The parsec-scale properties of the radio galaxy 4C 26.42 in the dense cooling core cluster A1795

TL;DR

This study investigates the parsec-scale radio properties of galaxy 4C 26.42 in Abell 1795, revealing symmetric jet structures, sub-relativistic speeds, and complex morphology influenced by the dense cooling core environment.

Contribution

First detailed VLBA multi-frequency, multi-epoch analysis of 4C 26.42's parsec-scale radio emission in a cooling core cluster environment.

Findings

Jets are likely sub-relativistic with proper motion limits of β_a < 0.04.

The source exhibits symmetric Z-shaped parsec-scale structure.

The kiloparsec-scale morphology is similar to parsec-scale but with reversed P.A. and bends.

Abstract

The aim of the present work is to study the radio emission on the parsec scale of 4C 26.42, the Brightest cluster galaxy in Abell 1795, in the framework of radiosources in a dense cool core cluster. We present Very Long Baseline Array (VLBA) observations at 1.6, 5, 8.4 and 22 GHz. We performed a spectral index and multiepoch analysis. The source appears two-sided with a well defined and symmetric Z-structure at ~5 mas from the core. The kiloparsec-scale morphology is similar to the parsec-scale structure, but reversed in P.A., with symmetric 90 deg. bends at about 2 arcsec from the nuclear region. Comparing data obtained at 3 different epochs we derive a 3$\sigma$ limit to the apparent proper motion of $\beta_a$ < 0.04. We suggest that the parsec-scale jets are sub-relativistic, in contrast with the high velocities found for most low-power radio galaxies. The origin of the unusual radio morphology remains a puzzle. We suggest that the identification of the parent galaxy with the central cD in a cooling cluster plays an important role in the properties and structure of the jets.