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 Title: 

            Frequency of Disks in the Nearest Young Clusters, as Seen by Spitzer

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 Authors:

          Lori Allen (CfA), 

          Tom Megeath (CfA),

          Nuria Calvet (CfA),

          Paola D'Alessio (UNAM),

          Bruno Merin (LAEFF),

          Lee Hartmann (CfA),

          James Muzerolle (Steward Obs),

          Erick Young (Steward Obs),

          Rob Gutermuth (U Rochester),

          Judith Pipher (U Rochester),

          Giovanni Fazio (CfA),

          Philip Myers (CfA)

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 Abstract:

          We present results of a Spitzer IRAC and MIPS survey of the nearest young embedded clusters and groups, including those in rho Ophiuchus, R Corona Australis, Chamaeleon I, Lupus III, Taurus/L1495 and Taurus/L1551.   We use IRAC, MIPS, and ground-based near-IR photometry to determine the frequency of disks around stars and brown dwarfs in these clusters.  Through comparison of observed 1-24 micron colors with predicted colors from models of disks and infalling envelopes, we discuss the relative fractions of sources with protostellar envelopes, with accretion disks, and with large inner disk holes.   Although Spitzer is unable to spatially resolve circumstellar disks in these clusters, it will produce the most sensitive and complete list of disks around young stars within 150 pc.  Spitzer surveys such as the one presented here will make invaluable contributions to target selection for future interferometric studies. 

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