Twenty-Seven-Day Variation of Galactic Cosmic Rays

Neutron monitor data observed at Climax (CL) and Huancayo/Haleakala (HU/HAL) have been used to calculate the amplitude A of the 27-day variation of galactic cosmic rays (CRs). The median primary rigidity of response, R _m, for these detectors encompasses the range 18 ≤R _m≤46 GV and the threshold rigidity R ₀ covers the range 2.97≤R ₀≤12.9 GV. The daily average values of CR counts have been harmonically analyzed for each Bartels solar rotation (SR) during the period 1953 – 2001. The amplitude of the 27-day CR variation is cross-correlated to solar activity as measured by the sunspot number R, the interplanetary magnetic field (IMF) strength B, the z-component B _z of the IMF vector, and the tilt angle ψ of the heliospheric current sheet (HCS). It is anticorrelated to the solar coronal hole area (CHA) index as well as to the solar wind speed V. The wind speed V leads the amplitude by 24 SRs. The amplitude of the 27-day CR variation is better correlated to each of the these parameters during positive solar polarity (A>0) than during negative solar polarity (A<0) periods. The CR modulation differs during A>0 from that during A<0 owing to the contribution of the z-component of the IMF. It differs during A ₁>0 (1971 – 1980) from that during A ₂>0 (1992 – 2001) owing to solar wind speed.     

Associated HI absorption in thez = 3.4 radio galaxy B2 0902 + 343 observed with the GMRT

We have made observations of the as sociated HI absorption of a high redshift radio galaxy 0902+34 atz = 3.395 with the Giant Meterwave Radio Telescope in the 323 ± 1 MHz band. We find a narrow absorption line with a flux density of 11.5 mJy at a redshift of 3.397 consistent with that observed by Usonet al. (1991), Briggset al. (1993) and de Bruyn (1996). A weak broad absorption feature reported by de Bruyn (1996) has not been detected in our observations. We also place an upper limit of 4mJy(2σ) on emission line strength at the position where Usonet al. (1991) claimed to have found a narrow emission line.     

Effects of the Polarity States of the Heliospheric Magnetic Field and Particle Drifts in Cosmic Radiation

Forbush decrease (FD) events recorded at the ground-based neutron monitors (NMs) during the period 1961 – 1999, have been selected and recovery characteristic of these events have been analyzed. The average profile of FDs observed during different polarity states of the heliosphere is obtained by superposed epoch analysis separately for the periods 1961 – 1969 (A < 0), 1971 – 1979 (A > 0), 1981 – 1989 (A < 0) and 1991 – 1999 (A > 0). Hourly count rate of neutron monitors of different cut-off rigidities have been utilized. The results are compared with model predictions including drifts. No marked difference is observed in the amplitudes of FDs during A < 0 and A > 0. Rigidity spectrum fitted with a power law yields the values of spectral exponent that are closer to values predicted by two-dimensional models including drifts. The recovery rate of FDs varies with the polarity of HMF and the rate is higher (recovery time smaller) during A > 0 than during A < 0 epoch, consistent with the model predictions including the drift effects in the HMF. This difference in recovery time of FDs during A > 0 and A < 0 polarity conditions provides experimental evidence that drift plays an important role in cosmic ray modulation.     

Evidence for chemical evolution in spectra of high redshift galaxies

Using a sample of 57 VLT FORS spectra in the redshift range 1.37< z < 3.40 and a comparison sample with 36 IUE spectra of local ( ) starburst galaxies we derive CIV equivalent width values and estimate metallicities of starburst galaxies as a function of redshift. Assuming that a calibration of the CIV equivalent widths in terms of the metallicity based on the local sample of starburst galaxies is applicable to high-z objects, we find a significant increase of the average metallicities from about 0.16 Z _⊙ at the cosmic epoch corresponding to z ≈ 3.2 to about 0.42 Z _⊙ at z ≈ 2.3. A significant further increase in metallicity during later epochs cannot be detected in our data. Compared to the local starburst galaxies our high-redshift objects tend to be overluminous for a given metallicity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cosmic vibration of the sun and quasar 3C 273

