On the nature of the faint /B approximately equal to 20/ ultraviolet excess objects and the problem of the X-ray background

Details On the nature of the faint /B approximately equal to 20/ ultraviolet excess objects and the problem of the X-ray background On the nature of the faint /B approximately equal to 20/ ultraviolet excess objects and the problem of the X-ray background

Oct 1980

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980a%26a....90l..10b&link_type=abstract

Astronomy and Astrophysics, vol. 90, no. 1-2, Oct. 1980, p. L10-L12.

Astronomy and Astrophysics

Astronomy

17

Background Radiation, Quasars, Ultraviolet Astronomy, X Ray Astronomy, Cosmology, Spatial Distribution, Ultraviolet Radiation

Scientific paper

A considerable fraction of the Ultraviolet Excess Objects of the Braccesi et al.(1970)list and of the 13h+36° very faint sample have shown extended images on an excellent IIIa-J, Palomar 48" plate.
We show that, at the fainter magnitudes (B ≃20), the number of resolved objects conflicts with the z distribution of QSOs derived from the assumption of simple density evolution. By dismissing the extended objects, the surface density fits the predictions of a luminosity evolution model.
On this basis we outline a picture of the QSO contribution to the X-ray background in fair agreement with observations.
This population of ultraviolet excess, fast evolving, resolvable objects seems to extend the recent observational evidence for a strong colour evolution in faint galaxies. We briefly discuss the possibility that this population could be related to the initial stages of clusters or of galaxies.

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