Abstract
ABSTRACT The Square Kilometre Array (SKA) will be the first low-frequency instrument with the capability to directly image the structures of the epoch of reionization (EoR). Indeed, deep imaging of the EoR over five targeted fields of 20 sq deg each has been selected as the highest priority science objective for SKA1. Aiming at preparing for this highly challenging observation, we perform an extensive pre-selection of the ‘quietest’ and ‘cleanest’ candidate fields in the southern sky to be suited for deep imaging of the EoR using existing catalogues and observations over a broad frequency range. The candidate fields should meet a number of strict criteria to avoid contaminations from foreground structures and sources. The candidate fields should also exhibit both the lowest average surface brightness and smallest variance to ensure uniformity and high-quality deep imaging over the fields. Our selection eventually yields a sample of 7 ‘ideal’ fields of 20 sq deg in the southern sky that could be targeted for deep imaging of the EoR. Finally, these selected fields are convolved with the synthesized beam of SKA1-low stations to ensure that the effect of sidelobes from the far-field bright sources is also weak.
Highlights
Exploration of the dark ages, cosmic dawn (CD) and epoch of reionization (EoR) constitutes the last frontier of observational cosmology for the decades, which will unveil the mysteries of how and when the universe underwent a transition from a dark to bright phase, how the underlying large-scale structures grew from linear to nonlinear stage, and how baryonic matter became prominent for formation of cosmic structures
We summarize the criteria for selecting the candidate fields for deep imaging of EoR with the future SKA1-low: (1) located within the cold regions with temperature below 30 K in the Haslam 408 MHz All-Sky Map; (2) far away from the LMC, SMC and other bright, extended structures; (3) containing no bright radio point sources; (4) containing no massive clusters of galaxies; MHz
Our priority choice of FoV is 20 square degrees or 2◦.52 in radius, the size that will be adopted for the deep imaging of EoR with SKA1-low in terms of current observational strategy, we provide the candidates for a larger field of 40 square degrees or 3.57◦ in radius for both comparison and optional choices
Summary
Exploration of the dark ages, cosmic dawn (CD) and epoch of reionization (EoR) constitutes the last frontier of observational cosmology for the decades, which will unveil the mysteries of how and when the universe underwent a transition from a dark to bright phase, how the underlying large-scale structures grew from linear to nonlinear stage, and how baryonic matter became prominent for formation of cosmic structures. Jansky VLA and FAST (if the fields are observable in the northern hemisphere) over a wide waveband should be made in order to understand the ‘quietness’ and ‘cleanness’ of the candidate fields and their environmental effects This will help to answer the questions of how foreground bright cosmic sources, especially the extended and diffuse ones, are distributed and clustered in the fields, to what extent the sky models can be constructed and foreground sources removed, how sidelobe leakages of off-field bright sources affect the imaging quality and sensitivity, and what kinds of noise remain to be the major source of errors in imaging reconstruction and what kinds of technologies should be needed and further developed to beat down the noise(s) to an acceptable level. With such motivation in mind, we attempt to fulfill the task in the present work by making a pre-selection of the candidate EoR fields, based mainly on the existing radio catalogs and observations
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