Difference between revisions of "Antennae Band7 - Imaging for CASA 3.3"

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</source>
 
</source>
  
*fitspw='0:5~50,0:120~164': line-free channels
+
*fitspw='0:5~50,0:120~164': Line-free channels
*fitorder = 1:  first-order polynomial
+
*fitorder = 1:  First-order polynomial
*fitmode = 'subtract': subtract the continuum from all channels. Note that the result is stored in the CORRECTED_DATA column
+
*fitmode = 'subtract': Subtract the continuum from all channels. Note that the result is stored in the CORRECTED_DATA column
 
 
 
Next, we {{clean}} the CO(3-2) line emission. We obtain the dirty map first with {{clean}} and niter=0:
 
Next, we {{clean}} the CO(3-2) line emission. We obtain the dirty map first with {{clean}} and niter=0:
Line 177: Line 177:
 
</source>
 
</source>
  
The threshold is ~ 1.5 the rms of the line-free channel for each dataset.
+
The threshold is ~ 1.5 the rms of the line-free channel for each dataset. We double the imsize of the southern mosaic to increase the dirty beam, as the emission is quite extended along the mosaic. Using interactive=T the viewer will open when it is ready to start an interactive clean. Step through to the channels to see how extended the emission is. Then either use  "All Channels" to define the same clean mask for all channels, or select "This Channel" to select different masks for each channel. Once you have defined a polygon region, you need to double click inside it to save the mask region. You can use the "tape deck" to step through the channels again and check that the emission in all channels fits within the mask(s) you have created. Note that the mask we defined above does not include all emission -- you will have to change the mask interactively!
Using interactive=T the viewer will open when it is ready to start an interactive clean. Step through to the channels to see how extended the emission is. Then either use  "All Channels" to define the same clean mask for all channels, or select "This Channel" to select different masks for each channel. Once you have defined a polygon region, you need to double click inside it to save the mask region. You can use the "tape deck" to step through the channels again and check that the emission in all channels fits within the mask(s) you have created. Note that the mask we defined above does not include all emission -- you will have to change the mask interactively!
 
 
To continue with clean use the "Next action" buttons in the green area on the Viewer Display GUI: The red X will stop clean where you are; the blue arrow will stop the interactive part of clean, but continue to clean non-interactively until reaching the stopping niter or threshold (whichever comes first); and the green arrow will clean until it reaches the "iterations" parameter on the left side of the green area.
 
To continue with clean use the "Next action" buttons in the green area on the Viewer Display GUI: The red X will stop clean where you are; the blue arrow will stop the interactive part of clean, but continue to clean non-interactively until reaching the stopping niter or threshold (whichever comes first); and the green arrow will clean until it reaches the "iterations" parameter on the left side of the green area.
  
Line 190: Line 189:
  
 
==== Moment maps ====
 
==== Moment maps ====
Next, we make the moment maps of the CO(1-0) emission using the task {{immoments}}:
+
Next, we make the integrated intensity maps and velocity fields of the CO(3-2) emission using the task {{immoments}}. Note that we choose to  run the {{immoments}} separately for the total intensity map and the velocity field because we want to use different flux thresholds.
 
   
 
   
 
<source lang="python">
 
<source lang="python">
 
# In CASA
 
# In CASA
os.system('rm -rf result-ngc3256_CO1-0.mom0*')
 
immoments(imagename='result-ngc3256_line_CO.image', moments=[0],
 
chans='15~34', box='38,38,90,90', axis='spectral',
 
includepix=[0.02, 10000], outfile='result-ngc3256_CO1-0.mom0')
 
