About me


I am currently a PhD student at the University of Melbourne under the supervision of prof. Stuart Wyithe. My PhD research focuses on some statistical effects of strong gravitational lensing on the galaxy population.
In particular, I studied the magnification bias at the bright end of the galaxy luminosity function, the distribution of galaxy scale lenses in optical and NIR surveys, and the imprints of the Velocity Dispersion Function of early type galaxies on the strong lensing statistics.
Before the PhD, I was raised in the modern metropolis of Casalbuttano ed Uniti (Italy). I eventually moved to Milan, where I lived at Collegio di Milano and studied Physics at the University of Milan. There I graduated under prof. Claudio Grillo and prof. Giuseppe Bertin. In my master thesis I studied the presence of rotation and the state of dynamical relaxation in the galactic component of two clusters of galaxies.

Some research highlights

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  • VDF evolution from strong lensing statistics

  • A model for galaxy-galaxy strong lensing statistics in survey

  • Magnification bias depends on source size-L relation

Velocity dispersion function evolution from strong lensing statistics

The redshift and size distributions of galaxy scale strong lenses depend on the evolution of early-type galaxies (ETGs) in the redshift range 0.25 < z < 75. We use this dependence to constrain the velocity dispersion function (VDF) evolution from the Strong Lensing Legacy Survey (SL2S) sample of lenses. Our modeling of the lens population includes lens identifiability given survey parameters, and constrains the evolution of the VDF based on the redshift distributions of sources and lenses as well as the distribution of Einstein radii. We consider five different assumptions for the reference VDF at redshift zero and two sets of scaling relations for the VDF. We find that in all cases the observed lens sample favors a slow evolution of both the VDF normalization factor and the VDF characteristic velocity with redshift which is consistent with a VDF that is constant in redshift for z < 75.

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A model for galaxy-galaxy strong lensing statistics in surveys

Photometric wide-area observations in the next decade will be capable of detecting a large number of galaxy-scale strong gravitational lenses, increasing the gravitational lens sample size by orders of magnitude. To aid in forecasting and analysis of these surveys, we construct a flexible model based on observed distributions for the lens and source properties and test it on the results of past lens searches, including SL2S, SuGOHI and searches on the COSMOS HST and DES fields. We use this model to estimate the expected yields of some current and planned surveys, including Euclid Wide, Vera Rubin LSST, and Roman High Latitude Wide Area. The model proposed includes a set of free parameters to constrain on the identifiability of a lens in an image, allowing construction of prior probability distributions for different lens detection methods. The code used in this work is made publicly available.

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Magnification bias depends on source size-L relation

The bright end of the rest-frame ultraviolet luminosity function (UVLF) of high-redshift galaxies is modified by gravitational lensing magnification bias. Motivated by recent discoveries of very high-z galaxies with JWST, we study the dependence of magnification bias on the finite size of sources at 6 < z < 14. We calculate the magnification probability distributions and use these to calculate the magnification bias assuming a rest-frame Schechter UVLF for galaxies at redshift 6 < z < 14. We find that the finite size of bright high-redshift galaxies together with lens ellipticity significantly suppresses magnification bias, producing an observed bright end which declines more sharply than the power law resulting from assumption of point sources. By assuming a luminosity-size relation for the source population and comparing with the observed z = 6 galaxy luminosity function from Harikane et al. (2022), we show that the UVLF can be used to set mild constraints on the galaxies intrinsic size, favouring smaller galaxies compared to the fiducial luminosity-size relation.

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