Galaxies within Dark Matter Halos

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Galaxies within Dark Matter Halos

• Michael Brown (Monash)
• with help from Stuart Wyithe (Melbourne), Martin
  Zwaan (ESO), Martin Meyer (UWA), Martin White
  (Berkeley), Zheng Zheng (AS), Darren Croton
  (Swinburne)

Image stolen from Millennium Run Collaboration
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Why?

• Does star-formation depend on halo mass?
• Virial shocking heating (e.g., Dekel et al).
• AGN feedback (Croton et al.)
• Does SFR/HI vary with location within halos?
• When is gas removed from satellite galaxies?
• When is gas heated in central galaxies?
• What is the role of mergers in galaxy growth?

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SF/HI varies with DM mass Rapid galaxy merging
SF/HI varies with stellar mass Long lived
satellite galaxies
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SF/HI varies with DM mass Rapid galaxy merging
SF/HI varies with stellar mass Long lived
satellite galaxies
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How

• DM halo clustering is a known function of DM halo
  mass.
• Model galaxy 2-pt correlation function using
  models of how galaxies populate DM halos.
• Halo Occupation Distribution (HOD) modelling.
• Conditional Luminosity Function (CLF) modelling.
• Clustering at gt1 Mpc a function of DM mass.
• Clustering at lt1 Mpc varies with the number of
  satellite galaxies.

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HIPASS

• Wyithe, Brown, Zwaan Meyer (in preparation).
• Small fingers-of-god imply high halo mass cutoff.
• Small fraction of satellite galaxies.

Redshift space clustering
Excess galaxy pairs c/w random distribution
Redshift
Projected Distance (Mpc/h)
Projected Distance (Mpc/h)
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Summary

• Understanding how galaxies populate DM halos
  tells us much about galaxy formation
• Mode of growth (mergers, star formation).
• Regulating star formation (AGN, virial shock)
• Stripping and heating of cold gas.
• Galaxy clustering constrains models of how
  galaxies populate DM halos.