Semianalytic modelling in the era of wide deep

Semi-analytic modelling in the era of wide, deep and multiwavelenght surveys Gabriella De Lucia Max-Planck Institut für Astrophysik Bologna – May 25, 2006

Outline: Semi-analytic models -- substructures & galaxies -- hybrid models – methods, limits & aims Applications -- the formation history � of elliptical galaxies -- the hierarchical formation of BCGs (with J. Blaizot) -- some other prelimilary results…

Cooling (metallicity, structure, conductivity) Dust (formation, distribution, heating and cooling) Winds (IGM heating, enrichment) Star formation (threshold, efficiency, initial mass function) galaxy formation IGM AGN (BH growth, feedback) Galaxy interactions (morphological transformations, induced star formation) Stellar evolution (spectro-photometric evolution, yields, feedback)

The SAM – the classical models: Extended Press & Schechter “Planting” the merger trees Lacey & Cole (1993) These might provide a not adequate description of the merger rates (Benson et al. , 2005)

The SAM – the hybrid models : CDM Central galaxy CDM Halo galaxy Satellite galaxy Springel (2001) Mathis H. et et al. , 2002 De Lucia et al. , 2004

About 800 million subhaloes The Millennium Simulation (Springel et al. 2005) 64 time slices stored Group catalogues and information about their embedded substructures used to construct merger trees About 20 million galaxies Individual trees are stored separately so that the SAM can be run for each tree sequentially

The SAM – the physics : re-incorporation Croton et al. 2006 - AGN heating Cold Gas Hot Gas cooling star formation feedback recycling Ejected Gas DLG, Kauffmann & White, 2004 Stars

Colour-magnitude Tully-Fisher DLG, Kauffmann & White, 2004 Luminosity function Metallicitymass Gas fractionluminosity

Observational signature of different feedback models #1: DLG, Kauffmann & White, 2004 David, Forman, Jones 1995 ejection fast wind fast ejection slow wind slow

A slow ejection feedback scheme: David, Forman, Jones 1995 (M/L)V 190 – 230 (M/L)B 240 – 290 (M/L) IMLR 0. 015 – 0. 020 M /L DLG, Kauffmann & White, 2004

Ellipicals: an old controversy Toomre & Toomre 1972 Barnes 1992 Visvanathan & Sandage (1977) Kauffmann & Charlot (1998) Bender 1992 Gladders et al. (1998)

Ellipicals: the [ /Fe] problem Thomas et al. did not use a selfconsistent approach SNIa Thomas et al. 2001 Previous SAM work based on extended PS theory Most previous SAM work not in a CDM Universe SNII [ /Fe]V Observations are still plagued by systematic uncertainties (template bias) observation s superwind /Kennicutt Nagashima et al. (2005) Log [ /km s-1] conduction

Ellipticals in a hierarchical model : AGN model for suppression of the cooling-flows (Croton et al. , 2006) Three channels to make bulges: In a ‘minor’ merger the stellar mass of the merged galaxy is transferred to the bulge of the central galaxies + burst of a fraction of the combined cold gas A ‘major’ merger completely destroys the disc of the central galaxy + burst of a fraction of the remaining gas Disk instability (Mo, Mao & White 1998) De Lucia et al. , 2006 1, 031, 049 (810, 486 ) Es with Mstar > 4 x 109 (1 x 1010) Msun 16% Es / 66% Sp / 18 % S 0 (MV < -18) (13%, 67%, 20% Loveday et al. , 1996)

The star formation histories: redshift cluster 10 M 10 clusters ellipticals 1011 M 1212 Mstar 10 = 10 M Msun Mstar = 109 Msun field ellipticals Elliptical galaxies also have a shorter formation timescale! This is “anti-hierarchical”!!! Lookback time (Gyr) De Lucia et al. , 2006

Ellipticals: formation & assembly: Fraction of galaxies 50 % stars formed 50 % stars in a single object 80 % redshift De Lucia et al. , 2006

Comparison with previous work: Kauffmann & Charlot (1998) (1998 most massive ellipticals younger than their less massive counter-parts!

Comparison with previous work: No AGN feedback No cooling cutoff AGN feedback reversal due to a combination of the change in the physical model and in the cosmology Kauffmann & Charlot: Cooling cutoff Vcrit = 350 km/s -- critical matter density -- cutoff 500 km/s

The Brighest Cluster Galaxies : The most luminous and most massive objects in the Universe at the present epoch NGC 4889 - z ~ 0 CL 1232. 5 -1250 z ~ 0. 5

The formation of BCGs: De Lucia & Blaizot, in prep.

The formation of BCGs: 0. 5 Time of last major 50 BCGs selected merger @z=0 “Assembly vs formation” history De Lucia & Blaizot, in prep.

The formation of BCGs: Mass in the main branch Fraction of mass gained through accretion >1010 Msun <1010 Msun Most of the stars of this BCG were not formed in the MB, but were instead accreted over time De Lucia & Blaizot, in prep.

The formation of BCGs: Mass in the main branch quiescent starburst the stars formed in separate entities in a quiescent mode. stars formed during Starbursts contribute only for about 10%. De Lucia & Blaizot, in prep.

The formation of BCGs: “Progenitors” more massive than 1010 Msun De Lucia & Blaizot, in prep.

The formation of BCGs: Burke, Collins & Mann 2000 De Lucia & Blaizot, in prep.

Ellipticals: the evolution of the CM B-V A well defined CM up to z~2 A clear bimodal distribution up to z~2 De Lucia et al. , in preparation V

The evolution of the stellar MF Fontana et al. 2004 Drory et al. 2005 ~ good agreement up to z~2 for massive gxs.

The origin of the colour-magnitude: B-V Gallazzi et al. , 2006 Log [Mstars] De Lucia et al. , in preparation

Tools to observe ideas : Mock 2 d. F 75 x 4 deg 2 BAB < 19. 5 Blaizot et al. 2005: Mo. Ma. F

Tools to observe ideas : Mock SDSS 19 < r < 20 H 18 < r < 19 20 < r < 21 21 < r < 22 D 4000 with Jérémy Blaizot

The colour-magnitude bimodality: o. Tail of blue bright objects o Transition region not well populated o Excess of faint red satellites u-r Quantitatively the CM bimodality is not well reproduced

The D 4000 distribution: Same problems are visible in the distribution of D 4000

Conclusions: Semi-analytic models are a technique for studying galaxy formation - they are not meant to be definitive! The observed down-sizing is not in contradiction with the hierarchical paradigm More massive systems assemble later than their less massive counter-parts (this does not seem to be in contradiction with observational data but more detailed comparisons nedeed here) The ever more detailed picture of our Universe also requires a more complex modelling and the development of new tools for a more straightforward comparison with observational data