Gravitationally Lensed Galaxies at 2<z<3.5: Direct Abundance Measurements of Lya Emitters

TL;DR

This study uses gravitational lensing to detect and analyze emission lines in galaxies at redshifts 2 to 3.5, enabling direct oxygen abundance measurements and insights into high-redshift Lya emitters' physical properties.

Contribution

It presents the first direct oxygen abundance measurements for galaxies at z>2 using gravitational lensing, doubling the known sample and providing detailed physical insights.

Findings

Oxygen abundances around 10% solar in the studied galaxies.

Sub-solar carbon and nitrogen ratios relative to oxygen.

Small outflows consistent with observed line profiles.

Abstract

Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2<z<3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z>2 for which this has been possible. The three galaxies have ~10% solar oxygen abundances in agreement with strong emission line diagnostics. Carbon and nitrogen ratios relative to oxygen are sub-solar as expected for young metal-poor galaxies. Two of the galaxies are Lya emitters with rest-frame equivalent widths of 20 A and 40 A, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lya emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines.