High-luminosity Sources Research Articles

Galaxy identifications in the ROSAT All-Sky Survey

In a correlation study of the ROSAT All-Sky Survey Bright Source Catalogue (RASS-BSC) with the Catalogue of Principal Galaxies (PGC) 904 X-ray sources were found that possess possible extragalactic counterparts within a search radius of 100 arcsec. A visual screening process was applied to classify the reliability of the correlations. 547 correlations have been quoted as reliable identifications. From these, 349 sources are known as active galaxies. Although for the other sources no hints for activity were found in the literature, 69% of those for which we have distances show X-ray luminosities exceeding those of normal galaxies, a clear sign that these galaxies also own hitherto unreported X-ray active components. Some objects are located inside or in the direction of a known group or cluster of galaxies. Their X-ray flux may therefore be in part affected by hot gas emission. Luminosity and $\log N{-}\log S$ distributions are used to characterize different subsamples. Nuclei that are both optically and X-ray active are found predominantly in spirals. Two special source samples are defined, one with candidates for X-ray emission from hitherto unknown groups or clusters of galaxies, and one with high X-ray luminosity sources, that are likely candidates to possess hitherto unreported active galactic nuclei. Besides a compilation of X-ray and optical parameters, also X-ray overlays on optical images for all the objects are supplied as part of this work.

AnRXTESurvey of Long‐Term X‐Ray Variability in Seyfert 1 Galaxies

Data from the first three years of RXTE observations have been systematically analyzed to yield a set of 300 day, 2-10 keV light curves with similarly uniform, ~5 day sampling, for a total of nine Seyfert 1 galaxies. This is the first X-ray variability survey to consistently probe time scales longer than a few days in a large number of AGN. Comparison with ASCA data covering a similar band but much shorter (~1 day) time scales shows that all the AGN are more strongly variable on long time scales than on short time scales. This increase is greatest for the highest-luminosity sources. The well-known anticorrelation between source luminosity and variability amplitude is both stronger and shallower in power-law slope when measured on long time scales. This is consistent with a picture in which the X-ray variability of Seyfert 1s can be can be described by a single, universal fluctuation power density shape for which the cutoff moves to longer time scales for higher luminosity sources. All of the Seyfert 1s exhibit stronger variability in the relatively soft 2-4 keV band than in the harder 7-10 keV band. This effect is much too pronounced to be explained by simple models based on either the dilution of the power-law continuum by the Compton reflection component or on the hard X-rays being produced in a static, pair-dominated, plane-parallel Comptonizing corona.

PDS 456: an extreme accretion rate quasar?

We present quasi-simultaneous ASCA and RXTE observations of the most luminous known AGN in the local (z<0.3) Universe, the recently discovered quasar PDS 456. Multiwavelength observations have been conducted which show that PDS 456 has a bolometric luminosity of 10^47 erg/s peaking in the UV part of the spectrum. In the X-ray band the 2-10 keV (rest-frame) luminosity is 10^45 erg/s. The broad-band X-ray spectrum obtained with ASCA and RXTE contains considerable complexity. The most striking feature observed is a very deep, ionised iron K edge, observed at 8.7 keV in the quasar rest-frame. We find that these features are consistent with reprocessing from highly ionised matter, probably the inner accretion disk. PDS 456 appeared to show a strong (factor of 2.1) outburst in just 17ksec, although non-intrinsic sources cannot be completely ruled out. If confirmed, this would be an unusual event for such a high-luminosity source, with the light-crossing-time corresponding to 2 Schwarzschild radii. The implication would be that flaring occurs within the very central regions, or else that PDS 456 is a `super-Eddington' or relativistically beamed system. Overall we conclude on the basis of the extreme blue/UV luminosity, the rapid X-ray variability and from the imprint of highly ionised material on the X-ray spectrum, that PDS 456 is a quasar with an unusually high accretion rate.

