Astronomy below the Survey Threshold

TL;DR

This paper reviews recent advances in astronomical analysis techniques at or below survey detection thresholds, focusing on confusion, P(D) analyses, and stacking methods, and discusses implications for future SKA surveys.

Contribution

It provides an overview of recent developments in low-threshold astronomical analysis techniques and discusses their impact on survey design and interpretation.

Findings

Recent techniques enable analysis below traditional survey limits.

Examples demonstrate the effectiveness of confusion and stacking methods.

Implications influence the design of future SKA surveys.

Abstract

Astronomy at or below the 'survey threshold' has expanded significantly since the publication of the original 'Science with the Square Kilometer Array' in 1999 and its update in 2004. The techniques in this regime may be broadly (but far from exclusively) defined as 'confusion' or 'P(D)' analyses (analyses of one-point statistics), and 'stacking', accounting for the flux-density distribution of noise-limited images co-added at the positions of objects detected/isolated in a different waveband. Here we discuss the relevant issues, present some examples of recent analyses, and consider some of the consequences for the design and use of surveys with the SKA and its pathfinders.