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Published September 7, 2001 | public
Journal Article

Hydrogen 21-Centimeter Emission from a Galaxy at Cosmological Distance

Abstract

We have detected the neutral atomic hydrogen (HI) emission line at a cosmologically significant distance [redshift (z) = 0.18] in the rich galaxy cluster Abell 2218 with the Westerbork Synthesis Radio Telescope. The HI emission originates in a spiral galaxy 2.0 h_(65) ^(−1)megaparsecs from the cluster core. No other significant detections have been made in the cluster, suggesting that the mechanisms that remove neutral gas from cluster galaxies are efficient. We infer that fewer than three gas-rich galaxies were accreted by Abell 2218 over the past 10^9 years. This low accretion rate is qualitatively consistent with low-density cosmological models in which clusters are largely assembled at z > 1.

Additional Information

© 2001 American Association for the Advancement of Science. 1 June 2001; accepted 27 July 2001. We thank the WSRT staff for assistance with the data taking and T. Galama and A. Diercks for obtaining the Keck image. A significant part of the work of M.A.Z. was carried out at the Kapteyn Astronomical Institute, the Netherlands. P.G.v.D. acknowledges support by NASA through Hubble Fellowship grant HF-01126.01-99A awarded by the Space Telescope Science Institute. Until December 2000, M.A.W.V. was employed by the National Radio Astronomical Observatory through a Jansky Fellowship. The WSRT is operated by the Netherlands Foundation for Research in Astronomy with financial support from the Netherlands Organization for Scientific Research.

Additional details

Created:
August 19, 2023
Modified:
October 18, 2023