Bibcode
Moles, M.; Garcia-Pelayo, J. M.; Masegosa, J.; Aparicio, A.; Quintana, J. M.
Referencia bibliográfica
Astronomy and Astrophysics (ISSN 0004-6361), vol. 152, no. 2, Nov. 1985, p. 271-281.
Fecha de publicación:
11
1985
Número de citas
24
Número de citas referidas
24
Descripción
UBVRI observations of 37 QSOs are reported. The sample is considered as
a good representation of the bright (V not greater than 17) quasars in
the compilation by Hewitt and Burbidge (1980). The continuum has a
steeper slope in the ultraviolet as indicated by the correlation between
the blue colors and the redshift. That spectral region appears to be
decoupled from the remainder. No differences are seen between radio
quiet and radio loud quasars in the observed colors. No direct evidence
for a synchrotron origin of the continua is present in the data since
they are poorly fitted by power laws. A principal component analysis of
the data points to the existence of two groups of quasars with
differences in their continua as well as in some of the emission lines
and in the X-ray luminosities. It is argued that the possible
non-thermal component could be diluted by other contributions in
particular that of the nebulosities surrounding the quasars.