The extragalactic view of W51 at 220 and 290 GHz

These are APEX data covering 5.5' x 5.5' centered on W51 Main: These are calibrated to T_A* units. APEX telescope efficiencies can be found here: and are approximately 0.75 at the observed frequencies.

W51 is at a distance of 5.1 kpc, so this field of view is equivalent to 8.1 pc, or 1.7" at 1 Mpc or 0.33" at 5 Mpc.

The linewidth is 12.7-15.2 km/s (H2CO 4-3, CO 2-1) FWHM averaged over this full field.

Images of the spectra, with some lines identified, are shown here (open them in a new tab to see the full resolution). The baselines aren't great, but it's easy to fit a local linear baseline around any of the fairly narrow lines.

The same images, but not zoomed in the y-direction. Note that 12CO 2-1 is very near the edge of the band; it peaks around 20 K:

Scripts to obtain the data and process them are here:

See the related project by Watanabe et al looking at W51 in the 3mm band: