2014MNRAS.438.3039J

We report the discovery of a transparent sightline at projected distances of ρ ≲ 20kpc to an interacting pair of mature galaxies at z = 0.12. The sightline of the UV-bright quasar PG 1522+101 at zem = 1.328 passes at ρ = 11.5kpc from the higher mass galaxy (M* = 10^10.6M_☉) and ρ = 20.4kpc from the lower mass one (M* = 10^10.0M_☉). The two galaxies are separated by 9kpc in projected distance and 30 km/s in line-of-sight velocity. Deep optical images reveal tidal features indicative of close interactions. Despite the small projected distances, the quasar sightline shows little absorption associated with the galaxy pair with a total Hi column density no greater than log  N(H I)/cm^-2=13.65. This limiting Hi column density is already two orders of magnitude less than what is expected from previous halo gas studies. In addition, we detect no heavy-element absorption features associated with the galaxy pair with 3σ limits of log N(Mg II)/cm^-2 < 12.2 and log N(O VI)/cm^-2 < 13.7. The probability of seeing such little absorption in a sightline passing at a small projected distance from two non-interacting galaxies is 0.2 per cent. The absence of strong absorbers near the close galaxy pair suggests that the cool gas reservoirs of the galaxies have been significantly depleted by the galaxy interaction. These observations therefore underscore the potential impact of galaxy interactions on the gaseous haloes around galaxies.