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The STAGES Supercluster: A challenge for semi-analytical models?

Rhys Rhodes The University of Nottingham 25 th June 2008 Meghan Gray and Frazer Pearce. The STAGES Supercluster: A challenge for semi-analytical models?. The STAGES field. Multiwavelength survey of the complex Abell 901/902 supercluster (4 clusters?)

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The STAGES Supercluster: A challenge for semi-analytical models?

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  1. Rhys Rhodes The University of Nottingham 25th June 2008 Meghan Gray and Frazer Pearce The STAGES Supercluster: A challenge for semi-analytical models?

  2. The STAGES field • Multiwavelength survey of the complex Abell 901/902 supercluster (4 clusters?) • Aim to explore the environmental drivers of galaxy evolution • Hubble imaging, ground based 17-band imaging (photo-z), XMM • Weak lensing from HST data reveals DM distribution

  3. A901a A901b A902 SW group Image: Heymans et al 2008

  4. galaxy luminosity density galaxy number density Is this a challenge? mass map

  5. Is this a challenge? Croton model Number of galaxies Mass of cluster M200

  6. A more direct comparison • Count galaxies down a fixed width column of 450 h-1 Kpc for every cluster in the simulation • Introduce a magnitude cut of Mv < -17

  7. Is this a challenge?: Not as we thought ?

  8. A902? • A901a/b difference in Ngal is reproduced in models • A902 has ~twice the maximum number of galaxies predicted for its mass • These columns are only cut through the galaxies within the DM halos of the clusters • A902 also has two BGCs and two DM mass peaks

  9. Another look at A902

  10. A pair of clusters • Two clusters in projection would give a combined lensing mass • From previous plot two halos of half the mass would have ~correct Ngal • Searched through halo catalogue for pairs of halos with combined mass of A902 • Cut columns through depth of both halo centres out to +/- 2Mpc with 450kpc radius

  11. Paired Clusters

  12. Paired Clusters

  13. Thinner Cut

  14. Histograms

  15. 3D Distributions 4 Mpc Separation

  16. Conclusions • A901a/A901b galaxy count difference reproduced • Models suggest A902 may be a pair of clusters along the line of sight • So far the STAGES field has produced nothing which causes problems for the millennium galaxy models (sorry) • However by comparing observations of our field with simulations we may have learned something about its structure

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