Extremely Broad Ly? Line Emission from the Molecular Intragroup Medium in Stephan’s Quintet: Evidence for a Turbulent Cascade in a Highly Clumpy Multiphase Medium?

We present Hubble Space Telescope Cosmic Origin Spectrograph (COS) UV line spectroscopy and integral-field unit (IFU) observations of the intra-group medium in Stephan's Quintet (SQ). SQ hosts a 30 kpc long shocked ridge triggered by galaxy collision at relative velocity 1000 km/s, where large amounts molecular gas coexist with hot, X-ray emitting, plasma. COS five positions sampling diverse environments reveals very broad (2000 km/s) Ly$\alpha$ emission complex shapes. The profiles are similar to or much broader than those H$\beta$, [CII]$\lambda157.7\mu$m CO~(1-0) emission. extreme breadth emission, compared implies resonance scattering within observed structure. Scattering indicates that neutral is clumpy, significant surface covering factor. observe variations Ly$\alpha$/H$\beta$ flux ratio between components. From mean averaged over velocities, we estimate effective escape fraction photons be 10-30%. Remarkably, more four orders magnitude temperature, powers radiated X-rays, Ly$\alpha$, H$_2$, [CII] comparable factor few, assuming H$_2$ fluxes whole stay positions. Both shocks mixing layers could contribute energy dissipation associated turbulent cascade. Our results may relevant for cooling high redshifts, metal content lower this local system, amplitude turbulence common.