Circumstellar Disk Evolution in Nearby Molecular Clouds
          Lucas Cieza, UT Austin
          Paul Harvey, UT Austin
          C2D Team

          We use initial data from the Spitzer Legacy Project 'From Molecular Cores to Planet Forming Disks' (c2d) to investigate the evolution of circumstellar disks in five nearby molecular clouds: Chameleon, Lupus, Ophiuchus, Perseus and Serpens. We estimate the ages of ~100 classical and weak-lined T Tauri stars across the clouds using different evolutionary tracks, and construct their Spectral Energy Distribution (SED) from IRAC, MIPS, J,K,H, I and z photometry.  Near-infrared excess is used as an indication of inner accretion disks, while the presence of far-infrared excess, in the absence of excess at shorter wavelengths, is interpreted as the signature of systems with large inner holes. We first describe our different data sets and discuss the method used to estimate stellar ages. Second, we present the SEDs of the targets and apply simple models to infer the basic properties of their disks. Then, we divide the sample into several age bins, discuss the observed evolutionary trends, and try to discriminate primordial disks from debris disks. Finally, we compare our results with previous studies and discuss their implications on the dissipation timescale of circumstellar disks and on planet formation theories.