1.4-GHz Luminosity Function of Galaxies from the Las Campanas Redshift Survey

A preliminary 1.4 GHz RLF at redshift of about 0.14 is derived from the Las Campanas Redshift Survey (LCRS) and the NVSS radio data. No significant evolution has been found at this redshift in comparison to the 'local' RLF.Comment: 2 pages including 2 Postscript figures, uses crckapb10.st

Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population

The time evolution of giant (D>1 Mpc) lobe-dominated galaxies is analysed on the basis of dynamical evolution of the entire FRII-type population.Comment: 4 pages, 2 Postscript figures, uses baltlat1.sty To be published in "Radio astronomy at 70: from Karl Jansky to microjansky", JENAM-2003 Symposium, eds. L.Gurvits and S.Frey, (Baltic Astronomy

GB2 0909+353: One of the Largest Double Radio Source

The evidence are given that the radio source GB2 0909+353 (GB2 catalogue: Machalski 1978; ICRS 2000.0 coordinates: 09 12 51.7, +35 10 10) is likely one of the largest classical doubles known, though its optical identification is not certain. Our deep VLA observations at 5 GHz did not reveal a radio core brighter than 0.5 mJy/beam at this frequency. Thus a distance to the source is evaluated using photometric -- redshift estimates of the faint galaxies in the optical field. The equipartition magnetic field and energy density in the source is calculated and compared with corresponding parameters of other `giant' radio sources known, showing extremely low values of both physical parameters of the source investigated. On the other hand, the age of relativistic electrons, and the advance speed of the `hot spot' in the source are typical for much smaller and brighter 3CR sources.Comment: 10 pages with 3 Postscript figures, accepted to Acta Astronomic

The new sample of giant radio sources III. Statistical trends and correlations

In this paper we analyse whether `giant' radio galaxies (GRGs) differ from `normal'-size galaxies (NSGs) except for the linear extent of their radio structure. We compare a number of properties of GRGs with the corresponding properties of NSGs, and analyse the statistical trends and correlations of physical parameters, homogeneously determined for the sources, with their `fundamental' parameters. Using the Pearson partial-correlation test on the correlation between two variables in the presence of one or two other variables, we examine which correlation is the strongest. The analysis clearly shows that GRGs do not form a separate class of radio sources. They most likely evolve with time from smaller sources, however under specific circumstances. Analysing properties of GRGs and NSGs together, we find that (i) the core prominence does not correlate with the total radio luminosity (as does the core power), but it anti-correlates with the surface brightness of the lobes of sources, (ii) the energy density (and possibly the internal pressure) in the lobes is independent of redshift for constant radio luminosity and size of the sources, (iii) the equipartition magnetic-field strength, transformed into constant source luminosity and redshift, strongly correlates with the source size. We argue that this B_{eq} - D correlation reflects a more fundamental correlation between B_{eq} and the source age, (iv) both the rotation and depolarisation measures suggest Faraday screens local to the lobes of sources, however their geometry and the composition of intervening material cannot be determined from the global polarisation characteristics.Comment: 10 pages, 8 figures, 6 tables. Accepted for publication in A&

Giant Radio Sources in View of the Dynamical Evolution of FRII-type Population. I. The Observational Data, and Basic Physical Parameters of Sources Derived from the Analytical Model

The time evolution of giant lobe-dominated radio galaxies (with projected linear size D>1 Mpc if H_{0}=50 km/s/Mpc and q_{0}=0.5 is analysed on the basis of dynamical evolution of the entire FRII-type population. Two basic physical parameters, namely the jet power Q_{0} and central density of the galaxy nucleus rho0 are derived for a sample of giants with synchrotron ages reliably determined, and compared with the relevant parameters in a comparison sample of normal-size sources consisting of 3C, B2, and other sources. Having the apparent radio luminosity P and linear size D of each sample source, Q_{0} and rho_{0} are obtained by fitting the dynamical model of Kaiser et al. (1997). We find that: (i) there is not a unique factor governing the source size; they are old sources with temperate jet power (Q_{0}) evolved in a relatively low-density environment (rho_{0}). The size is dependent, in order of decreasing partial correlation coefficients, on age; then on Q_{0}; next on rho_{0}. (ii) A self-similar expansion of the sources' cocoon seems to be feasible if the power supplied by the jets is a few orders of magnitude above the minimum-energy value. In other cases the expansion can only initially be self-similar; a departure from self-similarity for large and old sources is justified by observational data of giant sources. (iii) An apparent increase of the lowest internal pressure value observed within the largest sources' cocoon with redshift is obscured by the intrinsic dependence of their size on age and the age on redshift, which hinders us from making definite conclusions about a cosmological evolution of intergalactic medium (IGM) pressure.Comment: 36 pages, 8 figures, 7 table

The Dynamics of Radio Galaxies and Double-Double Radio Galaxies

Relativistic and magnetised plasma ejected by radio loud AGNs through jets form the diffuse lobes of radio galaxies. The radiating particles (electron/electron-positron) in lobes emit in radio via the synchrotron process and X-ray via inverse-Compton scattering of cosmic microwave background photons. The thermal environment around radio galaxies emits X-rays via the thermal bremsstrahlung process. By combining information from these processes we can measure physical conditions in and around the radio lobes and thus study the dynamics of radio galaxies, including double-double radio galaxies.Comment: 11 pages, 4 figures, Diffuse Radio Plasma Conference proceedings (held in Raman Research Institute, Bangalore, India

Large-Scale Radio Structure in the Universe: Giant Radio Galaxies

Giant radio galaxies (GRGs), with linear sizes larger than 1 Mpc (H0=50 km/s/Mpc), represent the biggest single objects in the Universe. GRGs are rare among the entire population of radio galaxies (RGs) and their physical evolution is not well understood though for many years they have been of special interest for several reasons. The lobes of radio sources can compress cold gas clumps and trigger star or even dwarf galaxy formation, they can also transport gas from a host galaxy to large distances and seed the IGM with magnetic fields. Since GRGs have about 10 to 100 times larger sizes than normal RGs, their influence on the ambient medium is correspondingly wider and is pronounced on scales comparable to those of clusters of galaxies or larger. Therefore `giants' could play an important role in the process of large-scale structure formation in the Universe. Recently, thanks to the new all sky radio surveys, significant progress in searching for new GRGs has been made.Comment: To appear in Multiwavelength AGN Surveys, ed. R. Maiolino and R. Mujica, Singapore: World Scientific, 2004, 2 page

A multifrequency study of giant radio sources I. Low-frequency Giant Metrewave Radio Telescope observations of selected sources

We present low-frequency observations with the Giant Metrewave Radio Telescope (GMRT) of a sample of giant radio sources (GRSs), and high-frequency observations of three of these sources with the Very Large Array (VLA). From multifrequency observations of the lobes we estimate the magnetic field strengths using three different approaches, and show that these differ at most by a factor of $\sim$3. For these large radio sources the inverse-Compton losses usually dominate over synchrotron losses when estimates of the classical minimum energy magnetic field are used, consistent with earlier studies. However, this is often not true if the magnetic fields are close to the values estimated using the formalism of Beck & Krause. We also examine the spectral indices of the cores and any evidence of recurrent activity in these sources. We probe the environment using the symmetry parameters of these sources and suggest that their environments are often asymmetric on scales of $\sim$1 Mpc, consistent with earlier studies.Comment: 14 pages, 5 figures, 6 tables, one appendix; accepted for publication in MNRA