NPTFit: A code package for Non-Poissonian Template Fitting

TL;DR

NPTFit is an open-source Python package that implements non-Poissonian template fitting, enabling the analysis of unresolved point sources in astrophysical data, with applications demonstrated in gamma-ray and potentially other astronomical datasets.

Contribution

The paper introduces NPTFit, a new computational tool that generalizes traditional template fitting to detect unresolved point source populations in astrophysical data.

Findings

Successfully applied to Fermi gamma-ray data to identify point source contributions.

Provides efficient computational methods for non-Poissonian template fitting.

Potential applications extend beyond gamma-ray data to other astronomical observations.

Abstract

We present NPTFit, an open-source code package, written in python and cython, for performing non-Poissonian template fits (NPTFs). The NPTF is a recently-developed statistical procedure for characterizing the contribution of unresolved point sources (PSs) to astrophysical data sets. The NPTF was first applied to Fermi gamma-ray data to give evidence that the excess of ~GeV gamma-rays observed in the inner regions of the Milky Way likely arises from a population of sub-threshold point sources, and the NPTF has since found additional applications studying sub-threshold extragalactic sources at high Galactic latitudes. The NPTF generalizes traditional astrophysical template fits to allow for the ability to search for populations of unresolved PSs that may follow a given spatial distribution. NPTFit builds upon the framework of the fluctuation analyses developed in X-ray astronomy, and thus likely has applications beyond those demonstrated with gamma-ray data. The NPTFit package utilizes novel computational methods to perform the NPTF efficiently. The code is available at https://github.com/bsafdi/NPTFit and up-to-date and extensive documentation may be found at http://nptfit.readthedocs.io