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1.
We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3 < z < 5.5 selected among the X-ray sources of the “serendipitous” XMM-Newton survey presented in the 3XMMDR4 catalog (the median X-ray flux is ≈5 × 10?15 erg s?1 cm?2 in the 0.5–2 keV energy band) and located at high Galactic latitudes |b| > 20° in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error δ mz′ < 0.2 and a color i′ ? z′ < 0.6 (to first eliminate the M-type stars). For the selected sources, we have calculated the dependences χ2(z) for various spectral templates from the library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z = 0 and obtained a sample of quasars with photometric redshift estimates 2.75 < z phot < 5.5. The selection completeness of known quasars at z spec > 3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation (Δz = |z spec ? z phot|) is σ Δz /(1+z spec) = 0.07, while the outlier fraction is η = 9% when Δz/(1 + z спек.) > 0.2. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3 < z < 5.5 will allow the purity of this sample to be estimated more accurately.  相似文献   

2.
Two quasars SDSS J010013.02+280225.8 and J030642.51+185315.8 with redshifts z = 6.30 and z = 5.363 were recently discovered. Their apparent magnitudes in the standard cosmological model give the luminosities of Lbol ～ 4.3 × 1014L⊙ and Lbol ～ 3.4 × 1014L⊙. In the framework of modern concepts it is accepted that the energy release of quasars is provided by the accretion onto black holes with masses of 1.24 ± 0.19 × 1010M⊙ and 1.07 ± 0.27 × 1010M⊙. As within the standard cosmological model the ages of these objects are about one billion years, this creates serious difficulties for the scenario of formation of such objects. Here we interpret the ultra-high luminosities of quasars as the effect of lensing of their radiation by the foreground globular clusters or dwarf galaxies.  相似文献   

3.
Data on HII regions, molecular clouds, and methanol masers have been used to estimate the Sun’s distance from the symmetry plane z ⊙ and the vertical disk scale height h. Kinematic distance estimates are available for all objects in these samples. The Local-arm (Orion-arm) objects are shown to affect noticeably the pattern of the z distribution. The deviations from the distribution symmetry are particularly pronounced for the sample of masers with measured trigonometric parallaxes, where the fraction of Local-arm masers is large. The situation with the sample of HII regions in the solar neighborhood is similar. We have concluded that it is better to exclude the Local arm from consideration. Based on the model of a self-gravitating isothermal disk, we have obtained the following estimates from objects located in the inner region of the Galaxy (R ≤ R 0): z ⊙ = ?5.7 ± 0.5 pc and h 2 = 24.1 ± 0.9 pc from the sample of 639 methanol masers, z ⊙ = ?7.6±0.4 pc and h 2 = 28.6±0.5 pc from 878HII regions, z ⊙ = ?10.1 ± 0.5 pc and h 2 = 28.2 ± 0.6 pc from 538 giant molecular clouds.  相似文献   

4.
We present our B, V, Rc, and Ic observations of a \(3'.6 \times 3'\) field centered on the host galaxy of GRB 000926 (α2000.0=17h04m11s, \(\delta _{2000.0} = + 51^ \circ 47'9\mathop .\limits^{''} 8\)). The observations were carried out on the 6-m Special Astrophysical Observatory telescope using the SCORPIO instrument. The catalog of galaxies detected in this field includes 264 objects for which the signal-to-noise ratio is larger than 5 in each photometric band. The following limiting magnitudes in the catalog correspond to this limitation: 26.6 (B), 25.7 (V), 25.8 (R), and 24.5 (I). The differential galaxy counts are in good agreement with previously published CCD observations of deep fields. We estimated the photometric redshifts for all of the cataloged objects and studied the color variations of the galaxies with z. For luminous spiral galaxies with M(B)z～1.  相似文献   

