xiaohu yang ( 杨小虎 )
DESCRIPTION
The halo model & galaxy formation. Xiaohu Yang ( 杨小虎 ). Shanghai Astronomical Observatory Partner group of MPA. Collaborators: H.J. Mo (UMass), F.C. van den Bosch (MPIA), A. Pasquali (MPiA), S. Weinmann (MPA), etc. Dark matter. Galaxies. Connecting Galaxies with dark matter halos. - PowerPoint PPT PresentationTRANSCRIPT
Xiaohu Yang (杨小虎 )
Shanghai Astronomical Observatory
Partner group of MPA
Collaborators: H.J. Mo (UMass), F.C. van den Bosch (MPIA), A. Pasquali (MPiA), S. Weinmann (MPA), etc.
Connecting Galaxies with dark matter halos
Galaxies are formed in dark matter halos How many galaxies are formed per halo? What luminosity does each galaxy have? Color? What is their spatial distribution?
GalaxiesDark matter
Outline
What is HOD/CLF?
Can we directly measure the HOD/CLF?
Can we model the evolution of the satellite galaxies? To probe the fate of the disrupted satellite galaxies
An novel scheme: HOD
Jing et al. 1998
Original HOD model:
One step further:
HOD for galaxies of different luminosities: P(N|M)
Conditional Luminosity Function: P(L|M)
Yang et al. 2003; van den Bosch et al.2003
(1) Better match/model observation / Put constraints on the galaxy formation
Progresses in HOD/CLF models
Probe the connection between galaxies and HOST halos The halo Occupations
e.g. Jing, Mo & Borner 1998; Berlind & Weinberg 2002; Zheng et al. 2005; 2008… The Conditional Luminosity Function
e.g. Yang et al. 2003; van den Bosch et al. 2003; 2007; Cooray 2006… The non-parametric CLF
e.g. Vale & Ostriker 2004; 2006; Conroy et al. 2006… Model the central and satellite galaxies separately
Log-normal distribution model for the central galaxies Yang et al. 2003; 2008; Zheng et al. 2006; Cooray 2006; van den Bosch et al. 2007
Power law or (modified) Schetchter form CLF for satellite galaxies Berlind & Weinberg 2002; Yang et al. 2003; van den Bosch et al. 2003
GalaxiesDark matter
Part II: Direct measurement?
The HOD/CLF model Need to assume a functional form Constrained using the observational data
Do we have direct measure of these functions? Yes! If the galaxies can be grouped according to their common halos…
Galaxy groups in the SDSS DR4 (Yang et al. 2007)Sky coverage: 4514 deg^2
Galaxies with redshifts: 369447 (408119)
Groups selected: 301237 (300049)
Galaxies are grouped according to their common halos Halo mass is assigned for each group The most massive galaxy is defined as the central galaxy
Part III: Model the satellite evolution Satellite galaxies are connected with subhalos
Before their accretion into host halos, they are central galaxies They may have different evolution process after their accretion into the
host halos Probe the evolution of the satellite galaxies
The original stellar mass? The survived stellar mass?
What we have? Observation: CSMF for satellite galaxies (survived) Observation: the central – host halo relation Theory: the models of the subhalo population (SHMF)
Assumption : If the subhalo at the time of its accretion into host halo and the host halo
have the same central – host halo relation, we can predict the original CSMF for satellite galaxies
Used in recent models: Vale & Ostriker 2006; Conroy et al. 2006; 2007;
2008; Cooray 2005
Predict the original satellite galaxy population
What we have? Observation: CSMF for satellite galaxies (survived) Observation: the central – host halo relation Theory: the models of the subhalo population (SHMF)
Assumption : If the subhalo and the host halo have the same central – host
halo relation, we can predict the original CSMF for satellite galaxies
Predictions…
The fate of the disrupted satellite galaxies:
Case 1: merged to the central galaxies Case 2: remain scattered as intra-cluster (group) stars Case 3: in-between
Case 1 ruled out
Star formation in small
halos
Star formation quench
limit
The fraction of stellar mass associated with central galaxy
ICS observational proof
Our prediction of about 8
Gonzalez et al. 2005; 2007; ~ 90% light associated with central galaxies is in the ICS
A factor of 10 more light in ICS than in the central galaxy
Various observational proofs of ICS.
Main results
Observational constraints: The satellite galaxies in more massive subhalos are disrupted at a
higher fraction Star formation in the central galaxy is necessary to halos of mass
>10^{12.4}M_{sun} Not all the stars in the disrupted satellite galaxies are merged to
the central galaxy, especially in clusters. The large amount ICS observed by Gonzalez et al. is predicted in
our model . Impacts:
The galaxy formation models The amount of AGN feedback
Yang et al. 2008 b