Searching for Synchrotron Emission from the Geminga TeV Halo using the Planck Satellite

TL;DR

This study investigates whether the Geminga pulsar's TeV halo produces detectable synchrotron emission in Planck satellite data, aiming to understand electron propagation and acceleration at lower energies, but finds no conclusive evidence.

Contribution

First attempt to use Planck data to constrain low-energy electron acceleration and diffusion around the Geminga pulsar's TeV halo.

Findings

No conclusive synchrotron emission detected in Planck data.

Predicted flux is below Planck's measurement threshold.

Current measurements cannot tightly constrain diffusion or injection spectra.

Abstract

Pulsars convert a significant fraction of their total spin-down power into very high-energy electrons, leading to the formation of TeV halos. It is not yet known, however, whether these sources also efficiently accelerate electrons at lower energies and, if so, how those particles propagate through the surrounding environment. If pulsars produce $\sim 50-300 \, {\rm GeV}$ electrons, these particles would produce a spatially extended halo of synchrotron emission in the frequency range measured by Planck. Such emission could be used to constrain the low-energy diffusion coefficient in the regions surrounding these pulsars, as well as the spectrum and intensity of the electrons that are accelerated in this energy range. In this study, we attempt to use Planck data to constrain the nature of the Geminga pulsar's TeV halo. We find no conclusive evidence of this emission in Planck's frequency range, however, and calculate that the synchrotron flux from Geminga should be well below the total flux measured by Planck, even for models with favorable diffusion parameters or soft injection spectra. At this time, these measurements are not capable of significantly constraining the values of these parameters.