Hard X-ray selected giant radio galaxies -- II. Morphological evidence of restarted radio activity
G. Bruni, F. Panessa, L. Bassani, D. Dallacasa, T. Venturi, L. Saripalli, M. Brienza, L. Hernández-García, E. Chiaraluce, F. Ursini, A. Bazzano, A. Malizia, P. Ubertini
About 6% of Radio Galaxies (RG) can reach linear sizes larger than 0.7 Mpc, and are then classified as Giant Radio Galaxies (GRG). The conditions that make possible the formation of such big structures is still not clear - either core accretion properties or environmental factors. Recent studies have shown that GRG can be up to four times more abundant in hard X-ray selected (i.e. from INTEGRAL/IBIS and Swift/BAT at >20 keV) RG samples. Moreover, a high fraction of young radio sources found in their cores suggests a recently restarted activity, as suggested from the discrepancy between the measured jet and lobes power, with respect to the one expected from core X-ray luminosity. Here we present a radio morphological study of a sample of 15 hard X-ray selected GRG, discussing low-frequency images from our GMRT campaign complemented with others from the literature: among them, 7/15 show evidence of restarted radio activity either in the form of double-double/X-shaped morphology, or as a cocoon emission embedding more recent jets. This, together with the objects from this sample already found hosting a young radio source in their core, suggests that at least 13 over 15 of these hard X-ray selected GRG show features which are consistent with the possibility of restarted radio activity.
Giant radio galaxies provide important clues into the life cycles and triggering mechanisms of radio jets. With large-scale jets spanning 1.8 Mpc, ESO 422-G028 ($z = 0.038$) is a giant radio galaxy that also exhibits signs of restarted jet activity in the form of pc-scale jets. We present a study of the spatially-resolved stellar and gas properties of ESO 422-G028 using optical integral field spectroscopy from the WiFeS spectrograph. In addition to the majority $\sim 13\,\rm Gyr$ old stellar population, ESO 422-G028 exhibits a much younger ($\lesssim 10\,\rm Myr$ old) component with an estimat…
Comprehensive X-ray Study of Giant Radio Galaxies with XMM-Newton and Chandra
Dayanand Science College（戴亚南德科学学院）；Centre for Space Research, North-West University（西北大学空间研究中心）；Aryabhatta Research Institute of Observational Sciences (ARIES)（阿耶波达观测科学研究所）；National Institute for Theoretical and Computational Sciences (NITheCS)（国家理论与计算科学研究所）
Double-double radio galaxies (DDRGs) represent a short but unique phase in the life-cycle of some of the most powerful radio-loud active galactic nuclei (RLAGN). These galaxies display large-scale remnant radio plasma in the intergalactic medium left behind by a past episode of active galactic nuclei (AGN) activity, and meanwhile, the radio jets have restarted in a new episode. The knowledge of what causes the jets to switch off and restart is crucial to our understanding of galaxy evolution, while it is important to know if DDRGs form a host galaxy dichotomy relative to RLAGN. We utilised the…
We observed the core region of the giant radio galaxy GRS J0844+4627 with e-MERLIN at 1.52 and 5.07 GHz. These observations revealed that the apparent single feature at the centre of GRS J0844+4627, as seen by GMRT, consists of two components separated by 2.7 kpc in projection. Follow-up observations at 1.66 GHz using the EVN unveiled the complex morphologies of the two components. In particular, the south-western component identified with the SDSS J084408.85+462744.2 galaxy morphologically resembles a compact symmetric object (CSO) with a projected linear size of 115 pc. If the CSO hypothesis…
Active galactic nuclei (AGN) at the centres of galaxies can cycle between periods of activity and of quiescence. Characterising the duty-cycle of AGN is crucial for understanding their impact on the evolution of the host galaxy. For radio AGN, their evolutionary stage can be identified from a combination of morphological and spectral properties. We summarise the results we have obtained in the last few years by studying radio galaxies in various crucial phases of their lives, such as remnant and restarted sources. We used morphological information derived from LOw Frequency ARray (LOFAR) image…
