2017/09/30 by Marzia Rivi, Lance Miller, L. Miller
Computer Science · Engineering · Physics and Astronomy · #Advanced Measurement and Detection Methods #Astronomy #Astrophysics #Galaxy #Optical measurement and interference techniques #Optics #Physics #Radio Astronomy Observations and Technology #Redshift #Shear (geology) #Visibility #Weak gravitational lensing #astro-ph.CO #astro-ph.IM
paper · pdf · doi:10.1093/mnras/sty371
published as MNRAS 2018, 476 (2): 2053-2062 · 11 pages, 8 figures, MNRAS accepted
arxiv created 2018/02/07 · openalex publication_date 2018/02/12 · arxiv updated 2018/04/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
This paper extends the method introduced in Rivi et al. (2016b) to measure galaxy ellipticities in the visibility domain for radio weak lensing surveys. In that paper, we focused on the development and testing of the method for the simple case of individual galaxies located at the phase centre, and proposed to extend it to the realistic case of many sources in the field of view by isolating visibilities of each source with a faceting technique. In this second paper, we present a detailed algorithm for source extraction in the visibility domain and show its effectiveness as a function of the source number density by running simulations of SKA1-MID observations in the band 950–1150 MHz and comparing original and measured values of galaxies’ ellipticities. Shear measurements from a realistic population of 104 galaxies randomly located in a field of view of 1 |deg 2| (i.e. the source density expected for the current radio weak lensing survey proposal with SKA1) are also performed. At SNR ≥ 10, the multiplicative bias is only a factor 1.5 worse than what found when analysing individual sources, and is still comparable to the bias values reported for similar measurement methods at optical wavelengths. The additive bias is unchanged from the case of individual sources, but it is significantly larger than typically found in optical surveys. This bias depends on the shape of the uv coverage and we suggest that a uv-plane weighting scheme to produce a more isotropic shape could reduce and control additive bias.