Evolutionary map of the Universe (EMU): 18-cm OH-maser discovery in ASKAP continuum images of the SCORPIO field

A. Ingallinera*, F. Cavallaro, S. Loru, J. Marvil, G. Umana, C. Trigilio, S. Breen, C. Bordiu, C. S. Buemi, F. Bufano, J. D. Collier, S. Etoka, M. D. Filipović, S. R. Goldman, A. M. Hopkins, B. S. Koribalski, P. Leto, R. P. Norris, S. Riggi, F. SchilliròC. Tremblay, J. T. Van Loon

*Corresponding author for this work

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3 Citations (Scopus)
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Low-and intermediate-mass stars end their life dispersing their outer layers into the circumstellar medium, during the asymptotic and post-asymptotic giant branch phases. OH masers at 18 cm offer an effective way to probe their circumstellar environment. In this work, we present the discovery of seven OH maser sources likely associated with such evolved stars from the visual inspection of Australian SKA Pathfinder (ASKAP) continuum images. These seven sources do not emit real continuum emission, but the high sensitivity of our images allows us to detect their maser emission, resembling continuum sources. To confirm their nature, we carried out spectral-line observations with ATCA. All the sources showed the double-peaked spectra at 1612 MHz, typical of evolved stars. The detection of maser emission in continuum images can be a complementary and easy-to-use method to discover new maser sources with the large-area deep surveys conducted with the Square Kilometre Array (SKA) precursors. The implication for radio stars studies are remarkable since pure OH maser sources (i.e. with no continuum associated) represent, at a sensitivity of 100 μJy-1, about 4 per cent of all Galactic sources and by far the most numerous stellar population.

Original languageEnglish
Pages (from-to)L21-L26
Number of pages6
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
Publication statusPublished - 1 May 2022

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters, Volume 512, Issue 1, May 2022, Pages L21–L26, https://doi.org/10.1093/mnrasl/slac017. Copyright 2021 The Author(s). Copyright © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.


  • Circumstellar matter
  • Masers
  • Methods: observational
  • Radio lines: stars
  • Stars: AGB and post-AGB
  • Techniques: image processing


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