ASKAP-EMU radio continuum detection of planetary nebula NGC 5189: the "Infinity" nebula

Abstract

We report the radio continuum detection of well known Galactic Planetary Nebula (PN) NGC 5189, observed at 943 MHz during the Australian Square Kilometre Array Pathfinder (ASKAP) Evolutionary Map of the Universe (EMU) survey. Two detections of NGC 5189 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 $S_{943\mathrm{MHz}}=0.33\pm 0.03$ Jy, and the spectral luminosity is $L_{943\mathrm{MHz}}$ = 8.89 $\times$ 10${}^{13}$ W m${}^{-2}$ Hz${}^{-1}$. Using available flux density measurements for radio-detections of NGC 5189, we calculate a radio surface brightness at 1 GHz and measure ${\Sigma }_{1\mathrm{GHz}}$ = 6.0 $\times$ 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${}^{\prime }$ $\times$ 2.2${}^{\prime }$ corresponding to physical diameters of 1.48 pc $\times$ 0.96 pc, and combine available radio observations of NGC 5189 to estimate a spectral index of $\alpha$ = 0.12 $\pm$ 0.05. Hence, we agree with previous findings that NGC 5189 is a thermal (free-free) emitting nebula. Additional measurements of the optical depth ($\tau =0.00246$) and electron density ($N_e=138c{m}^{-3}$) support our findings that NGC 5189 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.

arXiv comment9 pages, 4 figures. Accepted for publication in PASA

References in corpus (19)

• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. II. The Source Catalogue
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. I. Science goals, survey design and instrumentation
• Planetary nebulae seen with TESS: Discovery of new binary central star candidates from Cycle 1
• Binary planetary nebulae nuclei towards the Galactic bulge. II. A penchant for bipolarity and low-ionisation structures
• H-alpha emission in local galaxies: star formation, time variability and the diffuse ionized gas
• A radial velocity survey for post-common-envelope Wolf-Rayet central stars of planetary nebulae: First results and discovery of the close binary nucleus of NGC 5189
• One star, two star, red star, blue star: an updated planetary nebula central star distance catalogue from Gaia EDR3
• The mysterious cut-off of the Planetary Nebula Luminosity Function
• A synchrotron jet from a post-AGB star
• Planetary nebulae that cannot be explained by binary systems
• Radio Planetary Nebulae in the Magellanic Clouds
• Time-variable non-thermal emission in the planetary nebula IRAS 15103-5754
• Radio variability and non-thermal components in stars evolving toward planetary nebulae
• Mapping Excitation in the Inner Regions of the Planetary Nebula NGC 5189 using HST WFC3 Imaging
• Gamma-ray detection of newly discovered Ancora SNR: G288.8-6.3
• Radio observations of planetary nebulae: no evidence for strong radial density gradients
• Determination of Planetary Nebulae angular diameters from radio continuum Spectral Energy Distribution modeling
• Low-ionization structures in planetary nebulae -- III. The statistical analysis of physico-chemical parameters and excitation mechanisms
• Non-thermal radio emission in Sakurai's Object

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