Thèse Evolution du Taux de Fusion des Galaxies et de leurs Trous Noirs Centraux Depuis 12.5 Milliards d'Années H/F - Doctorat_Gouv

Établissement : Université de Toulouse École doctorale : SDU2E - Sciences de l'Univers, de l'Environnement et de l'Espace Laboratoire de recherche : IRAP - Institut de Recherche en Astrophysique et Planetologie Direction de la thèse : Thierry CONTINI ORCID 000000030275938X Début de la thèse : 2026-10-01 Date limite de candidature : 2026-06-01T23:59:59 Notre compréhension de la genèse des trous noirs massifs (MBH) et de leur évolution au cours du temps cosmique fera un bond en avant dans les prochaines décennies grâce aux ondes gravitationnelles qui seront captées par LISA. Cependant, les prédictions du taux de fusion des MBH et leurs détections par LISA sont basées jusqu'à présent uniquement sur des simulations cosmologiques, qui ne résolvent pas encore le régime des galaxies naines (M*10^5 M) binaries range from ~1 to 75 Gyr^-1 (e.g. Chen+22) depending on the simulation parameters (eg. delays between the merger of galaxies and the final coalescence of their MBH, effect of supernovae feedback on MBH growth, etc) and resolution. But, in the context of LISA's science, these cosmological simulations do not resolve dwarf galaxies (Mstars<10^9 M) and are thus underestimating the merger rate of LISA's MBH mergers. On the side of the LISA data analysis and parameter estimation for these signals, much remain to be explored. In particular, asymmetric galaxy mergers might lead to high mass ratios binaries (20-100), a range where our theoretical understanding of waveforms is limited and where data analysis remains uncharted. In turn, depending on their accuracy, the measurements of the masses and spins of MBH systems by LISA will enrich our understanding of the formation of MBHs as well as their co-evolution with their host galaxies. The goal of this PhD thesis is to make a step forward into the prediction of MBH coalescences that should be detected with the LISA interferometer, and to simulate the detection and parameter recovery of these MBHs by LISA. Such predictions can now be based not only on simulations but on measurements of the galaxy merger rate, such as those performed by our team at IRAP in the first MUSE deep fields (Ventou+17,19) over 12.5 Gyrs of galaxy evolution (ie. from redshift z~0.2 to 6) and covering a broad range of galaxy stellar masses (10^7-10^11M), thus extending into the dwarf galaxy regime not probed so far by cosmological simulations. Simulating the LISA data analysis for the predicted MBHs will tell us which scientific information will be extracted by LISA according to these new predictions. To achieve these objectives, the PhD student will first assemble and analyse the properties of a large sample of galaxy pairs over a broad redshift range (0.2 < z < 6), thus probing about 12.5 Gyrs of galaxy evolution. This dataset will be collected from various MUSE observations obtained by our MUSE-GTO (Guaranteed Time Observations) European collaboration. By combining (extremely-)deep MUSE data acquired in limited field-of-views, such as the MUSE-Hubble Ultra Deep Field (Bacon+17, Inami+17), with shallower observations over a larger area (e.g. the MUSCATEL survey completed recently), she(he) will be able to identify and characterize hundreds of close pairs of galaxies spread over five orders of magnitude in stellar mass (~10^7-10^11M). These 3D spectroscopic observations will be complemented with publicly available HST or JWST high-resolution images and extensive photometry in cosmological fields such as HUDF, Frontier Fields, CANDELS and COSMOS. From the MUSE data, the PhD student will produce catalogs of galaxy pairs following and improving the procedures developed by our team (Ventou+17,19, Contini+22, Delpech+24). She/he will thus make predictions about MBH mergers hosted by these galaxies, as a function of redshift, galaxy masses, mass ratios, and environment. She/he will then simulate the detection and extraction of the parameters of this population of binaries by LISA. This will be achieved by using existing tools for comparable-mass binaries (Marsat+20), and by developing new (possibly approximate) LISA data analysis techniques in the yet unexplored range of high mass ratio binaries.

- Connaissance de l'astrophysique extragalactique et/ou des ondes gravitationnelles
- Bonne connaissance en programmation (Python, C++, etc)
- Goût pour l'analyse de données
- Aptitudes à travailler en équipe