5.
The X-ray luminosity function of distant (3 < z < 5.1) type 1 quasars has been measured. A sample of distant high-luminosity (1045 erg s?1 ≤ LX,2?10 < 7.5×1045 erg s?1 in the 2–10 keV energy band) quasars from the catalog by Khorunzhev et al. (2016) compiled from the data of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey and the Sloan Digital Sky Survey (SDSS) has been used. This sample consists of 101 sources. Most of them (90) have spectroscopic redshifts zspec ? 3; the remaining ones are quasar candidates with photometric redshift estimates zphot ? 3. The spectroscopic redshifts of eight sources have been measured with the BTA and AZT-33IK telescopes. Owing to the record sky coverage area (?250 sq. deg at X-ray fluxes ~10?14 erg s?1 cm?2 in the 0.5–2 keVband) from which the sample was drawn, we have managed to obtain reliable estimates of the space density of distant X-ray quasars with luminosities LX,2?10 > 2×1045 erg s?1 for the first time. Their comoving space density remains constant as the redshift increases from z = 3 to 5 to within a factor of 2. The power-law slope of the X-ray luminosity function of distant quasars at its bright end (above the break) has been reliably constrained for the first time. The range of possible slopes for the quasar luminosity and density evolution model is γ2 = 2.72 ?0.12 +0.19 ± 0.21, where initially the lower and upper boundaries of γ2 with the remaining uncertainty in the detection completeness of X-ray sources in SDSS and subsequently the statistical error of the slope are specified.  相似文献   

6.
We have obtained new estimates of the Sun’s distance from the symmetry plane Z ⊙ and the vertical disk scale height h using currently available data on stellar OB associations, Wolf–Rayet stars, HII regions, and Cepheids. Based on individual determinations, we have calculated the mean Z ⊙ = ?16 ± 2 pc. Based on the model of a self-gravitating isothermal disk for the density distribution, we have found the following vertical disk scale heights: h = 40.2 ± 2.1 pc from OB associations, h = 47.8 ± 3.9 pc from Wolf–Rayet stars, h = 48.4 ± 2.5 pc from HII regions, and h = 66.2 ± 1.6 pc from Cepheids. We have estimated the surface, Σ = 6 kpc?2, and volume, D(Z ⊙) = 50.6 kpc?3, densities from a sample of OB associations. We have found that there could be ～5000 OB associations in the Galaxy.  相似文献   

7.
The parameters of the cosmological model with cold dark matter and cosmological constant (ΛCDM model) were determined using three-year Wilkinson Microwave Anisotropy Probe observations of cosmic microwave background together with some data on the large-scale structure of the universe. The data cover scales from 1 to 10 000 Mpc. The best-fit ΛCDM model parameters were derived by minimizing the x 2 statistic with the use of the Levenberg-Markquardt approach (ΩΛ = 0.736 ± 0.065, Ωm = 0.238 ± 0.080, Ωb = 0.05 ± 0.011, h = 0.68 ± 0.09, σ8 = 0.73 ± 0.08, and n s = 0.96 ± 0.015). The ΛCDM model with these parameters is shown to agree well with the angular power spectrum of cosmic microwave background temperature fluctuations and with the density perturbation power spectra estimated from spatial distributions of galaxies and rich clusters of galaxies as well as from the statistics of the Ly α absorption lines in the spectra of distant quasars. The accord between the model large-scale structure characteristics and the observed ones is analyzed, and conceivable factors causing appreciable discrepancies between some characteristics are discussed.  相似文献   

8.
Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto–Nagai expressions. The Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen–Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ ⊙ = 0.1 M ⊙ pc?3 and the force K z =1.1/2πG = 77 M ⊙ pc?2 acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M G (R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 1012 M ⊙, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, M G (R ≤ 200 kpc) = (1.45 ±0.30)× 1012 M ⊙, M G (R ≤ 200 kpc) = (1.29± 0.14)× 1012 M ⊙ at γ = 6.3, and the smallest value has been found in model II, M G (R ≤ 200 kpc) = (0.61 ± 0.12) × 1012 M ⊙. In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is M G (R ≤ 200 kpc) = (0.75 ± 0.19) × 1012 M ⊙. A comparative analysis with the models by Irrgang et al. (2013), including those using the integration of orbits for the two globular clusters NGC 104 and NGC 1851 as an example, has been performed. The third model is shown to have subjected to a significant improvement.  相似文献   

