{"id":{"repo_id":"cambridge","oai_identifier":"oai:www.repository.cam.ac.uk:1810/391425"},"canonical_url":"https://search.dev.ndltd.org/etd/cambridge/oai:www.repository.cam.ac.uk:1810/391425","repository":{"repo_id":"cambridge","name":"Cambridge University","base_url":"https://api.repository.cam.ac.uk/server/oai/request"},"display":{"title":"Regulating and Quenching Star Formation in Galaxies across the Cosmic Epochs","abstract":"This PhD thesis uncovers the mechanisms regulating and quenching star formation in galaxies from cosmic dawn to the present. Based on optical spectroscopy of 10,000 local galaxies from the MaNGA survey, I report the discovery of a stellar Fundamental Metallicity Relation, a smooth relation between stellar mass, star-formation rate and stellar metallicity, analogous to the well-established gas-phase FMR. The existence of the stellar FMR suggests that the metal-poor gas accreted from the intergalactic/circumgalactic medium – or the lack thereof – is continuously imprinted onto the stars over cosmic times. This discovery points to “starvation”, i.e. the cut-off of gas supply, as the main path through which galaxies stop forming stars, i.e., “quench”, at low redshift. Additionally, I provide evidence that this starvation is likely caused by time-integrated feedback from Active Galactic Nuclei (AGN). In contrast, quenching mechanisms in the young, high-redshift universe may differ significantly. Using groundbreaking data from the James Webb Space Telescope (JWST), I identify an extremely rapidly “(mini-)quenched” galaxy at redshift z=7.3, when the universe was only 700 million years old. Its star-formation history (SFH) consists of a short and intense burst terminating only 10-40 million years before the epoch of observation. Its stellar mass is very low, only 400–600 million solar masses. This suggests that this galaxy was quenched by different physical mechanisms than local galaxies. The most compelling scenarios are ejective feedback from a supermassive black hole or efficient feedback from star formation. Both of these mechanisms may have driven powerful outflows, expelling the gas and depleting the galaxy of its fuel for star formation – perhaps only temporarily, until the gas returns. This finding supports theoretical models, which predict that SFHs were stochastic or 'bursty' during the universe's first billion years. I further test this theoretical hypothesis, based on the analysis of deep JWST NIRSpec prism spectra of ~200 galaxies at redshifts 0.6<z<11. Inferring key physical quantities, such as star-formation rates, stellar masses, stellar ages, or burstiness parameters, I confirm that SFHs were indeed strongly stochastic during these epochs. I conclude by presenting observational strategies to optimize high-redshift galaxy surveys for environmental information, with a particular emphasis on constraining environmental quenching at cosmic noon, when most massive galaxies quench. Overall, this thesis improves our understanding of galaxy evolution, particularly the mechanisms of galaxy quenching from the local universe to the highest redshifts.","abstract_html":"This PhD thesis uncovers the mechanisms regulating and quenching star formation in galaxies from cosmic dawn to the present. Based on optical spectroscopy of 10,000 local galaxies from the MaNGA survey, I report the discovery of a stellar Fundamental Metallicity Relation, a smooth relation between stellar mass, star-formation rate and stellar metallicity, analogous to the well-established gas-phase FMR. The existence of the stellar FMR suggests that the metal-poor gas accreted from the intergalactic/circumgalactic medium – or the lack thereof – is continuously imprinted onto the stars over cosmic times. This discovery points to “starvation”, i.e. the cut-off of gas supply, as the main path through which galaxies stop forming stars, i.e., “quench”, at low redshift. Additionally, I provide evidence that this starvation is likely caused by time-integrated feedback from Active Galactic Nuclei (AGN). In contrast, quenching mechanisms in the young, high-redshift universe may differ significantly. Using groundbreaking data from the James Webb Space Telescope (JWST), I identify an extremely rapidly “(mini-)quenched” galaxy at redshift z=7.3, when the universe was only 700 million years old. Its star-formation history (SFH) consists of a short and intense burst terminating only 10-40 million years before the epoch of observation. Its stellar mass is very low, only 400–600 million solar masses. This suggests that this galaxy was quenched by different physical mechanisms than local galaxies. The most compelling scenarios are ejective feedback from a supermassive black hole or efficient feedback from star formation. Both of these mechanisms may have driven powerful outflows, expelling the gas and depleting the galaxy of its fuel for star formation – perhaps only temporarily, until the gas returns. This finding supports theoretical models, which predict that SFHs were stochastic or &#x27;bursty&#x27; during the universe&#x27;s first billion years. I further test this theoretical hypothesis, based on the analysis of deep JWST NIRSpec prism spectra of ~200 galaxies at redshifts 0.6&lt;z&lt;11. Inferring key physical quantities, such as star-formation rates, stellar masses, stellar ages, or burstiness parameters, I confirm that SFHs were indeed strongly stochastic during these epochs. I conclude by presenting observational strategies to optimize high-redshift galaxy surveys for environmental information, with a particular emphasis on constraining environmental quenching at cosmic noon, when most massive galaxies quench. Overall, this thesis improves