منابع مشابه
XMM - Newton EPIC observations of 21 low - redshift PG quasars
We present an X-ray spectral analysis of 21 low redshift quasars observed with XMM-Newton EPIC. All the sources are Palomar Green quasars with redshifts between 0.05 and 0.4 and have low Galactic absorption along the line-of-sight. A large majority of quasars in the sample (19/21) exhibit a significant soft excess below ∼ 1–1.5 keV, whilst two objects (PG1114+445 and I Zw1) show a deficit of so...
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...
متن کاملFar Infrared Loud Quasars 1: Disturbed and Quiescent Quasars in the PG Survey
We use host galaxy imaging studies of the PG Quasar survey to compare the farinfrared (FIR) properties of quasars with disturbed and undisturbed host galaxies. By using survival analysis, we show that the quasars with disturbed host galaxies, with morphologies classified from a homogenous data set, have a 60μm luminosity distribution that is different from that of those with undisturbed hosts w...
متن کاملDust in PG quasars as seen by ISO
Infrared to millimeter spectral energy distributions (SEDs) have been obtained for a random sample of 17 Palomar Green quasars. The observations were carried out between 4.8 and 200 μm with ISO and supplemented for ten sources with IRAM at 1.3 mm. Eight sources were detected in the far infrared for the first time. The SEDs provide evidence for considerable dust emission and do not support the e...
متن کاملDo Quasars Lens Quasars?
If the unexpectedly high frequency of quasar pairs with very different component redshifts is due to the lensing of a population of background quasars by the foreground quasar, typical lens masses must be ∼ 10M⊙ and the sum of all such quasar lenses would have to contain ∼ 0.005 times the closure density of the Universe. It then seems plausible that a very high fraction of all ∼ 10M⊙ gravitatio...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2005
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361:20041623