Evolution and Reionization of the Universe The Impact of the Hubble - - PowerPoint PPT Presentation
VulcanoWorkshop-24May2010 VulcanoWorkshop-24May2010 Evolution and Reionization of the Universe The Impact of the Hubble Space Telescope Nino Panagia (STScI/INAF-CT/Supernova Ltd) Main Phases of the
Nino Panagia (STScI/INAF-CT/Supernova Ltd)
Vulcano Workshop - 24 May 2010 Vulcano Workshop - 24 May 2010
Evolution and Reionization of the Universe The Impact of the Hubble Space Telescope
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Main Phases of the Universe Evolution
14.5 14.5
BIG BANG
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Dark Ages
Reionization
Primordial stars
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We know that the Universe is not quite ionized at redshift z~6.3
Becker et al. (2001)
Becker et al (2001): The full story
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Why do we care?
in the Universe
environment for galaxy formation and evolution
galaxies responsible for reionization may be the seeds of the most massive galaxies in the local Universe.
Basic processes
eV to be ionized a mass fraction 0.2×10-5 undergoing fusion is sufficient to re-ionize all hydrogen (in practice the required mass in stars is 10-100 times larger)
different (e.g. QSOs at 6.28 and 6.43).
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(e.g., Barkana & Loeb, Phys. Reports , 2001)
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Population III stars (Z=0)
Even “normal” mass stars with zero- metallicity would be much hotter than their solar analogues.
Tumlinson & Shull (2000)
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Let’s estimate the luminosity of reionization sources from first principles
Dense HI
HII region
Escaping UV radiation
A fraction f≤ 1 of UV radiation escapes and can ionize the Universe
Dense HI Dense HI
Some photons ionize dense hydrogen clouds that recombine → C≥ 1 Recombination lines escape, ∝(1-f) Some Lyman α escapes, ∝ Velocity width × (1-f)
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The Principles of Reionization (RI)
continuum photons
escape fraction, f, from the RI sources and the clumpiness of the IGM <Q> = <MHI> × f –1 × B(z1,z2,C)
required Ly-c photons HI mass = ρHI ×Volume escape fraction photons needed per ionization
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Recognizing the Reionization Agents
⇒ are doing it
⇒ have done it
⇒ the process of Reionization
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Reionization constraints for identical sources
Pop III - Z=0 Pop II - Z<Z/100
Stia iavelli, lli, Fall ll & Panagia ia (2004a)
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The effect of the IGM clumping on Reionization
[Stiavelli, Fall & Panagia 2004a]
Clumping factor C = <n2
H>/<nH>2
Effective number of photons to ionize an atom
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Can we detect the Sources of Reionization NOW?
It is not easy… but it can be done!
Let’s interrogate the sky:
The Hubble Ultra-Deep Field
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The Renaissance after the Dark Ages
Big Bang H II
z ~ 6
“Dark Ages”
TIGM ~ 4z K
z ~ 103 z ~ ∞
recombination t z
H I
TIGM ~ 104 K
normal galaxy S1
Here Now
primordial galaxy
Hubble Deep Field
Hubble Ultra Deep Field
e n d
r e i
i z a t i
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Location of the HUDF
1 8
Ultra Deep Field
“typical” z=6 galaxies
(Stiavelli, Fall, Panagia, 2004a)
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HUDF- z>5.5 objects
to begin seeing substructure in z>5 objects.
QSO at z=5.5 spectroscopically confirmed by GRAPES using ACS/GRISM GOODS selected z=5.8
S/N=100.
The large number of z>6 objects opens up the possibility of learning something about the reionization of the Universe.
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HIGH-z detections in the HUDF
find 4 candidate galaxies at redshifts 7-8 that “could play an important role in re-ionization at these redshifts”
imaging, find one candidate at possible redshift 6.5-7.
ISAAC, and Spitzer ST imaging up to 8.5µm, identify a galaxy at z≈7 (HUDF-JD2) that could have re-ionized its region of Universe
HUDF-JD2: A Distant Galaxy in the HUDF
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Combined Visible+Infrared
HUDF-JD2
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z = 7 no extinction
t = 50 Myr t = 100 Myr t = 300 Myr t = 500 Myr t = 600 Myr t = 800 Myr
The Balmer break is a prominent feature for stellar populations age t > 100 Myrs
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z=2.5-3.4
HUDF-JD2, a Balmer Break Galaxy prototype A galaxy that did it in the past?