our understanding of galaxy evolution, particularly the mechanisms of galaxy quenching from the local universe to the highest redshifts.","abstract_has_math":false,"creators":["Looser, Tobias"],"institution":"University of Cambridge","degree_name":"Doctor of Philosophy (PhD)","degree_level":"Doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":["Maiolino, Roberto","D'Eugenio, Francesco"],"committee_chairs":[],"committee_members":[],"year":2024,"date_issued":"2024-11-15","date_published":"2024-11-15","updated_at":"2026-07-24T01:32:57Z","subjects":["Galaxies","Galaxy feedback","Galaxy formation and evolution","Galaxy quenching","Regulation of star formation"],"languages":["eng"],"rights":[],"rights_urls":["https://www.repository.cam.ac.uk/bitstreams/916ada8f-40d8-488d-9d69-3266bf39041b/download","http://purl.org/NET/rdflicense/allrightsreserved"],"identifier_entries":[]},"links":{"outbound_url":"https://doi.org/10.17863/CAM.122562","outbound_label":"DOI","outbound_source":"dc:identifier.doi"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Maiolino, Roberto","D'Eugenio, Francesco"]},{"key":"dc:contributor.sponsor","label":"Sponsor","values":["Cambridge CDT for Data Intensive Science."]},{"key":"dc:creator","label":"Author","values":["Looser, Tobias"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.issued","label":"Date","values":["2024-11-15"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Cambridge"]},{"key":"dc:relation.isreferencedby.uri","label":"Dc Relation Isreferencedby URI","values":["https://www.repository.cam.ac.uk/handle/1810/391425"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["Doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Doctor of Philosophy (PhD)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Galaxies","Galaxy feedback","Galaxy formation and evolution","Galaxy quenching","Regulation of star formation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["https://www.repository.cam.ac.uk/bitstreams/916ada8f-40d8-488d-9d69-3266bf39041b/download","http://purl.org/NET/rdflicense/allrightsreserved"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.doi","label":"DOI","values":["https://doi.org/10.17863/CAM.122562"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://www.repository.cam.ac.uk/bitstreams/6b5ac5bb-f4bf-46c5-acbf-1a83ce317490/download"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["This PhD thesis uncovers the mechanisms regulating and quenching star formation in galaxies from cosmic dawn to the present. 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Using groundbreaking data from the James Webb Space Telescope (JWST), I identify an extremely rapidly “(mini-)quenched” galaxy at redshift z=7.3, when the universe was only 700 million years old. Its star-formation history (SFH) consists of a short and intense burst terminating only 10-40 million years before the epoch of observation. Its stellar mass is very low, only 400–600 million solar masses. This suggests that this galaxy was quenched by different physical mechanisms than local galaxies. The most compelling scenarios are ejective feedback from a supermassive black hole or efficient feedback from star formation. Both of these mechanisms may have driven powerful outflows, expelling the gas and depleting the galaxy of its fuel for star formation – perhaps only temporarily, until the gas returns. This finding supports theoretical models, which predict that SFHs were stochastic or 'bursty' during the universe's first billion years. I further test this theoretical hypothesis, based on the analysis of deep JWST NIRSpec prism spectra of ~200 galaxies at redshifts 0.6<z<11. Inferring key physical quantities, such as star-formation rates, stellar masses, stellar ages, or burstiness parameters, I confirm that SFHs were indeed strongly stochastic during these epochs. I conclude by presenting observational strategies to optimize high-redshift galaxy surveys for environmental information, with a particular emphasis on constraining environmental quenching at cosmic noon, when most massive galaxies quench. 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Using groundbreaking data from the James Webb Space Telescope (JWST), I identify an extremely rapidly “(mini-)quenched” galaxy at redshift z=7.3, when the universe was only 700 million years old. Its star-formation history (SFH) consists of a short and intense burst terminating only 10-40 million years before the epoch of observation. Its stellar mass is very low, only 400–600 million solar masses. This suggests that this galaxy was quenched by different physical mechanisms than local galaxies. The most compelling scenarios are ejective feedback from a supermassive black hole or efficient feedback from star formation. Both of these mechanisms may have driven powerful outflows, expelling the gas and depleting the galaxy of its fuel for star formation – perhaps only temporarily, until the gas returns. This finding supports theoretical models, which predict that SFHs were stochastic or 'bursty' during the universe's first billion years. I further test this theoretical hypothesis, based on the analysis of deep JWST NIRSpec prism spectra of ~200 galaxies at redshifts 0.6<z<11. Inferring key physical quantities, such as star-formation rates, stellar masses, stellar ages, or burstiness parameters, I confirm that SFHs were indeed strongly stochastic during these epochs. I conclude by presenting observational strategies to optimize high-redshift galaxy surveys for environmental information, with a particular emphasis on constraining environmental quenching at cosmic noon, when most massive galaxies quench. 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