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Clustering and environments of dark matter halos

Clustering and environments of dark matter halos. Yipeng Jing Shanghai Astronomical Observatory. Evolution of large scale structures.

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Clustering and environments of dark matter halos

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  1. Clustering and environments of dark matter halos Yipeng Jing Shanghai Astronomical Observatory

  2. Evolution of large scale structures The importance of studying dark matter halos: 1)in CDM models, all dark matter is in halos of different mass; 2) shaping up luminous objects, such galaxies and clusters; 3) dark matter halos could be directly detected by gravitational lensing

  3. Three important aspects of dark matter halos • Mean number: mass function f(m)dm; • Spatial distribution: correlation functions; bias factors, etc. • Internal properties of dark matter: density profile, spin,etc

  4. Excursion Set Theory for “identifying” dark matter halos from Gaussian Initial density field Bond et al. 1991, ApJ

  5. ( ) F f & h h d l M P S B i 1 9 7 1 1 9 9 1 t t t a s s u n c o n r e s s c e c e r ; o n e a . r 2 ¯ ¯ µ ¶ ( ) d l M 2 ½ n ¾ º 0 ¯ ¯ ( ) ( ) d d M M M 1 ¡ n º e x p = ¯ ¯ 2 d l M M 2 n ¼ ¯ ¯ = ( ) h ± d ± W M 1 6 8 e r e º ¾ a n = = c c : . ( ) F f & h B L M W i i i 1 9 9 6 t t a s a c o r n e a r ; o e 2 1 ¡ º ( ) ( ) B M 1 2 + = ± c ( ) F h l h l f h l h d T i i i i i t t t e n e r n a p y s c a p r o p e r e s o a o s s p n s a p e a g e e c a r e n e - , , . ( ) d f d l h B W i i 1 9 9 1 1 9 9 6 t t t t p e n e n o e n v r o n m e n o n e a ; e . Predictions of the Excursion Set Theory

  6. Test of the Excursion theory :mass function Lee & Shandarin 1998, ApJ

  7. Jing et al. 2006 in preparation 暗晕的质量函数也能很好地与模拟数据符合（Based on the background-split assumption and the bias model）

  8. Test of the bias (Jing 1998, ApJL)

  9. Empirical Modification for MF and bias (based on peak background split) • Sheth & Tormen (1999) MNRAS

  10. Environmental effect • Lemson & Kauffmann (1999): spin, concentration, no dependence; • Percival et al. (2003): clustering vs age, no dependence; • Gao et al. (2005), MNRAS, found age dependence • Main Reason: Gao et al examine M<<M* halos Formation time: at the time when the most massive pregenitor has accumulated a half mass

  11. Concentration vs formation time Jing (2000) ApJ; see also Bullock et al. (2001), Wechsler et al. (2002), Zhao et al (2003a,b)

  12. Clustering vs concentration Wechsler et al. 2006/astroph0512416 • Small halos: agree with Gao et al. • Big halos: reversed • Small and big halos Not at the same epoch

  13. Reversal not found for formation time ?? Wetzel, et al. 2006 Astroph/0606699 For massive halos: confirmed the dependence on c; but not found for the formation time

  14. ( ) h ( ) ( ) i k ± k ± k P c m c m ( ) b 1 = = ( ) h ( ) ( ) i k ± k ± k P m m m m An accurate determination at high halo mass Jing, Suto, Mo 2006, to be submitted A set of N-body simulations of 1 billion particles Using cross-power spectrum method Superior over the correlation function method

  15. Cosmological N-body simulations at SHAO with 10243 particles

  16. The dependence on the formation time is detected at >10sigma for large halos, though small !

  17. Why old, low mass halos are more strongly clustered? Wang, Mo, Jing (2006), astroph/0608690 (MN in press)

  18. Association with high initial collapse region (SC) leads to high clustering of old population

  19. Tidal stripping/pancake heating suppress formation of low mass halos in high density regions (cf. Mo et al 2005 MN, Lee 2006 astroph/0605697)

  20. Observational Evidence? Using 2dF catalogs of galaxies and groups, and the cross correlation Using η (current SFR)of the central as the proxy for z_f Yang et al. (2005) ApJL

  21. Consequences for Halo Occupation Distribution Studies (Zhu et al. 2006, ApJL)

  22. Limitation for precision measurement with HOD Croton et al. 2006 Astroph/0605636

  23. Summary • The dependences of halo clustering on both formation time and the concentration are well established; • The dependence at low mass is largely due to the failure of the spherical model; providing clues to improve EST; • The dependences at high mass still are challenging to Excursion Set Theory • Preliminary observational evidence, but not fully consistent; • Important for precision cosmology studies with HOD: color dependence

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