Sloan Quasar Survey
Sloan Digital Sky Quasar Survey
| Group Name | SloanQSOs |
| Reference | Sloan Digital Sky Survey |
| Prepared by | Eric Gawiser (Rutgers University) |
| Labels | No |
| Files | sdssqsos.speck |
| Dependencies | none |
| Census | 90,509 quasars |
The Sloan Quasar Survey contains over 90,000 quasars that extend beyond the Sloan galaxies. This makes sense, as they come from the same observations that were made to compile the Sloan galaxy catalog.
The SDSS quasars have the same data variables listed in the section describing the 2dF galaxies, with the exception of the release variable describing the data release (see “Sloan Digital Sky Galaxy Survey”). Of course, the range of these variables is dramatically different from that of the SDSS galaxies. Generally, the objects are dimmer from our perspective; their average distance is 12.5 billion light-years, compared with 1.8 billion light-years for the galaxies. And the look-back time, the length of time the light has been traveling, is 8 billion years on average, while it is only 1.7 billion years for the galaxies.
These differences are not at all surprising given that quasars are thought to represent galaxies in their early stages of evolution. If we could travel instantaneously to a Sloan quasar that is 10 billion light-years from Earth, we would see that the quasar has evolved into a “normal” galaxy like those in our neighborhood. And looking back to the Milky Way, we would see a galaxy in its quasar stage of evolution.
The SDSS quasars appear to have no obvious signs of large-scale structure. There is a pattern that depends on distance, which we might expect to see since this is an observed catalog and the brightness of objects falls off with distance. Around 16 billion light-years, the data begin to “fade out,” or become sparse. You'll notice too that the 2dF quasars cut off at this same distance, around 20 billion light-years. However, the lack of structure within the data results from the fact that quasars are relatively rare and represent only a sparse sampling of the large-scale structure that exists.
Quasars are among the farthest objects we see, but they do not take us all the way back to the beginning of the Universe. To peer into the earlier Universe, we look to the cosmic microwave background light seen in the WMAP all-sky survey.
© 2002-2005 American Museum of Natural History
Last Modified: 2007-12-19 by Brian Abbott