1. Study of Planet forming Systems Orbiting Intermediate-mass Stars Sweta Shah Ithaca College Advisor: Dr. Luke Keller In collaboration with the NASA Spitzer Space Telescope InfraRed Spectrograph Disk’s Team Image credit: Caltech

2. Theory of Planet formation Adapted from Hogerheide 1998

3. Why intermediate mass (Herbig Ae Be) stars ? Hot and massive 12,000 - 18,000 K 2-10 solar mass Excess thermal (IR) radiation ‘e’ Emission line spectra Circumstellar disks in Orion Nebula (Hubble Space Telescope Image: McCaughrean & O’Dell 1995)

4. Spectral characteristics of the Accretion Disk Thermal IR excess PAH Dust -silicates Spectral Energy Distribution (Malfait et al. 1998) UV mm

5. Correlation of SED and disk geometry (Malfait et al. 1998)

6. Physical structure of the disks: SEDs (UV-mm) IRS SL IRS SL IRS SL IRS SL LL (Malfait et al. 1998)

7. Spectral features - PAH? Polycyclic Aromatic Hydrocarbon Excited by UV radiation H H H H H H H H H H H H Sloan, Keller, Leibensperger et al. 2005 very stable

8. What is the shape of the disk? How do we test this hypothesis?

9. Measuring the strength of “bumps” in Infrared continuum 6 13 25

10. Star with no disk Flared disks Flat disks Dust grain growth and settling Keller, Shah et al. 2006, paper in preparation Increasing 6-13  m SED slope Increasing 13-25  m SED slope

11. Ultimate Goal Disk evolution in time I PAH ?!

12. Thanks! (Any ?)

13. Spitzer InfraRed Telescope Facility –Background-limited sensitivity 3 – 180  m –85 cm f/12 beryllium R-C telescope, T < 5.5K –Three scientific instruments provide: Imaging/photometry, 3-180  m Spectroscopy, 5-40  m (R = 90 & 600) Spectrophotometry, 50-100  m –5.5 yr lifetime –Launched on 25 August 2003 –Birth stone: forsterite IRS