Transcript Future Giant Telescopes: Evolution in Ground-Space Synergy Richard Ellis Caltech Astrophysics 2020: STScI, November 13 2007

Future Giant Telescopes:
Evolution in Ground-Space Synergy
Richard Ellis
Caltech
Astrophysics 2020: STScI, November 13 2007
Ground-Space Synergy
(1990-2005)
NASA’s Great Observatories
~$2.5B investment in 8-10m telescopes
Synergistic attributes:
Space: unique wavelengths, angular resolution, reduced IR background, all-sky
Ground: photon-starved spectroscopy, panoramic fields, upgradable technologies
Synergistic Successes
HDF: HST
GRBs: Chandra/Swift
Transiting exoplanets: Spitzer
Some (of many) highlights of this partnership:
• charting the 2 < z < 6 Universe: redshifts, SFRs, morphologies & masses
• origin of various transients: short and long-duration GRBs, X-ray flashes
• physical properties of exoplanets
A Vision for Ground-Based Astronomy (1908)
"It is impossible to predict the dimensions
that reflectors will ultimately
attain. Atmospheric disturbances,
rather than mechanical or optical
difficulties, seem most likely to stand
in the way. But perhaps even these, by
some process now unknown, may at
last be swept aside. If so, the
astronomer will secure results far
surpassing his present expectations.”
George Ellery Hale, Study of Stellar Evolution, 1908 (p. 242)
writing about the future of the 100 inch.
Era of ELTs (2016 - )
A new generation of 20-42m ELTs is being designed:
TMT
• Thirty Meter Telescope (www.tmt.org)
- Caltech, UC, Canada + poss. Japan
- 30m f/1 primary via 492  1.4m segments
- $80M design underway (2004-2009)
- $760M construction cost (FY2006)
- major fund-raising already underway
GMT
• Giant Magellan Telescope (www.gmto.org)
- Carnegie, Harvard, Arizona, Texas,
Australia + others
- 21m f/0.7 primary via 6  8.2m segments
- funds for $50M design study being raised
• European ELT (www.eso.org/projects/e-elt)
- 42m f/1 primary with 900+ 1.4m segments
- 5 mirror design
- 57M Euros design underway (2007-)
How will these AO-designed ELTs
affect
ground-space synergy and space astronomy?
E-ELT
JWST vs 8m ground-based telescope
(1998)
Comparison of 8m JWST and AOfed 8m ground-based telescope:
Assuming:
• point sources
• AO (projected Strehl of 80% at K)
• Various OH suppression/detector
options
Space wins  > 2.2 m
Ground wins R>1000 1 < < 2.2m
All-Sky Adaptive Optics is Here!
Keck and Gemini Laser Guide Star Facilities
Performance of Keck NGS AO System
50% Strehl
R magnitude
r0 (cm)
Miranda+Uranus
Courtesy: Wizinowich & Keck AO team
Neptune
Titan
Performance of Keck LGS AO System
50% Strehl
NGS
LGS
r0 (cm)
Keck is
achieving ACS
resolution in K
band
Courtesy: Wizinowich & Keck AO team
R magnitude
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
HST Optical - Keck Near-IR Synergy
Resolved stellar populations in
HII regions in IC10
• ACS: I-band
• Keck AO + NIRC2:
H, K’ (Strehl ~30%)
• Self-calibration of AO
photometry using `curve of
growth’ technique (~few %
accuracy)
• Combined data enables direct
identification of AGB stars, C
stars, resolves WR complex
• Analysis reveals multiple bursts
of SF & accurate distance
Vacca, Sheehy & Graham Ap J 662, 272 (2007)
Recent Keck AO Highlights
Refereed Keck AO Science Papers by Year & Type
20.0
18.0
Number of
16.0
126 NGS & 30 LGS
Solar System
Galactic
Extra-galactic
14.0
12.0
10.0
8.0
6.0
4.0
Substellar binaries
2.0
0.0
2000
2001
2002
2003
2004
Year
2005
2006
2007
Next Generation AO on Existing 8-10m’s
•
•
•
NGS - seriously limited in sky coverage
LGS - modest Strehl due to `cone effect’
Next Steps:
– Multiple laser to defeat `cone effect’ LTAO
– Multi-DMs widen field with uniform
correction MCAO
– Independent correction of multi-objects in a
larger field MOAO
– Improved seeing over significant fields of
view GLAO
– High contrast planet finders ExAO
All under active development or implementation
Keck Next Generation AO
H
Ca
Triplet
NGAO
NGS
LGS
• Tomography overcomes `cone effect’
• AO-corrected, IR tip-tilt improves sky coverage
• Closed-loop for 1st relay; open-loop for deployable IFUs & 2nd relay
Courtesy: Wizinowich & Keck AO team
ESO VLT AO Program
• Hawk-I: 2012 + GLAO
– K-band imager, 7.5’ x 7.5’ field
Hawk-I
• MUSE visible multi-IFU + GLAO: 2012
– 1' field, x 2 seeing improvement
• MUSE visible narrow field IFU: 2012
– 7.5” field, ~10% Strehl at 750 nm
• SPHERE: 2010
– High Contrast Planet Finder
MUSE
Ground-Space Synergy ~ 2015
Ground-based 8-10m + NGAO: < 2.2 m
–
–
–
–
–
Masses/composition of KBOs and minor planets:
I-band AO
Debris disks and nearby planets:
high contrast JH, astrometry
Nearby AGN and Galactic center: astrometry,
spatially-resolved spectra at 8500 Å
Stellar populations in nearby galaxies: imaging
High-redshift galaxies: assembly history etc
multi-IFU spectroscopy in JHK
JWST: 2013: > 2.2 microns
–
–
Very high z sources, stellar masses
Star-forming regions etc
ALMA: 2012
–
–
Comparable resolution to AO (~ 10-100 mas)
Complementary data on dust & cold gas
Resolved Spectroscopy of High Redshift Galaxies
• Major driver for NGAO on 8-10m’s & future ELTs
using integral field units (single or multiple)
• Dynamical state, SF - density relations, assembly
histories etc
z=2.38
Genzel et al: VLT+Sinfoni
z=2.18
Law et al: Keck+LGSAO+OSIRIS
Gravitational Lensing + AO : A Preview of the Future
`Cosmic Eye’: a lensed z=3.07 Lyman break galaxy
HST/ACS image
Keck AO + OSIRIS
Keck/OSIRIS IFU + LGS (Sept 2007).
