LaCE

LaCE contains a set of emulators for the one-dimensional flux power spectrum of the Lyman-alpha forest. It has been used in the papers:

• https://arxiv.org/abs/2011.15127
• https://arxiv.org/abs/2209.09895
• https://arxiv.org/abs/2305.19064 (latest version)

Please cite at least https://arxiv.org/abs/2305.19064 if you use this emulator in your research.

Installation

(Last update Jan 19 2024)

• Create a new conda environment. It is usually better to follow python version one or two behind. In January 2024, the latest is 3.12, so we recommend 3.11.

conda create -n lace -c conda-forge python=3.11 camb fdasrsf pip=24.0
conda activate lace

• Clone the repo into your machine and perform an editable installation:

git clone https://github.com/igmhub/LaCE.git
cd LacE
pip install -e .[explicit]

• If you want to use the GP emulator please run:

pip install -e .[gpy]

• If you want to use other versions of the packages you can install LaCE using:

pip install -e .

but there may be some issues.

• If you want to use notebooks via JupyterHub, you'll also need to download ipykernel:

pip install -e .[jupyter]
pip install ipykernel
python -m ipykernel install --user --name lace --display-name lace

Nyx users:

• You may need to add the Nyx path as an enviroment variable in your notebook kernel. The first is done writting in the kernel.json file:

 "env": {
  "NYX_PATH":"path_to_Nyx"
 }

For convenience, you could also add the Nyx path as an environment variable.

• To improve the reading time, you can precompute all cosmological information needed using CAMB. This is done by running the script

python scripts/compute_nyx_emu_cosmo.py

Note that you may need to update it as explained inside the file.

Emulator parameters:

These are the parameters that describe each individual P1D(k) power spectrum. We have detached these from redshift and traditional cosmology parameters.

Cosmological parameters:

Delta2_p is the amplitude of the (dimensionless) linear spectrum at k_p = 0.7 1/Mpc

n_p is the slope of the linear power spectrum at k_p

alpha_p is the running of the linear power spectrum at k_p

f_p is the (scale-independent) logarithmic growth rate

The current version of the emulator, relased in this repo, does not emulate alpha_p and f_p. However, these parameters are stored in the P1D archive.

IGM parameters:

mF is the mean transmitted flux fraction in the box (mean flux)

sigT_Mpc is the thermal broadening scale in comoving units, computed from T_0 in the temperature-density relation

gamma is the slope of the temperature-density relation

kF_Mpc is the filtering length (or pressure smoothing scale) in inverse comoving units

Tutorials:

In the Notebooks folder, there are several tutorials one can run to learn how to use the archives and emulators.

• Archive tutorial: notebooks/Tutorial_bookkeeping.ipynb
• Emulator tutorial: notebooks/Tutorial_emulator.ipynb

In the tests folder, there are four scripts that you can run to open a Gadget or Nyx archive and run the G^and NN emulators.