Formation of the first stars and quasars

We examine various observable signatures of the first generation of stars and low-luminosity quasars, including the metal enrichment, radiation background, and dust opacity/emission that they produce. We calculate the formation history of collapsed baryonic halos, based on an extension of the Press-Schechter formalism, incorporating the effects of pressure and H₂-dissociation. We then use the observed C/H ratio at z=3 in the Lyman-α forest clouds to obtain an average the star formation efficiency in these halos. Similarly, we fit the efficiency of black-hole formation, and the shape of quasar light curves, to match the observed quasar luminosity function (LF) between z=2−4, and use this fit to extrapolate the quasar LF to faint magnitudes and high redshifts. To be consistent with the lack of faint point-sources in the Hubble Deep Field, we impose a lower limit of ∼ 75 km s⁻¹ for the circular velocities of halos harboring central black holes.We find that in a ΛCDM model, stars reionize the IGM at z_reion=9−13, and quasars at z=12. Observationally, z_reion can be measured by the forthcoming MAP and Planck Surveyor satellites, via the damping of CMB anisotropies by ∼10% on small angular scales due to electron scattering. We show that if reionization occurs later, at 5 ≲ z_reion ≲ 10, then it can be measured from the spectra of individual sources. We also find that the Next Generation Space Telescope will be able to directly image about 1–40 star clusters, and a few faint quasars, from z >10 per square arcminute. The amount of dust produced by the first supernovae has an optical depth of τ=0.1−1 towards high redshift sources, and the reprocessed UV flux of stars and quasars distorts the cosmic microwave background radiation (CMB) by a Compton y-parameter comparable to the COBE limit, y ∼ 1.5 × 10⁻⁵.     

Improvements in bottomside electron density definition in the Autoscala program

Some improvements introduced in the Autoscala program are presented. They include improvements in E valley modeling of the electron density profile N_e(h), and in the link between the E valley and bottom-side F regions. An abrupt variation in N_e(h) generated by the previous version of Autoscala under night conditions has been eliminated.A series of ionograms recorded by the Millstone Hill digisonde (42.6°, 288.5°) were automatically interpreted by the previous version of Autoscala and by the new one. Data from Incoherent Scatter Radar (ISR) were used to comparatively assess the performance of the two versions. For this purpose, the root mean square errors (RMSEs) of the N_e(h) provided by Autoscala were calculated relative to the corresponding values provided by ISR.A more accurate overall modeling of N_e(h) was achieved by the new Autoscala version (RMSE = 0.51 MHz for the new version against RMSE = 0.67 MHz for the previous one).     

XMM-Newton observations across the Cygnus Loop from northeastern rim to southwestern rim

We have observed the Cygnus Loop from the northeast (NE) to the southwest (SW) with XMM-Newton. We extracted spectra from 3′-spaced annular regions across the Loop and fitted them either with a one-kT_e-component non-equilibrium ionization (NEI) model or with two-kT_e-component NEI model. We found that the two-kT_e-component model yields significantly better fits in almost all the spectra than the one-kT_e-component model. Judging from the abundances, the high-kT_e-component in the two-temperature model must be fossil ejecta while the low-kT_e-component comes from the swept-up interstellar medium (ISM). The distributions of Ne, Mg, Si, and S for fossil ejecta appear to retain the onion-skin structure at the time of a supernova explosion, suggesting that significant overturning of the ejecta has not occurred yet. Comparing the relative abundances of fossil ejecta estimated for the entire Cygnus Loop with those from theoretical calculations for Type-II SN, the mass of the progenitor star is likely to be ∼13 M_⊙. The trends of the radial profiles of kT_e and emission integral for the swept-up ISM are adequately described by the Sedov model, suggesting that the swept-up ISM is concentrated in a shell-like structure. Comparing our data with the Sedov model, we found the ambient medium density to be ∼0.7 cm⁻³. Then, we estimated the total mass of the swept-up ISM and the age of the remnant to be ∼130 M_⊙ and 13,000 years, respectively. Note that if the explosion occurred within a stellar wind cavity, then the density in the cavity, the total swept-up mass in the cavity, and the age of the remnant are estimated to be ∼0.14 cm⁻³, ∼25 M_⊙, and ∼10,000 years, respectively.     

