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
We present ALMA (0.87~mm and 1.3~mm) and VLA (9~mm) observations toward the
candidate intermediate-mass protostar OMC2-FIR3 (HOPS-370;
Lbol~314~L⊙) at ∼0.1" (40~au) resolution for the continuum
emission and ~0.25" (100 au) resolution of nine molecular lines. The dust
continuum observed with ALMA at 0.87~mm and 1.3~mm resolve 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_sun
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 (SED) 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 between 1.7 and
3.2×10−5~M⊙~yr−1.Comment: Accepted to ApJ; 51 pages, 12 Figures, 7 Table