Molecular Tracers of Embedded Star Formation in Ophiuchus

Abstract

In this paper we analyze nine SCUBA cores in Ophiuchus using the second-lowest rotational transitions of four molecular species (12CO, 13CO, C18O, and C17O) 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 13CO are used to determine infall characteristics, and a comparison of the dust emission (from SCUBA observations) and gas emission (from C18O) 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 12CO, 13CO, C18O, and C17O 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 exist in the interpretation of these results, many of which large mapping surveys like the GBS may be able to overcome to provide a clearer picture of activity in crowded fields.

43 pages including 19 postscript figures. Accepted for publication in the PASP

References in corpus (24)

• The Spitzer Space Telescope Mission
• From Molecular Cores to Planet-forming Disks: A SIRTF Legacy Program
• A Search for Infall Motions Toward Nearby Young Stellar Objects
• Star formation in clusters: a survey of compact mm-wave sources in the Serpens core
• The Evolution of Outflow-Envelope Interactions in Low-Mass Protostars
• ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster
• Bolocam Survey for 1.1 mm Dust Continuum Emission in the c2d Legacy Clouds. II. Ophiuchus
• The Nature of the Dense Core Population in the Pipe Nebula: Thermal Cores Under Pressure
• A Survey for Infall Motions toward Starless Cores. I. CS (2-1) and N${}_2$H${}^{+}$ (1-0) Observations
• An Extinction Threshold for Protostellar Cores in Ophiuchus
• New Protostellar Collapse Candidates: An HCO+ Survey of the Class 0 Sources
• The James Clerk Maxwell Telescope Legacy Survey of Nearby Star-forming Regions in the Gould Belt
• The Degree of CO Depletion in Pre-stellar Cores
• Current Star Formation in the Perseus Molecular Cloud: Constraints from Unbiased Submillimeter and Mid-Infrared Surveys
• Observations of L1521F: a highly evolved starless core
• Molecular freeze-out as a tracer of the thermal and dynamical evolution of pre- and protostellar cores
• HST/NICMOS Imaging Survey of the Ophiuchus (Lynds 1688) Cluster
• Imaging Scattered Light from the Youngest Protostars in L1448: Signatures of Outflows
• How to Identify Pre-Protostellar Cores
• Probing Inward Motions in Starless Cores Using The HCN J = 1-0 Hyperfine Transitions : A Pointing Survey Toward Central Regions
• Does Infall End Before the Class I Stage?
• ISOCAM-CVF spectroscopy of the circumstellar environment of young stellar objects
• The Possibly Remnant Massive Outflow in G5.89-0.39: I - Observations and Initial MHD Simulations
• A Multiple System of Radio Sources at the Core of the L723 Multipolar Outflow

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• Outflow forces of low mass embedded objects in Ophiuchus: a quantitative comparison of analysis methods
• Droplets I: Pressure-Dominated Sub-0.1 pc Coherent Structures in L1688 and B18
• The Initial Conditions of Clustered Star Formation. II. N2H+ Observations of the Ophiuchus B Core
• The Initial Conditions of Clustered Star Formation III. The Deuterium Fractionation of the Ophiuchus B2 Core
• Deuterium Fractionation in the Ophiuchus Molecular Cloud
• The physical and chemical properties of the $\rho$ ophiuchi A dense core