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This schematic behavior has held up in later studies

This schematic behavior has held up in later studies - This...

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This schematic behavior has held up in later studies, while at higher redshift the observed numbers are increasingly deficient compared to extrapolations of this behavior. This has been reviewed by, for example, Shaver et al. 1996 Nature 384, 449) from which the following plot was adapted: The implications of quasars at redshifts z > 4 have been discussed by Turner 1991 (AJ 101, 5), and are only getting stronger as a few objects turn up at higher and higher redshift. Generally, galaxies must have formed by z =5 or even better z =10 to expect enough dense cores to make high-redshift quasars. He cautions that beaming or gravitational amplification, if either operates differently on this population than for other QSOs, would complicate the analysis tremendously. There has been an explosion in the number of high-redshift quasars known, with 104 listed above z =4.0 in the 9th edition of the Veron-Cetty and Veron catalog . And this, of course, was before the SDSS color-selected samples became available.
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