Observing the formation and evolution of massive galaxies

1. Observing the formation and evolution of massive galaxies Andrea Cimatti University of Bologna – Department of Astronomy “Towards the science case for E-ELT HIRES” – IoA, Cambridge, 13-14 September 2012

2. 50% mass built Pozzetti et al. 2010 Physical processes of mass assembly Crucial test for mass assembly history in ΛCDM cosmology Cosmological applications with passive ellipticals Why ?

3. Early-Type Galaxies (ETGs): solid results at z<1 Oldest, passive, most massive Downsizing evolution Nearly constant number density

4. Schematic Evolution of Massive Galaxies sSFR (SFR/M*) Star-forming (I) AGN Post Starburst (II) Quiescent /Passive E/S0 (III) 0 1 2 3 4 5 Redshift

5. Phase I – The star-forming precursors at z ≥ 2 ? Daddi et al. 2004 Halliday et al. 2008 Tecza et al. 2004 Shapiro et al. 2009 • Dusty EROs, sBzK, DRGs, SMGs, ULIRGs… • SFR up to ~ 200+ Msun/yr • SFR – M* correlation • M* up to ~ 1011 Msun • High sSFR • Nearly solar gas metallicity for most massive ones • Massive disks or mergers • M(cold gas) ~ 1010-11 Msun (from CO) • Higher gas fraction than at z=0 • M(dust) ~ 108-9 Msun • SMGs : compact and dense (size : 1-2 kpc) • Fraction of AGN increases with mass • Strongly clustered (r0 ~ 8-11 h-1 Mpc) Tacconi et al. 2008

6. Phase II and III – From Post-starburst to Passive HST+ACS Cimatti et al. 2008, VLT+FORS2 z=2.99 HST+WFC3 z=2.04 (Toft et al. 2012, VLT+X-shooter) 1.4<z<2 (Onodera et al. 2012, Subaru+MOIRCS) Gobat et al. 2012 • z(spec)max~ 3 • Low sSFR to passive • Ages >1- 3 Gyr, Z ≈ ZSun ? • zform>2–4 • τ ≈ 0.1 – 0.3 Gyr • M* up to ~1011.5 M⊙ • 3x smaller (10x denser) than @z~0 Cimatti et al. 2008 Whitaker et al. 2011

7. z J H K 3.6 μm 4.5μm 5.8μm 8.0μm 24μm Passive galaxies at even higher redshifts ? dusty passive? Rodighiero et al. 2007 Dominguez-Sanchez et al. 2011 Photometriccandidates • 3 < z < 6(?!) • 10.8 < log M* < 11.5 M⊙ • Ages ~ 0.2 – 0.8 Gyr • AV ~ 0 – 1 IRAC 3 -8 μm K(AB) ~ 22-24 => EELT + JWST ! Dunlop et al. 2006, Brammer et al. 2006, Wiklind et al. 2007, Mancini et al. 2008, Fontana et al. 2009, Marchesini et al. 2010

8. Main Open Questions • Precursors ? • Formation mechanism(s) ? • Size Growth ? • Mass growth ? • Mode(s) and suppression of star formation ? • Role of AGN ? • Fit into ΛCDM scenario of structure formation ?

9. I ≈ 24 – 26+ K ≈ 20-23+ (AB) Passive ETG VLT + FORS2 ~30h integration z=2.04 (Toft et al. 2012, VLT+X-shooter) Current limitations - Generallyfaint targets - Passive: red continuum, no emission lines - Optical and NIR spectra needed - R>5000-10,000: challenging or impossible K ~ 21.5 (AB) I~ 25 VLT + X-shooter K ~ 20.2 (AB) J ~ 20.9 R~ 23.5 B ~ 24.8

11. Submm-selected starburst galaxy at z=2.56 VLT+SPIFFI K ~20 (AB) Example of JHK spectrum Wide spectral range needed Tecza et al. 2004 Example of optical + JHK spectrum Compact quiescent galaxy at z=1.8 VLT+ X-shooter van de Sande et al. 2011

12. Example of optical spectroscopy of star-forming galaxies at z≈ 2 VLT + FORS2 + grism 300V equivalent to800 hoursintegration ! Intermediate spectral resolution needed GMASS; Halliday et al. 2008

13. Kurk et al. 2009 passive ETG triplet in a protocluster at z=1.61 Overdensity around radio galaxy at z = 2.2 (Miley et al. 2006) Protocluster at z = 2.07 (Gobat et al. 2011) Examples of MOS benefits (I) 1.4’ 21”

14. Examples of MOS benefits (II) Giavalisco et al. 2011 15” Cold (T~104 K), chemically young gas seen in absorption in an overdensity of galaxies at z=1.6 using spectra of background LBGs at z>3 The gas does not belong to galaxies,but it is diffuse Large scale infall motion ? Accretion of cold gas onto galaxies ? Feeding star formation ? GMASS

15. Conclusions • Key and broad science case • Wide range of galaxy properties • => Multi-purpose instrument VLT EELT+HIRES R ~ 10,000 (1000?) Simultaneous Optical + YJHK MOS Moderate AO + slit