Statistical investigation of the space distribution of quasars and of their association with galaxies

Three distinct and representative sources of quasar data are used in this paper: 1) the Revised Optical Catalog of QSOs, 2) the quasars in the ?40° CTIO Curtis Schmidt Survey, and 3) the quasars in the Virgo Cluster region. Their redshift and magnitude distributions on various scales and their possible association with galaxies are analysed statistically.The preliminary conclusions are as follows. 1) The redshift and magnitude distributions on various scales are non-uniform. 2) The non-uniformity appears to be greater in the two local samples. 3) There is no evidence of a general association of quasars with field galaxies. 4) A general association of quasars with brighter cluster galaxies is statistically significant. 5) It seems likely that not all quasars have the same origin, some being local, some cosmological.     

Constraining cosmological models with cluster power spectra

Using extensive N-body simulations we estimate redshift space power spectra of clusters of galaxies for different cosmological models (SCDM, TCDM, CHDM, ΛCDM, OCDM, BSI, τCDM) and compare the results with observational data for Abell–ACO clusters. Our mock samples of galaxy clusters have the same geometry and selection functions as the observational sample which contains 417 clusters of galaxies in a double cone of galactic latitude |b|>30° up to a depth of 240 h⁻¹ Mpc. The power spectrum has been estimated for wave numbers k in the range 0.03k0.2 h Mpc⁻¹. For k>k_max0.05 h Mpc⁻¹ the power spectrum of the Abell–ACO clusters has a power-law shape, P(k)∝kⁿ, with n≈−1.9, while it changes sharply to a positive slope at k<k_max. By comparison with the mock catalogues SCDM, TCDM (n=0.9), and also OCDM with Ω₀=0.35 are rejected. Better agreement with observation can be found for the ΛCDM model with Ω₀=0.35 and h=0.7 and the CHDM model with two degenerate neutrinos and Ω_HDM=0.2 as well as for a CDM model with broken scale invariance (BSI) and the τCDM model. As for the peak in the Abell–ACO cluster power spectrum, we find that it does not represent a very unusual finding within the set of mock samples extracted from our simulations.     

Triple splitting with the F2-region of the ionosphere at high and mid-latitudes

The occurrence of the third (z-ray) component of the F2-trace on ionograms is investigated at high- and mid-latitudes. Diurnal variations show a systematic shift, with magnetic inclination, of the time of maximum occurrence. Seasonal variations show a winter maximum, and an inverse sunspot-cycle relationship exists. Maximum occurrence appears between a magnetic inclination of 70° and 80° with a fall-off either side.

Evidence is presented to suggest a z-ray association with “Spread-F” fronts, and a possible mechanism for the recording of the z-ray trace at the transmitter site is described. This involves longitudinal propagation of the o-mode at its normal reflection level, coupling at this point, and ultimate reflection for the z-ray mode as a result of sloping ionization contours belonging to “Spread-F” fronts extending in directions perpendicular to the magnetic meridian.

An association with V.L.F. emissions (“dawn-chorus”) is discussed.     

Periodic redshift distribution of quasars associated with low — redshift galaxies

We applied power spectral analysis to the redshift distribution of the quasars associated with low-redshift galaxies. Periodicity is confirmed at a level of confidence >99%, with a period of Δln(1+z) = 0.206. This result is exactly the same as previously found for different quasar samples. The periodicity is not caused by any selection effect in the emission lines. The two phenomena, the periodicity in the redhsift distribution and the association of quasars with low-redhsift galaxies can both be rather well explained by a multiply-connected model of the universe.     

The Steep Balmer Decrement of Quasars and Seyfert I Galaxies and its Origin

Observations of QSOs and Seyfert I galaxies show an anomalously steep Balmer decrement, which is in contradiction to the prediction of the traditional recombination theory. This is a long standing puzzle in past three decades in the study of AGNs. In this paper, we provide an alternative approach to solve this puzzle by using a newly recognized line emission mechanism, namely, the “Cerenkov line-like radiation”. For this purpose, we collected about a hundred of QSOs and Seyfert I galaxies, whose Balmer decrements have been measured and published in the past 30 years, and make the theoretical calculations on the observed Balmer decrements using an improved formula for the Cerenkov line intensity. The agreement between the calculations and observations is excellent. Therefore, we argue that the broad hydrogen lines of the QSOs and Seyfert I galaxies mainly originate from the Cerenkov line-like radiation of relativistic electrons. If this suggestion is further confirmed, our knowledge about the physics of AGNs will be greatly changed.     

