We report the detection of [C II] λ158 μm emission from a system of three closely separated sources in the Cosmic Evolution Survey (COSMOS) field at z ∼ 4.56, as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program to INvestigate C II at Early times (ALPINE). The two most luminous sources are closely associated, both spatially (1.6 arcsec ∼ 11 kpc) and in velocity (∼100 km s−1), while the third source is slightly more distant (2.8 arcsec ∼ 18 kpc, ∼300 km s−1). The second most luminous 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[C II] [M☉ yr−1]) = 2.8 ± 0.2, which may be split into contributions of 59, 31, and 10 per cent 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 ongoing major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z ∼ 2.5.

The ALPINE-ALMA [C II] survey: A triple merger at z ∼ 4.56

Yan L.;Bardelli S.;Cimatti A.
Membro del Collaboration Group
;
Loiacono F.
Data Curation
;
Pozzi F.
Membro del Collaboration Group
;
Talia M.
Membro del Collaboration Group
;
Vallini L.;Vergani D.;Zamorani G.;Zucca E.
2020

Abstract

We report the detection of [C II] λ158 μm emission from a system of three closely separated sources in the Cosmic Evolution Survey (COSMOS) field at z ∼ 4.56, as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program to INvestigate C II at Early times (ALPINE). The two most luminous sources are closely associated, both spatially (1.6 arcsec ∼ 11 kpc) and in velocity (∼100 km s−1), while the third source is slightly more distant (2.8 arcsec ∼ 18 kpc, ∼300 km s−1). The second most luminous 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[C II] [M☉ yr−1]) = 2.8 ± 0.2, which may be split into contributions of 59, 31, and 10 per cent 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 ongoing major merger and an upcoming minor merger, which is expected to end up in a single massive galaxy by z ∼ 2.5.
2020
Jones G.C.; Bethermin M.; Fudamoto Y.; Ginolfi M.; Capak P.; Cassata P.; Faisst A.; Le Fevre O.; Schaerer D.; Silverman J.D.; Yan L.; Bardelli S.; Boquien M.; Cimatti A.; Dessauges-Zavadsky M.; Giavalisco M.; Gruppioni C.; Ibar E.; Khusanova Y.; Koekemoer A.M.; Lemaux B.C.; Loiacono F.; Maiolino R.; Oesch P.A.; Pozzi F.; Riechers D.; Rodighiero G.; Talia M.; Vallini L.; Vergani D.; Zamorani G.; Zucca E.
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