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The Scientific Context for NGAO

Mark Morris, representing the NGAO Scientific Advisory Team (NSAT):

Tommaso Treu, Laird Close, Michael Liu, & Keith Matthews

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Context for NGAO – growing demand for LGS-AO on large telescopes

➜ the clear advantage of sky coverage.

Peer-reviewed publications:

Note the dominance of Keck, but other observatories are knocking hard on the door… 3

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Adaptive optics usage at WMKO has increased dramatically over thepast decade, and is still rising …

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All major research communities are employing LGS AO …

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Total LGS

Solar Sys

Galactic

Extra-galactic

2010to date:6 months

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Key Science Cases – Requirements Drivers

1. High-redshift galaxies, internal structure and dynamics at z = 1 – 3

2. Black hole masses in nearby AGNs: resolving the Keplerian velocity increase within the black holes’ sphere of influence

3. General Relativity at the Galactic center: precision stellar orbits to discover and measure post-Newtonian effects.

4. Planetary companions to low-mass stars & brown dwarfs: taking advantage of the favorable contrast, & using a coronagraph

5. Asteroid and KBO companions: size, shape, composition & orbits of companions to minor planets with the aim of reconstructing their history

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These push limits of AO system, instrument, and telescope. Determine the most demanding performance requirements.These push limits of AO system, instrument, and telescope. Determine the most demanding performance requirements.

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Simulation of radial velocities observed along the major axis of an emission-line disk surrounding a black hole in a galaxy center.

Observational Attributes:

near-diffraction limited performance in the near-IR (K Strehl ~80%). On Keck, this provides the highest spatial resolution available at any of its operating wavelengths. Very high Strehl key enabler of the science envisioned with NGAO.

substantially increased sky coverage, compared to existing AO systems

AO corrections at wavelengths as short as 7000 Å

imaging with a reconstructable and only moderately variable PSF over the entire science field (~20”) photometry, astrometry, deconvolution

integral field spectroscopy at R~4000 from 0.7 to 2.4 µm, with three pixel scales: 10, 35, and 50 (or 70) mas, with 5.6” x 3” FOV at 50 mas sampling. - AO-fed medium-resolution NIR IFS unique among AO systems under development.

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Calciumtriplet

850 nm

How is NGAO different from How is NGAO different from Keck’s AO today?Keck’s AO today?

• NGAO: same Strehl at Ca Triplet as LGS today in H band

• NGAO: better Strehl at J band than LGS today in K band

• NGAO: much higher sky coverage

• NGAO: same Strehl at Ca Triplet as LGS today in H band

• NGAO: better Strehl at J band than LGS today in K band

• NGAO: much higher sky coverage

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-=- Sky coverage -=-Many science cases, particularly extragalactic ones Many science cases, particularly extragalactic ones such as Galaxy Assembly and Star Formation such as Galaxy Assembly and Star Formation History are strongly affected by NGAO’s sky History are strongly affected by NGAO’s sky coverage coverage

• Need to look at random places in the sky

• Out of the plane of the Galaxy

• In select “Deep Fields” that were chosen by others to have very few stars

• Need to accumulate a good statistical sample of galaxies in order to draw conclusions

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MOAO correction of IR tip-tilt stars has large benefit for sky coverage

• Example: Keck NGAO, galaxy assembly science case, zenith angle 30 deg, median seeing at Mauna Kea

Current Keck TT

Current Keck EE 50 NGAO TT

NGAO EE 50

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NGAO: dramatic improvements in SNR NGAO: dramatic improvements in SNR for IFU spectra of distant galaxiesfor IFU spectra of distant galaxies

• Cooled AO system to reduce thermal background (K-band)

• Increased instrument throughput (34% vs. 19%)

• Higher spatial resolution means better point source sensitivity

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Antennae GalaxiesLocal Himage

LGS AO z =2.5

NGAO z = 2.5

SNR in H

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Advantages of NGAO for Advantages of NGAO for Resolved Stellar PopulationsResolved Stellar Populations

1. Reduced confusion from halos of adjacent stars: means better photometry on more stars

2. Color magnitude diagrams give better discrimination using I – K colors than using J – K or H – K colors (next slides)

3. Improved astrometry lets you better determine cluster membership (next slides)

Olsen Blum and Rigaut 2003GSMT simulation of NGC 1835

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Resolved Stellar PopulationsResolved Stellar Populations

Visible-light AO = better discrimination between stellar populations due to longer lever-arm of I-K vs. J-K for color-magnitude diagrams.

