A search for faint giant radio galaxies in the NVSS survey

Giant radio galaxies are the most extended radio sources in the universe having the sizes of groups and clusters of galaxies (about 1 Mpc). Their total number is comparable with the amount of clusters, revealing the Zeldovich-Sunyaev effect, which may lead to a biased estimation of the angular power spectrum for the ZS effect. To assess a possible contribution to the power spectrum, we need to collect the data on all the observed giant radio galaxies. We propose an algorithm for the selection of large sources (sized over 4′) from the NVSS survey catalog, using the parameters of possible components of radio sources, cataloged as compact objects. As a result of the first stage of our work, we have selected 61 new giant radio galaxy candidates, of which 35 have a pronounced morphological type FRII, and 26 galaxies—the FRI type.     

Investigating statistical and spectral characteristics of the radio sources from the RadioAstron catalog at millimetric wavelengths

We consider some statistical characteristics of radio sources at 22 GHz in the framework of the preparatory works on the RadioAstron space mission. The expected density of radio sources with inverted spectra is estimated. Based on the observations of the radio sources from the preliminary RadioAstron sample, we compare the expected and measured angular densities of the radio sources with inverted spectra. The optical characteristics of the objects with inverted spectra and of the sources from the complete sample are compared as well. We present some spectral parameters of the radio sources observed at two different frequencies. Some conclusions about the completeness and reliability of the preliminary RadioAstron catalog are made.     

Forthcoming close angular approaches of planets to radio sources and possibilities to use them as GR tests

During close angular approaches of solar system planets to astrometric radio sources, the apparent positions of these sources shift due to relativistic effects and, thus, these events may be used for testing the theory of general relativity; this fact was successfully demonstrated in the experiments on the measurements of radio source position shifts during the approaches of Jupiter carried out in 1988 and 2002. An analysis, performed within the frames of the present work, showed that when a source is observed near a planet’s disk edge, i.e., practically in the case of occultation, the current experimental accuracy makes it possible to measure the relativistic effects for all planets. However, radio occultations are fairly rare events. At the same time, only Jupiter and Saturn provide noticeable relativistic effects approaching the radio sources at angular distances of about a few planet radii. Our analysis resulted in the creation of a catalog of forthcoming occultations and approaches of planets to astrometric radio sources for the time period of 2008–2050, which can be used for planning experiments on testing gravity theories and other purposes. For all events included in the catalog, the main relativistic effects are calculated both for ground-based and space (Earth-Moon) interferometer baselines.     

On the spectral index of distant radio galaxies

The problems of using the spectral index of radio galaxies in various tests, in particular, in selecting distant radio sources are considered. The history of the question of choosing a criterion of searching for distant radio galaxies based on the spectral index is presented. For a new catalog of 2442 radio galaxies constructed from NED, SDSS, and CATS data, an analytical form of the spectral index-redshift relation has been determined for the first time. The spectral index-angular size and spectral index-flux density diagrams have also been constructed. Peculiarities of the distribution of sources on these diagrams are discussed.     

Cosmic radio sources with the peaks of spectral flux density at decameter wavelengths (According to the Grakovo catalog)

Spectral characteristics of extragalactic radio sources of synchrotron emission with spectral flux density maxima located at decameter wavelengths are studied on the basis of the Grakovo catalog data. Physical processes in space that can give rise to such spectra are considered. Angular sizes and possible characteristics of relevant cosmic plasma are determined for a number of sources.     

Analysis of a sample of RC catalog objects in the region overlapping with the areas covered by FIRST and SDSS surveys. II: Optical identification with the SDSS survey and USNO-B1 and 2MASS catalogs

We report the results of optical identification of a sample of RC catalog radio sources with the FIRST and SDSS surveys. For 320 sources identified with NVSS and FIRST objects we perform optical identification with the SDSS survey. When selecting optical candidates we make maximum use of the information about the structure of radio sources as provided by the FIRST survey images. We find optical candidates for about 70% of all radio sources.     

Anisotropy of the space orientation of radio sources. I: The catalog

A catalog of extended extragalactic radio sources consisting of 10461 objects is compiled based on the list of radio sources of the FIRST survey. A total of 1801 objects are identified with galaxies and quasars of the SDSS survey and the Veron-Veron catalog. The distribution of position angles of the axes of radio sources from the catalog is determined, and the probability that this distribution is equiprobable is shown to be less than 10⁻⁷. This result implies that at Z equal to or smaller than 0.5, the spatial orientation of the axes of radio sources is anisotropic at a statistically significant level.     

