The galaxy–halo connection

Wed, 29 Jul 2026 00:00:00 +0000

A central axis of my work is the development of empirical models linking dark matter haloes to galaxies, in order to generate realistic mock galaxy catalogues for SKAO and Euclid.

As a major outcome of my Ph.D. thesis I created SCAMPy, a hybrid C++/Python library for painting observed galaxy populations on top of the dark matter halo/sub-halo hierarchy of N-body simulations. It implements the Sub-halo Clustering and Abundance Matching scheme: a Halo Occupation Distribution prescription first selects which sub-haloes host galaxies, then sub-halo abundance matching assigns observable properties to each object. The method requires only the observed distribution of the target property — a luminosity function, say — and the clustering statistics of the target population. The result is a computationally efficient, fully data-driven way to produce mocks that reproduce both the 1- and 2-point statistics of any observed sample, from high-redshift Lyman-break galaxies to low-redshift radio sources. SCAMPy has since become a core ingredient in the simulation pipelines used for SKAO preparatory science.

During a research stay at SKAO Headquarters I also contributed to T-RECS, a tool for simulating radio sources in continuum and HI line, now widely used in the radio-cosmology community for survey design and theoretical modelling.

This line of work recently culminated in a comprehensive framework for constructing full-sky empirical mock catalogues of the radio sky: a modular pipeline combining a simulated dark-matter light-cone, built from the high-resolution DEMNUni N-body simulations, with empirically sampled galaxy populations generated by T-RECS and assigned to haloes via an extended version of SCAMPy. The resulting catalogues cover the full 4π steradians down to redshift z = 5 and place multiple radio populations on a common light-cone: continuum-emitting AGN and star-forming galaxies alongside HI line-emitting sources. No single existing approach had previously combined full-sky coverage, multiple radio populations, empirical flexibility and modularity.

I currently lead a European collaboration integrating these pipelines to enable joint radio continuum and line studies. In this context I coordinated the HI Simulations chapter for the next edition of Advancing Astrophysics with the SKA (AASKA II), bringing together researchers from four continents to compile a comprehensive description and comparison of the simulations available for studying post-reionization HI.

Currently: extending the framework to incorporate multi-wavelength counterparts, connecting radio populations to their optical, infrared and sub-mm emission for cross-survey analyses combining SKAO with Euclid and other facilities. I am also exploring reinforcement-learning approaches to extend the empirical models underlying the galaxy–halo connection.

Key papers: · ·

Software: ·

SCAMPy

Sat, 01 Aug 2020 00:00:00 +0000

Role: author & maintainer. Stack: C++ core (object-oriented, polymorphic) wrapped in Python.

SCAMPy implements the Sub-halo Clustering and Abundance Matching (SCAM) scheme, which combines the classical Halo Occupation Distribution with sub-halo abundance matching. The procedure runs in two steps: the HOD prescription selects which sub-haloes host galaxies, then SHAM assigns an observable property of choice to each selected sub-halo. It requires only the 1- and 2-point statistics of the target population as input — typically an observed luminosity function and its clustering — which makes the method fully data-driven rather than dependent on a physical galaxy-formation model.

The core functionalities are written in C++ and make wide use of polymorphism for flexibility and computational efficiency; the whole library is wrapped in Python so it can be driven from a scripting interface or embedded in a larger pipeline. Mock catalogues produced this way reproduce both the abundance and the clustering of the target sample, and the approach applies across a wide redshift range, from high-redshift Lyman-break galaxies to low-redshift radio sources.

SCAMPy came out of my Ph.D. thesis and has since become a core ingredient in simulation pipelines used for SKAO preparatory science, including the full-sky radio mock catalogues described in my .

Presented in Monthly Notices of the Royal Astronomical Society 498, 2095 (2020) — see . Also indexed in the Astrophysics Source Code Library as ascl:2002.006.

N-Body Simulations |

The galaxy–halo connection

SCAMPy