Transcript
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
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,
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
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
ResultsPh
otos
pher
e Su
btra
cted
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)
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
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
Probability Distributions
Mittal et al. (2014, submitted)
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