A Measurement of Source Noise at Low Frequency: Implications for Modern Interferometers

TL;DR

This paper measures source noise at low frequencies using the Murchison Widefield Array, revealing its impact on interferometer observations and confirming theoretical predictions in a regime where source flux is comparable to antenna noise.

Contribution

It provides the first direct measurement of source noise at 162MHz in a regime where source flux and antenna noise are comparable, informing future low-frequency interferometry.

Findings

Source noise magnitude matches predictions.

Detection achieved with a source contributing ~1% of total power.

Implications for current and future interferometric observations.

Abstract

We report on the detection of source noise in the time domain at 162MHz with the Murchison Widefield Array. During the observation the flux of our target source Virgo A (M87) contributes only $\sim$1\% to the total power detected by any single antenna, thus this source noise detection is made in an intermediate regime, where the source flux detected by the entire array is comparable with the noise from a single antenna. The magnitude of source noise detected is precisely in line with predictions. We consider the implications of source noise in this moderately strong regime on observations with current and future instruments.