Conference Summary
Richard Ellis
(Caltech)
ITALIA
View from Top Mountain Star
DEUTSCHLAND
SCHWEIZ
ÖSTERREICH
Galaxy Formation – Is the End in Sight?
LESSONS FROM THE PAST
Zeldovich (1978): “One can be pretty sure that the problem of
galaxy formation will be solved in the 1980’s”
1990’s: unwarranted confidence from theorists & observers:
extended SF histories was an early prediction of CDM models
matching optical data only
Madau et al 1996,
Baugh et al 1998
Galaxy Formation Issues
• Do we have a complete census of star formation activity and
baryon content at all epochs? - key role of multi-wavelength
techniques
• How did the Hubble Sequence emerge at z<1 from the varied
active and irregular sources at z > 2? What are the physical
processes involved? Are the detailed models correct?
• z > 6 the final frontier: did early galaxies reionize the Universe
and what early feedback processes shape the later assembly
history?
Challenges:
• Assumed physics & is it time invariant?
(IMF, stellar pops, modes of star formation, dust laws etc)
Disclaimer
58 talks × 30 slides = 1740 slides
AND 54 posters
All carefully digested, rationalized, intercompared with results in the literature to give a
“lucid, crisp, holistic view of our present
understanding of the formation of galaxies…..”
What follows is a brief, personal, selection of key issues
Apologies if your talk/poster (or even entire field!) is not
mentioned
Theoretical Progress
• Two ways to interpret galaxy data
- numerical simulations involving gas dynamics (SPH, GRID..)
- semi-analytic models (SAM)
• Both use stellar population modeling to match masses,colors, dust
(Tonini, Henriques, Silva, Mentuch)
• This conference: (Moore, Nagamine, Gonzalez, Somerville,
Narayanan)
- Complementarity of SPH and AMR simulations
- Claimed successes: cosmic SFH, local TF relation,
morphologies of z~3 galaxies, origin of SMGs, AGN
feedback
• Controversies
- Hydro: “AGN feedback overstressed in semi-analytic models”
- SAM – need top heavy IMF to explain SMG counts
Nagamine
Reproducing Local TullyFisher Relation &
Resolving Angular
Momentum Problem
Governato et al 2006
10^5 SPH particles in total, 500pc resolution
Better match with T-F.
Huge spheroid, disk is unresolved single phase cold gas
Moore
SMGs form in Mergers
Desika Narayanan
Narayanan, Hayward et al. 2009a
Chapman, Casey
Ways Forward: Velocity Fields with ALMA
Narayanan et al 2009b: Major Mergers
Davé et al 2009: Harassment
Dec 15th 2009
Desika Narayanan Obergurgl
Sub-millimeter Galaxies Are Dissipative
SMMJ09431+4700 z=3.35 Gas Rich Mergers
30 kpc
SMMJ163650+4057 z=2.39
H7
H6
0.5”(4
kpc)
• projected
separation ~4 kpc
• velocity
difference
200 km/s
blue: CO 6-5 v=±150, red: +500±400
green: 1mm continuum
SMMJ16358+4105 z=2.45
CO 7-6 (red) on ACS
•CO 6-5
•~0.5” resolution (blue) & NICMOS
H7
+50
-80
(green)
1”
0.5”
CO 7-6
1”
500 km/s
Neri et al. 2003, Greve et al. 2005,
Tacconi et al. 2006, 2008, Swinbank
et al. 2009, Bothwell et al. 2009, Smail
et al. 2010, Engel et al. 2010
300 km/s
flux density (mJy)
v
•CO 7-6
•CO Size ~0.25”
FWHM (1.6 kpc)
2
1”
0
-1000
0
velocity offset (km/s)
Tacconi, Walter
1000
Low Metallicity Gas in High z Radio SMGs?
Chapman
Clustering of SMGs?
Progress from BLAST and enlarged redshift samples
Broadly consistent with earlier (noisy) estimates
Correlation length r0
BLAST power spectra P(k,z)
20%(?) of SMGs may end up as massive DRGs?
