SIMBAD references

NGC 2024 has been imaged in the J=1-0 line of C¹⁸O and in the continuum at a wavelength of 2.7mm with a spatial resolution of ∼10". The continuum images show four features found in previous studies. A 160mJy point source coincides with the position of IRS 2. When the flux density at 2.7mm is combined with those at 6cm and 1.3cm, we find that the flux density of this source depends on frequency, ν, as ν^1.3. The positions of the other three continuum sources agree very well with the positions of the 1.3mm sources FIR 3, 5 and 6, given by Mezger et al. (1988, 1992). Combining the 2.7 and 1.3mm flux densities, we find that flux density shows a dependence ≥ν⁴. Using our upper limits to the 2.7mm continuum flux densities at the positions of FIR 1, 2, 4 and 7, we obtain a similar dependence. C¹⁸O emission is found in 3 slightly extended regions. The two southern peaks are offset from the positions of FIR 5 and FIR 6. The northern peak is located ≤4" from the position of FIR 2. For the C¹⁸O clouds, H₂ column densities from the virial theorem give (CO/H₂) ratios of ∼10^–5, about 10% of the normally used value.