Response time of the high-latitude dayside ionosphere to sudden changes in the north-south component of the IMF

The time scale of the response of the high-latitude dayside ionospheric flow to changes in the North-South component of the interplanetary magnetic field (IMF) has been investigated by examining the time delays between corresponding sudden changes. Approximately 40 h of simultaneous IMF and ionospheric flow data have been examined, obtained by the AMPTE-UKS and -IRM spacecraft and the EISCAT “Polar” experiment, respectively, in which 20 corresponding sudden changes have been identified. Ten of these changes were associated with southward turnings of the IMF, and 10 with northward turnings. It has been found that the corresponding flow changes occurred simultaneously over the whole of the “Polar” field-of-view, extending more than 2° in invariant latitude, and that the ionospheric response delay following northward turnings is the same as that following southward turnings, though the form of the response is different in the two cases. The shortest response time, 5.5 ± 3.2 min, is found in the early- to mid-afternoon sector, increasing to 9.5 ± 3.0 min in the mid-morning sector, and to 9.5 ± 3.1 min near to dusk. These times represent the delays in the appearance of perturbed flows in the “Polar” field-of-view following the arrival of IMF changes at the subsolar magnetopause. Overall, the results agree very well with those derived by Etemadi et al. (1988, Planet. Space Sci. 36, 471) from a general cross-correlation analysis of the IMF B_z and “Polar” beam-swinging vector flow data.     

Statistical analysis of the optical variability of QSO's

For 34 QSOs and 9 active galaxies with known optical variation and measured redshifts, the rate of optical variation appears to be positively correlated with the age: older quasars vary more violently than younger ones and active galaxies are the most violent of all.     

Influence of Gravitational Lensing on the Determination of the Luminosity Function of Background Objects

The distribution function of quasars with respect to apparent brightness is given, found under the assumption that quasars are, at least partially, the gravitationally enhanced images of the active nuclei of distant galaxies. A Schechter law and a two-power law for the luminosity function of the sources are used, as well as a probabilistic law of image enhancement for various models of gravitational lenses. To find the theoretical distribution function of quasars with respect to apparent brightness we use a theorem on the probability density of a product of random quantities. It is shown that the slope of this function ranges from -1 to -2 for faint quasars, like that for ordinary galaxies. In the case of bright quasars, the slope of the apparent brightness distribution function is determined mainly by the lensing effect and has a lower limit of -3. The good agreement between theory and observations suggests that statistically quasars are gravitationally enhanced images of the active nuclei of distant galaxies. If the initial assumptions are correct, then the luminosity function of galaxies and the apparent brightness function for quasars are not independent but are related by means of the differential lensing probability.     

Tianjin photographic zenith tube observations

In this paper we analyse the observational data obtained by the Chinese-made PZT in the two periods 1979 Feb – 1980 May and 1981 Dec – 1983 March. The internal accuracy of single star is found to be m_u = ±13.0 ms, m_φ = ±0. “144 for the first period, and m_u = ±14.6 ms, m_φ = ±0.” 152 for the second. Correction of star position is found by the chain method. The systematic error caused by the sealed window of the evacuated chamber and the temperature effect of the plate scale are investigated. Monthly means of time and latitude are given.     

Some aspects of Sporadic-E at mid-latitudes

Evidence is presented to suggest that the ƒ₀E_s value tends to be high at positions in the E_s-layer where trough slope-lines and crest slope-lines of F2-layer irregularities meet the E_s-layer. These slope-lines are drawn through the troughs and crests, respectively, of the characteristic kinks in the F2-layer ionization contours, which are associated with F2-layer irregularities.

A rotating-loop direction-finding system has allowed an estimation of the distribution of ionization, which gives rise to Sporadic-E echoes. Analysis of Sporadic-E occurrence, on two occasions, suggests that the reflecting surfaces are frontal in nature, the fronts having a separation from each other of some tens of kilometres, and probably existing as closed curves, with diameters of the order of several hundreds of kilometres. A possible association between these structures and the occurrence of the green line of the airglow, is discussed.

A distribution of ionization, which will give contours showing “clouds” of ionization at some frequencies and a ripple structure at other frequencies, is proposed, in an endeavour to explain the apparent dual nature of Sporadic-E occurrence.

The evidence seems to indicate that the mechanism operating at the E_s-layer level, producing the phenomenon of Sporadic-E, is the same as that which produces the F2-layer irregularities which are responsible for “Spread-F”.     

