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Summary Talk

Summary Talk. Andrea Ferrara 4C - Center for Computational Chemistry and Cosmology Scuola Normale Superiore, Pisa, Italy & Kavli IPMU, Tokyo, Japan. overview. Hayashi-sensei. Prof. Hayashi, 1920-2010. overview. Main topics. Formation of Pop III Stars Pop III to Pop II Transition

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Summary Talk

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  1. Summary Talk Andrea Ferrara 4C - Center for Computational Chemistry and Cosmology Scuola Normale Superiore, Pisa, Italy & Kavli IPMU, Tokyo, Japan

  2. overview Hayashi-sensei Prof. Hayashi, 1920-2010

  3. overview Main topics • Formation of Pop III Stars • Pop III to Pop II Transition • Stellar Archaeology • First Supernovae and Gamma-Ray Bursts • Primordial Galaxies and their observability • Cosmic Reionization and Background Radiation • Growth of Massive Black Holes at High-z

  4. AN OVEVIEW OF THE YOUNG UNIVERSE First Stars luminosity functions metals & dust black holes stellar populations outflows ? LBGs LAEs High-z Galaxies metal enrichment reionization IGM visibility

  5. First stars FORMATION • THE KEY ROLE OF DISKS • Rotationallysupported disk becomesToomreunstable • Coolingprovided by H2lines > CIE > H2dissociation • Fragmentsform in the central/externalregion of disk • Disk continue to accrete atfaster rate thanprotostarfeeding • Fragmentsmigrate to center due to gravitationaltorques • Half of them merge with centralprotostar: accretionbursts ? • Some of them are slingshot: browndwarfs/verylow mass starsatz=0 ? • But.. Are thesefragmentsbound ? Will theysurvive ? • No-sink-particlesimulationstimescalelimited to < 10 yr FINAL OUTCOME YET UNKNOWN

  6. First stars

  7. First stars FORMATION • THE ROLE OF RADIATIVE FEEDBACK • Quenchesaccretionby disconnecting disk edge from envelope • Final mass of star limited to < 50 M. Also PopIII.2 mass decreases • Implies no PairInstabilitySupernovae • 3D RHD simulationssubstantiallyconfirmthisresult • Long integration time (>105 yr) required to followaccretionevolution CAN FRAGMENTATION OCCUR WITH FEEDBACK ? • THE ROLE OF TURBULENCE • Turbulencemightprevent disk formationby providing pressure support • Increasescore temperature (additionalthermalsupport) • Itsroleseems to be underestimated by <32 cell/Jeans lengthexperiments • Interpretation ? Too muchdissipation ? Short integration time ?

  8. First stars FORMATION • THE ROLE OF DARK MATTER • Producesheating/ionization of gas • Reducesfragmentation • Dark stars: conditions on DM cusp/protostardisplacement (<100 AU) ? • THE ROLE OF MAGNETIC FIELD • At formation of first core Ekin/EB=3600, i.e. subdominant • However, strength not yet saturated at formation of first core • Grows faster than flux freezing (B ≈ ρ1.78) • Due to vorticity generated by shocks/chemothermal grads • If small-scale turbulent dynamo operates very fast (10-4 tff) amplification

  9. First stars IN SITU DETECTABILITY • INDIRECT: HIGH-Z SUPERNOVAE • Super-luminous (1011 L) SNIIndetectedatz=2.05 (in interactinggalaxy) • Offset from center: are welookingat the PopIIIwave ? • Time dilationmakesidentificationdifficult; use shock breakout? • ReliablePopIII light curvesnowcomputed • JWSTmightseePISNs up to z=15-20 (ifverylucky) • DIRECT/LENSED DETECTION • Search in H-coolinghalos (veryfewstill metal-free) • Direct detection with JWST wouldrequire 10% baryons in stars • Lensingwoulddecreaseefficiencyrequirement to 0.1% • How to disentanglePopIIIgalaxies from normalones ?

