A2415  430 MHz mapping aug09 

Last updated:22feb11

image of fields mapped to 22feb11

26oct10: links to images removed till jun11 when data becomes public. to see images
contact phil.

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

Links to Sections and Plots:

The steps in processing the data
Map positions raw data
    Plot: sampled map positions for each field (.ps) (.pdf).

Removing Tsys.

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

Mosaicing the 11 + 4 maps together

The final mosaiced maps (.gif):

Notes on the fields:

Intro: (top)

   A2415 mapped 9 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. After processing the data the polA data showed instabilities, so the maps,images were only made with the polB data. The 4 maps made for a2125 were also included in the mosaicing.

    Data was taken aug-dec09 and dec10. The a2125 data was then included in the final combined map.

mapname map center
ra, dec
date taken
Field1 00:51:00, 35:15:0
Field2 01:10:30, 35:15:00
Field3 01:09:30, 31:57:00
Field4 01:08:30, 38:15:00
01:07:30, 24:27:00
00:50:30, 24:27:00
00:16:20, 26:05:00
01:27:20, 31:21:00
01:26:30, 28:15:00
01:25:00, 25:09:00
a2125 fields (_05 added to fieldname)

00:50:38 , 23:31:00
Field2_05 00:34:42  , 28:31:00
Field3_05 00:50:55 , 32:01:00
Field4_05 00:34:25 , 32:01:00

processing: usr/a2415/aug09/

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 (.ps) (.pdf).
processing: chkalldata_pltpos.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 14.
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: aug09/lookimgidl.pro

Mosaicing the fields.  (top)

    The 11 fields from a2415 plus the 4 fields of a2125 were to be 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 interates 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)