The Evolutionary State of Anemic Circumstellar Disks in IC 348 and The Primordial-to-Debris Disk Transition

We investigate the evolution of ∼ 3 Myr-old MIPS-detected circumstellar disks in IC 348 that may be in an intermediate stage between primordial, optically-thick disks of gas/dust and debris disks characteristic of the final stages of planet formation. We demonstrate that these anemic disks are not a homogenous class of objects corresponding to a unique evolutionary state. Rather, such disks around early (B/A) spectral type stars are most likely warm, terrestrial zone debris disks; MIPS-detected anemic disks around later (M) stars are likely evolved primordial disks such as transition disks in their mid-IR colors, accretion signatures, and disk luminosities. Anemic disks surrounding G and K stars contain both populations. The difference in evolutionary states between anemic disks surrounding early type vs. late-type stars is consistent with a mass-dependent evolution of circumstellar disks from the primordial disk phase through the debris disk phase. Specifically, disks characteristically get to the debris disk phase faster for early-type stars; debris disks dominate the disk population of early-type stars by ∼ 3–5 Myr. Debris disks take ∼ 13–30 Myr to dominate the disk population around late-type stars. Subject headings: stars: pre-main-sequence–planetary systems: formation — planetary systems: protoplanetary discs