The local environmental dependence of properties of Luminous Red Galaxies (LRGs) from the SDSS data release 6 (SDSS6)

Using the Luminous Red Galaxy (LRG) sample of the SDSS Data Release 6, we investigate the dependence of LRG properties on the local environment. For each LRG, the local three-dimensional density within the distance to the 5th nearest galaxy is calculated. It turns out that there is no strong local environmental dependence of LRG morphologies, and that other galaxy properties do not present significant dependence on the local environment. We further calculate the local three-dimensional galaxy density within the distance to the 10th nearest galaxy, and find that results are similar to those for local density within the distance to the 5th nearest galaxy. Published in Astrofizika, Vol. 51, No. 2, pp. 189–200 (May 2008).     

Connecting global to local parameters in barred galaxy models

We present connections between global and local parameters in a realistic dynamical model, describing motion in a barred galaxy. Expanding the global model in the vicinity of a stable Lagrange point, we find the potential of a two-dimensional perturbed harmonic oscillator, which describes local motion near the centre of the global model. The frequencies of oscillations and the coefficients of the perturbing terms are not arbitrary but are connected to the mass, the angular rotation velocity, the scale length and the strength of the galactic bar. The local energy is also connected to the global energy. A comparison of the properties of orbits in the global and local potential is also made.     

The UKIRT Infrared Deep Sky Survey ZY JHK photometric system: passbands and synthetic colours

We present a statistical study of a very large sample of H  ii galaxies taken from the literature. We focus on the differences in several properties between galaxies that show the auroral line [O  iii ]λ4363 and those that do not present this feature in their spectra. It turns out that objects without this auroral line are more luminous, are more metal-rich and present a lower ionization degree. The underlying population is found to be much more important for objects without the [O  iii ]λ4363 line, and the effective temperature of the ionizing star clusters of galaxies not showing the auroral line is probably lower. We also study the subsample of H  ii galaxies whose properties most closely resemble the properties of the intermediate-redshift population of luminous compact blue galaxies (LCBGs). The objects from this subsample are more similar to the objects not showing the [O  iii ]λ4363 line. It might therefore be expected that the intermediate- redshift population of LCBGs is powered by very massive, yet somewhat aged, star clusters. The oxygen abundance of LCBGs would be greater than the average oxygen abundance of local H  ii galaxies.     

Mesogranulation and Turbulence in Photospheric Flows

Below the scale of supergranules we find that cellular flows are present in the solar photosphere at two distinct size scales, approximately 2 Mm and 4 Mm, with distinct characteristic times. Simultaneously present in the flow is a non-cellular component, with turbulent scaling properties and containing 30% of the flow energy. These results are obtained by means of wavelet spectral analysis and modeling of vertical photospheric motions in a 2-hour sequence of 120 SOHO/MDI, high-resolution, Doppler images near disk center. The wavelets permit detection of specific local flow patterns corresponding to convection cells.     

Turbulent stresses as a function of shear rate in a local disk model

We present local numerical models of accretion disk turbulence driven by the magnetorotational instability with varying shear rate. The resulting turbulent stresses are compared with predictions of a closure model in which triple correlations are modelled in terms of quadratic correlations. This local model uses five nondimensional parameters to describe the properties of the flow. We attempt to determine these closure parameters for our simulations and find that the model does produce qualitatively correct behaviour. In addition, we present results concerning the shear rate dependency of the magnetic to kinetic energy ratio. We find both the turbulent stress ratio and the total stress to be strongly dependent on the shear rate (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The hot and cold spots in five-year WMAP data

