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1.
Yu. N. Parijskij A. I. Kopylov A. V. Temirova N. S. Soboleva O. P. Zhelenkova O. V. Verkhodanov W. M. Goss T. A. Fatkhullin 《Astronomy Reports》2010,54(8):675-695
We present the results of spectroscopy of 71 objects with steep and ultra-steep spectra (α < −0.9, S ∝ ν
α) from the “Big Trio” (RATAN-600-VLA-BTA) project, performed with the “Scorpio” spectrograph on the 6-m telescope of the Special
Astrophysical Observatory (Russian Academy of Sciences). Redshifts were determined for these objects. We also present several
other parameters of the sources, such as their R magnitudes, maximum radio sizes in seconds of arc, flux densities at 500, 1425, and 3940 MHz, radio luminosities at 500 and
3940 MHz, and morphology. Of the total number of radio galaxies studied, four have redshifts 1 ≤ z < 2, three have 2 ≤ z < 3, one has 3 ≤ z < 4, and one has z = 4.51. Thirteen sources have redshifts 0.7 < z < 1 and 15 have 0.2 < z < 0.7.Of all the quasars studied, five have redshifts 0.7 < z < 1, seven have 1 ≤ z < 2, four have 2 ≤ z < 3, and one has z = 3.57. We did not detect any spectral lines for 17 objects. 相似文献
2.
We present the results of observations of a complete sample of radio sources with the RATAN-600 radio telescope at 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz. The sample was extracted from the GB6 catalog at 4.85 GHz, and contains all the sources at declinations 74°–75° (J2000) with flux densities S 4.85 > 100 mJy. We have obtained optical identifications for 67% of the radio sources with flat spectra and 30% of those with steep spectra. 相似文献
3.
Results of a study of the variability of radio sources on timescales of 3–30 days based on six sets of daily observations
on the RATAN-600 radio telescope with durations from 53 to 103 days at six frequencies from 0.97 to 21.7 GHz are reported.
The variability timescales and spectra determined from the analysis of light curves, structure functions, and autocorrelation
functions for 11 radio sources from a complete sample in the declination range 4°–6° (B1950) are presented. 相似文献
4.
The results of 0.97, 2.3, 3.9, 7.7, 11.1, and 21.7 GHz observations of a complete sample of radio sources obtained on the RATAN-600 radio telescope are presented. The sample is comprised of sources from the 4.85-GHz MGB survey, and contains all sources at declinations 10°–12°30′ (J2000) with Galactic latitudes |b|>15° and flux densities S4.85>200 mJy. Optical identifications have been obtained for about 86% of the radio sources with flat spectra and 59% of those with steep spectra. The spectra of the flat-spectrum sources have been decomposed into extended and compact components. 相似文献
5.
The results of observations of a complete sample of radio sources with spectral indices α>?0.5 (S∝v α) are presented. The sample was selected from the Zelenchuk Survey at 3.9 GHz and contains all sources with declinations 4°–6°, Galactic latitudes |b|>10°, and 3.9-GHz fluxes >200 mJy. Spectra at 0.97–21.7 GHz were obtained for all 69 sample sources. The spectra were classified, and a correlation between variability amplitude and spectrum shape was found. The spectra were separated into extended and compact components. The distribution of spectral indices α for the extended components coincides with the distribution for sources with power-law spectra. The correlation between the luminosity and frequency of the peak flux density is confirmed. This correlation is due to the fact that the distribution of source linear dimensions does not depend on luminosity. 相似文献
6.
