Comparative Performance of a 30m Groundbased GSMT and a 6 Comparative Performance of a 30m Groundbased GSMT and a 6.5m (and 4m) NGST NAS Committee of Astronomy & Astrophysics 9th April 2001 Matt Mountain Gemini Observatory/AURA NIO

Overview Science Drivers for a GSMT Performance Assumptions Results Backgrounds, Adaptive Optics and Detectors Results Imaging and Spectroscopy compared to a 6.5m & 4m NGST A special case, high S/N, R=100,000 spectroscopy Conclusions

GSMT Science Case “The Origin of Structure in the Universe” Najita et al (2000,2001) From the Big Bang… to clusters, galaxies, stars and planets

Mass Tomography of the Universe z~3 Hints of Structure at z=3 (small area) z~0.5 Existing Surveys + Sloan 100Mpc (5Ox5O), 27AB mag (L* z=9), dense sampling GSMT 1.5 yr Gemini 50 yr NGST 140 yr

Tomography of Individual Galaxies out to z ~3 Determine the gas and mass dynamics within individual Galaxies Local variations in starformation rate Multiple IFU spectroscopy R ~ 5,000 – 10,000 GSMT 3 hour, 3s limit at R=5,000 0.1”x0.1” IFU pixel (sub-kpc scale structures) J H K 26.5 25.5 24.0

Probing Planet Formation with High Resolution Infrared Spectroscopy Planet formation studies in the infrared (5-30µm): Planets forming at small distances (< few AU) in warm region of the disk Spectroscopic studies: Residual gas in cleared region emissions Rotation separates disk radii in velocity High spectral resolution high spatial resolution S/N=100, R=100,000, >4m Gemini out to 0.2pc sample ~ 10s GSMT 1.5kpc ~100s NGST X 8-10m telescopes with high resolution (R~100,000) spectrographs can detect the formation of Jupiter-mass planets in disks around nearby stars (d~100pc).

30m Giant Segmented Mirror Telescope concept GEMINI 30m F/1 primary, 2m adaptive secondary

GSMT Control Concept LGSs provide full sky coverage Deformable M2 : First stage MCAO, wide field seeing improvement and M1 shape control LGSs provide full sky coverage M2: rather slow, large stroke DM to compensate ground layer and telescope figure, or to use as single DM at >3 m. (~8000 actuators) Dedicated, small field (1-2’) MCAO system (~4-6DMs). Active M1 (0.1 ~ 1Hz) 619 segments on 91 rafts 10-20’ field at 0.2-0.3” seeing 1-2’ field fed to the MCAO module Focal plane

GSMT Implementation concept - wide field (1 of 2) Barden et al (2001)

GSMT Implementation concept - MCAO/AO foci and instruments Oschmann et al (2001) MCAO optics moves with telescope elevation axis MCAO Imager at vertical Nasmyth 4m Narrow field AO or narrow field seeing limited port

MCAO Optimized Spectrometer Baseline design stems from current GIRMOS d-IFU tech study occurring at ATC and AAO ~2 arcmin deployment field 1 - 2.5 µm coverage using 6 detectors IFUs 12 IFUs total ~0.3”x0.3” field ~0.01” spatial sampling R ~ 6000 (spectroscopic OH suppression)

Quantifying the gains of NGST compared to a groundbased telescope Assumptions (Gillett & Mountain 1998) SNR = Is . t /N(t): t is restricted to 1,000s for NGST Assume moderate AO to calculate Is , Ibg N(t) = (Is . t + Ibg. t + n . Idc .t + 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

Space verses the Ground Takamiya (2001)

Adaptive Optics enables groundbased telescopes to be competitive For background or sky noise limited observations: S  Telescope Diameter .  N Delivered Image Diameter B Where:  is the product of the system throughput and detector QE B is the instantaneous background flux

Adaptive Optics works well

Modeling verses Data GEMINI AO Data Model Results 2.5 arc min. 20 arcsec 2.5 arc min. Model Results M15: PSF variations and stability measured as predicted

Quantitative AO Corrected Data AO performance can be well modeled Quantitative predictions confirmed by observations AO is now a valuable scientific tool: predicted S/N gains now being realized measured photometric errors in crowded fields ~ 2% Rigaut et al 2001

