Probing the bias of radio sources at high redshift

TL;DR

This paper introduces a new method to estimate the bias of high-redshift radio sources using angular clustering, photometric redshifts, and simulations, revealing that unmatched sources are likely at higher redshifts.

Contribution

It presents a novel approach to probe the bias of radio sources at high redshift without redshift data by combining optical matching, simulations, and angular correlation analysis.

Findings

Unmatched radio sources are predominantly at higher redshifts.

Angular correlation functions can differentiate redshift ranges.

Bias estimates align with dark matter clustering expectations.

Abstract

The relationship between the clustering of dark matter and that of luminous matter is often described using the bias parameter. Here, we provide a new method to probe the bias of intermediate to high-redshift radio continuum sources for which no redshift information is available. We matched radio sources from the Faint Images of the Radio Sky at Twenty centimetres (FIRST) survey data to their optical counterparts in the Sloan Digital Sky Survey (SDSS) to obtain photometric redshifts for the matched radio sources. We then use the publicly available semi-empirical simulation of extragalactic radio continuum sources (S3) to infer the redshift distribution for all FIRST sources and estimate the redshift distribution of unmatched sources by subtracting the matched distribution from the distribution of all sources. We infer that the majority of unmatched sources are at higher redshifts than the optically matched sources and demonstrate how the angular scales of the angular two-point correlation function can be used to probe different redshift ranges. We compare the angular clustering of radio sources with that expected for dark matter and estimate the bias of different samples.