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The Next Generation Space Telescope
Board on Physics & Astronomy
Steven Beckwith
April 28, 2000
102
1600
1700
1800
104
1900
Hubble ST
Photographic & electronic detection
Keck, VLT, Gemini ...
CCDs
Telescopes alone
Mount Palomar 200”
Soviet 6-m
Photography
106
Mount Wilson 100”
Rosse’s 72”
Herschell’s 48”
108
Short’s 21.5”
0
Huygens
eyepiece
Slow f ratios
Galileo
Sensitivity improvement
over the unaided eye
NGST
Telescopes & Discovery
101
2000
Year of observations
After Fig. 3.10 in Cosmic Discovery, M. Harwit
2
Galaxy Sizes in the HDF



No significant evolution
out to z~1
There is a small
population of compact
high-SB galaxies that
do not fit in the normal
Hubble Sequence
By z ~ 3, the normal
Hubble sequence
disappears and most
galaxies are compact
and high SB
3
z=2.5
z=1.5
z=0
Galaxy
Sizes
HDF galaxies
with z~1
Shifted to z=2.5
4
Lyman-break Galaxies
5
Unique Infrared Objects
Dickinson et al. 1999
Optical
Infrared
0.33
0.44
0.55
0.8
1.25
U
B
V
I
J
1.65 mm
H
6
Star-Formation Rates
• UV luminosity density
– Gives unobscured
star-formation
rate, metalformation rate
– Extinction
corrections
uncertain
• Consistent with other
measures of global
chemical evolution?
• Clustering & star
formation?
Madau et al. 1996, Rowan-Robinson et al. 1996…
Calzetti & Heckman 1999, Pei et al. 1999
7
Future Surveys
Haiman & Loeb 1998 model counts
NGST 106 s
ACS + WFC3 106 s
NICMOS 106 s
z >10
galaxies
quasars
Ly-break z=3
Ly-break z=4
HDFS phot z>5
8
NGST At a Glance
•
•
•
•
•
•
8m primary mirror
0.6-27 µm wavelength range
5 year mission life (10 year goal)
passively cooled to <50K
L2 orbit
- Logical successor to HST
3 Core instruments
- Key part of the Origins Program
– 0.6-5 µm camera
– 1-5 µm Multiobject Spectrometer
– 5-27 µm camera/spectrometer
• 2009 launch
9
NGST Concepts: Phase I
Lockheed Martin
TRW/Ball
10
Discovery Space
NGST
2009
2002
11
NGST: Core Science Goals
• Origin & Evolution of Galaxies
– The Dark Ages
• The Creation of the Elements
• The Birth of Galaxies
– History of the Milky Way & its
Neighbors
• Cosmology and Structure of the
Universe
• Birth of Stars
and Planetary
Systems
12
Origins and Evolution of Galaxies
Seeing the “Dark Ages”
• When and how do the first stars and galaxies form?
– HST and Keck have detected very luminous star
forming regions/galaxies that appeared 1 billion years
after the Big Bang (to z ~ 5.6)
– New stars appear to be forming at roughly a constant
rate until very recently (1 < z < 5)
– SCUBA may have detected a significant component of
dust-hidden star formation at cosmological distances
• To see the growth of galaxies such as our Milky
Way, we need NGST (0.6-10µm)
– Sensitivity to see the first epoch of star formation, (z ~
10-20, 0.1 nJy sensitivity in 1 week)
– Angular resolution and wide field to survey 100,000
protogalaxies and their environments (to z ~ 5)
– mid infrared imaging and spectroscopy to pinpoint the
nature of the hidden stars and Active Galactic Nuclei
13
Close-up shows little confusion
No Noise, AB ~ 35
NGST PSF, AB ~ 30
10”
15
The Epoch of Reionization
• Needs high sensitivity,
spectroscopy, R ~ 100.
• NGST capability ideal if
zreion > 7 (Lya > 1µm).