[Mobasher et al. 2005]
z = 6.5 M = 6×1011 M Observed λ [µm] 0.5 1 2 5 10 Rest-frame [µm] 0.1 0.2 0.4 0.8
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Properties of HUDF-JD2
[Mobasher et al 2005, Panagia et al 2005]
Massive M/M = 6 × 1011 Bright L/L = 1012 Evolved Age > 350-650 Myr zform > 9 Ionizing Q ~ 4 × 1072 Ly-c photons
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HUDF-JD2
dereddened companions
Enough to re-ionize its region of Universe? By itself only if high escape fraction and low clumping Easily if undetectable companions with a reasonable LF are present
Panagia et al. 2005
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HUDF-JD2: A summary
reionization of the IGM starting a z~15
according to an α =1.6 Schechter LF it may account for the whole effect
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(2006) answer this question: “not quite”
photometry they detect about one bright BBG at z>5 every 9 square-arcmin field
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From Observations to Physical Parameters
– Photometric redshift – Age & formation redshift – Total Luminosity – Average Metallicity
– Present mass in stars
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An example of BBG candidate
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BBGs in the GOODS Deep-Field South
Insert table from Wikind et al
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Ionizing Properties of BBGs in the GOODS Deep-Field South
[Wiklind et al 2006, Panagia et al 2010]
18 BBGs in 160 arcmin2 <logL/L> = 11.9 <logM0/M> = 11.6 <logQ> = 72.5
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Re-Ionization Balance - I
Qobs = 5.1 × 1073 f Lyman-continuum photons
Qtot = 10.3 × 1073 f Lyman-continuum photons
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Lyman Continuum Photon Production History
BBG ionization is most efficient in the interval z~7-15
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Re-Ionization Balance - I
Qobs = 5.1 × 1073 f Lyman-continuum photons
Qtot = 10.3 × 1073 f Lyman-continuum photons
NH = 0.9 × 1073 atoms
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The effect of the IGM clumping on Reionization
[Stiavelli, Fall & Panagia 2004a]
Clumping factor C = <n2
H>/<nH>2
Effective number of photons to ionize an atom
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Re-Ionization Balance - I
Qobs = 5.1 × 1073 f Lyman-continuum photons
Qtot = 10.3 × 1073 f Lyman-continuum photons
NH = 0.9 × 1073 atoms
<Q> = <MHI> × f –1 × B ⇒ B/f = 11.5
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Re-Ionization Balance - II
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Re-Ionization Balance - II
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Re-Ionization Balance - II
to the reionization possible
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Re-Ionization Balance - II
to the reionization possible
should provide an equal amount of ionizing radiation.
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Re-Ionization Balance - II
to the reionization possible
should provide an equal amount of ionizing radiation.
steeper than α=1.3 quite reasonable
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Re-Ionization Balance - II
to the reionization possible
should provide an equal amount of ionizing radiation.
steeper than α=1.3 quite reasonable
with current telescopes but it will feasible with JWST.
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Reionization History
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Reionization History BBGs and WMAP
Amazing!
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WHO did it? Two basic possibilities
– Pop II – Pop I stars
– Pop III stars
Explore z=7-9 by obtaining NICMOS and ACS data complementary to the UDF.
UDF05 Team:
Beckwith, Bergeron, Dahlem, Ferguson, Kim, Koekemoer, Lucas, Mobasher, Panagia, Pavlovsky, Robberto, Stiavelli (PI) – STScI Baltimore Carollo, Lilly, Oesch – ETH Zurich Rix – MPA Heidelberg Gardner – GSFC Hook – ST ECF Garching
50
First results
The ACS observations were essential to rule out several low redshift interlopers.
The main result : there are fewer than expected z- and J-dropout
V i z J H ACS NICMOS
51
HUDF09
To implement this strategy HUDF05 team and the Illingworth-Bouwens team decided to join forces: they were awarded 192 orbits (PI: Illingworth) with WFC3 to
fields.
