mk1dspec input
input
Spectra to create or modify.
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.
ap = 1
Image line to be created or modified in images of dimension greater than 1.
rv = 0.
Radial velocity (km/s) or redshift, as selected by the parameter z,
applied to line positions and continuum. Velocities are converted to
redshift using the relativistic relation 1+z = sqrt ((1+rv/c)/(1-rv/c)).
Note the shift is not a shift in the dispersion parameters but in the
underlying artificial spectrum.
z = no
Is the velocity parameter a radial velocity or a redshift?
WHEN CREATING NEW SPECTRA
title =
Image title to be given to the spectra. Maximum of 79 characters.
ncols = 512
Number of columns.
naps = 1
Number of lines or apertures.
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 imheader is an acceptible data file. See mkheader
for further information.
wstart = 4000., wend = 8000.
Starting and ending wavelengths in Angstroms. The dispersion is
determined by these values and the number of columns.
CONTINUUM PARAMETERS
continuum = 1000., slope = 0.
Continuum of the starting wavelength at rest and the slope of the continuum.
temperature = 5700.
Blackbody continuum temperture in Kelvin. A value of 0 is used if
no blackbody continuum is desired. The intensity level is set by
scaling to the continuum level of the starting wavelength at rest.
fnu = no
Compute the continuum as flux per unit frequency (F-nu) if yes or flux per
unit wavelength (F-lambda) if no.
LINE PARAMETERS
lines =
List of spectral line files. Spectral line files contain lines of rest
wavelength, peak, and widths (see the the DESCRIPTION section).
The latter two parameters may be missing in which case they default to
the task peak and sigma parameters. If no file or a new
(nonexistent) file is specified then a number of random lines given by the
parameter nlines is generated. If a new file name is specified then
the lines generated are recorded in the file. If the list of spectral
line files is shorter than the list of input spectra, the last
spectral line list file is reused.
nlines = 0
If no spectral line file or a new file is specified then the task will
generate this number of random spectral lines. The rest wavelengths are
uniformly random within the limits of the spectrum, the peaks are
uniformly random between zero and the value of the peak parameter
and the width is fixed at the value of the sigma parameter.
If a redshift is applied the rest wavelengths are shifted and repeated
periodically.
peak = -0.5
The maximum spectral line peak value when generating random lines or
when the peak is missing fromthe spectral line file.
This value is relative to the continuum unless the continuum is zero.
Negative values are absorption lines and positive values are emission lines.
sigma = 10.
The default line width as a gaussian sigma in Angstroms when generating
random lines or when the width is missing from the spectral line file.
seed = 1
Random number seed.
comments = yes
Include comments recording task parameters in the image header?
PACKAGE PARAMETERS
nxsub = 10
Number of pixel subsamples used in computing the gaussian spectral line
profiles.
dynrange = 100000.
The gaussian line profiles extend to infinity so a dynamic range, the ratio
of the peak intensity to the cutoff intensity, is imposed to cutoff
the profiles.
This task creates or modifies one dimensional spectra. with a combination of blackbody and linear sloped continuum and emission and absorption gaussian profile spectral lines. A velocity shift may be applied to the underlying artificial spectrum which is shifted into the specified observed wavelength region. No noise is included but may be added with the task mknoise. New spectra are created with the specified number of pixels, wavelength range, and real datatype. When nlines is greater than 1 then an image with the specified number of lines is created though only the line given by the ap is will have a spectrum. Existing spectra may be modified in place or new spectra output. Spectra are modified by adding the continuum and lines defined by the parameters.
For new images a set of header keywords may be added by specifying an image or data file with the header parameter (see also mkheader). 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 to this optional header, parameters for the wavelength coordinates are defined. Finally, comments may be added to the image header recording the task parameters and any information from the line file which are not line definitions.
Initially all spectra are created without a dispersion function; i.e. pixel coordinates. For multiple spectra in an image this task must be executed for each image line to set the dispersion function and add data. When an image line is selected if it has a defined dispersion function that is used otherwise the task wavelength parameters are used.
A continuum is defined by the value at the starting wavelength at rest, a slope, and a blackbody function of a given temperture. The blackbody function is scaled to have the specified continuum value at the starting wavelength at rest. The blackbody flux units are per unit wavelength (F-lambda). A zero continuum value or a zero temperture will not produce a blackbody continuum.
Spectral lines are modeled by gaussian profiles of specified wavelength, peak, and sigma. The lines are defined in a spectral line file or generated randomly. A spectral line file consists of text lines giving rest wavelength, peak, and sigma. The sigma or the sigma and peak may be absent in which case the parameters sigma and peak will be used. If peak values are missing random values between zero and the peak value are generated. Thus, a simple list of wavelengths or a list of wavelengths and peaks may be used.