Not required that all DRGs form via one route
Viera, Chapman, Halpern
Blain et al 2004 Ap J 611, 725
Cosmic Star Formation History
Hopkins (2004), Hopkins & Beacom (2005)
- complementary diagnostics
- standardized IMF, cosmology, extinction law,
luminosity limit
Star
formation
rate per unit
comoving
volume
Redshift 
Peak z~2-3
UV, [O II], H, mid-IR
Nagamine
BLAST-IR Star Formation
Rates. (Grey disks have
MIPS photo-z contribution
removed.)
Optical-Steidel
Optical-Lilly
Halpern
Data at z~3-4 adequate test
Sawicki & Thompson (2006)
Nagamine
Emergence of Hubble Sequence:
Galaxy Demographics 0<z<3
Growing body of data at 1<z<3: formative period in galaxy
evolution
• Spectroscopic and photometric surveys (Le Fevre, Ilbert)
• Resolved dynamics of star forming galaxies (various)
• Mass-metallicity relation (Mannucci)
Formation of red sequence at z~0 (Faber, Hudson)
• Masses and colors of z~2-3 red galaxies (Henriques, Conselice)
• Evidence of star formation thresholds (Faber)
• Timescale of truncation and AGN feedback (Somerville, Faber)
• Morphology versus color (red disks)
Elmegreen et al 2009: Clumpy high redshift galaxies – chains, clusters etc.
Clumpy (10^8Mo), high star-formation rates, extended over ~10kpc radii
ACS images (Elmegreen et al)
Moore
The complex gas flows into a dark matter halo with a forming disk galaxy at a
redshift z=3. R=temperature, G=metals and B=density. (Agertz, Teyssier & Moore
2009). One can clearly distinguish the cold pristine gas streams in blue connecting
directly onto the edge of the disk, the shock heated gas in red surrounding the
disk and metal rich gas in green being stripped from smaller galaxies interacting
with the hot halo and cold streams of gas. The disk and the interacting satellites
stand out since they are cold, dense and metal rich.
Moore
IFU Spectroscopy 1<z<1.5 (Daniela Vergani, poster)
Resolved Dynamics (~100 pc resn!) via Combination of
Lensed Magnification and Keck Adaptive Optics
6 lensed galaxies 1.7 < z < 3.1
(linear magnification ~8-10)
revealing rotation in 5/6 cases
Rotation would not be revealed
without lensing magnification
Jones et al (astro-ph/0910.4488)
1 kpc = 0.13”
Mass – Metallicity Relation @ z~3
SINFONI data on LSD
and AMAZE programs:
Can argue z~3 is a
formative period where
most growth is in mass
(with only modest
increases in metal
content).
Subsequent evolution
is mostly in metallicity
F. Mannucci
Massive Red Galaxies @ z=2 are Small!
HST NIC2 sizes of a representative
sample of z~2-3 red galaxies with
M >1011 M: re~0.9 kpc
2-5 times smaller than comparably
massive z~0 ellipticals!
Growth in size but not mass?
van Dokkum et al (2008) (also
Conselice)
SDSS
halflight
radius
2<z<3
Reliability of Stellar Masses?
Older then the Universe!
Henriques
Effect of TP-AGB Stars
939 z~4 LBGs in GOODS-S
CB07 mass --TP
AGB stars
included
BC03 mass -- no TP AGB stars
• Inclusion of TP-AGB stars has little effect on UV- optical SED &
inferred stellar masses
• Few catastrophic failures refer to cases with marginal IRAC detections
Stark et al, in prep
Dynamical Masses: DEIMOS vs LRIS-R?
Efficiencies from June LRIS-R run (Drew Newman)
LRIS-R
600/1m
DEIMOS
G830/9000
Dynamical Masses & Fundamental Plane 1<z<1.7
• Dynamical masses for red spheroidals in era 1<z<1.7
• Keck: LRIS-R m(AB)<23.5; 8-12 hr integrations
Evol in FP
Newman, RSE et al (in prep)
Flow through the color-mass diagram for “central” galaxies
Red sequence
Dry merging
Blue cloud
88
Faber et al. 2007
9
10
Quenching band
11
12
A schematic model of average halo mass growth
15
14
SFR = f(Mhalo, z)
Log (Mhalo/M)
13
Mcrit
12
Star-forming band
11
10
C. Conroy, R. Wechsler, D. Croton
9
0
2
4
Redshift, z
6
8
Threshold Mass for Quenched Star Formation
0.4<z<0.7
• Stellar masses from Palomar Kband photometry for a large
(8000g) spectroscopic sample
(Keck DEEP2)
• The sites of star formation
appear to shift from including
high-mass galaxies at early
epochs (z~1-2) to only lowermass galaxies at later epochs.
