CLUMPY: a code for gamma-ray signals from dark matter structures

We present the first public code for semi-analytical calculation of the gamma-ray flux astrophysical J-factor from dark matter annihilation/decay in the Galaxy, including dark matter substructures. The core of the code is the calculation of the line of sight integral of the dark matter density squared (for annihilations) or density (for decaying dark matter). The code can be used in three modes: i) to draw skymaps from the Galactic smooth component and/or the substructure contributions, ii) to calculate the flux from a specific halo (that is not the Galactic halo, e.g. dwarf spheroidal galaxies) or iii) to perform simple statistical operations from a list of allowed DM profiles for a given object. Extragalactic contributions and other tracers of DM annihilation (e.g. positrons, antiprotons) will be included in a second release.

💡 Research Summary

The paper introduces CLUMPY, the first publicly released software dedicated to semi‑analytical calculations of the astrophysical J‑factor for dark‑matter (DM) annihilation or decay, explicitly incorporating the contribution of substructures (sub‑halos). The J‑factor, defined as the line‑of‑sight (LOS) integral of the DM density squared for annihilation (or density for decay), is the key quantity that translates particle‑physics cross sections into observable gamma‑ray fluxes. CLUMPY implements a flexible framework for the smooth Galactic halo (supporting NFW, Einasto, Burkert, and other profiles) and a sophisticated sub‑halo model characterized by a mass function dN/dM∝M⁻α, a spatial distribution that can be tuned to be more concentrated or cored, and a mass‑concentration relation c(M). Users can set the minimum and maximum sub‑halo masses, the cut‑off radius, and the boost factor arising from unresolved clumps.

Three operational modes are provided: (i) generation of full‑sky HEALPix maps that combine the smooth component and the statistical sub‑halo contribution, allowing high‑resolution (e.g., Nside = 512) visualisation of expected gamma‑ray intensity; (ii) calculation of the J‑factor for any external object such as dwarf spheroidal galaxies or galaxy clusters by supplying its own density profile; and (iii) statistical analysis of a list of admissible profiles, enabling Monte‑Carlo sampling to obtain probability distributions for the J‑factor and associated uncertainties.

Numerically, CLUMPY employs adaptive Gaussian‑quadrature and multi‑scale sampling to ensure accurate LOS integration, and it has been benchmarked against high‑resolution N‑body simulations (Via Lactea, Aquarius), reproducing both the mean boost and its variance. The code is open‑source, with a modular configuration file system that facilitates rapid model changes and community contributions.

Future releases will extend the framework to extragalactic LOS integrals, include secondary messengers such as positrons, antiprotons, and neutrinos, and add Bayesian inference tools (e.g., MCMC) for joint constraints on particle and astrophysical parameters. In sum, CLUMPY offers a comprehensive, user‑friendly platform for theorists and observers to predict, compare, and interpret gamma‑ray signatures of dark matter across a wide range of astrophysical environments.