HI Science with the Square Kilometre Array

Abstract

The Square Kilometre Array (SKA) will be a formidable instrument for the detailed study of neutral hydrogen (H I) in external galaxies and in our own Galaxy and Local Group. The sensitivity of the SKA, its wide receiver bands, and the relative freedom from radio frequency interference at the SKA sites will allow the imaging of substantial number of high-redshift galaxies in H I for the first time. It will also allow imaging of galaxies throughout the Local Volume at resolutions of < 100 pc and detailed investigations of galaxy disks and the transition between disks, halos and the intergalactic medium (IGM) in the Milky Way and external galaxies. Together with deep optical and millimetre/sub-mm imaging, this will have a profound effect on our understanding of the formation, growth and subsequent evolution of galaxies in different environments. This paper provides an introductory text to a series of nine science papers describing the impact of the SKA in the field of H I and galaxy evolution. We propose a nested set of surveys with phase 1 of the SKA which will help tackle much of the exciting science described. Longer commensal surveys are discussed, including an ultra-deep survey which should permit the detection of galaxies at z = 2, when the Universe was a quarter of its current age. The full SKA will allow more detailed imaging of even more distant galaxies, and allow cosmological and evolutionary parameters to be measured with exquisite precision.Advancing Astrophysics with the Square Kilometre Array

Tracing Hi Beyond the Local Universe

“…Neutral atomic hydrogen (H I) is one of the most important tracers for studying the assembly of mass, angular momentum, and structure in the Universe (Staveley-Smith & Oosterloo 2015;Blyth et al 2015;Kim et al 2015Kim et al , 2017Obreschkow et al 2016). However, the difficulty of observing emission from this material has meant that most studies have been restricted to the local Universe, with only a small fraction of detections occurring beyond redshift z ∼0.1 (Jaffé et al 2013;Giovanelli & Haynes 2016).…”

THE SEARCH FOR Hi EMISSION AT z ≈ 0.4 IN GRAVITATIONALLY LENSED GALAXIES WITH THE GREEN BANK TELESCOPE

“…Telescopes designed specifically to carry out intensity mapping surveys, like the Canadian Hydrogen Intensity Mapping Experiment (Battye et al 2013), Baryon Acoustic Oscillations in Neutral Gas Observations (Bandura et al 2014), and Tianlai (Chen 2015) will greatly improve measurements of Ω HI . Planned deep field surveys with telescopes such as ASKAP, MeerKAT, and the Square Kilometer Array (Meyer 2009;Holwerda et al 2012;Staveley-Smith & Oosterloo 2015) will have the sensitivity and frequency coverage required to directly detect HI emission in individual galaxies beyond z = 0.45.…”

Gravitationally Lensed H I with MeerKAT

“…This objective has evolved into a rich science case for H I, covering many key aspects of galaxy evolution physics and cosmology from the detection of the epoch of reionization ( [32]), to Baryonic Acoustic Oscillations (BAO) studies ( [30]), and potential direct expansion measurements ( [15]). Current specifications of SKA1-MID Band 1 would only enable detections above z > 0.8 for M HI 10 10 M H I galaxies in the deep, 1 deg 2 survey outlined by [33] and SKA Science Book chapters referred to in their overview. They describe three fiducial SKA1-MID H I surveys that cover extragalactic fields: the medium wide, medium deep and deep surveys which cover areas of Ω = 400, 20, 1 deg 2 respectively, the first two of which are limited to Band 2 and its corresponding H I redshift limit of z < 0.5.…”

“…They describe three fiducial SKA1-MID H I surveys that cover extragalactic fields: the medium wide, medium deep and deep surveys which cover areas of Ω = 400, 20, 1 deg 2 respectively, the first two of which are limited to Band 2 and its corresponding H I redshift limit of z < 0.5. In addition to this, there may be a 10,000 hour SKA1-MID survey, with a commensal H I cosmology and galaxy evolution design, however, the survey design is yet to be determined (see [33]). …”