title: A massive galaxy in its core formation phase three billion years after the Big Bang.
abstract: Most massive galaxies are thought to have formed their dense stellar cores in early cosmic epochs. Previous studies have found galaxies with high gas velocity dispersions or small apparent sizes, but so far no objects have been identified with both the stellar structure and the gas dynamics of a forming core. Here we report a candidate core in the process of formation 11 billion years ago, at redshift z = 2.3. This galaxy, GOODS-N-774, has a stellar mass of 100 billion solar masses, a half-light radius of 1.0 kiloparsecs and a star formation rate of solar masses per year. The star-forming gas has a velocity dispersion of 317 ± 30 kilometres per second. This is similar to the stellar velocity dispersions of the putative descendants of GOODS-N-774, which are compact quiescent galaxies at z ≈ 2 (refs 8-11) and giant elliptical galaxies in the nearby Universe. Galaxies such as GOODS-N-774 seem to be rare; however, from the star formation rate and size of this galaxy we infer that many star-forming cores may be heavily obscured, and could be missed in optical and near-infrared surveys.
authors.affiliation: Astronomy Department, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Erica
authors.initials: E
authors.lastname: Nelson
authors.affiliation: Astronomy Department, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Pieter
authors.initials: P
authors.lastname: van Dokkum
authors.affiliation: Leiden Observatory, Leiden University, NL-2300 RA Leiden, The Netherlands.
authors.forename: Marijn
authors.initials: M
authors.lastname: Franx
authors.affiliation: Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, Maryland 21218, USA.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Brammer
authors.affiliation: Astronomy Department, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Ivelina
authors.initials: I
authors.lastname: Momcheva
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbackstrasse 1, 85748 Garching, Germany.
authors.forename: Natascha Förster
authors.initials: NF
authors.lastname: Schreiber
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Elisabete
authors.initials: E
authors.lastname: da Cunha
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbackstrasse 1, 85748 Garching, Germany.
authors.forename: Linda
authors.initials: L
authors.lastname: Tacconi
authors.affiliation: Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, Arizona 85721, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Bezanson
authors.affiliation: Department of Astronomy, University of Massachusetts, Amherst, Massachusetts 01002, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Kirkpatrick
authors.affiliation: Astronomy Department, Yale University, New Haven, Connecticut 06511, USA.
authors.forename: Joel
authors.initials: J
authors.lastname: Leja
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Hans-Walter
authors.initials: HW
authors.lastname: Rix
authors.affiliation: South African Astronomical Observatory, PO Box 9, Observatory, Cape Town 7935, South Africa.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Skelton
authors.affiliation: Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany.
authors.forename: Arjen
authors.initials: A
authors.lastname: van der Wel
authors.affiliation: Astrophysics Science Division, Goddard Space Center, Greenbelt, Maryland 20771, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Whitaker
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbackstrasse 1, 85748 Garching, Germany.
authors.forename: Stijn
authors.initials: S
authors.lastname: Wuyts