Convective motions in liquid metals for material processings. Numerical simulation of oscillation regimes and effect of rotation

The paper is concerned with the numerical simulation and the analysis of some kinds of flow regimes which can develop in Bridgman and Czochralski systems for material processings. The flows in the liquid phase are investigated considering two-dimensional and axisymmetric models. The time-dependent regimes were studied for a zero-Prandtl-number fluid layer confined inside a two-dimensional cavity of aspect ratio (length-to-height) A=4, involving a stress-free upper surface and submitted to a horizontal temperature gradient. The range of Grashof number was varied up to the conditions at which the flow goes from oscillatory to chaotic type behaviours. The combined influence of the temperature gradients and of the rotations of the crucible and of the seed/crystal was investigated for a Czochralski model. The axisymmetric regimes were studied for a Pr_m=0.015 liquid melt confined inside a cylindrical crucible of aspect ratio (height-to-radius) A_m=2, and coupled to a viscous encapsulant liquid layer (10<Pr_e<1200) of aspect ratio A_e=0.5. A number of steady and (transient) time-dependent flow patterns are identified.     

Nonlinear electromagnetic perturbations in a degenerate electron–positron plasma

Nonlinear propagation of fast and slow magnetosonic perturbation modes in an ultra-cold, degenerate (extremely dense) electron–positron (EP) plasma (containing non-relativistic, ultra-cold, degenerate electron and positron fluids) has been investigated by the reductive perturbation method. It is shown that due to the property of being equal mass of the plasma species (_me=_mp$m_e=m_p$, where _me$m_e$ and _mp$m_p$ are electron and positron mass, respectively), the degenerate EP plasma system supports the K-dV solitons which are associated with either fast or slow magnetosonic perturbation modes. It is also found that the basic features of the electromagnetic solitary structures, which are found to exist in such a degenerate EP plasma, are significantly modified by the effects of degenerate electron and positron pressures. The applications of the results in an EP plasma medium, which occurs in compact astrophysical objects, particularly in white dwarfs, have been briefly discussed.     

On the physical state in the narrow-line region of the classical Seyfert galaxy NGC 7469

Based on the spectrophotometric data, by decomposition of the observed continuum, the power - law continuum characteristics of the central source are obtained. The behaviour of both electron temperature T_e and density n_e in the Narrow - Line Region (NLR) of NGC 7469 is discussed on the thermal and ionization equilibria calculations. T_e in NLR of the Sy1 galaxies are higher than the Sy2 ones, and the possible explanation is the lack of the dense (n_e 10¹⁰ cm⁻³) zone close to the central source in the Sy2 galaxies.     

Medium resolution near-infrared spectra of the host galaxies of nearby quasars

We present medium resolution near-infrared host galaxy spectra of low redshift quasars, PG 0844+349$0844+349$ (z = 0.064), PG 1226+023$1226+023$ (z = 0.158), and PG 1426+015$1426+015$ (z = 0.086). The observations were done by using the Infrared Camera and Spectrograph (IRCS) at the Subaru 8.2 m telescope. The full width at half maximum of the point spread function was about 0.3 arcsec by operations of an adaptive optics system, which can effectively resolve the quasar spectra from the host galaxy spectra. We spent up to several hours per target and developed data reduction methods to reduce the systematic noises of the telluric emissions and absorptions. From the obtained spectra, we identified absorption features of Mg I (1.503 μm), Si I (1.589 μm) and CO (6-3) (1.619 μm), and measured the velocity dispersions of PG 0844+349$0844+349$ to be 132 ± 110 km s⁻¹ and PG 1426+015$1426+015$ to be 264 ± 215 km s⁻¹. By using an _MBH–σ$M_{\text{BH}}''–''\sigma$ relation of elliptical galaxies, we derived the black hole (BH) mass of PG 0844+349$0844+349$, log(_MBH/_M⊙)=7.7±5.5$\log (M_{\text{BH}}/M_{\odot })=7.7\pm 5.5$ and PG 1426+015,log(_MBH/_M⊙)=9.0±7.5$1426+015\text{,}\log (M_{\text{BH}}/M_{\odot })=9.0\pm 7.5$. These values are consistent with the BH mass values from broad emission lines with an assumption of a virial factor of 5.5.     

A possible redshift evolution of the time-lag and variability luminosity relations for long gamma-ray bursts

Several luminosity relations currently exist for long gamma-ray bursts (GRBs). Some were derived from the light curves; others were obtained from the spectra. In this study, we consider two of these luminosity relations: the time-lag, _τlag${\tau }_{\mathit{lag}}$, relation and the variability, V, relation and investigate their possible dependence on (or “evolution” with) the redshift, z.     

Energy conversion of the flare due to direct electric fields from the sheared reconnection

In this paper we present a new mechanism of the main energy conversion of the solar flare. Since a flare inducing prominence (flux tube) rises V_z ? 300 km s⁻¹, the plasmas below it cannot continuously eject with Alfvén speeds of V_A = 3000 km s⁻¹ but probably with V_z ≈ ±100 km s⁻¹. Plasma up and downflows with V_A will within a short duration be blocked between the chromosphere where reconnected flux tubes are piling up, and the slowly rising flux rope. Hence the Petschek slow shock mechanism is difficult to be realized as a major energy converting mechanism.     