V. L. Afanas’ev S. N. Dodonov A. V. Moiseev A. G. Gorshkov V. K. Konnikova M. G. Mingaliev 《Astronomy Reports》2006,50(4):255-272
We present classifications, optical identifications, and radio spectra for 19 radio sources from three complete samples, with declinations 4°–6° (B1950, S 3.9 GHz > 200 mJy), 10°–12°30′ (J2000, S 4.85 GHz > 200 mJy), and 74°–75° (J2000, S 4.85 GHz > 100 mJy). We also present corresponding information for the radio source J0527+0331. The right ascensions are 0–24h and the Galactic latitudes |b| > 15° for all the samples. Our observations were obtained with the 6 m telescope from the Special Astrophysical Observatory in the range 4000–9000 Å or 4000–7500 Å and the RATAN-600 radio telescope at frequencies in the range 0.97–21.7 GHz. We obtained flux densities for the radio sources and optical spectra for their optical counterparts. Nine objects were classified as quasars with redshifts from z = 1.029 to 3.212; nine objects are emission-line galaxies with redshifts from 0.172 to 0.546, and one is a galaxy with burstlike star formation at z = 0.156, and one is a BL Lac object with z = 0.509. The spectra of five radio sources were decomposed into extended and compact components. The radio source J0527+0331, identified with a BL Lac object, displays significant variations of time scales from several days to several years. Data on flux variations are presented for 11 radio sources, as well as their spectra at several epochs. 相似文献
7.
M. G. Mingaliev Yu. V. Sotnikova N. S. Kardashev M. G. Larionov 《Astronomy Reports》2009,53(6):487-500
We present the results of our observations of compact extragalactic radio sources near the north celestial pole (+75° ≤ δ ≤ +88°) obtained on the RATAN-600 radio telescope. Our sample consists of 51 radio sources with spectra that are either flat or inverted (growing toward shorter wavelengths) and with flux densities at 1.4 GHz S ν ≥ 200 mJy. We observed the sources at 1–21.7 GHz. Multi-frequency instantaneous spectra are presented for 1999–2007. We observed 33 of our sample source daily for 30 days in August 2007. As a result, we revealed 15 objects exhibiting rapid variations on time scales of a day. The multi-frequency instantaneous spectra of these sources indicate that radio flux variations on one-day timescales are characteristic of objects of various spectral types. More than half the sources exhibiting rapid variations demonstrate a growth in the variability amplitude with increasing frequency. For some of the objects, the variability amplitude is virtually independent of frequency. 相似文献
8.
V. L. Afanas’ev S. N. Dodonov A. V. Moiseev A. G. Gorshkov V. K. Konnikova M. G. Mingaliev 《Astronomy Reports》2009,53(4):287-294
We present classifications, optical identifications, and radio spectra for eight radio sources from three flux-density-complete samples in the following declination ranges: 4°–6° (B1950), S 3.9 > 200 mJy; 10°–12°30′ (J2000), S 4.85 > 200 mJy; 74°?75° (J2000), S 4.85 > 100 mJy. For all these samples, the right ascensions are 0h–24h and the Galactic latitudes, |b| > 15°. Our optical observations at 4000–7500 ° were made with the 6-m telescope of the Special Astrophysical Observatory; we also observed at 0.97–21.7 GHz with the RATAN-600 radio telescope of the Special Astrophysical Observatory. We classify four of the objects as quasars and four as galaxies. Five of the radio sources have power-law spectra at 0.97–21.7 GHz, while two objects have flat spectra. The quasar J2358+0430 virtually did not vary during 23 years. 相似文献
9.
M. G. Mingaliev Yu. V. Sotnikova N. N. Bursov N. S. Kardashev M. G. Larionov 《Astronomy Reports》2007,51(5):343-363
We have used the RATAN-600 radio telescope to study the spectral characteristics of a uniform sample of 504 radio sources from the NVSS catalog near the North Celestial Pole at six frequencies from 1.1 to 21.7 GHz, with the aim of selecting sources possessing inverted spectra near 22 GHz, to be included in the program of the Radio Astron future space VLBI mission. We found 17 radio sources with the desired spectral characteristics. Data from spectral studies over a wide wavelength range testify that the spectral behavior of our sample differs from that for a complete sample of sources with the same initial parameters but selected at 20 GHz. We find a 6% deficit of inverted-spectrum sources, which can be explained as an effect of the spectral characteristics of “sub-threshold” sources that were not included in the initial sample at 1.4 GHz. 相似文献
10.
