Molecular gas in the host galaxy of a quasar at redshift z = 6.42

Walter, Fabian
Bertoldi, Frank
Carilli, Chris
Cox, Pierre
Lo, K. Y.
Neri, Roberto
Fan, Xiaohui
Omont, Alain
Strauss, Michael A.
Menten, Karl M.

* National Radio Astronomy Observatory, PO Box 0, Socorro, New Mexico 87801, USA
† Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
‡ Institut d'Astrophsique Spatiale, Universite de Paris-Sud, 91405 Orsay, France
§ IRAM, 300 Rue de la Piscine, 38406 St-Martin-d'Heres, France
∥ Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, Arizona 85721, USA
¶ Institut d'Astrophysique de Paris, CNRS & Université Paris 6, 75014 Paris, France
# Princeton University Observatory, Princeton, New Jersey 08544, USA

Received 16 May; accepted 16 June 2003; doi:10.1038/nature01821.

Correspondence and requests for materials should be addressed to F.W. ([email protected]).

Nature 424(6947):p 406-408, July 24, 2003.

Observations of molecular hydrogen in quasar host galaxies at high redshifts provide fundamental constraints on galaxy evolution, because it is out of this molecular gas that stars form. Molecular hydrogen is traced by emission from the carbon monoxide molecule, CO; cold H₂itself is generally not observable. Carbon monoxide has been detected in about ten quasar host galaxies with redshiftsz > 2; the record-holder is atz = 4.69 (refs). Here we report CO emission from the quasar SDSS J114816.64 + 525150.3 (refs) atz = 6.42. At that redshift, the Universe was only 1/16 of its present age, and the era of cosmic reionization was just ending. The presence of about 2 × 10¹⁰M_⊙of H₂in an object at this time demonstrates that molecular gas enriched with heavy elements can be generated rapidly in the youngest galaxies.