Planets around Planets around Low-Mass Stars Low-Mass Stars

and Brown Dwarfsand Brown Dwarfs

Michael LiuMichael LiuBruce MacintoshBruce Macintosh

NGAO Workshop, Sept 2006NGAO Workshop, Sept 2006

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Planets around VLM stars & brown dwarfsPlanets around VLM stars & brown dwarfs

• Direct imaging and Direct imaging and spectroscopy of planetsspectroscopy of planets easier around low-mass easier around low-mass stars and brown dwarfs.stars and brown dwarfs.

• Study objects with Study objects with SEDs & SEDs & atmospheresatmospheres similar to similar to “regular” exoplanets, but “regular” exoplanets, but perhaps with diff origin.perhaps with diff origin.

• High contrast LGSHigh contrast LGS + + IR tiptiltIR tiptilt needed. needed.

~5 MJup?

~25 MJup

Chauvin et al (2005): VLT AO (IR WFS)

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NGAO: Planet detection sensitivityNGAO: Planet detection sensitivity• Very high contrast in near-IR enables imaging of Jovian-Very high contrast in near-IR enables imaging of Jovian-

mass planets around mass planets around low-mass starslow-mass stars and and brown dwarfsbrown dwarfs..

• This can only be This can only be done by NGAO.done by NGAO. The The stars are too optically stars are too optically faint for ExAO systems faint for ExAO systems (I<8-9). (I<8-9).

• A unique avenue for A unique avenue for testing planet testing planet formation models, by formation models, by using a wide range using a wide range of stellar host mass.of stellar host mass.

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NGAO opens a unique realm for NGAO opens a unique realm for high contrast studies for a high contrast studies for a broadbroad range range

of science programs.of science programs.

AO systemAO system ContrastContrast

Extreme AOExtreme AOv.v.bright stars onlybright stars only

101077–10–1088

Keck NGAOKeck NGAOmany targetsmany targets 101055–10–1066

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Modeling the targets for NGAOModeling the targets for NGAO

• Census of solar Census of solar neighborhood is neighborhood is very incomplete very incomplete now …now …

• But in ~5 years will But in ~5 years will be much better be much better (Pan-STARRS)(Pan-STARRS)

• Can build a budget Can build a budget of planet return as of planet return as a function of a function of contrast and IR T/T contrast and IR T/T sensitivitysensitivity(preliminary)

6 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?

7 Sample analytic error budget

PSF components

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

Atmos. FittingTelescope

Telescope vibrationInitial calibration

Atmospheric bandwidthWFS measurementInternal optical errors

Quad cell changesPost-coron. aberrs.Flexure/Beam ShearChromatic beam shear

Scintillation

Polarization errors

Tertiary intensity errors

Internal static intensity errors

Coronagraph leak&pinned speckles

Flat field errorsPhoton noise

Total

Normalized intensity

PSF intensity PSF noise

8Sample simulation: effect of static

calibration error on contrast

99

1010

Why do we need NGAO?Why do we need NGAO?

• Very high-contrast near-IR imagingVery high-contrast near-IR imagingdirectly image planets and debris disksdirectly image planets and debris disks

• Large sky coverageLarge sky coveragestudy stars over a very wide range of masses & agesstudy stars over a very wide range of masses & ages

• Multi-band optical Multi-band optical andand IR wavelengths IR wavelengthsdetermine properties & evolution of circumstellar materialdetermine properties & evolution of circumstellar material

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Debris Disks: Extrasolar analogs to Debris Disks: Extrasolar analogs to the asteroid & Kuiper Beltthe asteroid & Kuiper Belt

• structurestructure• compositioncomposition• evolutionevolution• low-mass planetslow-mass planets

Keck NGS: H-bandResolved disks are a goldmine for studying:

100’s of these known from integrated light, but only ~12 resolved to date (2 by AO).

1212

Debris disks studies with NGAODebris disks studies with NGAOsimulated 3-hour H-band integration simulated 3-hour H-band integration

of massive Kuiper Belt in the Pleiades (120 Myr, 130 pc)of massive Kuiper Belt in the Pleiades (120 Myr, 130 pc)

Undetectable Neptune with 1:1 resonant dust ring

NGAO could image many (10s-100s) analogs to the young solar

system, study other Kuiper Belts & low-

mass planets

Solar system model High Strehl NGAO Keck AO today

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The EndThe End