Observing the formation and evolution of massive galaxies
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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
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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. 50% mass built. Pozzetti et al. 2010. Physical processes of mass assembly - PowerPoint PPT Presentation
Transcript of Observing the formation and evolution of massive galaxies
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
Crucial test for mass assemblyhistory in ΛCDM cosmology
Cosmological applicationswith passive ellipticals
Pozzetti et al. 2010
50%massbuilt
Early-Type Galaxies (ETGs): solid results at z<1
Nearly constant number density
Oldest, passive, most massive
Downsizing evolution
sSFR
(SFR/M*)
Redshift0 1 2 3 4 5
Schematic Evolution of Massive Galaxies
E/S0 Quiescent/Passive
Post Starburst
Star-forming
AGN
(I)
(II)
(III)
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)
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
Tacconi et al. 2008
Cimatti et al. 2008, VLT+FORS2
• 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
z=2.04 (Toft et al. 2012, VLT+X-shooter)
Phase II and III – From Post-starburst to Passive
1.4<z<2 (Onodera et al. 2012, Subaru+MOIRCS)
HST+ACS
Whitaker et al. 2011
Gobat et al. 2012
z=2.99 HST+WFC3
Cimatti et al. 2008
Photometric candidates
3 < z < 6(?!) 10.8 < log M* < 11.5 M⊙
Ages ~ 0.2 – 0.8 Gyr AV ~ 0 – 1
Dunlop et al. 2006, Brammer et al. 2006, Wiklind et al. 2007, Mancini et al. 2008, Fontana et al. 2009, Marchesini et al. 2010
IRAC 3 -8 μm
Passive galaxies at even higher redshifts ?
K(AB) ~ 22-24 => EELT + JWST !
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
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
I ≈ 24 – 26+K ≈ 20-23+ (AB)
Passive ETGVLT + FORS2~30h integration
- Generally faint targets
- Passive: red continuum, no emission lines
- Optical and NIR spectra needed
- R>5000-10,000: challenging or impossible
z=2.04 (Toft et al. 2012, VLT+X-shooter)
VLT + X-shooter
K ~ 20.2 (AB)J ~ 20.9R~ 23.5B ~ 24.8
K ~ 21.5 (AB)I~ 25
Requirement Why ? Main Science
Spectral Coverage
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”) S/N for small targets
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
Example of JHK spectrum Submm-selected starburst galaxy at z=2.56VLT+SPIFFIK ~20 (AB)
Tecza et al. 2004
Compact quiescent galaxy at z=1.8
Example of optical + JHK spectrum
VLT+ X-shootervan de Sande et al. 2011
Wide spectral range needed
Example of optical spectroscopy of star-forming galaxies at z≈ 2
GMASS; Halliday et al. 2008
VLT + FORS2 + grism 300V
equivalent to 800 hours integration !
Intermediate spectral resolution needed
Protocluster at z = 2.07 (Gobat et al. 2011)
Kurk et al. 2009passive ETG triplet in aprotocluster at z=1.61
Examples of MOS benefits (I)Overdensity around radio galaxy at z = 2.2 (Miley et al. 2006)
21”
1.4’
Examples of MOS benefits (II)
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 ?
Giavalisco et al. 2011
15”
GMASS
Conclusions
VLT
EELT+HIRES
• Key and broad science case• Wide range of galaxy properties• => Multi-purpose instrument
R ~ 10,000 (1000?)Simultaneous Optical + YJHKMOSModerate AO + slit