• NGST is uniquely capable if
Gunn-Peterson trough falls
in atmospheric absorption
region.
zreion = 8
zreion = 7
zreion = 11
16
Mapping Dark Matter
• Weak lensing is best method for measuring
masses of galaxies and structures for z >1.
– HST/NGST PSF ideal for faint, small background
galaxies (Mellier, Schneider)
– Large scale (linear) structure on scales of arcmin
or individual galaxy lensing on scales of ~ 10
arcsec gives polarizations ~ 1%, requires ~ 104
galaxies.
– Optical depths 5 x greater for zsource 1-> 5.
• NGST images yield ~ 104 galaxies with z >
2 per 4’ x 4’ field of view.
• RMS shear > 10% at z ~ 10 means dark
matter mapping is crucial component of
deep field surveys!
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NGST Deep Imaging: 0.5–10 mm
4’x4’
deep
survey
field
5000 galaxies to
AB ~ 28,
105 galaxies to
AB ~ 34
photometry,
morphology & z's
Depth:
AB ~ 34 in 106 s
Redshifts: Lyman a to z = 40 (?)
4000 Å to z = 10
NGST will detect 1 M yr-1 for 106 yrs
to z  20 and 108 M at 1 Gyr to z  10
(conservatively assuming W = 0.2)
Origins and Evolution of Galaxies:
Imaging & Spectra
• Multi-Object Spectroscopy
– Deep, R ~ 100, KAB~31
(Photometric redshift
verification)
– Emission line diagnostics,
KAB ~33 R ~ 1000,
• Star-formation rates
• Metallicities/reddening
• Kinematics of bound
groups/proto Milky Way
galaxies
NGC 7714 @ z = 6 (Kennicutt 1998)
Sensitivity (10 s)
~ 0.2 M yr-1 z ~ 7
~ 1.0 M yr-1 z ~ 12
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Hubble’s Law: Wmatter & WL
5.0
1.2
WMatter: 0.3
W
: 0.3
WL:Matter0.7
WL:
0.7
Redshift z
1.0
4.0
0.8
3.0
WMatter: 1.0
WL:
0.0
WMatter: 1.0
WL:
0.0
0.6
2.0
0.4
1.0
0.2
HST only
0.0
0
10
50
20
100
30
150
40
200
Luminosity distance (Billion light-years)
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Star and Planet Formation
• NGST will play an important role with its
near- and mid-infrared capabilities by:
– Determining the physics of star formation: the
assembly of stars and proto-planetary disks from
cloud cores
– Imaging and doing atmospheric studies of
Jupiter-sized planets at similar (5 AU) distances
around nearby stars (50 candidates within 8 pc,
needs a simple MIR Lyot stop)
– Inventorying the prebiotic materials in
starforming systems
Science
21
Evolution of Planetary Systems
Vega Disk Detection
l
(mm)
Flux* Contrast
(mJy) Star/Disk
11mm
2.4
1.5x107
22mm
400
2x104
33mm
1300
3x103
Reflected & emitted
light detected with a
simple coronograph.
*per Airy disk
NGST resolution at 24mm = 5 AU at Vega, > 10 pixels
across the inner hole
NGST & Extrasolar Planets
From Angel & Woolf 1998, in Science with the NGST, ASP, 133, 172
108
Fn (mJy)
• Control of primary
only:
– Jupiter at 10 < l
< 20 mm
• Active wavefront
correction to 30 nm
rms
– Direct detection
of Jupiter l > 0.4
mm
“Sun”
106
“Solar System" at 8 pc,
6m primary
104
102
ldiff=1 mm
1
0.01
Jupiter
10s
Earth
30nm
0.1
1
10
100
Wavelength (mm)
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Summary
• NGST gives advance in observing capabilities
over HST comparable to the advance of HST
• NGST can observe
– Acceleration/deceleration of expanding universe
– Cosmic dark matter
– First luminous objects after Big Bang, even if much
–
–
–
–
–
–
smaller than galaxies
Protogalaxies merging into large galaxies
First release of dust from first stars
Deep into active galactic nuclei
Individual stars in distant galaxies
Interstellar gas and dust
Recent formation of stars and planets
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