Exploring the squeezed three-point galaxy correlation function with generalized halo occupation distribution models

TL;DR

This paper introduces the GRAND-HOD framework, a generalized and differentiable halo occupation distribution model, to analyze galaxy correlation functions and improve understanding of galaxy-halo connections.

Contribution

The paper develops a flexible, generalized HOD model incorporating various physics and biases, and demonstrates its effectiveness in analyzing 2PCF and squeezed 3PCF data.

Findings

Degeneracies in projected 2PCF are broken in redshift-space and squeezed 3PCF.

Squeezed 3PCF provides additional constraints on galaxy-halo models.

Current HOD framework predicts squeezed 3PCF with high accuracy.

Abstract

We present the GeneRalized ANd Differentiable Halo Occupation Distribution (GRAND-HOD) routine that generalizes the standard 5 parameter halo occupation distribution model (HOD) with various halo-scale physics and assembly bias. We describe the methodology of 4 different generalizations: satellite distribution generalization, velocity bias, closest approach distance generalization, and assembly bias. We showcase the signatures of these generalizations in the 2-point correlation function (2PCF) and the squeezed 3-point correlation function (squeezed 3PCF). We identify generalized HOD prescriptions that are nearly degenerate in the projected 2PCF and demonstrate that these degeneracies are broken in the redshift-space anisotropic 2PCF and the squeezed 3PCF. We also discuss the possibility of identifying degeneracies in the anisotropic 2PCF and further demonstrate the extra constraining power of the squeezed 3PCF on galaxy-halo connection models. We find that within our current HOD framework, the anisotropic 2PCF can predict the squeezed 3PCF better than its statistical error. This implies that a discordant squeezed 3PCF measurement could falsify the particular HOD model space. Alternatively, it is possible that further generalizations of the HOD model would open opportunities for the squeezed 3PCF to provide novel parameter measurements. The GRAND-HOD Python package is publicly available at https://github.com/SandyYuan/GRAND-HOD .