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MAX-AT Workshop Madison, Wisconsin, 27 - 29 August. Maximum Aperture Telescope Workshop Organized by AURA Chaired by Jay Gallagher. MAX-AT Workshop Madison, Wisconsin, 27 - 29 August. Basic Ideas for Very Large Aperture Telescopes the case for continuing groundbased astronomy. Matt Mountain - PowerPoint PPT Presentation
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Maximum Aperture Telescope Workshop
Organized by AURA
Chaired by Jay Gallagher
MAX-AT WorkshopMadison, Wisconsin, 27 - 29 August
Basic Ideas for Very Large Aperture Telescopes
the case for continuing groundbased astronomyMatt Mountain
Gemini TelescopesAugust 1998
MAX-AT WorkshopMadison, Wisconsin, 27 - 29 August
Basic Ideas for Very Large Aperture
Telescopesthe case for continuing groundbased
astronomyGoals Establish a framework for discussing the science case
for a Very or Extremely Large Aperture Telescope
Examine the challenges for 8m - 10m groundbased telescopes in an “NGST era”
Look at how a 21st Century groundbased telescope could extend and compliment the capabilities of an 8m NGST
Highlight some of the very real technical and cost-benefit challenges that have to be overcome
Make the case, that in an NGST era, with our current science interests, a groundbased 30m - 50m telescope is the necessary (if somewhat daunting) “next step”
What is the case for a new groundbased facility?
ORM
LBT 2
MMTSubaru
Gemini S
Palomar
WHT UKIRT CFHT WIYN ARC TNG MPA KPNO NTT CTIO AAT ESOIRTF
VLT 1
VLT 2
VLT 3
VLT 4
Keck 1 Keck 2 HET
Magellan 1
Magellan 2LBT 1
Gemini N
?
Science
“Observing and understanding the origins and evolution of stars and planetary systems, of galaxies, and of the Universe itself.” - Gemini Science Requirements, 1990
Large collecting area and
superb image qualityand
optimized IR performance
Framework for a Science Case
Where are our current science interests taking us?
Lets be presumptuous….-
21st Century astronomers should be uniquely positioned to study “the evolution of the universe in order to relate causally the physical conditions during the Big Bang to the development of RNA and DNA” (Giacconi, 1997)
Adapted from Science, vol. 274, pg. 912
Dynamics, abundances’ requires - spectral resolutions > 5,000 Isolating individual objects or phenomena requires - high spatial resolution Imaging spectroscopy at high spectral and spatial
resolution requires - collecting area
Challenging 8m - 10m telescopes - Imaging Spectroscopy of
the majority of objects in the HDF
Current Keck spectroscopy limit
4 mag.’s
HDF Differential Number counts from Williams et al 1996
10”
“Deconstructing High z Galaxies”
Integral fieldobservations of a z = 1.355 irregularHDF galaxy (Ellis et al)
“Starformation historiesof physically distinctcomponents apparently vary - dynamical data isessential”
2”
SN in Arp 220 (VLBI Harding et al 1998)
~ 0.01”
Going beyond Gemini
0.4”
0.2”
“milliarcsecond scaleemission is common,perhaps universal inLIG’s”
“Deconstructing the M16 Pillars
with Gemini”
Approximate field of view ofGemini Mid Infrared Imager
Embedded forming stars
Beyond surveying M16 “pillars” for forming
stars,closer inspection with NIRI reveals bipolar
outflowIntegral fieldspectroscopy
revealsoutflow dynamics
Coronagraphreveals faint lowmass companion
AO+NIRS spectroscopyshows spectrum of a forming “super-
Jupiter”
Going beyond GeminiJupiterSolar System @ 10 pc
500 mas
Gilmozzi et al (1998)
Lo
g1
0 F
(
Jan
sky)
m)
10 t = 10,000s R = 1800
Geminix 30
Models for 1 MJ Planets at 10 pc from Burrows et al 1997
How we will be competitive from the ground
The “Next Generation” Space Telescope (NGST) will probably launch 2006 - 2010 an 6m - 8m telescope in space
NGST will be extremely competitive for: deep infrared imaging, spectroscopy at wavelengths longer than 3 microns
Groundbased telescopes can still compete in the optical and near-infrared moderate to high resolution spectroscopy
Groundbased facilities can also exploit large baselines high angular resolution observations
Sensitivity gains for a 21st
Century telescope
For background or sky noise limited spectroscopy:
S Equivalent Telescope Diameter .
