Determines response function and quantum efficiency
This recipe reduces a standard star frame (STANDARD_xxx or STANDARD_xxx, where xxx = BLUE, RED) using a combination (depending on recipe parameters and provided input frames) of the steps:
- bias subtraction,
- dark subtraction,
- background subtraction,
- extraction/cosmic ray removal,
- flat-field correction,
- wavelength rebinning,
- sky subtraction,
- order merging.
Expected input for this recipe is an raw std star frame, STANDARD_xxx or
order table(s) for each chip, ORDER_TABLE_xxxx (where xxxx=BLUE, REDL, REDU), line table(s) for each chip, LINE_TABLE_xxxx, a master bias frame, MASTER_BIAS_xxxx, a master flat, MASTER_FLAT_xxxx, a reference standard star flux table, FLUX_STD_TABLE, a table describing the atmospheric extintion, EXTCOEFF_TABLE. Two reductions are performed, the first using optimal extraction (used to compute the instrument response function), the second using linear extraction (used to get the Quantum Detection Efficiency)
For each chip (xxxx = BLUE, REDL, REDU) the recipe produces
INSTR_RESPONSE_xxxx Response curve
WCALIB_FF_RESPONSE_xxxx Response curve in (lambda,order) space before
correcting for exposure time, gain, binning and
atmospheric absorption
RED_STD_xxxx Reduced spectrum
EFFICIENCY_TABLE_xxxx Efficiency table
BKG_STD_xxxx The subtracted background
Create an object for the recipe uves_cal_response.
import cpl
uves_cal_response = cpl.Recipe("uves_cal_response")
Whether or not to save intermediate results to local directory (bool; default: False) [default=False].
Any plots produced by the recipe are redirected to the command specified by this parameter. The plotting command must contain the substring ‘gnuplot’ and must be able to parse gnuplot syntax on its standard input. Valid examples of such a command may include ‘gnuplot -persist’ and ‘cat > mygnuplot$$.gp’. A finer control of the plotting options can be obtained by writing an executable script, e.g. my_gnuplot.pl, that executes gnuplot after setting the desired gnuplot options (e.g. set terminal pslatex color). To turn off plotting, set this parameter to ‘no’ (str; default: ‘no’) [default=”no”].
For RED arm data process the redl, redu, or both chip(s) (str; default: ‘both’) [default=”both”].
The pointing accuracy (in arcseconds) used to identify the observed star with a catalogue star. If the angular separation is less than this number, the identification is made. (float; default: 60.0) [default=60.0].
Flat-fielding method. If set to ‘pixel’, flat-fielding is done in pixel-pixel space (before extraction); if set to ‘extract’, flat- fielding is performed in pixel-order space (i.e. after extraction). If set to ‘no’, no flat-field correction is done. <pixel | extract | no> (str; default: ‘no’) [default=”no”].
Order merging method. If ‘optimal’, the flux in the overlapping region is set to the (optimally computed, using the uncertainties) average of single order spectra. If ‘sum’, the flux in the overlapping region is computed as the sum of the single order spectra.If ‘noappend’ the spectrum is simply rebinned but not merged.If flat-fielding is done, method ‘optimal’ is recommended, otherwise ‘sum’. <optimal | sum | noappend> (str; default: ‘sum’) [default=”sum”].
(optimal extraction only) If false (fastest), the spectrum is extracted only once. If true (best), the spectrum is extracted twice, the second time using improved variance estimates based on the first iteration. Better variance estimates slightly improve the obtained signal to noise but at the cost of increased execution time (bool; default: True) [default=True].
Extraction method. <average | linear | weighted | optimal> (str; default: ‘linear’) [default=”linear”].
Extraction slit length (in pixels). If negative, the value inferred from the raw frame header is used (float; default: -1.0) [default=-1.0].
Do sky-subtraction (only applicable to linear and average extractions)? (bool; default: True) [default=True].
Offset (in pixels) of extraction slit with respect to center of order. This parameter applies to linear/average/optimal extraction. For linear/average extraction, if the related parameter objslit is negative, the offset is automatically determined by measuring the actual object position. (float; default: 0.0) [default=0.0].
Object window size (in pixels). This must be less than the total slit length. If negative, the default value (half of full slit length) is used. The upper and lower sky windows are defined as the part of the full slit (if any) outside the object window. The center of the object window is determined by the offset parameter. This parameter does not apply to optimal extraction. (float; default: -1.0) [default=-1.0].
