Stellar Halo Studies

Johnston & Bullock
Bullock & Johnston
Robertson et al.
Font et al.

If the favored hierarchical cosmological model, LCDM, is correct, then the Milky Way and similarly sized galaxies should have accreted and subsequently tidally destroyed ~200 low-mass galaxies in the past ~12 Gyr. Kathryn Johnston and I are modelling this process using a hybrid semi-analytic plus N-body approach.  Below are a few images from our simulations.

External  Images
300 kpc x 300 kpc boxes.
By row, colors map:
Surface brightness, Fe/H, alpha/Fe, velocity dispersion, line-of-sight velocity

External Surface Brightness Images
Shown is the halo on the far right above, now cut at various surface brightness limits.
From left to right, black= 40, 35, 32, 30, and 28 Magnitudes per square arcsecond.
Click on an image for a larger version.

Phase diagrams: radial velocity vs. radius for entire halos.  Each figure mathes halos with the image above.
Each point represents 1000 solar luminosities in V.
Colors indicate the lookback time when each star was unbound from its satellite: 13.5Gyr = dark blue, 0Gyr = white
Click on image for larger picture.

Vr vs r phase diagram
Vr vs r phase space map
Vr vs r phase space
Vr vs r phase space
radial phase space diagram

Phase diagrams for 4 quarters of the sky for first halo on the left, above.

1 quarter sky
quarter sky
quarter sky
quarter sky

From Font et al. 2006 (astro-ph/0512611):
Metallicity Maps
: Chemical Abundance maps in 8 simulated halos.  Color code in [Fe/H] (left sub-panesl) and [alpha/Fe] (right sub-panels).  Each pixel is 0.25kpc on a side through 300kpc deep.  Boxes are 300kpc on a side.

stellar halo metallicity map

V-band surface brightness maps: Left sub-panels show the surface brightness map of all stars and right sub-panel shows surface brightness for only stars with [alpha/Fe]<0.25.  Each panel is 300 kpc on a side.  (Font et al. 2006).

sb map