Understanding the structural scaling relations of early-type galaxies
Abstract
We use a large suite of hydrodynamical simulations of binary galaxy mergers to construct and calibrate a physical prescription for computing the effective radii and velocity dispersions of spheroids. We implement this prescription within a semi-analytic model embedded in merger trees extracted from the Bolshoi Λ cold dark matter N-body simulation, accounting for spheroid growth via major and minor mergers and disc instabilities. We find that without disc instabilities, our model does not predict sufficient numbers of intermediate-mass early-type galaxies in the local Universe. Spheroids also form earlier in models with spheroid growth via disc instabilities. Our model correctly predicts the normalization, slope, and scatter of the low-redshift size-mass and Fundamental Plane relations for early-type galaxies. It predicts a degree of curvature in the Faber-Jackson relation that is not seen in local observations, but this could be alleviated if higher mass spheroids have more bottom-heavy initial mass functions. The model also correctly predicts the observed strong evolution of the size-mass relation for spheroids out to higher redshifts, as well as the slower evolution in the normalization of the Faber-Jackson relation. We emphasize that these are genuine predictions of the model since it was tuned to match hydrodynamical simulations and not these observations.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2014
- DOI:
- 10.1093/mnras/stu1434
- arXiv:
- arXiv:1407.0594
- Bibcode:
- 2014MNRAS.444..942P
- Keywords:
-
- galaxies: elliptical and lenticular;
- cD;
- galaxies: evolution;
- galaxies: formation;
- galaxies: interactions;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- Submitted to MNRAS