Extracted Spectra Collection Product

Metadata

Data product name

DpdSirExtractedSpectraCollection

Data product custodian

SIR

Name of the Schema file

euc-sir-ExtractedSpectraCollection.xsd <https://gitlab.euclid-sgs.uk/ST-DM/ST_DataModel/-/b lob/10.1.2/ST_DM_Schema/auxdir/ST_DM_Schema/dpd/sir/euc-sir-ExtractedSpectraCollection.xsd> _

Processing function using the data product

SIR

Proposed for inclusion in EAS/SAS

This product is proposed for inclusion in the SAS: no

This is an internal Data Product, part of its content will be stored in the euc-sir-CombinedSpectra.xsd.

Data product elements

Header

object of type sys:genericHeader

Data

object of type sir:genericSirCollection

QualityFlags

object of type dqc:sqfPlaceHolder

Parameters

object of type ppr:genericKeyValueParameters

Detailed description of the data product

The SIR_SpectraExtraction works on decontaminated spectra: it uses the LocationTable to extract 2D and 1D spectra linearly resampled, lambda calibrated and without distortions.

For each 1 st order LocationSpectrum in the LocationTable one ExtractedSpectrum is produced.

../../_images/ExtractedSpectrum.png

Fig. 45 : The ExtractedSpectrum structure.

The ExtractedSpectrum (cyan box in Fig. 45) is the atomic part of the ExtractedSpectraCollection, it contains:

  • The AstronomicalObject group (see Astronomical Object group description).

  • The CONTAMINANTS dataset: the list of contaminants identified and removed during the decontamination step.

  • The DATA group: a collection of SpectrumDataset (purple box in Fig. 45), structures designed to contain spectral data like the science array, the variance and so on (see the next paragraph for further details). SpectrumDataSets gathered in the DATA group are:

    • 2D: the 2D spectrum (counts)

    • 1D: the 1D spectrum (counts)

    • 1D REL: the 1D spectrum relative flux calibrated

    • 1D FLUX: the 1D spectrum absolute flux calibrated

    • CUTOUT_TRANS: the 2D imaging cutout at the SIR resolution (rotated, rebinned, PSF convolved) and with the shear applied for the virtual slit

    • LSF: profile of the Line Spread Function obtained by summing the cutout in the cross-dispersion direction

    • SLIT PROFILE: slit profile obtained by summing the cutout in the dispersion direction

  • The LOCATION group (see Location Object group description).

SpectrumDataset

SpectrumDataset represents an extracted spectrum (2D or 1D, flux calibrated or not), it collects all the information related to one extracted spectrum decontaminated, linearly wavelength calibrated and corrected by the distortions. The dispersion direction is along the X axis, while the spatial direction is along the Y axis.

All these spectra have the same wavelength solution, for this reason the pixel to lambda relation is described once for all, at the level of the DATA group by these 3 attributes:

  • Wlen start: value of starting wavelength [\(\mathring{A}\)]

  • Wlen inc: the increment step [\(\mathring{A}\)]

  • Wlen end: value of last wavelength [\(\mathring{A}\)]

Each SpectrumDataSet group contains 4 layers (4 HDF5 dataset) of the same shape. The layers are:

  • Science: the layer containing the values of the extracted spectrum.

  • Variance: the variance values of each point of the Science layer.

  • The Quality layer contains values between 0 and 1; it is the percentage of pixels used (during 2D resample and/or 1D extraction) to obtain a science point.

  • The bit Mask layer which gives info about every single points in the Science layer. Bit mask values are:

    • 1: DO_NOT_USE;

    • 2: LOW_SNR, low S/N (resampling/combination was based on a significantly smaller-than-expected);

    • 4: SUSP_EXTR, suspicious spectrum extraction (e.g. x-disp. profiles from thumbnail and spectrogram don’t match);

    • 8: SUSP_HIGH, suspected high (during extrac./combin., at least one px looked suspiciously high yet included);

    • 16: SUSP_LOW, suspected low (during extrac./combin., at least one px looked suspiciously low yet included);

    • 32: SUSP_RFX, suspicious relative flux scaling (scale or associated error);

    • 64: SUSP_AFX, suspicious absolute flux scaling (scale or associated error).

Finally, attributes of the SpectrumDataSet layer are:

  • Exptime: the spectrum exposure time

  • LSF sigma: the line spread function of the Spectrum

  • Normalization factor: normalization factor to apply to dataset values

  • Tolerance: tolerance threshold used in covariance computation (-1 means covariance computation is disabled, which is the current configuration of the SIR_Pipeline)

DataContainer file name description

The following XML keywords:

  • Data.ObservationSequence.ObservationId (OBSID)

  • Data.ObservationSequence.DitherObservation (DITH)

  • Data.DetectorId (DETID)

are combined to create the DataContainer file name:

EUC_SIR_W-XTRACT_<OBSID>-<DITH>-DET_<DETID>_<TIMESTAMP>.h5

Here below and example:

EUC_SIR_W-XTRACT_65879-1-DET_13_20250410T165921.565547Z.h5