</source>
 
  
<source lang="python">
+
#Mom0 Northern
# In CASA
+
rm -rf Antennae_North.Line.Clean.Mom.image*  
os.system('rm -rf result-ngc3256_CO1-0.mom1*')
+
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[0],outfile='Antennae_North.Line.Clean.Mom.image.integrated')
immoments(imagename='result-ngc3256_line_CO.image', moments=[1],
+
imview (raster={'file': 'Antennae_North.Line.Clean.Mom.image.integrated'},out='Antennae_North.Line.Clean.Mom.image.integrated.png')
chans='15~34', box='38,38,90,90', axis='spectral',
 
includepix=[0.045, 10000], outfile='result-ngc3256_CO1-0.mom1')
 
</source>
 
  
[[File:CO_velfield.png|200px|thumb|right|The CO(1-0) velocity field of NGC3256, with contours of the total line emission map overlaid]]
+
#Mom1 Northern
[[File:CO_map.png|200px|thumb|right|The CO(1-0) "moment 0" total intensity maps of NGC3256, with contours of the velocity field overlaid]]
+
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[1],outfile='Antennae_North.Line.Clean.Mom.Mask.image.weighted_coord',mask="Antennae_North.Line.Clean.image>3.5e-2")
[[File:result-CO_dispersion.png|200px|thumb|right|The CO(1-0) "moment 2" dispersion map of NGC3256]]
+
imview (raster={'file': 'Antennae_North.Line.Clean.Mom.Mask.image.weighted_coord','range': [1500,1750]},out='Antennae_North.Line.Clean.Mom.Mask.image.velfield.png')
*moments=[x]: To specify that we wish to make the xth moment map. The 0th moment map gives integrated emission and the 1st gives the intensity-weighted velocity field
 
*chans='15~34': These are the channels that show line emission and therefore the ones we want to use for the moment map
 
*box='38,38,90,90': To select a box region around the emission so as to not include any regions away from the galaxy
 
*axis='spectral': Indicates the moment axis; in this case, 'spectral'  
 
*includepix=[0.045, 10000]: To select which pixel values in the cube to include in the moments. We find these values by looking for the faintest believable emission in the cube
 
*outfile='result-ngc3256_CO1-0.mom0': The output image name
 
  
Here, we have chosen to  run the {{immoments}} separately for the total intensity map and the velocity field because we want to use different thresholds for flux inclusion. To find the lower limit in includepix, open the cube in the viewer, and identify the lowest believable flux levels in the cube.
+
#Mom0 Southern
 +
rm -rf Antennae_South.Line.Clean.Mom.image*
 +
immoments('Antennae_South.Line.Clean.image', axis="spec", moments=[0],outfile='Antennae_South.Line.Clean.Mom.image.integrated')
 +
imview (raster={'file': 'Antennae_South.Line.Clean.Mom.image.integrated'},out='Antennae_South.Line.Clean.Mom.image.integrated.png')
  
We also make a velocity dispersion map of the CO(1-0) gas, using moments=[2]
+
#Mom1 Southern
 +
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[1],outfile='Antennae_South.Line.Clean.Mom.Mask.image.weighted_coord',mask="Antennae_South.Line.Clean.image>2.5e-2")
 +
imview (raster={'file': 'Antennae_South.Line.Clean.Mom.Mask.image.weighted_coord','range': [1300,1900]},out='Antennae_South.Line.Clean.Mom.Mask.image.velfield.png')
  
<source lang="python">
 
# In CASA
 
os.system('rm -rf result-ngc3256_CO1-0.mom2*')
 
immoments(imagename='result-ngc3256_line_CO.image', moments=[2],
 
chans='5~44', box='38,38,90,90', axis='spectral',
 
includepix=[0.035, 10000], outfile='result-ngc3256_CO1-0.mom2')
 
