The Python Sky Model 3 software

Abstract

The Python Sky Model (PySM) is a Python package used by Cosmic Microwave Background (CMB) experiments to simulate maps, in HEALPix pixelization, of the various diffuse astrophysical components of Galactic emission relevant at CMB frequencies (i.e. dust, synchrotron, free-free and Anomalous Microwave Emission), as well as the CMB itself. These maps may be integrated over a given instrument bandpass and smoothed with a given instrument beam. PySM 2, released in 2016, has become the de-facto standard for simulating Galactic emission, for example it is used by CMB-S4, Simons Observatory, LiteBird, PICO, CLASS, POLARBEAR and other CMB experiments, as shown by the 80+ citations of the PySM 2 publication. As the resolution of upcoming experiments increases, the PySM 2 software has started to show some limitations, the solution to these issues was to reimplement PySM from scratch focusing on these features: reimplement all the models with the numba Just-In-Time compiler for Python to reduce memory overhead and optimize performance; use MPI through mpi4py to coordinate execution of PySM 3 across multiple nodes and rely on libsharp, for distributed spherical harmonic transforms; employ the data utilities infrastructure provided by astropy to download the input templates and cache them when requested. At this stage we strive to maintain full compatibility with PySM 2, therefore we implement the exact same astrophysical emission models with the same naming scheme. In the extensive test suite we compare the output of each PySM 3 model with the results obtained by PySM 2.

arXiv commentSubmitted to JOSS, Github repository: https://github.com/galsci/pysm

References in corpus (6)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• HEALPix -- a Framework for High Resolution Discretization, and Fast Analysis of Data Distributed on the Sphere
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Final Maps and Results
• The Python Sky Model: software for simulating the Galactic microwave sky
• Libsharp - spherical harmonic transforms revisited

Cited by in corpus (6)

• The Simons Observatory: Galactic Science Goals and Forecasts
• Frequency dependence of the thermal dust $E/B$ ratio and $EB$ correlation: insights from the spin-moment expansion
• Non-Gaussian modelling and statistical denoising of Planck dust polarization full-sky maps using scattering transforms
• Dust polarization spectral dependence from Planck HFI data. Turning point on CMB polarization foregrounds modelling
• Constraints on the Optical Depth to Reionization from Balloon-Borne CMB Measurements
• Forecasting ground-based sensitivity to the Rayleigh scattering of the CMB in the presence of astrophysical foregrounds