molecular mass. This second step should benefit significantly from combination of our data with dust column density determined from e.g. 2MASS data. This effort is in progress and will be reported in a subsequent publication.

### Carbon Monoxide Column Density {#col_dens_calc}

The three different different regions of the cloud, defined by the detectability of each isotopologue, require different schemes to determine the carbon monoxide column density. We ignore mask 3 in determining the column density and to the mass of the cloud as we cannot readily correct for the artificial non–detections of  (discussed above). Its extremely small area and weak  emission make its contribution negligible.

Mask 2 represents the portion of the cloud that is most conventional in terms of column density determination. Since we have both  and  in each pixel, we determine the kinetic temperature from the peak value of the  (with appropriate correction for antenna efficiency). Here (as well as for other mask regions), we use the maximum antenna temperature of  in the velocity interval between 0  and 12 . The kinetic temperature is distributed from 3 K to 21 K, but with the vast majority of positions having kinetic temperatures between 6 K and 12 K. Since 