We report the detection of [CII]λ158µm emission from a system of three closely-separated sources in the COSMOS field at z ∼ 4.56, as part of the ALMA Large Program to INvestigate CII at Early times (ALPINE). The two dominant sources are closely associated, both spatially (1.600 ∼ 11 kpc) and in velocity (∼ 100 km s−1), while the third source is slightly more distant (2.800 ∼ 18kpc, ∼ 300 km s−1). The second strongest source features a slight velocity gradient, while no significant velocity gradient is seen in the other two sources. Using the observed [C II] luminosities, we derive a total log10(SFR[CII] [M year−1]) = 2.8 ± 0.2, which may be split into contributions of 59%, 31%, and 10% from the central, east, and west sources, respectively. Comparison of these [C II] detections to recent zoom-in cosmological simulations suggests an ongoing major merger. We are thus witnessing a system in a major phase of mass build-up by merging, including an on-going major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z ∼ 2.5.
|Publication status||Published - 2019 Aug 21|
- Galaxies: evolution –
- Galaxies: high-redshift
- Galaxies: interaction –
ASJC Scopus subject areas