Kavli Affiliate: Yingjie Peng
| First 5 Authors: Caro Derkenne, Richard M. McDermid, Francesco D’Eugenio, Caroline Foster, Aman Khalid
| Summary:
We use the `Middle Ages Galaxy Properties with Integral field spectroscopy’
(MAGPI) survey to investigate whether galaxies have evolved in the distribution
of their stellar angular momentum in the past 3-4 Gyr, as probed by the
observational proxy for spin, $lambda_{R}$. We use 2D stellar kinematics to
measure $lambda_{R}$ along with detailed photometric models to estimate galaxy
ellipticity. The combination of these measurements quantifies the kinematic
classes of `fast rotators’ and the rarer `slow rotators’, which show no regular
rotation in their line-of-sight velocity fields. We compare 51 MAGPI galaxies
with $log_{10} (M_{star}/mathrm{M}_odot) > 10$ to carefully drawn samples
of MaNGA galaxies in the local Universe, selected to represent possible
descendants of the MAGPI progenitors. The EAGLE simulations are used to
identify possible evolutionary pathways between the two samples, explicitly
accounting for progenitor bias in our results and the varied evolutionary
pathways a galaxy might take between the two epochs. We find that the
occurrence of slow rotating galaxies is unchanged between the MAGPI ($z sim
0.3$) and MaNGA ($z sim 0$) samples, suggesting the massive slow rotator
population was already in place $sim 4$ Gyr ago and has not accumulated since.
There is a hint of the MAGPI sample having an excess of high $lambda_{R}$
galaxies compared to the MaNGA sample, corresponding to more ordered rotation,
but statistically the samples are not significantly different. The large-scale
stellar kinematics, as quantified through the $lambda_{R}$ parameter, of
galaxies at $z sim 0.3$ have already evolved into the diversity of structures
seen today in the local Universe.
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