Cosmology and Galaxy Evolution from Galaxy Clustering

Zheng ZhengZheng Zheng

Institute for Advanced StudyInstitute for Advanced Study

Cosmology and Galaxy Evolution from Galaxy

Clustering

Halo Occupation Distribution (HOD)Halo Occupation Distribution (HOD)

Breaking the Degeneracies between Breaking the Degeneracies between Cosmology and Galaxy BiasCosmology and Galaxy Bias

With David Weinberg (Ohio State University)

(Zheng & Weinberg, astro-ph/0512071)

Evolution of Galaxies from HOD Modeling of Evolution of Galaxies from HOD Modeling of DEEP2 and SDSS Galaxy ClusteringDEEP2 and SDSS Galaxy Clustering

With

Alison Coil (University of Arizona)

Idit Zehavi (Case Western Reserve University)

Outline:

Galaxies from SDSS

Snapshot @ z~0Light-Mass relation not well

understood

Snapshot @ z~1100Light-Mass relation well

understood

CMB from WMAP

Cosmological Modelinitial conditions

energy & matter contents

Galaxy Formation Physicsgas dynamics, cooling

star formation, feedback

m 8 ns

Dark Halo Population n(M)

(r|M) v(r|M)

Halo Occupation Distribution P(N|M)

spatial bias within halosvelocity bias within halos

Galaxy ClusteringGalaxy-Mass Correlations

Halo Occupation Distribution (HOD)Halo Occupation Distribution (HOD)

• P(N|M)P(N|M)

Probability distribution of finding N galaxies in a halo of virial mass MProbability distribution of finding N galaxies in a halo of virial mass M

mean occupation <N(M)>mean occupation <N(M)> + higher moments+ higher moments

• Spatial bias within halosSpatial bias within halos

Difference in the distribution profiles of dark matter and galaxies within Difference in the distribution profiles of dark matter and galaxies within haloshalos

• Velocity bias within halosVelocity bias within halos Difference in the velocities of dark matter and galaxies within halosDifference 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; …





m 8 ns


(r|M) v(r|M)




CosmologyA

Halo PopulationA

HODA


A

CosmologyB

Halo PopulationB

HODB


B

=

Cosmology from Galaxy Clustering?

Halo populations from distinct cosmological models

Zheng, Tinker, Weinberg, &

Berlind 2002

Changing m

with 8, ns, and Fixed

CosmologyA

Halo PopulationA

HODA


A

CosmologyB

Halo PopulationB

HODB


B

=

Flexible HOD parameterization

• P(N|M)

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

Observational quantities

• Spatial Clustering Galaxy overdensity g(r)

Group multiplicity function ngroup(>N)

2-point and 3-point correlation function of galaxies

• Dynamically Sensitive Observables m

0.6/bg

Pairwise velocity dispersion v(r)

Average virial mass of galaxy groups <Mvir(N)>

• Galaxy-mass cross-correlation function

mgm(r)

Constraints on HOD and cosmological parameters

Changing m


Constraints on HOD parameters

Changing m


Constraints on cosmological parameters

Changing m only

Changing 8 only

Cluster-normalized

Halo MF matched

Influence Matrix

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

Abazajian et al. 2005

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.





m 8 ns


(r|M) v(r|M)




Galaxy Evolution from Galaxy Clustering

Galaxy SamplesGalaxy Samples

DEEP2, z~1 (Coil et al 2006)DEEP2, z~1 (Coil et al 2006)

SDSS, z~0 (Zehavi et al 2005)SDSS, z~0 (Zehavi et al 2005)

Measurements of two-point correlation functions Measurements of two-point correlation functions as a function of luminosityas a function of luminosity

Two-point correlation function of galaxies

1-halo term

2-halo term

Excess probability w.r.t. random distribution of finding galaxy pairs at a given separation

Central

Satellite

Halo Occupation DistributionHalo Occupation Distribution

For a sample of galaxiesmore luminous than Lmin

Mmin - characteristic minimum mass

of halos hosting Lmin galaxies

M1 - mass of halos on

average hosting one satellite galaxy above Lmin

Scatter between galaxy luminosity and host halo mass

Modeling resultsModeling results

L

DEEP2 galaxies

Distribution of central galaxy luminosityDistribution of central galaxy luminosity

Mass scales of host halosMass scales of host halos

Establishing an evolution link Establishing an evolution link between DEEP2 and SDSS galaxiesbetween DEEP2 and SDSS galaxies

MergingStar

Formation

z~0

z~1

Merging

z~1

z~0

Stellar mass evolution

Star formation efficiency vs Halo massStar formation efficiency vs Halo mass

Stellar mass evolution (z~1 to z~0) Stellar mass evolution (z~1 to z~0) as a function of halo massas a function of halo mass

Merging

z~1

z~0

Star Formation

Tentative conclusion:

For central galaxies in z~0 M<1012 h-1Msun halos,~80% of their stars form after z~1

For central galaxies in z~0 M>1012 h-1Msun halos,~20-40% of their stars form after z~1

Fardal et al. 2006

Summary & Future WorkSummary & Future Work HODs at z~1 and z~0 from modeling two-point correlation functions ofHODs at z~1 and z~0 from modeling two-point correlation functions of DEEP2 and SDSS galaxiesDEEP2 and SDSS galaxies

Evolution link through halo evolutionEvolution link through halo evolution

Stellar mass evolution from z~1 to z~0 for central galaxies as a function Stellar mass evolution from z~1 to z~0 for central galaxies as a function of halo mass (pure merger vs star formation)of halo mass (pure merger vs star formation)

Useful constraints to galaxy formation modelsUseful constraints to galaxy formation models Clustering measurements for galaxy samples based on stellar massClustering measurements for galaxy samples based on stellar mass

Galaxy samples at different redshiftsGalaxy samples at different redshifts

Evolution of satellite galaxiesEvolution of satellite galaxies

Cosmology and Galaxy Evolution from Galaxy Clustering

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