Redshift

Physics

Halo

Quasar

Astronomy

Astrophysics

Galaxy

Gravitational lens

Gravitational potential

Nature

The halo of gas around a galaxy at redshift 1 is clumpy and anisotropic, with little variation in gas velocity, suggesting that it consists of entrained recycled material. Star-forming galaxies are surrounded by haloes of gas that has been enriched with the 'metals' created in stars and supernovae. These haloes extend out at least 100 kiloparsecs, but the structure of the gas is poorly constrained. Sebastian Lopez and collaborators use a bright gravitationally lensed arc as a back light to study Mg ɪɪ absorption in a galaxy at a redshift of 0.98. They find that the absorption strength decreases with increasing distance from the galaxy, which is in good agreement with the limited results from earlier studies. However, they find that the gas is not isotropically distributed, and that the velocity varies little over a large area. Every star-forming galaxy has a halo of metal-enriched gas that extends out to at least 100 kiloparsecs1,2,3, as revealed by the absorption lines that this gas imprints on the spectra o...

A clumpy and anisotropic galaxy halo at redshift 1 from gravitational-arc tomography