The LEGA-C and SAMI Galaxy Surveys:Quiescent Stellar Populations and the Mass-Size Plane across 6 Gyr

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: Barone, Tania M., D'Eugenio, Francesco, Scott, Nicholas, Colless, Matthew, Vaughan, Sam P., Wel, Arjen van der, Fraser-McKelvie, Amelia, Graaff, Anna de, Sande, Jesse van de, Wu, Po-Feng, Bezanson, Rachel, Brough, Sarah, Bell, Eric, Croom, Scott M., Cortese, Luca, Driver, Simon, Gallazzi, Anna R., Muzzin, Adam, Sobral, David, Bland-Hawthorn, Joss, Bryant, Julia J., Goodwin, Michael, Lawrence, Jon S., Lorente, Nuria P. F., Owers, Matt S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: sami
• Online Access: https://eprints.lancs.ac.uk/id/eprint/167219/; https://eprints.lancs.ac.uk/id/eprint/167219/1/2107.01054v1.pdf; https://doi.org/10.1093/mnras/stac705

We investigate the change in mean stellar population age and metallicity ([Z/H]) scaling relations for quiescent galaxies from intermediate redshift ($0.60\leq z\leq0.76$) using the LEGA-C Survey, to low redshift ($0.014\leq z\leq0.10$) using the SAMI Galaxy Survey. We find that, similarly to their low-redshift counterparts, the stellar metallicity of quiescent galaxies at $0.60\leq z\leq 0.76$ closely correlates with $M_*/R_\mathrm{e}$ (a proxy for the gravitational potential or escape velocity), in that galaxies with deeper potential wells are more metal-rich. This supports the hypothesis that the relation arises due to the gravitational potential regulating the retention of metals, by determining the escape velocity required by metal-rich stellar and supernova ejecta to escape the system and avoid being recycled into later stellar generations. On the other hand, we find no correlation between stellar age and $M_*/R_\mathrm{e}^2$ (stellar mass surface density $\Sigma$) in the LEGA-C sample, despite this being a strong relation at low redshift. We consider this change in the age--$\Sigma$ relation in the context of the redshift evolution of the star-forming and quiescent populations in the mass--size plane, and find our results can be explained as a consequence of galaxies forming more compactly at higher redshifts, and remaining compact throughout their evolution. Furthermore, galaxies appear to quench at a characteristic surface density that decreases with decreasing redshift. The $z\sim 0$ age--$\Sigma$ relation is therefore a result of building up the quiescent and star-forming populations with galaxies that formed at a range of redshifts and so a range of surface densities.