Angular clustering of point sources at 150 MHz in the TGSS survey

TL;DR

This study analyzes the angular clustering of point sources at 150 MHz in the TGSS survey, revealing that brighter sources cluster more strongly, which has implications for foreground modeling in cosmological surveys.

Contribution

It provides the first detailed measurement of the angular correlation function of radio sources at 150 MHz across a large sky area, showing how clustering amplitude varies with flux limit.

Findings

Clustering amplitude increases with flux threshold.

Brighter sources are likely hosted by massive halos.

Power law relation between flux limit and clustering amplitude.

Abstract

We study the angular clustering of point sources in The GMRT (Giant Meter Wave Telescope) Sky Survey (TGSS). The survey at 150 MHz with delta > -53.5 degrees has a sky coverage of 3.6 pi steradians, i.e., 90% of the whole sky. We created subsamples by applying different total flux thresholds limit (S >> 5 sigma) for good completeness and measured the angular correlation function omega(theta) of point sources at large scales ( >= 1 degree). We find that the amplitude of angular clustering is higher for brighter subsamples, this indicates that higher threshold flux samples are hosted by massive halos and cluster strongly: this conclusions is based on the assumption that the redshift distribution of sources does not change with flux and this is supported by models of radio sources. We compare our results with other low-frequency studies of clustering of point sources and verify that the amplitude of clustering varies with the flux limit. We quantify this variation as a power law dependence of the amplitude of correlation function with the flux limit. This dependence can be used to estimate foreground contamination due to clustering of point sources for low frequency HI intensity mapping surveys for studying the epoch of reionisation.