The SAMI–Fornax dwarfs survey:III. evolution of [α/Fe] in dwarfs, from galaxy clusters to the local group

• Main Authors: Romero-Gómez, J. (J), Peletier, R. F. (Reynier F), Aguerri, J. A. (J A L), Mieske, S. (Steffen), Scott, N. (Nicholas), Bland-Hawthorn, J. (Joss), Bryant, J. J. (Julia J), Croom, S. M. (Scott M), Eftekhari, F. S. (F Sara), Falcón-Barroso, J. (Jesús), Hilker, M. (Michael), van de Ven, G. (Glenn), Venhola, A. (Aku)
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press 2023
• Subjects: galaxies: abundances; galaxies: clusters: general; galaxies: dwarf; galaxies: fundamental parameters; sami
• Online Access: http://urn.fi/urn:nbn:fi-fe20230929137865

Abstract Using very deep, high spectral resolution data from the SAMI Integral Field Spectrograph, we study the stellar population properties of a sample of dwarf galaxies in the Fornax Cluster, down to a stellar mass of 10⁷ M⊙, which has never been done outside the Local Group. We use full spectral fitting to obtain stellar population parameters. Adding massive galaxies from the ATLAS3D project, which we re-analysed, and the satellite galaxies of the Milky Way, we obtained a galaxy sample that covers the stellar mass range 10⁴–10¹² M⊙. Using this large range, we find that the mass–metallicity relation is not linear. We also find that the [α/Fe]-stellar mass relation of the full sample shows a U-shape, with a minimum in [α/Fe] for masses between 10⁹ and 10¹⁰ M⊙. The relation between [α/Fe] and stellar mass can be understood in the following way: when the faintest galaxies enter the cluster environment, a rapid burst of star formation is induced, after which the gas content is blown away by various quenching mechanisms. This fast star formation causes high [α/Fe] values, like in the Galactic halo. More massive galaxies will manage to keep their gas longer and form several bursts of star formation, with lower [α/Fe] as a result. For massive galaxies, stellar populations are regulated by internal processes, leading to [α/Fe] increasing with mass. We confirm this model by showing that [α/Fe] correlates with clustercentric distance in three nearby clusters and also in the halo of the Milky Way.