Abstract
In order to investigate the structure and dynamics of the recently discovered massive (M* ≳ 1011M ⊙) compact z ∼ 2 galaxies, cosmological hydrodynamical/N- body simulations of a ∼ 50,000 Mpc3 comoving (Lagrangian), proto-cluster region have been undertaken. At z = 2, the highest resolution simulation contains ∼ 5800 resolved galaxies, of which 509, 27, and 5 have M* > 1010M⊙,M* > 1011M⊙, and M* > 4×10 11M⊙, respectively. Total stellar masses, effective radii, and characteristic stellar densities have been determined for all galaxies. At z = 2, for the definitely well-resolved mass range of M * ≳ 1011M⊙, we fit the relation Reff = Reff,12M 1/3 *,12 to the data, where M*,12 is the total stellar mass in units of 1012M⊙. This yields Reff,12 = (1.20±0.04) kpc, in line with observational findings for compact z ∼ 2 galaxies, though somewhat more compact than the observed average. The only line-ofsight velocity dispersion measured for a z ∼ 2 compact galaxy is very large, σ*,p = 510+165 -95 km s -1. This value can be matched at about the 1σ level, although a somewhat larger mass than the estimated M* ≳ 2 × 1011⊙ is indicated. For the above mass range, the galaxies have an average axial ratio <b/a> = 0.64±0.02 with a dispersion of 0.1, and an average rotation to one-dimensional velocity-dispersion ratio <v/σ> = 0.46±0.06 with a dispersion of 0.3, and a maximum value of v/σ ≃ 1.1. Both rotation and velocity anisotropy contribute significantly in flattening the compact galaxies. Some of the observed compact galaxies appear flatter than any of the simulated galaxies. Finally, it is found that the massive compact galaxies are strongly baryon dominated in their inner parts, with typical dark matter mass fractions of order only 20% inside of r = 2Reff .
| Original language | English |
|---|---|
| Journal | Astrophysical Journal |
| Volume | 721 |
| Issue number | 2 |
| Pages (from-to) | 1755-1764 |
| Number of pages | 9 |
| ISSN | 0004-637X |
| DOIs | |
| Publication status | Published - 1 Oct 2010 |