If no spectral line file is specified or a new (nonexistent) file is named then the number of random lines given by the parameter nlines is generated. The rest wavelengths are uniformly random within the wavelength range of the spectrum and extend periodically outside this range in the case of an applied velocity shift, the peaks are uniformly random between zero and the peak parameter, and the widths are given by the sigma parameter. If a new file is named then the parameters of the generated lines will be output.
The peak values are taken relative to a positive continuum. In other words the generated line profile is multiplied by the continuum (with a minimum of zero for fully saturated absorption lines). If the continuum is less than or equal to zero, as in the case of an artificial arc spectrum or pure emission line spectrum, then the peak values are absolute intensities. Positive peak values produce emission lines and negative values produce absorption lines. Odd results will occur if the continuum has both positive and zero or negative values.
The width values are gaussian sigmas given in Angstroms.
The underlying rest spectrum may be shifted. This is used primarily for testing radial velocity measuring algorithms and is not intended as a complete model of redshift effects. The starting and ending wavelengths are not changed by redshifting; these are the instrumental observed wavelengths. Input line wavelengths are specified at rest and then shifted into or out of the final spectrum. To be realistic the line list should include wavelengths over a great enough range to cover all desired redshifts. The peaks and sigma are also appropriately modified by a redshift. As an example, if the redshift is 1 the lines will appear broader by a factor of 2 and the peaks will be down by a factor of 2 in order to maintain the same flux.
The random line generation is difficult in that one wants to have the
same set of lines (for a given seed) observed at different redshifts.
What is done is that the specified number of random lines is generated
within the observed wavelength interval taken at rest. This set is
then repeated periodical over all wavelengths. A redshift will then
shift these rest lines in to or out of the observed spectrum. If the
lines are output, they are given at rest. Note that this
periodicity may be important in interpreting cross correlation redshift
tests for large shifts between template and object spectra.
The definitions of the continuum are also affected by a redshift.
The reference point for the continuum level, slope, and blackbody
continuum is the starting wavelength taken at rest. Shifts will then
modify the continuum level at the first pixel appropriately. In
particular a large redshift will shift the blackbody in such a way that
the flux is still given by the continuum parameter at the starting
wavelength at rest.
The wavelengh parameters are written to the parameters W0, WPC, CRPIX1,
CRVAL1, and CDELT1. Note that the keyword DC-FLAG is not created
so some tasks may consider the spectra to not be dispersion corrected.
1. Create a simple blackbody continuum between the default wavelengths.
2. Create a random absorption spectrum on a blackbody continuum without
saving the line list.
3. Create a random absorption spectrum with noise and cosmic rays.
4. Create a random emission spectrum on a blackbody continuum and save
the line list.
5. Create an artificial random arc line spectrum.
6. Create a test spectrum with a line list.
7. Add absorption lines to a spectrum.
Normally the input spectrum would be a real spectrum.
8. Make two spectra taken from the same set of random lines but differing
in redshift.
9. Make a multispec image with 5 apertures and a range of redshifts.
REVISIONS
mknoise,
mk2dspec,
mkheader,
onedspec.sinterp,
KEYWORDS
EXAMPLES
cl> mk1dspec bb title=Blackbody
cl> mk1dspec bbab title=Absorption nlines=100
cl> mk1dspec bbab title=Absorption nlines=100
cl> mknoise bbab rdnoise=10 poisson+ ncos=5 energy=1000
cl> mk1dspec bbem title=Emission nl=30 peak=0.6 lines=bbem.dat
cl> mk1dspec arc title="Arc lines" cont=0 peak=500 nl=30
cl> type linelist
4100 -.1 10
4200 -.2 10
4300 -.3 10
5100 -.9 1
5200 -.9 2
5300 -.9 4
6700 .9 4
6800 .9 2
6900 .9 1
7700 .3 10
7800 .2 10
7900 .1 10
cl> mk1dspec testspec title=Test cont=500 temp=0 lines=linelist
cl> mk1dspec bb out=artspec cont=0 lines=STDIN
4300 -60 3.2
5000 -200 3.2
[EOF]
cl> mk1dspec restspec nl=30
cl> mk1dspec redspec rv=3000 nl=30
cl> mk1dspec bluespec rv=-.01 z+ nl=30
cl> mk1dspec spec.ms ap=1 nl=30 rv=0 naps=5
cl> mk1dspec spec.ms ap=2 nl=30 rv=1000
cl> mk1dspec spec.ms ap=3 nl=30 rv=2000
cl> mk1dspec spec.ms ap=4 nl=30 rv=3000
cl> mk1dspec spec.ms ap=5 nl=30 rv=4000
REVISIONS
MK1DSPEC V2.10.3
The format parameter was eliminated and the task updated to produce the
current coordinate system format.
SEE ALSO
This page automatically generated from the iraf .hlp file. If you
would like your local iraf package .hlp files converted into HTML
please contact Dave Mills at NOAO.dmills@noao.edu