The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. IV. Unveiling the Embedded Intermediate-Mass Protostar and Disk within OMC2-FIR3/HOPS-370

Abstract

Abstract We present ALMA (0.87 and 1.3 mm) and VLA (9 mm) observations toward the candidate intermediate-mass protostar OMC2-FIR3 (HOPS-370; L bol ∼ 314 L ⊙) at ∼01 (40 au) resolution for the continuum emission and ∼025 (100 au) resolution of nine molecular lines. The dust continuum observed with ALMA at 0.87 and 1.3 mm resolves a near edge-on disk toward HOPS-370 with an apparent radius of ∼100 au. The VLA observations detect both the disk in dust continuum and free–free emission extended along the jet direction. The ALMA observations of molecular lines (H2CO, SO, CH3OH, 13CO, C18O, NS, and H13CN) reveal rotation of the apparent disk surrounding HOPS-370 orthogonal to the jet/outflow direction. We fit radiative transfer models to both the dust continuum structure of the disk and molecular line kinematics of the inner envelope and disk for the H2CO, CH3OH, NS, and SO lines. The central protostar mass is determined to be ∼2.5 M ⊙ with a disk radius of ∼94 au, when fit using combinations of the H2CO, CH3OH, NS, and SO lines, consistent with an intermediate-mass protostar. Modeling of the dust continuum and spectral energy distribution yields a disk mass of 0.035 M ⊙ (inferred dust+gas) and a dust disk radius of 62 au; thus, the dust disk may have a smaller radius than the gas disk, similar to Class II disks. In order to explain the observed luminosity with the measured protostar mass, HOPS-370 must be accreting at a rate of (1.7−3.2) × 10−5 M ⊙ yr−1.