Examining low mass galaxy evolution through SDSS-IV MaNGA spatially resolved spectroscopy

Astronomy Unit Seminars
Samantha Penny
Alkistis Pourtsidou
April 27th, 2018 at 14:30
GO Jones Room 610

Despite being the dominant galaxy population by number in the nearby Universe, the formation timescale and mechanism of lower mass galaxies, including dwarf elliptical galaxies, remains unknown. Are quenched dwarfs the remnants of hierarchical galaxy assembly, or are they formed at later times via the morphological transformation of more massive galaxies? Do they only quench through environmental processes? To address this question requires spatially-resolved spectroscopy to uncover their kinematics and formation timescale. Using data from the first two years of the SDSS-IV MaNGA IFU survey, we identify a sample of 69 quenched dwarf galaxies fainter than Mr = -19, selected independently of morphology and environment. This is the first large scale Integral Field Unit (IFU) study of such galaxies outside of the cluster environment. I will show the majority of quenched dwarfs exhibit coherent rotation in their stellar kinematics, and several host disc or spiral features, inconsistent with a primordial origin. Several exhibit kinematically distinct cores which must form via gas infall and accretion. I will discuss an origin for these dwarfs as quenched low-mass disc/spiral galaxies, supporting the hypothesis that galaxy-galaxy or galaxy-group interactions quench star formation in low mass galaxies. I will also show that a number of bright dEs with signatures of gas accretion host AGN, which are likely maintaining their quiescence. Despite being the "simplest" galaxies in our current models of galaxy formation, quenched dwarf galaxies are a diverse population, with further detailed spectroscopy and modelling needed to understand their origin.