Configuration Parameters

A number of reduction parameters can be changed using entries in the configuration file.

If you installed the pipeline with pip, the configuration file will not be easy to find, since it will be stored with installed pip packages. If you need to modify the configuration, we advise that you download a copy of the config file, saving it to some easy to remember location, and using the -c option to point to that file.

If you installed the package via git, the master copy of the configuration file is in the installation directory, in kcwidrp/config/kcwi.cfg. This file can be modified in place or copied in another directory (the -c option of the main reduction script is used to specify the configuration file).

The configuration file contains a number of parameters connected to the structure of the files and to the specifications of the instrument, e.g. the number of continuum bars. There is usually no reason to modify these parameters, and they are not described here.

The remaining parameters are used to control the processing algorithms and are described here.

Processing parameters

bias_min_nframes = 7
flat_min_nframes = 6
dome_min_nframes = 3
twiflat_min_nframes = 1
dark_min_nframes = 3
arc_min_nframes = 1        # = 3 for [RED]
contbars_min_nframes = 1   # = 3 for [RED]
minoscanpix = 75           # = 20 for [RED]
oscanbuf = 20              # = 5 for [RED]

These parameters control the minimum number of bias, internal/dome/twilight flats and darks that the DRP expects before producing a master calibration. The arcs and contbars minimum numbers are different for the Blue and Red channels as described above. The values shown here are synchronized with the calibration scripts that we use in the afternoon.

The overscan parameters are based on the configuration of the Blue and Red detectors and we do not recommend altering these parameters.

skipscat = False        # Skip subtracting scattered light?
skipsky = False         # Skip sky subtraction?

These control scattered light subtraction and sky subtraction. Setting either of these to True will skip the subtraction for all subsequent runs of the pipeline. Skipping sky subtraction globally can also be invoked by using -k on the command line.

plot_pause = 1         # Pause time for each plot in seconds
saveintims = False     # Save intermediate images during basic reduction
verbose = 1            # Verbosity of output

These control various aspects of how the DRP runs: how long to pause at each plot if not in interactive mode (see plot_level below), whether to save intermediate images for diagnosis, and the verbosity level of text output.

TAPERFRAC = 0.2        # Adjusts edge taper for Atlas cross-correlation
TUKEYALPHA = 0.2       # Tukey alpha value for cross-correlating bars
FRACMAX = 0.5          # How much of line peak to use for fitting
MIDFRAC = -1.0         # Middle fraction or -1 to use default calculation
ATOFF = 0              # Atlas offset or 0 to use default calculation
LINELIST = ""          # Optional line list to use instead of generated
LINETHRESH = 100.      # Line threshhold for fitting

These adjust the way in which arc line fitting is performed. In most cases, you will not have to adjust these. For the Red channel, we use these values:

TUKEYALPHA = 0.7
FRACMAX = 0.25
LINETHRESH = 10.

See the [RED] section to make changes for Red channel data.

default_arc_lamp = 'ThAr'

KCWI has two calibration lamps, Thorium/Argon (ThAr) and Iron/Argon (FeAr). This parameter specifies which of the two lamps should be used by the DRP. The default is to use the ThAr lamp.

Wavelength correction parameters:

radial_velocity_correction = "heliocentric"
air_to_vacuum = True   # Defaults to vacuum wavelengths

These control the refinement of the wavelength solution. You can specify if you want air wavelengths by setting air_to_vacuum to False. You can specify the type of radial velocity correct as one of:

• heliocentric
• barycentric
• none

Plotting parameters

# BOKEH SERVER
enable_bokeh = False
plot_level = 1

These parameters control the plotting features of the DRP. Plotting is performed using a combination of a Bokeh server running in the background and a browser front end.

To activate the plotting features, set enable_bokeh = True. When the DRP starts, it will check if there is an instance of the Bokeh server running or start one. A browser window will be opened automatically when needed.

The plot_level parameter controls the level of interactivity. Setting it 0 will disable plotting. Setting it to 1 will enable plotting, but the DRP will not interact with the user. A higher level will increase both the verbosity and the interactivity of the plots. The highest level is 3. At this level, the user will be provided with a plot of every arc line, for example, with a graphic representation of the fitting used to determine the central position.

For general use, it is advisable to leave the plot level to 1.

The size of the plotting window can be specified using plot_width and plot_height.

Cosmic rays rejection parameters

CRR_MINEXPTIME = 60.0
CRR_PSSL = 0.0
CRR_GAIN = 1.0
CRR_READNOISE = 3.2
CRR_SIGCLIP = 4.5
CRR_SIGFRAC = 0.3
CRR_OBJLIM = 4.0
CRR_PSFFWHM = 2.5
CRR_FSMODE = "median"
CRR_PSFMODEL = "gauss"
CRR_SATLEVEL = 60000.0
CRR_VERBOSE = False
CRR_SEPMED = False
CRR_CLEANTYPE = "meanmask"
CRR_NITER = 4

These parameters are used to control the CRR algorithms. See the documentation in astroscrappy for details (PROVIDE LINK)