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[C ii] 158-μm emission from the host galaxies of damped Lyman-alpha systems

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Science  24 Mar 2017:
Vol. 355, Issue 6331, pp. 1285-1288
DOI: 10.1126/science.aal1737

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Identifying the hosts of quasar absorbers

If the line of sight from Earth to a distant quasar passes through foreground material, some of the quasar's light is absorbed. If a galaxy-sized quantity of gas intervenes, it forms a damped Lyman α system (DLA), visible as absorption lines in the quasar spectrum. Using the Atacama Large Millimeter/Submillimeter Array, Neeleman et al. observed two quasars with known DLAs. They detected emission from gas and dust in two foreground galaxies associated with the DLAs and were able to measure their star-formation rates. Combining these different tracers of DLAs will help us understand how galaxies evolved in the early universe.

Science, this issue p. 1285

Abstract

Gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. Using the Atacama Large Millimeter/Submillimeter Array, we report on detections of [C ii] 158-μm line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of z ~ 4. Our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies.

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