The hypothesis that some extragalactic objects pulsate with a period of P ₀ = 9600.606(12) s, which was first discovered in the Sun, is tested with data on quasar 3C 273. Observations of its rapid photometric variability were made by different observers in 1968–2005 within several spectral bands. At the 4σ confidence level, these data show that there is a period of 9600.624(18) s, which is consistent, within the error limits, with P ₀ (mean harmonic amplitude 0.006 B magnitude). Its independence from the redshift z is a sign of a cosmological origin of the P ₀ pulsation, which is sometimes understood as the “rhythm” of cosmos’ absolute time. This phenomenon is also shown to be deeply connected—via the Sanchez formula—to the fundamental constants of physics and cosmology. This refutes the standard Big Bang hypothesis and confirms the Steady State, c-free model of the Universe (c is the speed of light).     

Magnetic field of the young star RW Aur

Results of ourmeasurements of the longitudinal magnetic field B _z for the young star RWAur A are presented. B _z measured from the so-called narrow component of the He I 5876 line varies in the range from −1.47 ± 0.15 to +1.10 ± 0.15 kG. Our data are consistent with a stellar rotation period of }~5.6 days and the model of two hot spots with opposite magnetic field polarities spaced about 180° apart in longitude. Relative to the Earth, the spot with B _z < 0 lies in the hemisphere above the midplane of the accretion disk, while the spot with B _z > 0 is below the midplane. The upper limit for B _z (at the 3σ level) obtained by averaging all observations is 180 G for the photosphere and 220 and 230 G for the Hα and [OI] 6300 line formation regions, respectively. We have also failed to detect a field in the formation region of broad emission line components: the upper limit for B _z is 600 G. In two of 11 cases, we have detected a magnetic field in the formation region of the blue absorption wing of the Na I D doublet lines, i.e., in the wind from RW Aur A: B _z = −180 ± 50 and −810 ± 80 G. The radial velocity of the photospheric lines in RW Aur A averaged over all our observations is }~+10.5 km s⁻¹, i.e., a value lower than that obtained by Petrov et al. (2001) ten years earlier by 5.5 km s⁻¹. Therefore, we discuss the possibility that RW Aur is not a binary but a triple system.     

Scaling Properties of X-ray Clusters: The Chandra View

The study of X-ray clusters of galaxies, started 30 years ago, has revealed an increasing complexity in the thermodynamics of the X-ray emitting intracluster medium (ICM) as long as the sensitivity and the resolution of the X-ray satellites increased. At the same time, deep surveysdetected several, unexpected, high-z clusters. Here we focus on the Chandra observations of the most distant X-ray selected clusters (0.3 < z < 1.3), in order to constrain their thermodynamic evolution. The X-ray scaling properties show hints of negative evolution in the luminosity–temperature and M _gas–temperature relations, and a positive evolution in the entropy–temperature relation. We find that the mean iron abundance at 〈z〉 = 0.8 is Z _Fe = 0.25^+0.04 _−0.06 Z _⊙, and at 〈z〉 ∼ 1.2 is Z _Fe = 0.35^+0.06 _−0.05 Z _⊙, both measures consistent with no evolution with respect to the local value Z _Fe≃ 0.3 Z _⊙. These results can provide interesting constraints on the thermodynamics of the ICM at large look back times, pointing towards a redshift z ≳ 2 for the onset of non-gravitational processes.     

Distribution of stars perpendicular to the plane of the galaxy

We present here rigorous analytical solutions for the Boltzmann-Poisson equation concerning the distribution of stars above the galactic plane. The number density of stars is considered to follow a behaviour n(m,0) ∼H(m - m₀)m^−x, wherem is the mass of a star andx an arbitrary exponent greater than 2 and also the velocity dispersion of the stars is assumed to behave as < v²(m)> ∼ m^−θ the exponent θ being arbitrary and positive. It is shown that an analytic expression can be found for the gravitational field K_z, in terms of confluent hypergeometric functions, the limiting trends being K_z∼z for z →0, while K_z → constant for z → infinity. We also study the behaviour of < |z(m)|²>,i.e. the dispersion of the distance from the galactic disc for the stars of massm. It is seen that the quantity < |z(m)|²>∼ m^t-θ, for m→ t, while it departs significantly from this harmonic oscillator behaviour for stars of lighter masses. It is suggested that observation of < |z(m)|²> can be used as a probe to findx and hence obtain information about the mass spectrum.     

