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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

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maximum aperture telescope workshop organized by aura chaired by jay gallagher

MAX-AT Workshop

Madison, Wisconsin, 27 - 29 August

Maximum Aperture Telescope WorkshopOrganized by AURAChaired by Jay Gallagher

basic ideas for very large aperture telescopes the case for continuing groundbased astronomy

MAX-AT Workshop

Madison, Wisconsin, 27 - 29 August

Basic Ideas for Very Large Aperture Telescopesthe case for continuing groundbased astronomy

Matt Mountain

Gemini Telescopes

August 1998

basic ideas for very large aperture telescopes the case for continuing groundbased astronomy4
Basic Ideas for Very Large Aperture Telescopesthe case for continuing groundbased astronomy
  • Goals
    • 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

Science

?

WHT

UKIRT

CFHT

WIYN

ARC

TNG

MPA

KPNO

IRTF

NTT

CTIO

AAT

ESO

LBT 1

HET

Keck 1

Keck 2

ORM

Gemini N

Subaru

LBT 2

Gemini S

MMT

Palomar

Magellan 1

Magellan 2

VLT 1

VLT 2

VLT 3

VLT 4

What is the case for a new groundbased facility?

“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 quality

and

optimized IR performance

framework for a science case
Framework for a Science Case

Where are our current science interests taking us?

lets be presumptuous

Adapted from Science, vol. 274, pg. 912

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)

  • 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

10”

Challenging 8m - 10m telescopes - Imaging Spectroscopy of the majority of objects in the HDF

4 mag.’s

Current Keck

spectroscopy limit

HDF Differential Number counts from Williams et al 1996

deconstructing high z galaxies
“Deconstructing High z Galaxies”

Integral field

observations of a

z = 1.355 irregular

HDF galaxy

(Ellis et al)

“Starformation histories

of physically distinct

components apparently

vary - dynamical data is

essential”

slide10

Going beyond Gemini

SN in Arp 220 (VLBI Harding et al 1998)

0.2”

0.4”

~ 0.01”

2”

“milliarcsecond scale

emission is common,

perhaps universal in

LIG’s”

deconstructing the m16 pillars with gemini

Beyond surveying M16 “pillars” for forming stars,

closer inspection with NIRI reveals bipolar outflow

Integral field

spectroscopy reveals

outflow dynamics

Coronagraph

reveals faint low

mass companion

AO+NIRS spectroscopy

shows spectrum of

a forming “super-Jupiter”

“Deconstructing the M16 Pillars with Gemini”

Embedded forming stars

Approximate field of view of

Gemini Mid Infrared Imager

going beyond gemini

Log10 Fu (mJansky)

x 30

Gemini

10 s, t = 10,000s

R = 1800

l (mm)

Going beyond Gemini

Solar System @ 10 pc

Jupiter

500 mas

Gilmozzi et al (1998)

Models for 1 MJ Planets at 10 pc from Burrows et al 1997

how we will be competitive from the ground
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 21 st century telescope
Sensitivity gains for a 21st Century telescope

For background or sky noise limited observations:

S(Effective Collecting Area)1/2 .

N Delivered Image Diameter 

For background or sky noise limited spectroscopy:

SEquivalent Telescope Diameter .

N Effective Aperture Width 

S/N x (106)1/2

  • To meet these scientific challenges:S/N  30 x S/N of a 8m ~ 10 m Telescope
the gains of ngst compared to a groundbased 8m telescope

Source noise background dark-current read-noise

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)1/2and 10% of the pixels are lost
slide16

Photon-limited performance averaging OH lines

Photon-limited performance between OH lines

Relative Signal to Noise (SNR) of NGST/Gemini

-- assuming a detected S/N of 10 for NGST on a point source, with 4000s integration

Intermediate cases

determined by

detection noise

2

10

10

2

slide17

Relative Signal to Noise (SNR) of NGST/Gemini

-- assuming a detected S/N of 10 for NGST on a point source, with 4000s integration

Spectroscopy between

the OH lines

2

2

telescopes can still be competitive from the ground
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
“its resolution stupid..”

Facility Baseline Collecting Area

(m) (m2)

  • Gemini 8-M 8 2 x 50
  • CHARA 354 5.5
  • Keck 1 & 2 + 165 157 + 11
  • VLTI + 200 201 + 20
its resolution stupid20
“its resolution stupid..”

Facility Baseline Collecting Area

(m) (m2)

  • 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 telescopessensitivity gains ~ 102over Gemini for point like sources
its collecting area stupid
“its collecting area stupid..”

