Emil-Christensen-SASP-2014

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)