V. L. Afanas’ev S. N. Dodonov A. V. Moiseev A. G. Gorshkov V. K. Konnikova M. G. Mingaliev 《Astronomy Reports》2005,49(5):374-389
We present optical identifications, classifications, and radio spectra for 19 radio sources from a complete sample in flux density with declinations 10°–12°30′ (J2000) obtained with the 6-m optical telescope (4000–9000 Å) and RATAN-600 radio telescope (0.97–21.7 GHz) of the Special Astrophysical Observatory. Twelve objects with redshifts from 0.573 to 2.694 have been classiffied as quasars, and two objects with featureless spectra as BL Lac objects. Four objects are emission-line radio galaxies with redshifts from 0.204 to 0.311 (one also displaying absorption lines), and one object is an absorption-line galaxy with a redshift of 0.214. Radio flux densities have been obtained at six frequencies for all the sources except for two extended objects. The radio spectra of five of the sources can be separated into extended and compact components. Three objects display substantial rapid (on time scales from several days to several weeks) and long-term variability of their flux densities. 相似文献
11.
We present the results of twenty-year observations of a complete sample of 68 flat-spectrum radio sources with flux densities S 3.9 GHz > 200 mJy carried out at centimeter wavelengths with the RATAN-600 radio telescope. Since 1995, we have observed simultaneously at six frequencies between 0.97 and 21.7 GHz. Of the 56 sources identified with optical objects, 41 are quasars with redshifts between 0.293 and 3.263. Based on our analysis of the spectral shapes, we divide the sources into four classes. Changes of spectral class for individual sources are fairly rare. Based on the light curves and spectra, in most cases, a flare’s evolution is in accordance with a model in which the variations result from the evolution of a shock in the radio jet. The main result of our study is that there is no redshift dependence for the true linear sizes of the radiating regions, the variability indices derived for all 20 years of data or for individual flares, or the peak frequencies of the spectra of the compact radio emission. We suggest that this testifies to an absence of cosmological evolution of the sample quasars, at least to z ≈ 3. 相似文献
12.
Observations of a complete sample of sources from the WMAP catalog were obtained at 22.2 and 36.8 GHz on the RT-22 radio telescope of the Crimean Astrophysical Observatory. We have determined the distribution of the source spectral indices between these frequencies. The distributions of the spectral indices of the WMAP catalog (between 23 and 33 GHz) and in the RT-22 sample have the same shape and half-width, suggesting that the mean source parameters are constant in time. We have plotted the log N — log S dependence down to the flux levels of about 0.1 Jy using pilot data from the AT20 survey, where a cosmological “cutoff” in the source counts is already observed. The variability of individual sources in connection with flare activity is considered. The optical characteristics of the complete sample of WMAP sources are compared to those of identified AT20 survey sources. 相似文献
13.
The variation of the oxygen content in olivines, (Fe
x
Mg1−
x
)2SiO4, with 0.2 ≤ x ≤ 1.0, was investigated by thermogravimetric measurements. Mass changes occurring upon oxygen activity changes were measured
as a function of oxygen activity and cationic composition at 1130 and 1200 °C. During the measurements the samples were in
direct contact with gases containing CO, CO2 and N2 and, at a few spots at the bottom of the sample stack, also with SiO2. By fitting experimental data of mass changes to equations derived using point defect thermodynamics, it was shown for olivines
with 0.2 ≤ x ≤ 1.0 at 1130 °C and 0.2 ≤ x ≤ 0.7 at 1200 °C within the oxygen activity ranges investigated that the observed variations in the oxygen contents are compatible
with cation vacancies and Fe3+ ions on M sites and Fe3+ ions on silicon sites as majority defects if it is assumed that only three types of point defects occur as majority defects.
Different cases were considered, closed systems, taking into account that ξ=[Si]/([Si]+[Fe]+[Mg]) is not necessarily equal
to 1/3, and olivines in equilibrium with SiO2 or pyroxenes. The oxygen content variations observed in this study are significantly smaller than those reported previously
in the literature. It is proposed that these differences are related to the dissolution of Fe into noble metal containers
used as sample holders in earlier studies and/or to the presence of secondary phases.
