Cross-Correlation of Diffuse Synchrotron and Large-Scale Structures

TL;DR

This study investigates the potential of cross-correlating radio synchrotron emission with large-scale structure tracers to detect diffuse intergalactic medium signals, demonstrating the method's sensitivity and future applicability despite a null result.

Contribution

First application of cross-correlation between radio synchrotron emission and large-scale structure tracers to detect diffuse IGM/WHIM signals, assessing detection thresholds and future survey prospects.

Findings

Null result obtained in current data.

Detection thresholds suggest possible signals at microGauss magnetic fields.

Method shows promise for upcoming sensitive surveys.

Abstract

We explore for the first time the method of cross-correlation of radio synchrotron emission and tracers of large-scale structure in order to detect the diffuse IGM/WHIM. We performed a cross-correlation of a 34 x 34 degree area of 2MASS galaxies for two redshift slices (0.03 < z < 0.04 and 0.06 < z < 0.07) with the corresponding region of the 1.4 GHz Bonn survey. For this analysis, we assumed that the synchrotron surface brightness is linearly proportional to surface density of galaxies. We also sampled the cross-correlation function using 24 distant fields of the same size from the Bonn survey, to better assess the noise properties. Though we obtained a null result, we found that by adding a signal weighted by the 2MASS image with a filament (peak) surface brightness of 1 (7) mK and 7 (49) mK would produce a 3 sigma positive correlation for the 0.03 < z < 0.04 and 0.06 < z < 0.07 redshift slices respectively. These detection thresholds correspond to minimum energy magnetic fields as low as 0.2 microG, close to some theoretical expectations for filament field values. This injected signal is also below the rms noise of the Bonn survey, and demonstrates the power of this technique and its utility for upcoming sensitive continuum surveys such as GALFACTS at Arecibo and those planned with the Murchison Widefield Array (MWA).