Quenching mechanisms in recently quenched elliptical galaxies: insights from neutral hydrogen studies and environmental analysis
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Recently Quenched Elliptical galaxies (RQEs) represent a critical phase in the transition from star-forming to quiescent galaxies. However, the mechanisms driving their quenching remain elusive. We conduct a multi-wavelength analysis of 695 RQEs, along with their precursors (preRQEs) and descendants (postRQEs), focusing on their neutral hydrogen (HI) content and star formation properties. Contrary to conventional quenching models emphasizing gas depletion, RQEs retain substantial HI reservoirs (fgas ≥ 17%), suggesting that quenching is not primarily driven by gas exhaustion. We identify a critical halo mass threshold at log(Mhalo) = 12.1 M⊙, delineating different evolutionary pathways for RQEs. This threshold aligns with the transition from cold-mode to hot-mode gas accretion in theoretical models. RQEs in lower-mass halos (log Mhalo < 12.1M⊙) likely experience rapid quenching, possibly initiated by major mergers, followed by brief AGN activity and sustained LINER emission. We propose two evolutionary pathways: (a) rapid quenching via major mergers followed by AGN/LINER activity and passive evolution, and (b) rapid quenching followed by rejuvenation through minor mergers before evolving into more massive, long-term quenched ellipticals. These results challenge the conventional understanding of galaxy quenching, especially in low-density environments where RQEs typically reside. Our findings suggest that while RQEs may follow a rapid quenching pathway, their evolution is influenced by interactions between gas accretion modes, feedback mechanisms, and environmental factors. Future observations with advanced radio interferometers like SKA will be crucial for elucidating the quenching mechanisms in RQEs and their role in galaxy evolution.
Table of Contents
Investigating quenching in recently quenched elliptical galaxies with HI studies -- Re-examining the environmental status of recently quenched ellipticals: a multi-scale analysis of their
true nature as central galaxies -- Design and development of an introductory undergraduate course on radio astronomy
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Ph.D. (Doctor of Philosophy)