Toward accurate measurement of property-dependent galaxy clustering I. Comparison of the Vmax method and the "shuffled" method

TL;DR

This study compares two redshift assignment methods, Vmax and shuffled, for galaxy clustering measurements, finding Vmax more accurate especially for flux-limited samples, thus improving galaxy formation insights.

Contribution

It provides a systematic comparison of redshift assignment methods using mock catalogs, recommending the Vmax method for more accurate galaxy clustering analysis.

Findings

Shuffled method underestimates 2PCFs in redshift space.

Vmax method shows no notable bias for volume-limited samples.

Vmax method outperforms shuffled for flux-limited samples on large scales.

Abstract

Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution, as well as the universe. The redshift assignment for the random sample is one of the key steps to measure the galaxy clustering accurately. In this paper, by virtue of the mock galaxy catalogs, we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions (hereafter 2PCFs), the Vmax method and the "shuffled" method. We found that the shuffled method significantly underestimates both of the projected 2PCFs and the two-dimensional 2PCFs in redshift space. While the Vmax method does not show any notable bias on the 2PCFs for volume-limited samples. For flux-limited samples, the bias produced by the Vmax method is less than half of the shuffled method on large scales. Therefore, we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis.