The vmmosstandard recipe

vmmosstandard

Synopsis

Reduce a MOS standard star exposure.

Description

This recipe is used to calibrate and extract a standard star spectrum obtained in MOS mode, and compare it with a catalog spectrum to obtain the efficiency and the response curves.

Input files

DO category:               Type:      Explanation:         Required:
MOS_STANDARD               Raw        Science exposure        Y
MASTER_BIAS                Calib      Master bias             Y
EXTINCT_TABLE              Calib      Atmospheric extinction  Y
STD_FLUX_TABLE             Calib      Standard star fluxes    Y
MASTER_DARK                Calib      Master dark             .

MOS_MASTER_SCREEN_FLAT     Calib      Normalised flat field   .

EXTRACT_TABLE              Calib      Extraction table        .

GRISM_TABLE                Calib      Grism table             Y
CCD_TABLE                  Calib      Bad pixel table         .

Output files

DO category:               Data type: Explanation:
MOS_STANDARD_REDUCED       FITS image Extracted spectrum
MOS_STANDARD_EXTRACTED     FITS image Sky subtracted slit spectra
MOS_STANDARD_SKY           FITS image Sky slit spectra
MOS_STANDARD_SKY_EXTRACTED FITS image Extracted sky spectrum
OBJECT_TABLE               FITS table Objects spectra identification
WINDOW_TABLE               FITS table Objects positions in slit
MOS_SPECPHOT_TABLE         FITS table Efficiency and response curves

The standard star spectrum is calibrated and extracted as described for the recipe vmmosobsstare. The extracted spectrum is compared to catalog fluxes of the same star to obtain the efficiency curve and the response curve to use for flux calibration. For this comparison the extracted spectrum is converted into electrons/sec/Angstrom. The catalog fluxes, as well as the atmospheric extinction factors, are remapped to the same wavelength bins of the extracted spectrum. After removing the effect of the atmospheric extinction (i.e., correcting the extracted spectrum to airmass zero), the response curve is derived as the ratio between the catalog spectrum and the calibrated spectrum.

The efficiency curve is obtained by dividing the extracted spectrum in electrons/sec/Angstrom by the the catalog fluxes converted from erg/cm/cm/s/Angstrom to photons/s/Angstrom (at 100% efficiency each photon would correspond to one electron).

For more details, please refer to the VIMOS Pipeline User’s Guide.

Constructor

cpl.Recipe("vmmosstandard")

Create an object for the recipe vmmosstandard.

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

Parameters

vmmosstandard.param.BiasMethod

Bias removal method. (str; default: ‘Zmaster’) [default=”Zmaster”].

vmmosstandard.param.SkyMethod

Sky level determination method. (str; default: ‘Median’) [default=”Median”].

vmmosstandard.param.PolyOrder

Degree of polynomial used when the SkyMethod is set to Fit. (int; default: 0) [default=0].

vmmosstandard.param.SkyKSigmaLow

Low threshold for K-sigma rejection in sky fitting. (float; default: 3.0) [default=3.0].

vmmosstandard.param.SkyKSigmaHigh

High threshold for K-sigma rejection in sky fitting. (float; default: 3.0) [default=3.0].

vmmosstandard.param.Fuzz

Extra pixels from expected position of spectrum edge in extraction. (int; default: 5) [default=5].

vmmosstandard.param.SlitMargin

Number of excluded pixels at slit ends in object search or in sky level determination. (int; default: 2) [default=2].

vmmosstandard.param.LineWidth

Size of spectrum to extract around any skyline. (int; default: 16) [default=16].

vmmosstandard.param.DetectionLevel

Object detection level in units of sigma. (float; default: 10.0) [default=10.0].

vmmosstandard.param.WatershedLevels

Number of levels in the watershed method in object detection. (int; default: 32) [default=32].

vmmosstandard.param.WatershedFraction

Flux fraction to use in watershed. (float; default: 0.01) [default=0.01].

vmmosstandard.param.MinObjectSize

Minimal size for an object candidate to be considered an object. (int; default: 2) [default=2].

vmmosstandard.param.MaxObjectSize

Maximal size for an object candidate for not trying deblend into sub- objects. (int; default: 7) [default=7].

vmmosstandard.param.CleanBadPixel

Bad pixel correction on MOS science exposure. (bool; default: True) [default=True].

vmmosstandard.param.HorneExtraction

Use 1D Horne extraction. (bool; default: False) [default=False].

vmmosstandard.param.ModelSlit

Model wavelength solution within each slit. (bool; default: True) [default=True].

vmmosstandard.param.ModelSlitOrder

Order of polynomial for wavelength solution modeling within each slit. (int; default: 0) [default=0].

vmmosstandard.param.UseSkylines

Use sky lines to refine the wavelength calibration (bool; default: True) [default=True].

vmmosstandard.param.ResponseOrder

Order of the polynomial used to smooth the instrument response curve. (int; default: 5) [default=5].

vmmosstandard.param.ReduceAnyFrame

Reduce any frame. (bool; default: False) [default=False].

vmmosstandard.param.ComputeQC

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

vmmosstandard.param.SelectSlit

Slit containing the standard star. (int; default: 0) [default=0].

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

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

vmmosstandard.param.BiasMethod = "Zmaster"
vmmosstandard.param.SkyMethod = "Median"
vmmosstandard.param.PolyOrder = 0
vmmosstandard.param.SkyKSigmaLow = 3.0
vmmosstandard.param.SkyKSigmaHigh = 3.0
vmmosstandard.param.Fuzz = 5
vmmosstandard.param.SlitMargin = 2
vmmosstandard.param.LineWidth = 16
vmmosstandard.param.DetectionLevel = 10.0
vmmosstandard.param.WatershedLevels = 32
vmmosstandard.param.WatershedFraction = 0.01
vmmosstandard.param.MinObjectSize = 2
vmmosstandard.param.MaxObjectSize = 7
vmmosstandard.param.CleanBadPixel = True
vmmosstandard.param.HorneExtraction = False
vmmosstandard.param.ModelSlit = True
vmmosstandard.param.ModelSlitOrder = 0
vmmosstandard.param.UseSkylines = True
vmmosstandard.param.ResponseOrder = 5
vmmosstandard.param.ReduceAnyFrame = False
vmmosstandard.param.ComputeQC = True
vmmosstandard.param.SelectSlit = 0

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

import cpl
vmmosstandard = cpl.Recipe("vmmosstandard")
[...]
res = vmmosstandard( ..., param = {"BiasMethod":"Zmaster", "SkyMethod":"Median"})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to ESO VIMOS Pipeline Team. Alternatively, you may send a report to the ESO User Support Department.