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

Outline 1. Introduction to Circumstellar Disks 2. Problem Statement and Objective 3. Methods 4. Results 5. Conclusions University of Arizona 2

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 University of Arizona 3

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 University of Arizona 4

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 University of Arizona 5

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 University of Arizona 6

Results Correlation between presence of a stellar companion and low 1.3 mm flux University of Arizona 7

Results, Continued Moderate anti-correlation between accretion rate and strength of 10 m silicate feature University of Arizona 8

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 University of Arizona 9

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? University of Arizona 10