[daip] forwarded message from Enno Middelberg
Eric Greisen
egreisen at nrao.edu
Wed Sep 14 10:29:40 EDT 2005
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From: Enno Middelberg <enno.middelberg at csiro.au>
To: egreisen at nrao.edu
Subject: Aips problems
Date: Wed, 14 Sep 2005 11:59:50 +1000
Dear Eric Greisen,
I have tried to get some help with an Aips-related problem, but an email
sent to daip at nrao.edu on 31 August remained unanswered. Can you please
forward my email to the relevant person (or possibly look into this
yourself)?
Thanks very much,
Enno Middelberg
ATNF, Australia
================================================================
I have a VLBA spectral line data set and encounter two problems which I
am unable to solve. I have an experiment in which the water masers in
NGC3079 were observed with the VLBA using 256 channels in each of 8 IFs.
Each IF has a bandwidth of 8 MHz, and hence a channel has 31.25 kHz.
Problem 1
- ---------
I am trying to use SETJY to be able to convert frequencies into
velocities, but the way this has to be done seems laborious and
redundant. Using the "SYSVEL" parameter and APARM(1) one defines the
velocity of a given pixel. This requires that I calculate the velocity
for, eg, channel one in each of the eight IFs separately and use SETJY
eight times to set the velocity (this is the laborious part)!
Furthermore, as the observing date, the observing frequency and the line
rest frequency are known, the conversion to km/s in, eg, POSSM, should
be straight forward, and, once tested, less error-prone than my own
conversion. What am I missing?
Problem 2
- ---------
This is related to making an image cube from VLBA spectral line data. I
want to make an image cube from (nearly) all 2048 channels, with one
channel per plane, using IMAGR. I specify
BCHAN 2
ECHAN 255
CHANNEL 0
NCHAV 1
CHINC 0
BIF 1
EIF 8
and would expect that IMAGR takes channel 2 in IF1, then channel 3 in
IF1, and so on, until all channels in IF1 are done, and then starts with
channel 2 in IF2, and so on. But IMAGR averages channel 2 from _each_
IF, then channel 3 from each IF, etc, resulting in a cube with 255
planes. Here is some output from the message server:
(...)
IMAGR1: Beginning channel 95 through 95 with 8 IFs
IMAGR1: FNDPOL: Stokes I computed assuming V=0
IMAGR1: GRDMEM: Ave 8 Channels; 2.213722E+10 to 2.219321E+10 Hz
IMAGR1: Field 1 Sum of gridding weights = 8.65353E+05
IMAGR1: Field 1 Beam min = -92.8 MilliJy, max = 1.0 Jy
IMAGR1: Field 1 fit FWHM = 596.604 x 412.031 Microarcsec, PA= 6.8
IMAGR1: CLBHIS: minimum component 0.294 of current peak
IMAGR1: Field 1 min = -21.1 MilliJy,max = 21.3 MilliJy
IMAGR1: No Cleaning requested
IMAGR1: Beginning channel 96 through 96 with 8 IFs
IMAGR1: FNDPOL: Stokes I computed assuming V=0
IMAGR1: GRDMEM: Ave 8 Channels; 2.213725E+10 to 2.219324E+10 Hz
IMAGR1: Field 1 Sum of gridding weights = 8.65353E+05
IMAGR1: Field 1 Beam min = -92.8 MilliJy, max = 1.0 Jy
IMAGR1: Field 1 fit FWHM = 596.604 x 412.031 Microarcsec, PA= 6.8
IMAGR1: CLBHIS: minimum component 0.294 of current peak
IMAGR1: Field 1 min = -22.2 MilliJy,max = 20.8 MilliJy
IMAGR1: No Cleaning requested
(...)
The 3rd and 12th line give the frequency range over which the average is
done. It's 55.99 MHz, which corresponds to the frequency difference of,
eg, channel 95 in IF1 and channel 95 in IF8.
Hence, the image cube will have 255 planes, and each plane will be the
average of channels with the same number, but from different IFs.
How do I generate a cube with one channel _from one IF only_, per plane?
Will I need to make eight cubes and combine them somehow? I am using the
31DEC04 version, and I have pasted the data file header and the entire
inputs to IMAGR below.
