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Noise effects on Weak-lensing D erived Mass-concentration Relation of Dark Matter Halos

Tsinghua Large Scale Structure Workshop 2014. Noise effects on Weak-lensing D erived Mass-concentration Relation of Dark Matter Halos. Wei Du & Zuhui Fan 2014. Wei Du. National Astronomical Observatory of China. 2014.10.11. Introduction. Coma cluster ( Abell 1656, z=0.0231).

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Noise effects on Weak-lensing D erived Mass-concentration Relation of Dark Matter Halos

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  1. Tsinghua Large Scale Structure Workshop 2014 Noise effects on Weak-lensing Derived Mass-concentration Relation of Dark Matter Halos Wei Du & Zuhui Fan 2014 Wei Du National Astronomical Observatory of China 2014.10.11

  2. Introduction Coma cluster (Abell1656, z=0.0231) The mosaic combines visible-light data from the SDSS. The 2dF Galaxy Redshift Survey

  3. "While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter." • (from Wiki) Coma cluster (Abell1656, z=0.0231) The mosaic combines visible-light data from the SDSS. Galaxy clusters: 1, contain ~3% stellar component, ~17% gas and ~80% dark matter 2, 3, A diameter from 2 to 5 Mpc

  4. M-c relation NFW. 1996, ApJ, 462, 563 Navarro, Frenk& White, 1996,1997 From Phoenix Project; Gao et al. 2012

  5. Mandelbaum et al. 2008 Also see Huanyuan’s work

  6. Wiesner M.P. et al. 2012 Okabe et al. (2010) α ~ -0.45 α ~ -0.4 WL • Sample variance: narrow mass range, low number of clusters… • Selection effect: more concentrated clusters are more likely to be included in the sample • Physical reasons: baryonic physics, accreting haloes out of equilibrium, ΛCDM? SL+N200 Serenoand Covone, 2013 Oguri et al. 2012 α ~ -0.59 α ~ -0.8 SL+WL SL+WL

  7. Coma cluster observed by CFHT Gavazzi, R., Adami, C. et al. 2009 Israel, H., Erben, T. et al. 2012; 400d survey, MMT telescope

  8. Noise effect on M-c relation A halo with a low/high true mass can be grouped into a high/low weak lensing-derived mass bin. For those halos, their derived concentrations are systematically lower/higher than their underlying true concentrations.

  9. Bayesian method

  10. Bayesian method For a mass- limited sample: Where M_{low} indicates selection effect and n(M_T) is the halo mass functiontaken from Tinker et al. (2008)

  11. For a large observational sample of clusters

  12. small samples with a limited number of clusters Okabe et al. (2010) ; 19 clusters

  13. Monte Carlo simulation --Bayesian method

  14. Preliminary result from CFHTLenS • e.g., W1: • Number of bright (<=20 mag) cluster members >=10  147 K2 clusters • Further select the clusters without masks within 5 arcmin  114 K2 clusters

  15. Preliminary result from CFHTLenS

  16. Summary • In order to derive an unbiased M-c relation, noise effect should be carefully taken into account. • We introduce a Bayesian method, including the effects of noise and selection bias (i.e., low mass limit), which can give the unbiased prediction. Thank you!

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