Multi-epoch VLBA observations of radio galaxy 0932+075: is this a compact symmetric object?

TL;DR

Long-term VLBA observations of galaxy 0932+075 reveal that its radio structure does not conform to the compact symmetric object model, challenging previous classifications and indicating the need for alternative interpretations.

Contribution

This study provides multi-epoch, multi-frequency VLBA data that refutes the CSO classification of 0932+075, highlighting the importance of proper motion analysis in radio galaxy morphology.

Findings

Displacements of components are inconsistent with CSO behavior.

The identified high-frequency peaker (HFP) is not the core.

The western structure is not a CSO anchored at the HFP.

Abstract

A part of the radio structure of the galaxy 0932+075 emerged as a possible compact symmetric object (CSO) after the observation with the Very Long Baseline Array (VLBA) at 5 GHz in 1997. More than a decade later, we carried out observations at 5, 15.4, and 22.2 GHz using the VLBA to test this possibility. We report here that we have found a component whose spectrum is inverted in the whole range from 5 GHz to 22 GHz and we label it a high-frequency peaker (HFP). Using a set of 5 GHz images from two epochs separated by 11.8 years and a set of 15.4 GHz images separated by 8.2 years, we were able to examine the proper motions of the three components of the CSO candidate with respect to the HFP. We found that their displacements cannot be reconciled with the CSO paradigm. This has led to the rejection of the hypothesis that the western part of the arcsecond-scale radio structure of 0932+075 is a CSO anchored at the HFP. Consequently, the HFP cannot be labelled a core and its role in this system is unclear.