Statistics of WMAP ILC map temperature fluctuations towards distant radio galaxies

For 2442 galaxies of the catalog, compiled based on the NED, SDSS, and CATS survey data with redshifts z, > 0.3 we conducted an analysis of the amplitude of temperature fluctuations in the cosmic microwave background (CMB) in the points, corresponding to the direction to these objects. To this end, we used the ILC map from the WMAP mission seven-year data release. We have estimated the dipole component of the background and tested the hypothesis of Kashlinsky on the existence of a “dark bulk flow”, determined for the estimated dipole component of the CMB WMAP by the value of the CMB anisotropy in the direction to the clusters of galaxies. We show that the amplitude of this dipole T _max = 0.012mK is located within the σ interval, estimated by Monte Carlo simulations for the Gaussian fluctuations of the CMB signal in the ΛCDM model. The low amplitude of the dipole indicates that it is impossible to confirm this hypothesis from the WMAP data. In addition, we studied the statistics of the fluctuation amplitude of the microwave signal in the direction to radio galaxies. A weakening of the absolute value of the mean signal in the corresponding fields was discovered.     

Om diagnostic of dilaton dark energy with two-parameter ω in potential [1+(σ−A)2]e (−Bσ)

Based on a new geometric diagnostic method-Om, we consider a new independent-model parametrization . When we work in potential W _σ [1+(σ−A)²]e ^(−Bσ), we investigate the evolutional behavior of Om with respect to red-shift z and the influence of coupling parameter α on the trajectory of Om with respect to z. We get that phantom model of Dilaton dark energy can avoid the future singularity “Big Rip”. The numerical results give current value of EOS which fits the latest observational data WMAP5+BAO+SNe very well.     

Propagation of a burst of radiation in an expanding and recombining universe: Thomson scattering

The propagation of an instantaneous burst of nonpolarized isotropic radiation from the time of its onset at some redshift z ₀ to the time of its recording at the present epoch is considered within the framework of a flat cosmological model. Thomson (Rayleigh) scattering by free electrons is believed to be the only source of opacity. The spatial distributions of the mean (over the directions) radiation intensity as well as the angular distributions of the radiation intensity and polarization at various distances from the burst center have been constructed. The mean intensity profile normalized to the total number of photons emitted during the burst is shown to depend weakly on the initial conditions (the burst time z ₀, the width and shape of the initial radiation distribution) at fairly high z ₀ (≥1400). As regards the angular intensity and polarization distributions, they turn out to be rather narrow (3–10 arcmin), while the polarization can reach 70%. On average, the expected polarization can be about 15%.     

Study of the Cosmic Ray Diurnal Anisotropy During Different Solar and Magnetic Conditions

The pressure-corrected hourly counting rate data of four neutron monitor stations have been employed to study the variation of cosmic ray diurnal anisotropy for a period of about 50 years (1955–2003). These neutron monitors, at Oulu ( R _c = 0.78 GV), Deep River ( R _c = 1.07 GV), Climax ( R _c = 2.99 GV), and Huancayo ( R _c = 12.91 GV) are well distributed on the earth over different latitudes and their data have been analyzed. The amplitude of the diurnal anisotropy varies with a period of one solar cycle (∼11 years), while the phase varies with a period of two solar cycles (∼22 years). In addition to its variation on year-to-year basis, the average diurnal amplitude and phase has also been calculated by grouping the days for each solar cycle, viz. 19, 20, 21, 22, and 23. As a result of these groupings over solar cycles, no significant change in the diurnal vectors (amplitude as well as phase) from one cycle to other has been observed. Data were analyzed by arranging them into groups on the basis of the polarity of the solar polar magnetic field and consequently on the basis of polarity states of the heliosphere ( A > 0 and A < 0). Difference in time of maximum of diurnal anisotropy (shift to earlier hours) is observed during A < 0 (1970s, 1990s) polarity states as compared to anisotropy observed during A > 0 (1960s, 1980s). This shift in phase of diurnal anisotropy appears to be related to change in preferential entry of cosmic ray particles (via the helioequatorial plane or via solar poles) into the heliosphere due to switch of the heliosphere from one physical/magnetic state to another following the solar polar field reversal.     

