The Multi-Wavelength Quasar Survey IV. Quasars in the Leo Cluster

We aim to providea quasar sample that is more complete than any previous surveys by using a combined selection technique to reduce the selection effects. Here we present the observational results for the X-ray candidates in the field of the Leo Cluster. We found 33 X-ray AGNs in this field of which 10 are new discoveries. The X-ray data and optical spectra of these AGNs are given. We also study the near-IR properties of the X-ray-selected AGNs by using the data from 2MASS. Most of the AGNs in our sample span the color range 0.0 < B-J < 2.5, 1.0 < J-Ks < 2.0 and 0.5 < H-Ks < 1.2.     

The SuperCOSMOS Sky Survey – III. Astrometry

In this, the third in a series of three papers concerning the SuperCOSMOS Sky Survey, we describe the astrometric properties of the data base. We describe the algorithms employed in the derivation of the astrometric parameters of the data, and demonstrate their accuracies by comparison with external data sets using the first release of data, the South Galactic Cap survey. We show that the celestial coordinates, which are tied to the International Celestial Reference Frame via the Tycho–2 reference catalogue, are accurate to better than ±0.2 arcsec at J , R ∼19,18 , rising to ±0.3 arcsec at J , R ∼22,21 , with positional-dependent systematic effects from bright to faint magnitudes at the ∼0.1-arcsec level. The proper motion measurements are shown to be accurate to typically ±10 mas yr⁻¹ at J , R ∼19,18 , rising to ±50 mas yr⁻¹ at J , R ∼22,21 , and are tied to zero using the extragalactic reference frame. We show that the zero-point errors in the proper motions are ≤1 mas yr⁻¹ for R >17 , and are no larger than ∼10 mas yr⁻¹ for R <17 mas yr⁻¹ .     

The Nearby Field Galaxy Survey

We report on our observing programme to obtain integrated spectrophotometry, intermediate- and high-resolution major-axis spectra, and UBR surface photometry of a representative sample of ∼ 200galaxies in the nearby field. The main goal of this programme is to provide a comparison sample for high-redshift studies and to study the variation in star formation rates (SFRs), star formation history (SFH),excitation, metallicity, and internal kinematics over a wide range of galaxy luminosities and morphological types. In particular, we extend the work of Kennicutt (1992) to lower-luminosity systems. We present the main results of our analysis so far. In these proceedings, we condense the two atlases presented of 1) images and radial surface brightness profiles and colour profiles, and 2) images and integrated spectra into several example images, profiles and spectra, showing the general trends observed. For the original atlases we refer the reader to the electronic distribution on CDROM or as available on the Web at http://www.astro.rug.nl/∼nfgs/. This revised version was published online in July 2006 with corrections to the Cover Date.     

A Comparison of BBN,ADTree and MLP in separating Quasars from Large Survey Catalogues

We compare the performance of Bayesian Belief Networks (BBN), Multilayer Perception (MLP) networks and Alternating Decision Trees (ADtree) on separating quasars from stars with the database from the 2MASS and FIRST survey catalogs. Having a train- ing sample of sources of known object types, the classifiers are trained to separate quasars from stars. By the statistical properties of the sample, the features important for classifica- tion are selected. We compare the classification results with and without feature selection. Experiments show that the results with feature selection are better than those without feature selection. From the high accuracy found, it is concluded that these automated methods are robust and effective for classifying point sources. They may all be applied to large survey projects (e.g. selecting input catalogs) and for other astronomical issues, such as the parame- ter measurement of stars and the redshift estimation of galaxies and quasars.     

On the Nature of the FBS Blue Stellar Objects and the Completeness of the Bright Quasar Survey. II

In Paper I we compared the surface density of QSOs in the Bright Quasar Survey (BQS) and in the First Byurakan Survey (FBS) and concluded that the completeness of the BQS is of the order of 70% rather than 30-50% as suggested by several authors. A number of new observations recently became available, allowing a reevaluation of this completeness. We now obtain a surface density of QSOs brighter than B = 16.16 in a subarea of the FBS covering 2250 deg², equal to 0.012 deg^-2 (26 QSOs), implying a completeness of 53 ± 10%.     

类星体红移分布的高频周期

本文对Ｖｅｒｏｎ－Ｃｅｔｔｙ和Ｖｅｒｏｎ类星体表中３１９７颗红移精度为０．００１的类星体做了红移分布的周期性分析。结果表明：类星体红移值在几个方向上存在高频波动的周期性分布，且置信度水平较高。根据我们的分析，这种周期性不可能完全是由于选择效应引起的。因此，类星体在大尺度上的分布很可能具有大约５０Ｍｐｃ的周期涨落。     

The Parkes Southern Pulsar Survey — III. Timing of long-period pulsars

The Parkes survey of the entire southern sky for millisecond and other low-luminosity pulsars has now been completed. The survey system and initial results were described by Manchester et al. and the final results and population studies are described by Lyne et al. A total of 298 pulsars were detected, including 101 new discoveries of which 17 were millisecond pulsars. Here we report on timing observations at Parkes and Jodrell Bank of the 84 long-period (non-millisecond) pulsars discovered in the survey, including timing solutions for 78 of them. Pulse profiles and arrival times were obtained at several different frequencies over intervals of more than a year, yielding a position, period, period derivative and dispersion measure for each pulsar. Pulse profiles at frequencies near 400 MHz and 600 or 1400 MHz are presented for most of the observed pulsars. Significant timing noise was detected for five pulsars and a glitch was observed in the period of PSR J1123–6259.     

