CMBForegrounds.jl

A general-purpose Julia package for building CMB likelihoods with foreground and systematic effect modeling

Overview

CMBForegrounds.jl is designed as a foundational tool for constructing Cosmic Microwave Background (CMB) likelihoods. The package provides well-tested, optimized, and differentiable functions for modeling the most relevant and commonly employed functional forms for:

Astrophysical foregrounds (galactic dust, synchrotron, free-free emission)
Secondary anisotropies (thermal and kinematic Sunyaev-Zel'dovich effects)
Instrumental systematics and calibration effects
Spectral energy distributions and frequency-dependent responses

Key Features

Well-tested: Comprehensive test suite with 158+ unit tests ensuring numerical accuracy
Optimized: Efficient implementations of spectral functions and frequency transformations
Differentiable: Compatible with automatic differentiation frameworks for gradient-based inference
General-purpose: Flexible building blocks for custom likelihood implementations
Standards-compliant: Follows Julia community best practices and conventions

Core Functionality

The package provides fundamental spectral functions including:

Planck function ratios and temperature derivatives
Thermal Sunyaev-Zel'dovich (tSZ) spectral functions
Dimensionless frequency variables for blackbody calculations
Physical constants and unit conversions

Installation

using Pkg
Pkg.add("CMBForegrounds")

Physical Constants

The package includes several important physical constants used in CMB analysis: