The fors_pmos_calib recipe

fors_pmos_calib

Synopsis

Determination of the extraction mask

Description

This recipe is used to identify reference lines on PMOS arc lamp exposures, and trace the spectral edges on the corresponding flat field exposures. This information is used to determine the spectral extraction mask to be applied in the scientific data reduction, performed with the recipe fors_science.

This recipe accepts both FORS1 and FORS2 frames. The input arc lamps and flat field exposures are assumed to be obtained quasi-simultaneously, so that they would be described by exactly the same instrument distortions.

A line catalog must be specified, containing the wavelengths of the reference arc lamp lines used for the wavelength calibration. A grism table (typically depending on the instrument mode, and in particular on the grism used) may also be specified: this table contains a default recipe parameter setting to control the way spectra are extracted for a specific instrument mode, as it is used for automatic run of the pipeline on Paranal and in Garching. If this table is specified, it will modify the default recipe parameter setting, with the exception of those parameters which have been explicitly modifyed on the command line.

If a grism table is not specified, the input recipe parameters values will always be read from the command line, or from an esorex configuration file if present, or from their generic default values (that are rarely meaningful). Finally a master bias frame must be input to this recipe.

The products SPECTRA_DETECTION_PMOS, SLIT_MAP_PMOS, and DISP_RESIDUALS_PMOS, are just created if the –check parameter is set to true.

The MASTER_DISTORTION_TABLE is marked as required, but it is not so if all slits have different offsets, and in the case of FORS1 observations made with the old TK2048EB4-1 1604 chip read in windowed mode (2048x400)

Input files

DO category:              Type:       Explanation:          Required:
SCREEN_FLAT_PMOS          Raw         Flat field exposures     Y
LAMP_PMOS                 Raw         Arc lamp exposure        Y
MASTER_BIAS or BIAS       Calib       Bias frame               Y
MASTER_LINECAT            Calib       Line catalog             Y
GRISM_TABLE               Calib       Grism table              .

MASTER_DISTORTION_TABLE   Calib       Master distortions table Y

Output files

DO category:              Data type:  Explanation:
MASTER_SCREEN_FLAT_PMOS   FITS image  Combined (sum) flat field
MASTER_NORM_FLAT_PMOS     FITS image  Normalised flat field
MAPPED_SCREEN_FLAT_PMOS   FITS image  Wavelength calibrated flat field
MAPPED_NORM_FLAT_PMOS     FITS image  Wavelength calibrated normalised flat
REDUCED_LAMP_PMOS         FITS image  Wavelength calibrated arc spectrum
DISP_COEFF_PMOS           FITS table  Inverse dispersion coefficients
DISP_RESIDUALS_PMOS       FITS image  Residuals in wavelength calibration
DISP_RESIDUALS_TABLE_PMOS FITS table  Residuals in wavelength calibration
DELTA_IMAGE_PMOS          FITS image  Offset vs linear wavelength calib
WAVELENGTH_MAP_PMOS       FITS image  Wavelength for each pixel on CCD
SPECTRA_DETECTION_PMOS    FITS image  Check for preliminary detection
SLIT_MAP_PMOS             FITS image  Map of central wavelength on CCD
CURV_TRACES_PMOS          FITS table  Spectral curvature traces
CURV_COEFF_PMOS           FITS table  Spectral curvature coefficients
SPATIAL_MAP_PMOS          FITS image  Spatial position along slit on CCD
SPECTRAL_RESOLUTION_PMOS  FITS table  Resolution at reference arc lines
SLIT_LOCATION_PMOS        FITS table  Slits on product frames and CCD

Constructor

cpl.Recipe("fors_pmos_calib")

Create an object for the recipe fors_pmos_calib.

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

Parameters

fors_pmos_calib.param.dispersion

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

fors_pmos_calib.param.peakdetection

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

fors_pmos_calib.param.wdegree

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

fors_pmos_calib.param.wradius

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

fors_pmos_calib.param.wreject

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

fors_pmos_calib.param.wcolumn

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

fors_pmos_calib.param.cdegree

Degree of spectral curvature polynomial (long; default: 0) [default=0].

fors_pmos_calib.param.cmode

Interpolation mode of curvature solution (0 = no interpolation, 1 = fill gaps, 2 = global model) (long; default: 1) [default=1].

fors_pmos_calib.param.startwavelength

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

fors_pmos_calib.param.endwavelength

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

fors_pmos_calib.param.stack_method

Frames combination method (str; default: ‘average’) [default=”average”].

fors_pmos_calib.param.minrejection

Number of lowest values to be rejected (long; default: 1) [default=1].

fors_pmos_calib.param.maxrejection

Number of highest values to be rejected (long; default: 1) [default=1].

fors_pmos_calib.param.klow

Low threshold in ksigma method (float; default: 3.0) [default=3.0].

fors_pmos_calib.param.khigh

High threshold in ksigma method (float; default: 3.0) [default=3.0].

fors_pmos_calib.param.kiter

Max number of iterations in ksigma method (long; default: 999) [default=999].

fors_pmos_calib.param.ddegree

Degree of flat field fitting polynomial along dispersion direction (long; default: -1) [default=-1].

fors_pmos_calib.param.dradius

Smooth box radius for flat field along dispersion direction (long; default: 10) [default=10].

fors_pmos_calib.param.qc

Compute QC1 parameters (bool; default: True) [default=True].

fors_pmos_calib.param.check

Create intermediate products (bool; default: False) [default=False].

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

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

fors_pmos_calib.param.dispersion = 0.0
fors_pmos_calib.param.peakdetection = 0.0
fors_pmos_calib.param.wdegree = 0
fors_pmos_calib.param.wradius = 4
fors_pmos_calib.param.wreject = 0.7
fors_pmos_calib.param.wcolumn = "WLEN"
fors_pmos_calib.param.cdegree = 0
fors_pmos_calib.param.cmode = 1
fors_pmos_calib.param.startwavelength = 0.0
fors_pmos_calib.param.endwavelength = 0.0
fors_pmos_calib.param.stack_method = "average"
fors_pmos_calib.param.minrejection = 1
fors_pmos_calib.param.maxrejection = 1
fors_pmos_calib.param.klow = 3.0
fors_pmos_calib.param.khigh = 3.0
fors_pmos_calib.param.kiter = 999
fors_pmos_calib.param.ddegree = -1
fors_pmos_calib.param.dradius = 10
fors_pmos_calib.param.qc = True
fors_pmos_calib.param.check = False

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

import cpl
fors_pmos_calib = cpl.Recipe("fors_pmos_calib")
[...]
res = fors_pmos_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.