Exploring the Origins of Galaxy Bimodality at z<0.1

Post-starburst Galaxies (PSBs) are characterised by a lack of massive, young blue stars and a large fraction of intermediate mass A- and F-type stars. They are interpreted as a population of galaxies which have recently undergone a major episode of star formation, and their study may elucidate the nature of galaxy bimodality. We employ a principal component analysis to study a sample of 32 low redshift (0.01 < z < 0.11) PSBs selected with SDSS DR 7 single-fibre spectroscopy and observed with MaNGA integral field spectroscopy. Morphologies are examined to characterise the sample, finding a mixture of starforming and quiescent parameters, indicative of tran- sition. We find that this rich sample exhibits strong radial gradients in stellar age, as measured by the principal components (PC) corresponding to the 4000-Å break strength and excess Hδ absorption. To examine the extent of aperture bias, we com- pare these two properties between the DR 7 and MaNGA spectra, integrated over 3" and the full aperture, finding evidence for systematics and radial gradients. We em- ploy two stellar population synthesis codes (BC03, FSPS) to test the manner in which star-formation proceeded, either as a single radially evolving burst, or coeval with varying burst strengths. Achieved here for the first time, we find a remarkable consistency between the models and gradients, suggesting complex and diverse star-formation histories. We show that this method, coupled with an increased sample size, is well-suited to elucidate the real nature of these strange and peculiar objects.

John R. Weaver
John R. Weaver
PhD Fellow in Astrophysics

My research interests lie almost exclusively within the realm of extragalactic astrophysics and cosmology. I use state-of-the-art optical and infrared observatories and surveys to study the lives of galaxies, and how their properties change over cosmic time. This includes detailed case studies of individual galaxies, as well as statistical analyses of large survey catalogs.

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