Apertif DR1 - HI spectral cubes
Apertif is a phased-array feed system for the Westerbork Synthesis
Radio Telescope (WSRT), providing forty instantaneous beams over 300
MHz of bandwidth. This first data release includes observations in the
first year of survey operations, from 1 July 2019 through 30 June
2020. The data release includes all raw observational data for a total
of 221 observations of 160 independent target fields, covering
approximately one thousand square degrees of sky. A subset of
processed data products, meeting specified quality assessment criteria
as outlined in Adams et al. (2022), are also released. Images and
cubes are released on a per beam basis, and 3374 beams (of 7640
considered) are included in this data release. The processed data
products are only available for the upper 150 MHz of the band over the
range 1280–1430 MHz. The first 12.5 MHz of data are flagged due to
persistent RFI resulting in a nominal bandwidth of 137.5 MHz and
central frequency of 1361.25 MHz. The data products are not
primary-beam corrected, however the primary-beam images are provided
separately that may be used for mosaicking or for correction of
individual images. This service queries the spectral line cubes from
the first data release of Apertif. Four line cubes are produced over a
set of different frequency ranges as follows. Cube 0: 1292.5–1337.1
MHz, Cube 1: 1333.1–1377.7 MHz, Cube 2: 1373.8–1418.4 MHz, Cube 3:
1414.5–1429.3 MHz. Cube 3 is produced at full spectral resolution of
12.2 kHz while other cubes are produced with a 3-channel averaging at
36.6 kHz resolution. The cubes have a spatial extent of 1.1 deg × 1.1
deg (661 × 661 pixels, with 6''/pixel). The median noise for all line
cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy/beam,
corresponding to a 3-σ H I column density sensitivity of 1.8 × 10^20
atoms cm^−2 over 20 km s^−1 (for a median angular resolution of 24″ ×
15″). The corresponding dirty beam cubes are also released to allow
offline cleaning of source emission.
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