Clustering of Extragalactic Sources from 151 MHz to 232 MHz: Implications for Cosmological 21-cm Observations

TL;DR

This paper measures the angular correlation function of extragalactic radio sources at 151 and 232 MHz, providing insights crucial for accurate simulations in 21-cm cosmological experiments.

Contribution

It presents the first detailed measurement of the angular two-point correlation function at these low frequencies, revealing a double power law behavior independent of flux threshold.

Findings

w(θ) fits a double power law at 232 MHz

Slope γ ~ -1.12 for 0.2° to 0.6°

Shallower slope γ ~ -0.16 at larger angles

Abstract

In order to construct accurate point sources simulations at the frequencies relevant to 21-cm experiments, the angular correlation of radio sources must be taken into account. This paper presents a measurement of angular two-point correlation function, w(\theta), at 232 MHz from the MIYUN survey - tentative measurements of w(\theta) are also performed at 151 MHz. It is found that double power law with shape w(\theta) = A \theta^{-\gamma} fits the 232 MHz data well. For the angular lenght of 0.2 degrees < \theta < 0.6 degrees, \gamma ~ -1.12, and this value of slope is independent of the flux-density threshold; while for angular lenghts much greater than 0.6 degrees, \gamma has a shallower value of about -0.16. By comparing the results of this paper with previous measurements of w(\theta), it is discussed how w(\theta) changes with the change of frequency and completness limit.