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

• 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

AN OVEVIEW OF THE YOUNG UNIVERSE

First Stars

LBGs LAEs?

High-z Galaxies

metals & dustluminosity functions black holes

stellar populations outflows

IGM

visibility

metal enrichmentreionization

First stars

FORMATION

FINAL OUTCOME YET UNKNOWN

THE KEY ROLE OF DISKS

•Rotationally supported disk becomes Toomre unstable•Cooling provided by H2 lines > CIE > H2 dissociation •Fragments form in the central/external region of disk•Disk continue to accrete at faster rate than protostar feeding •Fragments migrate to center due to gravitational torques•Half of them merge with central protostar: accretion bursts ?•Some of them are slingshot: brown dwarfs/very low mass stars at z=0 ?•But.. Are these fragments bound ? Will they survive ?•No-sink-particle simulations timescale limited to < 10 yr

First stars

First stars

FORMATION

CAN FRAGMENTATION OCCUR WITH FEEDBACK ?

THE ROLE OF RADIATIVE FEEDBACK

•Quenches accretion by disconnecting disk edge from envelope•Final mass of star limited to < 50 M. Also PopIII.2 mass decreases•Implies no Pair Instability Supernovae•3D RHD simulations substantially confirm this result•Long integration time (>105 yr) required to follow accretion evolution

THE ROLE OF TURBULENCE

•Turbulence might prevent disk formation by providing pressure support•Increases core temperature (additional thermal support)•Its role seems to be underestimated by <32 cell/Jeans length experiments•Interpretation ? Too much dissipation ? Short integration time ?

First stars

FORMATION

THE ROLE OF DARK MATTER

•Produces heating/ionization of gas•Reduces fragmentation•Dark stars: conditions on DM cusp/protostar displacement (<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

First stars

IN SITU DETECTABILITY

INDIRECT: HIGH-Z SUPERNOVAE

•Super-luminous (1011 L) SNIIn detected at z=2.05 (in interacting galaxy)•Offset from center: are we looking at the PopIII wave ?•Time dilation makes identification difficult; use shock breakout?•Reliable PopIII light curves now computed•JWST might see PISNs up to z=15-20 (if very lucky)

DIRECT/LENSED DETECTION

•Search in H-cooling halos (very few still metal-free)•Direct detection with JWST would require 10% baryons in stars•Lensing would decrease efficiency requirement to 0.1%•How to disentangle PopIII galaxies from normal ones ?

POPIII TO POPII TRANSITION

CRITICAL metallicity

line c

oolin

g

H2

OI, CII

dust

coo

ling

HIGH-z DUST(Mostly) produced in cooling SN ejectaReprocessed by reverse shockFurther accretion and shattering in ISMDifferent extinction curveDifferent depletion factor


CRITICAL metallicity

C+O in gas phase

Zcr = 10−3.5 Z

C+O in gas phase + dust

Zcr = 10−5±1 Z

Caffau+2011 star: Z=10−4.35 Z(low mass)

Puzzling Li underabundance at very low [Fe/H]

.. ....CONFLICTING THEORIES

z=3

z=5

Pop IIIPop II

TRANSITION DURING COSMIC EVOLUTION

PopIII wave

OBSERVATIONAL IMPLICATIONS

•Increasing fraction of PopIII galaxies•Core collapse vs Hypernovae•Increasing rate of PopIII GRBs


SNIIn z=2.05?

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]•Lithium plateau 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%

STELLAR ARCHAEOLOGY

THE POPIII PARADOX: WHERE ARE THEY ?

SELECTION STRATEGY AND SPECTROSCOPIC ABILITY ARE KEY

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

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

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 relationfor GRB hosts

PRIMORDIAL GALAXIES

First galaxies as a feedback laboratory

• Gas/metal ejection efficiencies of small and large galaxies

• Turbulence energy dissipation and injection

• Positive or negative radiative feedback in relic regions ?

