Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons

The inner Galaxy has hosted cosmic-ray burst events, including those responsible for the gamma-ray Fermi bubbles and the eROSITA bubbles in X-rays. In this work, we study the Alpha Magnetic Spectrometer positron fraction and find three features around 12, 21, and 48 GeV, of which the lowest energy h...

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Main Authors: Ilias Cholis, Iason Krommydas
Format: Article
Language:English
Published: IOP Publishing 2023-01-01
Series:The Astrophysical Journal
Subjects:
Online Access:https://doi.org/10.3847/1538-4357/accb55
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author Ilias Cholis
Iason Krommydas
author_facet Ilias Cholis
Iason Krommydas
author_sort Ilias Cholis
collection DOAJ
description The inner Galaxy has hosted cosmic-ray burst events, including those responsible for the gamma-ray Fermi bubbles and the eROSITA bubbles in X-rays. In this work, we study the Alpha Magnetic Spectrometer positron fraction and find three features around 12, 21, and 48 GeV, of which the lowest energy has a 1.4–4.9 σ significance, depending on astrophysical background assumptions. Using background simulations that explain the cosmic-ray positron fraction, positron flux, and electron plus positron flux by primary and secondary cosmic rays and cosmic rays from local pulsars, we test these spectral features as originating from electron/positron burst events from the inner Galaxy. We find the 12 GeV feature to be explained by an event of age τ ≃ 3–10 Myr, in agreement with the proposed age of the Fermi bubbles. Furthermore, the energy in cosmic-ray electrons and positrons propagating along the Galactic disk and not within the Fermi bubbles volume is estimated to be 10 ^51.5 –10 ^57.5 erg, or O(10 ^−4 ) − O(1) the cosmic-ray energy causing the Fermi bubbles. We advocate that these positron fraction features are the counterpart signals of the Fermi bubbles, or of substructures within them, or of the eROSITA bubbles.
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spelling doaj.art-1f223864a4404a47819d61f8e27029fa2023-09-03T11:16:54ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-01950212010.3847/1538-4357/accb55Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray PositronsIlias Cholis0https://orcid.org/0000-0002-3805-6478Iason Krommydas1https://orcid.org/0000-0001-7849-8863Department of Physics, Oakland University , Rochester, MI 48309, USA ; cholis@oakland.eduPhysics Division, National Technical University of Athens , Zografou, Athens, 15780, Greece ; ik23@rice.edu; Department of Physics and Astronomy, Rice University , Houston, TX 77005, USAThe inner Galaxy has hosted cosmic-ray burst events, including those responsible for the gamma-ray Fermi bubbles and the eROSITA bubbles in X-rays. In this work, we study the Alpha Magnetic Spectrometer positron fraction and find three features around 12, 21, and 48 GeV, of which the lowest energy has a 1.4–4.9 σ significance, depending on astrophysical background assumptions. Using background simulations that explain the cosmic-ray positron fraction, positron flux, and electron plus positron flux by primary and secondary cosmic rays and cosmic rays from local pulsars, we test these spectral features as originating from electron/positron burst events from the inner Galaxy. We find the 12 GeV feature to be explained by an event of age τ ≃ 3–10 Myr, in agreement with the proposed age of the Fermi bubbles. Furthermore, the energy in cosmic-ray electrons and positrons propagating along the Galactic disk and not within the Fermi bubbles volume is estimated to be 10 ^51.5 –10 ^57.5 erg, or O(10 ^−4 ) − O(1) the cosmic-ray energy causing the Fermi bubbles. We advocate that these positron fraction features are the counterpart signals of the Fermi bubbles, or of substructures within them, or of the eROSITA bubbles.https://doi.org/10.3847/1538-4357/accb55Galactic cosmic rays
spellingShingle Ilias Cholis
Iason Krommydas
Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
The Astrophysical Journal
Galactic cosmic rays
title Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
title_full Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
title_fullStr Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
title_full_unstemmed Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
title_short Possible Counterpart Signal of the Fermi Bubbles at the Cosmic-Ray Positrons
title_sort possible counterpart signal of the fermi bubbles at the cosmic ray positrons
topic Galactic cosmic rays
url https://doi.org/10.3847/1538-4357/accb55
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