9.
We consider stars with radial velocities, proper motions, and distance estimates from the RAVE4 catalogue. Based on a sample of more than 145 000 stars at distances r < 0.5 kpc, we have found the following kinematic parameters: \({\left( {U,{\kern 1pt} V,{\kern 1pt} W} \right)_ \odot }\) = (9.12, 20.80, 7.66) ± (0.10, 0.10, 0.08) km s?1, Ω0 = 28.71 ± 0.63 km s?1 kpc?1, and Ω0 ’ = ?4.28 ± 0.11 km s?1 kpc?2. This gives the linear rotation velocity V 0 = 230 ± 12 km s?1 (for the adopted R 0 = 8.0 ± 0.4 kpc) and the Oort constants A = 17.12 ± 0.45 km s?1 kpc?1 and B = ?11.60 ± 0.77 km s?1 kpc?1. The 2D velocity distributions in the UV, UW, and VW planes have been constructed using a local sample, r < 0.25 kpc, consisting of ~47 000 stars. A difference of the UV velocity distribution from the previously known ones constructed from a smaller amount of data has been revealed. It lies in the fact that our distribution has an extremely enhanced branch near the Wolf 630 peak. A previously unknown peak at (U, V) = (?96, ?10) km s?1 and a separate new feature in the Wolf 630 stream, with the coordinates of its center being (U, V) = (30, ?40) km s?1, have been detected.  相似文献   

10.
The results of a comprehensive analysis of continuous radio spectra of a sample of Gigahertz-Peaked Spectrum (GPS) sources are reported. The sources are selected from a flux-density-complete sample (S ν ≥ 200 mJy at 4.8 or 5 GHz) using multifrequency measurements of the RATAN-600 radio telescope and data from the CATS astrophysical catalogs support system. The analysis revealed a very small number (1–2%) of “classical” GPS objects, which is significantly less than the expected fraction of 10%. GPS galaxies are found to have narrower and steeper radio spectra than quasars. The low-frequency part of the spectrum is seen to become steeper with increasing redshift. Galaxies and quasars at the same z have comparable angular sizes, whereas their luminosities may differ by one order of magnitude. At large redshifts there is a deficit of objects with low (several GHZ) peak frequencies. The number of GPS galaxies decreases sharply with redshift, and most of them are found at z between 0.01 and 1.81. GPS quasars are found at large redshifts, from 0.11 to 3.99. A quarter of the sample consists of blazars whose spectra may temporarily have a convex shape when the object is in active state.  相似文献   

11.
Based on observations of SN 1999em, we determined the physical parameters of this supernova using hydrodynamic calculations including nonequilibrium radiative transfer. Taking the distance to SN 1999em estimated by the expanding photosphere method (EPM) to be D = 7.5 Mpc, we found the parameters of the presupernova: radius R = 450R⊙, mass M = 15M⊙, and explosion energy E = 7 × 1050 erg. For the distance D = 12 Mpc determined from Cepheids, R, M, and E must be increased to the following values: R = 1000R⊙, M = 18M⊙, and E = 1051 erg. We show that one cannot restrict oneself to using the simple analytical formulas relating the supernova and presupernova parameters to obtain reliable parameters for type-IIP presupernovae.  相似文献   

12.
Based on data from the Two-Micrometer All-Sky Survey (2MASS), we analyzed the infrared properties of 451 Local-Volume galaxies at distances D ≤ 10 Mpc. We determined the K-band luminosity function of the galaxies in the range of absolute magnitudes from ?25m to ?11m. The local luminosity density within 8 Mpc is 6.8 × 108L⊙ Mpc?3, a factor of 1.5 ± 0.1 higher than the global mean K-band luminosity density. We determined the ratios of the virial mass to the K-band luminosity for nearby groups and clusters of galaxies. In the luminosity range from 5 × 1010 to 2 × 1013L⊙, the dependence log(M/LK) ∝ (0.27 ± 0.03) log LK with a dispersion of ～0.1 comparable to the measurement errors of the masses and luminosities of the systems of galaxies holds for the groups and clusters of galaxies. The ensemble-averaged ratio, 〈M/LK〉 ? (20–25) M⊙/L⊙, was found to be much smaller than the expected global ratio, (80–90)M⊙/L⊙, in the standard model with Ωm = 0.27. This discrepancy can be eliminated if the bulk of the dark matter in the Universe is not associated with galaxies and their systems.  相似文献   

