Résumé / Abstract Journal-club_Galaxies

Séminaire/Seminar Galaxies

« Extremely broad Lyman-alpha line emission from the molecular-rich (yet quenched) Stephan’s Quintet »

Pierre Guillard
Institut d'Astrophysique de Paris (Paris, France)

I will report on the discovery of an extremely broad Ly-alpha line (2000 km/s) from the intergalactic medium (IGM) in the Stephan’s Quintet (SQ) galaxy group. SQ hosts a 30 kpc long shocked ridge triggered by a galaxy collision at a relative velocity of 1000 km/s, where large amounts of molecular gas coexist with a hot, X-ray emitting plasma. After an introduction to the background physics of the Ly-alpha transfer and emission, I will compare the Ly-alpha line profiles to other optical, infrared and millimeter lines, and show that Ly-alpha photons escape through scattering in a low-density, dust-free medium. Scattering indicates that the neutral gas of the IGM is clumpy, with a large covering factor. Remarkably, over more than four orders of magnitude in temperature, the powers radiated by X-rays, Ly-alpha, H2, [CII] are comparable within a factor of a few. I will discuss shocks and mixing layers as contributors to the energy dissipation associated with a turbulent cascade. This may be important for the cooling of gas at higher redshifts, where the metal content is lower than in this local system, and a high amplitude of turbulence more common.
jeudi 8 juillet 2021 - 11:30
Institut d'Astrophysique de Paris
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