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.