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An Active Galactic Nucleus Sample with High X-Ray-to-Optical Flux Ratio from RASS. II. Optical Emission Line Properties of Seyfert 1-Type Active Galactic Nuclei
This work studies the optical emission line properties of a sample of155 low-redshift bright X-ray-selected ROSAT Seyfert 1-type activegalactic nuclei for which adequate signal-to-noise ratio spectroscopicobservations are available. We measured emission-line properties byperforming multicomponent fits to the emission-line profiles, coveringthe effect of blended iron emission. We also obtained continuumparameters, including 250 eV X-ray luminosities derived from the ROSATdatabase. In addition, the measured properties are gathered for acorrelation analysis, which confirms the well-known relations betweenthe strengths of Fe II, [O III] emission and the X-ray slope. We alsodetect striking correlations between Hβ redshift (or blueshift) andflux ratios of Fe II to Hβ broad component and [O III] to Hβnarrow component. These trends are most likely driven by the Eddingtonratio.
| An AGN sample with high X-ray-to-optical flux ratio from RASS. I. The optical identification
We present the first results of a program to identify the unknown brightactive galactic nuclei (AGN) in the ROSAT All Sky Survey Bright SourceCatalog (RASS-BSC). We have used log C + 0.4 R as an alternativeexpression for log (f_X/fopt), where C is X-ray count rateand R stands for R magnitude. Then a high X-ray-to-optical flux ratiocriterion has been used to select an AGN sample with 165 unidentifiedX-ray sources for optical spectroscopy. Those 165 X-ray sources havebeen identified in the following classes: 115 emission line AGN (QSOsand Seyferts), 2 BL Lac objects and 4 BL Lac candidates, 22 clusters ofgalaxies, 12 Galactic stars and 10 objects remain unidentified. Thisrepresent a success rate of about 73% for detecting AGN using ourselection criteria. Plausibility is based upon the opticalclassification and X-ray characteristics of the sources.
| The ROSAT AGN content of the 87GB 5 GHz survey: bulk properties of previously optically identified sources.
The cross-correlation of the source list from the ROSAT All-Sky Surveywith the 5 GHz Green Bank survey yields a list of 2127 objects. Abouttwo thirds of them are optically unidentified. The majority of theobjects with known optical counterparts are quasars and radio galaxies,most of them detected in X-rays for the first time. In this paper wepresent a list of the previously optically identified objects with theirmain characteristics and discuss their general (bulk) properties. Wefind strong correlations between luminosities in the radio, optical, andX-ray bands which differ for quasars and radio galaxies. The fraction offlat radio spectrum sources increases with redshift and ~ 95% of allsources above z = 2 are of that type. In the relatively large group ofblazars, radio selected BL Lacs and highly polarized quasars show verysimilar properties while X-ray selected BL Lacs have markedly differentX-ray to radio flux ratios. The sample is large enough and ofsufficiently high quality to reveal clearly various detection biases andselection effects which strongly influence the physical interpretationof the correlations. Radio follow - up observations for thedetermination of the morphological and spectral properties as well asenvironmental conditions are needed for a statistically reliable studyof the sample. The very large group of sources with low radio fluxesremains to be optically identified.
| A survey of the Pisces-Perseus supercluster. VI - The declination zone +15.5 deg to 21.5 deg
New results are presented of Arecibo observations in the 21 cm line of765 galaxies with declinations between 15.5 deg and 21.5 deg, in thePisces-Perseus supercluster zone. If considered independently on theneighboring parts of sky, this region, to the South of the superclusterridge, shows significantly less evidence of structure on large scales inexcess of 30 Mpc, contrasting substantially with the characteristics ofthe declination zones immediately to the North.
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