Positron annihilation in the nuclear outflows of the Milky Way

Fiona H. Panther*, Roland M. Crocker, Yuval Birnboim, Ivo R. Seitenzahl, Ashley J. Ruiter

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Observations of soft gamma rays emanating from the Milky Way from SPI/INTEGRAL reveal the annihilation of ~2 × 1043 positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce a prominent emission line centred at 511 keV, has remained mysterious since their discovery almost 50 yr ago.Aplausible origin for the positrons is in association with the intense star formation ongoing in the Galactic centre. Moreover, there is strong evidence for a nuclear outflow in the MilkyWay.We find that advective transport and subsequent annihilation of positrons in such an outflow cannot simultaneously replicate the observedmorphology of positron annihilation in the Galactic bulge and satisfy the requirement that 90 per cent of positrons annihilate once the outflow has cooled to 104 K.

Original languageAmerican English
Pages (from-to)L17-L21
JournalMonthly Notices of the Royal Astronomical Society: Letters
Issue number1
StatePublished - 1 Feb 2018

Bibliographical note

Publisher Copyright:
© 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.


  • Galaxy: centre
  • Gamma-rays: ISM
  • ISM: general


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