HIGH SPATIAL-RESOLUTION 1.3 CENTIMETER IMAGING OF THE NGC 2024 STAR-FORMING REGION

The NGC 2024 star-forming region has been imaged in the (J, K) = (1, 1) and (2, 2) inversion lines of NH3 and the radio continuum at a wavelength of 1.3 cm with a spatial resolution of 3". The continuum image shows one pointlike and two extended features found in previous, lower resolution studies. The unresolved source (in a 2.4 beam) has a 1.3 cm flux density of 19 mJy and coincides with the position of IRS 2. Using the 6 cm data of Snell & Bally, this source has a spectral index (S is-proportional-to nu(alpha)) of alpha = 1.2 +/- 0.2. The radio continuum emission is likely due to an ionized stellar wind. The mass-loss rate is almost-equal-to 3.6 x 10(-7) M. yr-1. The southern extended ionized feature (SCP) coincides with the sharp southern boundary of the H II region: an interface where the H II region is expanding into the northern edge of a group of high density molecular regions. The central part of the extended northern region (NCP) is at the southeast boundary of another group of molecular regions. This central portion of the NCP could be caused by a flow of ionized material off a protrusion of the northern molecular ridge into the extended H II region. The positions of the NH3 maxima generally agree with the positions of the 1.3 mm FIR sources of Mezger et al. For the molecular regions nearest the SCP and NCP, the relative abundances of NH3 are lower, and the FWHP line widths and values of T(k) are larger than the average values (almost-equal-to 10(-9), 1 km s-1 and 30 K, respectively).