On the cosmological evolution of the FR II radio source population

We present an analytical model for the cosmological evolution of the FRII source population. Based on an earlier model for the intrinsic radio luminosity - linear size evolution of these objects, we construct theoretical source samples. The source distributions in the radio power - linear size plane of these samples are then compared with that of an observed flux-limited sample. We find that the source parameters determining the radio luminosity of FRII objects can not be independent of each other. The best-fitting models predict the jet power to be correlated either with the life time of the source or with the shape of the density distribution of the source environment. The latter case is consistent with the observed tendency of the most luminous radio sources at high redshift to be located in richer and more extended environments than their low redshift counterparts. We also find evidence for a class of FRII sources distinctly different from the main population. These sources are extremely old and/or are located in very underdense environments. The luminosity function of FRII sources resulting from the model is in good agreement with previous results for high luminosity sources. The apparent luminosity evolution of the radio luminosity function is not reproduced because of the high flux limit of the used comparison sample. The cosmological evolution of the median linear size of FRII sources is found to be mild.

Temporal and spectral variability of AGN with RXTE

We present RXTE PCA observations of temporal and spectral variability of the four X-ray bright Seyfert galaxies NGC 4051, NGC 5506, NGC 5548 and MGC-6-30-15 covering a period of 18 months from February 1996. We find evidence of a knee in the long timescale power spectrum of NGC 4051 at a frequency of 5×10 −5 Hz. There is possible evidence of a knee at a slightly lower frequency in the higher luminosity source MCG-6-30-15 but no knees have been found in the still higher luminosity sources NGC 5506 and NGC 5548. If the knee frequency scales inversely with the central black hole mass then, by comparison with galactic black hole X-ray binaries, we deduce a mass of approximately 10 5 M ⊙ in NGC 4051. Strong continuum reflection components and iron fluorescent lines are seen in all four galaxies and we find evidence of strong X-ray spectral variability in all four galaxies. Here we discuss the spectra of NGC 5506 and MCG-6-30-15 as NGC 4051 is discussed elsewhere in these proceedings [1] and a possibly confusing BL Lac lies within the PCA field of view of NGC 5548. In both NGC 5506 and MCG-6-30-15 we find strong evidence for a steeping of the continuum spectral slope as the intensity increases. In MCG-6-30-15 the iron line flux increases only weakly as the continuum flux rises and, indeed, the iron line flux is consistent with being constant. In NGC 5506, however, there is an approximately linear relationship between the iron line flux and continuum flux with only weak evidence for an additional steady component. One explanation, although by no means confirmed, of the spectral index variability and relative quiescence of the iron line flux is that, in addition to rapidly varying steep spectrum continuum emission, there is also a harder reflected component from the surrounding torus. The torus component would not vary on the timescales of our observations and would dominates at very low flux levels. The difference between the variability of NGC 5506 and MCG-6-30-15 may be a lesser contribution from the torus in NGC 5506.

On the Dependence of the Iron K-Line Profiles with Luminosity in Active Galactic Nuclei

We present evidence for changes in the strength and profile of the iron Kα line in active galactic nuclei (AGNs), based on X-ray observations with ASCA. There is a clear decrease in the strength of the line with increasing luminosity. This relation is not due solely to radio power, as it persists when only radio-quiet AGNs are considered and therefore cannot be fully explained by relativistic beaming. In addition to the change in strength, the line profile also appears to be different in higher luminosity sources. We discuss these results in terms of a model where the accretion disk becomes ionized as a function of the accretion rate.

X‐Ray Properties of the NGC 1961 Group of Galaxies

We present an analysis of the ROSAT observations of the massive spiral galaxy NGC 1961 and surrounding small group of spiral galaxies. Contrary to the earlier Einstein observation which suggested that the X-ray emission comes mainly from an arc-shaped region on one side of NGC 1961, the ROSAT observations show that the X-ray emission is fairly typical for a spiral galaxy and comes mainly from the starburst nucleus with some contribution from the surrounding spiral arm regions. The total X-ray flux of 5.1 × 1040 ergs s-1 is normal, but the spectrum has an unusually narrow peak at 0.9 keV that can only be fit by models that have high absorption and low characteristic temperatures. A nearby bright X-ray source (LX = 1.7 × 1040 ergs s-1) at a projected distance of 44 kpc from NGC 1961 has no optical or radio counterpart and may be an example of the rare high-luminosity X-ray sources seen in a few other galaxies. There is no detectable diffuse X-ray emission in this group of spiral galaxies, but this is not unexpected because recent statistical studies show that groups with a hot intragroup medium (IGM) tend to have a higher velocity dispersion and contain a large fraction of elliptical and S0 galaxies. If there is a substantial IGM in this group, as is suggested by the head-tail distribution of H I gas around NGC 1961, then it must be cooler than ≈ 0.3 keV and thus invisible to the ROSAT detectors.

