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How do galaxies accrete their mass? Quiescent and star - forming massive galaxies at high z

How do galaxies accrete their mass? Quiescent and star - forming massive galaxies at high z. Paola Santini. Osservatorio Astronomico di Roma. THE ORIGIN OF GALAXIES: LESSONS FROM THE DISTANT UNIVERSE Obergurgl, 12 - 17 December 2009. z ≥ 2 : major phase in the assembly of massive galaxies.

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How do galaxies accrete their mass? Quiescent and star - forming massive galaxies at high z

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  1. How do galaxies accrete their mass?Quiescent and star-forming massive galaxies at high z Paola Santini Osservatorio Astronomico di Roma THE ORIGIN OF GALAXIES: LESSONS FROM THE DISTANT UNIVERSE Obergurgl, 12-17 December 2009

  2. z ≥ 2 : major phase in the assembly of massive galaxies Redshift 1) What drives the evolution of stellar mass at z ~ 2? (SF inside galaxies? Mergers?) 2) Quenching mechanisms? 3) Are these processes reproduced by the models? Searching observables which directly reflect these two processes M>7 1010 Mo Fontana+06

  3. The GOODS-MUSIC sample GreatObservatoriesOriginsDeepSurvey-MUltiwevelengthSouthernInfra-redCatalog (Grazian+06, Santini+09, http://lbc.oa-roma.inaf.it/goods) Photometry from 0.3 to 24 µm (15 bands) ~143 arcmin2CDF-South ~15000 objects z, Ks and 4.5 µm selected ~ 1800 spectroscopic z + well calibrated zphot U35 U38 (MPG/ESO-WFI) U VIMOS (VLT) B V i z (HST-ACS) J H Ks (VLT-ISAAC) 3.6 4.5 5.8 8.0 µm (Spitzer-IRAC) 24 µm (Spitzer-MIPS)

  4. Mid-IR emission of quiescent and active galaxies Dusty star-forming 0.9 µm 2.2 µm 4.5 µm 24 µm F(24μm)/F(K) as SED indicator Passively evolving Empirical UV-to-midIR SEDs (Polletta+07) 0.9 µm 2.2 µm 4.5 µm 24 µm

  5. F(24)/F(K) N (UAB-V)

  6. Quiescent galaxies

  7. The very quiescent tail: Red&Dead galaxies 24 µm undetected galaxies Combined IR emission + SED fitting analysis SFR/M SFR/M < 10-11 yr-1 “RED&DEAD” galaxies M>7 1010 Mo Fontana+09 SFR/M

  8. The cosmic evolution of Red&Dead galaxies Galaxies with very low levels of SFR M>7 1010 Mo Fontana+09 • 15-20% of massive galaxies is already in a very quiescent phase at z~2-3 • Sensitive observable to constrain models: quenching mechanisms K07: Kitzbichler&White07 (Millennium Simulation) M06: Menci+06 F07: MORGANA (Monaco+07) N06: Nagamine+06

  9. Star-forming galaxies

  10. Absorbed UV light Dust emission PAH features Stellar emission 24 μm filter M82 (ISO) SFR estimate SED fitting to the multiwavelength photometry Photometric z SFR(Moyr-1) = 1.8 x 10-10 x Lbol(Kennicutt98) (from Dale&Helou02 templates) where Lbol = (2.2 x LUV + LIR), LUV = 1.5 x L2700Å, uncorrected for extinction (Papovich+07) M(stars) SFR Dust Z

  11. Comparison between SFR estimators 1.5 < z < 2.5 Highly obscured AGN candidates (Fiore+08) 1.0 < z < 1.5 GOODS-South + GOODS-North (by Stefano Berta) 0.6 < z < 1.0 Systematic trend: open issue… (see later) 0.3 < z < 0.6

  12. The Specific SFR — stellar mass relation What drives the evolution of stellar mass at z ~ 2? SFR/M Kitzbichler&White07 (Millennium Simulation) GOODS-S + GOODS-N Total accreted mass = <SFR>active x <∆tactive phase> “Duty cycle” argument: 65% of M > 7 1010 Mo galaxies is actively SF-ing at 1.5<z<2.5, with <SFR>~300Mo/yr assuming that the active fraction is proportional to burst duration, the stellar mass acquired in this epoch is >1011Mo SFR=1000Moyr-1 At z ~ 2 massive galaxies are rapidly forming.The SFR directly observed in massive galaxies is enough to produce the bulk of the observed stellar mass density. Intense star formation processes within massive galaxies prevail over merging events at z ~ 2. 100Moyr-1 10Moyr-1 1Moyr-1 Santini+09

  13. How can future data help us? Herschel

  14. @ z~ 2 L PACS 70, 100, 160mm SPIRE MIPS 24 m 250, 350, 500mm Wavelength (µm) Empirical UV-to-midIR SEDs (Polletta+07)

  15. Systematics in IR templates DH: Dale&Helou02 CE: Chary&Elbaz01

  16. What will Herschel be able to observe? above predicted 5 flux limit at 160m above predicted 5 flux limit at 100m

  17. PACS Evolutionary Probe (Herschel GT program) Rodighiero et al, in preparation

  18. Summary & conclusions 1) The epoch z>~2 is a major phase in the assembly of massive galaxies 2) “Red&Dead” galaxies exist up to z=3 and most likely above: need for efficient feedback/quenching mechanisms of SF at high z 3) At z~2, more than 50% of massive galaxies are experiencing a major peak in their SFRH: during this process they accrete a substantial fraction of their mass (see also Daddi+07) 4) Theoretical models fail in predicting simultaneously the SFR (typically under-predicted) and the quenching of SF 5) Need for a different/new physics? (e.g. cooling flows – Dekel+06,08,09) 6) Waiting for new Herschel data…

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