Tracing the neutral gas environments of young radio AGN with ASKAP

Abstract

At present neutral atomic hydrogen (HI) gas in galaxies at redshifts above $z\sim 0.3$ (the extent of 21-cm emission surveys in individual galaxies) and below $z\sim 1.7$ (where the Lyman-$\alpha$ line is not observable with ground-based telescopes) has remained largely unexplored. The advent of precursor telescopes to the Square Kilometre Array will allow us to conduct the first systematic radio-selected 21-cm absorption surveys for HI over these redshifts. While HI absorption is a tracer of the reservoir of cold neutral gas in galaxies available for star formation, it can also be used to reveal the extreme kinematics associated with jet-driven neutral outflows in radio-loud active galactic nuclei. Using the six-antenna Boolardy Engineering Test Array of the Australian Square Kilometre Array Pathfinder, we have demonstrated that in a single frequency tuning we can detect HI absorption over a broad range of redshifts between $z=0.4$ and $1.0$. As part of our early science and commissioning program, we are now carrying out a search for absorption towards a sample of the brightest GPS and CSS sources in the southern sky. These intrinsically compact sources present us with an opportunity to study the circumunuclear region of recently re-started radio galaxies, in some cases showing direct evidence of mechanical feedback through jet-driven outflows. With the sensitivity of the full ASKAP array we will be able to study the kinematics of atomic gas in a few thousand radio galaxies, testing models of radio jet feedback well beyond the nearby Universe

5 pages, 3 figures. Accepted for publication in Astronomische Nachrichten. In proceedings of the "5th Workshop on CSS and GPS radio sources", held in Rimini (Italy) in May 2015

References in corpus (10)

• Evidence for powerful AGN winds at high redshift: Dynamics of galactic outflows in radio galaxies during the "Quasar Era"
• Fast outflows in compact radio sources: evidence for AGN-induced feedback in the early stages of radio source evolution
• Jet acceleration of the fast molecular outflows in the Seyfert galaxy IC5063
• Probing radio source environments via HI and OH absorption
• The Australian Square Kilometre Array Pathfinder: System Architecture and Specifications of the Boolardy Engineering Test Array
• The HI absorption "Zoo"
• Discovery of HI gas in a young radio galaxy at $z=0.44$ using the Australian Square Kilometre Array Pathfinder
• What triggers a radio AGN? The intriguing case of PKSB 1718-649
• Probing the gas content of radio galaxies through HI absorption stacking
• HI Absorption in High-Frequency Peaker Galaxies

Cited by in corpus (9)

• Compact steep-spectrum and peaked-spectrum radio sources
• FLASH Early Science -- Discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field
• A comparative study of intervening and associated HI 21-cm absorption profiles in redshifted galaxies
• The evolution of neutral hydrogen over the past 11 Gyr via HI 21 cm absorption
• Atomic and Molecular Absorption in Redshifted Radio Sources
• FLASH Pilot Survey: Detections of associated 21 cm HI absorption in GAMA galaxies at 0.42 < z <1.00
• Intervening or associated? Machine learning classification of redshifted H I 21-cm absorption
• The potential of tracing the star formation history with HI 21-cm in intervening absorption systems
• QSO redshift estimates from optical, near-infrared and ultraviolet colours