  10. POPIII TO POPII TRANSITION CRITICAL metallicity HIGH-z DUST (Mostly) produced in cooling SN ejecta Reprocessed by reverse shock Further accretion and shattering in ISM Different extinction curve Different depletion factor H2 line cooling dust cooling OI, CII

  11. POPIII TO POPII TRANSITION CRITICAL metallicity C+O in gas phase C+O in gas phase + dust . . . . . . CONFLICTING THEORIES Zcr = 10−3.5 Z Zcr = 10−5±1 Z Caffau+2011 star: Z=10−4.35 Z (low mass) PuzzlingLi underabundanceatverylow [Fe/H]

  12. POPIII TO POPII TRANSITION TRANSITION DURING COSMIC EVOLUTION PopIII wave z=5 Pop III Pop II SNIIn z=2.05? z=3 • OBSERVATIONAL IMPLICATIONS • Increasingfraction of PopIIIgalaxies • Core collapse vs Hypernovae • Increasing rate of PopIIIGRBs

  13. STELLAR ARCHAEOLOGY THE POPIII PARADOX: WHERE ARE THEY ? • I. MILKY WAY HALO • No truly metal-free star detected in >30 years • No star with total metallicity Z < 10-4.5 Zyet found • Handful of UMP stars with [Fe/H] < −5 found • The Metallicity Distribution Function rapidly rolls-off at [Fe/H]< −3.5 • Abundance of C-rich ([C/Fe] >1) stars increase at low [Fe/H] • Lithiumplateau melts-down and scatter increases at low [Fe/H]; rotation ? • Nature of r-processes (i.e. [Sr/Ba]) changes at [Fe/H]< −3.5 • Fraction of EMP binaries as high as 10% SELECTION STRATEGY AND SPECTROSCOPIC ABILITY ARE KEY

  14. STELLAR ARCHAEOLOGY THE POPIII PARADOX: WHERE ARE THEY ? • II. CLASSICAL DSPH SATELLITES • Dwarf Metallicity-luminosity relation and MDFs require pre-enrichment • Environmental effects (tidal, ram-pressure stripping) play minor role • Lower [α/Fe] @ fixed [Fe/H] in dSphs than in MW halo (Loss ? Low SF ?) • Galactocentic distribution might reflect internal/external reionization • III. ULTRA FAINT DWARF SATELLITES • MDF shifted to lower [Fe/H] and broader (prolonged, low level SF) • Could be leftovers of the earliest galaxies, probably minihalos • Best candidates to search for PopIII stars (maybe Hercules ?) • “Failed” UFs could be identified with C-enhanced DLAs

  15. FIRST Sne AND GRBs SUPER/HYPERNOVAE • Pre-SN evolution/explosive nucleosynthesis/fate well understood • WD/NS/BH/PISN/BH sequence allows to predict metal ejection • Open problems: (i) mass loss (ii) rotation (> mass loss) (iii) mixing HN + FALLBACK MODEL EXPLAINS MOST EMP

  16. FIRST Sne AND GRBs GAMMA RAY BURsTS • Long GRBs are connected with H/SNe, supporting collapsar model • Record holders: (spec) 090423 z=8.2, (phot) 090429 z=9.4 • Much brighter than galaxies at same redshift: signposts of star formation • Host gas metallicities (low?), density; progenitor mass • Indication of a larger SFR at high z wrt to dropout galaxy determinations ? • Pop III GRBs: how to get rid of envelope ? need binary companion ? Mass-Metallicity relation for GRB hosts

  17. PRIMORDIAL GALAXIES First galaxies as a feedback laboratory • Gas/metal ejectionefficiencies of small and large galaxies • Turbulenceenergydissipation and injection • Positive or negative radiative feedback in relicregions ? • Suppression of galaxyformationbelow Jeans filtering mass? • Isitreally a sharpboundary ? Gentledecrease of bayonicfraction ? • Effects of global LW background: sterilization of MH ? • Role of dust and CMB for critical metallicity Chemical Radiative Mechanical

  18. HIGH REDSHIFT GALAXIES SEARCH TECHNIQUES DROP-OUTS • Sharp drop in flux shortwards than Lya line • Finding galaxy candidates at z>6 : using i, z, Y, J-drops. • Contamination by stars and low-z ellipticals LYMAN ALPHA EMITTERS • Narrow band filters tuned on redshifted Lyα line • Few and narrow atmospheric clean windows • Not all spectroscopically confirmed

  19. HIGH REDSHIFT GALAXIES LBG UV LUMINOSITY FUNCTIONS • UNCERTAINTIES • Interlopers can resemble high-zgalaxiesatlowS/N • Size/surfacebrightnessdistribution (incompletness) • Selectionefficiency • Cosmicvariance • Dustcorrections Isit a Schechterfunction ? Smoothevolution

