4. The Maximum Entropy Method (MEM) deconvolution
The angular resolution of the total integrated line intensity map has been improved by using a MEM deconvolution algorithm (Wilczek & Drapatz 1985). The SEST HPBW of the CO observations was and the observational grid spacing was generally in the central region, i.e. appropriate for MEM-deconvolution. The best deconvolution was obtained after 14 smoothly converging iterations resulting in a -value of 5.7 for the final map. The expected resolution of the MEM map is about a third of the beamwidth used, i.e. .
The MEM map is presented in Fig. 5 and Fig. 6. In Fig. 5, the image has been rotated clockwise by , so that the new x- and y-axes are the galaxy's minor and major axes, respectively. Here the deconvolved integrated intensities are displayed in a grey-scale representation to emphasize the detailed structure of the CO distribution. The major axis of the galaxy is the y-axis, which is the same as in Fig. 4, thus facilitating direct comparison of the molecular gas spatial and velocity structure along the major axis.
© European Southern Observatory (ESO) 1999
Online publication: March 1, 1999