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

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

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

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

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

Phase II and III – From Post-starburst to Passive Gobat et al. 2012 z=2.99 HST+WFC3 z=2.04 (Toft et al. 2012, VLT+X-shooter) 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 HST+ACS Cimatti et al. 2008 Whitaker et al. 2011 Cimatti et al. 2008, VLT+FORS2 1.4<z<2 (Onodera et al. 2012, Subaru+MOIRCS)

Passive galaxies at even higher redshifts ? z J H K 3.6 μm 4.5μm 5.8μm 8.0μm 24μm dusty passive? Rodighiero et al. 2007 Dominguez-Sanchez et al. 2011 Photometric candidates 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

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 ?

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

Requirement Why ? Main Science Spectral Coverage Spectral Resolution Simultaneous Optical (λmin ~0.35 μm for Lyα at z=2) + YJHK Several science cases Stellar populations, emission line ratios, extinction, metallicity, star formation, SFH, AGN… Spectral Resolution (~1000 ?) – 10,000 R~1000: identification and characterization of faint rare targets from wide-field surveys (e.g. Euclid) Mergers, scaling relations, kinematics, feedback, stellar & ISM absorption lines (e.g. metallicity, cold flows, …) Multiplexing FoV ~ 30”+ (diameter) N ~ 10+ BzK galaxies in the field: sBzK: 0.3-1.5 arcmin-2 to K~21.2-22.7(AB) pBzK: 0.1 arcmin-2 to K~21.2-21.7(AB) Densities up to 10x in densest environments Protoclusters High-density fields around AGNs Galaxy gaseous halos connection with IGM AO Moderate (at most) Galaxy sizes ~0.1” - 1” S/N for small targets Fiber vs Slit Narrow slits (e.g. 0.3”) IFU Desirable Internal properties Kinematics, gradients Sensitivity K(AB)=22, seeing limited, 0.8” seeing, 0.8” slit, point source, R=10,000, R(S/N)=0,4” S/N~10 in 4h (ETC V2.14) K(AB)=24.0 R=1000(0) 4(40)h to reach S/N=5

Wide spectral range needed Example of JHK spectrum 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

Intermediate spectral resolution needed Example of optical spectroscopy of star-forming galaxies at z≈ 2 VLT + FORS2 + grism 300V equivalent to 800 hours integration ! Intermediate spectral resolution needed GMASS; Halliday et al. 2008

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

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

Conclusions EELT+HIRES VLT 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