Discovery of giant radio galaxies from NVSS: radio and infrared properties

Dabhade, Pratik; Gaikwad, Madhuri; Bagchi, J.; Pandey-Pommier, M.; Sankhyayan, Shishir; Raychaudhury, Somak

doi:10.1093/mnras/stx860

Cited by 55 publications

(85 citation statements)

References 75 publications

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“…The opted search radius of 120 corresponds to the physical scale of ∼ 900 kpc at the redshift cut-off (z < 0.8) of our sample. Thus, the diameter of circle within which additional radio components are searched, is similar to the size of a typical giant radio galaxy (see Dabhade et al 2017). We visually inspected 5 × 5 FIRST image cut-outs of all the sources that show one or more additional radio sources within the circle of 120 radius.…”

Section: 4 Ghz Radio Counterparts In the Firstmentioning

confidence: 99%

Investigating kpc-scale radio emission properties of narrow-line Seyfert 1 galaxies

Singh

Chand

2018

Monthly Notices of the Royal Astronomical Society

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In recent years, several Radio-Loud Narrow-Line Seyfert 1 galaxies (RL-NLS1) possessing relativistic jets have come into attention with their detections in Very Large Baseline Array (VLBA) and in γ-ray observations. In this paper we attempt to understand the nature of radio-jets in NLS1s by examining the kpc-scale radio properties of, hitherto, the largest sample of 11101 optically-selected NLS1s. Using 1.4 GHz FIRST, 1.4 GHz NVSS, 327 MHz WENNS, and 150 MHz TGSS catalogues we find the radiodetection of merely ∼ 4.5 per cent (498/11101) NLS1s, with majority (407/498 ∼ 81.7 per cent) of them being RL-NLS1s. Our study yields the highest number of RL-NLS1s and it can only be a lower limit. We find that the most of our radio-detected NLS1s are compact (< 30 kpc), exhibit both flat as well as steep radio spectra, and are distributed across a wide range of 1.4 GHz radio luminosities (10 22 − 10 27 W Hz −1 ). At the high end of radio luminosity our NLS1s often tend to show blazar-like properties such as compact radio-size, flat/inverted radio spectrum, radio variability and polarization. The diagnostic plots based on the mid-IR colours suggest that the radio emission in NLS1s is mostly powered by AGN, while nuclear star-formation may have a significant contribution in NLS1s of low radio luminosities. The radio luminosity versus radio-size plot infers that the radio-jets in NLS1s are either in the early evolutionary phase or possibly remain confined within the nuclear region due to low-power or intermittent AGN activity.

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Section: 4 Ghz Radio Counterparts In the Firstmentioning

confidence: 99%

Investigating kpc-scale radio emission properties of narrow-line Seyfert 1 galaxies

Singh

Chand

2018

Monthly Notices of the Royal Astronomical Society

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“…A compact radio core is detected in the FIRST image. This is a giant radio galaxy, with a size of 2.3 Mpc (Dabhade et al 2017).…”

Section: Notes On Candidate Hymorsmentioning

confidence: 99%

Radio Galaxy Zoo: A Search for Hybrid Morphology Radio Galaxies

Kapińska

Terentev²,

Wong

et al. 2017

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Hybrid morphology radio sources (HyMoRS) 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 HyMoRS, we embarked on a largescale 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 4.7 10 median 24=´W Hz −1 sr −1 ) at redshifts z 0.14 1.0 < < . Hosts of nine candidates have spectroscopic observations, of which six are classified as quasars, one as high-and two as low-excitation galaxies. Two candidate HyMoRS are giant ( 1 > Mpc) radio galaxies, one resides at the center of a galaxy cluster, and one is hosted by a rare green bean galaxy. Although the origin of the hybrid morphology radio galaxies is still unclear, this type of radio source starts depicting itself as a rather diverse class. We discuss hybrid radio morphology formation in terms of the radio source environment (nurture) and intrinsically occurring phenomena (nature; activity cessation and amplification), showing that these peculiar radio galaxies can be formed by both mechanisms. While high angular resolution follow-up observations are still necessary to confirm our candidates, we demonstrate the efficacy of the RGZ in the pre-selection of these sources from all-sky radio surveys, and report the reliability of citizen scientists in identifying and classifying complex radio sources.

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“…like the Westerbork Northern Sky Survey (Rengelink et al 1997) at 0.3 GHz, the Sydney University Molonglo Sky Survey (SUMSS, Bock, Large & Sadler 1999) at 0.8 GHz, the NRAO VLA Sky Survey (NVSS, Condon et al 1998) and the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST, Becker, White & Helfand 1995) at 1.4 GHz. The more recent samples by Schoenmakers et al (2000a), Saripalli et al (2005), Lara et al (2001a), Machalski, Jamrozy & Zo la (2001); Machalski et al (2006); Machalski, Kozie l-Wierzbowska & Jamrozy (2007), Kuźmicz & Jamrozy (2012) as well as Dabhade et al (2017) and others have increased the number of known GRSs more than 6 times as compared to the sample of Ishwara-Chandra & Saikia (1999).…”

Section: Introductionmentioning

confidence: 96%