192 | | Now we are ready to image the source. |
| 192 | Now we are ready to image the source. In the DAC method, there are three ways to make images of the source |
| 193 | without recombining the UV data first. We will attempt all three methods: |
| 194 | 1. invert using the MFS option as normal, then clean and restor |
| 195 | 1. invert using both the MFS option and the SDB option, then use mfsclean and restor |
| 196 | 1. invert making a cube of all channels, then clean, restor and then make a moment map |
| 197 | |
| 198 | The first way is the way most familiar to MIRIAD users doing continuum reduction. We can make images of all |
| 199 | the individual datasets in the following way: |
| 200 | |
| 201 | dac_repeat.pl --task invert --repeat vis --repeat-freq rnovalmc --repeat map --repeat-freq rnovalmc_%f.map --repeat beam --repeat-freq rnovalmc_%f.beam "select=-auto,-ant(6)" stokes=ii options=double,mfs slop=1 |
| 202 | |
| 203 | This makes 16 each of the .map and .beam files. Let's get an idea of the RMS noise of each of the maps using |
| 204 | imstat. Using kvis we can identify a region (xmin,ymin,xmax,ymax)=(39,0,65,22) that contains no emission. |
| 205 | Using dac_repeat.pl we can run imstat on each set: |
| 206 | |
| 207 | ./dac_repeat.pl --task imstat --repeat in --repeat-freq rnovalmc_%f.map "region=boxes(39,0,65,22)" axes=ra,dec |
| 208 | |
| 209 | From this we find that the RMS noise values are: |
| 210 | || f (MHz) || RMS (uJy) || |
| 211 | || 4540 || 246 || |
| 212 | || 4668 || 214 || |
| 213 | || 4796 || 294 || |
| 214 | || 4924 || 385 || |
| 215 | || 5052 || 340 || |
| 216 | || 5180 || 426 || |
| 217 | || 5308 || 351 || |
| 218 | || 5436 || 343 || |
| 219 | || 5564 || 561 || |
| 220 | || 5692 || 386 || |
| 221 | || 5820 || 355 || |
| 222 | || 5948 || 336 || |
| 223 | || 6076 || 444 || |
| 224 | || 6204 || 340 || |
| 225 | || 6332 || 203 || |
| 226 | || 6460 || 179 || |
| 227 | |
| 228 | This gives us an average RMS of 338 uJy. We can use this value when cleaning: |
| 229 | |
| 230 | ./dac_repeat.pl --task clean --repeat map --repeat-freq rnovalmc_%f.map --repeat beam --repeat-freq rnovalmc_%f.beam --repeat out --repeat-freq rnovalmc_%f.clean cutoff=0.001014 |
| 231 | |
| 232 | And restor: |
| 233 | |
| 234 | ./dac_repeat.pl --task restor --repeat model --repeat-freq rnovalmc_%f.clean --repeat beam --repeat-freq rnovalmc_%f.beam --repeat map --repeat-freq rnovalmc_%f.map --repeat out --repeat-freq rnovalmc_%f.restor |
| 235 | |