Multi-wavelength environment of the Galactic globular cluster Terzan 5

TL;DR

This study investigates the multi-wavelength emission features of the globular cluster Terzan 5, revealing extended structures and analyzing their possible origins through radio and X-ray data.

Contribution

The paper provides a multi-wavelength analysis of Terzan 5, identifying extended radio and X-ray features and exploring their potential physical mechanisms, which was not previously detailed.

Findings

Extended radio structures near Terzan 5 suggest non-thermal electron production.

Diffuse X-ray emission is confined within 2.5 arcmin and likely due to inverse Compton scattering.

Radio and X-ray data favor inverse Compton origin over non-thermal Bremsstrahlung.

Abstract

Terzan 5 is a Galactic globular cluster exhibiting prominent X-ray and gamma-ray emission. Following the discovery of extended X- ray emission in this object, we explore here archival data at several wavelengths for other unexpected emission features in the vicinity of this globular cluster. Radio data from the Effelsberg 100 metre telescope show several extended structures near Terzan 5, albeit with large uncertainties in the flux estimates and no reliable radio spectral index. In particular, a radio source extending from the location of Terzan 5 to the north-west could result from long-term non-thermal electron production by the large population of milli-second pulsars in this globular cluster. Another prominent radio structure close to Terzan 5 may be explained by ionised material produced by a field O star. As for the diffuse X-ray emission found in Terzan 5, its extension appears to be limited to within 2.5 arcmin of the globular cluster and the available multi-wavelength data is compatible with an inverse Compton scenario but disfavours a non-thermal Bremsstrahlung origin.