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1.
Despite a general consensus in the astronomical community that all quasars are located at the distances implied by their redshifts, a number of observations still challenge this interpretation, possibly indicating that some subpopulation of quasars may harbour significant redshift components not related to the expansion of the Universe. It has been suggested that these objects may have been ejected from local galaxies and are likely to evolve into new galaxies themselves. Here, a test of such exotic scenarios is proposed, based on the spectral energy distribution of the galaxies hosting quasars with suspected ejection origin. Provided that the time-scales over which the ejected objects manifest themselves as quasars is short, one would in the framework of the ejection scenarios expect to find either no quasar host galaxy, a pseudo-host consisting of gas ionized by the quasar, or a host galaxy consisting of young stars only. It is argued that the spectral energy distributions corresponding to the last two options should differ significantly from that of most quasar host galaxies detected at low redshift so far, thus providing a potential test of the claimed existence of ejected quasars. A minimal implementation of this test, involving optical and near-infrared broad-band photometry, is suggested.  相似文献   

2.
The possibility of interpreting a number of statistical results on the characteristics of quasars, which are not explained consistently from a single point of view, is considered. It is shown that these results can be explained fairly well if we assume that some quasars are ejected from neighboring galaxies, and their observed redshift consists of three components: cosmological, anomalous, and local ejection components. It is assumed that the anomalous component has a maximum value at the birth of a quasar and subsequently disappears due to its evolution. Translated from Astrofizika, Vol. 41, No. 2, pp. 217–226, April-June, 1998.  相似文献   

3.
The variable Mass Hypothesis of conformal gravitation theory of Hoyle-Narlikar is used to develop a model for the anomalous redshift quasar-galaxy associations. It is hypothesised that quasars are born in and ejected from the nuclei of parent galaxies as massless objects and the particle masses in them systematically increase with epoch. The dynamics of such an ejection is discussed and it is shown that the observed features such as redshift bunching and quasar alignments can be understood in this scenario. Further tests of this hypothesis are suggested.  相似文献   

4.
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.  相似文献   

5.
We present spectroscopic observations of a sample of faint gigahertz peaked‐spectrum (GPS) radio sources drawn from the Westerbork Northern Sky Survey (WENSS). Redshifts have been determined for 19 (40 per cent) of the objects. The optical spectra of the GPS sources identified with low‐redshift galaxies show deep stellar absorption features. This confirms previous suggestions that their optical light is not significantly contaminated by active galactic nucleus-related emission, but is dominated by a population of old (>9 Gyr) and metal-rich (>0.2 [Fe/H]) stars, justifying the use of these (probably) young radio sources as probes of galaxy evolution. The optical spectra of GPS sources identified with quasars are indistinguishable from those of flat-spectrum quasars, and clearly different from the spectra of compact steep‐spectrum (CSS) quasars. The redshift distribution of the GPS quasars in our radio-faint sample is comparable to that of the bright samples presented in the literature, peaking at z ∼2–3. It is unlikely that a significant population of low-redshift GPS quasars is missed as a result of selection effects in our sample. We therefore claim that there is a genuine difference between the redshift distributions of GPS galaxies and quasars, which, because it is present in both the radio-faint and bright samples, cannot be caused by a redshift–luminosity degeneracy. It is therefore unlikely that the GPS quasars and galaxies are unified by orientation, unless the quasar opening angle is a strong function of redshift. We suggest that the GPS quasars and galaxies are unrelated populations and just happen to have identical observed radio spectral properties, and hypothesize that GPS quasars are a subclass of flat-spectrum quasars.  相似文献   

6.
本文讨论了类星体成团随红移的变化。利用Hewitt-Burbidge类星体星表和寻找类星体对的统计方法,分析结果表明类星体成团主要是由于小红移类星体的贡献,大红移类星体没有成团分布的证据。进一步分析表明不同红移类星体在成团分布上的区别并不是由于样品的绝对光度不同而引起的选择效应,而是反映了类星体团随宇宙时间变化的演化效应。  相似文献   

7.
We report the first results of an observational programme designed to determine the luminosity density of high-redshift quasars     quasars) using deep multicolour CCD data. We report the discovery and spectra of three     high-redshift     quasars, including one with     . At     , this is the fourth highest redshift quasar currently published. Using these preliminary results we derive an estimate of the         quasar space density in the redshift range     of     . When completed, the survey will provide a firm constraint on the contribution to the ionizing UV background in the redshift range     from quasars by determining the faint-end slope of the quasar luminosity function. The survey uses imaging data taken with the 2.5-m Isaac Newton Telescope as part of the Public Isaac Newton Group Wide Field Survey (WFS). This initial sample of objects is taken from two fields of effective area ∼12.5 deg2 from the final ∼100 deg2.  相似文献   