N Effective Aperture Width
For background or sky noise limited observations:
S (Effective Collecting Area)1/2 .
N Delivered Image Diameter
To meet these scientific challenges: S/N 30 x S/N of a 8m ~ 10 m Telescope
S/N x (106)1/2
The gains of NGST compared to a
groundbased 8m telescope Assumptions (Gillett & Mountain 1998)
SNR = Is . t /N(t): t is restricted to 1,000s for NGST
Assume moderate AO to calculate Is
N(t) = (Is . t + Ibg. t + n . Idc + n . Nr2)1/2
For spectroscopy in J, H & K assume “spectroscopic OH suppression”
When R < 5,000 SNR(R) = SNR(5000).(5000/R)1/2
and 10% of the pixels are lost
Source noise background dark-current read-noise
Relative Signal to Noise (SNR) of NGST/Gemini-- assuming a detected S/N of 10 for NGST on a point source, with 4000s integration
Photon-limited performance between OH lines
Photon-limited performance averaging OH lines
Intermediate casesdetermined bydetection noise
2 10 2 10
Relative Signal to Noise (SNR) of NGST/Gemini-- assuming a detected S/N of 10 for NGST on a point source, with 4000s integration
2 2
Spectroscopy betweenthe OH lines
Telescopes can still be competitive from the ground
NGST will be very competitive for: deep infrared imaging, spectroscopy at wavelengths longer than 3
microns
Groundbased telescopes can still compete in the optical and near-infrared moderate to high resolution spectroscopy
Groundbased facilities can also exploit large baselines high angular resolution observations
The science case for groundbased “Maximum Aperture Telescope” must exploit the observational requirements for imaging spectroscopy, requiring:
1. High spatial resolution to isolate individual objects or phenomena
2. Moderate to high spectral resolution spectroscopy for dynamics and abundance measurements
3. An effective telescope diameter of ~ 50m to complement NGST (and the MMA)
10 milliarcsecond imaging spectroscopy to 28 - 30 magnitudes
“its resolution stupid..”
Gemini 8-M 8 2 x 50 CHARA 354 5.5 Keck 1 & 2 + 165 157 +
11 VLTI + 200 201 + 20
Facility Baseline Collecting Area (m) (m2)
“its resolution stupid..”
Gemini 8-M 8 2 x 50 CHARA 354 5.5 Keck 1 & 2 + 165 157 + 11 VLTI + 200 201 + 20 VLIA ~ 1000 800 (16 x 8m)
Goal: 0.001 arcsecond images at 2.2 microns signal/noise gains ~ 10 compared to 8m telescopes sensitivity gains ~ 102 over Gemini for point like sources
Facility Baseline Collecting Area (m) (m2)
“its collecting area stupid..”
Gemini 8-M 8 2 x 50 CHARA 354 5.5 Keck 1 & 2 + 165 157 +
11 VLTI + 200 201 + 20
Facility Baseline Collecting Area (m) (m2)
“its collecting area stupid..”
