invert in MIRIAD and cellsize
Posted: Tue Aug 13, 2013 2:52 pm
Hi,
I've making I, Q and U cubes of CABB 5.5 GHz data, across the full 2 GHz band, so that we can investigate RM synthesis techniques in measuring the rotation measure of some sources.
I run invert with the folllowing (e.g. for U):
vis = ecdfs_fullband_6.5500.uv
map = ecdf_fullband_line10chan_6.umap
beam = ecdf_fullband_line10chan_6.ubeam
imsize = 1300
cell = 0.5
robust = 1
line = channel,200,5,10,10
stokes = u
options = systemp
slop = 1
The source of interest lies a little off the pointing centre (this is one of the mosaic pointings from my 42 pointing mosaic of eCDFS). For each plane or channel it has a different x,y position because the default of MIRIAD is to scale the cell size! As noted in the online MIRIAD manual this is okay when the fractional bandwidth is small, but we're talking about CABB at 5.5 GHz.
To run a RM synthesis code I need the source, or coordinates, in each x, y pixel to be the same in each plane or channel. That is, I need to have the cell size not scaled. Can you make an update to invert that allows one to turn off this cell size scaling?
Hopefully this is a simple hack and you can have a new version of invert available quickly?
thanks,
Minh
I've making I, Q and U cubes of CABB 5.5 GHz data, across the full 2 GHz band, so that we can investigate RM synthesis techniques in measuring the rotation measure of some sources.
I run invert with the folllowing (e.g. for U):
vis = ecdfs_fullband_6.5500.uv
map = ecdf_fullband_line10chan_6.umap
beam = ecdf_fullband_line10chan_6.ubeam
imsize = 1300
cell = 0.5
robust = 1
line = channel,200,5,10,10
stokes = u
options = systemp
slop = 1
The source of interest lies a little off the pointing centre (this is one of the mosaic pointings from my 42 pointing mosaic of eCDFS). For each plane or channel it has a different x,y position because the default of MIRIAD is to scale the cell size! As noted in the online MIRIAD manual this is okay when the fractional bandwidth is small, but we're talking about CABB at 5.5 GHz.
To run a RM synthesis code I need the source, or coordinates, in each x, y pixel to be the same in each plane or channel. That is, I need to have the cell size not scaled. Can you make an update to invert that allows one to turn off this cell size scaling?
Hopefully this is a simple hack and you can have a new version of invert available quickly?
thanks,
Minh