Standard star with the Fiber MOS

Mode:

Standard star with the FIBER MOS

Usage:

Offline, Online

Key:

MegaraMosStdStar

Recipe:

MOSStandardRecipe

Recipe input:

MOSStandardRecipeInput

Recipe result:

MOSStandardRecipeResult

This observing mode includes the required actions to obtain those calibration images needed to correct for the variation in the response of the system along the spectral direction. The difference between this mode and the two precedent observing modes is that in this case the spectrophotometric standard star is observed through one of the robotic positioners of the Fiber-MOS subsystem.

As in Standard star with the IFUs observing modes, the calibration is performed by observing one or several spectrophotometric stars with the same instrument configuration that for the scientific observations. Depending on the number of standard stars observed and the weather conditions two different types of calibration could be achieved, absolute or relative. In the case of the former calibration an aperture correction should be applied to take into account the possible flux losses from the standard stars when observed through one of the ~1.6-arcsec-wide robotic positioners.

Requirements

This mode requires having the focal-plane cover configured, the instrument shutter open, to configure the VPH mechanism to select the grating to be used, to set the instrument mode to Fiber MOS, to move the focusing mechanism to the position pre-defined for the specific VPH of choice, to move one of the robotic positioners to the position of the spectrophotometric standard star (other positioners could be also moved if needed) and to expose a certain time and to readout the detector in a series of exposures, being this series the image set containing the spectral energy distribution of the spectrophotometric standard star.

This observing mode could still be carried out with one of the sides of the focal-plane cover closed. However, as the (commonly rather bright) spectrophotometric standard star is the only object of interest in the field, the other positioners would not be observing scientific targets, so the level of cross-talk between these and the positioner devoted to the standard star should be negligible. Thus, the use of the focal-plane cover, although considered, is not recommended for this specific observing mode.

In order to place the robotic positioner(s) on the corresponding target(s) a set of input catalogues previously generated by the observer using MOPSS (MEGARA Observing Preparation Software Suite) are needed.

Products

Standard star image sets are to be obtained only as part of the routine calibration activities performed by the observer that are needed for processing data for scientific exploitation.

Recipe, inputs and results

class megaradrp.recipes.calibration.mosstdstar.MOSStandardRecipe(*args, **kwargs)

Process MOS Standard Star Recipe.

This recipe processes a set of images obtained in MOS Stardard Star image mode and returns the total flux of the star.

Notes

Images provided by obresult are trimmed and corrected from overscan, bad pixel mask (if master_bpm is not None), bias, dark current (if master_dark is not None) and slit-flat (if master_slitflat is not None).

Images thus corrected are then stacked using the median. The result of the combination is saved as an intermediate result, named ‘reduced_image.fits’. This combined image is also returned in the field reduced_image of the recipe result.

The apertures in the 2D image are extracted, using the information in master_apertures and resampled according to the wavelength calibration in master_wlcalib. Then is divided by the master_fiberflat. The resulting RSS is saved as an intermediate result named ‘reduced_rss.fits’. This RSS is also returned in the field reduced_rss of the recipe result.

The sky is subtracted by combining the the fibers marked as SKY in the fibers configuration. The RSS with sky subtracted is returned ini the field final_rss of the recipe result.

The flux of the star is computed by adding the 7 fibers corresponding to the bundle containing the star and returned as star_spectrum.

class MOSStandardRecipeInput(*args, **kwds)

MOSStandardRecipeInput documentation.

Attributes:
degrade_resolution_methodstr, requirement, optional, default=fixed

Method to degrade the resolution

degrade_resolution_targetstr, requirement, optional, default=object

Spectrum with higher resolution

diffuse_light_imageDiffuseLightCorrection, requirement, optional

Diffuse light correction image

extraction_offsetListOfType, requirement, optional, default=[0.0]

Offset traces for extraction

ignored_sky_bundlesListOfType, requirement, optional

Ignore these sky bundles

master_aperturesMultiType, requirement

Apertures information for extraction

master_biasMasterBias, requirement

Master BIAS image

master_bpmMasterBPM, requirement, optional

Master Bad Pixel Mask

master_darkMasterDark, requirement, optional

Master DARK image

master_fiberflatMasterFiberFlat, requirement

Master fiber flat calibration

master_sensitivityMasterSensitivity, requirement, optional

Master sensitivity for flux calibration

master_slitflatMasterSlitFlat, requirement, optional

Master slit flat calibration

master_twilightMasterTwilightFlat, requirement, optional

Master twlight flat calibration

master_wlcalibWavelengthCalibration, requirement

Wavelength calibration table

methodstr, requirement, optional, default=median

Combination method

method_kwargsdict, requirement, optional

Arguments for combination method

obresultObservationResultType, requirement

Observation Result

positionPoint2D, requirement, optional

Position of the reference object

reference_extinctionReferenceExtinctionTable, requirement

Reference extinction

reference_spectrumReferenceSpectrumTable, requirement

Spectrum of reference star

reference_spectrum_velocityfloat, requirement, optional

Radial velocity of reference spectrum

relative_thresholdfloat, requirement, optional, default=0.3

Threshold for peak detection

sigma_resolutionfloat, requirement, optional, default=20.0

sigma Gaussian filter to degrade resolution

sky_rssSkyRSS, requirement, optional

Row Stacked Spectra of the sky

smoothing_knotsMultiType, requirement, optional, default=3

List of nodes or number of nodes for sensitivity smoothing

class MOSStandardRecipeResult(*args, **kwds)

MOSStandardRecipeResult documentation.

Attributes:
fiber_idsArrayType, product
final_rssProcessedRSS, product
master_sensitivityMasterSensitivity, product
reduced_imageProcessedFrame, product
reduced_rssProcessedRSS, product
sensitivity_rawProcessedSpectrum, product
sigmafloat, product
sky_rssProcessedRSS, product
star_spectrumProcessedSpectrum, product
RecipeInput

alias of MOSStandardRecipeInput

RecipeResult

alias of MOSStandardRecipeResult