The muse_standard recipe



Create a flux response curve from a standard star exposure.


Merge pixel tables from all IFUs and correct for differential atmospheric refraction, when necessary. To derive the flux response curve, integrate the flux of all objects detected within the field of view using the given profile. Select one object as the standard star (either the brightest or the one nearest one, depending on –select) and compare its measured fluxes to tabulated fluxes to derive the sensitivity over wavelength. Postprocess this sensitivity curve to mark wavelength ranges affected by telluric absorption. Interpolate over the telluric regions and derive a telluric correction spectrum for them. The final response curve is then linearly extrapolated to the largest possible MUSE wavelength range and smoothed (with the method given by –smooth). The derivation of the telluric correction spectrum assumes that the star has a smooth spectrum within the telluric regions. If there are more than one exposure given in the input data, the derivation of the flux response and telluric corrections are done separately for each exposure. For each exposure, an image containing the extracted stellar spectra and the datacube used for flux integration are saved, together with collapsed images for each given filter. In MUSE’s WFM data (both AO and non-AO), the Moffat profile is a good approximation of the actual PSF. Using the smoothed profile (“smoffat”) helps to increase the S/N and in most cases removes systematics. In NFM, however, the profile is a combination of a wide PSF plus the central AO-corrected peak, which cannot be fit well by an analytical profile. In this case the circular aperture is the best way to extract the flux. Using –profile=”auto” (the default) selects these options to give the best flux extraction for most cases.



Create an object for the recipe muse_standard.

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



Type of flux integration to use. “gaussian”, “moffat”, and “smoffat” use 2D profile fitting, “circle” and “square” are non-optimal aperture flux integrators. “smoffat” uses smoothing of the Moffat parameters from an initial fit, to derive physically meaningful wavelength- dependent behavior. “auto” selects the smoothed Moffat profile for WFM data and circular flux integration for NFM. (str; default: ‘auto’) [default=”auto”].

How to select the star for flux integration, “flux” uses the brightest star in the field, “distance” uses the detection nearest to the approximate coordinates of the reference source. (str; default: ‘distance’) [default=”distance”].


How to smooth the response curve before writing it to disk. “none” does not do any kind of smoothing (such a response curve is only useful, if smoothed externally; “median” does a median-filter of 15 Angstrom half-width; “ppoly” fits piecewise cubic polynomials (each one across 2x150 Angstrom width) postprocessed by a sliding average filter of 15 Angstrom half-width. (str; default: ‘ppoly’) [default=”ppoly”].


Cut off the data below this wavelength after loading the pixel table(s). (float; default: 4000.0) [default=4000.0].


Cut off the data above this wavelength after loading the pixel table(s). (float; default: 10000.0) [default=10000.0].


Reference wavelength used for correction of differential atmospheric refraction. The R-band (peak wavelength ~7000 Angstrom) that is usually used for guiding, is close to the central wavelength of MUSE, so a value of 7000.0 Angstrom should be used if nothing else is known. A value less than zero switches DAR correction off. (float; default: 7000.0) [default=7000.0].


Carry out a check of the theoretical DAR correction using source centroiding. If “correct” it will also apply an empirical correction. (str; default: ‘none’) [default=”none”].


The filter name(s) to be used for the output field-of-view image. Each name has to correspond to an EXTNAME in an extension of the FILTER_LIST file. If an unsupported filter name is given, creation of the respective image is omitted. If multiple filter names are given, they have to be comma separated. If the zeropoint QC parameters are wanted, make sure to add “Johnson_V,Cousins_R,Cousins_I”. (str; default: ‘white’) [default=”white”].

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

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

muse_standard.param.profile = "auto" = "distance"
muse_standard.param.smooth = "ppoly"
muse_standard.param.lambdamin = 4000.0
muse_standard.param.lambdamax = 10000.0
muse_standard.param.lambdaref = 7000.0
muse_standard.param.darcheck = "none"
muse_standard.param.filter = "white"

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

import cpl
muse_standard = cpl.Recipe("muse_standard")
res = muse_standard( ..., param = {"profile":"auto", "select":"distance"})

See also

cpl.Recipe for more information about the recipe object.

Bug reports

Please report any problems to Peter Weilbacher. Alternatively, you may send a report to the ESO User Support Department.