LGS delivers 75mas resolution
BUT: x25 magnification so this is effectively ~8 mas in source plane
Ground-based Synergy (2015-2025): TMT/JWST
TMT and other ELTs will offer
the combination of all NGAO
gains discussed earlier plus
that of increased aperture
and resolution
See http://www.tmt.org/foundation-docs/index.html
Giant Segmented Mirror
Telescope Science
Working Group Report
JWST:
- Full sky coverage
- 0.6-27 m wavelength range
- Superior imaging 1-2.2 m
- Stable diffraction limited > 2.2 m
- High dynamic range
ELT:
- 25 light grasp
- optical sensitivity with 15’ field
- 5 better angular resolution
- Superior R>3000 1-2.2 m
- High spectral resolution capability
- Upgradeable
WFE=170 nm (on axis) and < 2 mas image motion at first-light
Upgrading to WFE of 120 nm subsequently
Laser Guide Star Facility
An extrapolation of existing LGSF
architectures, designs, and components
–
–
–
–
CW solid-state lasers
Launch telescope behind TMT M2
Mirror-based beam transfer optics
Safety and control systems derived from
Gemini LGSF
Conceptual design review passed in
March 2006
Laser room sized for physical
dimensions of 3 current-generation
50W laser systems to produce 6 25W
beacons for NFIRAOS
Will monitor future development of
advanced components for potential
architecture upgrades
– Pulsed lasers
– Fiber optic beam relays
23
Resolved Absorption Line Spectroscopy
HDF-N
Peak
SB
Central SB
limit for vel.
dispersions
redshift
Resolved z>1 stellar work is demanding in photons - only possible with TMT!
2 arcmin field ok for clusters, 5 arcmin field necessary for field galaxies
Theorists’ View of Cosmic Reionization
Avi Loeb, Scientific
American 2006
But did it really happen like this..?
Probing Early Galaxies: Effect of Source Size
• How small are z~10 sources?
log F
(cgs)
JWST NIRSpec
• Strongly-lensed examples
have intrinsic sizes ~30mas!
• Gain of TMT+AO over JWST
in detection very significant
redshift
• Abell 2218 z~5.7 Ly emitter
• Magnification 30
• HST size 0.23  <0.15 arcsec
• Unlensed source is 30 mas
• Source is < 150pc in size!
TMT
TMT/JWST Complementarity
In the era of TMT+JWST we
probably won’t be interested in
when reionization occurred but
rather the physical process as
tracked by the topology and
structure of ionization bubbles
TMT gains in sensitivity, angular & spectral resolution but not field of view
JWST finds luminous sources, TMT scans vicinity to determine topology of
ionized shells via fainter emitters - in conjuction with HI surveys
Removing the
OH Forest: the
final obstacle
Courtesy: Bland-Hawthorn
Fiber Bragg Grating: Created Holographically
Courtesy: Bland-Hawthorn
First device
(Bland-Hawthorn et
al 2004)
FBG takes out 96% of
OH background by
suppressing 18
doublets over 70nm
Courtesy: Bland-Hawthorn
J
H
taper transition
Leon-Saval, Birks & JBH (2005),
Optics Letters
JBH et al (2007), Optics Express
Impact of Evolving Synergy
• Current role of space observatories:
- unique wavelength range
- reduced background
- angular resolution
• Angular resolution is increasingly a driver in astronomy
• ELTs + next generation AO will redefine the territory
• Practicality of OH suppression less clear but given
sufficient investment could offer great advantages
in 0.7 - 2.2 m range
• Unassailable advantages of space (in UVOIR range)
- panoramic imaging (AO always ineffective)
- optical and UV: very significant opportunities
• JWST does not provide these capabilities
Relevance to Science Themes of Workshop
• Resolved Stellar Populations
• Dark Sector Cosmology:
• First Light and Cosmic Reionization:
• AGN and Black Holes:
• Extrasolar Planets
Some key questions:
• Is there a case for a post-JWST large aperture space
telescope?
• Merits of the optical and UV
• Broader role for JDEM given its unique potential