If enabled (recommended), the provided dispersion solutions obtained at different slit positions are interpolated linearly at the actually measured position of the object/sky. Line tilt correction is currently not supported for 2d extraction, in which case the dispersion solution obtained at the middle of the slit is always used. (bool; default: True) [default=True].
Flat-fielding method. If set to ‘pixel’, flat-fielding is done in pixel-pixel space (before extraction); if set to ‘extract’, flat- fielding is performed in pixel-order space (i.e. after extraction). If set to ‘no’, no flat-field correction is done (str; default: ‘extract’) [default=”extract”].
Order merging method. If ‘optimal’, the flux in the overlapping region is set to the (optimally computed, using the uncertainties) average of single order spectra. If ‘sum’, the flux in the overlapping region is computed as the sum of the single order spectra. If ‘noappend’ the spectrum is simply rebinned but not merged.If flat-fielding is done, method ‘optimal’ is recommended, otherwise ‘sum’. (str; default: ‘optimal’) [default=”optimal”].
Order merging left hand (short wavelength) cut. To reduce the amount of order overlapping regions we allow to cut short and long wavelength ranges. This may reduce the ripple possibly introduced by the order merging. Suggested values are: 10 (W<=390), 12 (390<W<=437, 520<W<=564), 14 (437<W<=520, 564<W) (float; default: 0.0) [default=0.0].
Order merging right hand (long wavelength) cut. To reduce the amount of order overlapping regions we allow to cut short and long wavelength ranges. This may reduce the ripple possibly introduced by the order merging. Suggested values is 4 (float; default: 0.0) [default=0.0].
The bin size (in w.l.u.) in wavelength space. If negative, a step size of 2/3 * ( average pixel size ) is used. (float; default: -1.0) [default=-1.0].
Whether or not to multiply by the factor dx/dlambda (pixels per wavelength) during the rebinning. This option is disabled as default in concordance with the method used in the MIDAS pipeline. This option should be set to true to convert the observed flux (in pixel-space) to a flux per wavelength (in wavelength-space). (bool; default: False) [default=False].
Background measuring method. If equal to ‘median’ the background is sampled using the median of a subwindow. If ‘minimum’, the subwindow minimum value is used. If ‘no’, no background subtraction is done. (str; default: ‘median’) [default=”median”].
This is the number of columns in interorder space used to sample the background. (long; default: 82) [default=82].
The height (in pixels) of the background sampling window is (2*radiusy + 1). This parameter is not corrected for binning. (long; default: 2) [default=2].
Degree of interpolating splines. Currently only degree = 1 is supported (long; default: 1) [default=1].
If spline interpolation is used to measure the background, the x-radius of the post-smoothing window is (smoothx * image_width). Here, ‘image_width’ is the image width after binning. If negative, the default values are used: (25.0/4096) for blue flat-field frames, (50.0/4096) for red flat-field frames, (300.0/4096) for blue science frames and (300.0/4096) for red science frames. (float; default: -1.0) [default=-1.0].
If spline interpolation is used to measure the background, the y-radius of the post-smoothing window is (smoothy * image_height). Here, ‘image_height’ is the image height after binning. If negative, the default values are used: (100.0/2048) for blue flat-field frames, (300.0/2048) for red flat-field frames, (200.0/2048) for blue science frames and (500.0/2048) for red science frames. (float; default: -1.0) [default=-1.0].
Extraction method. (2d/optimal not supported by uves_cal_wavecal, weighted supported only by uves_cal_wavecal, 2d not supported by uves_cal_response) (str; default: ‘optimal’) [default=”optimal”].
In optimal extraction mode, this is the threshold for bad (i.e. hot/cold) pixel rejection. If a pixel deviates more than kappa*sigma (where sigma is the uncertainty of the pixel flux) from the inferred spatial profile, its weight is set to zero. Range: [-1,100]. If this parameter is negative, no rejection is performed. (float; default: 10.0) [default=10.0].
In optimal extraction mode, the chunk size (in pixels) used for fitting the analytical profile (a fit of the analytical profile to single bins would suffer from low statistics). (long; default: 32) [default=32].
