Overview

Name:

Extragalactic Point Sources

Author:

Shikhar Mittal

Paper:

Mittal et al (2024)

Documentation:

epspy.readthedocs.io

Why do you need this code?

Use this code to generate the foregrounds due to extragalactic point sources.

A cosmological global 21-cm signal hides under foregrounds due to galactic and extragalactic emissions. These foregrounds can easily be 4 to 5 orders of magnitude higher than the signal of interest. For a reliable inference, it is important to accurately model these foregrounds. While we have a reasonable understanding of galactic emission (typically fit as a log-log polynomial), we do not understand the extragalactic contributions. This package models the foregrounds due to extragalactic radio sources.

Read more about it in the paper Mittal et al (2024).

Installation and requirements

This package can be installed as

pip install epspy

It is recommended to work on a Python version > 3.8. Packages required are

• numpy

• scipy

• matplotlib

• mpi4py

• healpy

• transformcl

Quick start

The code is run in two main steps:

• Assign the point sources flux densities (at a chosen reference frequency) and spectral indices.

• Then generate the sky maps at desired frequencies of observation.

The following code captures the main functionalities of this package.

from epspy import meps

#Step-1 initialise the object with default settings
obj = meps.eps()

#Step-2 generate the data at the reference frequency
obj.ref_freq()

#Step-3 generate the sky maps at multiple frequencies as well as their sky average
obj.gen_freq()

#Step-4 finally, generate a sky-averaged spectrum vs frequency figure
obj.visual()

Save the above code as (say) eg_script.py and run it as

python eg_script.py

Running the above will generate several files. The terminal messages will guide you to these output files. The most important of all files of your interest will be Tb_nu_map.npy. To visualise your outputs use the function visual(). Refer to the documentation for more details. To learn about the physics of this package see our paper.

The default values in this package have been chosen such that the users can run their scripts on a PC. Since modern PCs have at least 4 cores, for a better performance, one could also run eg_script.py parallelly as

mpirun -np 4 python eg_script.py

In general, and for more realistic flux density ranges and high-resolution maps, it is recommended to use the code on high-performance clusters.

Documentation

For more details on the working of the package and understanding the output files refer to the documentation.

License and citation

The software is free to use on the MIT open-source license. If you use the software then please cite Mittal et al (2024).

If the code is used in a project where the author has provided significant scientific input, guidance on methodology, or assistance with interpretation of results, then co-authorship on resulting publications is expected, following standard academic practice.

Users are encouraged to contact the author when using the code for new scientific applications or major projects.

Acknowledgement

I thank Girish Kulkarni, Dominic Anstey, and Eloy de Lera Acedo for helpful comments and feedback during the development of this code.