and temperature: $$N(\MOLH ) = \frac{S_{1.2mm}}{\Omega_{\rm beam} \, B_{\nu}(T)\,
 \kappa_{1.2mm} \; m } ,$$ where $N(\MOLH )$ is the averaged  column density , $S_{1.2mm}$ is the emitted 1.2mm flux density from the core, $\Omega_{\rm beam}$ is the telescope beam solid angle, $\kappa_{1.2mm}$ is the dust absorption coefficient per gram of gas at 1.2mm, $B_{\nu}(T)$ is the Planck function at temperature $T$, and $m$ the mean molecular mass. In our calculations we used a dust temperature $T_{\rm dust}$ = 10 K, close to the gas temperature found by Codella et al. ([@cod97]) using ammonia data (9.1 K), a dust opacity $\kappa_{1.2mm} \, =$ 0.005 cm$^{2}$ g$^{-1}$ (André et al. [@awm96]) and $m$ = 2.33 amu (with uncertainties of typically 50%; see e.g. Bianchi et al. [@bga03] and Gonçalves et al. [@ggw04]). This expression can be integrated over the 1.2mm map to derive the total gas mass.

In this fashion, we derive a core mass from the continuum measurements, within the large ellipse in Fig. \[fig1a\], of 5.5$\pm$0.5   corresponding to an integrated total flux of $3.0\pm 0.3$ Jy. (The error is dominated by errors in calibration and baseline removal.) Within the 26 beam, used for our line measurements, the enclosed mass is 