Molecular Tracers of Embedded Star Formation in Ophiuchus

In this paper we analyze nine SCUBA cores in Ophiuchus using the secondlowest rotational transitions of four molecular species (CO, CO, CO, and CO) to search for clues to the evolutionary state and star-formation activity within each core. Specifically, we look for evidence of outflows, infall, and CO depletion. The line wings in the CO spectra are used to detect outflows, spectral asymmetries in CO are used to determine infall characteristics, and a comparison of the dust emission (from SCUBA observations) and gas emission (from CO) is used to determine the fractional CO freeze-out. Through comparison with Spitzer observations of protostellar sources in Ophiuchus, we discuss the usefulness of CO and its isotopologues as the sole indicators of the evolutionary state of each core. This study is an important pilot project for the JCMT Legacy Survey of the Gould Belt (GBS) and the Galactic Plane (JPS), which intend to complement the SCUBA-2 dust continuum observations with HARP observations of CO, CO, CO, and CO J = 3→2 in order to determine whether or not the cold dust clumps detected by SCUBA-2 are protostellar or starless objects. Our classification of the evolutionary state of the cores (based on molecular line maps and SCUBA observations) is in agreement with the Spitzer designation for six or seven of the nine SCUBA cores. However, several important caveats must be noted in the interpretation of these results. First, while these tracers may work well in isolated cores, care must be taken in blindly applying these metrics to crowded regions. Maps of larger areas at higher resolution are required to determine whether the detected outflows originate from the core of interest, or from an adjacent core with an embedded YSO. Second, the infall parameter may not be an accurate tracer of star-formation activity because global motions of the cloud may act to emulate what appears to be the collapse of a single core. Centre for Radio Astronomy, University of Calgary, 2500 University Dr. NW, Calgary, AB, T2N 1N4, Canada, [email protected]; [email protected] Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany, [email protected] NRC-Herzberg Institute of Astrophysics, 5071 W. Saanich Road, Victoria, BC, V9E 2E7, Canada, [email protected]