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Wide Field Astronomy from Space
Steven Beckwith
Space Telescope Science Institute
January 9, 2002
1/9/2002 2
Limits:
Space advantages:
Low Bν
Small ∆Ω over FOV
PSF stability
Photometric stability
Full sky coverage
24 hr operation
Ground advantages
Large area telescopes
Upgradable detectors (increase/repair FOV)
High survey speed at BLIP 0.1
1
10
100
1000
10000
100000
0 0.5 1 1.5 2 2.5
Wavelength (µµµµm)
Backgro
und (
γγ γγ sec-1)
Zodiacal light
Paranal sky
S/N = t1/2 A ∆ν
hν
Fν
(Fν + ∆Ω Bν)1/2
1/2
( )
D = 6.5 m
θ = 0.3”
D = 2 m
θ = λ/D
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ACS Survey Workshop
Motivation:
To determine the potential for new surveys with ACS
To identify areas for teaming on large initiatives
Discussion findings:
Obvious synergism between galaxy formation, AGN
evolution, weak lensing, and cosmology (SN Ia) in
need for a ~1 ° HDF-like survey
Recognition of multiple science potential of deep and
wide surveys with HST
22-23 March 2001
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GOODs Legacy & Treasury Programs
Observations 300 arcmin2 in two fields: HDF-N, CDF-S
SIRTF: 3.6-24 µm (IRAC+MIPS), 600 hours
HST: 4 bands, 500 orbits ACS, near HDF depth
Chandra: 2x106 sec imaging; XMM: ~5x105 sec imaging
North South
Science Evolution of galaxies, 1 < z < 6
SN Ia detection via scheduling
AGN morphologies
Potential upgrades: wider fields for AGN, weak-lensing, DEEP fields
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All sky surveys
Space advantages: Low Bν Small ∆Ω over large FOV PSF stability Photometric stability Full sky coverage 24 hr operation
λλλλ (µµµµm) 10σσσσ mag t(sec) 4ππππ(days) 10σσσσ Mag t(sec) 4ππππ(days)
0.35 26.4 3.0 1.4 30.7 223 107
0.45 27.0 3.0 1.4 28.9 72 34
0.55 26.1 3.0 1.4 28.1 53 25
0.70 25.3 3.0 1.4 27.3 41 19
0.90 25.1 3.0 1.4 26.8 42 20
1.22 20.0 3.0 1.4 24.9 59 28
1.65 17.9 3.0 1.4 24.4 108 52
2.10 16.5 3.0 1.4 23.9 176 84
6.5m Ground 2m Space
Ground advantages Large area telescopes
Upgradable detectors
(large FOV)
High survey speed at BLIP
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Ideal limiting magnitudes
15
20
25
30
35
0 1 2 3
Wavelength (µµµµm)
Lim
iting M
agnitude
2m space
telescope
6.5m LSST
Space-survey science:
Earth-crossing asteroids (sens.)
Kuiper-belt objects (sens., ∆Ω)
Transient sources
Supernovae (e.g. SN Ia) (sens.)
Micro-lensing sources (# stars)
Dwarf stars: white, brown (sens.)
Quantify weak lensing in distant
galaxies (small ∆Ω, stable PSF)
Parallaxes of faint stars (sens.)
Rare objects (survey to R ~ 27m)
Eclipses of exo-planets (photometric
stability)
High z SN
DMT 8.4m
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-40 0 40 80 120
∆t (days)
28
27
26
25
24
23
I (mag)
z = 1.7
z = 1.4
z = 1.0
SN Ia Detection rate
WFPC2: 2 orbit
ACS: 2 orbit
LSST 4π
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SN 1998ff
A. Riess, F. Boffi & SNaZ Team
0.080 ”
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HD 209458b: Exoplanet eclipse
3 hours
Ingress Eclipse Egress
1σ ~ 2x10-4
5x10-4
Kepler selected as Discovery-class Mission
courtesy Brown et al. (2001)
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• Has a metallicity (abundance of
elements heavier than helium)
about one third that of the sun
HST/WFPC2
DSS
Globular Cluster 47 Tucanae
Contains about 106 stars,
at ~11 Gyr
courtesy R. Gilliland et al. (2001)
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NEO Hazard courtesy DMT consortium
http://dmtelescope.org/science.html
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Cumulative Distribution of NEAs
12 14 16 18 20 22
10
100
1000
10000
100000
# of NEAs larger
than 1km
5km 200m1km
Cumulative # of NEAs larger
than H
H
All Known NEAs
LINEAR Discoveries (43%)
Min theory (500)
Max theory (2100)
Known (424)
300m
4,000 –
77,000
Follow-up
problem ?
courtesy DMT consortium
http://dmtelescope.org/science.html
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Planned surveys with spacecraft
Galaxy, AGN evolution
HST/ACS, NGST
Supernovae, Λ
HST/ACS+NICMOS, SNAP
Eclipsing extra-solar planetary systems
Kepler
Astrometric surveys
Hipparcos, SIM, GAIA
∆Ω ~ λ/D
Bν ~ Zodiacal light
FOV ~ optics limit
λλλλ (µµµµm) 10σσσσ Mag t(sec)
0.35 30.7 223
0.45 28.9 72
0.55 28.1 53
0.70 27.3 41
0.90 26.8 42
1.22 24.9 59
1.65 24.4 108
2.10 23.9 176
2m Space
