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Modeling galaxy clustering and weak gravitational lensing with the Millennium simulation

Modeling galaxy clustering and weak gravitational lensing with the Millennium simulation. Eyal Neistein TMoX group, MPE Garching Collaborators: Mike Boylan-Kolchin , Sadegh Khochfar , Cheng Li, Francesco Shankar, Simone Weinmann. Halo occupation distribution (HOD) models.

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Modeling galaxy clustering and weak gravitational lensing with the Millennium simulation

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  1. Modeling galaxy clustering and weak gravitational lensing with the Millennium simulation EyalNeistein TMoX group, MPE Garching Collaborators: Mike Boylan-Kolchin, SadeghKhochfar, Cheng Li, Francesco Shankar, Simone Weinmann

  2. Halo occupation distribution (HOD) models • No evolution with time, deal with only one redshift • Populate N galaxies inside each halo of mass M • A specific population of galaxies (usually more massive than Mmin) • Halo properties (density profile, clustering) are being used to compute galaxy properties

  3. HOD principles Model assumptions: • Number of galaxies per halo, P(N|M) • Location of satellite galaxies within their host halo follows NFW. Zehavi et al (2010) • Main features: • Analytic model, self-contained • A simple set of parameters • A priori functional shapes • Not fully accurate (e.g., the assembly bias, Gao et al. 2005) Jing, Mo, & Borner (1998); Ma & Fry (2000); Peacock & Smith (2000); Seljak (2000); Scoccimarro et al. (2001); Berlind & Weinberg (2002); Cooray & Sheth (2002); Yang, Mo, & van den Bosch (2003); Kravtsov et al. (2004); Tinker et al (2005,2011); Zheng et al. (2005, 2007); Zehavi et al (2005,2010)…

  4. SAM The HASH* approach 1. Assign a stellar mass to each subhalo from the Millennium simulation (Minfall) 2. Allow a different stellar mass for central and satellite galaxies 3. The stellar mass of satellite galaxies depends on both Minfall and M200: constant stellar mass - Dynamical friction for galaxies (once subhalo are stripped below the resolution) - Location of satellite galaxies (according to the most-bound particle, or analytic model) * halo and subhalo Neistein et al (2011a, 2011b)

  5. Satellites: Parameter-free approach The observed CFs: different bins of stellar mass Centrals: • do not assume a functional form • check all possibilities Stellar mass Minfall

  6. Searching all solutions • ~107subhalos within the Millennium simulation • ~1014 number of pairs • ~1010 models to test • ~1024 computer operations => Hubble time? Correlation function: we compute the number of subhalo pairs : central-central pairs with subhalo masses M1infall, M2infall , : satellite-satellite, central-satellite Weak gravitational lensing: we compute the projected density profile around each subhalo, and average it:

  7. Models that fit the CF & SMF Satellites only: median 1-std full range Neistein et al (2011b)

  8. Results, weak lensing Centrals (uniform errors) Satellites (uniform errors) Centrals, 95% level Centrals, Mandelbaum et al. (2006), HOD Reference line

  9. All constraints together • Weak lensing does not contribute • Freedom for massive satellites • Future weak lensing measurements

  10. Comparison to HODs

  11. Thank you, the Millennium team! • Summary • We develop a new approach (HASH) • - stellar mass (for satellites) depends on both halo & subhalo • - freedom in satellite locations • - dynamical friction with a free scaling constant • >> more freedom in the models • >> higher accuracy • >> (almost) parameter free • The relation between dark-matter & galaxies • weak lensing does not add much for massive galaxies • systematics are still important (assembly bias)

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