The fors_pmos_extract recipe

fors_pmos_extract

Synopsis

Extraction of scientific spectra

Description

This recipe is used to reduce scientific spectra using the extraction mask and the products created by the recipe fors_mpol_calib. The spectra are bias subtracted, flat fielded (if a normalised flat field is specified) and remapped eliminating the optical distortions. The wavelength calibration can be optionally upgraded using a number of sky lines: if no sky lines catalog of wavelengths is specified, an internal one is used instead.

If the alignment to the sky lines is performed, the input dispersion coefficients table is upgraded and saved to disk, and a new CCD wavelengths map is created.

This recipe accepts both FORS1 and FORS2 frames. 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).

Either a scientific or a standard star exposure can be specified in input.

The acronym SCI on products should be read STD in case of standard stars observations.

Input files

DO category:               Type:       Explanation:         Required:
SCIENCE_PMOS                  Raw         Scientific exposure     Y
or STANDARD_PMOS              Raw         Standard star exposure  Y
MASTER_BIAS                   Calib       Master bias             Y
GRISM_TABLE                   Calib       Grism table             .

MASTER_SKYLINECAT             Calib       Sky lines catalog       .


MASTER_NORM_FLAT_PMOS         Calib       Normalised flat field   .

DISP_COEFF_PMOS               Calib       Inverse dispersion      Y
CURV_COEFF_PMOS               Calib       Spectral curvature      Y
SLIT_LOCATION_PMOS            Calib       Slits positions table   Y
RETARDER_WAVEPLATE_CHROMATISM Calib       Chromatism correction   .

Output files

DO category:               Data type:  Explanation:
REDUCED_SCI_PMOS             FITS image  Extracted scientific spectra
REDUCED_SKY_SCI_PMOS         FITS image  Extracted sky spectra
REDUCED_ERROR_SCI_PMOS       FITS image  Errors on extracted spectra
REDUCED_SCI_X_PMOS           FITS image  X Stokes parameter (and L)
REDUCED_ERROR_X_PMOS         FITS image  Error on X Stokes parameter
REDUCED_NUL_X_PMOS           FITS image  Null parameter for X
REDUCED_POL_ANGLE_PMOS       FITS image  Direction of linear polarization
REDUCED_POL_ANGLE_ERROR_PMOS FITS image  Error on polarization direction
UNMAPPED_SCI_PMOS            FITS image  Sky subtracted scientific spectra
MAPPED_SCI_PMOS              FITS image  Rectified scientific spectra
MAPPED_ALL_SCI_PMOS          FITS image  Rectified science spectra with sky
MAPPED_SKY_SCI_PMOS          FITS image  Rectified sky spectra
UNMAPPED_SKY_SCI_PMOS        FITS image  Sky on CCD
GLOBAL_SKY_SPECTRUM_PMOS     FITS table  Global sky spectrum
OBJECT_TABLE_SCI_PMOS        FITS table  Positions of detected objects
OBJECT_TABLE_POL_SCI_PMOS    FITS table  Positions of real objects

Only if the sky-alignment of the wavelength solution is requested:
DISP_COEFF_SCI_PMOS          FITS table  Upgraded dispersion coefficients
WAVELENGTH_MAP_SCI_PMOS      FITS image  Upgraded wavelength map

Constructor

cpl.Recipe("fors_pmos_extract")

Create an object for the recipe fors_pmos_extract.

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

Parameters

fors_pmos_extract.param.dispersion

Resampling step (Angstrom/pixel) (float; default: 0.0) [default=0.0].

fors_pmos_extract.param.skyalign

Polynomial order for sky lines alignment, or -1 to avoid alignment (int; default: 0) [default=0].

fors_pmos_extract.param.wcolumn

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

fors_pmos_extract.param.startwavelength

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

fors_pmos_extract.param.endwavelength

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

fors_pmos_extract.param.flux

Apply flux conservation (bool; default: True) [default=True].

fors_pmos_extract.param.flatfield

Apply flat field (bool; default: False) [default=False].

fors_pmos_extract.param.skyglobal

Subtract global sky spectrum from CCD (bool; default: False) [default=False].

fors_pmos_extract.param.skymedian

Sky subtraction from extracted slit spectra (bool; default: False) [default=False].

fors_pmos_extract.param.skylocal

Sky subtraction from CCD slit spectra (bool; default: True) [default=True].

fors_pmos_extract.param.cosmics

Eliminate cosmic rays hits (only if global sky subtraction is also requested) (bool; default: False) [default=False].

fors_pmos_extract.param.slit_margin

Number of pixels to exclude at each slit in object detection and extraction (int; default: 3) [default=3].

fors_pmos_extract.param.ext_radius

Maximum extraction radius for detected objects (pixel) (int; default: 6) [default=6].

fors_pmos_extract.param.cont_radius

Minimum distance at which two objects of equal luminosity do not contaminate each other (pixel) (int; default: 0) [default=0].

fors_pmos_extract.param.ext_mode

Object extraction method: 0 = aperture, 1 = Horne optimal extraction (int; default: 1) [default=1].

fors_pmos_extract.param.time_normalise

Normalise output spectra by the exposure time (bool; default: True) [default=True].

fors_pmos_extract.param.chromatism

Chromatism correction to polarization angles (bool; default: True) [default=True].

fors_pmos_extract.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_extract = cpl.Recipe("fors_pmos_extract")

fors_pmos_extract.param.dispersion = 0.0
fors_pmos_extract.param.skyalign = 0
fors_pmos_extract.param.wcolumn = "WLEN"
fors_pmos_extract.param.startwavelength = 0.0
fors_pmos_extract.param.endwavelength = 0.0
fors_pmos_extract.param.flux = True
fors_pmos_extract.param.flatfield = False
fors_pmos_extract.param.skyglobal = False
fors_pmos_extract.param.skymedian = False
fors_pmos_extract.param.skylocal = True
fors_pmos_extract.param.cosmics = False
fors_pmos_extract.param.slit_margin = 3
fors_pmos_extract.param.ext_radius = 6
fors_pmos_extract.param.cont_radius = 0
fors_pmos_extract.param.ext_mode = 1
fors_pmos_extract.param.time_normalise = True
fors_pmos_extract.param.chromatism = True
fors_pmos_extract.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_extract = cpl.Recipe("fors_pmos_extract")
[...]
res = fors_pmos_extract( ..., param = {"dispersion":0.0, "skyalign":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.