Public parameter group NMODEL
This document contains an overview of the public parameter group NMODEL, (part of) which is included in all those NEWSTAR programs that manipulate models in .MDL and/or .SCN files.
The document describes the individual parameters in alphabetical order. This description centers on the Help texts, which have been designed to guide the user to the proper choice at each junction, even if his knowledge of the overall workings of the program is only superficial.
Please note that the generic prompt and help texts defined for these parameters are frequently superseded in the actual applications by alternative texts that are more appropriate to the situation at hand. Unfortunately, the present architecture of NEWSTAR precludes the inclusion of such texts in the documentation system, so the only opportunity to read that information is during program execution (in your terminal window!).
Prompt: Beam descriptors (may vary per application)
Expected input: Integer: 1 to 32 values
Describe the primary beam for an instrument other than the WSRT or the ATCA. Here you specify the formula to be used; later you will be asked for values for the coefficients.
Each instrument (up to 8) is decribed by four numbers, with (in order) the following meaning:
- the value of the * in BEAM_FREQ_* and BEAM_FACTOR_* to use
- the type of formula:
0= cos(factor*freq(MHz)*angle(degree))**6;
1= 1/(1+fac1*(freq(GHz)*angle(arcmin))**2+fac2*...);
2= 1+fac1*(freq(GHz)*angel(arcmin))**2+fac2*...)
- the number of factors per frequency range in BEAM_FACTOR_*
- the number of frequency ranges specified in BEAM_FREQ_*
Instruments are: first WSRT, second ATCA
Prompt: Beam feed factors (may vary per application)
Expected input: Real: 1 to 64 values
Specify per frequency band specified in BEAM_FREQ_0 the factors to be used in the primary beam calculation formula (see BEAM_DESCR). This is for WSRT cos**6
Prompt: Beam feed factors (may vary per application)
Expected input: Real: 1 to 64 values
Specify per frequency band specified in BEAM_FREQ_1 the factors to be used in the primary beam calculation formula (see BEAM_DESCR). This is for ATCA 1/(1+ai.x**2i)
Prompt: Beam feed frequencies (may vary per application)
Expected input: Real: 1 to 8 values
Specify in increasing order the frequency bands to be used in calculating the primary beam. For each value there should be a corresponding set of values in BEAM_FACTOR_0 (the number of values in BEAM_DESCR).These factors will be used up to the corresponding frequency specified.
Prompt: Beam feed frequencies (may vary per application)
Expected input: Real: 1 to 8 values
Specify in increasing order the frequency bands to be used in calculating the primary beam. For each value there should be a corresponding set of values in BEAM_FACTOR_1 (the number of values in BEAM_DESCR).These factors will be used up to the specified corresponding frequency (MHz).
Prompt: Scale factor for primary-beam width (may vary per application)
Expected input: Real: 1 value
Specify a scaling factor for the primary beam calculations. If, e.g. a beam has been defined (by BEAM_FACTOR) for a 25 m dish, it can be used for a 20 m dish by specifying here 20./25. (or 0.8)
Prompt: Clear reference coordinates (Yes/No)? (may vary per application)
Expected input: Yes/No: 1 value
If you answer YES to this prompt, the reference coordinates of the model will be reset. Otherwise, only the number of components will be set to zero.
Prompt: Area l,m, dl,dm (arcsec) (may vary per application)
Expected input: Real: 1 to 4 values
Specify the area in which all sources should be deleted:
l,m area centre (0,0 = map centre)
dl,dm area size
Prompt: Lower flux limit (may vary per application)
Expected input: Real: 1 value
Source whose absolute flux is below the value specified here will be deleted from the model list.
Prompt: Source attribute to edit| (may vary per application)
Expected input: Character *24: 1 value
Specify the source attribute that you want to edit:
Source coordinates:
L, M coordinates relative to reference (arcsec)
Properties of the source:
I ampitude
SI spectral index
RM intrinsic rotation measure
Q, U, V Stokes parameters in %
LA, SA, PA long axis short axis, position angle of elliptic-Gaussian
extended-source model
Administrative attributes in the model list:
ID identification
BITS bits mask (if source is extended, has polarisation)
TYP source type (0 is the standard)
CCBM clean component (1) and beam-corrected (8)
TP2 reserved
Prompt: New value (may vary per application)
Expected input: Real: 1 value
Specify the value to set in specified edit field.