= NICP12 = NICP34
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Garth Illingworth
(UCO/Lick Obs & University of California, Santa Cruz)
Rychard Bouwens and the HUDF09 team STScI May 2010 BalOmore Stellar Popula,ons in the Cosmological Context
galaxy buildup in the first gyr: the nature of galaxies in the epoch of reioniza8on
galaxies in the first billion years Garth Illingworth firstgalaxies.org
1)
SM4 + WFC3/IR => z~8 galaxies & lots of z~7 (z~10?) (~500‐800 Myr)
2)
just 7 years a^er SM3b and ACS => z~6 galaxies (950 Myr)
revealing galaxies 13 billion years ago
>100 z~7 and z~8 galaxies properOes: sizes, UV colors, deep luminosity funcOons at ages 500‐800 Myr => in the heart of the reionizaOon epoch HST + Spitzer: SEDs, masses, mass density, ages LBGs and the star forming populaOon
data and results
what WFC3 enabled
galaxies in the first billion years GDI firstgalaxies.org
understanding galaxy forma6on and evolu6on……
galaxies in the first billion years GDI firstgalaxies.org
galac,c archaeology direct observa,on
we are remarkably fortunate to have two such powerful complementary approaches
WFC3/IR vs NICMOS
WFC3/IR has a “discovery efficiency” ~40X NICMOS comparing the old and new Hubble infrared cameras WFC3/IR NICMOS
to find a z~7 galaxy took ~100 orbits with NICMOS – with WFC3/IR it takes a few orbits
WFC3/IR is ~6X larger in area than NICMOS and much beler matches ACS
2.2 arcmin 3.4 arcmin ACS z~7 galaxies 2.2′ ′ x 2.2′ ′
NICMOS
WFC3/IR
galaxies in the first billion years GDI firstgalaxies.org
Oesch et al
NICMOS – 72 orbits
galaxies in the first billion years GDI firstgalaxies.org
WFC3/IR – 16 orbits
Big bang
galaxies in the first billion years GDI firstgalaxies.org
CDF‐S region is rich in data (HST, Spitzer, Chandra, etc)
1999‐2000 Chandra CDF‐S 2002‐2003 ACS GOODS 2003 ACS HUDF 2003 NICMOS HUDF 2004 Spitzer GOODS 2003‐2007 NICMOS 2005 HUDF05 2009 ERS 2009‐2010 HUDF09 2010‐2011 Chandra 4Ms 2010‐2012 CANDELS
CDF-South ~22’ x 22’
galaxies in the first billion years GDI firstgalaxies.org
an “astronomy public commons”
CDF‐S region is focus for HUDF09 & ERS (WFC3 and ACS)
Early Release Science (ERS) data taken ~65% of HUDF09 data taken: HUDF09 in aug 2009 HUDF09‐1 in nov 2009 HUDF09‐2 in feb 2010
remaining data to be taken later in 2010
galaxies in the first billion years GDI firstgalaxies.org
CDF-South GOODS Deep Optical ACS
~20’ x 20’ HUDF
searches for z~7‐8 objects in HUDF09 HUDF09WFC3/IR data
taken in late August 2009 very compeOOve area! within two weeks three groups had submiled papers on z~7‐8 galaxies, followed within a month by a fourth group, and then by a fi^h group in Dec Bouwens et al Oesch et al Bunker et al McLure et al Yan et al Finkelstein et al
z~7‐8 galaxies are just 600‐800 million years from t=0
galaxies in the first billion years GDI firstgalaxies.org
CDF-South GOODS Deep Optical ACS
Bouwens, Illingworth et al 2010a
first galaxies at z~8 from WFC3/IR
V i z Y J H
the two highest redshi^ z~8 galaxies detected not detected redshi^ ACS filters WFC3/IR z~8.4 z~8.7
galaxies in the first billion years GDI firstgalaxies.org
the other three z~8 galaxies all are H~28‐29 mag sources! searches conducted using the very robust and well‐tested photometric “dropout” technique Dropouts verified spectroscopically at z~2‐6 extensive tesOng for contaminaOon from photometric scaler, spurious sources, lower redshi^ sources…. WFC3/IR resoluOon helps separate galaxies from (rare) faint stars
2.4′ ′ x 2.4′ ′
first results: HUDF09 team’s 16 z~7 and 5 z~8 galaxies
HUDF09 WFC3/IR z~8 (650 Myr) Bouwens et al 2010a z~7 (800 Myr) Oesch et al
2010a
galaxies in the first billion years GDI firstgalaxies.org
HUDF09 image ~2.2′ boxes ~2.5′ ′
number of z~7 & z~8 galaxies is increasing quickly
HUDF09 fields WFC3/IR
updated z~7 and z~8 sample is sOll being checked but will be coming to a server near you soon… Bouwens et al (2010d)
galaxies in the first billion years GDI firstgalaxies.org
HUDF09 images: ~2.2′ number of z~7 & 8 galaxies has increased by ~5x in 6 months – 9 months ago the
current results: 101 z~7 & z~8 galaxies from ERS + HUDF09 fields
what have we learnt from the new HST data?
