Signatures of Cool Gas Fueling a Star-Forming Galaxy at Redshift 2.3

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Science  05 Jul 2013:
Vol. 341, Issue 6141, pp. 50-53
DOI: 10.1126/science.1234209

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Cool Accretion

Numerical models predict that in order to keep forming stars, galaxies should be continuously replenished with gas from the intergalactic medium. Using data from the Very Large Telescope in Chile, Bouché et al. (p. 50) report observations that are consistent with accretion of cold, chemically pristine gas onto a star-forming galaxy at a time when the cosmic star-formation activity was at its peak.


Galaxies are thought to be fed by the continuous accretion of intergalactic gas, but direct observational evidence has been elusive. The accreted gas is expected to orbit about the galaxy’s halo, delivering not just fuel for star formation but also angular momentum to the galaxy, leading to distinct kinematic signatures. We report observations showing these distinct signatures near a typical distant star-forming galaxy, where the gas is detected using a background quasar passing 26 kiloparsecs from the host. Our observations indicate that gas accretion plays a major role in galaxy growth because the estimated accretion rate is comparable to the star-formation rate.

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