Prompt: Coincidence radii dl,dm (arcsec) (may vary per application)
Expected input: Real: 1 to 2 values
Point sources that are within (dl,dm) arcsec of each other are combined. The suggested default values are approximately half the synthesised beam radius in l and m directions.
Prompt: specify model disposition and format in the order shown,|- (may vary per application)
Expected input: Character *24: 1 to 5 values
NOTE:
The defaults proposed have been chosen to minimise the time needed for
the lengthy (re)calculations of model visibilities. The price you pay for this
is a near-doubling of the size of the sectors in your .SCN file in which you
store a model. Your priorities may be different, but before choosing
non-default options make sure you understand the consequences.
In principle, the model list now in memory will be used to calculate
the model sources' visibilities in your observation(s).
To avoid this lengthy calculation where possible, the program will try
to use model visibilities stored earlier in the .SCN file. To this end, it will
read the model list from the .SCN file and combine it with the list in core,
then (re)calculate the visibilities only for those components that are not
represented correctly in the .SCN file. Having done that, the program may or
may not save the combined model and its visibilities back into the .SCN file.
You must select ONE of the following options for the combination and
subsequent storage:
MERGE Merge the model in the .SCN file with the one in core discarding
duplicates, i.e. components with identical position, extent and
flux; store the combined model in the .SCN file.
This option is suitable in the most common situations, viz.:
- the list in core is an extension containing the list in the
.SCN file as a subset; or
- the list in core is an incremental update, i.e. a list of
aditional components.
INCREMENT As MERGE, but retain the resultant model IN CORE ONLY without
changing the .SCN file
NEW Overwrite the model in the SCN file with the model in core.
TEMPORARY Use the model in core, ignoring the one in the SCN file.
ADD As MERGE, but without discarding any components, i.e. fluxes
of coincident sources are added.
This option will produce the same effect as MERGE in the case
that the list in core is an incremental update. Its use is
recommended for special applications only.
Separately from the above, you may define which effects must be
accounted for in the visibility calculations. The four items below must be
specified in the order shown. You may select the default by skipping the item,
typing only the delimiter comma; for example ',,\BEAM' will select the
defaults for the first four items.
BAND/NOBAND To correct or not correct the radial extent of your model
components for the smearing due to your finite observing
bandwidth
TIME/NOTIME To correct or not correct the tangential extent of your model
model components for the smearing due to the finite
integration time of your observation
INPOL/NOINPOL To correct or not correct the polarisation components
Q,U,V of your model for the effect of position-dependent
primary-beam polarisation.
(NOTE: The iNPOL option is currently disabled.)
BEAM/NOBEAM To correct or not correct your model fluxes for the
position-dependent gain of the primary beam.
NOTE that specifying options different from those used earlier in calculating the model visibilities that are noe now in the .SCN file will result in a partial or complete recalculation of the visibilities.
Prompt: Model-handling action (may vary per application)
Expected input: Character *24: 1 value
Specify what you want to do with the model list in core:
Consolidating/rearranging the list:
MERGE Combine (point-) sources at the same position.
Must have the same spectral index and rotation measure.
Stokes Q,U,V are properly taken into account.
CLEAN components are NOT combined with non-CLEAN comp.
Extended sources are ignored.
RMERGE As MERGE, but within specified radius (which may be 0).
The (l,m) position of the strongest source is taken.
CLEAN components are combined if at the same position.
SORT Sort source list in decreasing amplitude. (This will be done
automatically when you write the list back to a .MDL file.)
FSORT Sort on a specified field in source list (for subsequent
display)
Modifying sources in the list:
CALIB Calibrate the source list to a new amplitude and/or position
EDIT Edit source list (an amplitude of zero will delete the source)
FEDIT Edit a field in a range of sources
FLUX_KNOWN Toggle the 'unknown-flux' bit. When this bit is off, NCALIB
will by default refrain from attempting a Selfcan gain
solution.
Deleting sources in the list:
DEL Delete sources
DNCLOW Delete non-clean sources with low amplitudes
DCLOW Delete clean components with low amplitudes
DAREA Delete sources in specified area
Miscellaneous:
SHOW Show the list. (You will be prompted for details)
QUIT Quit model-handling.
Prompt: Model-list action| (may vary per application)
Expected input: Character *24: 1 value
Specify the action to be taken on the internal model list:
Transfers between the internal list and an external file:
READ Read the components from a .MDL file on disk into the
program's model list. The default filename is the name of
the calibrator belonging to the most recently read sector,
derived from the fieldname and the frequency. .MDL files are
first searched for in the current directory or the directory
defined by parameter DATAB. If this fails, the file is looked
for in the directory defined by parameter MODELB and finally by
that defined by the Unix environment variable MODELB.