I have spent considerable time on this problem already but was unable to
find a solution. Any hints to more information or documentation are
highly appreciated, but I believe this is not covered in the AIPS Cookbook.
data file header:
AIPS 1: Image=MULTI (UV) Filename=bm208b .FQ2 . 1
AIPS 1: Telescope=VLBA Receiver=VLBA
AIPS 1: Observer=BM208 User #= 28
AIPS 1: Observ. date=03-NOV-2004 Map date=15-JUL-2005
AIPS 1: # visibilities 66451 Sort order TB
AIPS 1: Rand axes: UU-L-SIN VV-L-SIN WW-L-SIN TIME1 BASELINE
AIPS 1: SOURCE FREQSEL INTTIM GATEID CORR-ID WEIGHT
AIPS 1: SCALE
AIPS 1: ----------------------------------------------------------------
AIPS 1: Type Pixels Coord value at Pixel Coord incr Rotat
AIPS 1: COMPLEX 1 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: STOKES 1 -2.0000000E+00 1.00 -1.0000000E+00 0.00
AIPS 1: FREQ 256 2.2134280E+10 1.00 3.1250000E+04 0.00
AIPS 1: IF 8 1.0000000E+00 1.00 1.0000000E+00 0.00
AIPS 1: RA 1 00 00 00.000 1.00 0.000000 0.00
AIPS 1: DEC 1 00 00 00.000 1.00 0.000000 0.00
AIPS 1: ----------------------------------------------------------------
Inputs to IMAGR:
AIPS 1: IMAGR: Wide field imaging/Clean task
AIPS 1: Adverbs Values Comments
AIPS 1: ----------------------------------------------------------------
AIPS 1: INNAME 'bm208b ' Input UV data (name)
AIPS 1: INCLASS 'FQ2 ' Input UV data (class)
AIPS 1: INSEQ 1 Input UV data (seq. #)
AIPS 1: INDISK 0 Input UV data disk drive #
AIPS 1: SOURCES 'NGC3079 ' Source name
AIPS 1: *rest ' '
AIPS 1: QUAL -1 Calibrator qualifier -1=>all
AIPS 1: CALCODE ' ' Calibrator code ' '=>all
AIPS 1: TIMERANG *all 0 Time range to use
AIPS 1: SELBAND -1 Bandwidth to select (kHz)
AIPS 1: SELFREQ -1 Frequency to select (MHz)
AIPS 1: FREQID 1 Freq. ID to select.
AIPS 1: SUBARRAY 0 Sub-array, 0=>all
AIPS 1: DOCALIB 1 If >0 calibrate data
AIPS 1: = 2 calibrate weights
AIPS 1: GAINUSE 5 CL (or SN) table to apply
AIPS 1: DOPOL -1 If >0.5 correct polarization.
AIPS 1: BLVER -1 BL table to apply.
AIPS 1: FLAGVER -1 Flag table version
AIPS 1: DOBAND 1 If >0.5 apply bandpass cal.
AIPS 1: Method used depends on value
AIPS 1: of DOBAND (see HELP file).
AIPS 1: BPVER 1 Bandpass table version
AIPS 1: SMOOTH *all 0 Smoothing function. See
AIPS 1: HELP SMOOTH for details.
AIPS 1: STOKES 'I ' Stokes parameters (see HELP)
AIPS 1: BCHAN 2 Low freq. channel 0 for cont.
AIPS 1: ECHAN 255 Highest freq channel
AIPS 1: CHANNEL 0 Restart channel number
AIPS 1: NCHAV 1 Number of chan. to average.
AIPS 1: CHINC 0 Channel incr. between maps.
AIPS 1: BIF 1 First IF in average.
AIPS 1: EIF 8 Last IF in average.
AIPS 1: OUTNAME 'N3079_CL5 ' Output image name (name)
AIPS 1: OUTDISK 0 Output image disk drive #
AIPS 1: OUTSEQ 0 Output seq. no.
AIPS 1: OUTVER 1 CC ver. no (Continuum only)
AIPS 1: *** SET OUTVER ON RESTARTS
AIPS 1: IN2NAME ' ' UV work file name
AIPS 1: IN2CLASS ' ' UV work file class
AIPS 1: IN2SEQ 0 UV work file seq
AIPS 1: *** SET TO KEEP WORK FILE
AIPS 1: IN2DISK 0 UV work file disk
AIPS 1: CELLSIZE 1.000E-04 1.000E-04 (X,Y) size of grid in asec
AIPS 1: IMSIZE 512 512 Minimum image size
AIPS 1: NFIELD 1 Number of fields (max 4096)
AIPS 1: DO3DIMAG -1 > 0 => use different tangent
AIPS 1: points for each field
AIPS 1: FLDSIZE *all 0 Clean size of each field.
