Compact Symmetric Objects -- I Towards a Comprehensive Bona Fide Catalog

TL;DR

This paper aims to create a reliable catalog of bona fide Compact Symmetric Objects (CSOs) by refining classification criteria to exclude misidentified sources, enabling more accurate astrophysical studies of these AGN.

Contribution

The authors identify 79 confirmed CSOs, including 15 newly confirmed, using improved criteria that account for low variability and low apparent jet speeds, reducing misclassification.

Findings

Established a sample of 79 bona fide CSOs.

Confirmed 15 CSOs for the first time.

Estimated CSO fraction in flux-limited samples as 6.8-8.5%.

Abstract

Compact Symmetric Objects (CSOs) are jetted Active Galactic Nuclei (AGN) with overall projected size <1 kpc. The classification was introduced to distinguish these objects from the majority of compact jetted-AGN in centimeter wavelength very long baseline interferometry observations, where the observed emission is relativistically boosted towards the observer. The original classification criteria for CSOs were: (i) evidence of emission on both sides of the center of activity, and (ii) overall size <1 kpc. However some relativistically boosted objects with jet axes close to the line of sight appear symmetric and have been mis-classified as CSOs, thereby undermining the CSO classification. This is because two essential CSO properties, pointed out in the original papers, have been neglected: (iii) low variability, and (iv) low apparent speeds along the jets. As a first step towards creating a comprehensive catalog of ``bona fide'' CSOs, we identify 79 bona fide CSOs, including 15 objects claimed as confirmed CSOs here for the first time, that match the CSO selection criteria. This sample of bona fide CSOs can be used for astrophysical studies of CSOs without contamination by mis-classified CSOs. We show that the fraction of CSOs in complete flux density limited AGN samples with S$_{\rm 5\,GHz}$ >700 mJy is between $(6.8\pm1.6)$% and $(8.5\pm1.8)$%.