13.
We have identified 22 galaxies with photometric redshifts zph=5–7 in the northern and southern Hubble Space Telescope deep fields. An analysis of the images of these objects shows that they are asymmetric and very compact (～1 kpc) structures with high surface brightness and absolute magnitudes of MB≈?20m. The average spectral energy distribution for these galaxies agrees with the distributions for galaxies with active star formation. The star formation rate in galaxies with zph=5–7 was estimated from their luminosity at λ=1500 Å to be ~30 M⊙yr?1. The spatial density of these objects is close to the current spatial density of bright galaxies. All the above properties of the distant galaxies considered are very similar to those of the so-called Lyman break galaxies (LBGs) with z ～ 3–4. The similarity between the objects considered and LBGs suggests that at z ～6, we observe the progenitors of present-day galaxies that form duringmergers of protogalactic objects and that undergo intense starbursts.  相似文献   

14.
We present the results of optical spectroscopy for 19 quasar candidates at photometric redshifts z phot ? 3, 18 of which enter into the Khorunzhev et al. (2016) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for a quasi-random sample of new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. Fourteen of the 18 candidates actually have turned out to be quasars; 10 of them are at spectroscopic redshifts z spec > 3. The high purity of the sample of new candidates suggests that the purity of the entire K16 catalog of quasars is probably 70–80%. One of the most distant (z spec = 5.08) optically bright (i′ ? 21) quasars ever detected in X-ray surveys has been discovered.  相似文献   

15.
We provide our estimates of the intensity of the gamma-ray emission with an energy near 0.1 TeV generated in intergalactic space in the interactions of cosmic rays with background emissions. We assume that the cosmic-ray sources are pointlike and that these are active galactic nuclei. The following possible types of sources are considered: remote and powerful ones, at redshifts up to z = 1.1, with a monoenergetic particle spectrum, E = 1021 eV; the same objects, but with a power-law particle spectrum; and nearby sources at redshifts 0 < z ≤ 0.0092, i.e., at distances no larger than 50 Mpc also with a power-law particle spectrum. The contribution of cosmic rays to the extragalactic diffuse gammaray background at an energy of 0.1 TeVhas been found to depend on the type of sources or, more specifically, the contribution ranges from f ? 10?4 to f ≈ 0.1, depending on the source model. We conclude that the data on the extragalactic background gamma-ray emission can be used to determine the characteristics of extragalactic cosmic-ray sources, i.e., their distances and the pattern of the particle energy spectrum.  相似文献   

16.
The apparatus of a correlation gamma function is used to analyze a sample of 2dFGRS galaxies. We suggest a modified gamma-function algorithm with nonintersecting working spheres, which ensures that the counts are independent at each step. The method of nonintersecting spheres has revealed a change in the regime of clustering (a break of the gamma function) on a scale of 10–16h?1 Mpc (H0 = 65 km s?1 Mpc?1). The standard method yields a scale of 30h?1 Mpc. An artificial distribution is used as an example to show that, in some cases, the modified algorithm is more responsive to a mixture of distributions with various properties than the standard method.  相似文献   

17.
We investigate the variation of the fraction of galaxies with suppressed star formation (MK < ?21 . m 5) and early-type galaxies (fracE) of the “red sequence” along the projected radius in six galaxy clusters:Coma (A1656), A1139, and A1314 in the Leo supercluster region (z ≈ 0.037) and A2040, A2052, A2107 in the Hercules supercluster region (z ≈ 0.036). According to SDSS (DR10) data, fracE is the highest in the central regions of galaxy clusters and it is, on the average, equal to 0.62 ± 0.03, whereas in the 2–3R/R200c interval and beyond the Rsp ≈ 0.95 ± 0.04 R200m radius that we inferred from the observed profile fracE is minimal and equal to 0.25 ± 0.02. This value coincides with the estimate fracE = 0.24 ± 0.01 that we inferred for field galaxies located between the Hercules and Leo superclusters at the same redshifts. We show that the fraction of galaxies with suppressed star formation decreases continuously with cluster radius from 0.87 ± 0.02 in central regions down to 0.43 ± 0.03 in the 2–3 R/R200c interval and beyond Rsp, but remains, on the average, higher than 26% than the corresponding fraction for field objects. This decrease is especially conspicuous in the galaxy mass interval log M* [M⊙] = 9.5–10. We found that galaxies with ongoing star formation have average clustercentric distances 1.5–2.5 R/R200c and that their radial-velocity dispersions are higher than those of galaxies with suppressed star formation.  相似文献   

