Transcript Nelson

Science Goals and AO for the TMT
Jerry Nelson
University of California at Santa Cruz
Adaptive Optics for Extremely Large Telescopes
Paris, 2009June23
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Outline
Project Introduction
Telescope overview
Science-based metrics
TMT key features
Major science goals
Science Instruments
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Project Introduction
Time line
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2004
2009
2011
2018
project start, design development
preconstruction phase
start construction
complete, first light, start AO science
Partnership
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UC
Caltech
Canada
Japan
NSF?
Others?
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Telescope Overview
LGSF launch telescope
M2 support tripod
M2 structural hexapod
Tensional members
LGSF beam transfer
M2 hexagonal ring
M2 support columns
Elevation journal
Nasmyth
platform
Laser room
Azimuth cradle
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M1 cell
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Azimuth truss
TMT Optical Design:
Ritchey Chrétien
M1 Parameters
– ø30m, f/1, Hyperboloid
k = -1.000953
– Paraxial RoC = 60.0m
– Sag = 1.8m
– Asphericity = 29.3mm (entire M1)
M2 Parameters
– ø3.1m, ~f/1, Convex hyperboloid,
k = -1.31823
– Paraxial RoC = -6.228m
– Sag = ~650mm
– Aspheric departure: 850 mm
M3 Parameters
– Flat
– Elliptical, 2.5 X 3.5m TMT.PSC.PRE.09.031.REL01
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Segment Size
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Primary Mirror Control System (M1CS)
The M1CS, with the Alignment and Phasing System, turn the 492
individual segments into the equivalent of a monolithic 30 meter
diameter mirror.
TMT control strategy is an evolutionary improvement on the
successful strategy used at the two Keck Telescopes.
SSA prototype with dummy segment
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M1CS Overview
M1CS maintains the overall shape of the primary mirror
– Attenuates gravity, temperature, wind, and vibration disturbances
The primary mirror is aligned and phased using the Alignment and Phasing
System (APS) every 4 weeks or after a segment exchange.
– Look up tables are used in between calibration runs
M1CS controls the global shape of the M1 using segment-mounted edge
sensors and actuators
Real time “On-instrument Wavefront Sensors” (OIWFS) measurements or AO
system offloads will augment the static look up tables built using APS data
M1 surface error from
wind disturbance
M1CS off: 223 nm RMS
M1CS on: 14 nm RMS
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Science-based Metrics
We use the time needed to make an observation as our
metric
– Generally assume that we are observing point sources
– Generally assume the sources are background limited (most
photons come from background, rather than source)
– In detail this is based on King’s paper that shows
point source sensitivity (PSS)
~ 1/equivalent noise area
For these assumptions we get

PSS ~
~
 PSF ()d
2
1
area * throughput
~
t (background /solid angle ) * (image solid angle )
This is true for seeing-limited or diffraction-limited
observations

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Science Merit Function
For seeing-limited observations
– PSS ~ D2/image diameter2
For diffraction-limited observations
– image solid angle varies as 1/area, so we get the well known
PSS~D4 rule
– For finite Strehl, the signal strength is reduced by S, but the
background is not reduced, so one gets PSS~S2 where
 2
Strehl  S  e
and  is the wavefront error in radians

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Reflectivity, emissivity, throughput
Clearly we want the highest possible reflectivity of our
optics
– Obvious, since PSS ~ throughput
– In the visible r ~ 0.9, so for 3 mirrors, net throughput ~ 0.73
– But, as important, thermal emission from the warm optics can
increase the IR background, particularly in K band
– When the IR sky is dark (between OH lines) the telescope
emission can be the dominant background source
– Background ~ (# warm mirrors)*(1-reflectivity)
So it can be VERY important to minimize the number of
warm mirrors between the target and the IR instrument
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Blackbody Flux vs wavelength (various T's)
Photons/s/arcsec2/µm/TMT
1.E+09
5°C
0°C
-5°C
-10°C
-15°C
-20°C
-25°C
1.E+08
1.E+07
1.E+06
1.5
1.7
1.9
2.1
2.3
2.5
Wavelength (µm)
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Thermal backgrounds
Previous graph shows the blackbody flux
Cooling the optic by ~ 30° reduces the flux in this wavelength region
by a factor of ~ 15
Below ~ 2µm the flux is lower than natural backgrounds
These fluxes are multiplied by the mirror emissivities and the
