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Home   /   Thesis   /   Understanding the formation of bulges based on morphology and kinematics information from JWST

Understanding the formation of bulges based on morphology and kinematics information from JWST

Astrophysics Corpuscular physics and outer space


Present-day bulges of spiral galaxies and elliptical galaxies contain very old stars and are thought to be formed in the early Universe. How this actually happened in practice is not well understood, and the most relevant physical processes at play are still unclear. In the last decade, evidence has been growing of the existence of compact star bursting galaxies that might be signposts of bulges caught at the event of formation. More recently, also thanks to new findings from our group based on JWST, a number of further puzzling results has accumulated, currently difficult to explain: A) these star-bursting galaxies are always embedded in larger disk-like systems that are less active but contain most of the existing stellar mass, as if there was no ’naked’ bulge formation; B) in some cases, the outer disks have actually stopped forming stars, thus representing cases of quenching progressing from the outside-in, reversing the standard more familiar pattern (as observed in local spirals and the MilkyWay, where the center is quenched and the outskirts are forming stars); C) the disks are often strongly lopsided in their stellar mass distribution, a feature becoming more and more dominant when looking at earlier times. This phenomenology is currently unexplained. It could be related to merging activity, gas accretion or also feedback effects. If these are forming bulges, how they would evolve in present-day bulges and elliptical galaxies is unclear. Still, these new challenging observations promise breakthrough in the understanding of bulge formation if more progress can be made and further insight gathered. We propose a PhD project where the student will be using imaging and spectroscopy data from JWST to illuminate these issues. Imaging from deep and ultra deep public surveys that is accumulating will be used to increase the statistics and put on more solid grounds the early results gathered so far. The spectroscopy from JWST holds the key to detailed understanding of specific systems, providing information on kinematics of the compact star bursting cores as well as of the outer disks: if these subsystems are co-rotating without major disturbances would support non violent, gas accretion related evolution. On the contrary, counter-rotating subsystems or kinematics disturbances would betray merging events. This kind of test has not yet been carried out. We will use targeted spectroscopy in part already available from the Early-Release project CEERS of which we are members, from the large archive that is accumulating, and from dedicated proposals (pending, and to be submitted in future cycles).


Institut de recherche sur les lois fondamentales de l’univers
Direction d’Astrophysique
Laboratoire de Cosmologie et d’Evolution des Galaxies
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