The z = 7.54 Quasar ULAS J1342+0928 Is Hosted by a Galaxy Merger

Abstract

We present ALMA 0.″28 × 0.″20 (1.4 kpc × 1.0 kpc) resolution observations of the [C  ii ] 158 μ m line and underlying dust continuum in the host galaxy of the most distant quasar currently known, ULAS J1342+0928 at z  = 7.5413. Both the [C  ii ] and continuum are detected and spatially resolved. The [C  ii ] line is ∼1.5 times more extended than the continuum emission, showing an elongated and complex structure of approximately 3.2 kpc × 6.4 kpc. Two separate peaks are clearly seen (≳6 σ each) in three 100 km s −1  width [C  ii ] channel maps. The velocity field of the [C  ii ] gas does not show evidence of a coherent rotation field but rather chaotic motion reminiscent of an ongoing merger.