In the framework of the unification scheme of radio-loud active galactic nuclei, BL Lac objects and quasars are the beamed end-on counterparts of low-power (FRI) and high-power (FRII) radio galaxies, respectively. Some BL Lacs have been found to poss
ess the FRII-type large-scale radio morphology, suggesting that the parent population of BL Lacs is a mixture of low- and high-power radio galaxies. This seems to apply only to `low frequency-peaked BL Lacs, since all the `high frequency-peaked BL Lacs studied so far were shown to host exclusively the FRI-type radio jets. While analyzing the NVSS survey maps of the TeV detected BL Lacs, we have however discovered that the high frequency-peaked object SHBL J001355.9-185406 is associated uniquely with the one-sided, arcmin-scale, and edge-brightened jet/lobe-like feature extending to the south-west from the blazar core. In order to investigate in detail the large-scale morphology of SHBL J001355.9-185406, we have performed low-frequency and high-resolution observations of the source at 156, 259 and 629 MHz using the Giant Metrewave Radio Telescope. Our analysis indicates that no diffuse arcmin-scale emission is present around the unresolved blazar core, and that the arcmin-scale structure seen on the NVSS map breaks into three distinct features unrelated to the blazar, but instead associated with background AGN. The upper limits for the extended radio halo around the TeV-emitting BL Lac object SHBL J001355.9-185406 read as < 10% - 1% at $156-629$ MHz. The fact that the integrated radio spectrum of the unresolved blazar core is flat down to 156 MHz indicates that a self-similar character of the jet in the source holds up to relatively large distances from the jet base.
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.