Gemini 8-M 8 2 x 50 CHARA 354 5.5 Keck 1 & 2 + 165 157 + 11 VLTI + 200 201 + 20 20 m 20 316 50-M Telescope 50 1963
Goal: 0.01 arcsecond images at 2.2 microns signal/noise gains ~ 30 compared to an 8m sensitivity gains ~ 103 over Gemini for point like sources
Facility Baseline Collecting Area (m) (m2)
Modeled characteristics of 20m and 50m telescope
Assumed detector characteristics
m <m 5.5m <m
Id Nr qe Id Nr qe
0.02 e/s 4e 80% 10 e/s 30e 40%
Assumed point source size (mas)
20M 1.2m 1.6m 2.2m 3.8m 4.9m 12m 20m (mas) 20 20 26 41 58 142 240
50M 1.2m 1.6m 2.2m 3.8m 4.9m 12m 20m (mas) 10 10 10 17 23 57 94
Relative Signal to Noise Gain of groundbased 20m and 50m
telescopes compared to NGST -- assuming a detected S/N of 10 for NGST on a
point source, with 4x1000s integration
Gro
un
db
ased
ad
van
tag
eN
GS
T a
dva
nta
ge
1 101E-3
0.01
0.1
1
10
1001 10
1E-3
0.01
0.1
1
10
100
50m R=10,000
20m R=10,000
Wavelength (m)
1 101E-3
0.01
0.1
1
10
1001 10
1E-3
0.01
0.1
1
10
100
50M R=5
20m R=5
S/N
Ga
in
Wavelength (m)
Relative Signal to Noise Gain of groundbased 20m and 50m
telescopes compared to NGST -- assuming a detected S/N of 10 for NGST on a
point source, with 4x1000s integration
Gro
un
db
ased
ad
van
tag
eN
GS
T a
dva
nta
ge
1 101E-3
0.01
0.1
1
10
1001 10
1E-3
0.01
0.1
1
10
100
50m R=1000
20m R=1,000
S/N
Ga
in
Wavelength (m)
1 101E-3
0.01
0.1
1
10
1001 10
1E-3
0.01
0.1
1
10
100
50m R=30000
20m R=30,000
Wavelength (m)
“its sensitivity and resolution ..”
Gemini 8-M 8 2 x 50 CHARA 354 5.5 Keck 1 & 2 + 165 157 + 11 VLTI + 200 201 + 20 20 m 20 316 50-M Telescope 50 1963
Goal: 0.01 arcsecond images at 2.2 microns signal/noise gains ~ 30 - 60 over Gemini
sensitivity gains ~ 103 over Gemini for point like sources
Facility Baseline Collecting Area (m) (m2)
50m Point Source Sensitivities
10 10,000s
1 10
100
101
102
103
104
105
106
R=10000
R=1000
R=5
Flu
x d
en
sity
(n
Jy)
Wavelength (m)
50m Point Source Sensitivities
10 10,000s
1 10
30
20
10
30
20
10
R=10,000
R=1,000
R = 5
Ma
gn
itud
es
Wavelength (m)
Adaptive Optics will be essential
16 consecutive nights of adaptive optics the CFHT
Image profilesare Lorenzian
- and still a lot to understand
AO performance on a 50m Telescope1k actuator AOS on 50-m (10% Seeing)
00.10.20.30.40.50.60.70.80.9
1
0 10 20 30 40 50 60
Field Angle (arcsec)
Str
eh
l
1.2 micron
1.6 micron
2.2 micron
3.8 micron
4.9 micron
12 micron
20 micron
Chun, 1998
AO performance on a 50m Telescope
5k actuator AOS on 50-m (Median Seeing)
00.10.20.30.40.50.60.70.80.9
1
0 10 20 30 40 50 60
Field Angle (arcsec)
Str
eh
l
1.2 micron
1.6 micron
2.2 micron
3.8 micron
4.9 micron
12 micron
20 micron
Diffraction limited imaging constrained to small field of view
Chun, 1998
The Challenge - Multiple Laser Beacons
* * * * **SRFA ~ 0.75 requires NBeacons
1.2m 75 1.6m 40 2.2m 20 3.8m 5 4.9m 3 12.0m <=1 20.0m <=1
- still a lot of technologies to develop
Adaptive Optics will be essential
Diffraction limited imaging will be constrained to small field of view
How does this constrain the science?