 
</source>
 
</source>
  
Now we can make images of the CO(1-0) emission. First create a colour image of the velocity field, with contours of the total line emission overlaid:
+
[[File:Antennae_North.Line.Clean.Mom.image.integrated.png|200px|thumb|right|The CO(3-2)  total intensity map (moment 0)  of the northern mosaic]]
 +
[[File:Antennae_North.Line.Clean.Mom.Mask.image.velfield.png|200px|thumb|right|The CO(3-2) velocity field (moment 1) of the northern mosaic]]
 +
[[File:Antennae_South.Line.Clean.Mom.image.integrated.png|200px|thumb|right|The CO(3-2)  total intensity map (moment 0) of the southern mosaic]]
 +
[[File:Antennae_South.Line.Clean.Mom.Mask.image.velfield.png|200px|thumb|right|The CO(3-2) velocity field (moment 1) of the southern mosaic]]
  
<source lang="python">
+
*moments=[x]: To specify that we wish to make the xth moment map. The 0th moment map gives integrated emission and the 1st gives the intensity-weighted velocity field
# In CASA
+
*axis='spectral': Indicates the moment axis; in this case, 'spectral'  
imview(contour={'file': 'result-ngc3256_CO1-0.mom0','levels':
+
*mask="Antennae_North.Line.Clean.image>X" Mask applied to the image before calculating the moments. Consider pixels in Antennae_North.Line.Clean.image that are larger than X
      [5,10,20,40,80,160],'base':0,'unit':1},
+
*outfile='result-ngc3256_CO1-0.mom0': The output image name
      raster={'file': 'result-ngc3256_CO1-0.mom1','range': [2630,2920],
 
      'colorwedge':T, 'colormap': 'Rainbow 2'}, out='result-CO_velfield.png')
 
</source>
 
 
 
Or, make a colour image of the integrated CO(1-0) line emission, with contours of the velocity field overlaid:
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CO1-0.mom1','levels':
 
        [2650,2700,2750,2800,2850,2900],'base':0,'unit':1},
 
        raster={'file': 'result-ngc3256_CO1-0.mom0', 'colorwedge':T,
 
        'colormap': 'Rainbow 2','scaling':-1.0,'range': [0.8,250]},
 
        out='result-CO_map.png')
 
</source>
 
 
 
And make a greyscale image of the CO(1-0) gas velocity dispersion
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CO1-0.mom2','levels':
 
        [20,30,40,50,60],'base':0,'unit':1},
 
        raster={'file': 'result-ngc3256_CO1-0.mom2', 'colorwedge':T,
 
        'colormap': 'Greyscale 1','scaling':-1.0,'range': [0,74]},
 
        out='result-CO_dispersion.png')
 
</source>
 
 
 
[[File:ngc3256_channels.png|200px|thumb|right|Channel maps of six central channels, with contours of the total continuum map overlaid]]
 
Also, using the viewer, it is possible to make channel maps. The following image shows six velocity channels, with contours indicating the 3mm continuum emission.
 
 
 
Next, we clean the CN line emission. There are two CN lines, the N=1-0, J=3/2-1/2 line at higher frequency and the N=1-0, J=1/2-1/2 line at lower frequency. We start with the higher frequency line emission. Again, we have set a mask here, but the best results are obtained if an interactive clean mask is defined.
 
 
<source lang="python">
 
# In CASA
 
os.system('rm -rf result-ngc3256_line_CNhi.*')
 
clean(vis='ngc3256_line_target_sc.ms', imagename='result-ngc3256_line_CNhi',
 
outframe='LSRK', spw='1:50~76', start='', nchan=27, width='',
 
restfreq='113.48812GHz', selectdata=T, mode='channel',
 
niter=500, gain=0.1, psfmode='hogbom', mask=[53,50,87,83],
 
interactive=True, imsize=128, cell='1arcsec',
 
weighting='briggs', robust=0.0, threshold='2mJy')
 
</source>
 
 
 
Make the moment maps of the higher frequency CN line emission:
 
 
<source lang="python">
 
# In CASA
 
os.system('rm -rf result-ngc3256_CNhi.mom.*')
 
immoments( imagename='result-ngc3256_line_CNhi.image', moments=[0,1],
 
chans='5~18', axis='spectral', box='38,38,90,90',
 
includepix=[0.005, 10000], outfile='result-ngc3256_CNhi.mom')
 
