Galactic Halos Derived from LambdaCDM Cosmology Simulation and their Red-Shift Evolution

TL;DR

This paper uses LambdaCDM cosmological simulations to identify galaxy-hosting halos based on mass criteria, analyzes their properties, and compares the results with observations to validate the simulation approach.

Contribution

It introduces a method to select galaxy-hosting halos from simulations using a specific mass threshold and validates the resulting galaxy samples against observational data.

Findings

Galaxy mass functions match observations

Galaxy spatial distributions agree with observed correlation functions

The simulation-based galaxy samples reliably represent real universe galaxies

Abstract

Galaxies can form in a sufficiently deep gravitational potential so that efficient gas cooling occurs. We estimate that such potential is provided by a halo of mass $M \gtsim M_{c} \approx 7.0 \times 10^{12} ~ (\Delta_{c}(z) (1+z)^{3})^{-1/2} \Msun$, where $\Delta_{c}(z)$ is the mean overdensity of spherically virialized objects formed at redshift $z$, and $M_{c} \approx 4.0 \times 10^{11} \Msun$ at $z = 0$. Based on this criterion, our galaxy samples are constructed from cosmology simulation data by using HiFOF to select subhalos in those FOF halos that are more massive than $M_{c}$. There are far more dark subhalos than galaxy-hosting subhalos. Several tests against observations have been performed to examine our galaxy samples, including the differential galaxy mass functions, the galaxy space density, the projected two point correlation functions (CF), the HODs, and the kinematic pair fractions. These tests show good agreements. Based on the consistency with observations, our galaxy sample is believed to correctly represent galaxies in real universe, and can be used to study other unexplored galaxy properties.