of the five discovered by us HYMORS. The main aim of the observations was to answer the questions of whether the unusual radio morph…
We report the high resolution radio observations and their analysis of a radio-loud compact steep spectrum (CSS) quasar FIRST J164311.3+315618, one of the members of a binary system. The second component of the system is a radio-quiet AGN. The projected separation of this pair is 2.3 arcsec (15 kpc) and it is one of the known smallest separation binary quasars. The multi-band images of this binary system made with the Hubble Space Telescope showed that the host galaxy of the radio-loud quasar is highly disturbed. The radio observations presented here were made with the multi-element radio link…
In this paper we consider the possibility that the structure of the largest radio galaxy J1420-0545 is formed by a restarted rather than a primary jet activity. This hypothesis is motivated by the unusual morphological properties of the source, suggesting almost ballistic propagation of powerful jets in a particularly low-density environment. New radio observations of J1420-0545 confirm its morphology consisting of only two narrow lobes; no trace of any outer low-density cavity due to the previous jet activity is therefore detected. Different model fits performed using the newly accessed radio…
We present radio continuum mapping, optical imaging and spectroscopy of the newly discovered double-peaked broad-lined AGN WISE J233237.05-505643.5 at redshift z = 0.3447. This source exhibits an FR-I and FR-II hybrid-morphology, characterized by bright core, jet, and Doppler-boosted lobe structures in ATCA continuum maps at 1.5, 5.6, and 9 GHz. Unlike most FR-II objects, W2332-5056 is hosted by a disk-like galaxy. The core has a projected 5" linear radio feature that is perpendicular to the curved primary jet, hinting at unusual and complex activity within the inner 25 kpc. The multi-epoch op…
Hybrid morphology radio sources are a rare type of radio galaxy that display different Fanaroff-Riley classes on opposite sides of their nuclei. To enhance the statistical analysis of hybrid morphology radio sources, we embarked on a large-scale search of these sources within the international citizen science project, Radio Galaxy Zoo (RGZ). Here, we present 25 new candidate hybrid morphology radio galaxies. Our selected candidates are moderate power radio galaxies (L_median = 4.7x10^{24} W/(Hz sr) at redshifts 0.14<z<1.0. Hosts of nine candidates have spectroscopic observations, of which six …
The sub-mJy radio population is a mixture of active systems, that is star forming galaxies (SFGs) and active galactic nuclei (AGNs). We study a sample of 883 radio sources detected at 1.4 GHz in a deep Very Large Array survey of the Extended Chandra Deep Field South (E-CDFS) that reaches a best rms sensitivity of 6 microJy. We have used a simple scheme to disentangle SFGs, radio-quiet (RQ), and radio-loud (RL) AGNs based on the combination of radio data with Chandra X-ray data and mid-infrared observations from Spitzer. We find that at flux densities between about 30 and 100 microJy the radio …
We investigate the parsec-scale structure of 17 high frequency peaking radio sources from the faint HFP sample. VLBA observations were carried out at two adjacent frequencies, 8.4 and 15.3 GHz, both in the optically-thin part of the spectrum, to obtain the spectral index information. We found that 64% of the sources are resolved into subcomponents, while 36% are unresolved even at the highest frequency. Among the resolved sources, 7 have a morphology and a spectral index distribution typical of young radio sources, while in other 4 sources, all optically associated with quasars, the radio prop…
Hybrid Morphology Radio Sources (HyMoRS) are a class of radio galaxies having the lobe morphology of a Fanaroff-Riley (FR) type I on one side of the active nucleus and of a FR type II on the other. The origin of the different morphologies between FR I and FR II sources has been widely discussed in the past 40 years, and HyMoRS may be the best way to understand whether this dichotomy is related to the intrinsic nature of the source and/or to its environment. However, these sources are extremely rare (<1% of radio galaxies) and only for a few of them a detailed radio study, that goes beyond the …
Extended extragalactic radio sources have traditionally been classified into FR I and II types, based on the ratio r of the separation S between the brightest regions on either sides of the host galaxy and the total size T of the radio source. Here we examine the distribution of various physical properties as a function of r of 1040 luminous radio galaxies (RGs) at z<0.3 from the SDSS, NVSS, and FIRST. About 2/3 of the RGs are lobe-dominated (LD), and 1/3 have prominent jets. If we follow the original definition of the FR types (a division based solely on r), FR I and FR II RGs overlap in thei…
Hybrid sources that present FR I - like jet on the one side of the radio core and FR II - like on the other are rare class of objects that may posses key to understanding the origin of FR division. We presents information connected with the new high resolution VLBA follow-up observations of 5 recently discovered hybrid sources. We believe that sources which exhibit two different morphologies at the opposite side of the radio core are FR II type objects evolving in non-uniform high-density environment.
