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Deep polarization surveys at low radio frequencies are key to cosmic magnetism studies: Larger catalogs of polarized extragalactic sources and increased precision on Faraday rotation measures (RMs) make it possible to probe the…

Astrophysics of Galaxies · Physics 2025-01-08 S. Piras , C. Horellou , J. Conway , M. Thomasson , T. W. Shimwell , S. P. O'Sullivan , E. Carretti , V. Vacca , A. Bonafede , I. Prandoni

Galaxy clusters are known to host a variety of extended radio sources: tailed radio galaxies whose shape is modelled by the interaction with the intra-cluster medium (ICM); radio bubbles filling cavities in the ICM distribution and rising…

We observe the radio galaxy PKS 1934-63 (at $z=0.1825$) using MUSE (Multi Unit Spectroscopic Explorer) on the Very Large Telescope (VLT). The radio source is GigaHertz Peaked Spectrum and compact (0.13 kpc), implying an early stage of…

Clues to the physical conditions in radio cores of blazars come from measurements of brightness temperatures as well as effects produced by intrinsic opacity. We study the properties of the ultra compact blazar AO 0235+164 with RadioAstron…

We present a 6GHz radio continuum image of the galaxy cluster Abell 2744 ($z = 0.307$) obtained with the Karl G. Jansky Very Large Array (VLA) as part of the VLA Frontier Fields program, whose goal is to explore the radio continuum emission…

Quantifying how the baryonic matter traces the underlying dark matter distribution is key to both understanding galaxy formation and our ability to constrain the cosmological model. Using the cross-correlation function of radio and…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-19 S. N. Lindsay , M. J. Jarvis , K. McAlpine

This paper presents the gamma-ray spectral and timing results from the long-term regular observations of Mrk 421 with the Large Area Telescope (LAT) onboard Fermi during 2008 August - 2023 August. We discerned six periods the relatively…

High Energy Astrophysical Phenomena · Physics 2025-03-05 B. Kapanadze , A. Gurchumelia , M. Aller

This paper is the second in a series in which we present intermediate-resolution spectra for a complete sample of 14 compact radio sources, taken with the aim of investigating the impact of the nuclear activity on the cirumnuclear…

Cosmology and Nongalactic Astrophysics · Physics 2010-11-02 J. Holt , C. N. Tadhunter , R. Morganti

We have investigated the physical conditions in the narrow-line region (NLR) of M51 using long-slit spectra obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope (HST) and 3.6 cm radio continuum…

Astrophysics · Physics 2009-11-10 L. D. Bradley , M. E. Kaiser , W. A. Baan

We present high-sensitivity 1.51 GHz e-MERLIN radio images of the nearby galaxy NGC 6217. We resolve the compact radio source at the centre of NGC 6217 for the first time, finding a twin-lobed structure with a total linear size of ~4 arcsec…

Some merging galaxy clusters host diffuse elongated radio sources, also called radio relics. It is proposed that these radio relics trace shock waves in the intracluster medium created during a cluster merger event. Within the shock waves…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-27 R. J. van Weeren , M. Hoeft , H. J. A. Rottgering , M. Bruggen , H. T. Intema , S. van Velzen

We present new spectroscopic observations of the southern radio galaxy PKS1549-79 (z =0.152).Despite the flat spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and…

Astrophysics · Physics 2009-11-06 C. Tadhunter , K. Wills , R. Morganti , T. Oosterloo , R. Dickson

A Chandra ACIS-S observation of PKS 2152-699 reveals thermal emission from a diffuse region around the core and a hotspot located 10" northeast from the core. This is the first detection of thermal X-ray radiation on kiloparsec scales from…

Astrophysics · Physics 2009-11-10 C. Ly , D. De Young , J. Bechtold

We have measured the angular correlation function of radio sources in the 1.4 GHz NVSS and FIRST surveys. Below ~6 arcminutes w(theta) is dominated by the size distribution of radio galaxies. A model of the size distribution of radio…

Astrophysics · Physics 2009-11-07 R. A. Overzier , H. J. A. Rottgering , R. B. Rengelink , R. J. Wilman

We present deep infrared (Ks band) imaging polarimetry and radio (1.4 and 4.8 GHz) polarimetry of the enigmatic transient Swift J164449.3+573451. This source appears to be a short lived jet phenomenon in a galaxy at redshift z = 0.354,…

We present very long baseline interferometry (VLBI) observations of 179 radio sources in the COSMOS field with extremely high sensitivity using the Green Bank Telescope (GBT) together with the Very Long Baseline Array (VLBA) (VLBA+GBT) at…

Ultra-steep spectrum (USS) radio sources with complex filamentary morphologies are a poorly understood subclass of diffuse radio source found in galaxy clusters. They are characterised by power law spectra with spectral indices less than…

Polarization of radio emission in extragalactic jets at a sub-milliarcsecond angular resolution holds important clues for understanding the structure of the magnetic field in the inner regions of the jets and in close vicinity of the…

The results of the first ever contemporaneous multi-wavelength observation campaign on the BL Lac object PKS2155-304 involving Swift, NuSTAR, Fermi-LAT and H.E.S.S. are reported. The use of these instruments allows us to cover a broad…

High Energy Astrophysical Phenomena · Physics 2020-07-08 H. E. S. S. , Fermi , NuSTAR collaborations

We investigate the feasibility of detecting and probing various components of the ionized intergalactic medium (IGM) and their turbulent properties at radio frequencies through observations of scatter broadening of compact sources. There is…

Cosmology and Nongalactic Astrophysics · Physics 2014-12-01 J. Y. Koay , J. -P. Macquart