AIPS 1: RASHIFT *all 0 RA shift per field (asec)
AIPS 1: DECSHIFT *all 0 DEC shift per field (asec)
AIPS 1: UVTAPER 0 0 (U,V) Gaussian taper
AIPS 1: units are kilo-lambda
AIPS 1: UVRANGE 0 0 Min & max baseline (klambda)
AIPS 1: GUARD 0 0 x,y guard band fractional
AIPS 1: radius
AIPS 1: ROTATE 0 Rotate image CCW from N by
AIPS 1: ROTATE degrees
AIPS 1: ZEROSP *all 0 0-spacing fluxes and weights
AIPS 1: SEE HELP!!
AIPS 1: UVWTFN 'N ' UV dist. weight function
AIPS 1: blank => uniform
AIPS 1: UVSIZE 0 0 Array size for doing uniform
AIPS 1: weights. 0 -> actual field
AIPS 1: size.
AIPS 1: ROBUST 0 Robustness power: -5 -> pure
AIPS 1: uniform weights, 5 => natural
AIPS 1: UVBOX 0 Additional rows and columns
AIPS 1: used in weighting.
AIPS 1: UVBXFN 1 Box function type when UVBOX
AIPS 1: > 0. 0 -> 1 round pill box.
AIPS 1: XTYPE 5 Conv. function type in x
AIPS 1: default spheroidal
AIPS 1: YTYPE 5 Conv. function type in y
AIPS 1: default spheroidal
AIPS 1: XPARM *all 0 Conv. function parms for x
AIPS 1: YPARM *all 0 Conv. function parms for y
AIPS 1: NITER 0 Maximum # of Clean components
AIPS 1: BCOMP *all 0 Begin at BCOMP component
AIPS 1: Specify for each field.
AIPS 1: ALLOKAY 0 For restart: > 0 => beams
AIPS 1: okay, > 1 => work file too
AIPS 1: NBOXES 0 Number of boxes for Clean
AIPS 1: NB: field 1 only.
AIPS 1: CLBOX *all 0 Four coordinates for each box
AIPS 1: BOXFILE *all ' ' Input file of field params
AIPS 1: and Clean boxes; ' ' => use
AIPS 1: FLDSIZE, RASHIFT, DECSHIFT,
AIPS 1: NBOXES, CLBOX only.
AIPS 1: OBOXFILE *all ' ' Output file for final Clean
AIPS 1: boxes
AIPS 1: GAIN 0.05 Clean loop gain
AIPS 1: FLUX -1 Minimum Clean component (Jy)
AIPS 1: MINPATCH 51 Min. BEAM half-width in AP.
AIPS 1: BMAJ 0 FWHM(asec) major axis Clean
AIPS 1: restoring beam.
AIPS 1: BMIN 0 FWHM(asec) minor axis Clean
AIPS 1: restoring beam.
AIPS 1: BPA 0 Clean beam position angle
AIPS 1: OVERLAP 0 1 => restore components to
AIPS 1: overlapped fields, >=2=>
AIPS 1: expect overlaps in Cleaning
AIPS 1: PHAT 0 Prussian hat height.
AIPS 1: FACTOR 0 Speedup factor see HELP
AIPS 1: CMETHOD ' ' Modeling method:
AIPS 1: 'DFT','GRID',' '
AIPS 1: IMAGRPRM *all 0 Task enrichment parameters
AIPS 1: (1) Antenna diameter (m)
AIPS 1: (2) Source Spectral index
AIPS 1: (3) Frequency scaling factor
AIPS 1: (4) > 0 -> SDI Clean factor
AIPS 1: (5) >0 => scale residuals
AIPS 1: (6) Half-width in x of box
AIPS 1: (7) Half-width in y of box
AIPS 1: (8) Filter components whose
AIPS 1: neighborhood is weaker than
AIPS 1: IMAGRPRM(8) Jy. 0 -> don't
AIPS 1: (9) Radius in pixels for the
AIPS 1: IMAGRPRM(8) test.
AIPS 1: (10) multiplier of image size
AIPS 1: to get beam size: 0 => 2;
AIPS 1: 2, 1, 0.5 0.25 supported
AIPS 1: (11-16) Multi-resolution
AIPS 1: added controls
AIPS 1: (19) Dynamic range limit
AIPS 1: (20) Retry factor (see help)
AIPS 1: NGAUSS 0 Number of resolutions to use
AIPS 1: WGAUSS *all 0 Resolutions in arc sec >= 0
AIPS 1: FGAUSS *all 0 Minimum flux for each resol.
AIPS 1: MAXPIXEL 0 Maximum pixels searched in
AIPS 1: each major cycle.
AIPS 1: DOTV -1 Display residuals on TV ?
AIPS 1: Start with field = DOTV
AIPS 1: BADDISK *all 0 Disks to avoid for scratch.
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