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Understanding how disks dissipate is essential to studies of planetformation. However, identifying exactly how dust and gas dissipates iscomplicated due to difficulty in finding objects clearly in the transition oflosing their surrounding material. We use Spitzer IRS spectra to examine 35photometrically-selected candidate cold disks (disks with large inner dustholes). The infrared spectra are supplemented with optical spectra to determinestellar and accretion properties and 1.3mm photometry to measure disk masses.Based on detailed SED modeling, we identify 15 new cold disks. The remaining 20objects have IRS spectra that are consistent with disks without holes, disksthat are observed close to edge-on, or stars with background emission. Based onthese results, we determine reliable criteria for identifying disks with innerholes from Spitzer photometry and examine criteria already in the literature.Applying these criteria to the c2d surveyed star-forming regions gives afrequency of such objects of at least 4% and most likely of order 12% of theYSO population identified by Spitzer.  We also examine the properties of these new cold disks in combination withcold disks from the literature. Hole sizes in this sample are generally smallerthan for previously discovered disks and reflect a distribution in betteragreement with exoplanet orbit radii. We find correlations between hole sizeand both disk and stellar masses. Silicate features, including crystallinefeatures, are present in the overwhelming majority of the sample although 10micron feature strength above the continuum declines for holes with radiilarger than ~7 AU. In contrast, PAHs are only detected in 2 out of 15 sources.Only a quarter of the cold disk sample shows no signs of accretion, making itunlikely that photoevaporation is the dominant hole forming process in mostcases.

A Spitzer c2d Legacy Survey to Identify and Characterize Disks with Inner Dust Holes