Spectra and Polarisation In Cutouts of Extragalactic sources from RACS Second Data Release (SPICE-RACS-DR2)

Full description

Spectra and Polarisation In Cutouts of Extragalactic sources from RACS (SPICE-RACS) is a project to derive an all-Southern-sky, linear polarisation map from the Rapid ASKAP Continuum Survey (RACS). Through this project, we will derive the following products:
• Cutout image cubes in Stokes I, Q, and U around every source detected in total intensity as a function of frequency
• Polarisation spectra as a function of frequency and Faraday depth for every component detected in total intensity
• A catalogue summarising the polarisation properties, including rotation measure (RM), for every component.
• Catalogues that provide the source and component positions in total intensity.

Note that the total intensity catalogues should be treated as a reference for source positions in the images, and approximate source properties. These are not processed to the same quality standard as the forthcoming RACS-low3 catalogue (Galvin et al. in prep).

This collection is laid out as follows:
/
├── catalogues/
│ └── ...
├── cubelets/
│ ├── {FIELD_NAME}_{SBID}_cubelets.tar.gz
│ └── ...
├── skymaps/
│ ├── spice-racs.dr2.{column name}_{interpolation}.fits
│ └── ...
└── spectra/
├── {FIELD_NAME}_{SBID}_spectra.tar.gz
└── ...

Catalogues:
- RACS-low3_INITIAL_components.fits
- RACS-low3_INITIAL_sources.fits
- spice-racs.dr2.fits.gz

Key identifier columns:
The following columns can be used to match across the catalogues, and are also used to structure the data below.
• Scheduling Block: 'sbid' in the spice-racs catalogue, and 'SBID' in the source and component catalogues.
• Field or Tile: 'tile_id' in the spice-racs catalogue, and 'Field_ID' in the source and component catalogues.
• PyBDSF Gaussian component: 'cat_id' in the spice-racs catalogue, and 'Gaussian_ID' component catalogue.
• PyBDSF Source: 'source_id' in the spice-racs catalogue, and 'Source_ID' in the source and component catalogues.

Basic subsets:
From the SPICE-RACS DR2 paper, S4.1:
"Our catalogue contains a row for every source detected in total intensity. We must therefore stress that not every reported row will correspond to a component with a reliable detection of polarised flux. Rather, we have retained all possible values so that users in the community can make their own cuts on the catalogue to satisfy their own needs and balance of completeness vs. correctness.

To assist users of the catalogue, we have again defined some basic subsets that should be reasonable, although conservative, for most science cases. These are as follows:
• goodI: Where the stokesI_fit_flag and channel_flag columns are False.
• goodRM: goodI, and where leakage_flag and snr_flag are False."

Cubelets:
{tile_id}_{sbid}/
├── {source_id stem}
│   ├── {source_id}.SB{sbid}.cutout.{image type}.restored.{Stokes}.{tile_id}.contcube.linmos.{ion type}.fits
│ └── ...
└── ...
• 'image type' can be 'image' or 'weight'
• 'Stokes' can be 'i', 'q', or 'u'
• ion type can be 'ion' or left out of the file name

Spectra:
{tile_id}_{sbid}/
├── {cat_id stem}/
│   ├── {cat_id}.SB{sbid}.{spectra type}.fits
│   └── ...
└── ...
• 'spectra type' can be 'freq', 'fdf', or 'rmsf'

Note that a 'stem' for cat_id or source_id e.g. "XYZ_123" will be "XYZ"

Sky maps:
These are catalogue data interpolated onto sky using either nearest-neighbour (nn) or inverse-distance weighting (idw).
All files are HEALPix images with Nside=512.
All files are named following: spice-racs.dr2.{column name}_{interpolation}.fits
Where 'column name' is the column from the catalogue being interpolated, and interpolation is either 'nn' or 'idw' as above.
Lineage: These data were derived from RACS-low3. We have processed and released 1595 unique SBIDs. The calibrated visibilities are available on CASDA under project code AS110.