Evolution in the orbital structure of quiescent galaxies from MAGPI, LEGA-C, and SAMI surveys: direct evidence for merger-driven growth over the last 7 Gyr

• Published in: Monthly Notices of the Royal Astronomical Society
• Main Authors: D’Eugenio, Francesco, van der Wel, Arjen, Piotrowska, Joanna M, Bezanson, Rachel, Taylor, Edward N, van de Sande, Jesse, Baker, William M, Bell, Eric F, Bellstedt, Sabine, Bland-Hawthorn, Joss, Bluck, Asa F L, Brough, Sarah, Bryant, Julia J, Colless, Matthew, Cortese, Luca, Croom, Scott M, Derkenne, Caro, van Dokkum, Pieter, Fisher, Deanne, Foster, Caroline, Gallazzi, Anna, de Graaff, Anna, Groves, Brent, van Houdt, Josha, del P. Lagos, Claudia, Looser, Tobias J, Maiolino, Roberto, Maseda, Michael, Mendel, J Trevor, Nersesian, Angelos, Pacifici, Camilla, Poci, Adriano, Remus, Rhea-Silvia, Sweet, Sarah M, Thater, Sabine, Tran, Kim-Vy, Übler, Hannah, Valenzuela, Lucas M, Wisnioski, Emily, Zibetti, Stefano
• Other Authors: ERC, Science and Technology Facilities Council, Australian Research Council
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2023
• Subjects: sami
• Online Access: http://dx.doi.org/10.1093/mnras/stad800; https://academic.oup.com/mnras/article-pdf/525/2/2789/56261508/stad800.pdf

ABSTRACT We present the first study of spatially integrated higher-order stellar kinematics over cosmic time. We use deep rest-frame optical spectroscopy of quiescent galaxies at redshifts z = 0.05, 0.3, and 0.8 from the SAMI, MAGPI, and LEGA-C surveys to measure the excess kurtosis h4 of the stellar velocity distribution, the latter parametrized as a Gauss-Hermite series. Conservatively using a redshift-independent cut in stellar mass ($M_\star = 10^{11}\, \mathrm{M_\odot }$) and matching the stellar-mass distributions of our samples, we find 7σ evidence of h4 increasing with cosmic time, from a median value of 0.019 ± 0.002 at z = 0.8 to 0.059 ± 0.004 at z = 0.06. Alternatively, we use a physically motivated sample selection based on the mass distribution of the progenitors of local quiescent galaxies as inferred from numerical simulations; in this case, we find 10σ evidence. This evolution suggests that, over the last 7 Gyr, there has been a gradual decrease in the rotation-to-dispersion ratio and an increase in the radial anisotropy of the stellar velocity distribution, qualitatively consistent with accretion of gas-poor satellites. These findings demonstrate that massive galaxies continue to accrete mass and increase their dispersion support after becoming quiescent.