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Accepted manuscript

ASKAP–EMU radio continuum detection of planetary nebula NGC 5189: the “Infinity” nebula

Published online by Cambridge University Press:  24 June 2025

A. D. Asher*
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia ATNF, CSIRO, Space and Astronomy, PO Box 76, Epping, NSW 1710, Australia
Z. J. Smeaton
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
M. D. Filipović
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
A. M. Hopkins
Affiliation:
School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia
J. Th. van Loon
Affiliation:
Lennard-Jones Laboratories, Keele University, ST5 5BG, UK
T. J. Galvin
Affiliation:
ATNF, CSIRO, Space and Astronomy, PO Box 1130, Bentley, WA 6151, Australia
L. A. Barnes
Affiliation:
Western Sydney University, Locked Bag 1797, Penrith South DC, NSW 2751, Australia
*
Author for correspondence: A. D. Asher, Email: albany.asher@csiro.au.
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Abstract

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We report the radio continuum detection of well known Galactic Planetary Nebula (PN) NGC5189, observed at 943MHz during the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. Two detections of NGC5189 have been made during the survey, of better resolution than previous radio surveys. Both measurements of the integrated flux density are consistent with each other, at S943 MHz = 0.33 ± 0.03 Jy, and the spectral luminosity is L943 MHz = 8.89 × 1013 W m–2 Hz–1. Using available flux density measurements for radio-detections of NGC5189, we calculate a radio surface brightness at 1GHz and measure Σ1 GHz = 6.0 × 10–21 W m–2 Hz–1 sr–1, which is in the expected range for Galactic PNe. We measure an apparent size of 3.′4×2.′2 corresponding to physical diameters of 1.48 pc × 0.96 pc, and combine available radio observations of NGC5189 to estimate a spectral index of α = 0.12 ± 0.05. Hence, we agree with previous findings that NGC5189 is a thermal (free–free) emitting nebula. Additional measurements of the optical depth (τ = 0.00246) and electron density (Ne = 138 cm–3) support our findings that NGC5189 is optically thin at 943 MHz. Furthermore, the radio contours from the ASKAP–EMU image have been overlaid onto a Hubble Space Telescope (HST) Wide Field Camera 3 image, demonstrating that the radio morphology closely traces the optical. Notably, the contour alignment for the innermost region highlights the two envelopes of gas previously reported to be low-ionisation structures, which is considered a defining feature of post common–envelope PNe that surround a central Wolf-Rayet star.

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Type
Research Article
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited.
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia