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

Abstract

We present ALMA 0.'' 128 x 0.'' 20 (1.4 kpc x 1.0 kpc) resolution observations of the [C II] 158 mu 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 similar to 1.5 times more extended than the continuum emission, showing an elongated and complex structure of approximately 3.2 kpc x 6.4 kpc. Two separate peaks are clearly seen (greater than or similar to 6 sigma 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.