Forced Measurement of Astronomical Sources at Low Signal to Noise

TL;DR

This paper introduces a modified moment matching algorithm that reliably measures faint astronomical sources at low SNR, avoiding failures and reducing bias, enabling detection of sources seven times fainter than traditional methods.

Contribution

The paper presents a novel modification to the moment matching algorithm that prevents failures at low SNR and accurately measures faint sources, improving sensitivity in astronomical imaging.

Findings

Avoids catastrophic failures in nearly 100% of low SNR cases

Measures sources seven times fainter than traditional methods

Provides unbiased estimates of flux, centroid, size, shape, and ellipticity

Abstract

We propose a modified moment matching algorithm to avoid catastrophic failures for sources with a low signal to noise ratio (SNR). The proposed modifications include a method to eliminate non-physical negative pixel values and a forced single iteration with an initial guess derived from co-add measurements when iterative methods are unstable. We correct for all biases in measurements introduced by the method. We find that the proposed modifications allow the algorithm to avoid catastrophic failures in nearly 100\% of the cases, especially at low signal to noise ratio. Additionally, with a reasonable guess from co-add measurements, the algorithm measures the flux, centroid, size, shape and ellipticity with bias statistically consistent with zero. We show the proposed method allows us to measure sources seven times fainter than traditional methods when applied to images obtained from WIYN-ODI. We also present a scheme to find uncertainties in measurements when using the new method to measure astronomical sources.