In this paper, we test the possibility that the structure of the largest radio galaxy J1420-0545 may have been formed by restarted rather than primary jet activity. This hypothesis was motivated by the unusual morphological properties of the source consisting of two edge-brightened, narrow, highly collinear, and symmetric lobes, thus suggesting an almost ballistic propagation of powerful jets into a particularly low-density external medium. New observations made with the VLA together with the currently available GLEAM and TGSS ADR1 data releases allow the detection of an excess emission at low…
Mrk 1498 is part of a sample of galaxies with extended emission line regions (extended outwards up to a distance of $\sim$7 kpc) suggested to be photo-ionized by an AGN that has faded away or that is still active but heavily absorbed. Interestingly, the nucleus of Mrk 1498 is at the center of two giant radio lobes with a projected linear size of 1.1 Mpc. Our multi-wavelength analysis reveals a complex nuclear structure, with a young radio source (Giga-hertz Peaked Spectrum) surrounded by a strong X-ray nuclear absorption, a mid-infrared spectrum that is dominated by the torus emission, plus a …
We present a new study of the 1.7 Mpc KAT-7-discovered giant radio galaxy, J0133$-$1302, which was carried out using GMRT data at 323 and 608 MHz. This source is located at RA $01^h33^m13^s$ and Dec $-13^{\circ}03^\prime00^{\prime\prime}$ and has a photometric redshift of $\sim$0.3. We discovered unusual morphological properties of the source which include lobes that are exceptionally asymmetric, where the upper lobe is much further from the core when compared to the lower lobe, and a complex structure of the upper lobe. This complex structure of the upper lobe hints at the presence of another…
We have undertaken a systematic study of FRI and FRII radio galaxies with the upgraded Giant Metrewave Radio Telescope (uGMRT) and MeerKAT. The main goal is to explore whether the unprecedented few $μ$Jy sensitivity reached in the range 550-1712 MHz at the resolution of $\sim4^{\prime\prime}-7^{\prime\prime}$ reveals new features in the radio emission which might need us to revise our current classification scheme for classical radio galaxies. In this paper we present the results for the first set of four radio galaxies, i.e. 4C 12.02, 4C 12.03, CGCG 044-046 and CGCG 021-063. The sources have …
SAGAN-VI: When Jets Meet Filaments -- Environmental Imprints on the Growth of Giant Radio Galaxies
Tartu Observatory, University of Tartu（塔尔图大学塔尔图天文台）；Astrophysics Division, National Centre for Nuclear Research（国家核研究中心天体物理部）；Inter-University Centre for Astronomy and Astrophysics (IUCAA)（大学间天文学与天体物理学中心）
Using deep, high-spatial resolution imaging from the HST ACS Coma Cluster Treasury Survey, we determine colour profiles of early-type galaxies in the Coma cluster. From 176 galaxies brighter than $M_\mathrm{F814W(AB)} = -15$ mag that are either spectroscopically confirmed members of Coma or identified by eye as likely members from their low surface brightness, data are provided for 142 early-type galaxies. Typically, colour profiles are linear against $\log(R)$, sometimes with a nuclear region of distinct, often bluer colour associated with nuclear clusters. Colour gradients are determined for…
We study the properties and the origin of the radio emission in the most luminous early-type galaxies (ETGs) in the nearby Universe (MK<-25, recession velocity < 7,500 km/s) as seen by the 150 MHz Low-Frequency ARray (LOFAR) observations. LOFAR images are available for 188 of these giant ETGs (gETGs) and 146 (78%) of them are detected above a typical luminosity of ~10E21 W/Hz. They show a large spread in power, reaching up to ~10E26 W/Hz. We confirm a positive link between the stellar luminosity of gETGs and their median radio power, the detection rate, and the fraction of extended sources. Ab…
We have examined the giant radio galaxy 3C~236 using LOFAR at 143 MHz down to an angular resolution of 7", in combination with observations at higher frequencies. We have used the low frequency data to derive spectral index maps with the highest resolution yet at these low frequencies. We confirm a previous detection of an inner hotspot in the north-west lobe and for the first time observe that the south-east lobe hotspot is in fact a triple hotspot, which may point to an intermittent source activity. Also, the spectral index map of 3C 236 shows that the spectral steepening at the inner region…
