initial-mass-function 2026.3.23

Tools for sampling from and working with functional forms of the initial mass function

IMF

Installation

Either use the dev version:

pip install https://github.com/keflavich/imf/archive/refs/heads/master.zip

or use pypi:

pip install initial_mass_function

Note that the project name (initial_mass_function) is different from the packagename you import (imf) because the latter was taken.

Usage

Simple tools to work with the Initial Mass Function

Some basic examples below.

1. Make a simple 1000 Msun cluster sampled from the default Kroupa IMF:

   cluster = imf.make_cluster(1000)
   

   or from a Salpeter IMF:

   cluster = imf.make_cluster(1000, massfunc='salpeter')
   

2. Create a sample of clusters to do some analysis of later. This will make clusters with masses Gaussian-distributed around a given mean mass in the list of cluster_masses, so that you could then do things like estimate the typical luminosity of a cluster for a given mass:

   from imf import imf
   from tqdm.auto import tqdm
   cluster_masses = [100, 1000, 10000]
   nclusters_per_bin = 30
   clusters = np.array([[imf.make_cluster(mass*(np.random.randn()/20.+1.), silent=True)
                        for ii in range(nclusters_per_bin)]
                        for mass in tqdm(cluster_masses)])
   

3. Calculate the mass fraction represented by M>8 Msun stars in a Kroupa IMF when the maximum mass is 200 Msun:

     kroupa = imf.Kroupa()
   
     mmax = 200
     cutoff1 = 8
   
     over8fraction = (kroupa.m_integrate(cutoff1, mmax)[0] /
                      kroupa.m_integrate(kroupa.mmin, mmax)[0])
   

4. This figure was made with examples/imf_figure.py

   

Contributing

To avoid committing notebook cell outputs (plots/images), install the repository hooks:

pip install pre-commit
pre-commit install

The nbstripout hook will clear output from .ipynb files before commit, and CI enforces the same check.

Credits

• Adam Ginsburg (@keflavich, wrote most of this)
• Sergey Koposov (@segasai, majorly refactored the distribution functions)
• Theo Richardson (@richardson-t, refactored pre-IMF submodules and wrote/revised some functions and documentation)
• Tiffany Christian (@teachristian, made some small corrections)

A companion paper describing the package is in prep.