Optical and radio properties of giant radio quasars: Central black hole characteristics

We analysed the optical and radio properties of lobe-dominated giant-sized (> 0.72 Mpc) radio quasars and compared the results with those derived for a sample of smaller radio sources to determine whether the large size of some extragalactic radio sources is related to the properties of their nuclei. We compiled the largest (to date) sample of giant radio quasars, including 24 new and 21 previously-known objects, and calculated a number of important parameters of their nuclei such as the black hole mass and the accretion rate. We conclude that giant radio quasars have properties similar to those of smaller size and that giant quasars do not have more powerful central engines than other radio quasars. The results obtained are consistent with evolutionary models of extragalactic radio sources which predict that giant radio quasars could be more evolved (aged) sources compared to smaller radio quasars. In addition we found out that the environment may play only a minor role in formation of large-scale radio structures.Comment: 19 pages, 17 figures, submitted to MNRA

J1145-0033 - the most distant giant radio source?

We present J1145-0033, a candidate for the most distant (z=2.055) lobe-dominated giant radio quasar, with a projected linear size of 1.34 Mpc. This quasar has both FR II -- type radio morphology and broad absorption lines in its optical spectrum. Some physical characteristics (e.g. black hole mass, accretion rate, equipartition magnetic field, energy density and particle density of ambient medium) based on the optical and radio data are provided. We have also found that the quasar has a relatively large central black hole mass and a very small accretion rate in comparison with similar objects.Comment: 12 pages, 4 Postscript figure

Optical and radio properties of extragalactic radio sources with recurrent jet activity

We present a sample of 74 radio sources with recurrent jet activity. The sample consists of 67 galaxies, 2 quasars and 5 unidentified sources, selected from the published data or are newly recognized. The sample's redshift range is 0.002 < z < 0.7 and the size of inner and outer structures varies from 0.02 to 4248 kpc. We analyse the optical and radio properties of the sample and compare them with the characteristics of ordinary one-off FRII radio sources. With the help of stellar population modelling, we derive black hole masses and stellar masses of host galaxies of 35 restarting radio sources, finding that the black hole masses in restarting radio sources are comparable to those of typical single-cycle FRII radio sources. The obtained median values of log M$_{BH}$ are 8.58 and 8.62 M$_{\odot}$ Unlike the black hole masses, the stellar masses in restarting radio sources tend to be smaller than in the FRII sources. Although the stellar populations of the hosts of recurrent activity sources are dominated by old stars, a significant fraction of young stars can be observed as well. Based on the Sloan Digital Sky Survey photometric observations, we also analyse the morphology of the host galaxies and obtained significantly smaller concentration indices for the restarting radio sources when compared to the classical FRII hosts. This effect can be interpreted as a result of frequent merger events in the history of host galaxies of restarting radio sources.Comment: 21 pages, 17 figure

Benchmarking in university development towards a learning organization

Background. Universities possess an inherent imperative of self-improvement derived from their mission and they act as a source, transformer and propagator of learning and knowledge. Therefore incorporating a learning organisation concept in higher education institutions (HEIs) seems natural. Research aims. A lack of clear and explicit practical hints on how to incorporate the concept into a university was identified as a cognitive gap in the literature. The key research aim of the paper was to analyse the concept of a learning organisation in the context of HEIs, present conditions facilitating implementation of the concept in HEIs and indicate how systematic usage of benchmarking can help HEIs to become learning organisations. Method. In the paper an in-depth study and critical analysis of literature on learning organisation in the context of HEIs was performed. The author points to benchmarking as a tool enhancing the impact of the learning organisation concept. In the study a set of recommendations for HEIs aiming at becoming a learning organisation was developed. Key Findings. In the paper the thesis that systematic usage of benchmarking helps a university  to become a learning organisation was stated and supported. Benchmarking comprises interorganisational learning. It involves descriptive learning about competition and  the environment of the organisation. Universities willing to become learning organisations should develop a climate of creativity and lateral thinking which enhances learning in the process of benchmarking

Central black holes in giant radio quasars

We analysed optical properties of giant radio quasars (with radio structures larger than 0.7 Mpc). To this day it is unclear why only a small fraction of radio sources attain such large sizes. There are a number of hypotheses attempting to explain this phenomenon, however the one treated in this paper has not yet been investigated in detail. This hypothesis assumes that the giant linear sizes of radio structures are due to internal properties of their central active galactic nuclei i. e. the specific properties of super-massive black holes and/or their accretion discs. We investigated whether a direct relation exists between the properties of the central "engine" and the origin of the Mpc scale radio structures. In our analysis, we did not find any relation between black hole mass and radio core power, however, we found a weak correlation between the accretion rate and radio core power. We also found a relation between a black hole's mass and linear size of the radio structure. The obtained results may suggest that giant radio quasars are similar to those of smaller size. There are also indications that giant radio quasars may be more evolved sources as compared with smaller radio quasars

