The First Large Absorption Survey in H i (FLASH): I. Science goals and survey design. (21st March 2022)

• Record Type: Journal Article
• Authors: Allison, James R.; Sadler, E. M.; Amaral, A. D.; An, T.; Curran, S. J.; Darling, J.; Edge, A. C.; Ellison, S. L.; Emig, K. L.; Gaensler, B. M.; Garratt-Smithson, L.; Glowacki, M.; Grasha, K.; Koribalski, B. S.; Lagos, C. del P.; Lah, P.; Mahony, E. K.; Mao, S. A.; Morganti, R.; Moss, V. A.; Pettini, M.; Pimbblet, K. A.; Power, C.; Salas, P.; Staveley-Smith, L.; Whiting, M. T.; Wong, O. I.; Yoon, H.; Zheng, Z.; Zwaan, M. A.
• Is Part Of: Publications of the Astronomical Society of Australia. Volume 39(2022)
• Publication Date: 2022-03-21
• Subjects: galaxies: active -- galaxies: ISM -- methods: observational -- radio continuum: general -- radio lines: galaxies -- surveys; Astronomy -- Periodicals; Southern sky (Astronomy) -- Periodicals; Astrophysics -- Periodicals; Periodicals; 520.5
• DOI: 10.1017/pasa.2022.3
• Languages: English
• ISSNs: 1323-3580

Abstract

Abstract: We describe the scientific goals and survey design of the First Large Absorption Survey in H i (FLASH), a wide field survey for 21-cm line absorption in neutral atomic hydrogen (H i ) at intermediate cosmological redshifts. FLASH will be carried out with the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope and is planned to cover the sky south of $\delta \approx +40\, \deg$ at frequencies between 711.5 and 999.5 MHz. At redshifts between $z = 0.4$ and $1.0$ (look-back times of 4 – 8 Gyr), the H i content of the Universe has been poorly explored due to the difficulty of carrying out radio surveys for faint 21-cm line emission and, at ultra-violet wavelengths, space-borne searches for Damped Lyman- $\alpha$ absorption in quasar spectra. The ASKAP wide field of view and large spectral bandwidth, in combination with a radio-quiet site, will enable a search for absorption lines in the radio spectra of bright continuum sources over 80% of the sky. This survey is expected to detect at least several hundred intervening 21-cm absorbers and will produce an H i -absorption-selected catalogue of galaxies rich in cool, star-forming gas, some of which may be concealed from optical surveys. Likewise, at least several hundred associated 21-cm absorbers are expected to be detected within the host galaxies of radio sources at $0.4 < z < 1.0$, providing valuable kinematical information for models of gas accretion and jet-driven feedback in radio-loud active galactic nuclei. FLASH will also detect OH 18-cm absorbers in diffuse molecular gas, megamaser OH emission, radio recombination lines, and stacked H i emission.