Bipolar Molecular Outflows in Massive Star Formation Regions

Bipolar molecular outflows are a basic component of the star formation process. This is true for stars of all masses, although it has not yet been well established how outflows associated with massive stars differ from those associated with low-mass stars. We present results from a project to identify bipolar outflows from massive young stellar objects (YSOs) and determine how they compare with low-mass YSO systems. Ten massive star formation regions with high-velocity 12CO(J = 1 − 0) line wings were mapped with the Kitt Peak 12 m telescope using the On-the-Fly (OTF) mapping technique. Five of the regions have bipolar outflows. We determine accurate mass estimates of the molecular gas in the red-and blueshifted lobes by taking into account variations in the optical depth as a function of velocity in the flow. We find that the molecular outflows have masses between ~16 and 72 M☉ and kinetic energies between ~1045 and 1046 ergs. The outflows have significantly more mass and kinetic energy than those from low-mass YSOs. Of the remaining five regions, two have a clumpy distribution in 12CO with multiple velocity components within the cloud complex, and three sources did not have sufficient signal-to-noise ratio (S/N) to map the high-velocity line wings. We combine our data with 18 additional outflow sources with stellar luminosities that range from 0.6 L☉ to 2.1 × 105 L☉ to predict the luminosity of the star responsible for the outflow. We find that the stellar luminosities of the sources in our sample range from ~102 to 104 L☉, which correspond to mid- to early-B type stars; the precursors of Herbig Be stars. One source, G173.58, has an IRAS source on the flow axis with the appropriate luminosity to drive the observed outflow. For the remaining four sources, there is no detectable ultracompact (UC) H ii region or isolated IRAS source with the appropriate luminosity to produce the observed molecular outflow. The outflows mapped in this work begin to fill in a region of outflow parameter space in which relatively few sources have been studied, and they help to bridge the gap between low-luminosity outflow sources and the few isolated outflows from massive O stars. Our data are consistent with the ideas that (1) in a molecular outflow increases continuously with Lbol of the driving source over a range from ~1 L☉ to ~106 L☉ (2) one can predict the central source luminosity from the measured mass flux in the flow, (3) there is a clear Mflow versus age (td) relationship for stars of all luminosities, and (4) the larger for higher luminosity sources implies that these objects produce massive outflows on short timescales relative to low-mass stars.

Increase of the atomic phase density in a hollow laser waveguide

A study is made of the channeling of atoms in a narrowing hollow waveguide carrying on its inner surface a surface wave with positive detuning for the absorption line of an atom. The inelastic reflection of atoms from the surface light wave and the convergent geometry of the waveguide make it possible to decrease the temperature and increase the phase density of an ensemble of atoms introduced continuously into the hollow convergent waveguide from a magnetooptic trap, by a factor of 105. It is suggested that such a waveguide be used to study collective phenomena in quantum-mechanical systems with a high density (Bose-Einstein condensate) and as a high-luminosity coherent source of cold atoms.

Large-Scale Structure: Jets on kiloparsec Scales

This paper examines some of the consequences of the hypothesis that jets in all radio galaxies and quasars are relativistic on small scales, in the sense that the flow velocity &gt;0.5c. This idea is suggested by a number of lines of evidence. Firstly, Unified Models (Urry &amp; Padovani, 1995) imply that the relativistic motion required in core-dominated objects must also occur in a larger parent population consisting of most, if not all, extended sources. Secondly, superluminal motion is detected in the nuclei of extended sources and in the kpc-scale jet of M 87 (Hough, 1994; Biretta, Zhou &amp; Owen, 1995). Thirdly, jets are one-sided in the same sense on pc and kpc scales; at all luminosities, the radio emission tends to become more symmetrical on larger scales, as expected if an initially relativistic flow decelerates (Bridle &amp; Perley, 1984; Bridle et al., 1994a; Parma et al., 1994). Finally, depolarization asymmetry occurs in both low (Parma, de Ruiter &amp; Fanti, 1996) and high (Laing, 1988; Garrington et al., 1988) luminosity sources: the implication is that the brighter jet is on the near side of the source. It is likely that the key difference between radio sources in the two morphological classes defined by Fanaroff &amp; Riley (1974) are that relativistic flow persists to the extremities of FRII sources, but that FRI jets decelerate smoothly on intermediate scales (Laing, 1993; Bicknell, 1995). On kiloparsec scales, we can identify structures which we propose should be called fast jets. These are well-collimated and generally one-sided (in the sense that the jet/counterjet ratio &gt;4:1). They also have longitudinal apparent magnetic field (B||). They occur both in FRII sources, and at the bases of FRI jets (Bridle &amp; Perley, 1984). We suggest that they are relativistic flows, and that this fact is crucial to an understanding of their evolution. A framework for the understanding of the variety of extended structures in extragalactic radio sources in this context is illustrated in Figure 1, which is an improved version of the diagram presented by Laing (1993). A fast jet appears to be able to: decelerate and recollimate to form a slow jet with β &lt;&lt; 1 (therefore two-sided unless external effects dominate); disrupt, as in wide-angle tail sources, or hit the external medium and form a hot-spot. Slow jets are probably formed only when a decelerating fast jet can be recollimated by the external pressure gradient (Phinney, 1983; Bowman, Leahy &amp; Komissarov, 1995). This may not be possible for more powerful sources in flatter pressure gradients and it is likely that wide-angle tail sources are formed when a fast jet decelerates rapidly but cannot recollimate. Deceleration by entrainment is efficient when the jet is transonic, and Bicknell (1994) showed that this corresponds to β ≈0.3 − 0.7 for a relativistic jet. If the jet does not slow down sufficiently (e.g. by mass loading; Komissarov 1994), then the flow will remain supersonic until it impacts on the external medium, and an FRII source will result. The radio morphology is therefore determined by a combination of initial jet speed and thrust and the effects of the environment, via the rate of stellar mass loss and the pressure gradient. On the largest scales, a bridge(backflow) or tail (outflow) will be formed. If the jet remains supersonic as far as the end of the lobe (as in an FRII source), then it is inevitable that a backflow (bridge) will be generated. As emphasised by Parma, de Ruiter &amp; Fanti (1996), the majority of FRI sources also show bridges: the residual momentum of the jets, their density contrast with the external medium and the external pressure gradient are all likely to be important in determining their large-scale morphologies.

UNIFIED SCHEMES FOR RADIO-LOUD ACTIVE GALACTIC NUCLEI

ABSTRACT The appearance of active galactic nuclei (AGN) depends so strongly on orientation that our current classification schemes are dominated by random pointing directions instead of more interesting physical properties. Light from the centers of many AGN is obscrued by optically thick circumstellar matter, particularly at optical and ultraviolet wavelengths. In radio-loud AGN, bipolar jets emanating from the nucleus emit radio through gamma-ray light that is relativistically beamed along the jet axes. Understanding the origin and magnitude of radiation anistropies in AGN allows us to unify different classes of AGN; that is, to identify each single, underlying AGN type that gives rise to different classes through different orientations. This review describes the unification of radio-loud AGN, which includes radio galaxies, quasars, and blazars. We describe the classification and general properties of AGN. We summarize the evidence for anisotropic emission caused by circumstellar obscuration and relativistic beaming. We outline the two most plausible unified schemes for radio-loud AGN, one linking the high-luminosity sources (BL Lac objects and less luminous radio galaxies). Using the formalism appropriate to samples biased by relativistic beaming, we show the population statistics for two schemes are in accordance with available data. We analyze the possible connections between low- and high-luminosity radio-loud AGN and conclude they probably are powered by similar physical processes, at least within the relativistic jet. We review potential difficulties with unification and conclude that none currently constitutes a serious problem. We discuss likely complications to unified schemes that are suggested by realistic physical considerations; these will be important to consider when more comprehensive data for larger complete samples become available. We conclude with a list of the ten questions we believe are the most pressing in this field.

Investigating beaming and orientation effects using a complete sample of radio sources

A homogeneous set of optical and radio data has recently been obtained for a complete, flux-limited sample of southern radio sources. Using Monte Carlo simulations, we investigate the log Pcore versus log Ptot correlation and the distribution of the observed parameters Ptot, z and R (the ratio of the core and the extended flux densities). The sample properties can be well reproduced if the beaming of the core is described by a mean Lorentz factor γ ∼ 3, but there is evidence, both from this work and from other arguments, that the low- and high-luminosity sources tend to have somewhat lower and higher values, respectively. While the use of a local radio luminosity function describes the general properties of the sample quite well, there is evidence for some luminosity evolution in the most distant objects (⁠|$0.5\lt z\lt0.7$|⁠).

