CHILES. VII. Deep Imaging for the CHILES Project, an SKA Prototype

Abstract

Radio astronomy is undergoing a renaissance, as the next generation of instruments provides a massive leap forward in collecting area and therefore raw sensitivity. However, to achieve this theoretical level of sensitivity in the science data products, we need to address the much more pernicious systematic effects, which are the true limitation. These become all the more significant when we consider that much of the time used by survey instruments, such as the Square Kilometre Array (SKA), will be dedicated to deep surveys. CHILES is a deep H i survey of the COSMOS field, with 1000 hr of Very Large Array time. We present our approach for creating the image cubes from the first epoch, with discussions of the methods and quantification of the data quality from 946 to 1420 MHz—a redshift range of 0.5−0. We lay out the problems we had to solve and describe how we tackled them. These are important because CHILES is the first deep wide-band multiepoch H i survey and has relevance for ongoing and future surveys. We focus on the accumulated systematic errors in the imaging, as the goal is to deliver a high-fidelity image that is only limited by the random thermal errors. To understand and correct these systematic effects, we ideally manage them in the domain in which they arise, and that is predominately the visibility domain. CHILES is a perfect test bed for many of the issues we can expect for deep imaging with the SKA or ngVLA, and we discuss the lessons we have learned.

SKA Science Data Challenge 2: analysis and results

“…MNRAS 523, 1967-1993 (2023) This work used resources of China SKA Regional Centre prototype (An et al 2019 ;2022 ) funded by the National Key R&D Programme of China (2018YFA0404603) and Chinese Academy of Sciences (114231KYSB20170003). The Enabling Green E-science for the Square Kilometre Array Research Infrastructure (ENGAGE-SKA) team acknowledges financial support from grant POCI-01-0145-FEDER022217, funded by Programa Operacional Competitividade e Internacionaliza c ¸˜ ao (COMPETE 2020) and the Funda c ¸˜ ao para a Ci ˆ encia e a Tecnologia (FCT), Portugal.…”

“…H I dynamics also provide a measurement of the dark matter (DM) content of galaxies (Power et al 2015 ). Deep H I surv e ys are therefore crucial for our understanding of galaxy formation and evolution o v er cosmic time (Power, Baugh & Lacey 2010 ;Blyth et al 2015 ;Meyer et al 2017 ;Dodson et al 2022 ).…”

MIGHTEE-H i: the first MeerKAT H i mass function from an untargeted interferometric survey

“…The advent of the next-generation deep, blind H I surveys using new telescopes such as Australian Square Kilometre Array Pathfinder (ASKAP; Johnston et al 2008 ), APERture Tile In Focus (APERTIF; Adams et al 2022 ), MeerKAT (Jonas 2009 ), and eventually the Square Kilometre Array (SKA) will impro v e our understanding of the redshift evolution of the HIMF and H I . Surv e ys such as the Looking At the Distant Universe with the MeerKAT Array (LADUMA; Blyth et al 2018 ), the Deep Investigation of Neutral Gas Origins (DINGO; Meyer 2010 ;Rhee et al 2023 ), and the COSMOS H I Large Extragalactic Surv e y (CHILES; Hess et al 2019 ;Dodson et al 2022 ) are specifically designed to systematically study H I in galaxies o v er a large range of redshifts. Another such surv e y is the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE; Jarvis et al 2018 ), which when complete will detect more than 1000 galaxies in H I up to z ∼ 0.6, therefore allowing the systematic study of the evolution of the neutral gas content of galaxies o v er the past fiv e billion years.…”