1. 1 Comparative Performance of a 30m Groundbased GSMT and a 6.5m (and 4m) NGST NAS Committee of Astronomy & Astrophysics 9 th April 2001 Matt Mountain Gemini Observatory/AURA NIO

2. 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. 3 GSMT Science Case “The Origin of Structure in the Universe” From the Big Bang… to clusters, galaxies, stars and planets Najita et al (2000,2001)

4. 4 Mass Tomography of the Universe z~0.5 Existing Surveys + Sloan z~3 Hints of Structure at z=3 (small area) 100Mpc (5 O x5 O ), 27AB mag (L* z=9), dense sampling GSMT1.5 yr Gemini50 yr NGST140 yr

5. 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, 3  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. 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  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). S/N=100, R=100,000, >4  m Gemini out to 0.2pc sample ~10s GSMT 1.5kpc ~100s NGST X

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

8. 8 GSMT Control Concept LGSs provide full sky coverage Deformable M2 : First stage MCAO, wide field seeing improvement and M1 shape control 10-20’ field at 0.2-0.3” seeing 1-2’ field fed to the MCAO module  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). Focal plane Active M1 (0.1 ~ 1Hz) 619 segments on 91 rafts

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

10. 10 GSMT Implementation concept - wide field (2 of 2) 20 arc minute MOS on a 30m GSMT 800 0.75” fibers R=1,000 350nm – 650nm R=5,000 470nm – 530nm Detects 13% - 23% photons hitting 30m primary 1m Barden et al (2001)

11. 11 Spot Diagrams for Spectrograph R=1000 case with 540 l/mm grating. R=5000 case with 2250 l/mm grating. 350 nm440 nm500 nm560 nm650 nm 470 nm485 nm500 nm515 nm530 nm On-axis Circle is 85 microns equal to size of imaged fiber. Barden et al (2001)

12. 12 GSMT Implementation concept - MCAO/AO foci and instruments MCAO optics moves with telescope Narrow field AO or narrow field seeing limited port MCAO Imager at vertical Nasmyth elevation axis 4m Oschmann et al (2001)

13. 13 Spot diagrams for MCAO + Imager Diffraction limited performance for 1.2  m – 2.2  m can be achieved

14. 14 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)

15. 15 Quantifying the gains of NGST compared to a groundbased telescope Assumptions (Gillett & Mountain 1998) SNR = I s. t /N(t): t is restricted to 1,000s for NGST Assume moderate AO to calculate I s, I bg N(t) = (I s. t + I bg. t + n. I dc.t + n. N r 2 ) 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

16. 16 Space verses the Ground Takamiya (2001)

17. 17 Adaptive Optics enables groundbased telescopes to be competitive For background or sky noise limited observations: S  Telescope Diameter.   N Delivered Image Diameter   Where:   is the product of the system throughput and detector QE  is the instantaneous background flux

18. 18 Adaptive Optics works well

19. 19 Modeling verses Data 20 arcsec M15: PSF variations and stability measured as predicted GEMINI AO Data Model Results 2.5 arc min.

20. 20 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

21. 21 Tomographic calculations correctly estimated the measured atmospheric phase errors to an accuracy of 92% –better than classical AO –MCAO can be made to work Multi-Conjugate Adaptive Optics MCAO 2.5 arc min. Model results

22. 22 AO Technology constraints (50m telescope) r 0 (550 nm) = 10cm No. of Computer CCD pixel Actuator pitch S(550nm) S(1.65  m) actuators power rate/sensor (Gflops) (M pixel/s) 10cm 74% 97% 200,000 9 x 10 5 800 25cm 25% 86% 30,000 2 x 10 4 125 50cm 2% 61% 8,000 1,500 31 SOR (achieved) 789 ~ 2 4 x 4.5 Early 21 st Century technology will keep AO confined to > 1.0  m for telescopes with D ~ 30m – 50m

23. 23 MCAO on a 30m: summary MCAO on 30m telescopes should be used  m 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 (  m) 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 Rigaut & Ellerbroek (2000)

24. 24 Modeled characteristics of a 30m GSMT with MCAO (AO only,  m) and a 6.5m NGST Assumed detector characteristics  m <  m 5.5  m <  m I d N r q e I d N r q e 0.01 e/s 4e 80% 10 e/s 30e 40% Assumed encircled-energy diameter (mas) containing energy fraction  30M 1.2  m 1.6  m 2.2  m 3.8  m 5.0  m 10  m 17  m 20  m (mas) 23 29 41 34 45 90 154 181    Strehl 0.40 0.56 0.73 0.85 0.91] NGST 1.2  m 1.6  m 2.2  m 3.8  m 5.0  m 10  m 17  m 20  m (mas) 100 100 82 138 182 363 617 726 

25. 25 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 R = 10,000 R = 1,000 R = 5

26. 26 Comparative performance of a 30m GSMT with a 4m NGST R = 10,000 R = 1,000 R = 5 Assuming a detected S/N of 10 for NGST on a point source, with 4x1000s integration GSMT advantage NGST advantage

27. 27 Observations with high Signal/Noise, R>30,000 is a new regime - source flux shot noise becomes significant

28. 28 High resolution, high Signal/Noise observations Detecting the molecular gas from gaps swept out by a Jupiter mass protoplanet, 1 AU from a 1 M O young star in Orion (500pc) (Carr & Najita 1998) GSMT observation ~ 40 mins (30 mas beam)

29. 29 Conclusions 6.5m4.0m Comments 1.Camera 0.6 – 5  m Deep imaging from space; consistent image quality, IR background, even for  4.0m 2. MOS R=1,000 1.2 – 2.5  m 2.5 – 5.0  m NGST MOS still competitive for  < 2.5  m only if D~6.0m (consistent image quality,  coverage) 3. Camera Spec. R=1500 5 – 28  m Clear IR background advantage observing from space, even for D~4m and R< 30,000 4. IFU R=5,000 1.2 – 2.5  m 2.5 – 5.0  m Detector noise limited for  < 2.5  m D 2 advantage for groundbased GSMT For  >2.5  m, NGST wins even D~4m D 2 advantage for groundbased GSMT For  <12  m A  advantage of GSMT,technology challenges from space (fibers) NGST advantage GSMT advantage X X X X NGST NGST Instrument High S/N, R~100,000 spectroscopy WF MOS Spectroscopy  m XX XX