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1.
We analyze observations of the compact GHZ-peaked-spectrum radio source in the nucleus of the weakly active galaxy NGC 1052, assuming that the low-frequency turnover in its spectrum is due to synchrotron self-absorption. The analysis is based on a model for an inhomogeneous source of synchrotron radiation. It is shown that the magnetic field is not uniform, but the change in the field strength from the center to the edge of the compact radio source does not exceed an order of magnitude. The maximum magnetic-field strength in the nucleus of NGC 1052 is 20 G < H ⊥ < 200 G, and the density of relativistic electrons is 0.018 cm−3 < n e < 0.18 cm−3 on scales of 0.1 pc; everywhere in the radio source, the energy density of the magnetic field exceeds the energy density of the relativistic electrons. The physical conditions are similar to those in the nuclei of the nearby radio galaxies 3C 111 and 3C 465, and differ strongly from those in the nucleus of the radio galaxy 0108+388, which is a compact GHz-peaked-spectrum source (these three galaxies were studied by the authors earlier using the same method).  相似文献   

2.
A method for studying the physical conditions in compact components of extragalactic radio sources displaying variability on time scales of hundreds of days is proposed. The method can be used to estimate the relative variations of the magnetic-field strength and number density of relativistic electrons in superluminal jets from the cores of quasars and radio galaxies. Results are presented for the jets of the quasars 3C 120, 3C 273, 3C 279, and 3C 345. The energies of the magnetic field and relativistic particles in these objects are not in equipartition. As a rule, the magnetic-field strength decreases appreciably during the evolution of an expanding jet, while the number of relativistic electrons grows.  相似文献   

3.
The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ～ 10?1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ～ 10?3 G, and the density of relativistic electrons is n e ～ 10?3 cm?3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, 〈E H 〉 = 〈E e 〉 ～ 10?7–10?6 erg cm?3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.  相似文献   

4.
Interplanetary scintillation observations of the compact nucleus of 3C 274 have been carried out at 111 MHz on on the Large Phased Array radio telescope. We have derived an upper limit for the flux density of the compact radio source, and determined the parameters of the low-frequency cutoff of the spectrum of this source. We have analyzed the observational data assuming that the low-frequency spectral cutoff is due to synchrotron self-absorption. In this case, the magnetic field in the nucleus of 3C 274 must be very nonuniform. At the center, on scales of < 0.01 pc, the magnetic field varies in the range 0.4 G < H < 40 G, while its mean value over the entire radio source is 〈H〉 ～ 10?3 ? 10?4 G. The energy density of the relativistic electrons exceeds the energy density of the magnetic field everywhere within the nucleus, though energy equipartition is also possible near the center.  相似文献   

5.
Interplanetary scintillation observations of the radio sources 4C 31.04, 3C 67, 4C 34.07, 4C 34.09, OE 131, 3C 93.1, OF 247, 3C 147, 3C 173, OI 407, 4C 68.08, 3C186, 3C 190, 3C 191, 3C 213.1, 3C 216, 3C 237, 3C 241, 4C 14.41, 3C 258, and 3C 266 have been carried out at 102 MHz. Scintillations were detected for nearly all the sources. The integrated flux densities and flux densities of the scintillating components are estimated. Nine of the 21 sources have a low-frequency turnover in their spectra; three of the sources have high-frequency turnovers. The physical parameters are estimated for sources with turnovers in the spectra of their compact components. In most of the quasars, the relativistic-plasma energy exceeds the magnetic-field energy, while the opposite is true of most of the radio galaxies. Empirical relations between the size of the compact radio source and its magnetic field and relativistic-electron density are derived.  相似文献   

6.
It is shown that composite radio spectra of the hot spots of the radio galaxy Cygnus A can be fully explained by assuming a nonuniform distribution of the magnetic fields inside the hot spots, without invoking any physical mechanisms other than synchrotron radiation. The magnetic fields are strong (B ?? 10?2?10?1 G) at the center of the hot spots, and decreases at the hot-spot edges to the level of the magnetic field of the radio lobes in which the hot spots are embedded (B ?? 10?4?10?5 G). The difference in the magnetic field between the hot-spot center and edge decreases during the evolution, while the average magnetic-field intensity increases.  相似文献   

7.
We investigate the nature of bright radio sources with known radio spectra in the direction of the nearby cluster of galaxies A569 (z=0.0193). The optical identifications of the sources show that 45% of these radio sources are associated with compact galaxies. A substantial fraction of these galaxies have active nuclei, with the radio emission concentrated toward the galactic center. Some of the cluster galaxies have radio halos, with appreciably weaker radio powers and spectral indices α=0.95±0.2. We compute the magnetic fields in the nuclei and halos of the galaxies for the adopted distance to A569. As expected, the magnetic fields in the galactic halos make a smooth transition to the intergalactic field, while the magnetic fields in the central regions of the galaxies rise sharply toward the nucleus.  相似文献   