18.
Highly accurate observations of 116 asteroids are used to determine the orientation of the Hipparcos frame with respect to the reference frames of the DE403/LE403 and DE405/LE405 majorplanet ephemerides. These observations include the photographic observations of 15 asteroids obtained as part of the programs for observing selected asteroids and reduced to the Hipparcos frame using dependences, the space observations of 48 asteroids obtained by the Hipparcos satellite, and the presentday observations of 116 asteroid performed in the frame of the ACT catlog. The total number of observations used is more than 50 000 in the interval 1949–2007. Processing this series has yielded the following estimates of the orientation parameters: ω x = 0.12 ± 0.08 mas yr?1, ω y = 0.66 ± 0.09 mas yr?1, and ω z = ?0.56 ± 0.16 mas yr?1. This rotation may be attributable to a peculiarity of the transition from the reference frame of the DE200/LE200 ephemerides to that of DE403/LE403 ephemerides (since October 1, 1988, to J2000) that consists in the the assumption that the former reference frame has no rotation relative to the ICRF.  相似文献   

19.
We measured the radial velocity of the star θ1 Ori D from IUE spectra and used published observations. Based on these data, we determined the period of its radial-velocity variations, P=20.2675±0.0010 days, constructed the phase radial-velocity curve, and solved it by least squares. The spectroscopic orbital elements were found to be the following: the epoch of periastron passage Ep=JD 2430826.6±0.1, the system's center-of-mass velocity /Gg=32.4±1.0 km s?1, K=14.3±1.5 km s?1, Ω=3.3±0.1 rad, e=0.68±0.09, a1 sin i = 3 × 1010 km, and f1 = 0.0025M⊙. Twice the period, P=40.528±0.002 days, is also consistent with the observations.  相似文献   

20.
The eclipse observations were performed at the Laboratory of Radio Astronomy of the CrAO in Katsiveli with stationary instrumentation of the Solar Patrol at wavelengths of 10.5 and 12.0 cm. The data obtained were used to determine the brightness temperature of the undisturbed Sun at solar activity minimum between 11-year cycles 23 and 24: T d10.5 = (43.7 ± 0.5) × 103 K at 10.5 cm and T d12.0 = (51.8 ± 0.5) × 103 K at 12.0 cm. The radio brightness distribution above the limb group of sunspots NOAA 0866 was calculated. It shows that at both wavelengths the source consisted of a compact bright nucleus about 50 × 103 km in size with temperatures T b10.5 = 0.94 × 106 K and T b12.0 = 2.15 × 106 K located, respectively, at heights h 10.5 = 33.5 × 103 km and h 12.0 = 43.3 × 103 km above the sunspot and an extended halo with a temperature T b = (230–300) × 103 K stretching to a height of 157 × 103 km above the photosphere. The revealed spatial structure of the local source is consistent with the universally accepted assumption that the radiation from the bright part of the source is generated by electrons in the sunspot magnetic fields at the second-third cyclotron frequency harmonics and that the halo is the bremsstrahlung of thermal electrons in the coronal condensation forming an active region. According to the eclipse results, the electron density near the upper boundary of the condensation was N e ≈ 2.3 × 108 cm?3, while the optical depth was τ ≈ 0.1 at an electron temperature T e ≈ 106 K. Thus, the observations of the March 29, 2006 eclipse have allowed the height of the coronal condensation at solar activity minimum to be experimentally determined and the physical parameters of the plasma near its upper boundary to be estimated.  相似文献   

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