A Deeper Look at the 3-10 Myr Old Disks in the Orion OB1 Association

We propose to obtain deep 70/160 micron PACS Photometer observationsof populations in the Orion OB1 association, spanning the critical3 to 10 Myr range of ages when disks are supposed todissipate and planets to form. Our ongoing largescale survey of theOrion OB1 starforming regions has allowed us to find the elusive lowmass population in the older parts of the association, and secure thephotometric and spectroscopic data to fully determine the stellar andaccretion properties of these objects. We propose to obtain slowspeedscans of five 30.x30. fields, covering sections of the virgul 3 Myrold cluster sigma Ori, a virgul 5 Myr old group in the Ori OB1bsubassociation, and the virgul 9 Myr old 25 Ori group, the mostpopulous stellar group at this age within 500 pc. Our Spitzer IRACand MIPS data for the proposed fields allow us to estimate thatwe will detect at least 62 disks in our PACS observations, 48%of which also have Spitzer IRS data. With the Herschel farinfrared fluxesand our midinfrared and optical fluxes wewill construct the most complete spectral energy distributions for alarge sample of 310 Myr disks. The interpretation of these SEDs withour irradiated accretion disk codes, constrained by the stellarparameters and mass accretion rates determined independently from theUV excess, will allow the best characterization to date of disks inthis age range, and provide essential constraints on theoretical models ofdisk evolution and planet formation. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]