SHOCK-ENHANCED C+ EMISSION AND THE DETECTION OF H2O FROM THE STEPHAN’S

   Prof. Gao, Yu in PMO and his cooperator have performed the first Herschel observations of the giant intergalactic filament away from the major star forming regions in Stephan’s Quintet with the [OI] 63 μm and [C II] 158 μm fine-structure transitions, and a single para-H₂O. The filament is believed to form when a high-speed intruder to the group collided with a clumpy intergroup gas (see figure). 

（By with GAO Yu）

      Based on a model of the heating and cooling of the [C II]- and [O I]-emitting gas, Appleton et al. ‘s measurements suggest that the emission arises from a warm diffuse medium. They found that the strong enhancement of [C II] in the filament, relative to PAH and dust continuum, suggests that the [C II] is heated by shocks and turbulence, but not star formation.  The possibility that [C II] can be excited at a large scale by the dissipation of mechanical energy (turbulence and shocks) provides a potential new source of [C II] emission when interpreting [C II] in high-redshift galaxies. These new results have been published in 2013, The Astrophysical Journal Vol. 777, Page 66.