Abstract
We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range (radio to 10 keV X-rays) of the electromagnetic spectrum. The primary (UVSX) sample includes 47 quasars for which the spectral energy distributions include X-ray spectral indices and UV data. Of these, 29 are radio quiet, and 18 are radio loud. The SEDs are presented both in figures and in tabular form, with additional tabular material published on CD-ROM. Previously unpublished observational data for a second set of quasars excluded from the primary sample are also tabulated. The effects of host galaxy starlight contamination and foreground extinction on the UVSX sample are considered and the sample is used to investigate the range of SED properties. Of course, the properties we derive are influenced strongly by the selection effects induced by quasar discovery techniques. We derive the mean energy distribution (MED) for radio-loud and radio-quiet objects and present the bolometric corrections derived from it. We note, however, that the dispersion about this mean is large (approximately one decade for both the infrared and ultraviolet components when the MED is normalized at the near-infrared inflection). At least part of the dispersion in the ultraviolet may be due to time variability, but this is unlikely to be important in the infrared. The existence of such a large dispersion indicates that the MED reflects only some of the properties of quasars and so should be used only with caution.
Highlights
One of the reasons that main-sequence stars are much better understood than quasars is that they radiate blackbody spectra with temperatures between —4000 and —30,000 K, so that their blackbody peak moves conveniently through the optical band
We present an atlas of the spectral energy distributions (SEDs) of normal, nonblazar, quasars over the whole available range of the electromagnetic spectrum
By showing that most stars lie in a restricted band of color and luminosity, this diagram provided a crucial input to theories of stellar structure
Summary
One of the reasons that main-sequence stars are much better understood than quasars is that they radiate (almost) blackbody spectra with temperatures between —4000 and —30,000 K, so that their blackbody peak moves conveniently through the optical band. Quasars emit almost constant power per decade of frequency from 100 /¿m to at least 100 keV (see, e.g., Fig. 1 of Carleton et al 1987) While this equipartition is surprising and may be to some extent an observational artifact (Brissenden 1989; Elvis 1991), it contains too little information to constrain theoretical ideas. Our primary selection criteria were ( 1 ) existing Einstein observations at good signal-tonoise ratio (to ensure good X-ray spectra), and (2) an optical magnitude bright enough to make an IUE spectrum obtainable. Work included SEDs for IRASbright AGNs by Edelson & Malkan (1986), and for hard X-ray-selected Seyfert galaxies by Ward et al ( 1987 ). Our study is different in that it includes X-ray data, divided into three energy bands in many cases, for all the objects, and includes both IUE and IRAS data. Vol 95 line the features we are studying (§2) and the sample of quasars (§ 3)
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