LAMA

LAMA

LAMA

Large Astronomical Mercury-Mirror Array

Paul Hickson University of British ColumbiaKen Lanzetta SUNY Stony BrookRick Puetter UC San DiegoGene Sprouse SUNY Stony BrookAmos Yahil SUNY Stony Brook

Photo Credit: S. Radford.

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Very Large Optical Telescope Concepts

“Continued progress in optical astronomy requires a telescope of aperture and resolution significantly larger than that of present instruments” – Next Generation CFHT CommitteeAperture in the range 30-100 meters is needed

Major Optical Telescope Projects/Proposals

2012?~ 1000 M$~ 50 mMAXAT

2007~ 800 M$8 m (space)NGST

2015+> 1000 M$~ 100 mOWL

2010?~ 600 M$~ 30 mCELT

First LightCostApertureProject

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Primary Science Goals

Detect and study the first luminous systemsStudy the process of galaxy formation and evolution from redshift z ~ 20 to the presentDetermine the star formation history of the UniverseDetermine the cosmological parametersResolve the innermost regions of AGN and QSOsDetect and study the oldest and faintest stars

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Observing Galaxy Formation

Photo Credit:NASA.

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Finding The First Galaxies

Wavelength range 0.4 < ? < 2.5 umLyman-a visible to z = 19.6

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Early Protogalaxies

Credit: NGST

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Importance of ResolutionHST 2.4m NGST 8m LAMA 60m

Photo Credit:NASA

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Early Globular Clusters

Credit: NGST

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Star-Formation History of the Universe?

Credit: NASA

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Supernova Detection

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nJy)

LAMA 2um 300s flux limitType II, k = 0, lambda = 0Type II, k = 0, lambda = 1

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Object Counts (per square arcmin)

0.4z > 10173Strong Gravitational lenses

45 < z < 1074z < 578Active Galactic Nuclei

10.5Supernovae II per year0.3z > 1055 < z < 1051z < 557Lyman-a emitters (R = 100)

202z > 10778675 < z < 101757708z < 52628781Galaxies1 (KAB = 31.4)10 (KAB = 28.9)Flux (nJy)

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Performance Goals

0.4 – 2.5 um wavelength range< 0.1 nJy detection limit for point sources< 1 nJy detection limit for galaxiesMilliarcsec resolution~ 100 square arcmin survey area:

> 105 galaxies~ 100 supernovae per year

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Emerging Technologies

Adaptive OpticsOptical interferometry Large mercury mirrorsNear-zenith tracking opticsOH absorption cellLarge VIS/NIR arrays

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Adaptive Optics FWHM = 0.08 arcsec

FWHM = 0.8 arcsec

Credit: Gemini Project

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Adaptive Optics Performance

Distance from Guide Star (arcsec)Credit: Matt Mountain

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Image Intensity

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Optical Interferometry NPOI

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Optical Interferometry

Frontier technologyPhase closure with independent telescopes has been demonstratedPrototype arrays: I2T, MkIII, IRMAOperational arrays: PTI, IOTA, NPOI, ISI, GI2T, SUSIUpcoming arrays: COAST, VLTI, KeckPhase errors within individual apertures are corrected with adaptive opticsMoving mirrors remove zero-point (piston) phase differencesPhase tracking on light from natural guide starLBT design gives interferometric imaging over 40 arcsec

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LBT Imaging Interferometer

2 x 8.4 m interferometer22.8 m baselinef/15 phase-combined beamLaser guide-star AO on individual telescopesPhase tracking on natural guide star40 arcsec FOV5 mas resolution in optical80-96% Strehl ratio in interferometric image

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Liquid-Mirror Telescopes

Three 3m telescopes in operationA 6m nearing completionA 4m project in Chile

Photo Credit: Chip Simons Photography

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Liquid-Mirror Technology

Strehl RatioS = central intensity/ideal central intensity

S = 0.81 measured in lab tests of 2.5m LM

S ~ 0.5-0.7 estimated for NODO 3m telescope

S ~ exp(-k2σ2)k = 2π/λσ = RMS OPD error

Images courtesy of Dr. E. Borra, Universite Laval

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Liquid-Mirror Interferometric Testing

Image courtesy of Dr. E. Borra, UniversiteLaval

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Liquid-Mirror Surface Quality

85 nm RMS error ð S = 0.93 at λ = 2 um

Image courtesy of Dr. E. Borra, Universite Laval

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Scattered Light

Credit: Dr. E. Borra, Universite Laval

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Mercury Telescopes NODO

Photo credit: Mark K. Mulrooney

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LMT Imaging Arp 270

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LMT Imaging Field Galaxies

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LMT Imaging Distant Cluster

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LMT Imaging Cluster Core

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Large Zenith Telescope

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6m Primary Mirror Truss

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LZT Mirror Truss

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Making the mirror-segment mold

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LZT Air Bearing

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LMT Tracking Optics

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Preliminary Design (Single element)

M1: 10 m f/1.5 parabolicM2: 0.75 m hyperbolicM3: 0.2 m flat2 compensation lenses5 min trackingRMS spot dia < 150 masStrehl ratio > 0.1 @ 2 um

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Background Light

Credit: Space Telescope Science Institute

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OH Absorption Cell

NIR sensitivity is directly proportional to backgroundGain of ~ 100 is possibleOH Production: Radiative excitation by Meinel photonsCollisional dexcitation in ~100 usColumn density > 1018 cm-2

Path length ~ 10 mPressure ~ 0.1 TorrLifetime ~ 10 msGas consumption ~ 2 kg/hr O3, 40 g/hr H

23 OOHHO +→+

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OH Absorption vs Column Density

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Sample Model Calculation (N = 1018 cm-3)

Before

After

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Cerro Chanjnantor

5000 m high desert in Northern ChileSite of ALMA millimeter arrayProposed site of Cornell IR telescope and several others

Photo credit: S. Radford

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Chajnantor Seeing vs Paranal (ESO VLT)

Credit: Cornell University

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LAMA Concept

Optical-NIR interferometerNear-zenith pointing and trackingSurvey fields around natural guide starsWavefront control on each element (AO)Phase tracking on all beamsDiffraction limit of 60m telescopeEquivalent area of 42m telescopeFully sample isoplanatic areaBackground reduction by gas-phase OH absorption cells0.1 nJ point source sensitivity (AB = 33.9)Mercury primary mirrorsHigh dry site (eg. Alto-Plano)Low project cost (~ $50M)

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Array Geometry

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60m

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Array Transfer Function

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Single-Element PSF

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LAMA PSF

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PSF Profile

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Encircled Energy

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Conceptual Design

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10m Array Element

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Survey Mode

~ 360 survey fields, each 30 x 30 arcsec~ 150 observations per year for each field

ò100 pJy detection limit for galaxies (0.1”)

10 pJy detection limit for point sources

ò90 square arcmin in one year~ 40,000 sec integration time

LAMA

Summary

A Very-Large Optical Telescope is feasible nowA 60 m optical interferometer would provide unprecedented sensitivity and resolutionGains of an order of magnitude or more over NGST are possiblefor survey-type observationsLiquid-Mirrors provide a way to beat the cost curve by a factor of 10-50Such a telescope could be built on a relatively short timescale (~ 6 yrs)