The Formation and Evolution of Galaxies

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The Formation and Evolution of Galaxies
What were the first sources of light in the
Universe?
z 1000
How were luminous parts of galaxies assembled?
How did the Hubble sequence of galaxy
morphologies form?
When? and what are the baryons doing?
How do galaxies interact with their environment?
What are the global histories of star-formation,
metal enrichment, and gas consumption?
What is the relationship between active galactic
nuclei and their host galaxies?
z 0
2
Key NGST capabilities for high z galaxies
Ly a at z 4 and 2000 Å at z 2 3 x resolution
and 9 x sensitivity of HST
0.5 1 mm
Follow hot (young) stellar light (l gt 1200 Å)
to very high redshifts z 30 Trace cool (old)
stellar populations (l gt 4000 Å) to z
10 Observe diagnostic emission (and absorption)
features 3700 6600 Å at 1.5 lt z lt 6.5 all
this at kpc-scale resolution at all z
Dressler core 1 5 mm
Stellar features (H-, CO) at 2 lt z lt 3 that are
immune to dust obscuration and present in stars
of age 107 lt t lt 1010 yr
5 10 mm
Thermal dust emission and mid-IR diagnostic
features (e.g. 3.3 mm and 7.7 mm PAH) of far-IR
energy sources
10 30 mm
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Extending the frontierUltra-Deep Imaging 0.510
mm
4 x 4 arcmin2
5000 galaxies to AB 28, x 10 to AB 34?
photometry, morphology and redshift
estimates
Extreme depths AB 34 in 106 s Extreme
redshifts Lyman ? to z 40 (?)
4000 Å to z 10
NGST should detect 1 MO yr-1 for 106 yrs to z ?
20 and 108 MO at 1 Gyr to z ? 10 (assuming most
pessimistic W 0.2)
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The physics of galaxy evolution Diagnostic 1-5
mm Spectroscopy
A Physical conditions (R 1000)
Key emission-line diagnostic features in 3727
7000 Å range are within 1 5 mm for 1.7 lt z lt
6.6, (c.f. ultraviolet desert at shorter l)

• Star-formation rate from Ha
• Metallicity from R23 OIIOIII/Hb
• Reddening from Ha/Hb
• AGN/stellar from OIII. NII, SII, OI,
  SIII
• Ages from continuum features

B Kinematics ? masses (R 300010000)

• Spatially resolved rotation curves in
• gaseous line emission, e.g. Ha within
• 15 mm for 0.5 lt z lt 6.6
• Spatially unresolved velocity dispersions
• in stellar absorption lines, e.g. Mg 5175,
• Ca triplet, and CO bands at 2.3 mm
• (at AB 24)

