Research interests

The first billion years of our Universe were the theatre of the formation of the first stars, black holes and galaxies. These first galaxies produced the first elements heavier than hydrogen and helium and emitted enough light to reionise the hydrogen in the intergalactic medium. As an observational astronomer and astrophysicist, I use the most powerful ground-based telescopes to detect and study the first galaxies, the co-evolution of these with their central black holes, and their impact on the surrounding gas.

I am especially in how we can constraint their contribution of ionising photons and how they leak them into the intergalactic medium, how and when these galaxies enrich their circumgalactic gas in metals (O, C, Mg, Al, Si, etc) which will utlimately become the main building blocks of life (and us!). I also study early quasars and their potential evolution with cosmic time, and like devising new methods to find the earliest ones.

Publications


Recent first author publications - a full publication list can be found here (NASA ADS)!


New Constraints on the Evolution of Quasars: Broad Line Velocity Shifts at 1.5 <z<7.5


We have gathered a comprehensive sample of quasar spanning 5 billion years of cosmic history to study the shift the broad UV emission lines of quasars. We found that the average blueshift of the broad triply-ionised carbon (CIV) line increases by a factor 2.5 as we look at quasars into the reionisation era (z>6). We hypothesize this could be the result of increased obscuration in young, actively accreting quasars resulting in a selection bias towards quasars with highly blueshifted CIV (read the full paper) . The supplementary material for Appendix A can be downloaded here.

The role of AGN and galaxies in reionising
the Universe II: Metal-tracing the sources of reionisation

This study investigates the possiblity to correlate the positions of metal absorbers absorbers (here triply-ionised carbon (CIV)) with ionised patches of the Intergalactic Medium. With a larger sample of 25 sightlines, we find an excess of ionised hydrogen on Megaparec scales around these metal absorbers. We interpret that this excess is caused by faint galaxies beyond the reach of current telescopes contributing to cosmic reionisation with either Lyman Continuum high escape fractions and/or hard radiation cluster around the CIV hosts. Click here to see the published paper.

Upcoming Talks

"A new route to determining the ionising contribution to reionisation of the z~6 faint galaxy population", November 11 , ESO Vitacura, Santiago, Chile
"Probing the epoch of reionisation with cross-correlations of high-redshift galaxies and the IGM transmission", September 18, KICC 10th Anniversary Symposium, Cambridge, UK

Outreach

  • ORBYTS

    I've been a tutor for two years for the ORBYTS program which consists of undergraduate level lectures and hands-on data analysis for highschool students in the UK and abroad. ORBYTS is now a growing UCL-based scheme with 100+ pupils from the UK and abroad participating in 2019!

  • One-off events

    Science is better when it is shared - with other scientists and the general public. I have done several talks for prospective students and younger pupils, but I'm always looking for opportunities to share more about my research and astronomy in general. Drop me an email if you'd be interested to invite me to give a talk!