Thomas Herard-Demanche


🖥 Office 470 (Oort Building)


PhD candidate at Leiden Observatory (Sterrewacht Leiden) under the supervision of Rychard Bouwens and Jacqueline Hodge

My research is about finding and studying the properties of high-redshift galaxies, to characterise how these massive object build-up their stellar mass in the Epoch of Reionisation. I am trying to learn how they form and evolve through cosmic time by using powerful ground-based radio and infrared space telescopes like ALMA and JWST.


Star Formationg Histories of Massive Quiescent Galaxies

During my Master's thesis at the Cosmic DAWN Center in Copenhagen, I used Prospector, a new SED-fitting tool which has a non-parametric approach to reconstructing the star formation histories of galaxies, to compare its results with standard parametric methods like EAZY and LePhare. The main goal was to determine whether more accurate predictions on the stellar mass, redshift and other properties (like metallicity and dust content) could be made using it depending on the amount of information available for the source. A sample of high redshift quiescent galaxies in the COSMOS field was the starting point of this analysis to prepare for their upcoming spectroscopic observation with X-Shooter on the VLT. I showed that while photometry was enough to constrain stellar masses and quiescence (sSFR), the spectrum contained valuable information to constrain the star formation history. Moreover, EAZY proved more efficient than Prospector to give an estimation of redshift when only photometry is available for these objects.


Georgios Magdis, Francesco Valentino