We present an extensive frequentist analysis of the one-point statistics (number, mean, variance, skewness and kurtosis) and two-point correlation functions determined for the local extrema of the cosmic microwave background temperature field observed in five-years of Wilkinson Microwave Anisotropy Probe ( WMAP ) data. Application of a hypothesis test on the one-point statistics indicates a low variance of hot and cold spots in all frequency bands of the WMAP data. The consistency of the observations with Gaussian simulations of the best-fitting cosmological model is rejected at the 95 per cent confidence level outside the WMAP KQ75 mask and the Northern hemispheres in the Galactic and ecliptic coordinate frames. We demonstrate that it is unlikely that residual Galactic foreground emission contributes to the observed non-Gaussianities. However, the application of a high-pass filter that removes large angular scale power does improve the consistency with the best-fitting cosmological model.
Two-point correlation functions of the local extrema are calculated for both the temperature pair product [temperature–temperature (T–T)] and spatial pair-counting [point–point (P–P)]. The T–T observations demonstrate weak correlation on scales below  20°  and lie completely below the lower 3σ confidence region once various temperature thresholds are applied to the extrema determined for the KQ75 mask and northern sky partitions. The P–P correlation structure corresponds to the clustering properties of the temperature extrema, and provides evidence that it is the large angular-scale structures, and some unusual properties thereof, that are intimately connected to the properties of the hot and cold spots observed in the WMAP five-year data.     

Modelling ionized gas and stellar emissions in starburst components

With objectives to model star formation in radio galaxies, we present results of a starburst model, built by coupling the two codes PÉGASE and CLOUDY. Continuum and emission line data are used to derive the properties of a sample of local starbursts. Data are well reproduced with a new relation between the ionization parameter and the metallicity. Colors and H_α equivalent widths indicate that: (i) an underlying stellar population is needed, and (ii) burst ages span the range [0, 6] Myr.     

Dense molecular gas in a sample of LIRGs and ULIRGs: The low-redshift connection to the huge high-redshift starbursts and AGNs

The sample of nearby LIRGs and ULIRGs for which dense molecular gas tracers have been measured is building up, allowing for the study of the physical and chemical properties of the gas in the variety of objects in which the most intense star formation and/or AGN activity in the local universe is taking place. This characterisation is essential to understand the processes involved, discard others and help to interpret the powerful starbursts and AGNs at high redshift that are currently being discovered and that will routinely be mapped by ALMA. We have studied the properties of the dense molecular gas in a sample of 17 nearby LIRGs and ULIRGs through millimeter observations of several molecules (HCO⁺, HCN, CN, HNC and CS) that trace different physical and chemical conditions of the dense gas in these extreme objects. In this paper we present the results of our HCO⁺ and HCN observations. We conclude that the very large range of measured line luminosity ratios for these two molecules severely questions the use of a unique molecular tracer to derive the dense gas mass in these galaxies.     

The evolution of the cluster X-ray scaling relations in the Wide Angle ROSAT Pointed Survey sample at 0.6 < z < 1.0

The X-ray properties of a sample of 11 high-redshift  (0.6 < z < 1.0)  clusters observed with Chandra and/or XMM–Newton are used to investigate the evolution of the cluster scaling relations. The observed evolution in the normalization of the   L – T , M – T , M _g– T   and M – L relations is consistent with simple self-similar predictions, in which the properties of clusters reflect the properties of the Universe at their redshift of observation. Under the assumption that the model of self-similar evolution is correct and that the local systems formed via a single spherical collapse, the high-redshift L – T relation is consistent with the high- z clusters having virialized at a significantly higher redshift than the local systems. The data are also consistent with the more realistic scenario of clusters forming via the continuous accretion of material.
The slope of the L – T relation at high redshift  ( B = 3.32 ± 0.37)  is consistent with the local relation, and significantly steeper than the self-similar prediction of   B = 2  . This suggests that the same non-gravitational processes are responsible for steepening the local and high- z relations, possibly occurring universally at   z ≳ 1  or in the early stages of the cluster formation, prior to their observation.
The properties of the intracluster medium at high redshift are found to be similar to those in the local Universe. The mean surface-brightness profile slope for the sample is  β= 0.66 ± 0.05  , the mean gas mass fractions within   R _{2500( z )}  and   R _{200( z )}  are  0.069 ± 0.012  and  0.11 ± 0.02  , respectively, and the mean metallicity of the sample is  0.28 ± 0.11 Z_⊙  .     

