Studies of TeV Gamma-Ray Sources in the Hydrogen-Alpha Optical Line
The first way humanity explored our Milky Way Galaxy and the Universe was through optical light observations. That led us to explore the cosmos using different electromagnetic wavebands such X-rays, gamma-rays, and radio wavelengths. Since then multi-wavelength studies of sources have started to explain their physical properties. The links between the TeV (1012 eV) gamma-ray emission of HESS J1825-137 and an optical supernova remnant (SNR) G18.7-2.2 is helping us to understand the interstellar medium (ISM) in multiple different wavebands (Voisin et al., 2016). G18.7-2.2 is observed in optical H𝛼, and has a spectral intensity ratio of ionised sulphur to H𝛼 [S II] / H𝛼 indicating that it is a SNR. There is a need to look for similar counterparts in H𝛼 towards TeV gamma-ray surveys that have some interesting features. We use the archival data from optical H𝛼 survey, as well as the HESS galactic plane survey (HGPS), looking for attributes that may link the two emission channels. Moreover, other radio and X-ray surveys are used with some HESS candidates to provide more evidence in different electromagnetic wavelengths. A model is used to calculate the SNR radius as a function of age and density, where this age has been inferred from the energetic pulsars which have been left behind in the formation of the SNR. Additionally, a stellar wind bubble (SWB) model is used to estimate the radius of the stellar wind shock produced by the SNR progenitor star. In this work, There are some TeV sources that have no features in the H𝛼. However, there are many notable candidates that have been investigated in this study. We found that HESS J1356-645. HESS J1912+101 and HESS J1804-216 have an arcs in the optical H𝛼 line which indicates a plausible relationship. HESS J1303-631 and HESS J1640-465 have an interesting H𝛼 emission morphology that may be related to the stellar wind bubble created by the progenitor star. Finally, we present the unique H𝛼 jet structure and the bow shock morphology in the region of HESS J1826-148 which may be linked to a powerful microquasar in the galactic plane.
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