1. Identifying the Key Factors in the Planet Formation Process
Intern: Tracy Heran
Mentor: Dr. Ilaria Pascucci
Department: Astronomy
4/19/08
University of Arizona

2. Outline 1. Introduction to Circumstellar Disks
2. Problem Statement and Objective
3. Methods
4. Results
5. Conclusions
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3. Introduction to Circumstellar Disks
Planets form from circumstellar disks of dust and gas around young stars
Initiated by growth and crystallization of sub-micron dust grains with dust settling toward disk mid-plane
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4. Problem Statement
Stellar age and luminosity alone cannot explain the diverse properties of disks
Project Objective
Search for an underlying factor that may explain circumstellar disk characteristics in young stars of similar ages and spectral types
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5. Methods
Search for correlations between star/disk properties for a large sample of young-sun-like stars (44)
1.3 mm flux measures the dust disk mass
Ratio of 24 m to 13 m infrared flux is a proxy for dust settling toward the disk midplane
10 m silicate feature strength and shape provide information about grain size and amount of dust crystallization
Accretion rate is the rate at which star accretes gas from the disk
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6. Methods, Continued Generated plots and histograms using IDL
Performed statistical analysis tests that could incorporate non-detections (upper limits) and detections
Peto & Prentice Generalized Wilcoxon tests
Probability that samples are drawn from same population
Kendall Tau test
Probability that there is a correlation between variables
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7. Results
Correlation between presence of a stellar companion and low 1.3 mm flux
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8. Results, Continued Moderate
anti-correlation between accretion rate and strength of 10 m silicate feature
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9. Conclusions 1. Correlation between binary stars and low 1.3 mm fluxes
truncation of disk by stellar companion that decreases disk mass, leaving less mass to form planets
2. Moderate anti-correlation for 10 m silicate feature strength and accretion rate
higher accretion rates stir up large grains in the midplane that are then observable in the mid-infrared
Future research could involve expanding the sample to include more stars and looking at data from other wavelengths such as X-ray, UV, and far-infrared
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10. the Arizona Space Grant Consortium and Dr. Ilaria Pascucci
Thank you to
the Arizona Space Grant Consortium
and
Dr. Ilaria Pascucci
for giving me this wonderful opportunity.
Any Questions?
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