galaxies in the first billion years GDI firstgalaxies.org
these early galaxies are small
galaxies become very small at early Omes – does not appear to be a surface brightness effect (from simulaOons on lower redshi^ sources and stacking analysis) Oesch/Carollo et al 2010b
1.8′ ′ x 1.8′ ′ kpc galaxies in the first billion years GDI firstgalaxies.org
z~7 galaxies show considerable sub‐ structure
(0.3‐1)L* r½
size scales as (1+z)‐m where m = 1.12 ± 0.17
2 Gyr 1 Gyr
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc)
galaxies in the first billion years GDI firstgalaxies.org
Bouwens/Illingworth et al 2010b
these early galaxies are very blue
low luminosity galaxies become very blue at early Omes – low metals? UV‐conOnuum slope β most sensiOve to changes in dust content but dust content of lower luminosity, z>5‐6 galaxies is probably zero so changes at z>5‐6 must be due to
blue red
β
β is the power law slope of the UV continuum: fλ ~ λβ low luminosity <L*
galaxies in the first billion years GDI firstgalaxies.org
dust free at β < ~‐2.4 at β < ~‐2.8 standard populaOon models are challenged (even low metal abundance models) – need very low metallicity models?
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc) z>4 galaxies are very blue & fainter galaxies are even bluer (liele or no dust at z>5)
galaxies in the first billion years GDI firstgalaxies.org
luminosity func6ons
luminosity funcOons (LF) are key for determining the UV luminosity density and star formaOon rate densiOes exisOng z~4‐6 luminosity funcOons show that the slope is very steep at the faint end below L* (α ~ ‐1.75) the bulk of the integrated UV flux at high‐redshi^ comes from sub‐L* low luminosity galaxies
the changes in the LF with redshi^ are primarily at the bright end.
galaxies in the first billion years GDI firstgalaxies.org
steep faint end slope
z~4, 5, 6, 7, 8 LFs
z~4
luminosity func6ons
the new z~7 luminosity funcOon indicates that the very steep slope (α ~ ‐1.75) seen at lower redshi^ persists to higher redshi^ luminosity funcOons at z>7 are very important for establishing role of galaxies in reionizaOon
galaxies in the first billion years GDI firstgalaxies.org
excellent agreement now between the several groups
luminosity func6ons – implica6ons
dominant changes
massive end
galaxies in the first billion years GDI firstgalaxies.org
slope and density change very lille
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc) z>4 galaxies are very blue & fainter galaxies are even bluer (liele or no dust at z>5) the luminosity func6on at z>3 is very steep at α~1.7 => faint galaxies dominate the UV flux! changes are primarily at the bright end (>L*)
galaxies in the first billion years GDI firstgalaxies.org
striking results at z~7 from HST + Spitzer
Hubb le
HST NICMOS and Spitzer IRAC detecOons
Gonzalez, Labbé et al 2010a
stellar mass density at z ∼ 7 is 4.5 × 105 M Mpc-3
Fit to mean SED
Spitzer Model fits are BC03 CSF 0.2Z z~7 and ~300 Myr (SFH weighted age = t/2) with ~zero dust z~8
galaxies in the first billion years GDI firstgalaxies.org
Spitzer + HST powerful combina6on
Specific SFR (SFR/Mass) – derived from listed studies Gonzalez, Labbé, Bouwens, Illingworth et al 2010a constant SSFR at z>2 – strikingly so….