Luminescence in Primordial Helium Lines at the Pre-recombination Epoch

The formation of luminescent subordinate He I lines by the absorption of radiation from a source in lines of the main He I series in an expanding Universe is considered. A burst of radiation in continuum is assumed to occur at some instant of time corresponding to redshift z₀. This radiation is partially absorbed at different z < z₀ in lines of the main He I series (different pumping channels) and then is partially converted into radiation in subordinate lines. If ν _ik is the laboratory transition frequency of some subordinate line emerging at some z, then at the present epoch its frequency will be ν = ν _ik /(1 + z). The quantum yield, i.e., the number of photons emitted in the subordinate line per initial excited atom, has been calculated for different z (and, consequently, for different ν). Several pumping channels have been considered. We show that the luminescent lines can be both emission and absorption ones; the same line can be an emission one for one of the pumping channels and an absorption one for another. For example, the 1s2s–1s2p (1S–1P*) line is an emission one for the 1s2–1s2p pumping and an absorption one for the 1s2–1s3p pumping. We show that in the frequency range 30–80 GHz the total quantum yield for the first and second of the above channels can reach +50 and ?50%, respectively.     

Galaxy Evolution from Deep Field Galaxy Counts

We present deep galaxy number counts and colours of K—band selected galaxy surveys. We argue that primeval galaxies are present within the survey data, but have remained unidentified. There are few objects with the colours of an L ^* elliptical galaxy at a redshift of z ≈ 1, in contradiction to standard luminosity evolution models. We present K—band photometry of the objects in a spectroscopic redshift survey selected at 21 < B < 22.5. The absolute K magnitudes of the galaxies are consistent with the no-evolution or pure luminosity evolution models. The excess faint blue galaxies seen in the B—band number counts at intermediate magnitudes are a result of a low normalization, and do not dominate the population until B ≈ 25. Extreme merging or excess dwarf models are not needed at z < 1. This revised version was published online in July 2006 with corrections to the Cover Date.     

Star‐forming galaxies observed with X‐shooter

In the last couple of decades hundreds of studies have explored the nature of star‐forming galaxies at different redshifts. This contribution focuses on X‐shooter observations of star‐burst galaxies at 0 < z < 6 from commissioning runs, science verification, and regular observations, and demonstrates the capability of the new instrument in this competitive field. Observations of gravitationally lensed galaxies show that X‐shooter has no limitation in the redshift desert (1.4 < z < 2) where the strong optical emission lines are shifted to the near‐IR region. Physical properties of galaxies, such as masses, metallicities, abundance ratios, and star formation rates can be derived from observations with relatively short integration times for faint galaxies. The simultaneous UV to near‐IR spectral coverage makes derivation of physical quantities more reliable because there are no differential slit losses as may occur when observations from different optical and near‐IR instruments are used. Over the entire redshift range, spectra of faint galaxies will allow us to better measure stellar ages and dominating ionisation sources compared to broad band spectral energy distribution measurements (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The redshift dependence of spectral index in powerful radio galaxies