Quantum cosmology

The newest developments in the investigation of redshift quantization and variability are summarized and several approaches to cosmological models consistent with aspects of the data are discussed. The periodicities present when redshifts are referred to the Cosmic Background Radiation rest frame appear to be very precisely described by a series of period-doubling sequences based upon the ninth-root of 2 times the speed of light. Several examples of redshift quantization and variability are discussed to illustrate the periods, the CBR association and the dependence upon galaxy properties. Possible cosmological models involving properties of time, including a form of three-dimensional time and possible time networks, are introduced. Such models appear to have the potential to admit quantized and variable redshifts while remaining consistent with local continuous physical theory.     

Operator manifold approach to geometry and particle physics

The question that guides our discussion ishow did the geometry and particles come into being? To explore this query the present theory reveals primordial deeper structures underlying fundamental concepts of contemporary physics. We begin with a drastic revision of a role of local internal symmetries in phys ical concept of curved geometry. Under the reflection of fields and their dynamics from Minkowski space to Riemannian a standard gauge principle of local internal symmetries was generalized. The gravitation gauge group is proposed, which was generated by hidden local internal symmetries. In all circumstances, it seemed to be of the most importance for understanding of physical nature of gravity. Last two parts of this paper address to the question of physical origin of geometry and basic concepts of particle physics such as the fundamental fields of quarks with the spins and various quantum numbers, internal symmetries and so forth; also four basic principles of Relativity, Quantum, Gauge and Color Confinement, which are, as it was proven, all derivative and come into being simultaneously. The substance out of which the geometry and particles are made is a set of new physical structures —the goyaks, which are involved into reciprocal linkage establishing processes. The most promising aspect of our approach so far is the fact that many of the important anticipated properties, basic concepts and principles of particle physics are appeared quite naturally in the framework of suggested theory.     

The isolated dSph galaxy KKs3 in the local Hubble flow

We present SALT spectroscopy of a globular cluster in the center of the nearby isolated dSph galaxy KKs3 situated at a distance of 2.12 Mpc. Its heliocentric radial velocity is 316 ± 7 km s^–1 that corresponds to V_LG = 112 km s^–1 in the Local Group (LG) reference frame. We use its distance and velocity along with the data on other 35 field galaxies in the proximity of the LG to trace the local Hubble flow. The following basic properties of the local field galaxies are briefly discusse: morphology, absolute magnitudes, average surface brightnesses, specific star formation rates, and hydrogen mass‐to‐stellar mass ratios. Surprisingly, the sample of the neighboring isolated galaxies displays no signs of compression under the influence of the expanding Local Void. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dust-induced chemical differentiation in dense regions

Dust grains respond to the physical and chemical conditions of the interstellar region in which they are embedded. The interaction produces an extinction curve which depends on the local environment and on the past history of the dust grains. In this work we present a theoretical study of the effects of radial variations of dust extinction properties on gas-phase chemistry in spherical core–halo clouds. We use observational constraints on the variation range of the extinction curve, and we analyse if the degree of dust environmental processing could be reflected by chemical signatures in the gas-phase molecular concentrations. The results of this work show that significant variations in the photodestruction rates and in the thermal profile of the cloud might induce chemical patterns otherwise excluded in the standard dense-cloud chemistry. Some discrepancies between observations and theoretical provisions are discussed in the light of the present results.     

On the Alignment of T Tauri Stars with the Local Magnetic Field in the Taurus Molecular Cloud Complex

Magnetic field is believed to play an important role in the collapse of a molecular cloud. In particular, due to the properties of magnetic forces, collapse should be easier along magnetic field lines. This is supported by the large-scale sheet-like structures observed in the Taurus giant molecular cloud for instance. Here we investigate whether such a preferred orientation for collapse is present at a much smaller scale, that of individual objects, i.e., about 100AU. We use recent high-angular resolution images of T Tauri stars located in the Taurus star-forming region to find the orientation of the symmetry axis of each star+jet+disk system and compare it with that of the local magnetic field. We find that (i) T Tauri stars that are associated to a jet or an outflow are generally oriented parallel to the magnetic field, as previously demonstrated. More surprising, given our current knowledge of these objects, we also find that (ii) T Tauri stars that are not at present believed to be associated to a jet or an outflow are oriented very differently, i.e., mostly perpendicular to the magnetic field. We present some implications of this puzzling new result.     