Imaging of the Universe at High Redshift
with 10 milli-arcsecond resolutionSimulated NGST K
band image Blue for z = 0 - 3 Green for z = 3 - 5 Red for z = 5 - 10 = 0.1
48 arcseconds
Isoplanatic patch at2.2 microns for 10masimaging
8K x 8K array (3mas pixels)
2”
SN Remnants in Arp 220 (VLBI Harding et al 1998)
~ 0.01”
Going beyond Gemini
0.4”
0.2”
“milliarcsecond scaleemission is common,perhaps universal inLIG’s”
Observation scale lengths
1 R 1 AU 100 AU 0.1 pc 10 pc
Accretion Disks
Protoplanetary Disks
Planets
Molecular Cloud Cores
Jets/HH
GMC
Mo
l. O
utf
low
s
StellarClusters
1 - 10 milli-arcseconds
Observations at z = 2 - 5
AGN
Galactic observations out to1kpc at 10 mas resolution
10 AU
Spectroscopy Imaging
100 pc
Velo
city
dis
pers
ion
R=
10
5 10
4 10
3 10
2 10
1
Spectroscopic Imaging at 10 milli-arcsecond resolution
Simulated NGST K band image
Blue for z = 0 - 3 Green for z = 3 - 5 Red for z = 5 - 10 = 0.1
48 arcseconds
2K x 2K
IFU0.005” pixels
- using NGST as “finder scope”
100-m diameter f/6.43 arc minutes FOVSpherical primary & secondary mirrors
100-m diameter f/6.43 arc minutes FOVSpherical primary & secondary mirrors
100
20
126
8.3
5.7
OWLOWLOverWhelmingly LargeOverWhelmingly Large
F/1 50m diameter parabolic primary (Oschmann 1996)
50 Meter Telescope Concept
50 m
2m diameter adaptive secondary producing collimated beam, with 1 arcmin. FOV
50 m Design Performance
Concept:
Parabolic segmented primary to simplify polishing and testing
Primary mirror wind buffeting corrected by small 2m diameter adaptive secondary
Collimated beam used to relay focus to 2m “telescopes” at both Nasmyth foci
Diffraction limited performance across ~ 0.6 arcmin. FOV at = 2.2 microns
Technology and “cost-benefit”
challengesDeveloping multi-laser beacon, high order
adaptive optics or investigate atmospheric “tomography” near-diffraction limited performance is at the heart
of the MAX-AT science case
Choosing the most effective aperture A 50m requires producing and polishing over 1,900
square meters of “glass” equivalent to 39 Gemini’s or 25 Keck’s or over 20
HET’s
Deciding on which site or hemisphere…..
“What can it cost?”
Primary mirror assembly $622M Telescope structure & components $190M Secondary mirror assembly $11M Mauna Kea Site $78M Enclosures $70M Controls, software & communications $26M Facility instrumentation (A&G, AO) $35M Coating & cleaning facilities $9M Handling equipment $5M Project office $40M
Total $1,086M
50m Telescope costs (1997$))
Scaled costs
Constrained costs
Keck + Gemini + ESO-VLT + Subaru) = $1,560M
OWLOWLOverWhelmingly LargeOverWhelmingly Large
Just to put things into perspective...
The next step ?50m telescope
0
A 400 year legacy of groundbased telescopes
Basic Ideas for Very Large Aperture
Telescopesthe case for continuing groundbased
astronomyGoals - recap Establish a framework for discussing the science case
for a Very or Extremely Large Aperture Telescope
Examine the challenges for 8m - 10m groundbased telescopes in an “NGST era”
Look at how a 21st Century groundbased telescope could extend and compliment the capabilities of an 8m NGST
Highlight some of the very real technical and cost-benefit challenges that have to be overcome
Make the case, that in an NGST era, with our current science interests, a groundbased 30m - 50m telescope is the necessary (if somewhat daunting) “next step”
Workshop Summary (preliminary)
In view of the large number of science projects identified, there is sufficient scientific interest in building a 30-50m telescope observatory.
Moreover, there was consensus already at the end of the first day of the meeting that MAX-AT should be maximized to do science based on high resolution imaging and spectroscopy. 10 milli-arcsecond imaging spectroscopy at 28 - 30
magnitude
This Observatory should extend and complement the capabilities of NGST and the MMA
Workshop Science Cases (preliminary)
Planet formation Formation of stars and planetary systems (disks) Planet Formation Imaging of planets around nearby stars
Cepheids out to redshifts z~0.1 (measure H_0) measure matter and H_o in far fields
Measure t_o (age of stars) radioactive decay of Thorium in old giants below RGB tip.
Geometry of the Universe via Supernovae at z~3 (q_0) Main goal is to break degeneracy of omega matter and
omega lambda.