PhD defense: Gayathri Gururajan

“Probing the gas reservoirs of high redshift, dusty star-forming galaxies using ALMA observations of atomic carbon”

Here is the zoom link for those who are willing to attend remotely :
https://univ-amu-fr.zoom.us/j/7585591256

Abstract:
Intensely star-forming (> 500 M⦿/yr) dusty galaxies are found in the early Universe, and many questions regarding their formation and mass assembly remain open. In this thesis, we study a population of such galaxies from the South pole telescope – sub-millimeter galaxies (SPT-SMG) sample using Atacama large millimeter/sub-millimeter array (ALMA). We focus on characterising the gas reservoirs of these dusty galaxies to understand their prodigious star-formation rates. We focus on the neutral carbon emission lines as it is a promising alternative tracer to the traditionally used carbon monoxide lines. In the first part of this thesis, we study a sample of 29 galaxies with a rich ancillary data of multiple emission lines. Through this sample, we compare the ability of [CI], CO, and dust as a tracer of the gas reservoirs in these galaxies. We cross-calibrate the 𝜶CO, XCI, and 𝜹GDR and find a good agreement between them. In addition, we constrain the radiation field intensity, densities and the kinetic temperatures of the ISM using line ratios. In the second part of the thesis, we focus on higher-resolution imaging of 3 such galaxies to further understand their morphologies and resolved ISM properties to further investigate on the nature of intensely star-forming dusty galaxies at high-redshifts. We find diverse source kinematics in our sample: SPT0103-45 and SPT2147-50 are likely rotating disks, while SPT2357-51 is possibly a major merger.

Jury :
Veronique BUAT, LAM – President
Pierre COX, IAP – Referee
Georgios Magdis, Cosmic DAWN center – Referee
Nicole Nesvadba, Observatoire de la Côte d’Azur – Examiner
Miroslava Dessauges-Zavadsky, University of Geneva – Examiner
Matthieu Bethermin, LAM – Supervisor
Patrice Theule, LAM – Supervisor
Justin Spilker, Texas A&M university – Invited