YOUNG STELLAR OBJECTS IN THE IRAS POINT-SOURCE CATALOG

The IRAS Point Source Catalog (IPSC), providing an infrared survey of 96% of the sky, is searched for low mass young stellar objects (YSOs). Three different statistical approaches are pursued to classify an initial set of 69436 sources out of the total of 245889 IPSC objects. The performance of the classifiers is assessed by means of false alarm and hit rates. The similarity, in infrared properties, to a combined sample of YSOs taken from Beichman et al. (1986) and Myers et al. (1987) is exploited by two simple classifiers to produce rank-ordered lists of YSO candidates. A third, two-stage classifier utilizes the infrared properties of galactic and extragalactic objects in conjunction with the clustering properties of YSOs on the sky. This combination considerably improves the discrimination between YSOs and other galactic sources and selects a sample of 5 825 YSO candidates lying outside of confused regions (viz. the galactic plane and the Magellanic clouds). According to our performance analysis 87% or 5068 of these YSO candidates are indeed YSOs (implying a contamination of 13% or 757 misclassified sources), while the selection reaches a completeness of 85%. From these figures-of-merit we can estimate that the initial sample contains in total 5962 YSOs outside the confused areas. The quality of this classification is empirically verified by examining IPSC sources from the initial sample in the well-studied Chamaeleon I star forming region