Mitigating the Impact of the DESI Fiber Assignment on Galaxy Clustering

TL;DR

This paper introduces a simple, computationally efficient method to reduce the impact of fiber assignment incompleteness on galaxy clustering measurements in the DESI survey, preserving key cosmological signals.

Contribution

It proposes a modified correlation function that nulls angular modes affected by survey incompleteness, applicable with minimal changes to existing analysis pipelines.

Findings

The new statistic effectively mitigates fiber assignment bias.

The BAO signal remains unbiased with the new method.

Implementation requires only slight modifications to data catalogues.

Abstract

We present a simple strategy to mitigate the impact of an incomplete spectroscopic redshift galaxy sample as a result of fiber assignment and survey tiling. The method has been designed for the Dark Energy Spectroscopic Instrument (DESI) galaxy survey but may have applications beyond this. We propose a modification to the usual correlation function that nulls the almost purely angular modes affected by survey incompleteness due to fiber assignment. Predictions of this modified statistic can be calculated given a model of the two point correlation function. The new statistic can be computed with a slight modification to the data catalogues input to the standard correlation function code and does not incur any additional computational time. Finally we show that the spherically averaged baryon acoustic oscillation signal is not biased by the new statistic.