Do relativistic electrons either gain or lose energy, outside of extragalactic nuclei?

In the generally accepted models of high-luminosity extragalactic radio sources, the relativistic electron distribution evolves significantly outside of its source in the galactic nucleus; synchrotron losses occur throughout the source, and the harder (flatter) spectra seen in the hot spots are one indicator of relativistic particle acceleration. Our reanalysis and interpretation of the Carilli et al. (1991) data on Cygnus A, on the other hand, showed no evidence for evolution of the electron distribution function, and no evidence of the universally assumed injection power-law distribution. Having found a spectrum that describes an entire source, we have also introduced the technique of correcting synchrotron maps for frequency-dependent effects. In this way, a partial deconvolution of the underlying physical parameters is possible. In Cygnus A, this correction procedure led to the dominance of a hitherto unrecognized structure, an edge-brightened channel girdled by rings. We briefly discuss some implications of this work and our plans to continue this line of investigation. Subject headings: acceleration of particles — galaxies: individual (Cygnus A) — galaxies: nuclei — radiation mechanisms: nonthermal — radio continuum: galaxies

Dynamical and radiative effects of ultrarelativistic hadronic interactions in active galactic nuclei

We estimate the energies of the outflowing nucleons from the central regions of active galactic nuclei and found significant asymmetries in the nucleon energy output on both sides of the antiparallel axes of the high-luminosity radio source sample analyzed. The nucleon energy output is found to be consistently higher on the counterjet side than on the jet side for all the sources in this sample. We propose that relativistic neutron decay is a plausible mechanism for the production of radio synchrotron electrons in situ, and that large-scale radio jets result as a consequence of the dynamical and radiative signatures of the escaping relativistic neutrons

Infrared dust and millimeter-wave carbon monoxide emission in the Orion region

The far-infrared dust emission seen by the IRAS satellite in the Orion region is analyzed as a function of the local radiation field intensity, and the dust temperature and opacity are compared with (C-12)O and (C-13)O emission. The infrared radiation is interpreted within the framework of a single-component large grain model and a multicomponent grain model consisting of subpopulations of grains with size-dependent temperatures. A strong dependence of the 100-micron optical depth derived is found using the large grain model on the average line-of-sight dust temperature and radiation field. In the hot environment surrounding high-luminosity sources and H II regions, all dust along the line-of-sight radiates at 100 microns, and the dust-to-gas ratio, based on the 100-micron opacity and I(/C-13/O), appears to be in agreement with the standard value, about 1 percent by mass. A relationship is found between the inferred dust-to-gas ratio and the radiation field intensity responsible for heating the dust which can be used to estimate the gas column density from the dust opacity derived from the 60- and 100-micron IRAS fluxes.

An X-ray and radio study of steep-spectrum radio sources. II - Four fields from a 22 MHz polar CAP survey

Four fields containing radio sources with spectral indices greater than unity at low frequencies have been observed over a wide range of radio wavelengths and at X-ray wavelengths. For most of the steep-spectrum sources no optical identifications have been found to the detection limit of the Palomar Schmidt prints, even with the positional precision of about 1 arcsec from VLA maps. This implies that the associated galaxies or clusters lie at a great distance. X-ray emission was not detected from any of the steep-spectrum radio sources. In one case, an extended source appears to be a radio halo in an uncataloged cluster of galaxies at a redshift of 0.125, and it is suggested that this object is a promising candidate for the detection of inverse Compton X-rays, since it is not a high-luminosity source of thermal X-rays.

The identity and position of X-ray sources in globular clusters: radio emission from NGC6712

NINE globular clusters are known to contain luminous (Lx> 1036 erg s−1) X-ray sources, but because the X-ray position error boxes, a few arcseconds in size, contain many stars, optical iden-tification of the sources has not been possible, with the exception of that in NGC7078 (ref. 19). This has prevented detailed investiga-tion of the emitting objects. If the X-ray sources are similar to low-mass X-ray binaries (LMXBs) outside globular clusters, low-level radio emission would be expected1,2, and the detection of such radio emission would both strengthen the case that luminous globular cluster X-ray sources are LMXBs and aid optical iden-tification by means of an accurate radio position. We report here the detection of radio emission from the position of the luminous X-ray source A1850–08 (ref. 3) in the globular cluster NGC6712. The centroid of the slightly elongated radio source coincides with a previously suggested 20th magnitude stellar optical counterpart4. If the radio emission is synchrotron radiation, the minimum energy requirement and magnetic field strength are similar to what is found in the radio counterparts to other high-luminosity X-ray sources such as Sco X-l and Cyg X-3.

