[Paper Review] Exploring the HI Universe with ASKAP

M. Meyer|ArXiv.org|Dec 11, 2009

Galaxies: Formation, Evolution, Phenomena5 references17 citations

TL;DR

This paper proposes the DINGO survey, a deep neutral hydrogen (HI) survey using the Australian SKA Pathfinder (ASKAP) to map HI emission from galaxies out to redshift z ~ 0.4 across 60–150 deg² regions. By targeting GAMA survey fields, DINGO enables multiwavelength context for studying HI mass function, cosmic web evolution, and galaxy formation, achieving high sensitivity and completeness through deep integrations and advanced data processing.

ABSTRACT

The survey speed of ASKAP makes it a prime instrument with which to survey the HI universe, enabling it to carry out both wide surveys of the entire sky, as well as deep surveys covering cosmologically representative volumes. Here, the use of ASKAP to study deep HI fields is discussed as proposed by the Deep Investigation of Neutral Gas Origins (DINGO) survey. This ASKAP science survey project anticipates observing in excess of 10^5 sources out to redshift z~0.4. Key science goals include: Omega_HI and its evolution, the cosmic web as traced by distributions such as the HI mass function and the 2pt correlation function, and the formation and evolution of galaxies. Science returns are maximised by targeting the GAMA survey regions, enabling the HI content of galaxies to be studied and understood in full context with all the major galactic constituents over the past 4 Gyr.

Motivation & Objective

• To measure the evolution of cosmic HI mass density (Ω_HI) with redshift using direct HI emission detection out to z ~ 0.4.
• To study the cosmic web's structure and evolution by measuring the HI mass function and 2-point correlation function over cosmologically representative volumes.
• To understand galaxy evolution by linking HI content to all major galactic components (stars, dust, dark matter) using multiwavelength data from the GAMA survey.
• To develop robust, high-completeness source-finding and RFI mitigation techniques for deep, wide-area HI surveys with ASKAP.
• To coordinate with other SKA pathfinder surveys (e.g., Wallaby, MeerKAT) to create a layered, complementary legacy survey strategy.

Proposed method

• Conducting ultradeep 2500-hour and deep 500-hour ASKAP pointings over 60 deg² and 150 deg² regions, respectively, to achieve high sensitivity to HI emission at z < 0.43.
• Targeting the GAMA survey fields to enable multiwavelength cross-identification and context for HI properties using data from GALEX, VST, VISTA, UKIRT, WISE, and Herschel-ATLAS.
• Employing matched filter and wavelet-based source-finding techniques to enhance detection of point-like HI sources while minimizing false positives.
• Using end-to-end simulation, imaging, and analysis pipelines to test source-finding completeness and reliability, and to validate calibration and dynamic range.
• Implementing RFI mitigation strategies for stacked visibility data, accounting for delayed appearance of RFI in deep integrations.
• Developing semi-empirical and semi-analytic simulations to model HI properties consistent with observed HI mass density, mass function, and clustering.

Experimental results

Research questions

• RQ1 What is the evolution of the cosmic HI mass density (Ω_HI) from z = 0 to z ~ 0.4, and how does it compare to local measurements from HIPASS?
• RQ2 How has the spatial clustering of HI gas evolved over the past 4 Gyr, as traced by the HI mass function and 2-point correlation function?
• RQ3 How do HI properties correlate with galaxy environment, morphology, and stellar content across the GAMA survey fields?
• RQ4 What is the completeness and reliability of automated source-finding algorithms in deep, wide-area HI surveys with complex RFI and noise characteristics?
• RQ5 How can ASKAP’s deep HI survey be optimally coordinated with other SKA pathfinder surveys (e.g., Wallaby, MeerKAT) to maximize legacy science impact?

Key findings

• DINGO is projected to detect over 10⁵ HI sources out to z ~ 0.4, enabling statistically robust measurements of the HI mass function and clustering evolution.
• The survey will achieve Hipass-like precision in measuring Ω_HI out to z ~ 0.4 using direct emission detection, reducing reliance on uncertain stacking techniques.
• By targeting GAMA fields, DINGO will provide the most comprehensive multiwavelength context for HI properties across the past 4 Gyr, linking gas content to stellar, dust, and dark matter components.
• Simulations indicate that DINGO will be sensitive to HI masses down to M_HI ~ 10⁹ M☉ at z ~ 0.2, enabling detection of low-mass, gas-rich galaxies.
• The survey will produce a legacy dataset for SKA planning, with validated data pipelines and RFI mitigation strategies developed through BETA commissioning tests.
• Coordination with MeerKAT and Wallaby will enable a layered survey strategy covering 10–150 deg² (Dingo), 3×10⁴ deg² (Wallaby), and <10 deg² (MeerKAT), ensuring complementary depth and area coverage.