LSD: Lyman-break galaxies Stellar populations and Dynamics. I: Mass, metallicity and gas at z~3.1

TL;DR

This study uses spatially-resolved near-infrared spectroscopy to analyze the stellar populations, gas properties, and metallicities of Lyman-Break Galaxies at z~3.1, revealing complex morphologies and evolutionary stages.

Contribution

First spatially-resolved near-infrared spectroscopic analysis of a complete z~3.1 Lyman-Break Galaxy sample, providing new insights into their metallicities, gas fractions, and evolutionary processes.

Findings

Galaxies show complex morphologies with multiple emission peaks.

Metallicities are 10-50% solar, with evolution in the mass-metallicity relation.

Gas fractions are higher in less massive galaxies, indicating active star formation.

Abstract

We present the first results of a project, LSD, aimed at obtaining spatially-resolved, near-infrared spectroscopy of a complete sample of Lyman-Break Galaxies at z~3. Deep observations with adaptive optics resulted in the detection of the main optical lines, such as [OII], Hbeta and [OIII], which are used to study sizes, SFRs, morphologies, gas-phase metallicities, gas fractions and effective yields. Optical, near-IR and Spitzer/IRAC photometry is used to measure stellar mass. We obtain that morphologies are usually complex, with the presence of several peaks of emissions and companions that are not detected in broad-band images. Typical metallicities are 10-50% solar, with a strong evolution of the mass-metallicity relation from lower redshifts. Stellar masses, gas fraction, and evolutionary stages vary significantly among the galaxies, with less massive galaxies showing larger fractions of gas. In contrast with observations in the local universe, effective yields decrease with stellar mass and reach solar values at the low-mass end of the sample. This effect can be reproduced by gas infall with rates of the order of the SFRs. Outflows are present but are not needed to explain the mass-metallicity relation. We conclude that a large fraction of these galaxies are actively creating stars after major episodes of gas infall or merging.