SPIRE Spectral Feature Catalogue

2nd public release, September 2018

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Contributors

The Spectral Feature Finder project is lead by Rosalind Hopwood (1,2) and with significant contribution by Ivan Valtchanov (2), L. D. Spencer (3), J. Scott (3), C. Benson (3), N. Marchili (4), N. Hładczuk (2), E. T. Polehampton (5), N. Lu (6), G. Makiwa (3), D. A. Naylor (3), G. Noble (7), M. J. Griffin (8) and with valuable inputs from members of the no longer active SPIRE Instrument and Control Centre.

(1) Imperial College, London; (2) Herschel Science Centre, ESAC, ESA; (3) University of Lethbridge, Canada; (4) APS-INAF, Roma, Italy; (5) RAL Space, UK; (6) China-Chile Joint Center for Astronomy, Santiago, Chile; (7) University of British Columbia, Canada; (8) Cardiff University, UK


Abstract

The SPIRE Spectral Feature Finder Catalogue is the result of an automated run of the Spectral Feature Finder (FF). The FF is designed to extract significant spectral features from SPIRE FTS data products. These spectral features are only identified for High Resolution (HR) sparse or mapping observations, while for Low Resolution (LR) sparse or mapping observations the FF only provides the best fit continuum parameters.

The FF engine iteratively searches for peaks over a set of signal-to-noise ratio (SNR) thresholds, either in the HR spectra of the two central detectors (sparse mode) or in each pixel (SPIRE Long Wavelength - SLW, and SPIRE Short Wavelength - SSW) of the two hyper-spectral cubes (mapping). At the end of each iteration, independently for each spectral band, the FF simultaneously fits the continuum and the features found. The residual of the fit is used for the next iteration.

The final FF catalogue contains emission and absorption feature frequencies, and their respective SNR, for each observation; SNR is negative for absorption features. Line fluxes are not included as extracting reliable line flux from the FTS data is a complex process that requires careful evaluation and analysis of the associated spectra. Testing of the FF routine indicates that the FTS Spectral Feature Finder Catalogue is 100% complete for features above SNR=10, and 50-70% complete down to SNR=5.

The full SPIRE Automated Feature Extraction Catalogue (SAFECAT) contains 167,525 features at |SNR| >= 5 from 641 sparse and 179 mapping observations.

Important notes

  • No line fluxes are provided in the FF products. The iteratively detected features, in emission or in absorption, are given with their estimated local signal-to-noise ratio (SNR). SNR is negative for absorption features.
  • All frequency-depended results (spectral feature centroid, continua, postcards x-axis) are in the kinematic Local Standard of Rest (LSRk).
  • The radial velocities, available in the FF products metadata, are derived from the data (Scott J. et al., in preparation) or taken from publications. They should be used with caution.

All the details regarding the Feature Finder and the derived products are presented in the Release Note and in Hopwood et al., in preparation.

Access to the Spectral Feature Finder products

The FF products can be accessed in the Herschel Highly Processed Data Products Legacy Archive Area.

All products, postcards and documentation are available in FFv2_products.tar.gz tarball (564 MB).

FF catalogue variants

The FF products provided depend on spectral resolution and observing mode.

High resolution (HR)

There are three sub-folders of FF products for HR sparse-mode and mapping observations, each containing folders that provide: the individual FF feature catalogues; the fitted continua as Herschel spectral products and as polynomial coefficients; and the associated postcards.

  • HRpointProducts: contains FF products for point-source calibrated spectra
  • HRextProducts: contains FF products for extended-source calibrated spectra for those sparse-mode observations of sources with some spatial extent. For these observations it is important to consider both sets of FF results. For fully-extended sources there may be fewer spurious detections and a better spectral shape of the continua seen in the extended-source calibrated FF products.
  • HRmapping: contains FF products for mapping observations. Each spatial pixel in each of the two hyper-spectral cubes (for the two spectrometer arrays) is processed with the FeatureFinder and the results are stored in the output table.

hrSparseObservations.csv lists all HR observations for which there is a set of FF products and indicates the source extent of the source observed (pointLike, semiExtended or fullyExtended). If the source is known to be featureless, this is indicated in the knownFeatureless column, and there is no feature catalogue in the associated FF products. The dataUsed column indicates if special data was used, as explained in the Release Note.

The coma-separated-value files hrMappingObservations.csv, lrSparseObservations.csv and lrMappingObservations.csv provide a list of the OBSIDs used for the HR mapping and LR sparse and mapping observations respectively. For observations in H+LR mode the same OBSID will appear in both HR and LR lists.

In addition, the combined Spire Automated Feature Extraction CATalogue (SAFECAT), collates all features found for the point-source calibrated spectra of HR sparse and mapping mode observations.

Low resolution (LR)

For LR the best fit to the continua for the two spectral bands is provided, both as polynomial coefficients and as Herschel spectral products, along with the FF postcards. There are products for point-source calibrated spectra and extended-source calibrated spectra for all LR sparse-mode observations that were run with the FF.

The LR continua are also provided for spectral maps, both for the naive and convolution projection (CP) cube generation methods (see the SPIRE Data Reduction Guide for more details). For these observations the polynomial coefficients are provided for each cube pixel.

Individual FF catalogues and postcards

The FF catalogues can be accessed via a number of pages detailed in the tables below. The table provides links to the FF product tables in the left-hand column. The observations included on each page is given in the middle column, with the corresponding operational days in the right-hand column.

All products are described in greater detail in the Release Note. All individual feature catalogues, as well as SAFECAT, are provided as FITS files.

Go to page Observations covered Operational days
HR sparse-mode FF products
HR Sparse Page 1 1342187893 — 1342212341 209 — 602
HR Sparse Page 2 1342212342 — 1342231985 602 — 908
HR Sparse Page 3 1342231986 — 1342247763 908 — 1151
HR Sparse Page 4 1342247764 — 1342258698 1151 — 1335
HR Sparse Page 5 1342258699 — 1342270195 1335 — 1434
HR mapping-mode FF products
HR Mapping Page 1 1342192173 — 1342245117 302 — 1079
HR Mapping Page 2 1342245083 — 1342270045 1080 — 1433
LR sparse-mode FF products
LR Sparse Page 1 1342188674 — 1342248229 227 — 1160
LR Sparse Page 2 1342248245 — 1342257934 1160 — 1326
LR Sparse Page 3 1342259570 — 1342270194 1340 — 1434
LR intermediate and fully sampled mapping mode FF products
LR Mapping Page 1 1342192179 — 1342262926 302 — 1362
LR Mapping Page 2 1342262927 — 1342270038 1362 — 1433

FF postcards

Each FF result is presented visually in a postcard. The appearence of the postcards depend on the observing mode and the ingredients are described in more details in the Release Note.

FF EXAMPLE USAGE

How to use the FF products and catalogues is illustrated with examples in a Jupyter-lab notebook (link to the html version).

Additional information

In order to make full use of the Feature Finder products the following documents provide detailed background information regarding the SPIRE Fourier-Transform Spectrometer, its observing modes, calibration, pipelines and products:

For further reading of documents related with all aspects of the SPIRE instrument, please consult The SPIRE Legacy Documentation Library.

Acknowledge the SPIRE Spectral Feature Finder Catalogue

Any use of the Spectral Feature Finder products should be acknowledged with Hopwood et al., 2018, HERSCHEL-HSC-TN-2321 and Hopwood et al. (2019), in preparation.


Herschel Science Centre, September 2018