</source>
 
 
 
Make images of the higher frequency CN line emission:
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CNhi.mom.integrated','range': []},
 
        raster={'file': 'result-ngc3256_CNhi.mom.weighted_coord',
 
        'range': [2630,2920],'colorwedge':T,
 
        'colormap': 'Rainbow 2'}, out='result-CNhi_velfield.png')
 
</source>
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CNhi.mom.weighted_coord','levels':
 
      [2650,2700,2750,2800,2850,2900],'base':0,'unit':1},
 
      raster={'file': 'result-ngc3256_CNhi.mom.integrated','colorwedge':T,
 
      'colormap': 'Rainbow 2'}, out='result-CNhi_map.png')
 
</source>
 
 
 
And finally, clean the CN (N=1-0, J=1/2-1/2) emission:
 
 
<source lang="python">
 
# In CASA
 
os.system('rm -rf result-ngc3256_line_CNlo.*')
 
clean( vis='ngc3256_line_target_sc.ms', imagename='result-ngc3256_line_CNlo',
 
outframe='LSRK', spw='1:29~54', start='', nchan=26, width='',
 
restfreq='113.17049GHz', selectdata=T, mode='channel',
 
niter=300, gain=0.1, psfmode='hogbom', mask=[53,50,87,83],
 
interactive=True, imsize=128, cell='1arcsec',
 
weighting='briggs', robust=0.0, threshold='2mJy')
 
</source>
 
 
 
Make the moment maps of the lower frequency CN emission
 
 
<source lang="python">
 
# In CASA
 
os.system('rm -rf result-ngc3256_CNlo.mom.*')
 
immoments( imagename='result-ngc3256_line_CNlo.image', moments=[0,1],
 
chans='8~18', axis='spectral', box='38,38,90,90',
 
includepix=[0.003, 10000], outfile='result-ngc3256_CNlo.mom')
 
</source>
 
 
 
Make images of the low frequency CN emission
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CNlo.mom.integrated','range': []},
 
        raster={'file': 'result-ngc3256_CNlo.mom.weighted_coord',
 
        'range': [2630,2920],'colorwedge':T,
 
        'colormap': 'Rainbow 2'}, out='result-CNlo_velfield.png')
 
</source>
 
 
 
<source lang="python">
 
# In CASA
 
imview(contour={'file': 'result-ngc3256_CNlo.mom.weighted_coord','levels':
 
        [2650,2700,2750,2800,2850,2900],'base':0,'unit':1},
 
        raster={'file': 'result-ngc3256_CNlo.mom.integrated','colorwedge':T,
 
        'colormap': 'Rainbow 2'}, out='result-CNlo_map.png')
 
</source>
 
 
 
This composite shows the CN maps and velocity fields.
 
 
 
<gallery widths="280px" heights="200px" perrow="2">
 
File:result-CNhi_map.png|The higher frequency CN(1-0) "moment 0" total intensity maps of NGC3256, with contours of the velocity field overlaid
 
File:result-CNhi_velfield.png|The higher frequency CN(1-0) velocity field of NGC3256, with contours of the total line emission map overlaid
 
File:result-CNlo_map.png|The lower frequency CN(1-0) "moment 0" total intensity maps of NGC3256, with contours of the velocity field overlaid
 
File:result-CNlo_velfield.png|The lower frequency CN(1-0) velocity field of NGC3256, with contours of the total line emission map overlaid
 
</gallery>
 
  
And finally we show the channel maps of all three emission lines overlaid. The 'hot metal' colours represent the higher frequency CN line, the green contours are the CO line, and the cyan contours are the lower frequency CN line.
 