Remnant radio galaxies represent an important phase in the life-cycle of radio active galactic nuclei. It is suggested that in this phase, the jets have switched off and the extended emission is fading rapidly. This phase is not well-studied due to the lack of statistical samples observed at both low and high frequencies. In this work, we study a sample of 23 candidate remnant radio galaxies previously selected using the Low Frequency Array at 150 MHz in the Lockman Hole field. We examine their morphologies and study their spectral properties to confirm their remnant nature and revise the morp…
Massive galaxy clusters with cool-cores typically host diffuse radio sources called mini-haloes, whereas, those with non-cool-cores host radio haloes. We attempt to understand the unusual nature of the cool-core galaxy cluster CL1821+643 that hosts a Mpc-scale radio halo using new radio observations and morphological analysis of its intra-cluster medium. We present the Giant Metrewave Radio Telescope (GMRT) 610 MHz image of the radio halo. The spectral index, $α$ defined as $S\propto ν^{-α}$, of the radio halo is $1.0\pm0.1$ over the frequency range of 323 - 610 - 1665 MHz. Archival {\it Chand…
The rich and nearby Coma cluster of galaxies is known to have substructure. We aim to create a more detailed picture of this substructure by searching directly for bound companions around individual giant members. We have used two catalogs of Coma galaxies, one covering the cluster core for a detailed morphological analysis, another covering the outskirts. The separation limit between possible companions (secondaries) and giants (primaries) is chosen as M_B = -19 and M_R = -20, respectively for the two catalogs. We have created pseudo-clusters by shuffling positions or velocities of the primar…
A Morphological Identification and Study of Radio Galaxies from LoTSS DR2. I. The "Winged'' Radio Galaxies
Xiamen University（厦门大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）；Institute of Astronomy, Faculty of Physics, Astronomy and Informatics, NCU（尼古拉·哥白尼大学物理、天文与信息学学院天体物理研究所）；Jadavpur University（贾达普大学）
Transformer-Based Source Detection and Morphological Classification in LOFAR Deep-Field Continuum Images
University of Oxford（牛津大学）；Instituto de Astrofísica de Canarias（加那利天体物理研究所）；Universidad de La Laguna（拉古纳大学）；University of Malta（马耳他大学）；Anqing Normal University（安庆师范大学）；University of Science and Technology of China（中国科学技术大学）
We present the catalogue of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE I). It was generated by cross-matching galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS DR 7) as well as radio sources from the First Images of Radio Sky at Twenty Centimetre (FIRST) and the National Radio Astronomical Observatory VLA Sky Survey (NVSS) catalogues. We created the largest handmade catalogue of visually classified radio objects and associated with them optical host galaxies, containing 32,616 galaxies with a FIRST core within 3 arcsec o…
We present Hubble Space Telescope WFC3-IR imaging in the fields of six apparently bright dusty star-forming galaxies (DSFGs) at $z$ = 2-4 identified by their rest-frame far-infrared colors using the Planck and Herschel space facilities. We detect near-infrared counterparts for all six submillimeter sources, allowing us to undertake strong-lensing analyses. One field in particular stands out for its prominent giant arcs, PLCK G165.7+67.0 (G165). After combining the color and morphological information, we identify 11 sets of image multiplicities in this one field. We construct a strong-lensing m…
Filamentary structures are common morphological features of the cold, molecular interstellar medium (ISM). Recent studies have discovered massive, hundred-parsec-scale filaments that may be connected to the large-scale, Galactic spiral arm structure. Addressing the nature of these Giant Molecular Filaments (GMFs) requires a census of their occurrence and properties. We perform a systematic search of GMFs in the fourth Galactic quadrant and determine their basic physical properties. We identify GMFs based on their dust extinction signatures in near- and mid-infrared and velocity structure probe…
In this Master's project, the X-ray nuclear properties of a sample of bright nearby galaxies are explored. This is done by matching their comprehensive optical spectroscopic classification to the latest available XMM-Newton catalogue - 3XMM-DR4. The good coverage (approx. 38 per cent) ensures that a statistically representative sample is investigated. All nuclear and morphological subsets found within the original sample of 486 galaxies are encompassed, but early-type galaxies and galaxies with optical features characteristic for active galactic nuclei (AGN) are favoured. The results from the …