Slit spectra of galaxies of the Second Byurakan Survey. III

Special Astrophysical Observatory, USSR Academy of Sciences; Byurakan Astrophysical Observatory. Translated from Astrofizika, Vol. 29, No. 3, pp. 548–555, November–December, 1988.     

类星体3C 273的射电流量和偏振度关系

利用UMRAO数据平台,研究了类星体3C273的射电流量密度与偏振度的关系（包括4.8GHz,8GHz和14.5GHz3个频段）,结果发现偏振度与射电流量在3个频段都具有很强的负相关性。这些结果可能表明3C273的射电流量密度和偏振度的变化与聚束效应无关。一般,偏振度与流量密度的强负相关现象可以用喷流成分＋激波成分的双成分模型来解释：在喷流成分与激波成分的偏振角相互垂直并且偏振度基本相同的情况下,激波在喷流中的传播产生了这些偏振度与流量密度的强负相关性。     

A Nonlinear Force-Free Magnetic Field Approximation Suitable for Fast Forward-Fitting to Coronal Loops. III. The Free Energy

Stereoscopic white-light imaging of a large portion of the inner heliosphere has been used to track interplanetary coronal mass ejections. At large elongations from the Sun, the white-light brightness depends on both the local electron density and the efficiency of the Thomson-scattering process. To quantify the effects of the Thomson-scattering geometry, we study an interplanetary shock using forward magnetohydrodynamic simulation and synthetic white-light imaging. Identifiable as an inclined streak of enhanced brightness in a time–elongation map, the travelling shock can be readily imaged by an observer located within a wide range of longitudes in the ecliptic. Different parts of the shock front contribute to the imaged brightness pattern viewed by observers at different longitudes. Moreover, even for an observer located at a fixed longitude, a different part of the shock front will contribute to the imaged brightness at any given time. The observed brightness within each imaging pixel results from a weighted integral along its corresponding ray-path. It is possible to infer the longitudinal location of the shock from the brightness pattern in an optical sky map, based on the east–west asymmetry in its brightness and degree of polarisation. Therefore, measurement of the interplanetary polarised brightness could significantly reduce the ambiguity in performing three-dimensional reconstruction of local electron density from white-light imaging.     

Search for Optical Identifications in the 5C3-Radio Survey III. Spectroscopic Results

52 possible optical identifications (V ≲ 19.5) of 43 radio sources of the ₅C₃ area have been spectroscopically examined by use of objective prism plates from KARL SCHWARZSCHILD Observatory Tautenburg. The aim was to select objects of special interest for further slit spectrographic investigation. Besides 42 probably ordinary stars and 3 galaxies, five quasar spectra have been found, but only one redshift could be determined. Two further objects probably have unusual spectra.     

The Durham/UKST Galaxy Redshift Survey – III. Large-scale structure via the two-point correlation function

We have investigated the statistical clustering properties of galaxies by calculating the two-point galaxy correlation function from the optically selected Durham/UKST Galaxy Redshift Survey. This survey is magnitude-limited to b _J∼17, contains ∼2500 galaxies sampled at a rate of one-in-three and surveys a ∼4×10⁶ ( h ⁻¹ Mpc)³ volume of space. We have empirically determined the optimal method of estimating the two-point correlation function from just such a magnitude-limited survey. Applying our methods to this survey, we find that our redshift-space results agree well with those from previous optical surveys. In particular, we confirm the previously claimed detections of large-scale power out to ∼40 h ⁻¹ Mpc scales. We compare with two common models of cosmological structure formation and find that our two-point correlation function has power significantly in excess of the standard cold dark matter model in the 10–30 h ⁻¹ Mpc region. We therefore support the observational results of the APM galaxy survey. Given that only the redshift-space clustering can be measured directly, we use standard modelling methods and indirectly estimate the real-space two-point correlation function from the projected two-point correlation function. We then invert this projected correlation function to obtain an estimate of the spatial two-point correlation function in real space. This correlation function in real space has a lower amplitude than that in redshift space, but a steeper slope.     

The European Large Area ISO Survey – III. 90-μm extragalactic source counts

We present results and source counts at 90 μm extracted from the preliminary analysis of the European Large Area ISO Survey (ELAIS). The survey covered about 12 deg² of the sky in four main areas and was carried out with the ISOPHOT instrument onboard the Infrared Space Observatory ( ISO ). The survey is at least an order of magnitude deeper than the IRAS 100-μm survey and is expected to provide constraints on the formation and evolution of galaxies. The majority of the detected sources are associated with galaxies on optical images. In some cases the optical associations are interacting pairs or small groups of galaxies, suggesting that the sample may include a significant fraction of luminous infrared galaxies. The source counts extracted from a reliable subset of the detected sources are in agreement with strongly evolving models of the starburst galaxy population.