  
[[File:composite_channels.png|600px|thumb|left|Channel maps of all three lines]]
 
  
 
[[User:Despada|Daniel Espada]] 12:00 UT, 14 July 2011
 
[[User:Despada|Daniel Espada]] 12:00 UT, 14 July 2011

Revision as of 02:34, 20 July 2011


Overview

This section of the AntennaeBand7 CASA Guide cover the imaging of the continuum and spectral line data. It begins where the Antennae Band7 - Calibration section left off. If you completed the Calibration section of the guide, then you may want to continue with the calibrated data sets Antennae_South.ms and Antennae_North.ms. If you did not complete the Calibration section, then you can download the calibrated uv-data from the region closest to your location:

North America

Europe

East Asia

Once there, download the file 'Antennae_Band7_CalibratedData.tgz' to obtain the calibrated uvdata.

Once the download has finished, unpack the file:

# In a terminal outside CASA
tar -xvzf Antennae_Band7_CalibratedData.tgz

cd Antennae_Band7_CalibratedData

# Start CASA
casapy

After that, you should have Antennae_South.ms and Antennae_North.ms in your working directory.

Continuum map

We will make 345 GHz continuum images for the two regions covered by the mosaics. We use the task clean over the channels that are free of the line emission. The line-free channels are found by plotting the average spectrum. We find the CO(3-2) line from channels 50 to 100 in the southern mosaic, and from 70 to 100 in the northern mosaic.

Southern mosaic: Amplitude vs. channel. The CO(3-2) line is seen from 50 to 100
Northern mosaic: Amplitude vs. channel. The CO(3-2) line is seen from 70 to 100
# In CASA
plotms(vis='Antennae_South.cal.ms',xaxis='channel',yaxis='amp',
      avgtime='1e8',avgscan=T)
plotms(vis='Antennae_North.cal.ms',xaxis='channel',yaxis='amp',
      avgtime='1e8',avgscan=T)

The avgtime is set to a large value so that it averages over all the integrations, and avgscan is set to allow averaging of the different scans.

Next we create the continuum emission map. We use the default non-interactive mode and niter=0 as a first step to see if there is any continuum emission. The resolution in Band 7 for the extended configuration is approximately 1 arcsec. We therefore choose a cell size of 0.2 arcsec to oversample the beam sufficiently (at least three times). Note that we need to delete any previous clean output images before proceeding with the clean command, otherwise CASA will clean the data further instead of producing new output images.

For the northern mosaic:

345 GHz continuum image of the northern mosaic
345 GHz continuum image of the southern mosaic
# In CASA
os.system('rm -rf Antennae_North.Cont.Clean*')

clean(vis='Antennae_North.cal.ms',imagename='Antennae_North.Cont.Clean',
     field='',phasecenter='12',
     mode='mfs',restfreq='345.79599GHz',
     spw='0:0~50,0:120~164',
     imagermode='mosaic',
     imsize=500,cell='0.2arcsec',
     interactive=F,
     niter=1000, threshold='0.5mJy')

The input parameters include:

  • vis='Antennae_North.cal.ms': The calibrated dataset on the science target
  • imagename='Antennae_North.Cont.Clean': The base name of the output images
  • phasecenter='12': the source id of the mosaic.
  • spw='0:0~50,0:120~164': To specify only the line-free channels
  • mode='mfs': Multi-Frequency Synthesis: The default mode, which produces one image from all the specified data combined
  • niter=1000: Maximum number of clean iterations
  • theshold='0.5mJy': Stop cleaning if the maximum residual is below this value (~1.5 times the rms noise)
  • imsize=500, cell='0.2arcsec': Image size in pixels, chosen to cover the mosaic, and the cell size per pixel in arcsec to properly sample the synthesized beam (at least three times).

