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The Arecibo Legacy Fast ALFA (ALFALFA) survey is a completed, blind extragalactic HI survey exploiting Arecibo's superior sensitivity, angular resolution and digital technology to conduct a census of the local HI universe over a cosmologically significant volume. ALFALFA has detected more than 30,000 extragalactic HI line sources out to z~0.06, and its catalog will be especially useful in synergy with wide area surveys conducted at other wavelengths. The data collection is of great interest to the radio community and NRAO users. NRAO will partner with the ALFALFA team to ingest and serve their valuable products to the community.
ALFALFA has produced over 7400 ~7500 dual polarization spectral data cubes with supporting weights and continuum maps, an ASCII catalog of over 30,000 extragalactic detections, and HI line spectra.
ALFALFA is a completed program. All data products were processed through IDL, but the data are converted to FITS via Python and AstroPy. The ALFALFA project will provide the data cubes in FITS format.
From the SRDP perspective, the set of all ALFALFA data products is a collection.
Publications
The main catalog paper by Haynes et al. (2018).
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Data cube option 2 (Spectral cube and three ancillary products - spectral weights, continuum maps, and continuum weights).
Note that this "option 2" will likely fit best within the current archive scheme.
Number of files: ~7500 x 4 (spectral cubes, spectral weights, continuum maps. continuum weights) = ~30,000 FITS files
Dimensions of the data:
Spectral data cubes and weights: 2 polarizations x 1024 frequency channels x 144 RA pixels x 144 Decl. pixels
Spectral weights: 2 polarizations x 1024 frequency channels x 144 RA pixels x 144 Decl. pixels
Continuum maps: 2 polarizations x 144 RA pixels x 144 Decl. pixels
Continuum maps: Continuum maps and weights: 2 polarizations x 144 RA pixels x 144 Decl. pixels
Volume of data (< 10 TB)
Frequency range: 1335 to 1445 MHz (L-band)
Extragalactic redshift coverage: -2000 < cz < 18,000 km/s
Sky coverage: 7000 square degrees
2. Extragalactic Catalog
The catalog description, an ASCII text file, or a CSV text file. Data volume ~ 5 Megabytes.
Publication: IOP PDF
3. HI Spectra
Each detection has a single FITS file with a binary table extension, containing the X-Y points of the spectrum and associated metadata. Number: ~30,000 FITS files. Total volume: ~ 1 Gigabyte.
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The modalities for discovery and filtering of ALFALFA data sets in the Archive
End user manipulation
Th The expectation is that a user would search for a position on the sky, or via a galaxy name (NED resolver, etc.). For instance, if one searches on the position 12h20m00s, +09d00m00s, four data cubes, each with three additional ancillary products, would be returned (16 totals hits, total volume would be ~ 1.6 GB).
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- Ingest of ALFALFA spectral data cubes and for each cube, three ancillary spectral products (spectral weights, continuum maps, continuum weights)
- Ingest of the ALFALFA extragalactic catalog
- Ingest of the ALFALFA spectral line profiles
- Harvest and persistence of relevant generic and collection specific metadata.
- Ability to filter on Collection in observation view (both: "must be in" and "must not be in" semantics) in Archive Interface
- Ability to search on position, data cube name, or object (Cone Search).
Should haves:
- Search hits should return the data cubes, and any catalog entries and HI spectra within the search parameters.
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- Search on frequency range?
- Search via object name (extragalactic NED resolver)?
- Search via heliocentric redshift?
Implementation Plan
Risk Assessment
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