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Journal Article

Redshift evolution of the Fundamental Plane relation in the IllustrisTNG simulation


Springel,  Volker
Computational Structure Formation, MPI for Astrophysics, Max Planck Society;

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Lu, S., Xu, D., Wang, Y., Mao, S., Ge, J., Springel, V., et al. (2020). Redshift evolution of the Fundamental Plane relation in the IllustrisTNG simulation. Monthly Notices of the Royal Astronomical Society, 492(4), 5930-5939. doi:10.1093/mnras/staa173.

Cite as: https://hdl.handle.net/21.11116/0000-0006-71EE-F
We investigate the Fundamental Plane (FP) evolution of early-type galaxies in the IllustrisTNG-100 simulation (TNG100) from redshift z = 0 to z = 2. We find that a tight plane relation already exists as early as z = 2. Its scatter stays as low as ∼0.08 dex across this redshift range. Both slope parameters b and c (where R ∝ σbIc with R, σ, and I being the typical size, velocity dispersion, and surface brightness) of the plane evolve mildly since z = 2, roughly consistent with observations. The FP residual Res (⁠≡a+blogσ+clogI−logR⁠, where a is the zero-point of the FP) is found to strongly correlate with stellar age, indicating that stellar age can be used as a crucial fourth parameter of the FP. However, we find that 4c + b + 2 = δ, where δ ∼ 0.8 for FPs in TNG, rather than zero as is typically inferred from observations. This implies that a tight power-law relation between the dynamical mass-to-light ratio Mdyn/L and the dynamical mass Mdyn (where Mdyn ≡ 5σ2R/G, with G being the gravitational constant) is not present in the TNG100 simulation. Recovering such a relation requires proper mixing between dark matter and baryons, as well as star formation occurring with correct efficiencies at the right mass scales. This represents a powerful constraint on the numerical models, which has to be satisfied in future hydrodynamical simulations.