title: A large population of galaxies 9 to 12 billion years back in the history of the Universe.
abstract: To understand the evolution of galaxies, we need to know as accurately as possible how many galaxies were present in the Universe at different epochs. Galaxies in the young Universe have hitherto mainly been identified using their expected optical colours, but this leaves open the possibility that a significant population remains undetected because their colours are the result of a complex mix of stars, gas, dust or active galactic nuclei. Here we report the results of a flux-limited I-band survey of galaxies at look-back times of 9 to 12 billion years. We find 970 galaxies with spectroscopic redshifts between 1.4 and 5. This population is 1.6 to 6.2 times larger than previous estimates, with the difference increasing towards brighter magnitudes. Strong ultraviolet continua (in the rest frame of the galaxies) indicate vigorous star formation rates of more than 10-100 solar masses per year. As a consequence, the cosmic star formation rate representing the volume-averaged production of stars is higher than previously measured at redshifts of 3 to 4.
authors.affiliation: Laboratoire d'Astrophysique de Marseille, OAMP, UMR6110, CNRS, Université de Provence Aix-Marseille I, BP8, F-13376 Marseille cedex 12, France. Olivier.LeFevre@oamp.fr
authors.forename: O
authors.initials: O
authors.lastname: Le Fèvre
authors.forename: S
authors.initials: S
authors.lastname: Paltani
authors.forename: S
authors.initials: S
authors.lastname: Arnouts
authors.forename: S
authors.initials: S
authors.lastname: Charlot
authors.forename: S
authors.initials: S
authors.lastname: Foucaud
authors.forename: O
authors.initials: O
authors.lastname: Ilbert
authors.forename: H J
authors.initials: HJ
authors.lastname: McCracken
authors.forename: G
authors.initials: G
authors.lastname: Zamorani
authors.forename: D
authors.initials: D
authors.lastname: Bottini
authors.forename: B
authors.initials: B
authors.lastname: Garilli
authors.forename: V
authors.initials: V
authors.lastname: Le Brun
authors.forename: D
authors.initials: D
authors.lastname: Maccagni
authors.forename: J P
authors.initials: JP
authors.lastname: Picat
authors.forename: R
authors.initials: R
authors.lastname: Scaramella
authors.forename: M
authors.initials: M
authors.lastname: Scodeggio
authors.forename: L
authors.initials: L
authors.lastname: Tresse
authors.forename: G
authors.initials: G
authors.lastname: Vettolani
authors.forename: A
authors.initials: A
authors.lastname: Zanichelli
authors.forename: C
authors.initials: C
authors.lastname: Adami
authors.forename: S
authors.initials: S
authors.lastname: Bardelli
authors.forename: M
authors.initials: M
authors.lastname: Bolzonella
authors.forename: A
authors.initials: A
authors.lastname: Cappi
authors.forename: P
authors.initials: P
authors.lastname: Ciliegi
authors.forename: T
authors.initials: T
authors.lastname: Contini
authors.forename: P
authors.initials: P
authors.lastname: Franzetti
authors.forename: I
authors.initials: I
authors.lastname: Gavignaud
authors.forename: L
authors.initials: L
authors.lastname: Guzzo
authors.forename: A
authors.initials: A
authors.lastname: Iovino
authors.forename: B
authors.initials: B
authors.lastname: Marano
authors.forename: C
authors.initials: C
authors.lastname: Marinoni
authors.forename: A
authors.initials: A
authors.lastname: Mazure
authors.forename: B
authors.initials: B
authors.lastname: Meneux
authors.forename: R
authors.initials: R
authors.lastname: Merighi
authors.forename: R
authors.initials: R
authors.lastname: Pellò
authors.forename: A
authors.initials: A
authors.lastname: Pollo
authors.forename: L
authors.initials: L
authors.lastname: Pozzetti
authors.forename: M
authors.initials: M
authors.lastname: Radovich
authors.forename: E
authors.initials: E
authors.lastname: Zucca
authors.forename: M
authors.initials: M
authors.lastname: Arnaboldi
authors.forename: M
authors.initials: M
authors.lastname: Bondi
authors.forename: A
authors.initials: A
authors.lastname: Bongiorno
authors.forename: G
authors.initials: G
authors.lastname: Busarello
authors.forename: L
authors.initials: L
authors.lastname: Gregorini
authors.forename: F
authors.initials: F
authors.lastname: Lamareille
authors.forename: G
authors.initials: G
authors.lastname: Mathez
authors.forename: Y
authors.initials: Y
authors.lastname: Mellier
authors.forename: P
authors.initials: P
authors.lastname: Merluzzi
authors.forename: V
authors.initials: V
authors.lastname: Ripepi
authors.forename: D
authors.initials: D
authors.lastname: Rizzo