NOTE that reading is INCREMENTAL, so if you read the same
.MDL file twice, you will get every component doubled...
WRITE Write the program's model list to a .MDL file.
INTERN This does not affect the list, but selects
the model stored in the scan-file(s). Selecting INTERN is
equivalent to setting DE_APPLY=MODEL.
You may use this internal model in combination with
components in the program's model list.
Modification and display of the internal list:
CLEAR Empty the program's model list and optionally its reference
coordinates.
ADD Manual input of sources to add the list
MODIFY Enter a submenu with options to modify the model list:
- by deleting sources from the list;
- by editing entries manually;
- by sorting (for subsequent display) the list: you will be
prompted for a definition of the sort order;
- by calibrating.
SHOW Show the program's model list, you will be prompted for details.
QUIT Exit from model-handling.
Prompt: Model listing mode (may vary per application)
Expected input: Character *24: 1 value
Specify what type of listing you want, and where it should be shown:
LIST Show the program's model list in the log file. SHOW Idem, but both on the terminal and in the log file.
RLIST Show the program's model list in RA/DEC coordinates in the log file. RSHOW Idem, but both on the terminal and in the log file.
TOTAL Show the statistics of the program's model list.
QUIT Back to MODEL_OPTION.
Prompt: File with source names (may vary per application)
Expected input: Character *80: 1 value
Specify the full name of the input disk-file. The file should contain lines with Ra, Dec and Name, separated by white space. Comments may be added starting with an exclamation mark. A NULL answer (two double quotes) will ignore the name-list: no file will be opened.
Prompt: Reference coordinates l,m|- (may vary per application)
Expected input: Real: 1 to 2 values
Specify the reference coordinates for the distance sort that you selected.
Prompt: Sort criterion (may vary per application)
Expected input: Character *24: 1 value
Specify sourfce attribute on which to sort:
Source coordinates:
L, M l or m, arbitrary order for the other
LM, ML l and then m, or m and then l
DIST distance to a specified reference point
Properties of the source:
I ampitude
SI spectral index
POL polarised intensity
RM intrinsic rotation measure
Q, U, V Stokes parameters in %
LA, SA, PA long axis short axis, position angle of elliptic-Gaussian
extended-source model
Administrative attributes in the model list:
ID identification
BITS bits mask (if source is extended, has polarisation)
TYP source type (0 is the standard)
CCBM clean component (1) and beam-corrected (8)
TP2 reserved
Expected input: Character *24: 1 value
Specify the polarity of the sort
Prompt: I,l,m,id,Q,U,V,lax,sax,pa,si,rm,rs (may vary per application)
Expected input: Real: 1 to 13 values
Specify the source parameters in order shown.
I intensity (W.U.) l, m coordinates w.r.t. reference (arcsec) id identification number (see below) Q Stokes Q relative to I (% U Stokes U relative to I (% V Stokes V relative to I (% lax long-axis full halfwidth (arcsec, =0 for a point source) sax short-axis full halfwidth (arcsec, =0 for a point source) pa position angle of long axis (degrees, North through East) si spectral index rm intrinsic rotation measure ( rad/m**2 at 1 Ghz) rs reserved
You may omit values that you want to leave alone, but not the commas that delimit them. Trailing values and commas may be omitted.
Example:
,,3 will set m to 3 and leave all other parameters unchanged.
The identification number is of the form
<sequence number>-<mask byte>
Prompt: Amlitude ratio Anew/Aold, | shift dl,dm (arcsec) (may vary per application)
Expected input: Real: 1 to 3 values
Specify the calibration parameters in te order shown: An/Ao new/old amplitude dl new-old l in arcsec dm new-old m in arcsec
Prompt: Source number list (may vary per application)
Expected input: Integer: 1 to 128 values
Specify a list of individual source numbers to be acted upon. If you want to spaecfy a range, reply '*' here and wait for the next prompt
Prompt: Source number (may vary per application)
Expected input: Integer: 1 value
Specify the number of the source to be acted upon.
Prompt: Source number range (may vary per application)
Expected input: Integer: 1 to 2 values
Specify the first and last source number to process. * indicates 'all'. If you want all sources from some number <N> upward, reply
'<N>-<some very large number>'.
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