number of mirrors
Observatory created backgrounds
– Three ambient temperature telescope mirrors (M1, M2, M3)
– NFIRAOS science path
1 ambient window
5 cold mirrors
1 cold beam splitter
1 cold window
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K band thermal background
In the near IR, only K band will see significant thermal
flux from telescope
Telescope
– 3 mirrors at 1.5% emissivity each
– Segment gaps 0.5%
– Net background ~ 0.05*ambient blackbody flux
NFIRAOS
– Net throughput 85%, so emissivity ~ 0.15
– Cooling 30° reduces flux by a factor of ~ 15, so
– Net added background ~ 0.01*ambient blackbody flux
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Field of View
For many science programs larger field of view is useful
– Multiple targets
– Complex targets (galaxies, etc)
– Astrometry where reference objects are needed
Seeing-limited unvignetted 15 arcmin FoV
Atmospheric angular anisoplanatism limits the
correctable field of view for AO
– One must measure the atmosphere over a sufficient volume to
know what the angle dependent correction needs to be
– With lasers, one must do tomography to get this information
– One must have multiple deformable mirrors to make the added
correction
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Impact of multiple deformable mirrors
More DM’s allow greater 3-d fidelity of atmospheric
correction, improving correction over larger field of view
Strehl Ratio
Off axis angle (arcsec)
Wavelength
0”
6”
12”
18”
J 1 DM
0.56
0.42
0.21
0.07
J 2 DM
0.60
0.60
0.58
0.51
H 1 DM
0.72
0.61
0.40
0.21
H 2 DM
0.75
0.75
0.73
0.70
K 1 DM
0.83
0.75
0.60
0.41
K 2 DM
0.85
0.85
0.84
0.81
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TMT design path
30m diameter telescope
High reflectivity optics
Only 3 reflections to science instruments or NFIRAOS
NFIRAOS cooled by 30° to reduce thermal emission
NFIRAOS is initial AO system and can feed 3 inst
For AO, two DM’s for increased field of view
For AO, large sky coverage enabled by using 3 partially
corrected natural stars (focus, tip, tilt) with 6 LGS
15 arcmin unvignetted field of view for seeing-limited
All instruments always available in < 10 minutes
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Nasmyth Configuration:
First Decade Instrument Suite
/IRMS
TMT GCAR, April 2009
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NFIRAOS MCAO has better
performance than current systems
Dual conjugate AO system
– Order 61x61 DM and TTS at h=0 km
– Order 75x75 DM at h=12 km
– Better Strehl than current AO systems
(e.g., Keck ~280-300nm WFE)
Band
SRD (120 nm)
R
I
Z
J
H
K
0.313
0.411
0.566
0.674
0.801
0.889
Strehl Ratio
Baseline (177
nm)
0.080
0.145
0.290
0.424
0.617
0.774
Baseline + TT
(WIRC)
IRMS
(NIRES)
0.052
0.105
0.236
0.366
0.569
0.742
NFIRAOS
IRIS
Completely integrated system
Fast (<5 min) switch between targets
>50% sky coverage at galactic poles
(w/<2mas TT error)
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TMT: Key Science
•
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•
•
•
•
Nature and composition of the Universe
Formation of the first stars and galaxies
Evolution of galaxies and the intergalactic medium
Relationship between black holes and their galaxies
Formation of stars and planets
Nature of extra-solar planets
Presence of life elsewhere in the Universe
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Science Drivers for large O/IR Telescopes:
3 Basic Types
Science that you know you want to do now, but have discovered to be out of
reach through experience on 8-10m telescopes.
– These tend to be what is written in “design reference mission” or “science case”
documents
Solving problems we do not even know about yet
– Thinking about “capability space”, or “discovery space”, rather than specific
science cases
– Some intuition is necessary- where will the surprises be, what will we need to
follow them up?
Supporting roles and “complementarity” with other facilities on ground, in
space.
– Harder to make such roles sound exciting/compelling… BUT next-generation
O/IR telescopes will play key role in supporting ALMA, JWST, CCAT, LSST, IXO
(CON-X), ZEUS, etc.
– While many other facilities may not publicly admit that they “need” large O/IR
telescopes on the ground (for the same reason), in fact, history suggests that
they will.
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TMT Detailed Science Case
•~100 page summary of TMT
science case (David Silva,
editor), completed and posted
publicly in October 2007.
(http://tmt.org)
•Developed with AURA/NOAO
as full partner (US community
interests accounted for).
•Includes science cases
developed by instrument
feasibility study teams
•From fundamental physics
and cosmology, to galaxy and
structure formation, to extrasolar planets, to solar system
studies.