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Four Major Wide Field AO Systems Four Major Wide Field AO Systems are under Developmentare under Development

Tradeoffs: spatial resolution, strehl, PSF uniformity 17

NGAO Will Be the Leader in NGAO Will Be the Leader in High Performance Narrow Field AOHigh Performance Narrow Field AO

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contrast, Strehl, skycoverage

NGAO more robust

A broad array of other investigations is enabled by NGAO, some of which have been used as additional science drivers

Gravitationally lensed galaxies QSO host galaxies Circumnuclear disks in galaxies Extended gaseous structures at high redshifts Resolved stellar populations in extragalactic systems The internal dynamics of star clusters, young and old Debris disks Young stellar objects, protostellar disks, & jets Stellar winds: bubbles, bow shocks, & pinwheels Planetary & preplanetary nebulae – launching of bipolar flows Jovian planet atmospheres: climate and wind dynamics Planetary rings, satellites, and their interactions

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So far, 40 astronomers have helpedSo far, 40 astronomers have helpeddevelop the NGAO Science Casesdevelop the NGAO Science Cases

• Ádámkovics, Mate • Ammons, Mark• Auger, Matt • Barth, Aaron • Bouchez, Antonin • Cameron, Brian* Close, Laird• de Pater, Imke• Eisner, Joshua• Emery, Joshua• Fassnacht, Chris • Ghez, Andrea • Greene, Tom• Hammel, Heidi• Hillenbrand, Lynne• Jonsson, Patrik • Koo, David• Larkin, James• Law, David• Liu, Michael

• Lu, Jessica• Macintosh, Bruce • Marchis, Franck• Marshall, Phil* Matthews, Keith• Max, Claire• McGrath, Liz• Melbourne, Jason• Melling, Laura• Metchev, Stanimir * Morris, Mark* Nierenberg, Anna• Noll, Keith • Novak, Greg• Olsen, Knut• Steidel, Chuck• Suyu, Sherry* Treu, Tommaso• Vegetti, Simona• Weinberg, Nevin

* Current NSAT

Members

New science cases from other scientistsare always welcome

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Competitive Landscape: JWSTCompetitive Landscape: JWST

• JWST advantages

– JWST will have better sensitivity than NGAO (low backgrounds) at K band, but lower at J

– Diffraction limited imaging between 2.4 and 5 m

– Multiplexed slit spectroscopy (x 100)

– Spectral resolution R = 2700

• Keck NGAO advantages

– Better spatial resolution than JWST at wavelengths below 2 m

JWST pixels under-sample the diffraction limit at wavelengths shorter than 2 m

– Spectroscopy at spatial resolutions < 0.1”

– Spectroscopy at spectral resolutions R > 2700

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NGAO complementarity to TMTNGAO complementarity to TMT

• Technology groundbreaking for NFIRAOS

• In TMT era, Keck NGAO can play key role inscreening targets for follow-up with scarce TMT time

• TMT advantages

– Higher spatial resolution

– Higher sensitivity

– Wide field with partial correction (IRMS)

• Keck NGAO advantages

– Higher sky coverage (LGS AO corrected tip-tilt stars)

– Half-decade head start

– Synoptic studies

– More CIT & UC community access for NGAO

• For AGN black hole mass measurements, NGAO using Ca II triplet is comparable with TMT in K band (CO bandhead).

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Summary

NGAO’s very high Strehl over a substantial field of view, coupled with a dramatic improvement in sky coverage, would bring considerable scientific return, and enable both major progress in existing investigations as well as new kinds of scientific investigations.

All areas of astronomy would profit from this capability; the number of significant science cases so far indicates that the demand for this capability will be enduring, even into the era of JWST and TMT.