8.
Weak, compact radio sources (～100 mJy peak flux, L～1–10 pc) with their spectral peaks at about a gigahertz are studied, based on the complete sample of 46 radio sources of Snellen, drawn from high-sensitivity surveys, including the low-frequency Westerbork catalog. The physical parameters have been estimated for 14 sources: the magnetic field (H ⊥), the number density of relativistic particles (n e), the energy of the magnetic field $(E_{H_ \bot } )$ , and the energy of relativistic particles (E e). Ten sources have $E_{H_ \bot } \ll E_e $ , three have approximate equipartition of the energies $(E_{H_ \bot } \sim E_e )$ , and only one has $E_{H_ \bot } \gg E_e $ . The mean magnetic fields in quasars (10?3 G) and galaxies (10?2 G) have been estimated. The magnetic field appears to be related to the sizes of compact features as $H \sim 1/\sqrt L $ .  相似文献   

9.
The arrival directions of extensive air showers with energies 4×1019<E≤3×1020 eV detected by the AGASA, Yakutsk, Haverah Park, and Fly’s Eye arrays are analyzed in order to identify possible sources of cosmic rays with these energies. We searched for active galactic nuclei, radio galaxies, and X-ray pulsars within 3-error boxes around the shower-arrival directions and calculated the probabilities of objects being in the 3 error boxes by chance. These probabilities are small in the case of Seyfert galaxies with redshifts z<0.01 and BL Lac objects, corresponding to P>3σ (σ is the parameter of Gaussian distribution). The Seyfert galaxies are characterized by moderate luminosities (L<1046 erg/s) and weak radio and X-ray emission. We also analyzed gamma-ray emission at energies E>1014 eV recorded by the Bolivian and Tian Shan arrays. The source identifications suggest that the gamma rays could have been produced in interactions of cosmic rays with the microwave background radiation and subsequent electromagnetic cascades in intergalactic space. We estimate the strength of intergalactic magnetic fields outside galaxy clusters to be B≤8.7×10?10 G.  相似文献   

10.
A phenomenological model for the evolution of classical radio galaxies such as Cygnus A is presented. An activity cycle of the host galaxy in the radio begins with the birth of radio jets, which correspond to shocks on scales ～1 pc (the radio galaxy B0108+388). In the following stage of the evolution, the radio emission comes predominantly from formations on scales of 10–100 pc, whose physical parameters are close to those of the hot spots of Cygnus A (this corresponds to GHz-peaked spectrum radio sources). Further, the hot spots create radio lobes on scales of 103–104 pc (compact steep-spectrum radio sources). The fully formed radio galaxies have radio jets, hot spots, and giant radio lobes; the direction of the jets can vary in a discrete steps with time, creating new hot spots and inflating the radio lobes (as in Cygnus A). In the final stage of the evolutionary cycle, first the radio jets disappear, then the hot spots, and finally the radio lobes (similar to the giant radio galaxies DA 240 and 3C 236). A large fraction of radio galaxies with repeating activity cycles is observed. The close connection between Cygnus A-type radio galaxies and optical quasars is noted, as well as similarity in the cosmological evolution of powerful radio galaxies and optical quasars.  相似文献   

11.
A method for estimating the magnetic-field strengths and angular sizes of radio sources displaying synchrotron self-absorption based on their observed radio spectra is considered. The method is used to derive the angular sizes of compact radio sources (components) and the magnetic fields in these regions, as well as the energy and number of relativistic electrons and the radiative power of a number of quasars and radio galaxies.  相似文献   

12.
The formation and evolution of supermassive (102?1010 M ⊙) black holes (SMBHs) in the dense cores of globular clusters and galaxies is investigated. The raw material for the construction of the SMBHs is stellar black holes produced during the evolution of massive (25?150M ⊙) stars. The first SMBHs, with masses of ～1000M ⊙, arise in the centers of the densest and most massive globular clusters. Current scenarios for the formation of SMBHs in the cores of globular clusters are analyzed. The dynamical deceleration of the most massive and slowly moving stellar-mass (< 100M ⊙) black holes, accompanied by the radiation of gravitational waves in late stages, is a probable scenario for the formation of SMBHs in the most massive and densest globular clusters. The dynamical friction of the most massive globular clusters close to the dense cores of their galaxies, with the formation of close binary black holes due to the radiation of gravitational waves, leads to the formation of SMBHs with masses ? 103 M ⊙ in these regions. The stars of these galaxies form galactic bulges, providing a possible explanation for the correlation between the masses of the bulge and of the central SMBHs. The deceleration of the most massive galaxies in the central regions of the most massive and dense clusters of galaxies could lead to the appearance of the most massive (to 1010 M ⊙) SMBHs in the cores of cD galaxies. A side product of this cascade scenario for the formation of massive galaxies with SMBHs in their cores is the appearance of stars with high spatial velocities (> 300 km/s). The velocities of neutron stars and stellar-mass black holes can reach ～105 km/s.  相似文献   

