The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MEGaSaURA) I: The Sample and the Spectra

TL;DR

This paper introduces the MEGaSaURA project, providing high-quality ultraviolet spectra of 15 gravitationally lensed galaxies at redshifts 1.68 to 3.6, enabling detailed studies of galaxy evolution and outflows.

Contribution

It presents a new, high-resolution, high signal-to-noise spectral atlas of distant galaxies, with comprehensive data reduction and analysis, accessible to the community.

Findings

Neutral gas shows expected bulk outflows.

No systemic redshift offset between nebular and stellar lines.

Spectra surpass local universe starburst data in quality.

Abstract

We introduce Project MEGaSaURA: The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas. MEGaSaURA comprises medium-resolution, rest-frame ultraviolet spectroscopy of N=15 bright gravitationally lensed galaxies at redshifts of 1.68$<$z$<$3.6, obtained with the MagE spectrograph on the Magellan telescopes. The spectra cover the observed-frame wavelength range $3200 < \lambda_o < 8280$ \AA ; the average spectral resolving power is R=3300. The median spectrum has a signal-to-noise ratio of $SNR=21$ per resolution element at 5000 \AA . As such, the MEGaSaURA spectra have superior signal-to-noise-ratio and wavelength coverage compared to what COS/HST provides for starburst galaxies in the local universe. This paper describes the sample, the observations, and the data reduction. We compare the measured redshifts for the stars, the ionized gas as traced by nebular lines, and the neutral gas as traced by absorption lines; we find the expected bulk outflow of the neutral gas, and no systemic offset between the redshifts measured from nebular lines and the redshifts measured from the stellar continuum. We provide the MEGaSaURA spectra to the astronomical community through a data release.