8.
We use semi-analytic modelling on top of the Millennium simulation to study the joint formation of galaxies and their embedded supermassive black holes. Our goal is to test scenarios in which black hole accretion and quasar activity are triggered by galaxy mergers, and to constrain different models for the light curves associated with individual quasar events. In the present work, we focus on studying the spatial distribution of simulated quasars. At all luminosities, we find that the simulated quasar two-point correlation function is fit well by a single power law in the range  0.5 ≲ r ≲ 20  h −1 Mpc  , but its normalization is a strong function of redshift. When we select only quasars with luminosities within the range typically accessible by today's quasar surveys, their clustering strength depends only weakly on luminosity, in agreement with observations. This holds independently of the assumed light-curve model, since bright quasars are black holes accreting close to the Eddington limit, and are hosted by dark matter haloes with a narrow mass range of a few  1012  h −1 M⊙  . Therefore, the clustering of bright quasars cannot be used to disentangle light-curve models, but such a discrimination would become possible if the observational samples can be pushed to significantly fainter limits. Overall, our clustering results for the simulated quasar population agree rather well with observations, lending support to the conjecture that galaxy mergers could be the main physical process responsible for triggering black hole accretion and quasar activity.  相似文献   

9.
Based on the spectra of 4 high-redshift quasars (resolution 2A) obtained by us [1–5] using IPCS on the RGO Cassegrain spectrograph of the AAT, we point out the following. 1. Auto-correlation peaks at in PKS 0805+046 and PKS 1442+101 suggest that the large number of absorption lines shortward of Lα in high redshift quasars are due to absorption by hydrogen clouds. 2. The distribution of absorption lines and the correlation function of indicate that PKS 0528-250 may be an exception, requiring further observation. 3. Absorption redshift systems containing metallic lines may be produced by either matter ejected from the quasar, or an associated galaxy cluster or an intervening galaxy. 4. The randomness in the column density and the dispersion velocity deduced from the curve of growth of the pair supports the hypothesis that the pure Lα absorption comes from primitive hydrogen clouds in the early, exploding universe. 5. The number of hydrogen clouds per unit redshift interval is determined by the data of absorption lines of quasars with Z > 3.  相似文献   

10.
The chance that the pair of X-ray sources observed across NGC 4258 is accidental can be calculated as 5×10–6. The recent confirmation as quasars, and determination of the redshifts of the pair, atz=0.40 and 0.65 by E.M. Burbidge enables the final accidental probability of the configuration to be calculated as <4×10–7. In addition there are a number of observations which indicate the central Seyfert galaxy is ejecting material from its active nucleus.The NGC 4258 association is compared to four other examples of close association of pairs of X-ray quasars with low redshift galaxies. It is concluded that in each of these five cases the chance of accidental association is less than one in a million. The ejection speed calculated from the redshift differences of the X-ray quasars is 0.12c. This agrees with the ejection velocity of 0.1c calculated in 1968 from radio quasars associated with low redshift peaks become narrower—simultaneously strengthening the ejection origin for quasars and the quantization property of their redshift  相似文献   

11.
Using cosmological hydrodynamic simulations, we measure the mean transmitted flux in the Lyα forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel quasar separation distance can be fitted using a simple power-law form including the usual correlation function parameters r 0 and γ, so that     . From the simulations, we find the relation between r 0 and quasar host mass, and formulate this as a way to estimate quasar host dark matter halo masses, quantifying uncertainties due to cosmological and IGM parameters, and redshift errors. With this method, we examine data for ∼9000 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 5, assuming that the effect of ionizing radiation from quasars (the so-called transverse proximity effect) is unimportant (no evidence for it is seen in the data). We find that the best-fitting host halo mass for SDSS quasars with mean redshift z = 3 and absolute G -band magnitude −27.5 is  log  M /M⊙= 12.68+0.81−0.67  . We also use the Lyman-Break Galaxy (LBG) and Lyα forest data of Adelberger et al. in a similar fashion to constrain the halo mass of LBGs to be  log10  M /M⊙= 11.41+0.54−0.59  , a factor of ∼20 lower than the bright quasars. In addition, we study the redshift distortions of the Lyα forest around quasars, using the simulations. We use the quadrupole to monopole ratio of the quasar Lyα forest correlation function as a measure of the squashing effect. We find its dependence on halo mass difficult to measure, but find that it may be useful for constraining cosmic geometry.  相似文献   

12.
We examine a Doppler theory of quasars in which it is assumed that a fraction of the total population of quasars are fired from centres of explosion with moderate cosmological redshifts. It is argued that the substantial part of the redshift of a typical high redshift quasar could be of Doppler origin. If Hoyle’s recent hypothesis that quasars emit the bulk of their radiation in a narrow backward cone is given a quantitative form, it is shown that the kinematic and emission parameters of this model can explain the observed features of the four aligned triplets of quasars discovered by Arp and Hazard (1980) and by Saslaw (personal communication). The model predicts a small but nonzero fraction of quasars with blueshifts. Further observational tests of the model are discussed.  相似文献   