For the southern mosaic we modify the phase center and the line-free channels:

# In CASA
os.system('rm -rf Antennae_South.Cont.Clean*')

clean(vis='Antennae_South.cal.ms',imagename='Antennae_South.Cont.Clean',
     field='',phasecenter='15',
     mode='mfs',restfreq='345.79599GHz',
     spw='0:0~30,0:120~164',
     imagermode='mosaic',
     imsize=500,cell='0.2arcsec',
     interactive=F,
     niter=1000, threshold='0.5mJy')

The Half Power Beam Width (HPBW) of the elliptical synthesized beam is:

  • Northern mosaic: 1.28" times 0.66", with a position angle (PA) equal to 86 deg.
  • Southern mosaic: 1.15" times 0.66", and PA equal to 68 deg.


We will determine some statistics for the images using the task imstat:

# In CASA
imstat('Antennae_North.Cont.Clean.image')
imstat('Antennae_South.Cont.Clean.image')

The peak flux densities of the images are ~4.4 and 2.9 mJy for the southern and northern mosaics, and both have a similar rms ~ 0.3 mJy, thus the obtained dynamic ranges are larger or equal than 10.

Line cubes of the galaxy

First, we subtract the continuum emission in the uv-domain using the task uvcontsub.

# In CASA

uvcontsub(vis = 'Antennae_North.cal.ms',
	  fitspw='0:5~50,0:120~164', solint ='inf', 
	  fitorder = 1, fitmode = 'subtract')

uvcontsub(vis = 'Antennae_South.cal.ms',
	  fitspw='0:5~30,0:120~164', solint ='inf', 
	  fitorder = 1, fitmode = 'subtract')
  • fitspw='0:5~50,0:120~164': Line-free channels
  • fitorder = 1: First-order polynomial
  • fitmode = 'subtract': Subtract the continuum from all channels. Note that the result is stored in the CORRECTED_DATA column

Next, we clean the CO(3-2) line emission. We obtain the dirty map first with clean and niter=0:

# In CASA
os.system('rm -rf Antennae_North.Line,Antennae_South.Line*')
clean(vis='Antennae_North.cal.ms',imagename='Antennae_North.Line.Clean',
     spw='0',field='',phasecenter='12',
     mode='velocity',outframe='LSRK',restfreq='345.79599GHz',
     nchan=60,start='1300km/s',width='10km/s',
     imagermode='mosaic',
     imsize=500,cell='0.2arcsec',
     interactive=T,
     niter=0)

clean(vis='Antennae_South.cal.ms',imagename='Antennae_South.Line.Clean',
     spw='0',field='',phasecenter='15',
     mode='velocity',outframe='LSRK',restfreq='345.79599GHz',
     nchan=60,start='1300km/s',width='10km/s',
     imagermode='mosaic',
     imsize=500,cell='0.2arcsec',
     interactive=T,
     niter=0)
One of the channels in the interactive clean, showing CO emission. The white region indicates the clean mask

Notable parameters include:

  • mode='velocity',outframe='LSRK',restfreq='345.79599GHz',nchan=60,start='1300km/s',width='10km/s': To produce a data cube specified by the number of channels("nchan"=60), and "start" and "width" local standard of rest velocities (starting at 1300 km/s and with velocity widths of 10 km/s). The rest frequency of the CO line is used.
  • start='', nchan=31, width='': To include all 31 channels specified by spw, with no channel averaging
  • niter=0: Maximum number of clean iterations.

The (line-free) channel rms for the northern and southern mosaics are 2.7 mJy/beam and 2.4 mJy/beam, respectively, for 2.3 and 3.8 hours times on source approximately. The ALMA sensitivity calculator gives an on-source observing time of ~3-4 hours to reach a noise level of 2.5 mJy using 12 antennas for an angular resolution of 1. Note that the fields are overlapping by 0.5 the size of the primary beam.

We modify the following keywords to clean the mosaics:

# In CASA
minpb=0.2
interactive=T: To do interactive cleaning with the viewer GUI 

#For the Northern mosaic
threshold='4.0mJy'

#For the Southern mosaic
threshold='3.5mJy',
imsize=1000

*minpb=0.2
*interactive=T: To do interactive cleaning with the viewer GUI (read more about this below)
*threshold='5 mJy': Stop cleaning if the maximum residual is below this value.

