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.help mk2dspec Aug90 noao.artdata
.ih
NAME
mk2dspec -- Make/add 2D spectra using 1D spectra templates
.ih
USAGE
mk2dspec input
.ih
PARAMETERS
.ls input
Spectra to create or modify.
.le
.ls output = ""
Output spectra when modifying input spectra. If no output spectra are
given then existing spectra in the input list are modified directly.
If an output list is given then it must match in number the input list.
.le
.ls models = ""
List of model parameter files. If the list of model files is shorter than the
list of input images then the last model file is reused. The model
parameter files contain lines giving one dimensional spectrum template
name, intensity scale, type of cross dispersion profile, profile
width in the center line, change of width per line, profile position
in the center line, and change of position per line (see the DESCRIPTION
section).
.le
.ls comments = yes
Include comments recording task parameters in the image header?
.le
WHEN CREATING NEW SPECTRA
.ls title = ""
Image title to be given to the spectra. Maximum of 79 characters.
.le
.ls ncols = 100, nlines = 512
Number of columns and lines.
.le
.ls header = "artdata$stdheader.dat"
Image or header keyword data file. If an image is given then the image header
is copied. If a file is given then the FITS format cards are copied.
This only applies to new images. The data file consists of lines
in FITS format with leading whitespace ignored. A FITS card must begin
with an uppercase/numeric keyword. Lines not beginning with a FITS
keyword such as comments or lower case are ignored. The user keyword
output of \fBimheader\fR is an acceptable data file. See \fBmkheader\fR
for further information.
.le
.ih
DESCRIPTION
This task creates or modifies two dimensional spectra by taking one
dimensional spectra, convolving them with a spatial profile across the
dispersion, and adding them into two dimensional images. The one
dimensional spectra may be real data or artificial data created with
the task \fBmk1dspec\fR. No noise is included but may be added with
the task \fBmknoise\fR. The spatial profile is fully subsampled and
may vary in width and position along the dispersion axis. The spatial
axis is along the first dimension and the dispersion is along the
second dimension.
For new images a set of header keywords may be added by specifying an
image or data file with the \fIheader\fR parameter (see also \fBmkheader\fR).
If a data file is specified lines beginning with FITS keywords are
entered in the image header. Leading whitespace is ignored and any
lines beginning with words having lowercase and nonvalid FITS keyword
characters are ignored. In addition, comments may be added to
the image header recording the model file name and the contents of the
model file.
The spatial profile models are specified in one or more model parameter
files. These files contain lines giving a one dimensional spectrum template
name, intensity scale, type of cross dispersion profile, profile
width in the center line, change of width per line, profile position
in the center line, and change of position per line. More specifically:
.ls <template name>
The one dimensional spectrum template is any one dimensional IRAF image.
If the spectrum template length is less than the two dimensional spectrum,
the profile extends only over that number of lines and, if it is longer,
then only the first part of the spectrum is used.
.le
.ls scale
The template spectrum is scaled by this parameter to define the
total flux for the two dimensional profile.
.le
.ls <profile type>
The spatial profiles are identified by two keywords, "gaussian"
or "slit". The profiles are defined by the following formulae,
.nf
gaussian: I(x) = exp (-ln(2) * (2*(x-xc)/fwhm)**2)
slit: I(x) = exp (-ln(2) * (2*(x-xc)/fwhm)**10)
.fi
where x is the column coordinate, xc is the profile center, and
fwhm is the full width at half maximum. The "gaussian" profile
is the usual gaussian specified in terms of a FWHM. The "slit"
profile is one which is relatively flat and then rapidly drops
to zero. The profile is normalized to unit integral so that
the total flux across the profile is given by the scaled
1D spectrum flux.
.le
.ls fwhm, dfwhm
The full width at half maximum and derivative with line number. The fwhm is
defined for the middle of the image. The FWHM as a function
of line, l, is,
fwhm + (l - nlines/2) * dfwhm
.le
.ls center, dcenter
The profile center and derivative with line number. The center is
defined for the middle of the image. The center as a function
of line, l, is,
center + (l - nlines/2) * dcenter
.le
The provision for having the spectra tilted relative to the columns is
useful for understanding undersampling effects. However, note that the
spectral lines are not perpendicular to the dispersion but are always
aligned with the image lines.
.ih
EXAMPLES
1. Create an artificial multifiber spectrum:
.nf
cl> type multifiber.dat
arc 4 gauss 3 0 20 .01
spec1 .5 gauss 3 0 30 .01
spec2 .4 gauss 3 0 40 .01
spec3 .9 gauss 3 0 50 .01
spec4 .2 gauss 3 0 60 .01
spec5 .6 gauss 3 0 70 .01
spec6 1 gauss 3 0 80 .01
spec7 1 gauss 3 0 90 .01
cl> mk1dspec arc cont=0 peak=500 nl=30
cl> mk1dspec spec1 nlines=99 seed=1
cl> mk1dspec spec2 nlines=80 seed=2
cl> mk1dspec spec3 nlines=45 seed=3
cl> mk1dspec spec4 nlines=95 seed=4
cl> mk1dspec spec5 nlines=66 seed=5
cl> mk1dspec spec6 nlines=90 seed=6
cl> mk1dspec spec7 nlines=85 seed=7
cl> mk2dspec multifiber model=multifiber.dat
.fi
In this example artificial one dimensional spectra are generated with
\fBmk1dspec\fR.
2. Create an artificial multislit spectrum:
.nf
cl> type multislit.dat
arc 10 slit 18 0 120 .01
sky 2.5 slit 18 0 140 .01
sky 2.5 slit 18 0 160 .01
sky 2.5 slit 18 0 180 .01
sky 2.5 slit 18 0 200 .01
sky 2.5 slit 18 0 220 .01
spec1 .05 gauss 3 0 140 .01
spec2 .2 gauss 4 0 161 .01
spec3 .1 gauss 3 0 179 .01
spec4 .1 gauss 3 0 200 .01
spec5 .15 gauss 4 0 220 .01
cl> mk1dspec sky peak=1 nl=100
cl> mk2dspec multislit model=multislit.dat nc=400
.fi
Note how two spectra are overlaid to provide a sky spectrum with a
narrower object spectrum.
3. Create an artificial long slit spectrum:
.nf
cl> type longslit.dat
sky 22 slit 160 0 220 .01
spec5 .05 gauss 3 0 140 .01
spec1 .05 gauss 3 0 190 .01
spec4 .5 gauss 3 0 220 .01
spec2 2 gauss 40 0 220 .01
spec5 .1 gauss 3 0 240 .01
spec1 .02 gauss 3 0 290 .01
cl> mk2dspec longslit model=longslit.dat nc=400
.fi
Note how objects are overlaid on a long slit sky spectrum. The width
of the spec2 spectrum is wider simulating a galaxy spectrum.
4. To include noise use the task \fBmknoise\fR:
.nf
cl> mk2dspec longslit model=longslit.dat nc=400
cl> mknoise longslit rdnoise=10 gain=2 poisson+ ncos=100
.fi
5. Use a real long slit spectrum and add an object with an artificial spectrum:
.nf
cl> mk1dspec artspec1d nlines=50
cl> mk2dspec ls005 out=ls005new model=STDIN
artspec1d 1 gauss 5 0 125 0
[EOF]
.fi
.ih
SEE ALSO
mk1dspec, mknoise, mkheader
.endhelp
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