2000ApJ...538..665W

Using the VLA, we have mapped the Orion Hot Core region (full extent 10") with an angular resolution of ∼1" in the (J,K)=(4,4) and (10, 9) inversion transitions of ¹⁴NH₃ and an angular resolution of 4" in the (J,K)=(2,2) and (3, 3) inversion transitions of ¹⁵NH₃. All of the single-dish flux density for the (10, 9) transition was recovered by the VLA, but a substantial fraction of the flux density in the (4, 4) and ¹⁵NH₃ (3, 3) lines was not detected. The missing flux density is from the spatially extended ``spike'' component. Assuming that local thermodynamic equilibrium (LTE) holds, we have calculated the optical depths of the (4, 4) inversion transition for all positions where the main and satellite lines were detected with sufficient signal-to-noise ratio. We combined our (10, 9) data with these (4, 4) line results to produce images of the rotational temperature, T<sub>rot</sub>, and the column density of ammonia, N(NH<sub>3</sub>). For the H<sub>2</sub> densities in the Hot Core, T<sub>rot</sub>=T<sub>kin</sub>, the kinetic temperature. An additional determination of T<sub>kin</sub> and N(NH<sub>3</sub>) was made by combining our (10, 9) inversion line data with our <sup>15</sup>NH<sub>3</sub> (3, 3) inversion line results. The <sup>15</sup>NH<sub>3</sub> inversion transitions have no quadrupole hyperfine structure so that the line shapes are simpler. The moment distribution of the <sup>15</sup>NH<sub>3</sub> (3, 3) line shows that the largest intensity-weighted line width arises close to the center of the Hot Core region. Thus, we may have discovered a low-luminosity outflow source embedded in the Hot Core. Alternatively, this may be a result of gas motions related to source ``I'', which is about half a beamwidth from this feature.