CO surveys with the 1.2 m telescopes are of two basic types distinguished by angular resolution: the so-called "superbeam" surveys have an angular resolution of 1/2° while the "full resolution" surveys typically have a resolution of 8.4 arcmin--the beamsize of the CfA 1.2 m telescope. Individual surveys cover tens-to-hundreds of square degrees (mapping, for example, a large local cloud or a Galactic quadrant), and within each survey parameters such as the sampling interval, velocity resolution, and rms noise are held constant.

Tom Dame (tdame@cfa.harvard.edu) is the long-time custodian of all the 1.2 m surveys, and may be contacted with questions or data requests.

Superbeam Surveys

The effective 1/2° resolution of the superbeam surveys, most conducted between 1979 and 1986, was achieved by stepping through a 4 x 4 grid of positions on the sky separated by 1/8° (slightly less than one beamwidth) during the accumulation of a single spectrum (a very cool test of the superbeam software can be viewed here). These surveys were combined into the first complete CO survey of the Milky Way by Dame et al.(1987). The composite superbeam survey is sometimes called the "Columbia CO Survey", because our group and the northern 1.2 m telescope were based at Columbia University until 1986. Table 1 and Figure 1 in Dame et al.(1987) summarize the individual superbeam surveys, all of which are available from Tom Dame.

The entire composite superbeam survey is available from the Astronomical Data Center in the form of 721 FITS-format latitude-velocity maps, one for each longitude observed (360° at 0.5° spacing). The composite survey also exists as a single 34 Mb FITS cube. This cube, or subsections of it, are available from Tom Dame.

The velocity-integrated superbeam map of the whole Galaxy (Fig. 2 from Dame et al. 1987) is available from the Astronomical Data Center as well (lbmap.fit).

Full-Resolution Surveys

A single integer FITS cube containing all of the full resolution data with 1/8° spacing on the sky and 1 km/s spacing in velocity would be of order 1 Gb in size, too large to easily distribute and use.

For relatively small-scale studies, you should check the Galactic map below (Fig.1 from Dame, Hartmann, & Thaddeus 2001) to determine the survey(s) you need.

Then use Table 1 from the same paper to determine the specs and a reference for the survey(s) of interest. Most of the references appear in our list of Major CO Surveys. Contact the P.I. if possible, otherwise Tom Dame, to discuss whether the survey(s) are available for distribution; most of the published surveys are freely distributed.

For many scientific purposes only the total molecular column density, N(H₂) is needed, not the full v-l-b datacube. In these cases, the velocity-integrated (W_CO) map can be downloaded in FITS format from this webpage, and scaled to units of N(H₂) using: