Herschel Orion Protostar Survey

Most objects have near-infrared photometry from 2MASS, mid- and far-infrared data from Spitzer and Herschel, and submillimeter photometry from APEX; thus, the SEDs cover 1.2 - 870 microns and are used to classify the sample into protostellar classes. Of the 410 YSOs, 330 have Spitzer and Herschel data and are mostly protostars; the remaining objects include likely extragalactic contaminants and faint YSOs.

Using mid-IR spectral indices and bolometric temperatures, the sample of 330 YSOs is classified into 92 Class 0 protostars, 125 Class I protostars, 102 flat-spectrum sources, and 11 Class II pre-main-sequence stars. HOPS also implements a simple protostellar model (including a disk in an infalling envelope with outflow cavities) to generate a grid of 30,400 model SEDs and uses it to determine the best-fit model parameters for each protostar.