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.     

Radio-quiet quasar environments at 0.5 ≤ z ≤ 0.8

We quantify the galaxy environments around a sample of 0.5≤ z ≤0.8 radio-quiet quasars using the amplitude of the spatial galaxy–quasar correlation function, B _gq. The quasars exist in a wide variety of environments; some sources are located in clusters as rich as Abell class 1–2 clusters, whereas others exist in environments comparable to the field. We find that, on average, the quasars prefer poorer clusters of ≈Abell class 0, which suggests that quasars are biased tracers of mass compared with galaxies. The mean B _gq for the sample is found to be indistinguishable from the mean amplitude for a sample of radio-loud quasars matched in redshift and optical luminosity. These observations are consistent with recent studies of the hosts of radio-quiet quasars at low to intermediate redshifts, and suggest that the mechanism for the production of powerful radio jets in radio-loud quasars is controlled by processes deep within the active galactic nucleus itself, and is unrelated to the nature of the hosts or their environments.     

The Physics of Spectral Maxima in the Radiation from Non-Thermal Cosmic Radio Sources

Universal expressions are presented for spectral characteristics of non-thermal cosmic radio sources which show maxima of the spectral density of radiation at specific frequencies (negative slopes spectra). For a number of quasars, radio galaxies and their individual details the most probable physical processes in space leading to spectra of the kind are determined, and some parameters of the space medium, magnetic field and angular sizes of compact radio sources are estimated.     

A new quasar identified in the vicinity of NGC1068

An X-ray source close to the classical Seyfert galaxy NGC 1068 is identified as a quasar with a redshift of 0.63. The very high surface density of quasars around NGC 1068 suggests that the quasars may be physically associated with this active galaxy.     

在NGC1068附近发现的一个新的类星体

塞佛特星系ＮＧＣ1 0 6 8是一个非常令人注目的特殊天体 ,它是Ｓｅｙｆｅｒｔ[1]发现的第一批此类星系中离我们最近 (1 9Ｍｐｃ,取Ｈ0 =6 0ｋｍｓ- 1Ｍｐｃ- 1)和最亮的一个塞佛特星系 ,因此天文学家从射电到Ｘ 射线整个电磁波段对它进行了详尽的观测和研究。ＮＧＣ1 0 6 8最初被归类为塞佛特ＩＩ型天体 ,但是通过对其偏振光的光谱观测 ,发现了认为被遮挡住的塞佛特Ｉ型核发出的± 432 0ｋｍ/ｓ的宽Ｈβ发射线 ,因此被认为是活动星系核统一模型的一个范例 (见文 [2 ] )。射电与光学的观测资料都表明ＮＧＣ1 0 6 8的中心部分有激烈的喷射活动…     

Modification of the 21-cm power spectrum by quasars during the epoch of reionization

We assess the effect of a population of high-redshift quasars on the 21-cm power spectrum during the epoch of reionization. Our approach is to implement a seminumerical scheme to calculate the three-dimensional structure of ionized regions surrounding massive haloes at high redshift. We include the ionizing influence of luminous quasars by populating a simulated overdensity field with quasars using a Monte Carlo Markov Chain algorithm. We find that quasars modify both the amplitude and shape of the power spectrum at a level which is of the same order as the fractional contribution to reionization. The modification is found both at constant redshift and at constant global neutral fraction, and arises because ionizing photons produced by quasars are biased relative to the density field at a level that is higher than stellar ionizing photons. The modification of the power spectrum is likely to be small, rendering the effect of quasars difficult to isolate. However, we find the modification of the power spectrum by quasars to be at a level that is comparable to the precision expected for future low-frequency telescopes. Correct interpretation of observations will therefore require the effect of quasars to be considered, and our results imply that quasar ionization will need to be included in detailed modelling of observed 21-cm power spectra.     

The prevalence of Fanaroff–Riley type I radio quasars

We present deep, multi-Very Large Array configuration radio images for a set of 18 quasars, having redshifts between 0.36 and 2.5, from the 7C quasar survey. Approximately one quarter of these quasars have Fanaroff–Riley type I (FR I) type twin-jet structures and the remainder are a broad range of wide angle tail, fat double, classical double, core-jet and hybrid sources. These images demonstrate that FR I quasars are prevalent in the Universe, rather than non-existent as had been suggested in the literature prior to the serendipitous discovery of the first FR I quasar a few years ago, the optically powerful 'radio-quiet' quasar E 1821+643.
Some of the FR I quasars have radio luminosities exceeding the traditional FR I/FR II break luminosity; however, we find no evidence for FR II quasars with luminosities significantly below the break. We consider whether the existence of such high-luminosity FR I structures is due to the increasingly inhomogeneous environments in the higher redshift Universe.     

