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

作者：Dabhade Pratik; Gaikwad Madhuri; Bagchi Joydeep; Pandey Pommier M; Sankhyayan Shishir; Raychaudhury Somak

来源：Monthly Notices of the Royal Astronomical Society, 2017, 469(3): 2886-2906.

DOI：10.1093/mnras/stx860

• galaxies: active
• intergalactic medium
• galaxies: jets
• galaxies: nuclei
• quasars: supermassive black holes
• infrared: galaxies

Giant radio galaxies (GRGs) are one of the largest astrophysical sources in the Universe with an overall projected linear size of similar to 0.7 Mpc or more. The last six decades of radio astronomy research has led to the detection of thousands of radio galaxies. However, only similar to 300 of them can be classified as GRGs. The reasons behind their large size and rarity are unknown. We carried out a systematic search for these radio giants and found a large sample of GRGs. In this paper, we report the discovery of 25 GRGs from the National Radio Astronomy Observatory Very Large Array Sky Survey, in the red-shift range z similar to 0.07 to 0.67. Their physical sizes range from similar to 0.8 Mpc to similar to 4 Mpc. Eight of these GRGs have sizes >= 2 Mpc, which is a rarity. Here, for the first time, we investigate the mid-infrared (IR) properties of the optical hosts of the GRGs and classify them securely into various active galactic nuclei types using the WISE mid-IR colours. Using radio and IR data, four of the hosts of the GRGs were observed to be radio-loud quasars that extend up to 2 Mpc in radio size. These GRGs missed detection in earlier searches possibly because of their highly diffuse nature, low surface brightness and lack of optical data. The new GRGs are a significant addition to the existing sample. They will contribute to a better understanding of the physical properties of radio giants.

• 出版日期2017-8