ASKAP Commissioning Observations of the GAMA 23 Field

Abstract

We have observed the G23 field of the Galaxy And Mass Assembly (GAMA) survey using the Australian Square Kilometre Array Pathfinder (ASKAP) in its commissioning phase, to validate the performance of the telescope and to characterize the detected galaxy populations. This observation covers $\sim$48 deg${}^2$ with synthesized beam of 32.7${}^{\prime \prime }$ by 17.8${}^{\prime \prime }$ at 936 MHz, and $\sim$39 deg${}^2$ with synthesized beam of 15.8${}^{\prime \prime }$ by 12.0${}^{\prime \prime }$ at 1320 MHz. At both frequencies, the r.m.s. (root-mean-square) noise is $\sim$0.1 mJy/beam. We combine these radio observations with the GAMA galaxy data, which includes spectroscopy of galaxies that are i-band selected with a magnitude limit of 19.2. Wide-field Infrared Survey Explorer (WISE) infrared (IR) photometry is used to determine which galaxies host an active galactic nucleus (AGN). In properties including source counts, mass distributions, and IR vs. radio luminosity relation, the ASKAP detected radio sources behave as expected. Radio galaxies have higher stellar mass and luminosity in IR, optical and UV than other galaxies. We apply optical and IR AGN diagnostics and find that they disagree for $\sim$30% of the galaxies in our sample. We suggest possible causes for the disagreement. Some cases can be explained by optical extinction of the AGN, but for more than half of the cases we do not find a clear explanation. Radio sources are more likely ($\sim$6%) to have an AGN than radio quiet galaxies ($\sim$1%), but the majority of AGN are not detected in radio at this sensitivity.

arXiv comment26 pages, 22 figures, 6 tables. Accepted for publication in Publications of the Astronomical Society of Australia

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Cited by in corpus (8)

• Galaxy And Mass Assembly (GAMA): Assimilation of KiDS into the GAMA database
• FLASH Early Science -- Discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field
• The ASKAP-EMU Early Science Project: 888 MHz Radio Continuum Survey of the Large Magellanic Cloud
• Deep Investigation of Neutral Gas Origins (DINGO): HI stacking experiments with early science data
• Galaxy and Mass Assembly (GAMA): A $\text{WISE}$ study of the activity of emission-line systems in G23
• Connecting MeerKAT radio continuum properties to GAMA optical emission-line and WISE mid-infrared activity
• History of Astronomy in Australia: Big-Impact Astronomy from World War II until the Lunar Landing (1945-1969)
• Deep ASKAP EMU Survey of the GAMA23 field: Properties of radio sources