Formation and evolution of dusty ellipticals Laura Silva (INAF, Trieste, Italy) Gian Luigi Granato (INAF, Padova, Italy) Gianfranco De Zotti (INAF, Padova, Italy) Luigi Danese (SISSA, Trieste, Italy) In collaboration with:

STARTING POINT Difficulty of simulations of galaxy formation in cosmological context: crucial simplifications are required to describe sub-grid physics (SF, SN feedback…). Different treatments can lead to very different predictions for the properties of the galaxy population. As a consequence many successes but several problems as well, in particular connected with properties of (large) E galaxies (e.g. Peebles )

Summary of problems in SA models 1.Large E pop probably already in place at z (Im et al. 2001, Cohen 2001) 2.Not enough objects at z=0 with SED resembling E 3.The statistic of sub-mm selected high z galaxies 4.The color-magnitude and/or the [  /Fe]-M of E relations (Cole et al 2002, Thomas 1999, Thomas et al 2002, but see Kauffmann & Charlot 1998 for CM) These evidences are more consistent with a view in which (stars in) large E are old and almost coeval

Present day semi-analytical models match many observations, including IR (Granato et al 2000), but are challenged by counts and z-distrib. of sub-mm selected sources. Too many small SF events  a major revision of prescriptions used to approximate evolution of baryons seems required

Suggestion: simulations ignore mutual feed-back between formation of E and high-z QSO activity, suggested by observations: 1.Local spheroids contain a central MDO (SMBH), with M = M BH  M sph with scatter and M BH   c 4-5, tighter (e.g. Merritt & Ferrarese 2000, Gehardt et al 2001) 3.Spheroidal galaxies are the most common hosts of high-z QSOs (McLure et al, Dunlop et al ) 4.QSOs are associated to high metallicity, dusty environments (eg Hamann & Ferland 1999; Andreani, Franceschini & Granato, 1999) In particular QSO may mark (cause?) the end of major episode of SF in spheroids.

 Anti-hierarchical baryonic collapse scenario Granato, Silva, et al 2001, MNRAS Feed-back (SN + AGN) delay SF in smaller halos; Large E form their stars as soon as their potential wells are in place  rapid chemical and dust enrichment  high-z sub-mm bright phase; BH and L(QSO) grow, possibly contributing to stop the SF and expulsion of residual gas (0.5 to 2 Gyr); QSO phase follows, ( yrs) then (almost) passive evolution. Rapid reddening of colors (EROs). Intermediate and small sferoids shows up as LBGs.

Test against sub-mm counts (Granato et al 2001, MNRAS) 1.“formation” rate of spheroids 2.SF duration (and time dependence) 3.SED evolution (GRASIL Silva, Granato, Bressan & Danese et al 1998)  Luminosity functions, number counts, redshift distribution

1 - FORMATION RATE of spheroids Two possible paths lead to equivalent results: 1) “end of formation” rate from evolution of QSO LF (QSOs as clocks of SF) 2) “beginning of formation” rate from PS or ST mass function of halos (Sasaki 94, Blain & Longair 93)

2- SFR(t,M) before QSOs shine computed taking into account collapse, heating, cooling and feedback in DM halos Granato et al 2001 T burst (M sph )

short timescales for star-formation, decreasing with increasing mass, are suggested by Chemical abundances (  /Fe) in local ellipticals; The statistic of QSOs in the PS formalism (Monaco, Salucci & Danese 2000) Parametrization:

3 - SED evolution is computed with GRASIL. Prediction for FIR-sub-mm is robust T burst =2 GyrT burst =0.5 Gyr Granato et al 2001

ABC scenario reproduces in a natural way sub-mm statistic (and chemistry of Ellipticals) Granato et al 2001 SCUBA 850  m MAMBO 1200  m

Various aspects and predictions in: Monaco, Salucci & Danese, 2000, MNRAS (statistic of QSOs and E in hierarchical clustering) Granato, Silva, Monaco et al, 2001, MNRAS (sub-mm statistic and E chemistry) Magliocchetti, Moscardini et al, 2001, MNRAS + Perrotta, Magliocchetti et al, 2002, astro-ph (clustering of SCUBA gal., LBG and EROs + effect of strong lensing + fluctuations in planck channels) Romano, Silva, Matteucci & Danese, 2002, MNRAS (more details on chemistry of local E)

S>30  Jy (GOODS) S>450  Jy (SWIRE) z SWIRE (70 sq deg): N Ell  (  20% tot) SIRTF: predictions GOODS (0.1 sq deg): N Ell  1500 (  60% tot) In both surveys star forming Ellipticals show up at 24  m

SWIRE  30  Jy GOODS  2  Jy IRAC BANDS (  m) dominated by passively evolving Ellipticals