The threshold is ~ 1.5 the rms of the line-free channel for each dataset. We double the imsize of the southern mosaic to increase the dirty beam, as the emission is quite extended along the mosaic. Using interactive=T the viewer will open when it is ready to start an interactive clean. Step through to the channels to see how extended the emission is. Then either use "All Channels" to define the same clean mask for all channels, or select "This Channel" to select different masks for each channel. Once you have defined a polygon region, you need to double click inside it to save the mask region. You can use the "tape deck" to step through the channels again and check that the emission in all channels fits within the mask(s) you have created. Note that the mask we defined above does not include all emission -- you will have to change the mask interactively! To continue with clean use the "Next action" buttons in the green area on the Viewer Display GUI: The red X will stop clean where you are; the blue arrow will stop the interactive part of clean, but continue to clean non-interactively until reaching the stopping niter or threshold (whichever comes first); and the green arrow will clean until it reaches the "iterations" parameter on the left side of the green area.

When the cleaning has finished, you may want to inspect the resulting data cube

imview (raster={'file': 'Antennae_North.Line.Clean.image'})
imview (raster={'file': 'Antennae_South.Line.Clean.image'})


Moment maps

Next, we make the integrated intensity maps and velocity fields of the CO(3-2) emission using the task immoments. Note that we choose to run the immoments separately for the total intensity map and the velocity field because we want to use different flux thresholds.

# In CASA

#Mom0 Northern
rm -rf Antennae_North.Line.Clean.Mom.image* 
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[0],outfile='Antennae_North.Line.Clean.Mom.image.integrated')
imview (raster={'file': 'Antennae_North.Line.Clean.Mom.image.integrated'},out='Antennae_North.Line.Clean.Mom.image.integrated.png')

#Mom1 Northern
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[1],outfile='Antennae_North.Line.Clean.Mom.Mask.image.weighted_coord',mask="Antennae_North.Line.Clean.image>3.5e-2")
imview (raster={'file': 'Antennae_North.Line.Clean.Mom.Mask.image.weighted_coord','range': [1500,1750]},out='Antennae_North.Line.Clean.Mom.Mask.image.velfield.png')

#Mom0 Southern
rm -rf Antennae_South.Line.Clean.Mom.image* 
immoments('Antennae_South.Line.Clean.image', axis="spec", moments=[0],outfile='Antennae_South.Line.Clean.Mom.image.integrated')
imview (raster={'file': 'Antennae_South.Line.Clean.Mom.image.integrated'},out='Antennae_South.Line.Clean.Mom.image.integrated.png')

#Mom1 Southern
immoments('Antennae_North.Line.Clean.image', axis="spec", moments=[1],outfile='Antennae_South.Line.Clean.Mom.Mask.image.weighted_coord',mask="Antennae_South.Line.Clean.image>2.5e-2")
imview (raster={'file': 'Antennae_South.Line.Clean.Mom.Mask.image.weighted_coord','range': [1300,1900]},out='Antennae_South.Line.Clean.Mom.Mask.image.velfield.png')
The CO(3-2) total intensity map (moment 0) of the northern mosaic
The CO(3-2) velocity field (moment 1) of the northern mosaic
The CO(3-2) total intensity map (moment 0) of the southern mosaic
The CO(3-2) velocity field (moment 1) of the southern mosaic
  • moments=[x]: To specify that we wish to make the xth moment map. The 0th moment map gives integrated emission and the 1st gives the intensity-weighted velocity field
  • axis='spectral': Indicates the moment axis; in this case, 'spectral'
  • mask="Antennae_North.Line.Clean.image>X" Mask applied to the image before calculating the moments. Consider pixels in Antennae_North.Line.Clean.image that are larger than X
  • outfile='result-ngc3256_CO1-0.mom0': The output image name


Daniel Espada 12:00 UT, 14 July 2011