Kinematic analysis of EAGLE simulations: Evolution of $λ_{Re}$ and its connection with mergers and gas accretion

We have developed a new tool to analyse galaxies in the EAGLE simulations as close as possible to observations.We investigated the evolution of their kinematic properties by means of the angular momentum proxy parameter,$λ_{Re}$for galaxies with $M_{*} \ge 5 \times 10^{9} M_{\odot}$ in the RefL0100N1504 simulation up to redshift two (z = 2). Galaxies in the simulation show a wide variety of kinematic features, similiar to those found in integral-field spectroscopic studies. At z=0 the distribution of galaxies in the $λ_{Re}-ε$ plane is also in good agreement with results from observations. Scaling relations at z = 0 indicate that there is critical mass, $M_{crit} = 10^{10.3} M_{\odot}$, that divides two different regimes when we include the $λ_{Re}$ parameter. The simulation shows that the distribution of galaxies in the $λ_{Re}-ε$ plane evolves with time until z = 2 when galaxies are equally distributed both in $λ_{Re}$ and $ε$. We studied the evolution of $λ_{Re}$ with time and found that there is no connection between the angular momentum at z = 2 and z = 0. All systems reach their maximum $λ_{Re}$ at z = 1 and then steadily lose angular momentum regardless of their merger history, except for the high star-forming systems that sustain that maximum value over time. The evolution of the Re in galaxies that have not experienced any merger in the last 10 Gyr can be explained by their level of gas accretion.

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