AIRS: The Antarctic Infrared Survey

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AIRS The Antarctic Infrared Survey

• James M. Jackson
• Institute for Astrophysical Research
• Boston University

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Collaborators

• Boston University
• Dan Clemens
• Eric Tollestrup
• Thomas Bania

• Lowell Observatory
• Robert Millis
• Ted Dunham
• Marc Bruie

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Our Local UniverseKey Astrophysical Questions

• Earliest stages of planet formation
• Nature and number of brown dwarfs
• Earliest stages of star formation

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Key Science is Uniquely Addressed by Thermal
Infrared Observations

• Wavelengths of 3 to 30 mm correspond to
  black-body temperatures of 100 to 1000 K
• Infrared emission probes cooler objects
• Protoplanetary disks
• Brown dwarfs
• Star forming regions

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RCW 38
Another essential advantage Infrared penetrates
dust clouds
(M. Petr 2000)
VLT-FORS optical
VLT-ISAAC infrared (JHK)
Lada 2002
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Why Antarctica for infrared studies?Its COLD!

• Reduced infrared thermal background
• Telescopes and atmosphere emit in the thermal
  infrared
• Antarctic mean temperature 50 C
• IR backgrounds typically 20 to 100 times smaller
  than at temperate sites
• Excellent sensitivity

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Greatly Reduced Infrared Sky Brightness
The sky background is 20 100 times smaller at
the South Pole compared with Mauna Kea
Phillips et al. 1999
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Wide-field infrared surveys are essential to
study the local Universe 2MASS
2MASS 2mm
optical
www.ipac.caltech.edu/2mass
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Wide-Field Infrared Imaging Surveying Large
Areas

• Discover huge numbers of new objects for
  follow-up by larger telescopes or interferometers
• Obtain statistically significant samples
• BUT 2MASS still suffers from extinction
• Longer wavelengths penetrate dust better
• There are no large-scale
  3 mm lt l lt 5 mm surveys

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The Antarctic Infrared Survey

• The next generation Antarctic IR telescope
• 2 meter aperture
• 2-5 mm wide-field imaging camera
• Essential step in eventual development of large
  (15 m) Antarctic IR telescopes and multi-element
  interferometers

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The Antarctic Infrared Survey

• Simultaneous K and L band survey
• 8,000 square degrees (d lt -38o)
• Same sensitivity at L-band as 2MASS at K-band (5s
  limiting magnitude of 15.0)
• Detect all 2MASS objects with flat colors
• Discover hundreds of thousands of redder objects

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Formation of Planets Protoplanetary Disks

• Dusty disks have temperatures perfectly matched
  to the thermal infrared.
• Their presence can be inferred from excess IR
  emission.

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Identifying protoplanetary disks with L band
excess
L-band SPIREX data
redder
redder
Disks manifest themselves as excess L-band
emission (Kenyon Gomez 2001)
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L and T Dwarfs

• Coolest stars and brown dwarfs are called L and
  T dwarfs
• Boundary between stars and brown dwarfs is 0.07
  solar masses

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IR color vs. stellar typereddest objects are
brown dwarfs
Cooler (lower mass)
Redder
Brown dwarfs
Burgasser 2002
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AIRS can detect much more distant brown dwarfs
than 2MASS
N R3
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How many L and T dwarfs will the Antarctic
Infrared Survey detect?

• AIRS will reach Llim15.0, Klim 19.4 mag (tint
  9 minutes)
• Survey 8,000 square degrees
• L dwarfs
• K-band detections 350,000
• L-band detections 3,000 to 6,000
• Increase known sample by factor of 30
• T dwarfs
• K and L band detections 16 to 32
• Increase known sample by factor of 2

Kirkpatrick et al. 1999 Burgasser 2001
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Massive Star FormationNGC 6334
SPIREX/Abu image Blue PAH feature (UV
irradiated dust) Red Brackett a (ionized
gas) Green L band continuum (warm dust) Burton
et al. 2000
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Burton et al. 2000
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Star-forming Regions 30 Doradus
SPIREX/Abu data Blue J, Green K, Red L Deeply
embedded stars show as red. L-band detects
deeply embedded YSOs undetected at K-band. This
is the worlds most sensitive ground-based
L-band image (19 mag) taken with only a 60 cm
telescope!
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Temporal Variability

• Brown dwarfs
• Rotation rates, weather
• Evolved red supergiants (Mira variables)
• High mass, long period Miras are invisible at l lt
  3 mm
• Gravitational microlensing by planets
• IR removes degeneracy between impact parameter
  and planetary mass
• Comets
• Rotation rate known for 12 comets