We present and discuss in this paper the rest frame radio spectra (1–25 GHz) of a sample of fourteen radio galaxies atz >2 from the newly defined MRC/1Jy complete sample of 558 radio sources. These galaxies are among the most powerful radio sources known and range in luminosity from 1028-1028·8 watt Hz-1 at 1 GHz. We find that the median rest frame spectral index of this sample of galaxies atz >2 is significantly steeper than that of a matched luminosity sample of 3CRR galaxies which are at a much lower redshift (0.85 <z < 1.7). This indicates that spectral index correlates primarily with redshift, at least in the luminosity range considered here. The difference between the distributions of rest frame spectral curvatures for the two samples does not appear to be statistically significant. We suggest a new explanation for the steeper spectra of radio galaxies at high redshift involving steeper electron energy spectra at injection. Electron energy spectra are expected to steepen in a first-order Fermi acceleration process, at both non-relativistic and relativistic shock fronts, as the upstream fluid velocity decreases. This may well be the case at high redshifts: the hotter and denser circum-galactic medium at high redshifts could result in slower speeds for the hotspot and the jet material behind it. The smaller sizes of radio sources at higher redshifts provide support to this scenario. Since deceased.     

The characteristics of ion acoustic shock waves in non-Maxwellian plasmas with (G′/G)-expansion method

Korteweg-de-Vries-Burger (K-dVB) equation is derived for ion acoustic shock waves in electron-positron-ion plasmas. Electrons and positrons are considered superthermal and are effectively modeled by a kappa distribution in which ions are as cold fluid. The analytical traveling wave solutions of the K-dVB equation investigated, through the (G′/G)-expansion method. These traveling wave solutions are expressed by hyperbolic function, trigonometric functions are rational functions. When the parameters are taken special values, the shock waves are derived from the traveling waves. It is observed that the amplitude ion acoustic shock waves increase as spectral index κ and kinematic viscosity η _i,0 increases in which with increasing positron density β and electron temperature σ the shock amplitude decreases. Also, numerically the effect different parameters on the nonlinearity A and dispersive B terms and wave velocity V investigated.     

Clustering evolution between z=1 and today

We present results of an investigation of clustering evolution of field galaxies between a redshift of z ∼ 1 and the present epoch. The current analysis relies on a sample of ∼ 14000 galaxies in two fields of the COMBO 17 survey. The redshift distribution extends to z ∼ 1. The amplitude of the three-dimensional correlation function can be estimated by means of the projected correlation function w(r _p ). The validity of the deprojection was tested on the Las Campanas Redshift Survey (LCRS). In a flat cosmology with non-zero cosmological constant for bright galaxies (M _B ≤-18) the clustering growth is proportional to (1+z) ^-2. However, the measured clustering evolution clearly depends on Hubble type. While locally the clustering strength of early type galaxies is equal to that of the bright galaxies, at high redshifts they are much stronger clustered, and thus the clustering has to evolve much more slowly. This revised version was published online in August 2006 with corrections to the Cover Date.     

An observational constraint on the existence of proto-superclusters at z =3.3

Observations have been conducted using the Ooty Radio Telescope in order to place constraints on the evolutionary scenario leading to the formation of the present day superclusters. The experiment attempted to detect 21 cm emission from massive neutral hydrogen condensates at a redshift ofz = 3.3. In an Einstein de-Sitter universe with baryon density Ω = 0.05, about ten condensates were expected in the volume surveyed if superclusters, having H I masses ≃5 × 10₁₅ M _⊙, were the first objects to separate out of the Hubble expansion. The sensitivity of our experiment rules out the existence of these condensates atz = 3.3 unless their lifetimes are less than one-tenth the dispersion in their epoch of formation or the proto-superclusters subtend angles greater than 6 arcmin. The result indicates that superclusters form at z > 3.3 if indeed they were the first objects to condense out of the Hubble flow. An erratum to this article is available at .     

Redshift difference between emission and absorption lines of QSOs

Distribution of the redshift difference (z) between emission and absorption lines of QSOs is half-gaussian. Also, the quantity z increases with increase in emission line redshift (z _em). The correlation between the two quantities (z andz _em) is statistically significant. The interpretation of the results indicate that the co-moving density of absorbing clouds decreases with redshift and that the absorbing clouds are associated with the QSOs rather than completely unrelated intervening material.