0.5<z<1
• Using rest-frame U-B color as
a SF discriminant, stellar mass
functions reveal a threshold
stellar mass above which SF is
somehow quenched
Bundy et al Ap J 651, 120 (2006)
1<z<1.4
log stellar mass 
AGN Feedback
“Radio” mode feedback
“Quasar” mode
(eg. Granato et al., 2004, Springel
et al 2005)
(eg. Croton et al 2006, Bower et
al 2006 Okamoto et al 2007)
Radio
X-rays
Temperature
Quiescent hot gas accretes onto central
BH creating outflow (radio jet) which
suppresses cooling flow and associated
SF: may explain downsizing
Supermassive BH grows via merger of
two coalescing systems; cold disk gas
is driven onto the BH: may explain tight
BH mass - bulge relation
Popular Models of AGN Feedback
•
•
•
•
Reproducing local BJ
and K luminosity
functions
Switching “radio”
feedback off leads to a
population of very bright
galaxies formed in
cooling flows
But position of the LF
break is set by the
division between rapid
and hydrostatic cooling
haloes
But does this model
reproduce evolving
mass function and
hence the production
rate of quiescent earlytypes?
Bower et al (2006)
No AGN
Bj band
dust
No dust
MBJ
No AGN
K-band
MK
importance of different FB modes is mass-dependent:
 SN-driven winds remove baryons from small-mass halos
 some process(es) prevent cooling in large-mass halos (radio jets,
clumps, conduction, cosmic ray pressure?)
z=0
rss, Hopkins, Cox, Robertson & Hernquist 2008
Millenium Simulation
+ AGN Feedback
1 < z < 1.4
• Theorists are finally putting
their products on the web
• At last observers can make
their own judgements on how
well CDM really works!
0.7 < z < 1
• `Past light cone’ treatment of
MS permits direct comparison
with DEEP2/Palomar stellar
mass functions
• Comparison shows AGN
feedback prescription too
effective at high z: fewer blue
galaxies than observed
Stringer et al MN 393, 1127 (2009)
0.4 < z < 0.7
But do AGN live in quenched/quenching galaxies?
Nandra et al. 2006
And Is Morphological
Evolution Synonymous with
Color Transformation?
Log fraction of Red Sequence
Red passive disks in COSMOS
• significant fraction of red sequence
are disks, particularly at low masses
• red disks are more bulge-dominated
than higher z star-forming disks
• a key intermediate phase in the
transition to present day spheroidals
Bundy et al 0912.1077
Redshift
THE FINAL FRONTIER: Z > 7 GALAXIES
Big Bang
`First
light’
today
High Redshift Star Forming Galaxies
Lyman break galaxies:
Lyman alpha emitters:
Rest-frame UV continuum discontinuity
Located via narrow band imaging
The Spitzer Revolution: Stellar Masses
A modest 85cm cooled telescope can see the most
distant known objects and provide crucial data on
their assembled stellar masses and ages
SMB03-1: zspec=5.83 IRAC(3.6m)=24.2 (AB)
stellar mass = 3.4 1010 M age > 100 Myr
Balmer
break
IRAC
mass (M)
z=5.83
HST
VLT
age (yr)
Eyles et al (2005): to produce this mass since z~10 required 5-30 M yr-1
comparable to the ongoing SFR (6-20 M yr-1)
so should
see earlier examples if unobscured
Balmer Break as Age Indicator
z=7
t = 50 Myr
t = 100 Myr
t = 300 Myr
t = 500 Myr
t = 600 Myr
t = 800 Myr
Age is degenerate with star formation history but can infer time-averaged
star formation rate and compare this with actual on-going star formation rate
Stellar Mass Density
• Factor 5 growth in mass
V-drops
z~5
density over 4 < z < 6:
z~4 mass fn.