Interstellar spectral features and telluric absorption lines

In good quality spectra of stars the weak interstellar absorption lines may be substantially contaminated by telluric lines. Many telluric lines may also simulate interstellar absorptions. To avoid undesirable telluric effects during searches for interstellar absorptions, especially for diffuse interstellar bands (DIBs), we looked for all accessible catalogued telluric absorption lines in our spectra which contain DIBs. We investigated the echelle spectra of two stars, oPer and βTau, to revise the list of DIBs in oPer direction known from literature. We found that many telluric features simulate interstellar absorptions. We present the example parts of spectra to visualize this problem

Spectroscopic and Photometric Study of the Contact Binary BO CVn

We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88 percent. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20-24 percent, while the absolute parameters of components are: M1=1.16, M2=0.39, R1=1.62 and R2=1.00 (in solar units). The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt = 6.3 \times 10-8M\odot/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility)Comment: 16 pages, 5 figures, 5 tables, accepted for publication by New Astronom

Optical monitoring of FRII-type radio quasars

We present preliminary results of optical monitoring of sample of FRII-type radio quasars. The optical observations were made with three telescopes, among them one robotic, spanning a time interval longer than two years. Variability in the range of a fraction of a magnitude was observed for all eight targets. We applied the structure function to analyse the brightness changes. The slope of the structure function is only consistent with the disk instability model for two sources; the other sources show values between of the disk instability and starburst models. Finally we argue that such monitoring would be most suitable as a long-term, complementary program for robotic telescopes

CGCG 292-057 - a radio galaxy with merger-modulated radio activity

We announce the discovery of a unique combination of features in a radio source identified with the merger galaxy CGCG 292-057. The radio galaxy both exhibits a highly complex, X-like structure and shows signs of recurrent activity in the form of double-double morphology. The outer lobes of CGCG 292-057 are characterized by low radio power, P_{1400MHz} \simeq 2 * 10^{24} W\Hz^{-1}, placing this source below the FRII/FRI luminosity threshold, and are highly polarized (almost 20 per cent at 1400 MHz) as is typical of X-shaped radio sources. The host is a LINER-type galaxy with a relatively low black hole mass and double-peaked narrow emission lines. These features make this galaxy a primary target for studies of merger-triggered radio activity.Comment: 7 pages, 5 figures, submitted to MNRA

Exploring the active galactic nuclei population with extreme X-ray-to-optical flux ratios (fx/fo > 50)

The cosmic history of the growth of supermassive black holes in galactic centres parallels that of star formation in the Universe. However, an important fraction of this growth occurs inconspicuously in obscured objects, where ultraviolet/optical/near-infrared emission is heavily obscured by dust. Since the X-ray flux is less attenuated, a high X-ray-to-optical flux ratio (fx/fo) is expected to be an efficient tool to find out these obscured accreting sources. We explore here via optical spectroscopy, X-ray spectroscopy and infrared photometry the most extreme cases of this population (those with fx/fo > 50, EXO50 sources hereafter), using a well-defined sample of seven X-ray sources extracted from the 2XMM catalogue. Five EXO50 sources (~70?per?cent of the sample) in the bright flux regime explored by our survey (f(2-10?keV) = 1.5 × 10-13 erg?cm-2?s-1) are associated with obscured AGN (NH > 1022 cm-2), spanning a redshift range between 0.75 and 1 and characterized by 2–10 keV intrinsic luminosities in the QSO regime (e.g. well in excess to 1044 erg?s-1). We did not find compelling evidence of Compton thick active galacic nuclei (AGN). Overall, the EXO50 type 2 QSOs do not seem to be different from standard X-ray-selected type 2 QSOs in terms of nuclear absorption; a very high AGN/host galaxy ratio seems to play a major role in explaining their extreme properties. Interestingly, three out of five EXO50 type 2 QSO objects can be classified as extreme dust-obscured galaxies (EDOGs, f24?µm/fR = 2000), suggesting that a very high AGN/host ratios (along with the large amount of dust absorption) could be the natural explanation also for a part of the EDOG population. The remaining two EXO50 sources are classified as BL Lac objects, having rather extreme properties, and which are good candidates for TeV emission.SM and FJC acknowledge financial support by the Spanish Ministry of Economy and Competitiveness through grants AYA2010-21490-C02-01 and AYA2012-31447 and from the ARCHES project, funded by the 7th Frameworkof the European Union (project no. 313146). AR acknowledgesfinancial support by the Spanish Ministry of Economy and Competitiveness through grant AYA2012-3144