STAGE Timing the quenching of galaxy fertility in groups and clusters

Date de mise à jour de l’offre

CNRS - Institut d'Astrophysique de Paris :

Unité Mixte de Recherche CNRS - Sorbonne Université

Description de la mission

The fertilities of galaxies to form stars are a!ected by several physical processes, both internal and external. Observations indicate that stars form in cold Giant Molecular Clouds, and galaxy star formation (SF) rates correlate well with their molecular mass with a gas consumption time of roughly 2 Gyr. This gas thus needs to be replenished from infalling cold "laments of gas that are visible in hydrodynamical simulations with cosmological initial conditions. Gas can be heated or pushed out by supernova explosions and by the jets from active galactic nuclei surrounding supermassive black holes. Moreover, the infalling gas from the cold "laments will not enter low mass galaxies because its entropy is too low, nor will it enter high mass galaxies because they fall supersonically and are shockheated near the virial radius of the galaxy. Finally, the cold "laments can be stripped by the tidal "eld of the group (or cluster) in which the galaxy resides, as well as by the ram pressure that the di!use hot, X-ray emitting, intra-group gas exerts on them. These different mechanisms slow down, i.e. quench, the SF rates of galaxies.
To decide the relative importance of tides, ram pressure and other mechanisms, one needs to quantify the onset of quenching of SF after group entry and its duration, both versus galaxy mass and host group mass. Several studies, starting with Mahajan et al. (2011), found con#icting results on the time of quenching of SF, hence a state-of-the-art method is required.
This project aims to derive from observations, for the 1st time, the quenching history (rather than just epoch) as a function of galaxy stellar mass, group mass, and epoch of entry in the group. Our model uses a combination of state-of-the-art group "nders applied to subsamples complete in both distance and luminosity, individual SF histories already derived from the SDSS spectra for 600 thousand galaxies, and entry time distributions as a function of projected distance and line-of-sight velocity relative to the host group, previously deduced from cosmological simulations. The student will set up and run the Bayesian framework to determine the quenching history and convert it into a function of orbital phase of the galaxy in its group/cluster. (S)he will then analyze how the results depend on galaxy & group mass, entry time, and on the spectral model previously used to "t the SF histories to the SDSS spectra. (S)he will then deduce the physical mechanisms at work.

Profil recherché

Ease at programming and mathematical formalisms

Niveau de qualification requis

Bac + 4/5 et +
  • Employeur
    CNRS - Institut d'Astrophysique de Paris
  • Secteur d’activité de la structure
    Enseignement - Formation - Recherche
  • Effectif de la structure
    De 51 à 250 salariés
  • Site internet de la structure
  • Type de stage ou contrat
    Stage pour lycéens et étudiants en formation initiale
  • Date prévisionnelle de démarrage
  • Durée du stage ou contrat
    Plus de 4 mois et jusqu'à 6 mois
  • Le stage est-il rémunéré ?
  • Niveau de qualification requis

    Bac + 4/5 et +
  • Lieu du stage
    98 bis Boulevard Arago
  • Accès et transports
    Métro, RER Denfert-Rochereau