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Who Paints the Neutrino Sky: Two Hands of the Galaxy ✛

Original: "Galactic Microquasar and Supernova Remnants Imprinting on Diffuse Neutrino and Gamma-Ray Sky"
· Shiqi Yu, Bing Theodore Zhang
arXiv:2608.22374v1 · 2026-08-23 · CC BY 4.0 · 1 min
High Energy
Supernova remnants and microquasars together create the diffuse glow.

The Galaxy shines in neutrinos — particles that barely interact with matter. This light is painted by two hands: supernova remnants (shells left after stellar explosions) and microquasars (binary systems with a black hole and jets). Both accelerate protons, which collide with gas to produce neutrinos. But which hand matters more?

Up to 10 TeV, supernova remnants create the background; above that, microquasars take over.

Scientists built a model where the two classes of accelerators act separately. Supernova remnants accelerate protons up to 68 TeV, while microquasars reach 6 PeV — a hundred times higher. By fitting the efficiency to measurements at Earth, they calculated the neutrino and gamma-ray fluxes. The result matched IceCube and LHAASO data. Now this background can be used to search for individual bright sources.

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The proton acceleration efficiency of about 10% for microquasars means that each such object in its active phase injects energy into cosmic rays comparable to the Eddington luminosity for a black hole of 10 solar masses — approximately $10^{39}$ erg/s.

n_{cr}(E,r,\tau_{lookback}) = L_{cr} \int_{\tau_{min}}^{\tau_{lookback}} P(r,E,\tau)\,d\tau
The particle concentration at point r is built up by diffusion from a source that has been injecting over the injection time.
q_\nu(E_\nu,r) = n_{gas}(r) \int dE_p\, n_p(E_p,r)\,\beta c\,\sigma_{pp}(E_p)\,\frac{dN_\nu}{dE_\nu}(E_\nu,E_p)
The number of neutrinos at point r is proportional to the gas density and the proton flux, multiplied by the cross section and particle yield.
\phi_\nu(E_\nu,\Omega) = \frac{1}{4\pi} \int dE_p\, \beta c\,\sigma_{pp}(E_p)\,\frac{dN_\nu}{dE_\nu}(E_\nu,E_p)\,X(\Omega,E_p)
The observed flux is the sum of contributions from all points along the direction where cosmic rays and gas intersect.
Scientists
Paul DiracBernhard RiemannJoseph WeberKarl SchwarzschildKip ThorneRainer Weiss
Concepts
cosmic neutrino relic neutrino supernova remnant cosmic accelerator neutron star in supernova remnant icecube interstellar gas neutron star bubble galactic dust winds galactic outflow crab nebula large magellanic cloud gamma ray telescope stellar chemical abundances nicer gas cloud lhaaso population iii stars pulsar wind nebula