  20. HIGH REDSHIFT GALAXIES STELLAR POPULATIONS • UV SLOPE: UNCERTAINTIES (fλ ~ λβ) • Bias favoring the selection of galaxies with bluer UV-continuum slopes • Source selection not independent of β measurement

  21. HIGH REDSHIFT GALAXIES STELLAR POPULATIONS • STELLAR MASS FUNCTION: SED UNCERTAINTIES • Initial Mass Function and Star Formation History • Dust-age degeneracy • Metallicity • Nebular emission lines contamination Where are the reionization sources ? Whatyouseeis whatisthere

  22. COSMIC REIONIZATION OVERVIEW • Overlappingbubblestructure. Initially in-out, later out-in • Reionization in high densitypeaksstartsearlier (density-biased) • Onlyabout 3 ion. phot/HI atom/Hubble time availableatz=6 • Reionization by z=6 requires d/dz = d(J /mfp)/dz  0 • QSO @ z=7.1: neutral/long lived vs. 10% neutral/short lived • Star formation in minihalosissterilized/evaporated by LW/Ion. background • Sources: > 50% from halos < 109 M  @ z>7 • Studyvia QSO abs.lines, CMB, 21cm, NIRB, kSZ, LAEs

  23. COSMIC REIONIZATION REIONIZATION TEST USING LAE xHI < 0.3 Best-fitting z=5.7 Ly LF z  6.5 3 attenuated z=5.7 Ly LF (minimum for neutral gas)

  24. COSMIC REIONIZATION VISIBILITY Theoreticalpredictions • EMERGING LYA: fα Lαint • Depends on: • HI column density (size) • dust amount • dust clumping • ISM μ-scale velocity field (turbulence) • bulk motions (outflows/inflows) • ISM EoS • orientation • morphology fα fα ~ (1+z)2.6 COMPLEXITY! • Statistical approach: “volumetric” escape fraction • (based on Lya and UV luminosity densities + SFR calibration)

  25. COSMIC REIONIZATION LOW REDHSIFT ANALOGS fesc LAEs showing Lyc emission NB359 R ACS 814 (900 Å) (1500 Å) (2000 Å) • VIMOS:8 detections • 5 objects displaced: superposition ? • 3 seem to be real Lyc emitters • Stellar pop fit of Lyc and UV slope Young, massive, metal-poor population ? z = 3.09

  26. COSMIC REIONIZATION DEEP LYA EMISSION SURVEYS • LAE/LBG LOW REDSHIFT PROXIES • Low mass (107-9 M) • Young (< 100 Myr) • Low extinction • Low metallicity • Continuous SFR • HIGH-Z COMPLICATIONS • Kinematics (infall/outflow) • Orientation • Duty cycle • IGM transmission • Different extinction law UV Low-zanalog of reionization sources ? LAEs

  27. HIGH-z BLACK HOLES Complex BH-stars interplay mediated by X-rays and metal opacity FORMATION • THE PROBLEM • SMBH of M=109 M observed at z=7.085 (t=0.77 Gyr) • Implications: (a) start early (b) (super-)Eddingtonrate at all times  Seed masses > 400 M DIRECT COLLAPSE STELLAR SEEDS Gas driven in rapidly (deep potential) Transfer angular momentum Avoid fragmentation Avoid cooling via H2 to T ~ few 100 K Continuous gas supply Avoid rad. fdbck depressing accretion rate Avoid ejection from halos and loosing BHs Avoid overproducing ~ 106 Mholes

  28. HIGH-z BLACK HOLES FORMATION PATHS UV LW background! H2 Collisional Dissociation ?

  29. HIGH-z BLACK HOLES MASS ACCRETION HISTORY • FEEDBACK-REGULATED BONDI ACCRETION • Less efficient accretion • Accretion rate proportional to thermal pressure inside the HII region • Flickering luminosity with different modes with period tcross ≈ RHII/cs • Some BH must accrete at Eddington rate; some not (X-ray background) Flickering luminosity

  30. March 11, 2011 Dedicated to the memory of those who are not with us anymore

  31. どうもありがとうございました Many, many thanks to The LOC and the people that made this possible.

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