The Gould Belt "Misfits" Survey: The Real Solar Neighborhood Protostars

We present an HCO+ J = 3. 2 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+J = 3 -> 2 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 a and Tbol but not with Lbol. The detection fraction increases smoothly as a function of a 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 A(V) > 8 mag. Class 0+I and Flat SED YSOs that are not detected in HCO+ have, on average, a factor of similar to 2 higher Tbol and a factor of similar to 5 lower L-bol 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 T-bol less than or similar to 600 K and L-bol greater than or similar to 1 L-circle dot. The contamination percentage is > 90% at A(V) < 4 mag and decreases as A(V) increases.