28 -- 40 GHz variability and polarimetry of bright compact sources in the QUIJOTE cosmological fields

TL;DR

This study characterizes the high-frequency variability and polarization of bright compact sources in the QUIJOTE fields, revealing diverse polarization fractions, high rotation measures, and significant variability, which impact cosmological analyses.

Contribution

It provides the first detailed high-frequency polarization and variability measurements of bright sources in the QUIJOTE fields, highlighting their complex behavior and the need for simultaneous monitoring.

Findings

Median polarization fraction of 2% consistent with previous studies

Median rotation measure of approximately 1110 rad/m^2, with an outlier up to 64000 rad/m^2

59% of sources are variable in total intensity, and all are variable in polarization

Abstract

We observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields which were brighter than 1 Jy at 30 GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28 -- 40 GHz, in order to characterise their high-radio-frequency variability and polarization properties. We find a roughly log-normal distribution of polarization fractions with a median of 2%, in agreement with previous studies, and a median rotation measure (RM) of $\approx$ 1110 rad m$^{-2}$ with one outlier up to $\approx$ 64000 rad m$^{-2}$ which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity flux density and median polarization fraction. We find 59% of sources are variable in total intensity, and 100% in polarization at $3\sigma$ level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis.