emil-christensen-sasp-2014
TRANSCRIPT
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Modeling Dust in Exo-Kuiper Belts
Emil Christensen
Advisor: Christine Chen
August 14th 2014
http://www.jpl.nasa.gov/images/kepler/20120613/kepler20120613-full.jpg
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MotivationScientific Motivations…
• Characterize thermal emission from cold dust in debris disks
• Constrain dust grain composition and size distribution
• Quantify how properties change with stellar age and mass
In the Grander Scheme…
• Is our solar system unique?• Is our solar system’s formation
history unique?• Are there other habitable
worlds like ours?
Mdust = 21020 g = 10-10 Mplanets = 10-4 MMAB
LIR(dust) = 100 LIR(planets)
Why dust?Because it’s easy to see,
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Data• 15 objects• Infrared Spectrograph (IRS)
– Warm dust– λ ≈ 5 – 40 μm– R ≈ 60 – 600
• Multiband Imaging Photometer for Spitzer (MIPS) SED Mode– New!– Cold dust– λ ≈ 50 – 100 μm– R ≈ 15 – 25
• Calibrated with MIPS photometry (24μm and 70μm)
• Photosphere subtracted
Phot
osph
ere
Subt
ract
ed
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http://carrot.mcb.uconn.edu/~olgazh/bioinf2010/images/MCRobot.png
PSO
Modeling• Single/Double rings
– 6/12 free parameters• Distance, grain size, mass of each
grain species
• Continuous dust disk– n(a,r) = n0a-qr-α
– 10 free parameters• Inner/outer/power radius,
lower/upper/power grain size, mass of each grain species
• Silicate Grains– Olivine– Pyroxene– Forsterite– Enstatite
http://marple.eeb.uconn.edu/mcmcrobot/wp-content/uploads/2012/09/cropped-MCMCRobotFrontImage.png
MCMC
http://commons.wikimedia.org/wiki/File:Debris_Disks_Around_Sun-Like_Stars_AU_Microscopii_and_HD_107146.jpg
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ResultsPh
otos
pher
e Su
btra
cted
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Future Project:Water Ice Emission
• Prominent feature in range covered by our data
• Will look for evidence of water ice in model fit
• Want to understand how earth obtained its water
• Next feature to be added to model
Malfait et al. (1999)
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Conclusions(Not quite yet but soon)
• Good (Χ2 < 6) fits for most of the objects with the new data
• New fits capture cold dust much better• Grain radius power law consistent with
collisional equilibrium• Tools will be released (V1.0) on Github next
week
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Thank you!Check out the modeling tool here:
https://github.com/EmilRex/Silicate_Feature_Analysis
http://www.jpl.nasa.gov/images/kepler/20120613/kepler20120613-full.jpg
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Probability Distributions
Mittal et al. (2014, submitted)