The origin and fate of post-starburst galaxies : morphological and structural image analysis of local galaxies with recent episodes of enhanced star formation

Stars--Formation;Galaxies--Evolution

Pawlik, Milena ; Wild, Vivienne ; Wild, Vivienne

University:University of St Andrews

Department:Physics & Astronomy (School of)

关键词: Stars--Formation;    Galaxies--Evolution;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/9902/MilenaPawlikPhDThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

Post-starburst galaxies are a rare class of objects with unusual spectroscopic characteristics.Previous studies have shown that the presence of strong Balmer absorption lines in the spectraof these galaxies are consistent with a recent bust of star formation; however, the cause of suchevents remains unclear. Their environment and disturbed morphology suggest that many ofthem are likely remnants of gas-rich mergers of galaxies with comparable masses and modelsof galaxy mergers support that claim; however, some studies disagree and the origin of thesecurious systems remains an open debate. Post-starburst galaxies are also often regarded asa plausible transition channel between the blue continuously star-forming and quiescent redgalaxies, commonly observed in the local Universe. This is supported by models of merger-driven starbursts, which cause structural transformation of galaxies consistent with evolutiontowards the red population, and can ultimately lead to quenching of star formation in themerger remnant; however, observational evidence for this scenario remains elusive.In my study I aimed to place further constraints on the role of galaxy mergers in triggering starbursts in local galaxies and to investigate whether the post-starburst galaxies areindeed in transition between the star-forming and passive phases of galaxy evolution, by theanalysis of the morphology and structure of galaxies with spectroscopic signatures of a recent starburst. An important difference between this work and many previous studies is thepost-starburst sample selection. Traditionally, post-starburst galaxies are selected to have completely quenched their star-formation; here, I also considered those which show spectroscopicsign of residual star-formation, selected using a method introduced by Wild et al. (2007). Ihave also followed a different approach to quantifying the morphology of galaxies, by meansof an automated method for detecting visual post-merger signatures in galaxies, introduced asa part of this work. My analysis suggests that major mergers play a significant role in inducingstarbursts in local Universe, but their significance declines as a function of the stellar mass ofthe galaxies. I also found that post-starburst galaxies have different structural properties in thelow- and high-mass regimes and concluded that they are likely to be transitioning between theblue and red galaxy populations through a multi-stage scenario where both major and minormergers are at play.