STScI Logo

pltrans stsdas.hst_calib.synphot


NAME · USAGE · DESCRIPTION_ · PARAMETERS · EXAMPLES · REFERENCES
SEE_ALSO

NAME

pltrans -- Create photometric transformation plots

USAGE

pltrans spectrum xmode ymode xform yform

DESCRIPTION

This task plots general photometric transformation diagrams, such as Color-Color and Color-Magnitude diagrams. The user specifies a set of spectra and a mode and a form for each axis. Most usually the spectrum parameter is a filename preceded by a "@" character. The file contains one filename or synphot spectral expression per line. The parameter vzero can also be used to generate a set of spectra. Precalculated photometric data for plotting can be read in from the file specified by the input parameter and results can be saved in table specified by the'output' parameter.

PARAMETERS

spectrum [string]
This is a sequence of commands that create the synthetic spectrum. The commands can be placed in a file, whose name is passed to this parameter, preceded by a "@" character, e.g., @filename. Each line in this command file is treated as a separate set of commands. If this parameter is left blank or set to none, the only points plotted will be those read from the table specified in parameter input

The commands that can be passed to this parameter are described in detail in the help file for the calcspec task.

xmode [string]
Mode for the X-axis of the plot. This can be either a single mode or a color difference. Single modes are specified using the syntax "band(mode)", or simply "mode". Color differences are specified using the syntax "band(mode1) - band(mode2)". "Mode", "mode1", and "mode2" are comma separated lists of observation mode keywords. These keywords are described in the obsmode task. If this parameter is left blank or set to "none", a default observation mode that is everywhere one will be used.
ymode [string]
Mode for the Y-axis. This can also be either a single mode or a color difference. The syntax is the same as used by xmode.
xform [string]
Form of the X data. The following forms are recognized:


	FNU		erg / s / cm^2 / Hz
	FLAM		erg / s / cm^2 / A
	PHOTNU		photons / s / cm^2 / Hz
	PHOTLAM		photons / s / cm^2 / A
	COUNTS		photons / s 
	ABMAG		-2.5 log_10 (FNU)  - 48.60
	STMAG		-2.5 log_10 (FLAM) - 21.10
	VEGAMAG		-2.5 log_10 (F/F_vega)
	OBMAG		-2.5 log_10 (COUNTS)
	JY		10^-23 erg / s / cm^2 / Hz
 	MJY		10^-26 erg / s / cm^2 / Hz

A standard magnitude system is VEGAMAG, for which Vega by definition has magnitude 0 at all wavelengths. The AB and ST magnitude systems are based on constant flux per unit frequency and per unit wavelength, respectively. The zero points for these two systems are set for convenience so that Vega has magnitude 0 in both systems for the Johnson V passband.
yform [string]
Form of the Y data. The same forms recognized for xform are also recognized for yform.
(vzero = " ") [string]
A list of values to substitute for variable zero. Each value in the list is substituted in turn for the string $0 wherever it occurs in the input spectrum. The values must be real numbers. Using vzero is the equivalent of placing the input spectrum several times in a file, with each spectrum containing one of the values in the list. The list may contain single values or ranges. The endpoints of the ranges are separated by a dash. An optional step size follows the range, preceded by the letter x. If the step size is not present, the step size defaults to 1 or -1, depending on the order of the endpoints. The following table gives several examples of valid lists

	.1,.2,.3,.4	A list of single values
	.1-.4x.1	The same list expressed as a range
	-1 - -4 	A range with an implicit step size of -1
	1-9,10-20x2	A list of more than one range
(input = "none") [file name]
Name of a file containing calculated X-Y pairs of points for plotting. The x and y coordinates of the points are read frum columns "FLUX1" and "FLUX2", if the file is an SDAS table and the first and second columns if the file is an ascii file. If the file is an SDAS table, the values of xmode, ymode, xform, and yform will be read from table header parameters of the same name and these values will supersede the values in the parameter file. If the value of this parameter is "none" or blank, no file will be read.
(output = "none") [file name]
Name of the SDAS table used for output. The table has two columns, "FLUX1" and "FLUX2", containing the x and y coordinates of the data points. It has four header parameters, "XFORM", "YFORM", "XMODE", and "YMODE", containing the values of the respective task parameters. If the value of append is set to yes and a table of the same name already exists, the data will be appended to the existing table. Otherwise it will overwrite it. This table has the same format as the table read input, so output generated from this task can be replotted later without recalculating it. If the value of this parameter is "none" or blank, no file will be written.
(left = INDEF) [real]
Minimum x value to plot. If set to INDEF, the task will set it to the minimum x value.
(right = INDEF) [real]
Maximum x value to plot. If set to INDEF, the task will set it to the maximum x value.
(bottom = INDEF) [real]
Minimum y value to plot. If set to INDEF, the task will set it to the minimum y value.
(top = INDEF) [real]
Maximum y value to plot. If set to INDEF, the task will set it to the maximum y value.
(append = no) [boolean]
Append results to an existing plot?
(mktype = "plus") [string]
The marker type to be used for plotting the results. The value of this parameter is either a text string preceded by an exclamation point, in which case the text minus the exclamation point will be plotted at each data point; a line symbol (clear, solid, dashed, dotted, or dotdash), in which case a line will be plotted through the data points, or a point symbol (point, fill, box, plus, cross, diamond, hline, vline, hebar, vebar, or circle), in which case the indicated symbol will be plotted at the data point.
(device = "stdgraph") [string]
Send output to the designated device.
(wavetab = "") [file name]
Name of an optional wavelength table or file. An appropriate table can be generated by using the genwave task. If a table is used, the wavelength column name must be "WAVELENGTH". If an ASCII file is used the first column is taken to be the wavelength column. The subdirectory 'synphot$data has ASCII wavelength tables useful for specific HST passbands.

If no wavelength table is specified, the task generates a wavelength set which covers the range between the left and right plot limits. If there is no wavelength table, and plot limits are not specified, a default wavelength set is used. The default wavelength set covers the wavelength range where the spectrum is non-zero. Wavelengths are spaced logarithmically over this range. If more than one spectrum is plotted, the range is computed based on the first spectrum. If the wavelength range of the spectra differ significantly, a wavelength table should be specified explicitly or plot limits should be set.

(refdata = " ") [pset name]
Parameter set for reference data used in calculations. The following parameters are stored in this set.

     area = 45238.93416:  HST telescope area in cm**2.

     grtbl = "mtab$*.tmg":  HST graph table.  Uses the
	       most recent version by default.

     cmptbl = "mtab$*.tmc":  Instrument component table.  
                The most recent version is used by default.

EXAMPLES

1. Produce a color magnitude diagram of a list of stars:

sy> pltrans @bpgs.lis "band(v)" "band(b)-band(v)" stmag stmag

2. Show how the counts through the wfpc f555w filter vary with the color of the star:

sy> pltrans "rn(bb($0),band(v),10,stmag)" "band(b)-band(v)" \ >>> "band(wfpc,f555w)" stmag counts vzero="3e3-2e4x1e3"

REFERENCES

Written by B.Simon based on XCAL code written by Keith Horne

SEE ALSO

plspec


Source Code · Package Help · Search Form · STSDAS