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Key TMT features for Science
30m, f/1 primary, RC telescope, ~20’ field
– 30-m is a judgment about the proper balance between science benefit, cost,
technological readiness, and schedule
Filled aperture, 492 1.44m segments
– produces a more concentrated point spread function (PSF), improving signalto-noise ratios and easing data analysis
Integrated AO systems, including Laser Guide Star (LGS) facility
– MCAO, MOAO, GLAO, MIRAO, ExAO
– Sensitivity: D4 advantage for background-limited point sources with AO
Wavelength range: 0.31 - 28 microns (entire UV-mid-IR)
Spatial resolution: 0.007” at 1 micron, 0.014” at 2 microns
Instruments on large Nasmyth platforms, addressed by articulated tertiary
– Rapid switching between targets with different instruments (< 10 min)
– (Rapid target acquisition: time between targets < 5 min)
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SAC Instrument Prioritization
Desire to fund first-light instrument suite out of cost-capped construction
budget
Discovery space: largest gains in broadest range of science in the near-IR
(0.8-2.5 microns)@diffraction limit
– IRIS: IFU+diffraction limited imager
– IRMS: multiplexed faint object spectroscopy in the near-IR -- leverages investment
in facility MCAO system.
Ability to perform guaranteed high-priority science we can think of now
– WFOS
– PFI very focused, but very powerful (GPI as a pathfinder...)
– HROS workhorse capability, strong science case
Raw gains in sensitivity (D4) over existing or planned facilities, well defined
science
– MIRES (mid-IR echelle)
– NIRES (near-IR echelle)
– WIRC (wider field diff. limited imager)
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TMT First Decade Instrument/Capability Suite
Instrument
Near-IR DL Spectrometer &
Imager
(IRIS)
Spectral
Resolution
~4000
Wide-field Optical
Spectrometer
(WFOS)
1000-5000
Multi-slit near-DL near-IR
Spectrometer
(IRMS)
2000 - 5000
Mid-IR Echelle
Spectrometer & Imager
(MIRES)
5000 - 100000
ExAO I
(PFI)
50 - 300
High Resolution Optical
Spectrograph
(HROS)
30000 - 50000
MCAO imager
(WIRC)
5 - 100
Near-IR, DL Echelle
(NIRES)
Science Case
Assembly of galaxies at large redshift
Black holes/AGN/Galactic Center
Resolved stellar populations in crowded fields
Astrometry
IGM structure and composition 2<z<6
High-quality spectra of z>1.5 galaxies suitable for measuring stellar
pops, chemistry, energetics
Near-field cosmology
Near-IR spectroscopic diagnostics of the faintest objects
JWST follow-up
Physical structure and kinematics of protostellar envelopes
Physical diagnostics of circumstellar/protoplanetary disks: where and
when planets form during the accretion phase
Direct detection and spectroscopic characterization of extra-solar
planets
Stellar abundance studies throughout the Local Group
ISM abundances/kinematics, IGM characterization to z~6
Extra-solar planets!
Precision astrometry
Stellar populations to 10Mpc
Precision radial velocities of M-stars and detection of low-mass planets
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5000 - 30000
IGM characterizations for z>5.5
TMT Early Light Instrument Suite
Instrument
Near-IR DL Spectrometer
& Imager
(IRIS)
Spectral
Resolution
~4000
Science Case
Assembly of galaxies at large redshift
Black holes/AGN/Galactic Center
Resolved stellar populations in crowded fields
Astrometry
Wide-field Optical
Spectrometer
(WFOS)
1000-5000
IGM structure and composition 2<z<6
High-quality spectra of z>1.5 galaxies suitable for measuring
stellar pops, chemistry, energetics
Near-field cosmology
Multi-slit near-DL near-IR
Spectrometer
(IRMS)
2000 - 5000
Near-IR spectroscopic diagnostics of the faintest objects
JWST followup
Mid-IR Echelle
Spectrometer & Imager
(MIRES)
5000 100000
Physical structure and kinematics of protostellar envelopes
Physical diagnostics of circumstellar/protoplanetary disks: where
and when planets form during the accretion phase
ExAO I
(PFI)
50 - 300
Direct detection and spectroscopic characterization of extra-solar
planets
High Resolution Optical
Spectrograph
(HROS)
30000 50000
MCAO imager
(WIRC)
Stellar abundance studies throughout the Local Group
ISM abundances/kinematics, IGM characterization to z~6
Extra-solar planets!
Galactic center astrometry
5 - 100 TMT.PSC.PRE.09.031.REL01
Stellar populations to 10Mpc
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Precision radial velocities of M-stars and detection of low-mass
TMT Science and “Flow-down”
Requirements for early light capabilities have been finetuned as a balance between unfettered science-driven
desires and technical/fiscal realities (SAC/Project
interactions have been crucial).
We are proposing to build the most powerful suite of
capabilities we can, through close interaction between
science and engineering.