Received: 1 November 1995 / Accepted: 15 September 2002
Acknowledgements This work was supported by the Cornell Center for Materials Research (CCMR), a Materials Research Science and Engineering
Center of the National Science Foundation (DMR-0079992). The authors thank Mr. Daniel M. DiPasquo and Mr. Jason A. Schick
for helping in experimental work. 相似文献
14.
This study presents shear wave splitting analysis results observed at ISP (Isparta) broadband station in the Isparta Angle,
southwestern Turkey. We selected 21 good quality seismic events out of nearly 357 earthquakes and calculated splitting parameters
(polarization direction of fast wave, ϕ and delay time between fast and slow waves, δt) from mainly SKS and a few SKKS phases of the selected 21 seismic events. Then, we compared calculated splitting parameters
at ISP station (56° ≤ ϕ ≤ 205°; 0.37 s ≤ δt ≤ 4 s) with those previously calculated at ANTO (Ankara) and ISK (İstanbul) stations (27° ≤ ϕ ≤ 59°; 0.6 s ≤ δt ≤ 2.4 s and 26° ≤ ϕ ≤ 54°; 0.6 s ≤ δt ≤ 1.5 s) which are located at 230 and 379 km away from ISP station in central and northwestern Turkey, respectively. The
backazimuthal variations of the splitting parameters at ISP station indicate a different and complex mantle polarization anisotropy
for the Isparta Angle in southwestern Turkey compared to those obtained for Ankara and İstanbul stations. 相似文献
15.
The properties of giant radio sources (GRS’s) are considered with the aim of identifying conditions contributing to their
formation, using data from the literature, the Sloan Digital Sky Survey (SDSS), and the APM catalog. The optical and radio
properties of normal-size radio sources, (≤1 Mpc), are compared. The following conclusions are reached. (1) The fraction of
objects with broad emission lines among GRS’s with high-excitation spectra is the same as for isotropic samples of radio sources;
in the framework of the “unified scheme,” this testifies to an isotropic distribution of angles between the radio jets of
GRS’s and the line of sight, i.e., GRS’s do not represent a population of objects whose radio jets are in the plane of the
sky. (2) Giant radio sources do not differ from normal radio sources in the distributions of various asymmetry parameters
for their extended radio components; in the unified scheme, the similarity of the asymmetry distributions for giant radio
galaxies and giant radio quasars suggests that the origin of the asymmetry of their extended radio components is inhomogeneity
of the external conditions. (3) The observed powers of the radio jets of giant and normal radio sources do not differ, making
it unlikely that the large sizes of the GRS’s are due to this factor. (4) The richness and character of the environments of
giant and normal radio sources do not differ: giant host galaxies are found in both isolated fields and in clusters of up
to Abell class 1 in richness. This argues against the idea that a low density of the environment is the only origin of GRS’s.
(5) The relatively large fraction of radio sources with two pairs of extended radio components (so-called double-double radio
sources) among GRS’s testifies that the lifetimes of GRS’s are approximately an order of magnitude longer than those of normal
radio sources.Given the equal spatial densities of nearby (z < 0.1) GRS’s and FR II radio sources with powers P
1.4 MHz > 1025 W/Hz, this indicates that ∼10% of FR II radio sources have lifetimes an order of magnitude longer, and evolve into GRS’s.
(6) The small (∼0.1) ratio of the number of known GRS’s to the number of normal FR II radio sources, together with the observed
spatial density of GRS’s at z ∼ 0.6, which is an order of magnitude lower than the predicted value, suggests that a considerable number of GRS’s were missed
by surveys at z > 0.1, possibly due to observational selection effects because of their relatively low radio powers and radio surface brightnesses.
(7) The absence of “double-double” giant quasars suggests that these objects have a shorter activity time scale than GRS’s.
In an evolutionary scenario that is an alternative to the unified scheme uniting “radio loud” quasars and radio galaxies,
radio quasars evolve with time into radio galaxies, and the observed relative number of radio quasars among the GRS’s (∼10%)
can be interpreted as reflecting the existence of a long-lived population of “radio loud” quasars comprising ∼10% of all radio
quasars, with such a population of long-lived radio quasars being the parent population for giant radio galaxies. 相似文献
16.
