HODfit2sim: HOD model fitted to model galaxies

This python code corresponds to the work presented in GRP2024 and VGP2024 (in prep.). It provides a halo occupation distribution (HOD) model with parameters chosen to reproduce the clustering of a sample of model tracers. These can be either galaxies, QSOs or clouds of gas.

To use this code, acknowledge the source work by adding references to GRP2024.

Construct a sample of shuffled tracers

To generate a file with both the positions and velocities of the tracers, together with those for the DM haloes, run main.py with get_sample set to True.

python3 main.py

At the moment, the code does not include a modelling for assembly bias, and thus, the input sample needs to be shuffled. This means that model tracers populating a halo of a given mass are randomly placed on the position of a different halo with a mass within a set range.

In GRP2024, the shuffling was done in bins of 0.057 dex of halo mass, using M200c within the UNIT simulation.

Characterise the sample of tracers

To characterise the sample of tracers, run main.py with get_params set to True.

There are several quantities that need to be measured to characterise the sample of tracers.

• Shape of the mean HOD for central and satellite tracers. This requires counting the total number of DM haloes in each mass bin.
• The global conformity factors from the mean HOD for satellites with and without a central tracer of the same type. If the global factors are not a good description of the tracers, try using the factors in mass bins, with flags [....].
• Radial profile of satellite tracers. If the modified NFW profile is not a good description, try using directly the measured average radial profile.

Populate haloes with tracers with the HOD model

To populate DM haloes with the HOD model, run main.py with run_HOD set to True. This:

1. Reads the information calculated for the sample of tracers and DM haloes.
2. Runs the HOD model with the given parameters.

Installation

Requirements: python 3 and its main packages all installable through pip: astropy, numpy, scipy, matplotlib, math ...

git clone git@github.com:computationalAstroUAM/HODfit2sim.git

Liscence

Shield:

This work is licensed under a Creative Commons Attribution 4.0 International License.