X-ray Observations of NGC 1097 and Nearby Quasars

Observations of three different sized regions centered on the optical jet spiral, NGC 1097 have been made with ROSAT. The PSPC observations show a striking excess of bright and medium flux X-ray sources around this hot spot nucleus, Seyfert 1 galaxy. The brightest of these sources are catalogued quasars which suggests the fainter X-ray sources are predominantly quasars also. If so, of the order of at least 10 and possibly considerably more X-ray quasars appear to be associated with NGC 1097 within a radius of 20. There is a marked segregation, with bright X-ray sources on the side of the bright optical jets and weak X-ray sources on the side of the fainter optical jets. Some, but not all, of this asymmetry could be accounted for by absorption in the plane of the spiral being tilted towards us on the weak source side. Both optical and X-ray evidence point to strong absorption in the disk of NGC 1097 which reaches far beyond the optical limits. High resolution imaging (HRI) of regions closer to NGC 1097 reveal some fainter pairs and lines of X-ray sources aligned across the nucleus near the cones defined by the optical jets. Filaments and patches of ultraviolet emission (1500–1700Å) appear to fill in the region between the strong optical jets in the direction of the bright X-ray quasars, suggesting physical association of the ultraviolet emission with the quasars and the galaxy. Finally, ROSAT SURVEY observations have been examined over a 4 × 4 degree field centered on NGC 1097. A line of X-ray sources going through the galaxy in the direction of the strongest optical jet includes a strong X-ray quasar with its X-ray isophotes extended toward NGC 1097. In approximately the opposite direction, 1.9 degrees distant, is a strong X-ray source (.5cts s^-1) which is here identified with a 16.5 mag BL Lac object.     

Radio Luminosity, Black Hole Mass and Eddington Ratio for Quasars from the Sloan Digital Sky Survey

We investigate the MBH-O'.relation for radio-loud quasars with redshift z＜0.83 in Data Release 3 of the Sloan Digital Sky Survey (SDSS).The sample consists of 3772 quasars with better models of the H/~ and [O III] lines and available radio luminosity,including 306 radio-loud quasars,3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity (181 radio-quiet quasars with measured radio luminosity).The virial supermassive black hole mass (MBH) is calculated from the broad H/line,and the host stellar velocity dispersion (σ*) is traced by the core [O III] gaseous velocity dispersion.The radio luminosity and radio loudness are derived from the FIRST catalog.Our results are as follows:(1) For radio-quiet quasars,we confirm that there is no obvious deviation from the MBH-O".relation defined for inactive galaxies when the uncertainties in MBH and the luminosity bias are concerned.(2) We find that the radio-loud quasars deviate more from the MBH-σ.relation than do the radio-quiet quasars.This deviation is only partly due to a possible cosmological evolution of the MBH-σ* relation and the luminosity bias.(3) The radioluminosity is proportional to M128 0.23-0.16 BH(LBol/LEdd)1.29 0.31-0.24 for radio-quiet quasars and to M3.10 0.6.-0.70(LBol.LEdd)4.18 1.40-1.10 for radio-loud quasars.The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities,such as the spin of the black hole.     

The jet power extracted from a magnetized accretion disc

We consider the power of a relativistic jet accelerated by the magnetic field of an accretion disc. It is found that the power extracted from the disc is mainly determined by the field strength and configuration of the field far from the disc. Comparing it with the power extracted from a rotating black hole, we find that the jet power extracted from a disc can dominate over that from the rotating black hole. However, in some cases, the jet power extracted from a rapidly rotating hole can be more important than that from the disc, even if the poloidal field threading the hole is not significantly larger than that threading the inner edge of the disc. The results imply that the radio-loudness of quasars may be governed by its accretion rate, which might be regulated by the central black hole mass. It is proposed that the different disc field generation mechanisms might be tested against observations of radio-loud quasars if their black hole masses are available.     

