MAGMA Data Release 2 BETA:
CO Data for the LMC

Release Notes (4 May 2012)

Data cubes have been regenerated in the heliocentric velocity frame. In Livedata, a fix for an error in the application of the calibration factors and improved baseline estimation have been implemented, although a residual baseline still had to be subtracted. The baseline offset appears to result from slight non-Gaussianity of the noise, perhaps due to non-linearities in the system. The same linear baseline has been subtracted from all spectra in the cubes. In channel space, the fitted baseline (in K) is given by (2e-5)*z+(5e-3), where z ranges from 1 to 266.

Aside from the velocity axis labeling, the results should be substantially the same as in Data Release 1, and the cloud catalogues have not been regenerated.

This is a beta release for internal use only; the next official release will include additional OTF maps observed in 2012-2013.

Data Cubes and Moment Maps

Cubes are provided at two different spatial resolutions. These are gzipped FITS images constructed using the SIN projection in the barycentric velocity frame. Note that regions which were not observed have been assigned a blank value. The brightness temperature scale corresponds to the main beam brightness temperature assuming a Gaussian beam.

CO intensity is determined in two ways: (1) Masking by the 3-sigma contour of a cube that has been smoothed to 90" resolution, then integrating from 215 to 320 km/s; and (2) Identifying the peak of each spectrum and, if at least 4-sigma in intensity, integrating all channels within 10 channels of the peak (window method). The first method was adopted for the ApJS paper. For each intensity image, a corresponding rms image is constructed by scaling the rms noise per channel by the square root of the number of channels that contribute to the intensity map at that position.