First release of Apertif imaging survey data
Abstract
(Abridged) Apertif is a phased-array feed system for WSRT, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program started on 1 July 2019, with the last observations taken on 28 February 2022. We describe the release of data products from the first year of survey operations, through 30 June 2020. We focus on defining quality control metrics for the processed data products. The Apertif imaging pipeline, Apercal, automatically produces non-primary beam corrected continuum images, polarization images and cubes, and uncleaned spectral line and dirty beam cubes for each beam of an Apertif imaging observation. For this release, processed data products are considered on a beam-by-beam basis within an observation. We validate the continuum images by using metrics that identify deviations from Gaussian noise in the residual images. If the continuum image passes validation, we release all processed data products for a given beam. We apply further validation to the polarization and line data products. We release all raw observational data from the first year of survey observations, for a total of 221 observations of 160 independent target fields, covering approximately one thousand square degrees of sky. Images and cubes are released on a per beam basis, and 3374 beams are released. The median noise in the continuum images is 41.4 uJy/bm, with a slightly lower median noise of 36.9 uJy/bm in the Stokes V polarization image. The median angular resolution is 11.6"/sin(Dec). The median noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy/bm, corresponding to a 3-sigma HI column density sensitivity of 1.8 x 10^20 atoms cm^-2 over 20 km/s (for a median angular resolution of 24" x 15"). We also provide primary beam images for each individual Apertif compound beam. The data are made accessible using a Virtual Observatory interface.
Cite
@article{arxiv.2208.05348,
title = {First release of Apertif imaging survey data},
author = {Elizabeth A. K. Adams and B. Adebahr and W. J. G. de Blok and H. Denes and K. M. Hess and J. M. van der Hulst and A. Kutkin and D. M. Lucero and R. Morganti and V. A. Moss and T. A. Oosterloo and E. Orru and R. Schulz and A. S. van Amesfoort and A. Berger and O. M. Boersma and M. Bouwhuis and R. van den Brink and W. A. van Cappellen and L. Connor and A. H. W. M. Coolen and S. Damstra and G. N. J. van Diepen and T. J. Dijkema and N. Ebbendorf and Y. G. Grange and R. de Goei and A. W. Gunst and H. A. Holties and B. Hut and M. V. Ivashina and G. I. G. Jozsa and G. M. Loose and J. van Leeuwen and Y. Maan and M. Mancini and A. Mika and H. Mulder and M. J. Norden and A. R. Offringa and L. C. Oostrum and I. Pastor-Marazuela and D. J. Pisano and A. A. Ponomareva and J. W. Romein and M Ruiter and A. P. Schoenmakers and D. van der Schuur and J. J. Sluman and R. Smits and K. J. C Stuurwold and J. Verstappen and N. P. E Vilchez and D. Vohl and K. J. Wierenga and S. J. Wijnholds and E. E. M. Woestenburg and A. W. Zanting and J. Ziemke},
journal= {arXiv preprint arXiv:2208.05348},
year = {2022}
}
Comments
Accepted for publication in A&A, updated Figure 1