Cosmologie, Univers primordial, origine et évolution des grandes structures de l’Univers et des galaxies
Molecular gas in Super Spiral Galaxies
Massive galaxies with stellar masses >10^11 M⊙ are thought to be red and dead quenched galaxies, ie Dekel et al. (2009). They generally lie in clusters or groups. It is thought that environmental-quenching (ram- pressure stripping, collisions, tidal stripping) or mass-quenching (most generally associated to AGN–feedback) have affected their gas content and prevented them from forming stars. However, Ogle et al. (2016; 2019) have found that 6% of the most optically luminous galaxies below a redshift of 0.3 are extremely massive, giant Super Spiral galaxies, with very high SFR for their mass. As such, they look like gigantic (55-140 kpc) massive un-quenched galaxies. Those objects are thus perfect sources to challenge mass-quenching scenarios, one key question being to determine whether those galaxies are as efficient to form stars as their smaller version, the Main Sequence spirals.
The millimeter window is a unique opportunity to measure the gas content of these objects. Indeed, the fuel for star formation lies in the form of molecular gas, visible in the mm/submm domain. Understanding the star formation in these objects needs a better knowledge of their gas content. This has never been investigated yet.
The mission of the internship fellow will be to reduce and analyse IRAM/NOEMA observations of CO(1-0) emission line in one Super Spiral. The gas is clearly detected and stands in a molecular disk. The work will consist in deriving resolved galactic properties of the cold gas (mass, depletion time, kinematics and morphology) and to compare it to ancillary data (for extracting stellar masses and SFR).
This work is part of a pilot project with 4 more sources scheduled to be observed with the interferometer. So the methods and tools developed should be standard enough for further analysis (when the other data will be available, likely along the internship). These sources are also currently being observed in the cm-domain with the Nancay Radio Telescope, in order to search for HI emission. This is much more challenging because of strong RFI at redshifted 21cm frequencies. The fellow will also participate in the reduction and analysis of these data if the data are available.
The results coming out of this work will help prepare the strategy for the future : probing the gas properties of these objects is a completely open area. The internship fellow with thus also participate to proposals preparation.
Observatoire de Paris – 75014
UMR-8112 LERMA, Laboratoire d’étude du rayonnement et de la matière en astrophysique et atmosphères, Paris
Starting date (to be defined) 2022-03-01
Supervisor : Philippe Salomé (Chercheur ou enseignant-chercheur en poste) philippe.salome@observatoiredeparis.psl.eu 33 1 40512103
co-Supervisor : Francoise Combes