Currently-envisioned capabilities address a huge range
of questions we can formulate now (and complement
other powerful facilities)
The same capabilities will make new discoveries and will
be the primary diagnostic tool for making sense of the
discoveries made elsewhere.
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IRIS Conceptual Design Team
James Larkin (UCLA), PI, Lenslet IFS
Anna Moore (Caltech), co-I, Slicer IFS
Ryuji Suzuki, Masahiro Konishi, Tomonori Usuda (NAOJ), Imager
Betsy Barton (UC Irvine), Project Scientist
Science Team
–
Mate Adamkovics(UCB), Aaron Barth(UCI), Josh Bloom(UCB), Pat Cote(HIA),
Tim Davidge(HIA), Andrea Ghez(UCLA), Miwa Goto(MPIA), James
Graham(UCB), Shri Kulkarni(Caltech), David Law(UCLA), Jessica
Lu(UCLA),Hajime Sugai(Kyoto U), Jonathan Tan(UF), Shelley Wright(UCI)
OIWFS (On Instrument Wavefront Sensor) Team (HIA + Caltech)
– Led by David Loop, Anna Moore
NSCU (NFIRAOS Science Calibration Unit) Team (U of Toronto)
– Led by Dae-Sik Moon
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Motivation for IRIS
Should be the most sensitive astronomical IR spectrograph ever built
Unprecedented ability to investigate objects on small scales.
0.01” @
5 AU
5 pc
100 pc
1 kpc
8.5 kpc
1 Mpc
20 Mpc
z=0.5
z=1.0
z=2.5
z=5.0
Titan with an overlayed 0.05’’
grid (~300 km) (Macintosh et al.)
= 36 km
= 0.05 AU
= 1 AU
= 10 AU
= 85 AU
= 0.05 pc
= 1 pc
= 0.07 kpc
= 0.09 kpc
= 0.09 kpc
= 0.07 kpc
(Jovian’s and moons)
(Nearby stars – companions)
(Nearest star forming regions)
(Typical Galactic Objects)
(Galactic Center or Bulge)
(Nearest galaxies)
(Virgo Cluster)
(galaxies at solar formation epoch)
(disk evolution, drop in SFR)
(QSO epoch, Ha in K band)
(protogalaxies, QSOs, reionization)
M31 Bulge with 0.1” grid (Graham et al.)
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Keck AO images
29 are
High redshift galaxy. Pixels
0.04” scale (0.35 kpc).Barczys et al.)
WFOS/MOBIE Team
Rebecca Bernstein (UCSC), PI
Bruce Bigelow (UCSC), PM
Chuck Steidel (Caltech), PS
Science Team: Bob Abraham(U Toronto), Jarle Brinchmann(Leiden), Judy
Cohen(Caltech), Sandy Faber(UCSC), Raja Guhathakurta(UCSC), Jason Kalirai(UCSC),
Gerry Lupino(UH), Jason Prochaska(UCSC), Connie Rockosi(UCSC), Alice
Shapley(UCLA)
Some “flagship” science cases, “work horse capability”
– High quality spectra of faint galaxies/AGN/stars
– IGM tomography
Great “follow-up” and “discovery” potential - full wavelength coverage with
spectral resolutions up to R = 8000
– JWST, ALMA, etc., follow-up
Sensitivity >14 x current 8m telescopes
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IR Multi-Slit Spectrometer
(IRMS)
IRMOS (deployable MOAO IFUs) deemed too risky/expensive for first light
=> IRMS: clone of Keck MOSFIRE, first step towards IRMOS
– Multi-slit NIR imaging spectro:
– 46 slits,W: 160+ mas, L: 2.5”
– Deployed behind NFIRAOS
2’ field
60mas pixels
EE good (80% in K over 30”)
– Spectral resolution up to 5000
– Full Y, J, H, K spectra (one at a time)
Slit width
Images entire 2’ field
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Whole 120” field
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IRMS Spectra
Configurable Slit Unit originally developed for JWST (slits formed by opposing bars)
Full Y, J, H, K spectra with R ~ 5000 with 160mas (2 pix) slits in central ~1/3 of field
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Summary
TMT will be a 30-m telescope with AO capabilities from
the start
– ~ 190 nm rms wavefront error over 10 arcsec
– First light 2018
Very large and exciting science case
8 instruments planned for the first decade
3 instruments planned for first light
– IRIS (an AO NIR integral field spectrograph and imager)
– IRMS (an AO NIR multi object spectrometer (46 slits)
– WFOS (a seeing-limited multiobject spectrometer with R<8000,
and ~ 50 arcmin2coverage)
Many papers will elaborate on TMT AO in this conference
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