Plans for Extrasolar System Detection with the LBT Interferometer

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Plans for Extrasolar System Detection with the
LBT Interferometer

• Phil Hinz
• University of Arizona

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Acknowledgements

• Wilson Liu
• Ari Heinze
• Suresh Sivanandam

• Bill Hoffmann
• Roger Angel
• Matt Kenworthy
• Michael Meyer

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Why do we want to image giant planets and
zodiacal dust?

• Planets
• Extend radial velocity statistics
• Planets found by radial velocity measurements
  suggests a flat to rising separation distribution
• Look for long-period planets which could dominate
  the dynamical environments of planetary systems
• Before looking for a rocky planet we want to know
  which systems have stable habitable zones
• Learn about size, temperature, and composition of
  planets
• Most information about a planet can be obtained
  from direct detection.
• Zodiacal Dust Disks
• Disks are the smoking gun of a planetary system
• Material is cleared away on short timescales
  requiring large planetessimal bodies as
  reservoirs for transitory dust around mature
  stars.
• Resolving disks is crucial for understanding
  grain sizes and time scales
• Degeneracies between grain size and spatial
  distribution makes interpreting SEDs difficult.

Map out the architecture of other planetary
systems
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So whats the problem?
H M A Jupiter at 5 Gyr is 10-12
Lsun 10-8 Lsun A Jupiter at 0.5 Gyr is 10-8
Lsun 10-6 Lsun (Baraffe et al. 2003) Look
at younger systems! Look in the
infrared! Typical separations are 0.1-4
arcseconds for planets at 1-40 AU around stars
at 10 pc. Our Zodiacal Dust Disk is 10-4 Lsun at
11 microns
Requirements Approach Photometrically detect
planet/dust disk Large Infrared Optimized
Telescopes, Resolve planet from
star Interferometry or Large Telescopes Suppress
starlight Nulling, Adaptive Optics
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LBT Interferometric Imaging
The LBT combines good IR sensitivity with high
spatial resolution
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LBT Status

• First light with LBC prime focus camera achieved
  in October 2005
• Installed second primary in Fall 2005.
  Aluminized in January 2006
• Dual prime focus mode is planned for this summer.
• First Adaptive Secondary scheduled for delivery
  in summer 2008, second one six months later.

see http//lbto.org for latest pictures
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Interferometry with the LBT
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The LBTI-UBC Optical Design
deformable secondary
deformable secondary
f/15 telescope foci
beamcombiner
8.4 m LBT primary
14.4 m separation
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LBTI design

• Discrete cold dewars
• External Rigid Structure
• General Purpose (Universal) Beam Combiner (UBC)
• Three Camera Ports
• Nulling and Imaging Camera (NIC) is the only
  camera at the moment.
• Integrated Wavefront Sensors

UBC
Side Camera
Wavefront Sensors
NIC
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LBTI Parts
Parent Ellipse Mirror
vacuum bellows
rough cryostat housing
Mirror being polished
cryostat housing machined
center metering structure
metering structure edge-on
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LBTI Components
Fast Pathlength Corrector
4 K Mech. Cooler
SiC Mirror
Systems Engineer Tom Connors checks whether we
have left enough room for the binocular eyepiece
Left UBC Cryostat
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LBTI Structure in lab
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Optical Alignment Preparation
LBTI strongback as it would be seen from above
the LBT
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Fringes!
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LBTI-NIC requirements

• Four separate channels Wavelength Detector F
  OV
• Nulling 8-13 µm SiAs 256x256 7.7
• N band Fizeau 8-13 µm SiAs 256x256 7.7
• LM band Fizeau 3-5 µm HAWAII-1 10
• phase sensing channel 2-2.4 µm PICNIC 10
• Channels require separate intermediate focal and
  pupil planes for coronagraphy or nulling
  techniques.
• Require a reflective design for broadband (2-10
  µm) operations
• Split off NIR light after beam combination for
  phase control
• Require multiple dichroics in design to get right
  wavelength to right detector
• Each channel will be capable of low resolution
  (R100-300) spectroscopy

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NIC Optical Design
Side
Side View
In-Plane View
UBC focal Plane
N band Camera
DRS detector
Nulling Interferometer
HAWAII detector
L and M band Camera (LMIRCam)
Each channel uses a pair of aspheric toroidal
mirrors to form intermediate image and pupil
planes
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Nulling Channel
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N band imaging
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LMIRCam
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Phase Sensing
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LBTI Schedule
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LBT debris disk limits
see talk by Wilson Liu next week
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Comparison of Spitzer and nulling sensitivities
3000 zodies
300 zodies
30 zodies
3 zodies
Zodiacal dust model from Kelsall 1998 with 0.1
and 40 AU cutoffs
15 limit for Spitzer passbands
0.1 limit for nulling observations
0.01 limit for nulling observations
Colder dust is easier to see than warmer dust
with Spitzer. also Su et al. (2006) results
suggest inner debris disappears faster than outer
debris
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How to search for giant planets?
Model spectrum from Sudarsky, Burrows and Hubeny
(2003)
Theoretical models from Baraffe et al. 2003
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Observed L Exo-Jupiter limits to 1 Gyr star at 9
pc

• Observations of nearby old stars are sensitive to
  5-10 Jupiter masses

• Delta magnitude versus separation limits at L
  and M are comparable to NIR limits.

see SPIE papers by Heinze et al. (2006) and
Sivanandam et al. (2006)
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Improved Contrast with anApodizing Phase Plate

• Simple transmissive machined plate inserted in
  the pupil plane modifies suppresses the
  diffraction rings on one side.
• Technique is pointing invariant
• Contrasts of 11 magnitudes are achievable at
  separations of 0.5 arcsec (3 ?/D)

1.5
1.0
0.5
?m10.6
see ApJ paper by Kenworthy et al. (2007)
Initial results from Kenworthy, Codona, and
Mamajek
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LBTI Search Space
MMT/Clio
MMT/Clio with APP
LBTI
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Back Up Slides
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LBT compared to a single 8 m
14.4 m
10 mas/ µm
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Observations with the LBT over -3 HAto 3 HA
Dec20 deg
Dec0 deg
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Advantages of a Deformable Secondary

• IR observations are often limited by background
  light from the telescope optics.
• Typical AO systems have background emission of
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• A deformable secondary system can have an
  emissivity of 5-7.
• This can translate into 3-4x speed improvement in
  observations.

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The MMT AO System
AdaptiveSecondaryMirror
Send new position commands to the 336 actuators

• Measure aberrationsdue to the atmospherewith
  WFS Camera
• Calculate secondaryshape needed to
  correctmeasured aberration
• Apply shape to thedeformable secondary

Correct 56 modes
WFS Camera
Reconstructor Computer
Loop runat 550 Hz
12x12 Shack-Hartmann Sensor
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The Excitement of Ridin' the Hub
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AO in the mid-IR
Camera with cold pupil stop misaligned.
Camera with cold pupil stop aligned.
Blackbody emission From central hole in primary
Emission from sky
Emission from sky and telescope

• Images taken at 11 microns of the MMT adaptive
  secondary.
• Emissivity of the telescope was measured at 7.