The Emission Line Properties of Gravitationally-lensed 1.5 < z < 5 Galaxies

TL;DR

This study uses near-infrared spectroscopy of 28 gravitationally-lensed galaxies at 1.5 < z < 5 to analyze their star formation, metallicity, and mass, revealing less evolution in the mass-metallicity relation than previously observed.

Contribution

It provides new insights into the metallicity evolution of low luminosity galaxies at high redshift using gravitational lensing, extending previous studies to lower mass systems.

Findings

Less evolution in the mass-metallicity relation at low masses.

Low luminosity galaxies are more metal-rich than expected for their redshift.

Objects are consistent with a fundamental metallicity relation.

Abstract

We present and analyse near-infrared spectroscopy for a sample of 28 gravitationally- lensed star-forming galaxies in the redshift range 1.5 < z < 5, observed mostly with the Keck II telescope. With typical magnifications of ~1.5-4 magnitudes, our survey provides a valuable census of star formation rates, gas-phase metallicities and dynamical masses for a representative sample of low luminosity galaxies seen at a formative period in cosmic history. We find less evolution in the mass-metallicity relation compared to earlier work that focused on more luminous systems with z - 2-3, especially in the low mass (- 10^9 Msol) where our sample is - 0.25 dex more metal-rich. We interpret this offset as a result of the lower star formation rates (typically a factor of -10 lower) for a given stellar mass in our sub-luminous systems. Taking this effect into account, we conclude our objects are consistent with a fundamental metallicity relation recently proposed from unlensed observations.