A3121  430 MHz mapping feb17

Last updated:sep17

    image of what's been done (jpeg)
    field with sources removed (jpeg)

directory holding fits files:

Links to Sections and Plots:

The steps in processing the data
Map positions raw data
    Plot: sampled map positions for each field (.ps) (.pdf).
    Plot: where all 4 fields fit into the final combined map (.ps) (.pdf).


Removing Tsys.

The individual maps by field
    The  average maps for each field (.gif)

Mosaicing the 4 fields together

The final mosaiced maps (.gif):

Notes on the fields:

Intro: (top)

   A3121 mapped 4  overlapping fields at 430 MHz using the gregorian. Data was sampled at 1 hz. Each field was covered in the ra and then the dec direction for basket weaving. The 12.5 MHz bands with 2048 channels were used to computed the total power.

    Data was taken feb,mar 2017

mapname map center
ra, dec
Field1 09:46:47.5, 25:54:59.9
Field2 09:26:48.5, 24:54:59.9
Field3 09:47:13.2, 30:24:59.9
Field4 09:26:22.8, 30:24:59.9

processing: usr/a3121/....

The steps in processing the data  (top)

    The steps in processing the data were:

Map positions   (top)

  The plots shows the sampled map positions for each field take for a3121 (.ps) (.pdf).
The next plot  shows where all 4 fields fit into the final combined map (.ps) (.pdf).
processing: chkalldata_pltpos.pro   ,getmappos.pro

Removing Tsys (top)

    We need to remove Tsys (excluding the sky contribution since that is what we want to measure). This is explained in a2125. It  includes:
Plots of Tsys for fields 1 thru 4 .
Some of these things will be fixed by the basket weaving.

The individual maps.  (top)

    After removing Tsys and scaling to janskies, each field was gridded. The process was:
  1. grid the ra driven and dec driven maps separately to the same grid.
  2. basketweave the two  maps. Create an average map and a difference map after basketweaving.
The  average maps for each field (.gif) show the results.

processing: lookimgidl.pro

Mosaicing the fields.  (top)

    The 4  fields from A31215 were combined into a single image. The processing to do this was:
  1. take each pair of overlapping maps.
  2. Interpolate the first map of each  pair to the grid position of the second  (within the overlap region).
  3. compute  mapRaDif=(map2 - interpolated Map1) in the overlap region
  4. Fit a linear polynomial to the differences as a function of the ra position
  5. Correct the two maps by subtracting half the difference from map2 and adding half the difference to map 1
  6. Repeat steps 1 5 with the corrected fields, using the dec overlap of the pairwise maps.
  7. 21feb11: changed so that 1-6 only corrects 20% of the difference. It then iterates 1-6 5 times. This gets rid of jumps caused by the correction.
The plots below show the pairwise difference of the overlap regions of the maps.
Processing: combinemaps_scl.pro

The final mosaiced maps (.gif):

The final mosaiced maps with positions (.gif)

Notes on the fields.  (top)