• Substantial mass density at
z~5 suggesting much activity
>300 Myr earlier (z > 7)
• Mass in place is integral of
the past activity
M* (z) 

z10
z 5
* (z)dV (z)
• Hard to reconcile implied
past SF with that observed for
luminous dropouts but
implied SF nonethless may be
sufficient to maintain
reionization
• Perhaps early SF is in sub-L*
galaxies or is obscured
Stark & Ellis 2006, Stark et al 2007, 2009
completeness limit
i-drops
z~6
A Rapid Drop in Lyα Emitters from 5.7<z<6.6?
• 1 deg2 SXDS field
with 608 photometric
and 121 spectroscopic
Lyα emitters
SXDS ~1.0 deg2
includes cosmic
variance errors
z=5.7
• Contrast with LBGs:
no evolution 3<z<5.7!
z=6.5
• Tantalizing fading
(0.m3) seen in the LF
of Ly  emitters over
a small redshift
interval 5.7< z< 6.6
(150 Myr)
~30%
• Does this mark the
end of reionization
corresponding to an
increase in xHI (e.g. xHI
~0.6 at z~7)?
Ouchi et al (2009)
Searching for Ionized Bubbles
Bubble??
Lya emitting dropout
Size of
HUDF/WFC
3
UV bright dropouts
Ouchi et al. (2009b, ApJ, 706, 1139)

z~7 z-dropouts appear strongly clustered.


Ouchi
Lya emitting dropout sits at the center of overdense region of 4
UV brightest galaxies (~30Mpc )
Speculation: The overdense region makes a well-established
ionized bubble (>30Mpc) that allow the dropout to transmit Lya to
observers in partially neutral IGM? → Spec. follow-up
Testing Reionization via Fraction of Ly α Emitters
• Keck can probe redshift-dependent Lyα emitting fraction within continuumselected Lyman break population
• Via z~7 WFC3/IR candidates can test for reduced Lyα fraction claimed by
Subaru narrow band surveys
?
See also Clement
Stark et al, in prep
Hubble WFC3 High z Stampede
WFC3/IR: 850 - 1170nm
2.1  2.3 arcmin field of view
0.13 arcsec pixel-1
10 times survey power of NIC3
UDF 4.7 arcmin2
60 orbits in YJH
Reaches mAB~29 (5)
Bouwens et al 0909.1803
Oesch et al 0909.1806
Bunker et al 0909.2255
McLure et al 0909.2437
Bouwens et al 0910.0001
Yan et al 0910.0077
Labbé et al 0910.0838
Bunker et al 0910.1098
Labbé et al 0911.1365
Finkelstein 0912.1338
z >7 candidates from WFC3 UDF campaign
z’
Y
J
H
SED
2(z)
15 z > 7 candidates
3 IR filters c.f. 2 leads to more secure photometric
McLure et al (2009)
redshifts and reliable UV continuum slopes
But beware..uncertain redshifts still an issue..
z
Y
J
H
Results – I: Luminosity-dependent Evolution
Bouwens, McLure, Grazian
Results – II: z~7 Luminosity Function
α = -1.86 ± 0.33 (Oesch)
α = -1.72 ± 0.65 (Ouchi)
WFC3 UDF
NIC UDF
Ouchi 09 (Subaru)
- 10-16 z-band dropouts to YAB~28.5 corresponding to 6.5<z<7.5
Towards a reliable faint end slope: low star formers ~1 M yr-1 dominant
Abundance decline of ~2 since z=6
Oesch et al, Bunker et al 2009
-
Did Star Forming Galaxies Reionize the Universe?
cosmic
variance z~8
Stellar mass density at z~5-6 (and with greater uncertainty at z~7)
implies past SF in low luminosity galaxies may be sufficient for
reionization, especially if escape fraction of photons is >0.2
Stark et al 2007,2009; Labbé et al 2009ab
Will We Locate Pop III Stars?
