Status Report

The Formation of a Disk Galaxy within a Growing Dark Halo

By SpaceRef Editor
January 30, 2003
Filed under , ,

Astrophysics, abstract

From: Markus Samland <[email protected]>
Date: Fri, 24 Jan 2003 15:33:17 GMT (635kb)

The Formation of a Disk Galaxy within a Growing Dark Halo

Markus Samland,
Ortwin Gerhard (Astronomisches Institut, University Basel, Switzerland)

Comments: 23 pages, LaTeX, 18 figures, A&A accepted, a high resolution version
of the paper can be found at this http URL

We present a dynamical model for the formation and evolution of a massive
disk galaxy, within a growing dark halo whose mass evolves according to
cosmological simulations of structure formation. The galactic evolution is
simulated with a new 3D chemo-dynamical code, including dark matter, stars and
a multi-phase ISM. The simulations start at redshift z=4.85 with a small dark
halo in a LCDM universe and we follow the evolution until the present epoch.
The energy release by massive stars and SNe prevents a rapid collapse of the
baryonic matter and delays the maximum star formation until z=1. The galaxy
forms radially from inside-out and vertically from halo to disk. The first
galactic component that forms is the halo, followed by the bulge, the disk-halo
transition region, and the disk. At z=1, a bar begins to form which later turns
into a triaxial bulge. There is a pronounced deficiency of low-metallicity disk
stars due to pre-enrichment of the disk ISM with metal-rich gas from the bulge
and inner disk (G-dwarf problem). The mean rotation and the distribution of
orbital eccentricities for all stars as a function of metallicity are not very
different from those observed in the solar neighbourhood, showing that
homogeneous collapse models are oversimplified. The approach presented here
provides a detailed description of the formation and evolution of an isolated
disk galaxy in a LCDM universe, yielding new information about the kinematical
and chemical history of the stars and the ISM, but also about the evolution of
the luminosity, the colours and the morphology of disk galaxies.

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