summary talk andrea ferrara 4c - center for computational chemistry and cosmology scuola normale...
TRANSCRIPT
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
POPIII TO POPII TRANSITION
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
POPIII TO POPII TRANSITION
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
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 ?
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
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
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.