Overview

1. Comparative Performance of a 30m Groundbased GSMT and a 6.5m (and 4m) NGSTNAS Committee of Astronomy & Astrophysics9th April 2001Matt MountainGemini Observatory/AURA NIO

2. Overview • Science Drivers for a GSMT • Performance Assumptions • 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

3. 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

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

5. 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

6. 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).

7. 30mGiant Segmented Mirror Telescope concept GEMINI 30m F/1 primary, 2m adaptive secondary

8. GSMT Control Concept LGSs provide full sky coverage Deformable M2 : First stage MCAO, wide field seeing improvement and M1 shape control • 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

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

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

11. 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)

12. 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)1/2and 10% of the pixels are lost Source noise background dark-current read-noise

13. Space verses the Ground Takamiya (2001)

14. 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

15. Adaptive Optics works well

16. 20 arcsec Modeling verses Data GEMINI AO Data 2.5 arc min. Model Results M15: PSF variations and stability measured as predicted

17. 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

18. 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

19. 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 31SOR (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

20. 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 Rigaut & Ellerbroek (2000) l(mm) Delivered Strehl 1.25 0.2 ~ 0.4 1.65 0.4 ~ 0.6 2.20 0.6 ~ 0.8 9 Sodium laser constellation 4 tip/tilt stars (1 x 17, 3 x 20 Rmag)PSF variations < 1% across FOV

21. 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 17mm20mm (mas) 23 29 41 34 45 90 154 181 h 34% 47% 61% 50% 54% 56% 57% 58% NGST1.2mm 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%

22. R = 10,000 R = 1,000 R = 5 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 GSMT advantage NGST advantage

23. R = 10,000 R = 1,000 R = 5 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 GSMT advantage NGST advantage

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

25. 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)

26. Conclusions NGST advantage NGST GSMT advantageX X NGST Instrument X X X X High S/N, R~100,000 spectroscopy WF MOS Spectroscopy l < 2.5mm X X