Resolving the HI in Damped Lyman-{\alpha} systems that power star-formation

TL;DR

This study uses integral-field spectroscopy to map the extent and properties of damped Lyman-alpha systems at high redshift, revealing their large size, variable hydrogen column densities, and potential to fuel star formation in early galaxies.

Contribution

First direct spatially-resolved measurements of damped Lyman-alpha systems, showing their large extent and detailed hydrogen distribution at high redshift.

Findings

Damped Lyman-alpha systems are over 238 kpc^2 in size.

Hydrogen column densities vary significantly over small scales.

These systems contain enough neutral gas to support future star formation.

Abstract

Reservoirs of dense atomic gas (primarily hydrogen), contain approximately 90 percent of the neutral gas at a redshift of 3, and contribute to 2-3 percent of the total baryons in the Universe. These damped Lyman-${\alpha}$ systems (so called because they absorb Lyman-${\alpha}$ photons from within and from background sources) have been studied for decades, but only through absorption lines present in the spectra of background quasars and gamma-ray bursts. Such pencil beams do not constrain the physical extent of the systems. Here, we report integral-field spectroscopy of a bright, gravitationally lensed galaxy at a redshift of 2.7 with two foreground damped Lyman-${\alpha}$ systems. These systems are $>$ 238 $kpc^2$ in extent, with column densities of neutral hydrogen varying by more than an order of magnitude on $<$ 3 kpc-scales. The mean column densities are $10^{20.46}$ - $10^{20.84} cm^{-2}$ and the total masses are $> 5.5 \times 10^{8}$ - $1.4 \times 10^{9} M_{\odot}$, showing that they contain the necessary fuel for the next generation of star formation, consistent with relatively massive, low-luminosity primeval galaxies at redshifts $>$ 2.