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The Formation of a Realistic Disk Galaxy in Lambda Dominated Cosmologies Final version! (Apr 04)

Authors: F. Governato (UW, Seattle), L.Mayer (Zurich), J.Wadsley (Mcmaster, CA), J.P.Gardner (U.Pittsburgh), B.Willman (UW) E.Hayashi (U.Victoria, CA), T.Quinn, (UW), J.Stadel (Zurich), G.Lake (WSU)

ApJ in press. Significantly enlarged version.

We simulate the formation of a realistic disk galaxy within the hierarchical scenario of structure formation and study its internal properties to the present epoch. We use a set of smoothed particle hydrodynamic (SPH) simulations with a high dynamical range and force resolution that include cooling, star formation, supernovae (SN) feedback and a redshift dependent UV background. We compare results from a LambdaCDM simulation with a LambdaWDM (2keV) simulation that forms significantly less small scale structure. We show how high mass and force resolution in both the gas and dark matter components play an important role in solving the angular momentum catastrophe claimed from previous simulations of galaxy formation within the hierarchical framework. Hence, a large disk forms without the need of strong energy injection, the z = 0 galaxies lie close to the I--band Tully--Fisher relation, and the stellar material in the disk component has a final specific angular momentum equal to 40% and 90% of that of the dark halo in the LambdaCDM and LambdaWDM models respectively. If rescaled to the Milky Way, the LambdaCDM galaxy has an overabundance of satellites, with a total mass in the stellar halo 40% that in the bulge+disk system. The LambdaWDM galaxy has a drastically reduced satellite population and a negligible stellar spheroidal component. Encounters with satellites play only a minor role in disturbing the disk. Satellites possess a variety of star formation histories linked to mergers and pericentric passages along their orbit around the primary galaxy. In both cosmologies, the galactic halo retains most of the baryons accreted and builds up a hot gas phase with a substantial X--ray emission. Therefore, while we have been successful in creating a realistic stellar disk in a massive galaxy within the LambdaCDM scenario, energy injection emerges as necessary ingredient to reduce the baryon fraction in galactic halos, independent of the cosmology adopted.

The ApJ Paper Get the Postscript file (100kb)

PKDGRAV J. Wadsley, Thomas. Quinn and J. Stadel 2003. Gzipped Postscript file. Submitted to New Astronomy astro-ph/0303521

PKDGRAV J.Stadel PhD Thesis. Chapters on PKDGRAV. Gzipped Postscript file (1.6Mb)

PKDGRAV Stadel, J., J. Wadsley, and D. C. Richardson 2002. High performance computational astrophysics with PKDGRAV & GASOLINE. In High Performance Computing Systems and Applications. (N. J. Dimopoulos and K. F. Lie, Eds.), pp. 501--523. Kluwer Academic Publishers, Boston. Gzipped Postscript file (2.6Mb)

Click on each small stamp to get the movie or a high res image Movies are in Quicktime format. On Linux you need Xanim or Mplayer. With xanim: xanim +j40 file. All movies by Jeff Gardner. Go to his web site. LCDM stars Formation of the stellar component in the LCDM model. The movie is centered on the region were the galaxy forms and shows only the star particles. Young stars are white and get red and then dark blue as they age. Tidal stripping of the satellites originates the halo component. You can see the disk forming at the center. Box is 650kpc (comoving) across. (60Mb)
LCDM stars Age of the disk component in the LCDM model. Box is 40kpc across (40Mb) The movie is centered on the disk that forms in the LCDM run at z=0 and shows only the star particles. As we go backward in time (but we keep positions fixed) stars that just formed are white and get red and then dark blue as they age. You can distinguish the young thin disk and the older thick disk. The oldest stars are in the bulge and in the dwarf spheroidal that is currently passing close to the disk. Box is 30kpc across.
LCDM disk The disk and bulge components formed in the LCDM cosmology. Box is 40kpc across. The left panel shows stars formed after z=1.5, the right panel those formed before z=6.
rotation The rotation curve of the simulated galaxy.
Talk Plot A combined ps file.

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To Fabio Governato web page.
To The N-body Shop web page.
To the Local Group web page.
To the Rainforest Site.