Results of a search for and study of variability in a complete sample of flat-spectrum radio sources (83 objects) on time scales longer than a day are reported. The data were obtained in six series of daily observations on the RATAN-600 radio telescope made over 77–103 days at six frequencies from 0.97 to 21.7 GHz and at declinations of 10°–12°30′ (J2000). Variability on time scales of 3–30 days with significance levels below 1% was detected for 19 sources. The time scales, modulation indices, and spectra of the variability derived from an analysis of the light curves, structure functions, and autocorrelation functions are presented for these sources. For a number of them, intrinsic variability and extrinsic variability due to scintillations in the turbulent interstellar medium have been separated. The obtained source characteristics are compared with those for sources at declinations 4°–6° (B1950). 相似文献
17.
Radio Sources in the Central Section of the RZF Catalog. Search for Objects with Ultra-Steep Spectra
Results of reducing and selecting data from the Ratan Zenith Field (RZF) are presented. A deep survey in the region 0h ≤ R.A. ≤ 24h, 40.5° ≤ DEC ≤ 42.5° carried out on the RATAN-600 radio telescope was used. Within +2′ of the center of the survey region, 448 objects were detected, 69 of them with ultra-steep spectra (USS). The SDSS digital optical survey (DR12), NVSS radio maps, and the FIRST catalogs have been used to cross-identify 208 radio sources from the RZF catalog, obtained as part of the “Genetic Code of the Universe” project. The characteristics of these objects are studied, and the distribution of the SDSS galaxies in a two-color diagram is obtained. Photometric redshifts and radio luminosities at 3940 and 1400 MHz are determined for 27 objects with spectral indices α < −1.1 (S ∝ να) for which magnitudes in various filters are presented in the SDSS. In the sample of USS objects, 12 galaxies have redshifts z < 0.5, are detected at wavelength λ = 7.6 cm, and have relatively high radio luminosities (type FR II or intermediate type FR I–FR II). Only one radio galaxy proved to be a rare nearby galaxy with relatively low radio luminosity L1400 MHz = 1.51 × 1024 W/Hz (type FR I). Two objects are candidate GHz-Peaked Spectrum objects.
相似文献18.
19.
The paper reports the results of ten-year centimeter-wavelength observations with the RATAN-600 radio telescope of a complete sample of 83 flat-spectrum sources from the GB6 catalog of the MGB Survey, with S 4.85 > 200 mJy at declinations 10°?C12°30??. Starting in 2000, the observations were conducted simultaneously at six frequencies in the range 0.97?C21.7 GHz. Seventy-six sources (including 54 quasars) have been identified with optical objects, which have redshifts in the range z = 0.331?C3.601. Analysis of light curves and spectra at different activity phases has shown that, in most cases, the dynamics of the development of flares is consistent with a model in which the variability results from the evolution of a shock in a radio jet. A relationship between the time scales for the rise and fall of the flares has been found. There is no redshift dependence of the true linear dimensions of the radiating regions and the variability indices obtained over ten years. These facts can be interpreted as an absence of cosmological evolution of quasars at least up to z ?? 3. 相似文献
20.
Radio sources detected at 3.94 GHz in RATAN-600 observations made in 1980–1981 (the KHOLOD Survey) have been identified with objects from the NVSS catalog down to 5 mJy at 1.4 GHz, and their spectral indices have been estimated. Of the 1311 NVSS objects in the KHOLOD survey region, 836 are present in both catalogs. The average flux density of the common objects is 40 mJy, and the median flux density is 14 mJy. The average spectral indices of these objects for four flux-density intervals were calculated. The average spectral index grows with flux density. The fraction of objects with inverted spectra is 2–4%, and the average flux density of these sources is about 10 mJy. Optical identifications of the NVS S objects in the KHOLOD survey region have been carried out to R=20.5m using the Palomar plates. About 20% of the radio sources are identified with optical objects in all the radio flux-density intervals. 相似文献