The vmmoscalib recipe

vmmoscalib

Synopsis

Determination of the extraction mask

Description

This recipe is used to identify reference lines on MOS 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 vimos_science. The input arc lamp 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.

In the table below the MOS_CURV_COEFF, MOS_CURV_TRACES, MOS_SPATIAL_MAP MOS_ARC_SPECTRUM_EXTRACTED, MOS_SPECTRA_DETECTION, MOS_SLIT_MAP, and MOS_SLIT_LOCATION, are never created in case of long-slit-like data.

The products MOS_SPECTRA_DETECTION, MOS_SLIT_MAP, and MOS_DISP_RESIDUALS, are just created if the –check parameter is set to true. The product GLOBAL_DISTORTION_TABLE is just created if more than 12 separate spectra are found in the CCD.

Input files

DO category:               Type:       Explanation:         Required:
MOS_SCREEN_FLAT            Raw         Flat field exposures    Y
MOS_ARC_SPECTRUM           Raw         Arc lamp exposure       Y
MASTER_BIAS                Calib       Bias frame              Y
LINE_CATALOG               Calib       Line catalog            Y
CONFIG_TABLE               Calib       Grism table             .

Output files

DO category:               Data type:  Explanation:
MOS_COMBINED_SCREEN_FLAT   FITS image  Combined (sum) flat field
MOS_MASTER_SCREEN_FLAT     FITS image  Normalised flat field
MOS_ARC_SPECTRUM_EXTRACTED FITS image  Wavelength calibrated arc spectrum
MOS_DISP_COEFF             FITS table  Inverse dispersion coefficients
MOS_DISP_RESIDUALS         FITS image  Residuals in wavelength calibration
MOS_DISP_RESIDUALS_TABLE   FITS table  Residuals in wavelength calibration
MOS_DELTA_IMAGE            FITS image  Offset vs linear wavelength calib
MOS_WAVELENGTH_MAP         FITS image  Wavelength for each pixel on CCD
MOS_SPECTRA_DETECTION      FITS image  Check for preliminary detection
MOS_SLIT_MAP               FITS image  Map of central wavelength on CCD
MOS_CURV_TRACES            FITS table  Spectral curvature traces
MOS_CURV_COEFF             FITS table  Spectral curvature coefficients
MOS_SPATIAL_MAP            FITS image  Spatial position along slit on CCD
MOS_SPECTRAL_RESOLUTION    FITS table  Resolution at reference arc lines
MOS_SLIT_LOCATION          FITS table  Slits on product frames and CCD
GLOBAL_DISTORTION_TABLE    FITS table  Global distortions table

Constructor

cpl.Recipe("vmmoscalib")

Create an object for the recipe vmmoscalib.

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

Parameters

vmmoscalib.param.dispersion

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

vmmoscalib.param.peakdetection

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

vmmoscalib.param.wdegree

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

vmmoscalib.param.wradius

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

vmmoscalib.param.wreject

Rejection threshold in dispersion relation fit (pixel) (float; default: 1.0) [default=1.0].

vmmoscalib.param.wmodelss

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

vmmoscalib.param.wmodemos

Interpolation mode of wavelength solution (0 = no interpolation, 1 = local (slit) solution, 2 = global model) (int; default: 1) [default=1].

vmmoscalib.param.ignore_lines

Catalog lines nearest to wavelengths in this list will be ignored for wavelength calibration (str; default: ‘’) [default=””].

vmmoscalib.param.used_linesets

Linesets to use. Valid are ‘standard’ and’extended’ (see column LINE_SET in the line catalogue) (str; default: ‘standard’) [default=”standard”].

vmmoscalib.param.cdegree

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

vmmoscalib.param.cmode

Interpolation mode of curvature solution applicable to MOS-like data (0 = no interpolation, 1 = fill gaps, 2 = global model) (int; default: 1) [default=1].

vmmoscalib.param.startwavelength

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

vmmoscalib.param.endwavelength

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

vmmoscalib.param.reference

Reference wavelength for slit map (float; default: 0.0) [default=0.0].

vmmoscalib.param.slit_ident

Attempt slit identification.For multiplexing data slit identification is always performed. Switching it off will cause systematic errors in the absolute flux calibration if the FLAT_SED correction is used (see pipeline manual for details) (bool; default: True) [default=True].

vmmoscalib.param.s_degree

Polynomial degree for the flat field fitting along spatial direction (int; default: -1) [default=-1].

vmmoscalib.param.sradius

Smooth box radius for flat field along spatial direction (used if s_degree < 0) (int; default: -1) [default=-1].

vmmoscalib.param.d_nknots

Number of knots in flat field fitting splines along dispersion direction (int; default: -1) [default=-1].

vmmoscalib.param.dradius

Smooth box radius for flat field along dispersion direction (if d_knots < 0) (int; default: 10) [default=10].

vmmoscalib.param.fit_threshold

Threshold percentage for flat spline fitting with respect to the maximum (float; default: 0.01) [default=0.01].

vmmoscalib.param.line_ident_tol

Tolerance for the ratio of detected lines vs reference lines. This is used during for arc line identification. (float; default: 0.05) [default=0.05].

vmmoscalib.param.normalise_spa_local

If TRUE the normalization along the spatial axis is performed row-by- row otherwise a collapsed slit is used. (bool; default: True) [default=True].

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

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

vmmoscalib.param.dispersion = 0.0
vmmoscalib.param.peakdetection = 0.0
vmmoscalib.param.wdegree = 0
vmmoscalib.param.wradius = 4
vmmoscalib.param.wreject = 1.0
vmmoscalib.param.wmodelss = 2
vmmoscalib.param.wmodemos = 1
vmmoscalib.param.ignore_lines = ""
vmmoscalib.param.used_linesets = "standard"
vmmoscalib.param.cdegree = 0
vmmoscalib.param.cmode = 1
vmmoscalib.param.startwavelength = 0.0
vmmoscalib.param.endwavelength = 0.0
vmmoscalib.param.reference = 0.0
vmmoscalib.param.slit_ident = True
vmmoscalib.param.s_degree = -1
vmmoscalib.param.sradius = -1
vmmoscalib.param.d_nknots = -1
vmmoscalib.param.dradius = 10
vmmoscalib.param.fit_threshold = 0.01
vmmoscalib.param.line_ident_tol = 0.05
vmmoscalib.param.normalise_spa_local = True

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

import cpl
vmmoscalib = cpl.Recipe("vmmoscalib")
[...]
res = vmmoscalib( ..., 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.