1. 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.
- Author
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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, and Foster, Caroline
- Subjects
DISTRIBUTION of stars ,GALAXIES ,OPTICAL spectroscopy ,GALACTIC evolution ,MEDIAN (Mathematics) ,GALAXY mergers ,STELLAR mass - 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 h
4 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. [ABSTRACT FROM AUTHOR]- Published
- 2023
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