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AIRS Scientific Goal

• To survey the sky in the thermal infrared in
  order to significantly increase the known samples
  of protoplanetary disks, brown dwarfs, and young
  stellar objects

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AIRS Technical Requirements

• Achieve comparable sensitivity to 2MASS (2 mm)
• AIRS will detect every object with flat IR color
  that 2MASS did.
• AIRS will detect a large number of new, redder
  objects that 2MASS did not.
• L-band sensitivity of 14.3 magnitudes in 10
  minutes
• Simultaneous 2 color imaging L and K
• Large instantaneous field of view

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Telescope Design

• Cassegrain
• 2 meter primary
• f/1.6
• 0.6 m secondary
• 9.6 blockage
• 42 arcmin field of view
• Plate scale 58.18 mm/arcsec

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AIRCAM Camera Design
AIRCAM CONCEPT
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Camera

• Simultaneous L and K band imaging
• Registration
• Cross-calibration with 2MASS
• 2048 x 2048 InSb array for L and M bands
• 1024 x 1024 HgCdTe array for K band

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Expected Optical Performance Strehl Ratio vs.
Field of View
Diffraction-limited performance out to edges of
20x20 arcmin AIRCAM field of view
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Expected Optical PerformanceEncircled Energy
vs. radial offset
Diffraction-limited subarcsec performance across
all bands for the entire 20x20 arcmin field of
view.
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Sensitivity S/N of 5 in 9 minutes
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Mapping Times K 19.4, L 15.0
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A World-Class Observatory

• Open to community
• Open to guest instruments
• Short proprietary period
• Flexible, capable facility instruments
• Broad user base

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Prototype SPIREX/Abu

• Every aspect of AIRS has been successfully
  demonstrated by SPIREX/Abu
• Telescope
• Camera
• Community Access
• Data pipeline
• AIRS requires no new technology

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The South Pole Site

• Excellent, low sky backgrounds
• Good, stable weather
• Adequate, steady seeing
• The South Pole site is extremely well
  characterized!
• Excellent infrastructure and support
• AIRS can achieve its technical requirements at
  Pole.

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Site monitoring for an entire season
The advantage of relentless observing data
pipelining
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Clear Skies

• Measurements from SPIREX in 1999 show photometric
  conditions at L-band 52 of the time
• Correlation with wind suggests 50 photometric
  over the last decade
• Additional 20-30 of time is useful for
  photometry with less accuracy

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Seeing at South Pole

• Three separate techniques used to measure seeing
• Differential image motion
• Microthermal measurements
• Echosonde measurements
• Seeing at V band (visual) is 1.7 arcsec
• Seeing at 3 to 5 mm will be 1.1 to 1.2 arcsec
• This seeing is perfectly adequate for surveys
  (and is at or near the diffraction limit).

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Unusual atmospheric conditions
Still air
Turbulent boundary layer
Katabatic wind
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Dome C A better site?

• Compared with the South Pole, Dome C is
• Higher
• Less windy
• May well have better sensitivity and seeing
• Not at 90o S
• More sky coverage
• Better access to communications satellites
• BUT.
• Site testing just beginning
• Infrastructure not yet comparable

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Dome C Weather Statistics
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Another Advantage of Dome CLand Transport

• Large pieces can be hauled in
• Greatly reduces assembly time on ice

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The Next Generation AIRS

• Larger aperture (2-meter class)
• Simultaneous 2-color imaging (HJK LM)
• Continuous (24-hr), automated operation

gt Big improvement in efficiency over SPIREX/ABU
In the thermal infrared, AIRS can survey faster
than the Keck or Gemini telescopes!
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Schedule

• Years 1 and 2 (Boston U.)
• Detailed design
• IR surveys with MIMIR at Lowell 72-inch
• Years 3 and 4 (Boston U. Lowell)
• Procurement construction
• Prepare test site at Anderson Mesa, Arizona
• Year 5 (Lowell)
• Systems integration
• Automation and remote operations
• Comprehensive tests

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Plan

• Complete conceptual design work 2003
• Submit new proposal to US NSF Office of Polar
  Programs June 2004
• Evaluate Dome C site-testing
• Explore collaborations with French, Italians,
  Australians, and other partners

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AIRS

• An L-band survey is critical to bridge the gap
  between near- and mid-IR surveys.
• Will revolutionize our understanding of
  protoplanetary disks, brown dwarfs, and star
  forming regions.
• A 2-meter class telescope is the next step for
  Antarctic IR astronomy.
• Essential step for larger telescopes and
  interferometers

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Summary

• Key science well-suited to Antarctica
• SPIREX/Abu demonstration
• Optical design well-developed
• Solid plan with low risk
• Will work well at South Pole
• May work even better at Dome C
• AIRS concept is sound and ready to go.