Analogs of primeval galaxies two billion years after the Big Bang

Abstract

Deep observations are revealing a growing number of young galaxies in the first billion year of cosmic time. Compared to typical galaxies at later times, they show more extreme emission-line properties, higher star formation rates, lower masses, and smaller sizes. However, their faintness precludes studies of their chemical abundances and ionization conditions, strongly limiting our understanding of the physics driving early galaxy build-up and metal enrichment. Here we study a rare population of UV-selected, sub$-L^{\ast }$(z=3) galaxies at redshift 2.4$<z<$3.5 that exhibit all the rest-frame properties expected from primeval galaxies. These low-mass, highly-compact systems are rapidly-forming galaxies able to double their stellar mass in only few tens million years. They are characterized by very blue UV spectra with weak absorption features and bright nebular emission lines, which imply hard radiation fields from young hot massive stars. Their highly-ionized gas phase has strongly sub-solar carbon and oxygen abundances, with metallicities more than a factor of two lower than that found in typical galaxies of similar mass and star formation rate at $z\lesssim$2.5. These young galaxies reveal an early and short stage in the assembly of their galactic structures and their chemical evolution, a vigorous phase which is likely to be dominated by the effects of gas-rich mergers, accretion of metal-poor gas and strong outflows.

25 pages, 8 figs, 2 tables. Accepted for publication

References in corpus (16)

• The 2013 Release of Cloudy
• The VIMOS Ultra-Deep Survey: ~10,000 galaxies with spectroscopic redshifts to study galaxy assembly at early epochs 2<z<~6
• Modelling the nebular emission from primeval to present-day star-forming galaxies
• The galaxy stellar mass function at 3.5<z<7.5 in the CANDELS/UDS, GOODS-South, and HUDF fields
• Stellar masses from the CANDELS survey: the GOODS-South and UDS fields
• Deriving model-based T${}_e$-consistent chemical abundances in ionised gaseous nebulae
• Ultraviolet Emission Lines in Young Low Mass Galaxies at z~2: Physical Properties and Implications for Studies at z>7
• A Local Clue to the Reionization of the Universe
• C, N, O Abundances in the Most Metal-Poor Damped Lyman alpha Systems
• Gravitationally Lensed Galaxies at 2<z<3.5: Direct Abundance Measurements of Lya Emitters
• The VIMOS Ultra-Deep Survey (VUDS): fast increase of the fraction of strong Lyman alpha emitters from z=2 to z=6
• Photoionization Models for the Semi-Forbidden C III] 1909 Emission in Star-Forming Galaxies
• Feedback in low-mass galaxies in the early Universe
• An extremely young massive clump forming by gravitational collapse in a primordial galaxy
• Evidence of very low metallicity and high ionization state in a strongly lensed, star-forming dwarf galaxy at z=3.417
• Extreme emission-line galaxies out to z$\sim$1 in zCOSMOS. I. Sample and characterization of global properties

Cited by in corpus (1)

• The MUSE Hubble Ultra Deep Field Survey: IV. Global properties of C III] emitters