We present results from an X-ray and radio study of the merging galaxy cluster Abell 115. We use the full set of 5 Chandra observations taken of A115 to date (360 ks total integration) to construct high-fidelity temperature and surface brightness maps. We also examine radio data from the Very Large Array at 1.5 GHz and the Giant Metrewave Radio Telescope at 0.6 GHz. We propose that the high X-ray spectral temperature between the subclusters results from the interaction of the bow shocks driven into the intracluster medium by the motion of the subclusters relative to one another. We have identi…
uGMRT and MeerKAT observation of RXCJ0232-4420: a quiet cluster with a giant radio halo
National Centre for Radio Astrophysics, Tata Institute of Fundamental Research（塔塔基础研究院国家射电天文中心）；International Centre for Theoretical Sciences, Tata Institute of Fundamental Research（塔塔基础研究院国际理论科学中心）；National Radio Astronomy Observatory (NRAO)（国家射电天文台）
Lawrence Livermore National Laboratory（劳伦斯利弗莫尔国家实验室）
Results of the application of pattern recognition techniques to the problem of identifying Giant Radio Sources (GRS) from the data in the NVSS catalog are presented and issues affecting the process are explored. Decision-tree pattern recognition software was applied to training set source pairs developed from known NVSS large angular size radio galaxies. The full training set consisted of 51,195 source pairs, 48 of which were known GRS for which each lobe was primarily represented by a single catalog component. The source pairs had a maximum separation of 20 arc minutes and a minimum component…
Special Astrophysical Observatory of the Russian Academy of Sciences（俄罗斯科学院特别天文台）；Saint Petersburg State University（圣彼得堡国立大学）；Institute for Astronomy, University of Hawaii（夏威夷大学天体物理研究所）；Space Telescope Science Institute（太空望远镜科学研究所）
Radio and X-ray observations of galaxy clusters probe a direct link between cluster mergers and giant radio halos (RH), suggesting that these sources can be used as probes of the cluster merging rate with cosmic time. In this paper we carry out an explorative study that combines the observed fractions of merging clusters (fm) and RH (fRH) with the merging rate predicted by cosmological simulations and attempt to infer constraints on merger properties of clusters that appear disturbed in X-rays and of clusters with RH. We use morphological parameters to identify merging systems and analyze the …
Until recently, relativistic jets were ubiquitously found to be launched from giant elliptical galaxies. However, the detection by the Fermi-LAT of gamma-ray emission from radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxies raised doubts on this relation. Here, we morphologically characterize a sample of 29 RL-NLSy1s (including 12 gamma-ray emitters, gamma-NLSy1s) in order to find clues on the conditions needed by AGN to produce relativistic jets. We use deep near-infrared images from the Nordic Optical Telescope and the ESO VLT to analyze the surface brightness distribution of the galaxies i…
Metal-Poor Gas Accretion Drives Giant Clump Formation at 0.6 < z < 2.6
University of Colorado（科罗拉多大学）；York University（约克大学）；University of California, Davis（加州大学戴维斯分校）；University of California, Merced（加州大学默塞德分校）；Harvard University（哈佛大学）；University of Toronto（多伦多大学）；Dunlap Institute for Astronomy and Astrophysics（邓普勒天文学与天体物理研究所）
Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. In this work we investigate the duty cycle of the radio galaxy B2~0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (~240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. We have combined new LOFAR data at 145 MHz and new SRT data at 6600 MHz with available WSRT data at 1400 MHz to investigate the s…
We present the catalog of Radio sources associated with Optical Galaxies and having Unresolved or Extended morphologies I (ROGUE~I), consisting of 32,616 spectroscopically selected galaxies. It is the largest handmade catalog of this kind, obtained by cross-matching galaxies from the Sloan Digital Sky Survey (SDSS) Data Release 7 and radio sources from both the First Images of Radio Sky at Twenty Centimetre (FIRST) survey and the NRAO VLA Sky Survey \textit{without imposing a limit to the radio flux densities}. The catalog provides a \textit{visual} classification of radio and optical morpholo…
