Conference proceeding
Evidence for inverse-Compton emission from globular clusters
37TH INTERNATIONAL COSMIC RAY CONFERENCE, ICRC2021, 617
01/01/2022
DOI: 10.22323/1.395.0617
Abstract
Millisecond pulsars are very likely the main source of gamma-ray emission from globular clusters. However, the relative contributions of two separate emission processes-curvature radiation from millisecond pulsar magnetospheres vs. inverse Compton emission from relativistic pairs launched into the globular cluster environment by millisecond pulsars-have long been unclear. To address this, we search for evidence of inverse Compton emission in 8-year Fermi-LAT data from the directions of 157 MilkyWay globular clusters. We find that the gamma-ray luminosities of the globular clusters are correlated with their stellar encounter rates (6.4 sigma) and total radiation field energy density (3.8 sigma). We demonstrate that the gamma-ray emission of globular clusters can be resolved spectrally into two components: i) an exponentially cut-off power law and ii) a pure power law. The latter component-which we uncover at a significance of 8.2 sigma-is most naturally interpreted as inverse Compton emission by cosmic-ray electrons and positrons injected by millisecond pulsars. The luminosity of this inverse Compton component suggests that the fraction of millisecond pulsar spin-down luminosity into relativistic leptons is similar to the fraction of the spin-down luminosity into prompt magnetospheric radiation.
Details
- Title: Subtitle
- Evidence for inverse-Compton emission from globular clusters
- Creators
- Deheng Song - Virginia TechOscar Macias - Virginia TechShunsaku Horiuchi - Virginia TechRoland M. Crocker - Australian National UniversityDavid M. Nataf - Johns Hopkins University
- Contributors
- B Keilhauer (Editor)
- Resource Type
- Conference proceeding
- Publication Details
- 37TH INTERNATIONAL COSMIC RAY CONFERENCE, ICRC2021, 617
- DOI
- 10.22323/1.395.0617
- Publisher
- PROCEEDINGS OF SCIENCE
- Number of pages
- 8
- Grant note
- WPI Initiative, MEXT, Japan; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) AST1908960; PHY-1914409 / NSF; National Science Foundation (NSF) DE-SC0020262 / U.S. DOE; United States Department of Energy (DOE) JP17H04836; JP18H04340; JP18H04578; JP20K14463 / JSPS KAKENHI; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Japan Society for the Promotion of Science; Grants-in-Aid for Scientific Research (KAKENHI) DP190101258 / Australian Research Council 80NSSC19K0589 / NASA; National Aeronautics & Space Administration (NASA)
- Language
- English
- Date published
- 01/01/2022
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984701734002771
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