The HNCO ring in the Sgr B2 region

The large-scale structure associated with the 2′N HNCO peak in Sgr B2 [Minh, Y.C., Haikala, L., Hjalmarson, Å., Irvine, W.M., 1998. ApJ 498, 261 (Paper I)] has been investigated. A ring-like morphology of the HNCO emission has been found; this structure may be colliding with the Principal Cloud of Sgr B2. This “HNCO Ring” appears to be centered at (l,b) = (0.7°,−0.07°), with a radius of 5 pc and a total mass of 1.0 × 10⁵ to 1.6 × 10⁶ M. The expansion velocity of the Ring is estimated to be 30–40 km s⁻¹, which gives an expansion time scale of 1.5 × 10⁵ year. The morphology suggests that collision between the Ring and the Principal Cloud may be triggering the massive star formation in the Sgr B2 cloud sequentially, with the latest star formation taking place at the 2′N position. The chemistry related to HNCO is not certain yet, but if it forms mainly via reaction with the evaporated OCN⁻ from icy grain mantles, the observed enhancement of the HNCO abundance can be understood as resulting from shocks associated with the collision between the Principal Cloud and the expanding HNCO Ring.     

Quasar–galaxy associations revisited

Gravitational lensing predicts an enhancement of the density of bright, distant quasi-stellar objects (QSOs) around foreground galaxies. We measure this QSO–galaxy correlation w _qg for two complete samples of radio-loud quasars, the southern 1 Jy and half-Jansky samples. The existence of a positive correlation between     quasars and     galaxies is confirmed at a     per cent significance level (>99.9 per cent if previous measurements on the northern hemisphere are included). A comparison with the results obtained for incomplete quasar catalogues (e.g. the Veron-Cetty and Veron compilation) suggests the existence of an 'identification bias', which spuriously increases the estimated amplitude of w _qg for incomplete samples. This effect may explain many of the surprisingly strong quasar–galaxy associations found in the literature. Nevertheless, the value of w _qg that we measure in our complete catalogues is still considerably higher than the predictions from weak lensing. We consider two effects which could help to explain this discrepancy: galactic dust extinction and strong lensing.     

Fluctuations in tidal (24-, 12-h) characteristics and oscillations (8-h-5-d) in the mesosphere and lower thermosphere (70–110 km): Saskatoon (52°N, 107°W), 1979–1981

An M.F. radar (2.2 MHz) operating at Saskatoon, Canada (52°N, 107°W) has been used to produce continuous wind data ( 80–110km) from September 1978–April 1981. The 24-, 12-h tidal oscillations reveal regular summer-winter transitions; in particular the semi-diurnal tide demonstrates strikingly regular and rapid equinoctial changes over the three years. The vernal and autumnal equinox changes are clearly different in morphology. Shorter term tidal fluctuations (2d τ 10d) are compared with mean winds and gravity wave amplitudes, as well as with satellite-derived stratospheric temperatures.

Spectral analysis of monthly data sets for 1980, from 90–105 km, reveal oscillations of the expected 8-, 12-, 24-h periods, but also of 10-, 16- and 2-, 5/6d. A modulation of the “2-d” wave by the 12-h wave is suggested as a possible cause of these surprisingly regular oscillations.     

Maximum likelihood estimation of the mean parallax and kinematic parameters of the Pleiades

A simultaneous, maximum-likelihood determination of the distance and kinematic parameters of the Pleiades is made. The results are: distance of the cluster d = 135.56 ± 0.72 pc, dispersion σ_d = 7.66 ± 0.80 pc; space velocity V = 25.94 ± 0.13 km/s, dispersion σ_v = 0.58 ± 0.09 km/s coordinates of the convergent point A = 101.95° ± 0.47°, D = −41.36° ± 0.29°.     

The environments of intermediate-redshift QSOs: 0.3 < z < 0.7

An angular correlation of low significance (2 σ ) is observed between 0.3< z <0.5 QSOs and V 23 galaxies. Overall, the cross-correlation function between 82 intermediate-redshift (0.3< z <0.7) X-ray selected QSOs and V ≲24 galaxies is investigated, but no signal is detected for the z >0.5 QSOs. After converting to an excess of galaxies physically associated with the QSO, this lack of strong correlation is shown to be consistent with the clustering of normal galaxies at the same moderate redshifts. Combined with previous observations, these results imply that the environments of radio-quiet QSOs do not undergo significant evolution with respect to the galaxy population over a wide range of redshifts (0< z <1.5). This is in marked contrast to the rapid increase in the richness of the environments associated with radio-loud QSOs over the same redshift range.     