On the local magnetorotational instability of astrophysical jets

We present the local linear stability analysis of rotating jets confined by a toroidal magnetic field. Under the thin flux tube approximation, we derive the equation of motion for slender magnetic flux tubes. In addition to the terms responsible for the conventional instability of the toroidal magnetic field, a term related to the magnetic buoyancy and a term corresponding to the differential rotation become relevant for the stability properties. We find that the rigid rotation stabilizes while the differential rotational destabilizes the jet in a way similar to the Balbus–Hawley instability. Within the frame of our local analysis, we find that if the azimuthal velocity is of the order of or higher than the Alfvén azimuthal speed, the rigidly rotating part of the jet interior can be completely stabilized, while the strong shearing instability operates in the transition layer between the rotating jet interior and the external medium. This can explain the limb-brightening effect observed in several jets. However, it is still possible to find jet equilibria that are stable all across the jet, even in the presence of differential rotation. We discuss observational consequences of these results.     

Generalized analytical models of Syrovatskii’s current sheet

Two-dimensional stationary magnetic reconnection models that include a thin Syrovatskii-type current sheet and four discontinuous magnetohydrodynamic flows of finite length attached to its endpoints are considered. The flow pattern is not specified but is determined from a self-consistent solution of the problem in the approximation of a strong magnetic field. Generalized analytical solutions that take into account the possibility of a current sheet discontinuity in the region of anomalous plasma resistivity have been found. The global structure of the magnetic field in the reconnection region and its local properties near the current sheet and attached discontinuities are studied. In the reconnection regime in which reverse currents are present in the current sheet, the attached discontinuities are trans-Alfvénic shock waves near the current sheet endpoints. Two types of transitions from nonevolutionary shocks to evolutionary ones along discontinuous flows are shown to be possible, depending on the geometrical model parameters. The relationship between the results obtained and numerical magnetic reconnection experiments is discussed.     

An infrared study of the double nucleus in NGC 3256

We present new resolved near- and mid-infrared (mid-IR) imaging and N -band spectroscopy of the two nuclei in the merger system NGC 3256, the most IR luminous galaxy in the nearby Universe. The results from the spectral energy distribution fit to the data are consistent with previous estimates of the amount of obscuration towards the nuclei and the nuclear star formation rates. However, we also find substantial differences in the infrared emission from the two nuclei which cannot be explained by obscuration alone. We conclude that the northern nucleus requires an additional component of warm dust in order to explain its properties. This suggests that local star-forming conditions can vary significantly within the environment of a single system.     

Tracing the warm–hot intergalactic medium in the local Universe

We present a simple method for tracing the spatial distribution and predicting the physical properties of the Warm–Hot Intergalactic Medium (WHIM), from the map of galaxy light in the Local Universe. Under the assumption that biasing is local and monotonic we map the  ∼2 h ⁻¹ Mpc  smoothed density field of galaxy light into the mass-density field, from which we infer the spatial distribution of the WHIM in the Local Supercluster. Taking into account the scatter in the WHIM density–temperature and density–metallicity relation, extracted from the z = 0 outputs of high-resolution and large-box-size hydrodynamical cosmological simulations, we are able to quantify the probability of detecting WHIM signatures in the form of absorption features in the X-ray spectra, along arbitrary directions in the sky. To illustrate the usefulness of this semi-analytical method we focus on the WHIM properties in the Virgo cluster region.     

Local Environmental Dependence of Galaxy Properties in a Volume-Limited Sample of Main Galaxies

Using a volume-limited sample of Main Galaxies from SDSS Data Release 5,we investigate the dependence of galaxy properties on local environment.For each galaxy,a local three-dimensional density is calculated.We find that the galaxy morphological type depends strongly on the local environment:galaxies in dense environments have predominantly early type morphologies.Galaxy colors have only a weak dependence on the environment.This puts an important constraint on the process of galaxy formation.     

A possible method of determining the mass function of BL Lac

Discrete events with internally consistent properties are found in the light curve of the active galaxy BL Lac, which are consistant with the expected properties of stellar disruptions in standard loss-cone models of quasar energy generation. The amplitude distribution of events resembles the local mass distribution. It is argued that stochastic analysis of such active galaxy light curves may be a useful probe of the mass distributions in their centres.