Spectral variability in faint high frequency peakers

TL;DR

This study analyzes the spectral variability of faint high frequency peaker radio sources using multi-epoch VLA data, revealing different behaviors linked to optical host types and suggesting young radio sources often reside in galaxy groups.

Contribution

It provides the first detailed multi-epoch spectral variability analysis of faint HFPs, linking radio variability with optical host properties and environmental context.

Findings

24 sources show no spectral variability

12 sources lose their peaked spectrum in some epochs

Most galaxy-hosted sources are young radio sources

Abstract

We present the analysis of simultaneous multi-frequency Very Large Array (VLA) observations of 57 out of 61 sources from the ``faint'' high frequency peaker (HFP) sample carried out in various epochs. Sloan Digital Sky Survey (SDSS) data have been used to identify the optical counterpart of each radio source. From the analysis of the multi-epoch spectra we find that 24 sources do not show evidence of spectral variability, while 12 objects do not possess a peaked spectrum anymore at least in one of the observing epochs. Among the remaining 21 sources showing some degree of variability, we find that in 8 objects the spectral properties change consistently with the expectation for a radio source undergoing adiabatic expansion. The comparison between the variability and the optical identification suggests that the majority of radio sources hosted in galaxies likely represent the young radio source population, whereas the majority of those associated with quasars are part of a different population similar to flat-spectrum objects, which possess peaked spectra during short intervals of their life, as found in other samples of high-frequency peaking objects. The analysis of the optical images from the SDSS points out the presence of companions around 6 HFP hosted in galaxies, suggesting that young radio sources resides in groups.