The environment of QSOs (invited review)

The evidence for the association of QSOs with groups of galaxies and the available data on the global properties of such groups are reviewed. At least for redshifts less than 0.5, QSOs tend to occur in richer-than-average environments. There is some evidence that groups around steep-radio-spectrum QSOs are systematically richer than those around radio-quiet and flat-radiospectrum QSOs. The groups associated with the former may sometimes reach central galaxy number densities similar to those of moderately rich clusters, but are significantly more compact, and there is no evidence that any such groups have velocity dispersions above a few hundred km s^–1.A possible explanation for this environmental preference can be found in the recent evidence, from a variety of directions, that galaxy interactions play an important role in triggering nuclear activity. A significant fraction of low-redshift QSOs either have close companions at the same redshift, or show some indication of recent interaction. The results of a recent search for resolvable extended emission around a large sample of luminous low-redshift QSOs are described. There are now substantial reasons for believing that the presence of these extended emission-line regions, which are found around approximately 25% of all low-redshift OSOs, is often a signature of a recent interaction.Observed correlations between radio properties, optical spectra, and environment are mentioned briefly. The present evidence tends to support suggestions that there are two classes of QSOs, one being the extension of the Seyfert population to higher luminosities and having spiral host galaxies, the other being closely related to the broad-line radio galaxies. The host galaxies of this latter class appear often to be morphologically ellipticals, but may in fact be products of recent mergers.Paper presented at the Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Examination of the Association between Quasars and Abell Clusters on All Sky

Using the Hewitt-Burbidge QSO Catalogue (1993) and all-sky catalogue of Abell clusters (ACO, 1989) at the region |b| > 40^° we analyze the cross correlation function and find anti-correlation between them at angular separations 3^° < θ < 10^° , which is mainly caused by optical-selected QSOs, rather than radio-selected QSOs. There is no such anti-correlation between QSOs and Abell clusters at smaller separations θ < 3^°. Considering that this phenomenon may be caused by different characters of the objects, we further estimate the correlation function with various subsamples. We find that the correlation is independent of the redshift of QSOs, but depends upon the type of Abell clusters: for the D ≤ 4 clusters there is an obvious tendency of overdensity of quasars at 0^° < θ < 5^°; around the R ≥ 2 Abell clusters there is about an 18.7% deficit of quasars in the region 3^° < θ < 7^°. K-S Test shows the overdensity or deficit of quasars around different types of clusters cannot be explained by the projection effect of background quasars. We get the enhancement factor of quasar overdensity (for D ≤ 4 clusters) q =1.13, and the extinction magnitude factor of QSO deficiency (for R ≥ 2 clusters) Av= 0.14. This revised version was published online in July 2006 with corrections to the Cover Date.     

Near-infrared surface photometry of bulges and disks of spiral galaxies. The data

We present optical and near-infrared (NIR) surface brightness and colour profiles, in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 °. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-colour images are presented, as well as colour index maps. This data set, tailored for the study of the population characteristics of galaxy bulges, provides useful information on the colours of inner disks as well. In related papers, we have used them to quantify colour gradients in bulges, and age differentials between bulge and inner disk.     

Geminid Meteor shower activity 2003–2005 as observed by Gadanki radar

The distribution of meteor signals reflected from a backscatter radar is considered according to their duration. This duration time (T) is used to classify the meteor echoes and to calculate the mass index (S) of different meteoroids of shower plus sporadic background. Observational data on particle size distribution of the Geminid meteor shower are very scarce, particularly at low latitudes. In this paper the observational data from Gadanki radar (13.46°N, 79.18°E) have been used to determine the particle size distribution and the number density of meteoroids inside the stream of the Geminid meteor shower. The mean variation of meteor number density across the stream has been determined for three echo duration classes, T<0.4, T=0.4–1 and T>1 s. We are more interested in the appearance of echoes of various durations and therefore meteors of various masses in order to understand more on the filamentary structure of the stream. It is observed that the faint particle flux peaks earlier than the larger particles. We found a decreasing trend in the mass index values from the day of peak activity to the next observation days. The mass index profile was found to be U-shaped with a minimum value near the time of peak activity. The observed minimum s values are 1.64±0.05 and 1.65±0.04 in the years 2003 and 2005, respectively. The activity of the shower indicates the mass segregation of meteoroids inside the stream. Our results are best comparable with the “scissors” structure model of the meteoroid stream formation of Ryabova [2007. Mathematical modeling of the Geminid meteoroid stream. Mon. Not. R. Astron. Soc. 375, 1371–1380] by considering the asteroid 3200 Phaethon as an extinct comet.     

Optical microvariability of selected PG QSOs

This is a preliminary report of the continuing search for significant optical microvariability in a selected sample of radio-quiet and radio-loud quasi-stellar objects (QSOs). Total of 24 Paloma-Green (PG) quasars are observed. Among them, 17 objects are classified as radio-quiet and seven objects are classified radio-loud. In this classification, the ratio R, radio to optical flux density, is required to be less than 1 in order to assure the objects are reasonably radio-quiet. Two out of 17 radio-quiet QSOs and six out of eight radio-loud QSOs were microvariable. This apparent contrast in microvariations between radio-quiet and radio-loud QSOs does not provide firm support for the theoretical model utilizing discrete events in accretion disks and implies substantial support for models based on propagating shocks on relativistic jets as the likely process responsible for producing most of the microvariations are observed in AGNs.