In optimal extraction mode, the kind of profile to use. ‘gauss’ gives a Gaussian profile, ‘moffat’ gives a Moffat profile with beta=4 and a possible linear sky contribution. ‘virtual’ uses a virtual resampling algorithm (i.e. measures and uses the actual object profile). ‘constant’ assumes a constant spatial profile and allows optimal extraction of wavelength calibration frames. ‘auto’ will automatically select the best method based on the estimated S/N of the object. For low S/N, ‘moffat’ or ‘gauss’ are recommended (for robustness). For high S/N, ‘virtual’ is recommended (for accuracy). In the case of virtual resampling, a precise determination of the order positions is required; therefore the order-definition is repeated using the (assumed non-low S/N) science frame (str; default: ‘auto’) [default=”auto”].
In optimal extraction mode, the sky subtraction method to use. ‘median’ estimates the sky as the median of pixels along the slit (ignoring pixels close to the object), whereas ‘optimal’ does a chi square minimization along the slit to obtain the best combined object and sky levels. The optimal method gives the most accurate sky determination but is also a bit slower than the median method (str; default: ‘optimal’) [default=”optimal”].
The oversampling factor used for the virtual resampling algorithm. If negative, the value 5 is used for S/N <=200, and the value 10 is used if the estimated S/N is > 200 (long; default: -1) [default=-1].
(optimal extraction only) If false (fastest), the spectrum is extracted only once. If true (best), the spectrum is extracted twice, the second time using improved variance estimates based on the first iteration. Better variance estimates slightly improve the obtained signal to noise but at the cost of increased execution time (bool; default: True) [default=True].
The following code snippet shows the default settings for the available parameters.
import cpl
uves_cal_response = cpl.Recipe("uves_cal_response")
uves_cal_response.param.debug = False
uves_cal_response.param.plotter = "no"
uves_cal_response.param.process_chip = "both"
uves_cal_response.param.paccuracy = 60.0
uves_cal_response.param.efficiency.reduce.ffmethod = "no"
uves_cal_response.param.efficiency.reduce.merge = "sum"
uves_cal_response.param.efficiency.reduce.best = True
uves_cal_response.param.efficiency.reduce.extract.method = "linear"
uves_cal_response.param.reduce.slitlength = -1.0
uves_cal_response.param.reduce.skysub = True
uves_cal_response.param.reduce.objoffset = 0.0
uves_cal_response.param.reduce.objslit = -1.0
uves_cal_response.param.reduce.tiltcorr = True
uves_cal_response.param.reduce.ffmethod = "extract"
uves_cal_response.param.reduce.merge = "optimal"
uves_cal_response.param.reduce.merge_delt1 = 0.0
uves_cal_response.param.reduce.merge_delt2 = 0.0
uves_cal_response.param.reduce.rebin.wavestep = -1.0
uves_cal_response.param.reduce.rebin.scale = False
uves_cal_response.param.reduce.backsub.mmethod = "median"
uves_cal_response.param.reduce.backsub.npoints = 82
uves_cal_response.param.reduce.backsub.radiusy = 2
uves_cal_response.param.reduce.backsub.sdegree = 1
uves_cal_response.param.reduce.backsub.smoothx = -1.0
uves_cal_response.param.reduce.backsub.smoothy = -1.0
uves_cal_response.param.reduce.extract.method = "optimal"
uves_cal_response.param.reduce.extract.kappa = 10.0
uves_cal_response.param.reduce.extract.chunk = 32
uves_cal_response.param.reduce.extract.profile = "auto"
uves_cal_response.param.reduce.extract.skymethod = "optimal"
uves_cal_response.param.reduce.extract.oversample = -1
uves_cal_response.param.reduce.extract.best = True
You may also set or overwrite some or all parameters by the recipe parameter param, as shown in the following example:
import cpl
uves_cal_response = cpl.Recipe("uves_cal_response")
[...]
res = uves_cal_response( ..., param = {"debug":False, "plotter":"no"})
See also
cpl.Recipe for more information about the recipe object.
Please report any problems to Jonas M. Larsen. Alternatively, you may send a report to the ESO User Support Department.
This file is part of the FLAMES/UVES Pipeline Copyright (C) 2004, 2005, 2006, 2007 European Southern Observatory
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02111-1307 USA
Code author: Jonas M. Larsen <cpl@eso.org>