• Suppression of galaxy formation below Jeans filtering mass?

Is it really a sharp boundary ? Gentle decrease of bayonic fraction ?

• Effects of global LW background: sterilization of MH ?

• Role of dust and CMB for critical metallicity

Chem

ical R

adia

tive M

ech

anic

al

LYMAN ALPHA EMITTERS

• Narrow band filters tuned on redshifted Lyα line• Few and narrow atmospheric clean windows• Not all spectroscopically confirmed

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

HIGH REDSHIFT GALAXIES


LBG UV LUMINOSITY FUNCTIONS

UNCERTAINTIES

•Interlopers can resemble high-z galaxies at low S/N•Size/surface brightness distribution (incompletness)•Selection efficiency •Cosmic variance•Dust corrections

Smooth evolution Is it a

Schechter

functi

on ?


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


STELLAR POPULATIONS

STELLAR MASS FUNCTION: SED UNCERTAINTIES

•Initial Mass Function and Star Formation History•Dust-age degeneracy•Metallicity•Nebular emission lines contamination

OVERVIEW

•Overlapping bubble structure. Initially in-out, later out-in•Reionization in high density peaks starts earlier (density-biased)•Only about 3 ion. phot/HI atom/Hubble time available at z=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 minihalos is sterilized/evaporated by LW/Ion. background •Sources: > 50% from halos < 109 M

@ z>7 •Study via QSO abs.lines, CMB, 21cm, NIRB, kSZ, LAEs

COSMIC REIONIZATION

REIONIZATION TEST USING LAE

3 attenuated z=5.7 Ly LF (minimum for neutral gas)

Best-fitting z=5.7 Ly LF

z 6.5

xHI < 0.3

COSMIC REIONIZATION

VISIBILITY

• Statistical approach: “volumetric” escape fraction (based on Lya and UV luminosity densities + SFR calibration)

EMERGING LYA: fα Lαint

Depends on: (a) HI column density (size)(b) dust amount (c) dust clumping (d) ISM μ-scale velocity field (turbulence)(e) bulk motions (outflows/inflows)(f) ISM EoS(g) orientation(h) morphology

fα ~ (1+z)2.6

fα

COMPLEXITY!

Theoretical predictions

COSMIC REIONIZATION

LOW REDHSIFT ANALOGS

NB359 R ACS 814(900 Å) (1500 Å) (2000 Å)

fesc

• VIMOS:8 detections

• 5 objects displaced: superposition ?

• 3 seem to be real Lyc emitters

• Stellar pop fit of Lyc and UV slope

z = 3.09

COSMIC REIONIZATION

LAEs showing Lyc emission

Young, massive, metal-poor population ?

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

LAEs

UV

HIGH-Z COMPLICATIONS

•Kinematics (infall/outflow)•Orientation•Duty cycle•IGM transmission•Different extinction law

Low-z analog of reionization sources ?

HIGH-z BLACK HOLES

FORMATION

THE PROBLEM

•SMBH of M=109 M observed at z=7.085 (t=0.77 Gyr) •Implications: (a) start early (b) (super-)Eddington rate at all times

STELLAR SEEDS

Continuous gas supply Avoid rad. fdbck depressing accretion rate Avoid ejection from halos and loosing BHs Avoid overproducing ~ 106 M holes

DIRECT COLLAPSE

Gas driven in rapidly (deep potential) Transfer angular momentum

Avoid fragmentation Avoid cooling via H2 to T ~ few 100 K

Seed masses > 400 M

Complex BH-stars interplay mediated by X-rays and metal opacity

HIGH-z BLACK HOLES

FORMATION PATHS

H2 Collisional Dissociation ?

UV LW background!

HIGH-z BLACK HOLES

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)

MASS ACCRETION HISTORY

Flickering luminosity

March 11, 2011

Dedicated to the memory of those who are not with us anymore

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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Summary Talk