The spatial distribution and kinematics of cool interstellar medium (dust and molecular gas) within early-type galaxies (ETGs) can be used to highlight mechanisms causing galaxy evolution. For example, asymmetries and spatial or kinematic misalignments of cool ISM compared to stellar discs can be used to indicate recent merger activity. High-resolution mm-wavelength observations can reveal the spatial distribution of cool ISM, and allow ISM kinematics to be explored.
ALMA observations were obtained in 2016 of continuum and 12CO(2-1) line emission for a sample of five ETGs in the GAMA equatorial fields with redshifts ~0.04, drawn from a clean and complete sample of visually-classified ETGs. The sample was chosen to have relatively high dust content (10^7.5 – 10^8 Mʘ) determined using Herschel-ATLAS data. The observations revealed massive (~few x 10^9 Mʘ) extended molecular gas reservoirs in three ETGs.
This poster presents the findings from the modelling of molecular gas kinematics for the three ETGs with massive gas reservoirs, using the KINematic Molecular Simulation (KinMS) package. Axisymmetric single-component models are fitted to ALMA data to highlight additional structural components and any asymmetry. The models also allow examination of potential star formation in the cool molecular gas. Kinematic alignments of molecular gas, stars and ionised gas are also compared, using data from the SAMI galaxy survey. Scenarios for the evolutionary history of these ETGs are discussed using the findings. Future work based on results from these observations is also discussed, along with the possibilities for further observations.