Diagnostics not only give physical conditions but
also enable associations to be made between
members of the population at different epochs.
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Inside the galaxiesSpatially Resolved
Photometry and Spectroscopy
Photometric and spectroscopic analysis of
components within galaxies shows nature of
star-formation, possible importance of merging,
and the emergence of present-day morphological
components
HDF analyses limited to small number of bright
objects at lesser resolution
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Unveiling the hidden UniverseThe mid-infrared
We know from COBE that 50 of the luminous
energy in Universe emerges in far-IR apparently
an important contribution from ULIRGs at high z
NGST may be required to identify sources at 15
mm, and at 30 mm is potentially the most
sensitive detector of thermal dust at z 2
Spectroscopy of the 3.3 mm and 7 mm PAH features
can characterize the energy source as starburst
or AGN
for the complete observational picture
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New windows on galaxy evolutionSupernovae as
probes of chemical evolution and star-formation
HST z 0.5
SN II give measure of star-formation rate. The
effects of the time lag between SN II and SN Ia
in the early Universe is seen today in
a-enrichment and r- and s-process metallicity
effects in Galactic halo
NGST can detect supernovae to very high redshifts
Expect 515 SN II yr-1 per 4?4 field at z gt 2,
and 110 yr-1 at z gt 4, I.e. of order 1 on every
deep image.
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The DRM programs in The Formation and Evolution
of Galaxies
1. Deep Imaging Survey 0.610 mm imaging of
1 x UltraDeep Field 16 x Deep Fields 2.
Deep Spectroscopy Survey 15 mm spectroscopy
of 100 galaxies R100 for deep
identifications 2500 galaxies R1000
diagnostic spectroscopy 200? galaxies R5000
kinematics (incl.10 mm) spatially-resolved 2-d
integral field spectroscopy 3. Clusters Imaging
and spectroscopy of high z clusters for direct
comparison with field galaxies 4. AGNgalaxy
connection Imaging and spectroscopy on high z
AGN hosts (esp. Type I) 5. Obscured objects
Extension of deep imaging to 30 mm with low R
spectroscopic follow-up for diagnostic
features 6. Supernovae Spectroscopic
follow-up of SN discovered in imaging surveys
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Summary NGST capabilities
NGST will extend the redshift domain and should
detect the first light in the Universe
NGST will provide a wealth of diagnostic
information on high redshift galaxies, 1 lt z lt 5,
when most stars in the Universe likely formed,
that would be extremely hard to obtain in any
other way.
NGSTs wavelength extension down to 0.6 mm gives
maximum spatial resolution and the use of Lyman
features at 4 lt z lt 9 and 2000 Å at z 2.
Extension longwards to 10 mm gives NIR stellar
features to z 35 and extension to 30 mm gives
detection of thermal dust emission and diagnostic
3.3/7.7 mm PAH features.
NGST capable of yielding large numbers of
systematically studied galaxies over very wide
redshift range allowing full interpretation of
individual objects within the population.
first light star-clusters or significant AGN
accretion (e.g. 108 LO at 1200 Å at z 20 W0.2)
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The Dressler Report HST Beyond
7.2 Fundamental questions in high redshift
astrophysics 1. What was sequence of mass
accumulation in central regions of galaxies 2.
What was the sequence of disk formation? 3.
When and where were the first heavy elements
formed? 4. What was the role of AGN in galaxy
formation? 5. How do the above depend on
environment mass, state of the primordial gas and
dynamics? 6. What were the conditions in the
dark ages 1000 lt z lt 5? 7. Were there
precursor events that preceded full-blown galaxy
formation?
Detection identification characterization
placement in context
7.3 Generic capabilities required 1. Wide
wavelength coverage (ideally 0.5 mm to 1 mm) 2.
Deep imaging at high spatial resolution 3.
Spectroscopy at R gt 103 , with spatial
resolution 4. Large samples to be studied in
survey mode
NGST
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Will the NGST high-z science be done before
2008?(1) Progress since 1995
0. Large redshift surveys at 0 lt z lt 1
1. The 3 lt z lt 4 population, and first objects
(galaxies) at z gt 5
2. The HDF and morphologies and sizes at high
redshift
3. The ultraviolet luminosity density L (z)
relation 0 lt z lt 5
4. Measures of metallicity in the Lyman a
forest and DLA systems
5. Detection of far-IR background and
preliminary identification of
ultra-luminous sub-mm sources at high redshift
? (a) earliest activity must be at z gtgt 5 and
likely distributed amongst small units
(b) importance of small and faint galaxies at
high z (c) need for physical
understanding rather than just phenomenology
(d) our present view is very biased towards
(1) active star-formation and (2) the
unobscured objects
These continue to strengthen the case for NGST !
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Will the NGST high-z science be done before
2008?(2) Progress to 2008
19992008 will see (a) a vast increase in
number of 8m nights (x 17)
(b) introduction of near-IR
spectrographs
in 12 mm waveband, including MOS
(c) continued
implementation of AO in the near-IR
(d) Impact of NICMOS data
and ACS (WF3) on HST (e) SIRTF
By 2008, it is reasonable to expect
(a) 0 lt z lt 1 will be thoroughly done with
samples of 105 galaxies (but this is not where
galaxies are assembled!) this provides ideal
complement to NGST programs at higher
redshifts (b) Ground-based IR
imaging/spectroscopy SIRTF will yield produce
large samples with redshifts 1 lt z lt 4 (for
luminous galaxies) and we will know when large
mature galaxies first appeared. Will probably
not know how since diagnostics and masses
will be difficult with spectroscopy from
ground. Bias towards star-formation will
remain at highest redshifts. (c) Highest
redshift will creep up despite redder wavelengths
and fainter fluxes. Unlikely we will reach the
limit, and even if we do, it is very unlikely
that we would know that we have!
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The outlook for NGST
It is reasonable to be pessimistic about
ground-based observations for (a) all deep
observations at l gt 2.2 mm (b) systematic
multi-line spectroscopy at 1 lt l lt 2
mm (OH emission and H20 absorption) (c)
anything requiring diffraction limited imaging
at l lt 1 mm or (wide-field) imaging at 1 lt l
lt 2 mm (c.f. AO) i.e. modest
progress in programs involving (d) the very
highest redshifts (e) systematic diagnostic
spectroscopy (f) stellar (CO-bandhead) masses
at high z (g) the energy sources in all except
the most luminous high z ULIRGs (c.f.
SIRTF) These are the central goals of NGST
program on the formation and evolution of
galaxies, which are therefore likely to remain
current
IR astronomy from the ground