LOFAR discovery of rare large FR-I jets in low-luminosity radio galaxy NGC 5322

Amitesh Omar

Submitted on 29 June 2022


The discovery of faint FR~I radio jets in the nearby elliptical galaxy NGC 5322 is reported here using 144 MHz LOFAR image. The jets have an angular extent of 40 arcmin or a projected physical extent of 350 kpc. The faint jets remain well collimated and disappear in the intergalactic medium, without any visible hotspot or radio lobes. The jets detected up to 20 kpc extent at higher frequencies are relatively bright within the optical extent of the galaxy but become faint abruptly outside, where detection is made only in the LOFAR image. The total radio luminosity of the galaxy at 144 MHz is estimated to be 3.7(±0.4)×1022 W Hz1. The 144 MHz radio luminosity of the faint jets outside the optical extent is estimated to be 7.1(±2.0)×1021 W Hz1. The extent of the jets for its radio luminosity is abnormally large when compared to the general population of radio galaxies. It makes NGC 5322 a member of a rare population of radio galaxies, previously not detected in other radio surveys. A combined effect of stellar core depletion and low-density environment around the jets, inferred from previous studies in other wave-bands, resulting into weak entrainment of surrounding material to the jets could be responsible for its large size despite a low radio luminosity.


Comment: MNRAS submitted; 5 pages, 4 figures; comments welcome

Subjects: Astrophysics - Astrophysics of Galaxies; Astrophysics - Cosmology and Nongalactic Astrophysics