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Future Prospects for Sunyaev-Zeldovich Effect Studies

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Future Prospects for Sunyaev-Zeldovich Effect Studies Powered By Docstoc
					                Cosmology
                                with
       Cluster Surveys

                    Subha Majumdar

   Canadian Institute of Theoretical Astrophysics
                      Toronto


           along with Joe Mohr, Martin White & Jose Diego


International Conference on Gravitation and Cosmology, Kochi, 5th January 2004
   Overview
              Introduction to Galaxy Clusters
              Introduction to the Surveys
              Studying Dark Energy with Galaxy Cluster Surveys,
               the stress in on the eqn. of state “w” of dark energy

                 (This was the parameter that was not constrained by WMAP+SDSS!
                 But knowledge of “w” is fundamental to our understanding of dark
               energy)

              Something new: Self Calibration in cluster surveys
               and precision cosmology




Jan 2004                                ICGC – 04, Kochi
What Are Galaxy Clusters?
Galaxy clusters are the most                        HST
                                                      Chandra Image of Zw3158
   massive, collapsed structures in
   the universe. They contain
   galaxies, hot, ionized gas (107-8K)
   and dark matter.

In typical structure formation
    scenarios, low mass clusters
    emerge in significant numbers at
    z~2-3
                                                                    SZE
Clusters are good probes, because                     X-ray

    they are massive and “easy” to
    detect through their:
  • X-ray emission
 • Sunyaev-Zel’dovich Effect
 • Gravitational lensing

Jan 2004                         ICGC – 04, Kochi
The Basics of SZ Effect




   distortion  freq _ dependence amplitude(cluster)
   amplitude            gas _ pressure
                 line  of  sight


Jan 2004                              ICGC – 04, Kochi
Whats nice about SZE?
      1) Ofcourse, the distinct spectral signature
      2) Measures the total thermal content of the cluster
      3) More or less redshift independent
      4) Less susceptible to messy cluster substructure, core
         physics (prop to density and not density squared as in XRays)




Jan 2004                    ICGC – 04, Kochi
   Example: Local Abundance/Mass Function
                             Reiprich & Boehringer 2001




 Look at the large error bars!! We want to do much better.

            Things will change drastically with future surveys.
           Especially as a probe of dark energy eqn `of state “w”

Jan 2004                           ICGC – 04, Kochi
  Upcoming Cluster Surveys
 SZ-surveys:
  Planck    :    2008(?)       7,000/8,000 – 30,000/40,000
  SPT       :    2005(?)       20,000-30,000
  ACT        :   late 2004     few thousands
  APEX      :    middle 2004   few thousands

X-Ray surveys

DUET   : Unsuccesful                        20,000-30,000
DUO    : very +ve report, late 2004         ~10,000
XMM-LSS : 2004+ ,                           ~1000(?)

      Cluster surveys will be a thrust area for some time to come!
Jan 2004                    ICGC – 04, Kochi
From observations to detecting clusters:
                           an example




Diego & SM 04



Jan 2004         ICGC – 04, Kochi
    The Cluster Redshift Distribution

           One can get dN/dz if we can get the redshifts of the detected clusters


     Cluster redshift distribution probes:
             1) volume-redshift relation
             2) abundance evolution
             3) cluster structure and evolution.          Mass Selection Function


           dN(z) dV
                     nz   c d 2 1 z2  dM f M  dn M , z
                                            
           dzd dz d        H z A
                                            0             dM
                 Volume    Abundance         Volume                  Abundance
                 Element




Jan 2004                               ICGC – 04, Kochi
   Sensitivity of Cluster Redshift Distribution to
   Dark Energy Equation of State

Increasing w keeping E fixed
 hasthe following effects



             It decreases
           volume surveyed

      It decreases growth
     rate of perturbations



                                    Volume effect                   Growth Effect
Jan 2004                     ICGC – 04, Kochi       Fig courtesy Joe Mohr
Potential for different methods to
constrain `w’


                                                     Complimentary
                                                           &
                                                   Highly Competetive




  Levine, Shultz & White 2002

Jan 2004                        ICGC – 04, Kochi
Dual Nature of Galaxy Clusters
      It’s critical- for almost any analysis- to keep in mind that clusters
       are young objects and yet as a population they exhibit striking
       regularity

      Statistical studies of (x-ray flux limited samples of) galaxy
       clusters reveal that more than half exhibit merger signatures.
       There’s lot of substructures.


      Statistical studies of (x-ray flux limited samples of) galaxy
       clusters reveal regularity




                   Existence of simple flux-mass relation

Jan 2004                         ICGC – 04, Kochi
       Self-Calibration in SZ surveys
     Two surveys, the South Pole Telescope                   Assumptions required:
      Survey and the Planck all sky survey                       1.    Hierarchichal structure formation is
      (yielding > 20000 clusters), contain                             correct
      enough information to constrain the                        2.    A mass-X-ray luminosity relation
      interesting cosmological parameters and                          exists (or a mass-SZE luminosity
      solve for the structure of galaxy clusters                       relation exists)
      simultaneously!                                            3.    Crude redshift estimates are
                                                                       available for each cluster detected in
                                                                       the survey

                                   f x z4dL  AM  E 2 z
                                             2


        Survey       m      tot       w         s8       h            n        b       Norm    Slope
        Priors              flat                        0.07          0.050    0.004
        Planck      0.017    -        0.075    0.013    0.053         0.041    0.004     24%      0.004
        SPT
                  0.024    -        0.062    0.013    0.047         0.048    0.004     21%      0.005
                                                                                       SM & J. Mohr 2003


    Jan 2004                                  ICGC – 04, Kochi
Self-Calibration : Continued

A Caveat:       What if there is “evolution” ??
                                                             
                    f x z4 d  AM E z1 z
                                2
                                L
                                                 2



                                     Everything is lost ! Or is it?

     
 Self Calibration can be regained (by adding complimentary info) !
          1. Need to do follow-up mass estimates of a few clusters
          2. Cluster power spectrum, P(k)


       Not impressive by themselves, when combined with dN/dz they do wonders

Jan 2004                            ICGC – 04, Kochi
An Example: Planck All Sky Cluster Survey
                Nclusters ~ 22000




                                    SM & J. Mohr, 2004


Jan 2004         ICGC – 04, Kochi
How well do we get `w’ ?
           1s error around w=-1, normalized over 9 other parameters


Survey         On its          + P(k)              +100       + Both
               own                                 clusters
                                                      follow-
                                                   up
SPT            0.18            0.16                0.06       0.035
Planck         0.39            0.10                0.12          0.041

                       Note: WMAPext gives ~ 0.11
 To pin down dark energy we must have cluster surveys + (CMB+SNe)

Jan 2004                        ICGC – 04, Kochi
So what did I say,
  Upcoming large yield cluster surveys would unveil a new
era of doing cosmology with clusters.
    It has the promise to become 4th pillar of precision cosmology
along with CMB, SNe and weak lensing.

   As an example, we have shown that these surveys provide us an
opportunity to probe the enigma of dark energy with high precision
                       (the other great way is to do weak lensing tomography)


 Most importantly, we’ve seen that even with uncertainties in cluster
physics, `self-calibration’ in these surveys makes clusters an important
tool in precision cosmology           ( “w” to few percents, certainly competetive or maybe
even better than what can be done with CMB or SNe alone. )




Jan 2004                                ICGC – 04, Kochi

				
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posted:8/19/2012
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