The so-called double-double structure in radio sources is the most conspicuous signature of their restarted activity. Observations indicate that in the majority of double-double radio sources (DDRS), the span of the radio lobes is larger than 0.7 Mpc. This lower limit is also suggested by theory. However, it seemed likely that the apparent core of B0818+214, a radio galaxy with an overall linear size of its radio structure below that limit, could harbour a compact double well aligned with the outer lobes so that the whole object would fulfil the criteria of a DDRS. Here, we present evidence th…
In the case of an initially conical jet, we study the relation between jet collimation by the external pressure and large-scale morphology. We first consider the important length-scales in the problem, and then carry out axisymmetric hydrodynamic simulations that include, for certain parameters, all these length-scales. We find three important scales related to the collimation region: (i) where the sideways ram-pressure equals the external pressure, (ii) where the jet density equals the ambient density, and (iii) where the forward ram-pressure falls below the ambient pressure. These scales are…
We present a multi-wavelength study of the nature of the SDSS galaxies divided into fine classes based on their morphology, colour and spectral features. The SDSS galaxies are classified into early-type and late-type; red and blue; passive, HII, Seyfert and LINER, which returns a total of 16 fine classes of galaxies. The properties of galaxies in each fine class are investigated from radio to X-ray, using 2MASS, IRAS, FIRST, NVSS, GALEX and ROSAT data. The UV - optical - NIR colours of blue early-type galaxies (BEGs) seem to result from the combination of old stellar population and recent star…
Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGN) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusivel…
We present new more sensitive high-resolution radio observations of a compact broad absorption line (BAL) quasar, 1045+352, made with the EVN+MERLIN at 5 GHz. They allowed us to trace the connection between the arcsecond structure and the radio core of the quasar. The radio morphology of 1045+352 is dominated by a knotty jet showing several bends. We discuss possible scenarios that could explain such a complex morphology: galaxy merger, accretion disk instability, precession of the jet and jet-cloud interactions. It is possible that we are witnessing an ongoing jet precession in this source du…
We present three-dimensional hydrodynamic models of radio galaxies interacting with initially relaxed hot atmospheres and explore the significant off-axis radio lobe structures which result under certain conditions. With a focus on the "winged" and "X-shaped" radio galaxy population, we confirm the importance of observed trends such as the connection of wing formation with jets co-aligned with the major axis of the surrounding atmosphere. These wings are formed substantially by the deflection of lobe plasma flowing back from the hot spots (backflow) and develop in two stages: supersonic expans…
We present 150 MHz, 1.4 GHz, and 3 GHz radio imaging (LoTSS, FIRST and VLASS) and spatially resolved ionized gas characteristics (SDSS IV-MaNGA) for 140 local ($z<0.1$) early-type "red geyser" galaxies. These galaxies have low star formation activity (SFR $\sim \rm 0.01\ M_{\odot} yr^{-1}$), but show unique extended patterns in spatially-resolved emission line maps that have been interpreted as large-scale ionized winds driven by active galactic nuclei (AGN). In this work we confirm that red geysers host low-luminosity radio sources ($\rm L_{1.4GHz} \sim 10^{22} W Hz^{-1}$). Out of 42 radio-de…
Relativistic jets are a common feature of radio loud active galactic nuclei. Multifrequency observations are a unique tool to constrain their physics. We report on a detailed study of the properties of the jet of the nearby BL Lac object PKS 2201+044, one of the rare cases where the jet is detected from radio to X-rays. We use new adaptive optics near-IR observations of the source, obtained with the ESO multi-conjugated adaptive optics demonstrator (MAD) at the Very Large Telescope. These observations acquired in Ground-Layer Adaptive Optics mode are combined with images previously achieved by…
We have carried out Chandra, HST, and VLA observations of four MOJAVE blazars that have been previously classified as 'hybrid' (FR I/II) blazars in terms of radio morphology but not total radio power. The motivation of this study is to determine the X-ray emission mechanism in jets, these being different in FR I and FR II jets. We detected X-ray jet emission with sufficient SNR in two blazars viz. PKS 0215+015 and TXS 0730+504. We carried out spectral energy distribution (SED) modeling of the broad-band emission from the jet regions in these sources and found that a single synchrotron emission…
Zooming in on radio relics -- II. How relic morphology probes density fluctuations at the edge of galaxy clusters
Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；Max-Planck-Institut für Astrophysik（马克斯·普朗克天体物理研究所）；Universität Potsdam（波茨坦大学）；Universität Heidelberg（海德堡大学）
The Odd Radio Circles are newly identified diffuse radio sources at ~1 GHz frequency, with edge-brightened nearly circular morphology, which is remarkably similar to supernova remnants although a physical association with previous population of Galactic supernova remnants is challenging due to detections of the Odd Radio Circles at high Galactic latitudes. Here, a serendipitous identification of a new source in a LOFAR 144 MHz image with similar morphology as that of Odd Radio Circles is reported. This is the first reported identification of an Odd Radio Circle at a very low frequency and with…
We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency GMRT observations and SDSS data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source we find that the inner double is misaligned by $\sim$30$^\circ$ from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity off-set of the two components is 235$\pm$10.5 km s$^{-1}$. The misaligned radio morphology along …
The newly discovered galaxy cluster 1RXS J0603.3+4214 hosts a 1.9 Mpc long, bright radio relic with a peculiar linear morphology. Using hydrodynamical +N-body AMR simulations of the merger between three initially hydrostatic clusters in an idealised setup, we are able to reconstruct the morphology of the radio relic. Based on our simulation, we can constrain the merger geometry, predict lensing mass measurements and X-ray observations. Comparing such models to X-ray, redshift and lensing data will validate the geometry of this complex merger which helps to constrain the parameters for shock ac…
