Hello everybody and welcome to my webpage!

What I work on in my Ph.D.

I’m Silvia Onorato, Ph.D. Student at Leiden Observatory, working in the ENIGMA group led by Prof. Joseph F. Hennawi. I study high-redshift quasars (z>6.5), focusing on the analysis of optical and NIR spectra that are taken with several instruments (i.e., VLT/X-Shooter, Keck/NIRES, LRIS, DEIMOS, Gemini/GNIRS, GMOS, and LBT/MODS) and then reduced with the open-source Python-based spectroscopic data reduction pipeline PypeIt. The goal of my Ph.D. project is to infer information on the quasar lifetimes, on the average hydrogen neutral fraction at the epoch of Reionization, and on supermassive black hole growth. My sample consists of 45 quasars at 6.50<z<7.65 fully reduced and (soon) publicly available. For the first part of my project, I created a composite spectrum and compared it to others at both high- and low-z, proving that it does not change across cosmic time (Onorato et al. 2024, submitted to MNRAS). Currently, I am finalizing the analysis of their proximity zone sizes, expanding the sample size to lower-z with additional data to carry out a complete study of their evolution (Onorato et al. 2025a in prep). Soon I will also constrain the proximity zone probability distribution function by comparing real and mock data (Onorato et al. 2025b in prep).

Right before my Ph.D.

During my Master at Alma Mater Studiorum University of Bologna, I had great pleasure in working on Globular Clusters (GCs), studying the distribution of Multiple Populations in the isolated and dynamically young system NGC 2419 to place observational constraints on the initial formation and evolution scenarios of GCs. I worked with UV and optical WFC3/UVIS photometry from both HST and LBT, mastering PSF-fitting technique with DAOPHOT, magnitude measurements, and catalog cross-correlations. Exploiting the fact that the filters used were sensitive to differences in light elements (i.e., He, N), in a Chromosome Map I identified four different sub-populations, and studied several properties such as their radial distribution, density profiles, 2D density maps, the fraction of “first population” (FP) stars, and, finally, how NGC 2419 compares with other GCs and models, in terms of their sub-populations mass segregation. I found that “second population” (SP) stars are more centrally concentrated than FP and that the fraction of FP stars is larger than expected. This may be due to the transition of NGC 2419 to a weaker tidal field, as a number of studies suggested it formed in the Sagittarius dwarf galaxy and was accreted by the Milky Way. If you want to know more about this exciting work, check this out: Onorato et al. 2023 (published on A&A)!

About myself

I was born in Palermo in 1996 and raised in Bagheria. My passion for Astrophysics took me to Bologna in 2015, and now, with a Ph.D. position in Leiden, I’m still exploring the Universe — but also many other things!

Despite the knee complaints of an elderly soul, I’m stubborn enough to still play as a libero (yes, I’m short) in a volleyball team. I started in 2004 and have played in every city I’ve lived in.

Fun fact: as now I am based in the Netherlands, I had to learn from scratch every volleyball-related term in English (which caused some confusion on the court in the beginning). Even funnier fact: my volleyball mates are Dutch and they sometimes shout stuff in Dutch (that I do not speak); so I made myself able to link a certain shout to a certain action, even not knowing the meaning of it (yes, like dogs do). To make my knee pain worse, I love skiing at least once a year. I learned how to do it 3 years ago, and I am really proud of this achievement as now I know how wonderful it is. Another fun fact: when I moved to the Netherlands I was not a great bike rider, but I bought my first bike and, with a lot of practice, I managed to ride it properly! I only fell 3 times (with minor injuries).

While I’m not much of a boulderer/climber (fear of heights hasn’t helped), I love hiking, traveling (Iceland has a special spot in my heart), and taking pictures of the beautiful places I visit (see a few pics here). When I can chill on my couch, I also enjoy reading books (among my favorites: “The Unbearable Lightness of Being”, “The Shadow of the Wind”, and “Fresh Water for Flowers”), watching TV series (I am a huge “Friends” fan), and listening to music (I love Caparezza, Pinguini Tattici Nucleari, and many international artists). I hope from this description I made clear enough that I like being ironic (especially about myself) and having fun and laughing with people! Cheers :)

Contact

Leiden Observatory - Einsteinweg 55, 2333 CC Leiden (The Netherlands)

E-mail: onorato@strw.leidenuniv.nl

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