Comoving SFR density
Pop III UV spectrum
nebula
stars
z
Bromm & Loeb (2006)
Schaerer (2002)
Signature of metal-free Pop III stars may be realized with high
quality spectroscopy (e.g. He II 1640 ~ 1-10% Ly  ) to z~14
NB: He II is only briefly visible in nebular phase (~ Myr)
Bouwens, see also Bunker, Finkelstein (and early paper by Stanway)
Testing the High z Stellar IMF?
Integral of star formation history
Observed
stellar
masses
Is there any hope of testing the IMF in high z galaxies?
SNe in z > 2 LBGs (CFHT SNLS)
object: 234161
2006
2005
2004
2003
host galaxy
mr = 24.9 ± 0.07
g’ r’ i’ filters
SNe in z > 2 LBGs (CFHT SNLS)
object: 234161
2005
host galaxy
mr = 24.9 ± 0.07
image
subtraction
SN is offset
from host
centroid by
2.8 ± 0.6 kpc
(physical)
SN event
integrated magnitude
mr = 26.3 ± 0.14
g’ r’ i’ filters
Confirmation of SNIIN (M > 40-60M)
gmax= 25.7
rmax= 25.2
i,max= 25.1
Keck LRIS spectrum of
LBG and supernova
Lyα at z=2.32
So far 6 SNIIn with z > 2
SN LBG
Cooke, RSE et al
Comparison of UV
luminosity density of
searched LBGs and
number of SNIIn tests
IMF in star-forming
galaxies at z>2 !
THE FUTURE
ALMA
SKA
Herschel
LMT
James Webb ST
Rawlings’ vision of complete
inventory of stars, HI, H2 etc
(no slide!)
TMT
Excitement of First Herschel Science Results
Hermes & Atlas teams
Oliver, Clements
Importance of Associated Facilities
Resolution comparison of BLAST, Herschel and JCMT at 500/450 microns
50 square arcmin simulation based on BLAST counts courtesy of Ed Chapin
Crucial roles for JCMT+SCUBA2, LMT + AzTEC, CCAT…
Dunlop, Arextaga, Hughes, Wilson
SPICA:
JAXA + ESA Cosmic Vision
3.5 m telescope
Cooled to < 6K
Instruments cover 5- 210 μm
-MIR spectro-photometer
-FIR imaging spectrometer.
-MIR Medium/High Resolution
Spectrometer
-MIR coronagraph
-Focal Plane Camera dedicated
to guidance
-FIR and sub-mm spectrometer –
optional
62
Results - Spectra
HBLR
z=0.0689
AGN2
z=0.015167
[NeV]
Obscuration
Extended source
strong PAH
strong [NeV]
Compact source
Spinoglio
Sy1
z=0.03301
The Multiplex Advantage
Looking closer at the SPIRE background sources
SPICA FIR FTS will take spectra of 7-10 sources/field
Images Rosenbloom, Oliver, Smith, Raab private communication
64
The Era of Extremely Large Telescopes
A new generation of 20-42m ELTs is being designed:
TMT
• Thirty Meter Telescope (www.tmt.org)
- Caltech, UC, Canada, Japan +China
- 30m f/1 primary via 492  1.4m segments
- $80M design underway (2004-2009)
- $300M raised so far
GMT
• Giant Magellan Telescope (www.gmto.org)
- Carnegie, Harvard, AZ, TZ, Australia, S Korea
- 21m f/0.7 primary via 7  8.2m segments
- funds for $50M design study being raised
• European ELT (www.eso.org/projects/e-elt)
- 42m f/1 primary with 900+ 1.4m segments
- 5 mirror design
- 57M Euros design underway (2007-2010)
E-ELT
A partnership between: Caltech, U. California, Canada (Japan, China, Brazil?)
AO impacts JWST-TMT Synergy
TMT with AO will have better
resolution than JWST (not a dream:
Keck AO has better resolution than HST)
– together with large aperture
significantly changes space-ground
synergy
First sources & cosmic reionization:
– TMT is key to locating more
abundant, fainter, smaller sources
(AO gives 10-100 gain over JWST
depending on angular size).
– JWST probes to higher z in mid-IR
Lensed galaxies at z ~6
Unlensed sizes ~ 150pc or < 30mas!
Thanks to Conference Organizers..& ESF Staff