The SAMI–Fornax Dwarfs Survey – III. Evolution of [α/Fe] in dwarfs, from Galaxy Clusters to the Local Group

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Romero-Gómez, J., Peletier, Reynier F., Aguerri, J. A. L., Mieske, Steffen, Scott, Nicholas, Bland-Hawthorn, Joss, Bryant, Julia J., Croom, Scott M., Eftekhari, F. Sara, Falcón-Barroso, Jesús, Hilker, Michael, van de Ven, Glenn, Venhola, Aku
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: galaxies: abundances; galaxies: clusters: general; galaxies: dwarf; galaxies: fundamental parameters; Milky Way; sami
• Online Access: https://hdl.handle.net/11370/5913ef21-c481-44d6-89aa-e9629d62db9b; https://research.rug.nl/en/publications/5913ef21-c481-44d6-89aa-e9629d62db9b; https://doi.org/10.1093/mnras/stad953; https://pure.rug.nl/ws/files/771404146/stad953.pdf; http://www.scopus.com/inward/record.url?scp=85160400012&partnerID=8YFLogxK

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 10 7 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 ATLAS 3D project, which we re-analysed, and the satellite galaxies of the Milky Way, we obtained a galaxy sample that covers the stellar mass range 10 4 –10 12 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 10 9 and 10 10 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.