Nearly all the sky is covered by Lyman-α emission around high-redshift galaxies

Wisotzki, L.; Bacon, R.; Brinchmann, J.; Cantalupo, S.; Richter, P.; Schaye, J.; Schmidt, K. B.; Urrutia, T.; Weilbacher, P. M.; Akhlaghi, M. et al.
Bibliographical reference

Nature, Volume 562, Issue 7726, p.229-232

Advertised on:
10
2018
Journal
Description
Galaxies are surrounded by large reservoirs of gas, mostly hydrogen, that are fed by inflows from the intergalactic medium and by outflows from galactic winds. Absorption-line measurements along the lines of sight to bright and rare background quasars indicate that this circumgalactic medium extends far beyond the starlight seen in galaxies, but very little is known about its spatial distribution. The Lyman-α transition of atomic hydrogen at a wavelength of 121.6 nanometres is an important tracer of warm (about 104 kelvin) gas in and around galaxies, especially at cosmological redshifts greater than about 1.6 at which the spectral line becomes observable from the ground. Tracing cosmic hydrogen through its Lyman-α emission has been a long-standing goal of observational astrophysics1-3, but the extremely low surface brightness of the spatially extended emission is a formidable obstacle. A new window into circumgalactic environments was recently opened by the discovery of ubiquitous extended Lyman-α emission from hydrogen around high-redshift galaxies4,5. Such measurements were previously limited to especially favourable systems6-8 or to the use of massive statistical averaging9,10 because of the faintness of this emission. Here we report observations of low-surface-brightness Lyman-α emission surrounding faint galaxies at redshifts between 3 and 6. We find that the projected sky coverage approaches 100 per cent. The corresponding rate of incidence (the mean number of Lyman-α emitters penetrated by any arbitrary line of sight) is well above unity and similar to the incidence rate of high-column-density absorbers frequently detected in the spectra of distant quasars11-14. This similarity suggests that most circumgalactic atomic hydrogen at these redshifts has now been detected in emission.
Related projects
Project Image
Spiral Galaxies: Evolution and Consequences

Our small group is well known and respected internationally for our innovative and important work on various aspects of the structure and evolution of nearby spiral galaxies. We primarily use observations at various wavelengths, exploiting synergies that allow us to answer the most pertinent questions relating to what the main properties of

Johan Hendrik
Knapen Koelstra
Combined image of the active galaxy NGC 5643 from ALMA and VLT/MUSE data. The galaxy’s central region has two distinct components: a spiraling, rotating disc (in red) of cold molecular gas traced by carbon monoxide (CO), and the outflowing gas, traced by ionised oxygen and hydrogen (in blue-orange hues) perpendicular to the nuclear disc. Credit: ESO/A. Alonso-Herrero et al.; ALMA (ESO/NAOJ/NRAO).
Nuclear Activity in Galaxies: a 3D Perspective from the Nucleus to the Outskirts

This project consists of two main research lines. First, the study of quasar-driven outflows in luminous and nearby obscured active galactic nuclei (AGN) and the impact that they have on their massive host galaxies (AGN feedback). To do so, we have obtained Gran Telescopio CANARIAS (GTC) infrared and optical observations with the instruments

Cristina Diosco
Ramos Almeida
Type