Observational manifestations and intrinsic properties of the RCR sources in terms of a unified model

We present a summary results of the study of radio sources showing significant variations of integral flux density using the data from the RATAN-600 surveys of 1980–1994 at a frequency of 7.6 cm. The majority of the detected variable sources have flat radio spectra, although there are also all other spectrum types found. Point and compact sources predominate, although all known morphological structures are found in the sample. Variability is detected both in quasars and galaxies. Using the catalog data, we found brightness variations in the optical and/or infrared ranges for a half of host objects of radio sources. We analyzed the properties of nonvariable and variable RCR sources. We compared the ratio of absolute magnitude to radio luminosity for sources with the active nucleus types determined from the optical data. It is found that this parameter is approximately the same for quasars with different radio luminosity. It isminimum for the strongest radio galaxies and grows up to the level characteristic of quasars with the decrease of radio luminosity. Considering that the ratio depends on obscuring properties of a dust torus, such behavior can be explained if we assume that the torus geometry and its optical depth depend on the source long. This parameter is slightly higher among variable sources than among nonvariable ones which counts in favor of the nucleus more open to an observer.     

Extragalactic sources with very asymmetric radio structure: VLA and MERLIN observations

As part of our study to understand the nature of extragalactic radio sources which are very asymmetric in the surface brightness of the two lobes, often with radio emission on only one side of the nucleus, we have observed a large number of them with high angular resolution and good surface brightness sensitivity at radio frequencies. In this paper we present VLA and MERLIN observations of 15 such sources. We discuss their observed structures and spectra, and possible explanations for their morphologies. We report evidence of a possible correlation between the hot-spot brightness ratio and the degree of core prominence, used as a Statistical measure of source orientation, suggesting that relativistic beaming of the hot-spot emission does play a significant role in the observed brightness asymmetry. To explain the apparently one-sided sources within the relativistic beaming framework, the velocities required are in the range of 0.2 to 0.8c. We discuss the possibility that the lobe which is seen to the south of the jet in 3C273 is the counter-lobe seen in projection. We also draw-attention to a number of one-sided sources with very weak cores, and discuss their possible nature.     

Analysis of the RC catalog sample in the region overlapping with the regions of the FIRST and SDSS surveys: I. Identification of sources with the VLSS, TXS, NVSS, FIRST, and GB6 catalogs

Radio sources of the RC catalog produced in 1980–1985 at RATAN-600 radio telescope based on a deep survey of a sky strip centered on the declination of the SS433 source are optically identified in the region overlapping with FIRST and SDSS surveys (about 132?° large). The NVSS catalog was used as the reference catalog for refining the coordinates of the radio sources. The morphology is found for about 75% of the objects of the sample and the ratio of single, double and multicomponent radio sources is computed based on FIRST radio maps. The 74, 365, 1400, and 4850MHz data of the VLSS, TXS, NVSS, FIRST, and GB6 catalogs are used to analyze the shape of the spectra.     

Radio identification of decameter-wave sources. II: The 30°< <Emphasis Type="Italic">δ</Emphasis> <40° declination interval

This paper is dedicated to the identification of decameter-wave sources of the UTR catalog within declination interval 30°< δ <40°. UTR sources are cross-identified with CATS database catalogs within 40′ × 40′ error boxes. The sources are deblended using the data on the coordinates of the objects and the behavior of their continuum radio spectra. The spectra of 875 sources are derived and fitted by standard analytical functions. Of these sources, 221 objects have straight-line spectra with spectral indices α < ?1.0. All objects are catalogued and stored in the CATS database.     

The radio properties of a sample of optically selected radio-loud quasars

We searched for identification between the Large Bright Quasar Survey and the latest whole-sky survey catalog of 4.85 GHz radio sources. We found 34 quasars to have radio counterparts and they proved to be radio-loud objects. We found a nearly linear correlation between their radio and optical luminosities in this, probably the largest so far, sample of radio-loud quasars.     

Radio pulsars with expected gamma radiation and gamma-ray pulsars as pulsating radio emitters

Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s~(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.     

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.     

Radio Observation of the 11-Month Fermi-AGN at Urumqi Observatory

We carry out flux observation at 5 GHz for 124 sources from the ‘clean’ sample of Fermi catalog 1LAC (The First LAT AGN Catalog) with Urumqi 25 m telescope. We find that it is obvious that there is a correlation between the γ-ray and the radio flux density for blazars. For the subclasses, the correlation for FSRQs is strong, but the correlation for BL Lacs is weak.     