13.
分析类星体吸收线红移和发射线红移的特征。我们从Hewitt和Burbidge ( 1 993 )的星表中选择了吸收线红移和发射线红移都同时提供的类星体 ,得到了包含 4 0 1个对象的样本。这是至今对类星体红移研究的最大样本。我们从吸收线红移和发射线红移之间的关系图发现绝大多数 ( 93 .6% )对象的吸收线红移都小于相应的发射线红移。这个结论人们在 2 0世纪 70年代已经从很小的类星体样本 (样本大小 50左右 )中得到。本文进一步支持了这个结论。它表明类星体红移确实是距离的指示器。这跟宇宙学对类星体红移的解释是一致的  相似文献   

14.
Discrete Fourier analysis on the quasar number count, as a function of redshift, z, calculated from the Sloan Digital Sky Survey DR6 release appears to indicate that quasars have preferred periodic redshifts with redshift intervals of 0.258, 0.312, 0.44, 0.63, and 1.1. However the same periods are found in the mean of the zConf parameter used to flag the reliability of the spectroscopic measurements. It follows that these redshift periods must result from some selection effect, as yet undetermined. It does not signal any intrinsic (quantized) redshifts in the quasars in Sloan survey data. However this result does not rule out the possibility as found in earlier studies of other data.  相似文献   

15.
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.  相似文献   

16.
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.  相似文献   

17.
A New Approach for Studying Hubble Diagrams of Quasars   总被引：2，自引：0，他引：2  
In this paper, a new approach for studying Hubble diagrams of quasars is introduced. The purpose is to reduce the well-known very large scatter in the diagram. We believe that the scatter is mainly caused by the wide spread of luminosity distribution of quasars. Based on a large number of quasars having been discovered, we introduce a new quantity, the collective apparent magnitude of certain amount of quasars in a corresponding redshift interval, and make a plot of the collective apparent magnitude versus redshift with the data published by Hewitt and Burbidge (1993). The quantity is contributed by individual apparent luminosities as well as the luminosity distribution of quasars. Scatter is expected to be largely reduced in the corresponding diagram, and this is indeed true as shown by the figures. By discussing several possible effects and from the figures, we find that the assumption that redshifts of quasars are distance indicators is confirmed, and the standard cosmological model is supported. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

18.
Peaks at high redshifts in individual samples of quasars can be explained as due to selection effects. It is concluded that peaks in quasar redshift distribution do not obey any generalformula that can constitute a periodicity, even though individual samples may favour some redshifts of smaller values, viz. z < 1.  相似文献   

19.
We present the spectra, positions, and finding charts for 31 bright ( R <19.3) colour-selected quasars covering the redshift range z =3.85–4.78, with four having redshifts z >4.5. The majority are in the southern sky ( δ <−25°). The quasar candidates were selected for their red ( B J− R ≳2.5) colours from UK or POSSII Schmidt Plates scanned at the Automated Plate Measuring (APM) facility in Cambridge. Low-resolution (≳ 10 Å) spectra were obtained to identify the quasars, primarily at the Las Campanas Observatory. The highest redshift quasar in our survey is at z ≈4.8 ( R =18.7) and its spectrum shows a damped Ly α absorption system at z =4.46. This is currently the highest redshift damped Ly α absorber detected. Five of these quasars exhibit intrinsic broad absorption line features. Combined with the previously published results from the first part of the APM United Kingdom Schmidt Telescope (UKST) survey we have now surveyed a total of ∼8000 deg2 of sky i.e. 40 per cent of the high galactic latitude (| b |>30°) sky, resulting in 59 optically selected quasars in the redshift range 3.85 to 4.78; 49 of which have z ≥4.00.  相似文献   

20.
On the basis of Kang et al.’s semi-analytical model of galaxy formation and evolution, the joint formation and evolution of galaxies and their central massive black holes are studied. It is assumed that the activity of quasars is caused by merging of galaxies. Via the introduction of the mass accretion rate of black holes, the bolometric luminosity function of quasars with the redshifts in the region of 0 < z < 4.5 is ascertained. With the respective limitations of the three factors, i.e., the Eddington ratio, black-hole mass function and two-point correlation function, the luminosity function predicted by the model may coincide with observations in the entire range of luminosity. This result reveals that the constant Eddington ratio cannot well describe the accretion of black holes, so the Eddington ratio has to be increased with the redshift in a certain range of redshift. The major merging of galaxies is the effective mechanism of triggering the quasar activity, while the minor merging can merely affect the quasars with low and intermediate luminosities. Its effect on the high-luminosity quasars is very small. At the place of z=1, the quasars with extremely high luminosities possess more intense properties of clustering than other quasars.  相似文献   

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