Zheng Zheng

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Cosmology and Galaxy Evolution from Galaxy
Clustering

• Zheng Zheng
• Institute for Advanced Study

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Outline

• Halo Occupation Distribution (HOD)
• Breaking the Degeneracies between Cosmology and
  Galaxy Bias
• With David Weinberg (Ohio State University)
  
• (Zheng Weinberg, astro-ph/0512071)
• Evolution of Galaxies from HOD Modeling of DEEP2
  and SDSS Galaxy Clustering
• With
• Alison Coil (University of Arizona)
• Idit Zehavi (Case Western Reserve
  University)

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Halo Occupation Distribution (HOD)

• P(NM)
• Probability distribution of finding N galaxies
  in a halo of virial mass M
• mean occupation ltN(M)gt higher moments
• Spatial bias within halos
• Difference in the distribution profiles of
  dark matter and galaxies within halos
• Velocity bias within halos
• Difference in the velocities of dark matter
  and galaxies within halos

e.g., Jing Borner 1998 Ma Fry 2000 Peacock
Smith 2000 Seljak 2000 Scoccimarro et al.
2001 Berlind Weinberg 2002 Yang, Mo, van
den Bosch 2003
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Cosmology from Galaxy Clustering?
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Halo populations from distinct cosmological
models
Changing ?m with ?8, ns, and ? Fixed
Zheng, Tinker, Weinberg, Berlind 2002
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?
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Flexible HOD parameterization

• P(NM)
• Motivated by galaxy
• formation models
• Spatial bias within halos
• Different concentrations of galaxy
  distribution
• and dark matter distribution (?c)
• Velocity bias within halos
• vg ?vvm

Kravtsov et al. 2004 Zheng et al. 2005
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Observational quantities

• Spatial Clustering
• Galaxy overdensity ?g(r)
• Group multiplicity function ngroup(gtN)
• 2-point and 3-point correlation function of
  galaxies
• Dynamically Sensitive Observables
• ???m0.6/bg
• Pairwise velocity dispersion ?v(r)
• Average virial mass of galaxy groups
  ltMvir(N)gt
• Galaxy-mass cross-correlation function
• ?m?gm(r)

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Constraints on HOD and cosmological parameters
Changing ?m with ?8, ns, and ? Fixed
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Constraints on HOD parameters
Changing ?m with ?8, ns, and ? Fixed
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Constraints on cosmological parameters
Changing ?m only
Changing ?8 only
Cluster-normalized
Halo MF matched
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Influence Matrix
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Constraints on cosmological parameters
Forecast 10 on ?m 10 on ?8 5
on ?8 ?m0.75 From 30 observables of 8
different statistics with 10 fractional errors
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Conclusion

• Galaxy bias and cosmology are not degenerate with
  
• respect to galaxy clustering.
• HOD modeling can greatly increase the
  cosmological power of
• galaxy redshift survey by taking the
  advantage of high-precision
• clustering measurements at small and
  intermediate scales.
• Simultaneously, using galaxy clustering
  data, we can constrain
• the HODs for different classes of
  galaxies, which provide
• valuable tests of galaxy formation models.
  

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Galaxy Evolution from Galaxy Clustering Galaxy
Samples

• DEEP2, z1 (Coil et al 2006)
• SDSS, z0 (Zehavi et al 2005)
• Measurements of two-point correlation functions
  as a function of luminosity

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Two-point correlation function of galaxies
Excess probability w.r.t. random distribution of
finding galaxy pairs at a given separation
1-halo term
Central
2-halo term
Satellite
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Halo Occupation Distribution
For a sample of galaxies more luminous than Lmin
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Modeling results
DEEP2 galaxies
L
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Distribution of central galaxy luminosity
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Mass scales of host halos
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Establishing an evolution link between DEEP2 and
SDSS galaxies
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Stellar mass evolution
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Star formation efficiency vs Halo mass
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Stellar mass evolution (z1 to z0) as a
function of halo mass
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z1
Star Formation
Merging
z0
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Tentative conclusion For central galaxies in
z0 Mlt1012 h-1Msun halos, 80 of their stars
form after z1 For central galaxies in z0
Mgt1012 h-1Msun halos, 20-40 of their stars form
after z1
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Summary Future Work

• HODs at z1 and z0 from modeling two-point
  correlation functions of
• DEEP2 and SDSS galaxies
• Evolution link through halo evolution
• Stellar mass evolution from z1 to z0 for
  central galaxies as a function of halo mass (pure
  merger vs star formation)
• Useful constraints to galaxy formation models
• Clustering measurements for galaxy samples
  based on stellar mass
• Galaxy samples at different redshifts
• Evolution of satellite galaxies