Dark matter in elliptical galaxies - mapping the isolated elliptical NGC 4555

One of the main difficulties in measuring the dark matter content of ellipticalgalaxies is that the majority are embedded in the dark matter halos of groupsand clusters. NGC 4555 is currently the only truly isolated elliptical known tohave an extensive dark matter halo, and we propose to follow up our previousChandra observation with a deep XMMNewton pointing. We expect to trace the massprofile to virgul130 kpc (5.), allowing determination of parameters such as haloconcentration, total system mass, and baryon fraction, which can be comparedwith the predictions of galaxy simulations. We will also measure the abundanceprofile, providing insight into the enrichment history of this unusual andimportant galaxy. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]