Spitzer z~8
galaxies in the first billion years GDI firstgalaxies.org
effect of nebular emission lines on ages & SF history?? invesOgate with deep Spitzer IRAC data in 3.6 and 4.5
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc) z>4 galaxies are very blue & fainter galaxies are even bluer (liele or no dust at z>5) the luminosity func6on at z>3 is very steep α~1.7 => faint galaxies dominate the UV flux! changes are primarily at the bright end (>L*) even at z~7‐8 (650‐800 Myr) indica6ons of an “older” popula6on (few hundred million years) => suggests some stars formed earlier at z>10
galaxies in the first billion years GDI firstgalaxies.org
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc) z>4 galaxies are very blue & fainter galaxies are even bluer (liele or no dust at z>5) the luminosity func6on at z>3 is very steep α~1.7 => faint galaxies dominate the UV flux! changes are primarily at the bright end (>L*) even at z~7‐8 (650‐800 Myr) indica6ons of an “older” popula6on (few hundred million years) => suggests some stars formed earlier at z>10 evolved galaxies appear to be rare at z>4 unless they have dis6nctly different characteris6cs (β is not con6nuous?)
galaxies in the first billion years GDI firstgalaxies.org
integrated proper6es…..
galaxies in the first billion years GDI firstgalaxies.org
new results
the star forma6on rate density
UV luminosity density Bouwens/Illingworth et al 2010d
high low galaxies in the first billion years GDI firstgalaxies.org
dust‐corrected SFR Madau 1998 formulation with Salpeter IMF
z>4 star‐forming galaxies are very small, blobby objects (r½ is sub‐kpc) z>4 galaxies are very blue & fainter galaxies are even bluer (liele or no dust at z>5) the luminosity func6on at z>3 is very steep α~1.7 => faint galaxies dominate the UV flux! changes are primarily at the bright end (>L*) even at z~7‐8 (650‐800 Myr) indica6ons of an “older” popula6on (few hundred million years) => suggests some stars formed earlier at z>10 evolved galaxies appear to be rare at z>4 unless they have dis6nctly different characteris6cs (β is not con6nuous?) the bulk of the star forma6on at z>3 is in the LBGs massive galaxies like SMGs/sub‐mm galaxies do not appear to contribute significantly to SFR
galaxies in the first billion years GDI firstgalaxies.org
these galaxies are small, low mass objects (half‐light radii of just 0.7 kpc at z~7‐8) they are extremely blue in color and are probably quite deficient in heavier elements they give us esOmates for the mass density and the star formaOon rate density that extends from just ~5% of the age
combining these results with Spitzer data suggests that these galaxies were forming stars ~200‐300 million years earlier, at z>10‐11 (with recent possible detecOons being found at z~10)
what these new observa6ons tell us S U M M A R Y
Hubble’s new Wide Field Infra‐Red Camera (WFC3/IR) has revealed many galaxies 13 billion years ago (at redshi^s z~7 and z~8), just 600‐800 million years from the big bang
galaxies in the first billion years GDI firstgalaxies.org
can we find galaxies at z~10?
galaxies in the first billion years GDI firstgalaxies.org
lots of reasons to expect galaxies at z~10+
can we find galaxies at z~10?
galaxies in the first billion years GDI firstgalaxies.org
PROBABLY??
but, it is very challenging with the current dataset……
what we can look forward to using
galaxies in the first billion years GDI firstgalaxies.org
24 May 2010 HST and the Early Evolution of the Universe 85
Big Bang H II
z ~ 6
“Dark Ages”
TIGM ~ 4z K
z ~ 103 z ~ ∞
recombination t z
H I
TIGM ~ 104 K
normal galaxy S1
Here Now
primordial galaxy
Hubble Deep Field
HUDF
e n d
r e i
i z a t i
JWST+ HST
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for the reionization of the IGM starting at z~15
have the potential of ionizing the IGM entirely
properties of “reionizers”
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24 May 2010 HST and the Early Evolution of the Universe 89