13.
We consider the evolution of galaxies in dense galactic clusters. Observations and theoretical estimates indicate that this evolution may be specified to a large extent by collisions between galaxies, as well as interactions between the gaseous components of disk galaxies and intergalactic gas. We analyze collisions between disk galaxies with gaseous components using a simple model based on a comparison of the duration of a collision and the characteristic cooling time for the gas heated by the collision, and also of the relative masses of stars and gas in the colliding disk galaxies. This model is used to analyze scenarios for collisions between disk galaxies with various masses as a function of their relative velocities. Our analysis indicates that galaxies can merge, lose one or both of their gaseous components, or totally disintegrate as a result of a collision; ultimately, a new galaxy may form from the gas lost by the colliding galaxies. Disk galaxies with mass M G and velocities exceeding ～300 (M G/1010 M ⊙)1/2 km/s in intergalactic gas in clusters with densities ～10?27 g/cm3 can lose their gas due to the pressure of inflowing intergalactic gas, thereby developing into E(SO) galaxies.  相似文献   

14.
The possibility of selecting extended radio sources that are potential candidates for giant radio galaxies among objects in the Pushchino catalog at 102 MHz is considered. The method used is based on the analysis of objects in a α 1–α 2 diagram, where α 1 and α 2 are two-frequency spectral indices (S ν ～ ν ?α ), formally calculated using 102–365 and 365–1400 MHz data, based on the identifications of Pushchino radio sources with objects of the Texas (365 MHz) and Green Bank (1400 MHz) catalogs. The calculated spectra are abnormally steep at 102–365 MHz and flat or even inverted at 365–1400 MHz, due to the fact that the 365-MHz flux densities of extended radio sources measured with the Texas radio interferometer are appreciably underestimated. Ten objects among the fifteen Pushchino radio sources selected using this criterion proved to be already known large radio galaxies. The possibility of improving the efficiency of the method by using larger samples and applying some additional criteria selecting candidate giant radio galaxies is considered.  相似文献   

15.
Our measurements of the arrival-time delays of radio pulses from the Crab pulsar, PSR B0531+21, at low frequencies 111, 63, and 44 MHz revealed additional delays compared to the usual quadratic frequency relation, Δt(v) ∝ v ?2. These additional delays are 65 ms between 63 MHz and 111 MHz—i.e., a factor of two longer than the pulsar’s period, i.e., a factor of five longer than the pulsar period—and cannot be explained by the “twisting” of the magnetic-field lines by the rotation of the pulsar. We suggest the model in which a previously unknown high-density plasma layer with a high electron concentration is present along the line of sight in the Crab nebula, causing an additional frequency-dependent delay of the observed radio pulses at low frequencies due to the contribution of the n e 2 v ?4 term in the dispersion-delay formula. The parameters of this inferred layer have been derived: emission measure EM ? 4 × 106 pc/cm6, electron density n e ? 106 cm?3, depth along the line of sight d ? 4 × 10?6 pc, and electron temperature T e ≥ 2 × 106 K.  相似文献   

16.
We study a compact group of 18 galaxies in the cluster A1367 with redshifts z = 0.0208–0.025. The group’s center of activity in the radio is the galaxy NGC 3862, whose radio flux is an order of magnitude stronger than for the other members of the group. We present coordinates derived from the Palomar plate archive together with recessional velocities, and analyze other characteristics of the group’s galaxies. The results of 1400 MHz observations of NGC 3862 with the RATAN-600 radio telescope are presented. These observations indicate that the galaxy’s radio emission is variable.  相似文献   

17.
BV RI data are presented for the majority of steep-spectrum objects in the RC catalog with m R <23.5m. Previously developed programs are applied to these data to estimate the redshifts and ages of the stellar systems of the host galaxies. Applying this program to the color data (BV RI JHK) for distant radio galaxies with spectroscopic redshifts indicates that this approach provides accurate estimates of the redshifts of such radio galaxies, close to those obtained using field galaxies (～20%). The age estimates are much less trustworthy, but a lower limit to the ages of objects that are not very distant (z<1.5) can be determined with certainty. We have identi fied several galaxies whose formal ages exceed the age of the Universe at the corresponding z in simple Cold Dark Matter models for the Universe. The possibility of using such objects to elucidate the role of “dark energy” is discussed. This paradox disappears in models with cosmological constants (Λ terms) equal to 0.6–0.8.  相似文献   

18.
The results of spectroscopic observations of the host galaxies of objects in the RC catalog (the “Big Trio” program) obtained using the new SCORPIO spectrograph of the Special Astrophysical Observatory are presented. The spectroscopic redshifts of the objects are compared with their photometric color redshifts, and the errors in the latter are estimated. Based on BV RI observations obtained on the 6-m telescope of the SAO, the errors for the population of powerful radio galaxies are close to those found previously for radio quiet galaxies (about 10–20%). The detection of Ly α in the B filter in RC 1626+0448 is confirmed. This object is the second spectrally studied FR II radio source from the RC catalog to have a redshift z>2.5. Star formation in its host galaxy began at a redshift z>3.3. This first use of the new SCORPIO spectrograph demonstrates its promise for studies of very distant steep-spectrum radio galaxies brighter than 23m–24m in V.  相似文献   

19.
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   

20.

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.

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