Transcript Liu-NGAO-workshop-Sep2006.ppt

Planets around
Low-Mass Stars
and Brown Dwarfs
Michael Liu
Bruce Macintosh
NGAO Workshop, Sept 2006
Planets around VLM stars & brown dwarfs
~25 MJup
~5 MJup?
Chauvin et al (2005): VLT AO (IR WFS)
• Direct imaging and
spectroscopy of planets
easier around low-mass
stars and brown dwarfs.
• Study objects with SEDs
& atmospheres similar to
“regular” exoplanets, but
perhaps with diff origin.
• High contrast LGS +
IR tiptilt needed.
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NGAO: Planet detection sensitivity
• Very high contrast in near-IR enables imaging of Jovianmass planets around low-mass stars and brown dwarfs.
• This can only be
done by NGAO.
The stars are too
optically faint for ExAO
systems (I<8-9).
• A unique avenue
for testing planet
formation models,
by using a wide
range of stellar
host mass.
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NGAO opens a unique realm for
high contrast studies for a broad range
of science programs.
AO system
Contrast
Extreme AO
v.bright stars only
107–108
Keck NGAO
105–106
many targets
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Modeling the targets for NGAO
• Census of solar
neighborhood is
very incomplete
now …
• But in ~5 years will
be much better
(Pan-STARRS)
(preliminary)
• Can build a budget
of planet return as
a function of
contrast and IR T/T
sensitivity
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Key actions
• Detail science case including observing scenarios
– E.g. polarimetry, PSF subtraction, etc
• Prepare a maintainable contrast error budget
– Should this be 1d or 2d? Analytic? Simulations? How to keep
current? Who owns it?
• Identify a strawman coronagraph architecture
– Is this part of AO, science instrument, or in-between?
• Carry out analytic simulations of some key cases
• Figure out who actually does this
– Who does the work? Who pays for it? Who leads the area?
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Normalized intensity
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Sample analytic error budget
PSF components
1.0E-03
PSF noise
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Sample simulation: effect of static
calibration error on contrast
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Why do we need NGAO?
• Very high-contrast near-IR imaging
directly image planets and debris disks
• Large sky coverage
study stars over a very wide range of masses & ages
• Multi-band optical and IR wavelengths
determine properties & evolution of circumstellar material
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Debris Disks: Extrasolar analogs to
the asteroid & Kuiper Belt
Keck NGS: H-band
Resolved disks are a
goldmine for studying:
• structure
• composition
• evolution
• low-mass planets
100’s of these known from integrated light,
but only ~12 resolved to date (2 by AO).
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Debris disks studies with NGAO
simulated 3-hour H-band integration
of massive Kuiper Belt in the Pleiades (120 Myr, 130 pc)
Solar system model
Undetectable
Neptune with 1:1
resonant dust ring
High Strehl NGAO
Keck AO today
NGAO could image many (10s-100s)
analogs to the young solar system,
study other Kuiper Belts & low-mass planets
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The End
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