The fors_wave_calib recipe

fors_wave_calib

Synopsis

Derive dispersion relation from rectified arc lamp frame

Description

This recipe is used to wavelength calibrate MOS/MXU slit spectra contained in the rectified arc lamp exposure produced with recipe fors_extract_slits.

A pattern-matching algorithm is applied as in recipe fors_detect_spectra.

The input spatial map is used in the production of the wavelength map.

Use recipe fors_wave_calib_lss for LSS data, or for MOS/MXU data where all slits have the same offset. For more details on this data reduction strategy please refer to the FORS Pipeline User’s Manual.

Note that specifying an input GRISM_TABLE will set some of the recipe configuration parameters to default values valid for a particular grism.

In the table below the MXU acronym can be alternatively read as MOS.

Input files

DO category:               Type:       Explanation:         Required:
SPATIAL_MAP_MXU            Calib       Spatial map             Y
RECTIFIED_LAMP_MXU         Calib       Rectified arc exposure  Y
SLIT_LOCATION_MXU          Calib       Slit location table     Y
CURV_COEFF_MXU             Calib       Spectral curvature      Y
MASTER_LINECAT             Calib       Line catalog            Y
GRISM_TABLE                Calib       Grism table             .

Output files

DO category:               Data type:  Explanation:
REDUCED_LAMP_MXU           FITS image  Calibrated arc lamp exposure
DISP_COEFF_MXU             FITS table  Inverse dispersion coefficients
DISP_RESIDUALS_MXU         FITS image  Image of modeling residuals
WAVELENGTH_MAP_MXU         FITS image  Wavelengths mapped on CCD
SPECTRAL_RESOLUTION_MXU    FITS table  Spectral resolution table

Constructor

cpl.Recipe("fors_wave_calib")

Create an object for the recipe fors_wave_calib.

import cpl
fors_wave_calib = cpl.Recipe("fors_wave_calib")

Parameters

fors_wave_calib.param.dispersion

Expected spectral dispersion (Angstrom/pixel) (float; default: 0.0) [default=0.0].

fors_wave_calib.param.peakdetection

Initial peak detection threshold (ADU) (float; default: 0.0) [default=0.0].

fors_wave_calib.param.wdegree

Degree of wavelength calibration polynomial (int; default: 0) [default=0].

fors_wave_calib.param.wradius

Search radius if iterating pattern-matching with first-guess method (int; default: 4) [default=4].

fors_wave_calib.param.wreject

Rejection threshold in dispersion relation fit (pixel) (float; default: 0.7) [default=0.7].

fors_wave_calib.param.wcolumn

Name of line catalog table column with wavelengths (str; default: ‘WLEN’) [default=”WLEN”].

fors_wave_calib.param.startwavelength

Start wavelength in spectral extraction (float; default: 0.0) [default=0.0].

fors_wave_calib.param.endwavelength

End wavelength in spectral extraction (float; default: 0.0) [default=0.0].

The following code snippet shows the default settings for the available parameters.

import cpl
fors_wave_calib = cpl.Recipe("fors_wave_calib")

fors_wave_calib.param.dispersion = 0.0
fors_wave_calib.param.peakdetection = 0.0
fors_wave_calib.param.wdegree = 0
fors_wave_calib.param.wradius = 4
fors_wave_calib.param.wreject = 0.7
fors_wave_calib.param.wcolumn = "WLEN"
fors_wave_calib.param.startwavelength = 0.0
fors_wave_calib.param.endwavelength = 0.0

You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:

import cpl
fors_wave_calib = cpl.Recipe("fors_wave_calib")
[...]
res = fors_wave_calib( ..., param = {"dispersion":0.0, "peakdetection":0.0})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to Carlo Izzo. Alternatively, you may send a report to the ESO User Support Department.