The Gould Belt 'MISFITS' Survey: The Real Solar Neighborhood Protostars

We present an HCO+ survey of Class 0+I and Flat SED young stellar objects (YSOs) found in the Gould Belt clouds by surveys with Spitzer. Our goal is to provide a uniform Stage 0+I source indicator for these embedded protostar candidates. We made single point HCO+ measurements toward the source positions at the CSO and APEX of 546 YSOs (89% of the Class 0+I + Flat SED sample). Using the criteria from van Kempen et al., we classify sources as Stage 0+I or bona fide protostars and find that 84% of detected sources meet the criteria. We recommend a timescale for the evolution of Stage 0+I (embedded protostars) of 0.54 Myr. We find significant correlations of HCO+ integrated intensity with ? and Tbol but not with Lbol. The detection fraction increases smoothly as a function of ? and Lbol, while decreasing smoothly with Tbol. Using the Stage 0+I sources tightens the relation between protostars and high extinction regions of the cloud; 89% of Stage I sources lie in regions with AV > 8 mag. Class 0+I and Flat SED YSOs that are not detected in HCO+ have, on average, a factor of ?2 higher Tbol and a factor of ?5 lower Lbol than YSOs with HCO+ detections. We find less YSO contamination, defined as the number of undetected YSOs divided by the total number surveyed, for sources with Tbol ? 600 K and Lbol ? 1 L?. The contamination percentage is >90% at AV < 4 mag and decreases as AV increases.