Multi-Conjugate Adaptive Optics 2.5 arc min. Model results Tomographic calculations correctly estimated the measured atmospheric phase errors to an accuracy of 92% better than classical AO MCAO can be made to work MCAO

AO Technology constraints (50m telescope) r0(550 nm) = 10cm No. of Computer CCD pixel Actuator pitch S(550nm) S(1.65mm) actuators power rate/sensor (Gflops) (M pixel/s) 10cm 74% 97% 200,000 9 x 105 800 25cm 25% 86% 30,000 2 x 104 125 50cm 2% 61% 8,000 1,500 31 SOR (achieved) 789 ~ 2 4 x 4.5 Early 21st Century technology will keep AO confined to l > 1.0 mm for telescopes with D ~ 30m – 50m

MCAO on a 30m: summary MCAO on 30m telescopes should be used l > 1.25 mm Field of View should be < 3.0 arcminutes, Assumes the telescope residual errors ~ 100 nm rms Assumes instrument residual errors ~ 70 nm rms Equivalent Strehl from focal plane to detector/slit/IFU > 0.8 @ 1 micron Instruments must have: very high optical quality very low internal flexure l(mm) Delivered Strehl 1.25 0.2 ~ 0.4 1.65 0.4 ~ 0.6 2.20 0.6 ~ 0.8 Rigaut & Ellerbroek (2000) 9 Sodium laser constellation 4 tip/tilt stars (1 x 17, 3 x 20 Rmag) PSF variations < 1% across FOV

Modeled characteristics of a 30m GSMT with MCAO (AO only, l>3mm) and a 6.5m NGST Assumed encircled-energy diameter (mas) containing energy fraction h 30M 1.2mm 1.6mm 2.2mm 3.8mm 5.0mm 10mm 17mm 20mm (mas) 23 29 41 34 45 90 154 181 h 34% 47% 61% 50% 54% 56% 57% 58% NGST 1.2mm 1.6mm 2.2mm 3.8mm 5.0mm 10mm 17mm 20mm (mas) 100 100 82 138 182 363 617 726 h 70% 70% 50% 50% 50% 50% 50% 50% Assumed detector characteristics 1mm < l < 5.5mm 5.5mm < l < 25mm Id Nr qe Id Nr qe 0.01 e/s 4e 80% 10 e/s 30e 40%

Comparative performance of a 30m GSMT with a 6.5m NGST Assuming a detected S/N of 10 for NGST on a point source, with 4x1000s integration R = 10,000 R = 1,000 R = 5 advantage GSMT NGST advantage

Comparative performance of a 30m GSMT with a 4m NGST Assuming a detected S/N of 10 for NGST on a point source, with 4x1000s integration R = 10,000 R = 1,000 R = 5 advantage GSMT NGST advantage

Observations with high Signal/Noise, R>30,000 is a new regime - source flux shot noise becomes significant

High resolution, high Signal/Noise observations Detecting the molecular gas from gaps swept out by a Jupiter mass protoplanet, 1 AU from a 1 MO young star in Orion (500pc) (Carr & Najita 1998) GSMT observation ~ 40 mins (30 mas beam)

Conclusions NGST Comments X X X X X X X NGST advantage GSMT advantage X 6.5m 4.0m Comments 1. Camera 0.6 – 5 mm Deep imaging from space; consistent image quality, IR background, even for l < 2.5mm if D>4.0m 2. MOS R=1,000 1.2 – 2.5mm 2.5 – 5.0 mm NGST MOS still competitive for l < 2.5mm only if D~6.0m (consistent image quality, l coverage) 3. Spec. R=1500 5 – 28 mm Clear IR background advantage observing from space, even for D~4m and R< 30,000 4. IFU R=5,000 Detector noise limited for l < 2.5mm D2 advantage for groundbased GSMT For l >2.5mm, NGST wins even D~4m D2 advantage for groundbased GSMT For l <12mm AW advantage of GSMT,technology challenges from space (fibers) X NGST Instrument X X X X High S/N, R~100,000 spectroscopy WF MOS Spectroscopy l < 2.5mm X X