The X-ray spectrum of the broad-line radio galaxy 3C445

The first X-ray spectrum of the giant radio galaxy 3C445 is reported. The spectrum is well fitted by a power law of slope close to the ‘canonical’ value for emission-line galaxies. This suggests that the X-ray emission of 3C445 is dominated by its Seyfert nucleus and is not directly related to the radio flux, a conclusion supported by the large low-energy absorption evident from the X-ray spectrum. The implied intrinsic absorbing column of |$\thicksim 1.7 \times {10}^{23}\,{\text{cm}}^{-2}$| is the largest ever seen for such a high-luminosity source as 3C445 |$({L}_{2-10} \thicksim 3.3 \times {10}^{44}\,\text{egr}\, {\text{s}}^{-1})$|⁠.

The EXOSAT spectral survey of AGN

Results are presented from EXOSAT observations of 48 hard X-ray selected Seyfert type active galactic nuclei (AGN). These include all 30 of the emission line AGN in the Piccinotti sample. Combining EXOSAT LE and ME data has allowed us to obtain X-ray spectra over the broad energy range 0.1 – 10 keV. Spectra in the |$\sim2-10$| keV range are found to be well described by a simple power law, with a narrow distribution of spectral indices across the sample about a mean energy index α = 0.70. EXOSAT has also revealed a substantial number of sources with complex soft X-ray spectra. These include spectra with a second emission component at soft X-ray energies as well as sources with ‘leaky’ absorbing columns. Evidence that soft emission components occur in many Seyferts, together with detection of rapid variability in the soft component, provides quantitative support for an accretion disc model for AGN. Approximately half our sample of AGN show low-energy absorption attributable to substantial cold matter within the host galaxy. A few cases show evidence for column variability and reduced low-energy opacity (by photo-ionization). These results and the observed rarity of intrinsic absorption in the higher luminosity sources suggest the absorbing matter lies close to the central continuum source.

Radio properties of the highly polarized, quiescent quasar OI 287

view Abstract Citations (13) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Properties of the Highly Polarized, Quiescent Quasar OI 287 Ulvestad, James S. ; Antonucci, Robert R. J. Abstract OI 287 has often been considered to be a blazar because of its high optical polarization. However, it is the only high-polarization quasar with constant optical flux and polarization as well as a lobe-dominant radio source. All known blazars have cores with smooth convex spectra from radio to optical wavelengths, which is taken to indicate the presence of a single synchrotron source for this entire range. The high-resolution 6 cm and 2 cm VLA data described in this paper show that this cannot be the case for OI 287, so that it cannot be considered to be a blazar. Previous moderate-resolution radio mapping showed apparent twin jets with parallel magnetic fields in this high-luminosity source, whereas most high-luminosity sources have one-sided jets. The higher resolution data show that the jets are better described as bridges; therefore the morphology is not particularly unusual for high-luminosity, lobe-dominant sources. The radio core polarization of OI 287 is less than 0.25% at 6 cm, low in comparison to blazars. Both the radio polarization and the other radio/infrared properties are normal for lobe-dominant quasars. Therefore, the optical polarization may not arise from synchrotron radiation as it does in blazars. This is consistent with the idea of Miller and Goodrich in which an edge-on geometrically thin disk blocks our direct view of the continuum and broad-line regions. In that picture, the high optical polarization would arise because only scattered photons reach the observer. Alternatively, it is still possible that OI 287 is related to the broad absorption line quasars, several of which are significantly polarized. Publication: The Astrophysical Journal Pub Date: May 1988 DOI: 10.1086/166314 Bibcode: 1988ApJ...328..569U Keywords: Bl Lacertae Objects; Optical Polarization; Quasars; Radio Sources (Astronomy); Synchrotron Radiation; Blazars; Emission Spectra; High Resolution; Line Spectra; Morphology; Stellar Luminosity; Very Large Array (Vla); Astrophysics; BL LACERTAE OBJECTS; POLARIZATION; QUASARS full text sources ADS | data products SIMBAD (5) NED (5)