Investigating the Gamma-Ray Emission from Explosive Dispersal Outflows with Fermi-LAT

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Main Authors: Pandey, Paarmita, Lenker II, Stephen C., Lopez, Laura A., Rosen, Anna L., Linden, Tim, Thompson, Todd A., Offner, Stella S. R., Auchettl, Katie, Hirata, Christopher M.
Format: Preprint
Published: 2025
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author Pandey, Paarmita
Lenker II, Stephen C.
Lopez, Laura A.
Rosen, Anna L.
Linden, Tim
Thompson, Todd A.
Offner, Stella S. R.
Auchettl, Katie
Hirata, Christopher M.
author_facet Pandey, Paarmita
Lenker II, Stephen C.
Lopez, Laura A.
Rosen, Anna L.
Linden, Tim
Thompson, Todd A.
Offner, Stella S. R.
Auchettl, Katie
Hirata, Christopher M.
contents We present the first systematic study of explosive dispersal outflows (EDOs) as potential sources of high-energy emission in the Milky Way. EDOs are energetic outflows produced during dynamical interactions in young, massive star-forming regions, and their physical conditions make them promising environments for cosmic-ray acceleration. Using 16 years of $0.2$--$500$ GeV Fermi-LAT observations, we study the gamma-ray properties of seven EDOs. Three EDOs, DR21, G34.26$+$0.15, and G5.89$-$0.39 show spatially coincident GeV emission, while the remaining systems yield non-detections. Among the sample, DR21 stands out as the brightest candidate, with a detection significance $\geq 40σ$. Its spectrum is well described by a power law with an exponential cutoff, and the integrated luminosity in the $0.1$--$500$ GeV band is $L_γ\simeq 2\times10^{35}\ \mathrm{erg\ s^{-1}}$. When compared with the outflow's estimated kinetic energy, the inferred cosmic-ray acceleration efficiency is $\leq 15\%$, consistent with values for shocks in dense molecular environments. The energetics and morphology support an association between the DR21 molecular outflow and the observed gamma rays. Our results demonstrate that EDOs span a wide range of gamma-ray luminosities and efficiencies, suggesting they may contribute to the Galactic cosmic ray budget. This motivates searches for additional EDOs and improved multiwavelength characterization of their environments.
format Preprint
id arxiv_https___arxiv_org_abs_2509_02679
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Investigating the Gamma-Ray Emission from Explosive Dispersal Outflows with Fermi-LAT
Pandey, Paarmita
Lenker II, Stephen C.
Lopez, Laura A.
Rosen, Anna L.
Linden, Tim
Thompson, Todd A.
Offner, Stella S. R.
Auchettl, Katie
Hirata, Christopher M.
High Energy Astrophysical Phenomena
We present the first systematic study of explosive dispersal outflows (EDOs) as potential sources of high-energy emission in the Milky Way. EDOs are energetic outflows produced during dynamical interactions in young, massive star-forming regions, and their physical conditions make them promising environments for cosmic-ray acceleration. Using 16 years of $0.2$--$500$ GeV Fermi-LAT observations, we study the gamma-ray properties of seven EDOs. Three EDOs, DR21, G34.26$+$0.15, and G5.89$-$0.39 show spatially coincident GeV emission, while the remaining systems yield non-detections. Among the sample, DR21 stands out as the brightest candidate, with a detection significance $\geq 40σ$. Its spectrum is well described by a power law with an exponential cutoff, and the integrated luminosity in the $0.1$--$500$ GeV band is $L_γ\simeq 2\times10^{35}\ \mathrm{erg\ s^{-1}}$. When compared with the outflow's estimated kinetic energy, the inferred cosmic-ray acceleration efficiency is $\leq 15\%$, consistent with values for shocks in dense molecular environments. The energetics and morphology support an association between the DR21 molecular outflow and the observed gamma rays. Our results demonstrate that EDOs span a wide range of gamma-ray luminosities and efficiencies, suggesting they may contribute to the Galactic cosmic ray budget. This motivates searches for additional EDOs and improved multiwavelength characterization of their environments.
title Investigating the Gamma-Ray Emission from Explosive Dispersal Outflows with Fermi-LAT
topic High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2509.02679