Current Science at NOAO

The Most Distant Quasar Known

Daniel Stern, NASA/JPL

The image shows the area of sky where the quasar was detected in red and near-infrared light.

March, 2000  |  Astronomer Daniel Stern and collaborators discovered the most distant quasar known in the Universe, a quasar at a redshift of z=5.5. The discovery was made using the National Science Foundation's 4-m Mayall Telescope at Kitt Peak , as well as the Palomar 200" and the 10-m Keck Telescope.

The quasar was discovered as part of a deep imaging survey to probe the first billion years of galaxy formation in the Universe.

Imaging surveys are among the most useful tools for probing the evolution of galaxies and quasars. Wide-field, "shallow'' surveys such as the Palomar Digital Sky Surveys and Sloan Digital Sky Survey have been very successful at identifying bright, high-redshift quasars at redshifts between z=4 and z=5. Deep, smaller field surveys probe star-forming galaxies at earlier cosmic epoch.

The newly discovered quasar, named RD300, was the brightest candidate from their current survey area covering 74 square arcminutes of sky. The quasar is not seen in images taken in red light, but is faintly detected at longer wavelengths in the near-infrared. The image shows the area of sky where the quasar was detected in red and near-infrared light.

A spectrum obtained on the Keck II Telescope confirmed that the object is an extremely high-redshift quasar. The spectrum shows broad emission from hydrogen Lyman-alpha and ionized nitrogen, as well as absorptions from intervening material at lower redshift.

Surprisingly, RD300, is not one of the intrinsically brightest quasars known. Its actuall luminosity is comparble to lower luminosity quasars in the more-nearby Universe. If the distribution of quasar luminosities is the same at the high redshift of RD300 as it is at lower redshift, then faint, distant quasars may be more common than expected.

For more information see:
   NOAO Newsletter
   JPL Press Release
   JPL Press Release Images
   Redshifts of Quasi-Stellar Objects

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