Facility Baseline Collecting Area

(m) (m2)

  • Gemini 8-M 8 2 x 50
  • CHARA 354 5.5
  • Keck 1 & 2 + 165 157 + 11
  • VLTI + 200 201 + 20
its collecting area stupid22
“its collecting area stupid..”

Facility Baseline Collecting Area

(m) (m2)

  • 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 1963Goal: 0.01 arcsecond images at 2.2 microns signal/noise gains ~ 30 compared to an 8msensitivity gains ~ 103 over Gemini for point like sources
modeled characteristics of 20m and 50m telescope
Modeled characteristics of 20m and 50m telescope

Assumed point source size (mas)

20M 1.2mm 1.6mm 2.2mm 3.8mm 4.9mm 12mm 20mm

(mas) 20 20 26 41 58 142 240

50M 1.2mm 1.6mm 2.2mm 3.8mm 4.9mm 12mm 20mm

(mas) 10 10 10 17 23 57 94

h 70% 70% 50% 50% 50% 50% 50%

Assumed detector characteristics

1mm < l < 5.5mm 5.5mm < l < 25mm

Id Nr qe Id Nr qe

0.02 e/s 4e 80% 10 e/s 30e 40%

slide24

Groundbased

advantage

NGST advantage

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

slide25

Groundbased

advantage

NGST advantage

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

its sensitivity and resolution
“its sensitivity and resolution ..”

Facility Baseline Collecting Area

(m) (m2)

  • 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 1963Goal: 0.01 arcsecond images at 2.2 microns signal/noise gains ~ 30 - 60 over Geminisensitivity gains ~ 103 over Gemini for point like sources
adaptive optics will be essential

- and still a lot to understand

Adaptive Optics will be essential

Image profiles

are Lorenzian

16 consecutive nights of

adaptive optics the CFHT

ao performance on a 50m telescope31
AO performance on a 50m Telescope
  • Diffraction limited imaging constrained to small field of view

Chun, 1998

the challenge multiple laser beacons
The Challenge - Multiple Laser Beacons

- still a lot of technologies to develop

* * * * *

*

SRFA ~ 0.75 requires NBeacons

1.2mm 75

1.6mm 40

2.2mm 20

3.8mm 5

4.9mm 3

12.0mm <=1

20.0mm <=1

adaptive optics will be essential33
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 resolution

8K x 8K array (3mas pixels)

Imaging of the Universe at High Redshiftwith 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

Isoplanatic patch at

2.2 microns for 10mas

imaging

48 arcseconds

slide35

Going beyond Gemini

SN Remnants in Arp 220

(VLBI Harding et al 1998)

0.2”

0.4”

~ 0.01”

2”

“milliarcsecond scale

emission is common,

perhaps universal in

LIG’s”

observation scale lengths

Observations at z = 2 - 5

1 - 10 milli-

arcseconds

Velocity dispersion

R= 105 104 103 102 101

Imaging

Spectroscopy



10 AU

Galactic observations out to

1kpc at 10 mas resolution

Observation scale lengths

1 AU

1 R

100 AU

10 pc

100 pc

0.1 pc

Accretion Disks

Molecular

Cloud

Cores

Mol. Outflows

GMC

Protoplanetary

Disks

AGN

Jets/HH

Planets

Stellar

Clusters

spectroscopic imaging at 10 milli arcsecond resolution
Spectroscopic Imaging at 10 milli-arcsecond resolution

- using NGST as “finder scope”

  • Simulated NGST K band image
  • Blue for z = 0 - 3
  • Green for z = 3 - 5
  • Red for z = 5 - 10
  •  = 0.1

2K x 2K

IFU

0.005” pixels

l

48 arcseconds

slide38

OWL

OverWhelmingly Large

100-m diameter f/6.4

3 arc minutes FOV

Spherical primary &

secondary mirrors

50 meter telescope concept

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
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 challenges
Technology and “cost-benefit”challenges
  • Developing 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
“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 $40MTotal $1,086M

50m Telescope costs (1997$)

Scaled costs

Constrained

costs

S (Keck + Gemini + ESO-VLT + Subaru) = $1,560M

slide43

OWL

OverWhelmingly Large

Just to put things into perspective...

basic ideas for very large aperture telescopes the case for continuing groundbased astronomy45
Basic Ideas for Very Large Aperture Telescopesthe case for continuing groundbased astronomy
  • Goals - 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
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
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 W 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.