A Model of Quasars and AGNs with Magnetic Monopoles

An evolutionary model of quasars and AGNs with magnetic monopoles is proposed. Their energy source is due to nucleon decay induced by the monopoles. Both the mass and the luminosity of quasars and AGNs will gradually decrease in time because their constituent baryons are kept decaying and are transformed into radiation. The physical significance and theoretical predictions of our evolutionary model are stressed.     

The large-scale distribution of quasars identified with strong radio sources at 5 GHz

The large-scale angular distribution of quasars from a complete sample of extragalactic radio sources is examined at different redshifts. The sample contains 264 quasars which have been found so far among the complete sample of 518 radio sources stronger than. 1 Jy at 5 GHz. Of these, 19 quasars have redshift z > 2. Dividing the entire sky into three separate declination zones of equal area, the counts of quasars seem to indicate a deficit of high redshift quasars in the northernmost declination zone. On the other hand, the Iow-redshift quasars (z < 1) appear fairly uniformly distributed. We discuss some possible selection effects that might have led to the apparent anomaly at high redshifts and estimate the expected number of high-redshift quasars amongst the radio sources in the sample for which redshifts are presently not available.     

Far-infrared-loud quasars – I. Disturbed and quiescent quasars in the PG survey

We use host galaxy imaging studies of the PG quasar survey to compare the far-infrared (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 homogeneous data set, have a 60-μm luminosity distribution that is different from that of those with undisturbed hosts with >97 per cent confidence. For morphological classifications using an inhomogeneous data set, including HST data for some objects, this confidence rises to >99 per cent confidence. The mean 60-μm luminosity of the disturbed-host quasars is several times greater than that of the undisturbed-host quasars. However, possible biases in the PG survey might affect these conclusions. Our results are interpreted as supporting the idea that quasars are related to at least some ultraluminous infrared galaxies. We discuss the implications of this result for studies of quasar and galaxy evolution.     

Extending the Eigenvector 1 space to the optical variability of quasars

We introduce a new physical parameter, the optical variability amplitude, to the well-established Eigenvector 1 space of quasars and test a sample of long-term B-band light curves of 42 Palomar-Green quasars monitored by Giveon et al. We find that the optical variability amplitude strongly correlates with the intensity ratio of Fell to Hβ,Hβwidth and peak luminosity at 5007A. We briefly discuss the physical meaning of our findings and suggest that the Eddington ratio may be a key factor in determining a quasar's variability.     

Faster-than-light motion in quasars

Over the past fifteen years, observations of some quasars with the techniques of very-long-baseline interferometry have shown that the angular separation between pairs of radio-emitting regions in their cores is increasing year after year. If the quasars are indeed as far away as implied by Hubble’s law, then these angular motions translate into linear speeds several times the speed of light. Several theoretical scenarios have been proposed to show that the observed motions are illusory. The leading contender in this field — the relativistic beam model — and an alternative offered by the concept of a gravitational screen are described and compared in the light of recent observational data.     

类星体吸收线红移的研究

在此工作中,分析了一个类星体样本的吸收线红移和发射线红移之间的关系。结果表明这两类红移之间存在显著的相关。主要结论:a)反常吸收线红移的主要部分是宇宙学红移;b)吸收体相对于类星体的运动是弱的;c)结果表明产生这些反常吸收线红移的吸收体位于类星体寄主星系或者类星体内部并且朝着类星体运动。     

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.     

On the hypothesis of ejection of supermassive black holes from centers of galaxies and its application to quasar-galyxy associations

It is argued that accreting supermassive black holes ejected from centers of galaxies are the likely models for the quasars observed in association with galaxies. Also pointed out are the implications of a recent suggestion by Horák (1982) to account for the excess redshifts of such quasars due to a combined effect of peculiar Doppler-motion and the gravitational field.     

Further observations of quasars in ESO/SERC field 927

We present the spectra and redshifts of 62 quasars, from observations made with the Cerro Tololo Inter-American Observatory (CTIO) 4-m Blanco Telescope. These quasars form part of a total sample of 118 (with 56 having been published previously), which is being used for analysis of structure in the early universe. Quasars of particular interest are noted, including eight broad absorption line (BAL) quasars and two quasars with unusual emission spectra. Finally, we include a short summary of the present status of the large quasar group (LQG) that was discovered by Clowes & Campusano from the earlier observations. The quasars are from an area ∼25.3 deg² of ESO/SERC field 927, which is centred at (1950) 10^h40^m00^s, 05°00'00'.