Redshift evolution of the Fundamental Plane relation in the IllustrisTNG simulation
Abstract
We investigate the Fundamental Plane (FP) evolution of earlytype galaxies in the IllustrisTNG100 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 ∝ σ^{b}I^{c} 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 + b log σ + c log I  log R, where a is the zeropoint 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 powerlaw relation between the dynamical masstolight ratio M_{dyn}/L and the dynamical mass M_{dyn} (where M_{dyn} ≡ 5σ^{2}R/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.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2020
 DOI:
 10.1093/mnras/staa173
 arXiv:
 arXiv:1906.00927
 Bibcode:
 2020MNRAS.492.5930L
 Keywords:

 methods: numerical;
 galaxies: elliptical and lenticular;
 cD;
 galaxy: evolution;
 galaxies: formation;
 galaxy: kinematics and dynamics;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 10 pages, 7 figures, 1 table. Accepted for publication in MNRAS