Deep 7.6 cm RATAN-600 sky surveys at the declination of SS 433 during the 1980–1999 period. Catalog of radio sources in the right-ascension interval 2<Superscript>h</Superscript> ≤ RA &lt; 7<Superscript>h</Superscript>

We present a catalog of radio sources extending the RCR (RATAN Cold Refined) catalog to the right-ascension interval 2^h ≤ RA < 7^h. The list of objects was obtained in the process of a reprocessing of the observations of the “Cold” experiment conducted in 1980–1981 on RATAN-600 radio telescope at the declination of SS433, and the reduction of the 1987–1999 surveys of the same experiment.We report the right ascensions and integrated flux densities for 237 sources found at 7.6 cm (3.94 GHz) and their spectral exponents at 3.94 and 0.5 GHz. Twenty-nine sources of the list, which are mostly weaker than 30 mJy at 3.94 GHz, have available data only at two frequencies—1.4 and 3.94 Hz.We approximated the spectra of the sources using all catalogs available in the CATS and VizieR databases that meet the survey strip, and, in some cases, using the flux densities estimates from VLSSr,GLEAM, TGSS, and GB6 survey maps.We constructed the histograms of the spectral indices of the sources and verified the reliability of the identifications of sources found in the scans by comparing the coordinates and integrated flux densities with the corresponding parameters listed in the NVSS catalog. In the right ascension interval considered we found no objects at the 10–15 mJy level lacking in decimeter-wave catalogs.     

Search for spatial and spectral fluctuations of cosmic microwave background radiation with the ratan-600 radio telescope. The 2001–2006 observations

We report some of the results of the search for narrow-band spatial and spectral fluctuations of cosmic microwave background at the wavelength of 6.2 cmperformed with the RATAN-600 radio telescope in 2001–2006 in two 35′ × 7′ strips on the sky in the vicinity of the North Celestial Pole. We find the spectra of spatial fluctuations in the 12 MHz radio-frequency band and in the interval of spatial periods from 4′ to 16′ to exhibit power-law rises with exponents reaching ?2.0±0.5, with a periodicity of 2–3 MHz. We also find two narrow-band (in terms of angular frequency) features at 4870.4 and 4871.5 MHz with the corresponding fluctuation amplitudes of 5±0.5 mK in terms of antenna temperature in the vicinity of angular periods of about 5′ with the frequency bandwidths of about 600 kHz. Standard tests performed using the spectra of the half-sum and half-difference of two groups of observations randomly drawn from a total sample of 23 records of the March 2002 observing set confirm the reality of the features of the angular spectrumof fluctuations mentioned above and so does the comparison with the spectra of cold matched load connected to the receiver input instead of the antenna. However, the nature of the features found remains unclear. Our attempt to link this radiation to rotational transitions ²Π_1/2, J = 5/2 of the CH molecule, which has one of the components of its multiplet located inside the frequency interval of interest considered failed.     

<Emphasis Type="Italic">UVR</Emphasis> CCD photometry of stars in five sky areas with matched IR/radio sources

Five sky areas about the radio sources ICRS 1254+571, ICRS 1345+125, ICRS 1641+399, ICRS 1732+389, and ICRS 1807+698 were observed with the aim to identify reliably the extragalactic radio sources in these areas with bright infrared objects and objects in the optical range. The test CCD observations were made in the U, V, and R bands of the Johnson system with the 2-meter telescope of the Terskol Peak Observatory (North Caucasus, Russian Federation). The U, V, and B magnitudes and the equatorial coordinates α and δ in the USNO-A2.0 catalog system were determined for objects down to V ≈ 23^m in 8.5′ × 8.5′ areas, and these objects were identified with stars and infrared objects in the 2MASS catalog. The CCD image processing realized within the MIDAS/ROMAFOT program package on the basis of a new method for flat-field elimination is briefly described.     

Differential astrometry over 15°

We observed the pair of radio sources 1150+812 and 1803+784 in November 1993 with a VLBI array, simultaneously recording at 8.4 and 2.3 GHz. We determined the angular separation between the two sources with submilliarcsecond accuracy by using differential techniques. This result demonstrates the feasibility of high precision differential astrometry for radio sources separated in the sky by almost 15°, and opens the avenue to its application to larger samples of radio sources.