Research |

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.

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Galaxy formation and evolution

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

A second major axis is galaxy formation and evolution across cosmic time. With collaborators at SISSA I have analysed the spectral properties of high-redshift galaxies using theoretical models of star formation and dust processes.

This led to GalaPy, a public code that simulates the panchromatic emission of galaxies from X-rays to radio, offering full SED modelling, Bayesian inference, and a computationally efficient implementation. It is the fastest SED-generation tool of its kind, with a peak performance of almost 1000 SEDs per second on a single core, thanks to a hybrid C++/Python architecture that generates models on the fly rather than relying on templates.

Since its release GalaPy has gained users across Europe, Asia and South America, and has been adopted for studies ranging from nearby resolved galaxies to JWST high-redshift candidates. In a recent paper I presented the computational design of the code in detail: its object-oriented architecture, a hybrid parallelisation strategy combining vectorised array programming, shared-memory concurrency and distributed-memory message passing, and the optimisations that keep it portable with minimal memory overhead. That work also introduced two new capabilities — parallel sampling for Bayesian inference, and a fully analytical panchromatic AGN component.

Currently: GalaPy is developing along two directions. I am co-supervising a Ph.D. student implementing panchromatic line emission in GalaPy SEDs, covering both the physics of emission lines and the sampling strategies needed for efficient inference. Meanwhile growing adoption for JWST and ALMA data is driving further computational optimisation and validated spectroscopic fitting beyond the current photometric mode.

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Cosmic voids

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

A major research theme has been the study of cosmic voids — vast, under-dense regions occupying most of the volume of the Universe. When I began working on my Master’s thesis, the community had theoretically demonstrated that the statistical properties of these structures could be exploited to constrain dark energy and test theories of gravity, but the theoretical models describing the void size distribution consistently failed to predict both simulated and observed data.

My work has paved the way for the cosmological exploitation of the void size function when voids are identified in any distribution of tracers, including real data catalogues. In Ronconi & Marulli (2017) we presented an algorithm that redefines void ridges and, consequently, their radii; I implemented it inside CosmoBolognaLib, a large set of open-source numerical libraries for cosmological calculations.

With this tool we then demonstrated that, as long as our specifications are accounted for, the size function is a viable approach for studying cosmology with cosmic voids. The result was further validated by its adoption as a fundamental tool in Key Projects within the Euclid Collaboration, used to forecast the cosmological constraining power of void statistics.

Currently: I am working with members of the Euclid Collaboration on void statistics in mock galaxy catalogues, and investigating a new theoretical model of the void distribution based on stochastic differential equations, together with Andrea Lapi at SISSA. A Ph.D. student has recently been selected to pursue this direction over the next three years under our supervision.

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Software: CosmoBolognaLib