3C 357

Lore & Background

3C 357 was first discovered in the Third Cambridge Catalogue of Radio Sources survey in 1962 by A.S. Bennett. It is also documented in the Fourth Cambridge survey, designated as 4C 31.47. The galaxy is classified as a Type II Fanaroff-Riley Class radio galaxy, hosted by a large featureless elliptical galaxy with a bright central core. Imaging by the Hubble Space Telescope reveals a dust lane on the southwest side of the galaxy, visible downwards to the inner region. This dust lane is split into two separate parts: one near the nucleus and the other extending outwards from the nucleus towards the northwest direction with a dust emission path at its end. A disky isophotal structure is present in the galaxy with faint thin tendrils.

The radio source of 3C 357 is a double, orientated nearly east to west. A radio map taken by the Very Large Array at 4.86 GHz shows a visible radio core and multiple hotspots, with a jet located within the northwest radio lobe pointing towards a compact hotspot. At 1.4 GHz, the map shows evidence of a large-scale structure. Snapshots with the Chandra X-ray Observatory found radio emission from the core with no traces of any radiation around it or associated with its hotspots. Although the nucleus is depolarized, a study showed four vectors in the emission region, found perpendicular towards the radius, indicating the polarized light has a scattering origin. In 2021, extended X-ray emission was found detected around the galaxy, mainly along the radio axis.

Reader's Guide

3C 357 is significant as a Fanaroff-Riley Type II radio galaxy, a class known for its edge-brightened radio lobes. Its discovery in the Third Cambridge Catalogue in 1962 by A.S. Bennett places it among early radio source identifications. The galaxy's featureless elliptical host with a bright core and complex dust lane—split into two parts with a dust emission path—provides insight into dust dynamics in elliptical galaxies. The radio structure, including a double source oriented east-west, a visible core, multiple hotspots, and a jet in the northwest lobe, illustrates typical FR II morphology. The detection of extended X-ray emission along the radio axis in 2021 adds to understanding of the interaction between the radio source and the intracluster medium. The depolarized nucleus and polarized light with scattering origin offer clues to magnetic field configurations. The absence of X-ray radiation around the core or hotspots, as observed by Chandra, distinguishes its emission properties.

Did You Know?

• The galaxy hosts a dust lane split into two separate parts: one near the nucleus and one extending northwest with a dust emission path.
• Extended X-ray emission was detected around the galaxy in 2021, mainly along the radio axis.