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1. On the Fast Radio Burst and Persistent Radio Source Populations

   https://doi.org/10.3847/1538-4357/ac4c42  

   Law, Casey J.; Connor, Liam; Aggarwal, Kshitij (March 2022, The Astrophysical Journal)

   Abstract The first fast radio burst (FRB) to be precisely localized was associated with a luminous persistent radio source (PRS). Recently, a second FRB/PRS association was discovered for another repeating source of FRBs. However, it is not clear what makes FRBs or PRS or how they are related. We compile FRB and PRS properties to consider the population of FRB/PRS sources. We suggest a practical definition for PRS as FRB associations with luminosity greater than 10²⁹erg s⁻¹Hz⁻¹that are not attributed to star formation activity in the host galaxy. We model the probability distribution of the fraction of FRBs with PRS for repeaters and nonrepeaters, showing there is not yet evidence for repeaters to be preferentially associated with PRS. We discuss how FRB/PRS sources may be distinguished by the combination of active repetition and an excess dispersion measure local to the FRB environment. We use CHIME/FRB event statistics to bound the mean per-source repetition rate of FRBs to be between 25 and 440 yr⁻¹. We use this to provide a bound on the density of FRB-emitting sources in the local universe of between 2.2 × 10²and 5.2 × 10⁴Gpc⁻³assuming a pulsar-like beamwidth for FRB emission. This density implies that PRS may comprise as much as 1% of compact, luminous radio sources detected in the local universe. The cosmic density and phenomenology of PRS are similar to that of the newly discovered, off-nuclear “wandering” active galactic nuclei (AGN). We argue that it is likely that some PRS have already been detected and misidentified as AGN. 

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2. Radio Galaxy Zoo: The Distortion of Radio Galaxies by Galaxy Clusters

   https://doi.org/10.3847/1538-3881/aaff62  

   Garon, Avery F.; Rudnick, Lawrence; Wong, O. Ivy; Jones, Tom W.; Kim, Jin-Ah; Andernach, Heinz; Shabala, Stanislav S.; Kapińska, Anna D.; Norris, Ray P.; de Gasperin, Francesco; et al (March 2019, The Astronomical Journal)
3. Radio Galaxy Zoo: new giant radio galaxies in the RGZ DR1 catalogue

   https://doi.org/10.1093/mnras/staa2805  

   Tang, H; Scaife, A M; Wong, O I; Kapińska, A D; Rudnick, L; Shabala, S S; Seymour, N; Norris, R P (October 2020, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT In this paper, we present the identification of five previously unknown giant radio galaxies (GRGs) using Data Release 1 of the Radio Galaxy Zoo citizen science project and a selection method appropriate to the training and validation of deep learning algorithms for new radio surveys. We associate one of these new GRGs with the brightest cluster galaxy (BCG) in the galaxy cluster GMBCG J251.67741+36.45295 and use literature data to identify a further 13 previously known GRGs as BCG candidates, increasing the number of known BCG GRGs by $$\gt 60$$ per cent. By examining local galaxy number densities for the number of all known BCG GRGs, we suggest that the existence of this growing number implies that GRGs are able to reside in the centres of rich (∼1014 M⊙) galaxy clusters and challenges the hypothesis that GRGs grow to such sizes only in locally underdense environments. 

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4. The radio spectral turnover of radio-loud quasars at z > 5

   https://doi.org/10.1051/0004-6361/202142489  

   Shao, Yali; Wagg, Jeff; Wang, Ran; Momjian, Emmanuel; Carilli, Chris L.; Walter, Fabian; Riechers, Dominik A.; Intema, Huib T.; Weiss, Axel; Brunthaler, Andreas; et al (March 2022, Astronomy & Astrophysics)

   We present Karl G. Jansky Very Large Array S - (2–4 GHz), C - (4–8 GHz), and X -band (8–12 GHz) continuum observations toward seven radio-loud quasars at z  > 5. This sample has previously been found to exhibit spectral peaks at observed-frame frequencies above ∼1 GHz. We also present upgraded Giant Metrewave Radio Telescope (uGMRT) band-2 (200 MHz), band-3 (400 MHz), and band-4 (650 MHz) radio continuum observations toward eight radio-loud quasars at z  > 5, selected from our previous GMRT survey, in order to sample their low-frequency synchrotron emission. Combined with archival radio continuum observations, all ten targets show evidence for spectral turnover. The turnover frequencies are ∼1–50 GHz in the rest frame, making these targets gigahertz-peaked-spectrum or high-frequency-peaker candidates. For the nine well-constrained targets with observations on both sides of the spectral turnover, we fit the entire radio spectrum with absorption models associated with synchrotron self-absorption and free-free absorption (FFA). Our results show that FFA in an external inhomogeneous medium can accurately describe the observed spectra for all nine targets, which may indicate an FFA origin for the radio spectral turnover in our sample. As for the complex spectrum of J114657.79+403708.6 at z  = 5.00 with two spectral peaks, it may be caused by multiple components (i.e., core-jet) and FFA by the high-density medium in the nuclear region. However, we cannot rule out the spectral turnover origin of variability. Based on our radio spectral modeling, we calculate the radio loudness R 2500 Å for our sample, which ranges from 12 −1 +1 to 674 −51 +61 . 

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5. MEAN AND EXTREME RADIO PROPERTIES OF QUASARS AND THE ORIGIN OF RADIO EMISSION

   https://doi.org/10.1088/0004-6256/149/2/61  

   Kratzer, Rachael M.; Richards, Gordon T. (February 2015, The Astronomical Journal)