منابع مشابه
Red Quasars Not so Dusty
Webster et al (1995) claimed that up to 80% of QSOs may be obscured by dust. They inferred the presence of this dust from the remarkably broad range of B?K optical-infrared colours of a sample of at-spectrum PKS radio QSOs. If such dust is typical of QSOs, it will have rendered invisible most of those which would otherwise been have detected by optical surveys. We used the William Herschel Tele...
متن کاملOptical spectra of dusty starbursts
This contribution presents the optical spectral properties of FIR-luminous galaxies, whose distinctive feature is often the simultaneous presence in the spectra of a strong Hδ line in absorption and of emission lines (e(a) spectra). A discrepancy between the star formation rate estimated from the FIR luminosity and that derived from the Hα luminosity persists even after having corrected the Hα ...
متن کاملComputation of the Spectra of the Quasars
The repartition of redshifts of the lines observed in the spectra of the quasars is generally considered as stochastic, but several authors showed that the difference of two redshifts is the product of an integer by a basic redshift z f = 0.062. This property results from a coherent Raman effect during the propagation of the incoherent light in a halo of atomic hydrogen , without any jet of gas...
متن کاملHigh resolution X-ray spectra of quasars
Past X-ray observations by ASCA suggest that warm absorbers (Ovii and Oviii edges) are apparently rare in high luminosity AGNs (quasars) while they are more common in low luminosity AGNs (Seyferts). However, this could be a selection effect if high luminosity AGNs have mostly narrow absorption lines (with no strong bound free edges), which escaped detection by the low resolution of ASCA. To che...
متن کاملPSPC spectra of six PG quasars and PHL 1657
We report results from the spectral analysis of pointed ROSAT PSPC observations of six PG quasars and the weak-bump quasar PHL 1657. Disregarding other frequency bands, the PSPC data are represented best by simple power-law source spectra (dN=dE / EΓ) with a slope Γ = 2:5 0:4 and do not show evidence for a more complex structure. However, within the limits given by statistics and systematical e...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 1997
ISSN: 0252-9211
DOI: 10.1017/s0252921100039804