Mass density structuring around galaxy formation sites: impact on galaxy basic properties

Abstract

We study the local evolution of the Universe around galaxy formation sites in the EAGLE50 large-volume reference simulation. Using the reduced inertia tensor (r-TOI), we followed the anisotropic evolution of initially spherical Lagrangian volumes (LVs) centred at galaxy formation sites, both in dark matter (DM) and in cold baryons (CB), from very high redshift $z=15$ onward. We describe LV deformation in terms of the r-TOI eigen-directions, principal axes, their derived shape parameters, and the timescales for the freezing-out of these principal directions and axes. Of particular interest are the age of the Universe, $t_{\rm U}$, when the local Cosmic Web (CW) spine emerges, and that when anisotropic DM mass arrangements (i.e., migrant mass flows) cease. We find that the shapes LVs acquire along their evolution affect the halo and stellar mass of their central galaxy: prolate-shaped LVs show a tendency to host low-mass galaxies at $z=0$, while massive galaxies tend to form within triaxial or oblate LVs. Also, the local CW spine tends to set in earlier on in LVs that are to host massive galaxies than in those harbouring less massive galaxies. In addition, anisotropic DM-mass rearrangements stop late on average, at $t_{\rm U}\sim 10.5\,$Gyr, and even slightly later for CB. Interestingly, $z=0$ LVs with either flattened configurations in CB or those that are highly prolate in DM, are more likely to host rotation-dominated galaxies. This effect increases from $z=1$ to $z=0$. Finally, the CB spine of LVs that are more likely to host rotation-dominated galaxies emerges at later times.

Figures (19)

• Figure 1: Upper panels show the radius and mass distribution of the galaxy haloes selected at $z=0$. Lower panels depict the mass and radius of the corresponding LV sample.
• Figure 2: Example of the evolution of the three eigen-directions of the reduced inertia tensor calculated considered all particle species (tot).
• Figure 3: Evolution of the distribution of eigen-directions across redshifts, where $A_i^\mathrm{tot}$ is the angle formed by the eigenvectors $\hat{e}_i^{\rm tot}(z)$ and $\hat{e}_i^{\rm tot}(z=0)$, with $i=1,2,3$, and where '$\rm tot$' stands for the eigenvectors of the $I_{ij}^{\rm r}$, calculated with all the particles within a LV.
• Figure 4: Evolution of the distributions of the angles formed by the direction of the major axis of inertia that arises from the overall mass distribution $\hat{e}_1^\mathrm{tot}(z)$ and the corresponding eigen-direction calculated with one the following components: DM (left), cold baryons (middle) and hot gas (right).
• Figure 5: Evolution of the principal axes of the inertia ellipsoid for a wall-like LV (top) and a LV with evolves into a filamentary shape (bottom), where 'tot' stands for the total mass of the LV. i.e. all particles species.