Johan Comparat

Johan Comparat

Chaire de professeur junior in cosmology at Université Grenoble Alpes & LPSC

Johan Comparat

I am an observational cosmologist. Since December 2025 I hold a Chaire de professeur junior at the Université Grenoble Alpes and the Laboratoire de Physique Subatomique et de Cosmologie (LPSC) in Grenoble. My research topic is multi-wavelength cosmology and large-scale structure with a particular focus on exploiting observations from the Euclid and Rubin/LSST observatories.

I study how the large-scale structure of the Universe looks at different wavelengths. I use this to test the cosmological model and to understand how galaxies, their hot gas and their supermassive black holes live together and interact inside dark matter haloes.

Before Grenoble, I was a researcher at the Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching (2017–2025), where I worked on eROSITA, 4MOST, SDSS and LS10 surveys. Before that I was a Severo Ochoa postdoctoral fellow at the Instituto de Física Teórica (UAM-CSIC) in Madrid (2014–2017). I did my PhD at the Laboratoire d’Astrophysique de Marseille (2013), measuring baryon acoustic oscillations with emission-line galaxies. I obtained my habilitation (HDR) from the Université Grenoble Alpes in July 2026.

Research interests

  • Cosmology and large-scale structure: galaxy clustering, cluster counts, weak lensing.
  • Digital twins of the Universe: forward models using machine learning and artificial intelligence tools.
  • Multi-wavelength observations: optical and near-infrared photometry, optical spectroscopy, soft X-rays.
  • Galaxy evolution: the circumgalactic medium, active galactic nuclei, galaxy bimodality.

Collaborations

  • Euclid: Clusters of Galaxies Science Working Group.
  • Rubin Observatory LSST: Dark Energy Science Collaboration and Galaxies Science Collaboration.
  • eROSITA: galaxy clusters and cosmology, AGN, and normal galaxies working groups; end-to-end simulations of the X-ray sky.

In the past I have actively contributed to SDSS-III/BOSS, SDSS-IV/eBOSS and SPIDERS, SDSS-V, 4MOST (now permanent member), DESI, the DESI Legacy Imaging Surveys and MultiDark.

Contact

Johan Comparat
Laboratoire de Physique Subatomique et de Cosmologie (LPSC)
53 avenue des Martyrs
38000 Grenoble, France
Email: jcomparat@lpsc.in2p3.fr