Continuum energy distributions of quasars in the Palomar-Green Survey

Nearly simultaneous observations, from 0.3 to 2.2 µm, of the complete set of quasars found in the Palomar-Green survey are presented, along with 3.7 and 10.1 µm observations of a limited number of the quasars. The majority of the continua at rest frequencies between 10^(13.8) and 10^(15.3) Hz are consistent with fits by two power-law slopes plus a “3000 À bump.” The spectral indices representing the lower frequency observations have a median value of -1.4, while those describing the higher frequencies have a median value of -0.2. The transition frequency between these slopes is close to 10^(14.5) Hz in the rest frame; the dispersion around this frequency is about one octave. A significant fraction of the low-redshift quasars show evidence of nebulosity within 5" of the quasar