A dusty star-forming galaxy at z=6 revealed by strong gravitational lensing

TL;DR

This paper reports the discovery and spectroscopic confirmation of a dusty star-forming galaxy at redshift 6, gravitationally lensed, with properties similar to local ULIRGs, providing insights into early universe galaxy formation.

Contribution

First spectroscopic identification of a gravitationally lensed dusty star-forming galaxy at z=6, revealing properties comparable to local ULIRGs and extending galaxy evolution understanding.

Findings

Galaxy at z=6.027 confirmed through spectroscopy.

Gravitational lensing magnification factor mu=9.3.

Intrinsic star formation rate of 380 M_sun/yr after lens correction.

Abstract

Since their discovery, submillimetre-selected galaxies (SMGs) have revolutionized the field of galaxy formation and evolution. From the hundreds of square degrees mapped at submillimetre wavelengths, only a handful of sources have been confirmed to lie at z>5 and only two at z>6. All of these SMGs are rare examples of extreme starburst galaxies with star formation rates (SFRs) of >1000 M_sun/yr and therefore are not representative of the general population of dusty star-forming galaxies. Consequently, our understanding of the nature of these sources, at the earliest epochs, is still incomplete. Here we report the spectroscopic identification of a gravitationally amplified (mu = 9.3 +/- 1.0) dusty star-forming galaxy at z=6.027. After correcting for gravitational lensing, we derive an intrinsic less-extreme SFR of 380 +/- 50 M_sun/yr for this source and find that its gas and dust properties are similar to those measured for local Ultra Luminous Infrared Galaxies (ULIRGs), extending the local trends to a poorly explored territory in the early Universe. The star-formation efficiency of this galaxy is similar to those measured in its local analogues, despite a ~12 Gyr difference in cosmic time.