Solar cycle effects upon the relationship of Ne and Te in the F-region

Employing Atmsophere Explorer-C measurements made in 1974, just prior to solar minimum, Brace and Theis /1/ demonstrated that a remarkably consistent inverse relationship existed between the electron density N_e and temperature T_e in the F-region. In this paper we use later data from AE-C, taken when solar activity was rising (1975–1978), and Dynamics Explorer-2 data taken at solar maximum (1981), to examine how the temperature and density relationship changes with solar activity. We find that the solar maximum T_e is a factor of two larger than the solar minimum T_e for the same values of N_e. T_e does not necessarily increase with solar activity, however, because N_e increases enough to approximately cancel the effect of higher solar extreme ultraviolet heating. We find that the effect of solar activity can be accounted for by a simple function of the F_10.7 cm index that multiplies the solar minimum equation of Brace and Theis /1/.     

Ionospheric electron temperature at solar maximum

Langmuir probe measurements made at solar maximum from the Dynamics Explorer-2 satellite in 1981 and 1982 are employed to examine the latitudinal variation of electron temperature, T_e, at altitudes between 300 and 400 km and its response to 27 day variations of solar EUV. Comparison of these data with T_e models based on the solar minimum measurements from Atmosphere Explorer-C suggest that the daytime T_e does not change very much during the solar cycle, except at low latitudes where an especially large 27 day variation occurs. The 27 day component decreases from about 7°/F10.7 unit at the equator to 3°/F10.7 unit at 851V 3 middle and higher latitudes. From these DE-2 measurements, and those from AE-C, we conclude that the daytime T_e near the F₂ peak is more responsive to short-term (daily) variations in F10.7 than to any longer term changes that may occur between solar minimum and solar maximum. To investigate this sensitivity of the dayside ionosphere to solar activity we employ the inverse relationship of T_e and N_e, that was found at solar minimum, to see if it can be used to order the T_e behaviour at solar maximum. We introduce a simple quadratic correction for the F10.7 influence on T_e based on the entire daytime AE-C and DE-2 data base between 300 and 400 km. Although this equation may be found useful, the systematic deviations of the DE-2 data suggest that the solar minimum model does not accurately describe the T_e-N_e relationships at solar maximum, at least above 300 km where the DE-2 measurements were made. Future work with this data base should attempt to see if such a relationship exists.     

Modelled ionospheric Te profiles at mid-latitudes for possible IRI application

The electron temperature (T_e) variation in the mid-latitude ionosphere at altitudes between 120 – 800 km has been modelled for various seasonal and solar-cycle conditions. The calculated electron temperatures are consistent with plasma densities and ion temperatures computed from a time-dependent ionospheric model. The T_e distribution can be represented by a subset of standard T_e profiles. T_e above 200 km is controlled by the magnetospheric heat flux into the ionosphere. For realistic values of the magnetospheric heat flux, the maximum electron temperature ranges from 3000 to 10,000 K at 800 km. The effect of increasing the heat flux is to increase the topside temperature but retain the profile shape. Hence, given a topside T_e observation and selection of an appropriate profile shape, the entire T_e distribution can be computed.     

An empirical model of electron temperature for low and middle latitudes in the 100–200 km height region

An empirical model of electron temperature (T_e) for low and middle latitudes is proposed in view of IRI. It is constructed on the basis of experimental data obtained at 100 to 200 km by probe and incoherent scatter methods. Below 150 km the model gives two T_e values: one from incoherent scatter data and another from probe measurements. The model can be used for all seasons for quiet geomagnetic conditions (Kp not greater 3) and at almost all levels of solar activity (F_10.7 between 70 and 200). It is presented in an analytical form that allows one to calculate T_e profiles for different latitudes, longitudes and at any season (day). Depending on geomagnetic latitude and solar zenith angle, electron temperature distributions are presented for two heights along with T_e profile variations during the day (at middle latitudes).     

Latitudinal variation of the topside electron temperature at different levels of solar activity

A database of electron temperature (T_e) measurements comprising of most of the available satellite measurements in the topside ionosphere is used for studying the solar activity variations of the electron temperature T_e at different latitudes, altitudes, local times and seasons. The T_e data are grouped into three levels of solar activity (low, medium, high) at four altitude ranges, for day and night, and for equinox and solstices. We find that in general T_e changes with solar activity are small and comparable in magnitude with seasonal changes but much smaller than the changes with altitude, latitude, and from day to night. In all cases, except at low altitude during daytime, T_e increases with increasing solar activity. But this increase is not linear as assumed in most empirical T_e models but requires at least a parabolic approximation. At 550 km during daytime negative as well as positive correlation is found with solar activity. Our global data base allows to quantify the latitude range and seasonal conditions for which these correlations occur. A negative correlation with solar activity is found in the invdip latitude range from 20 to 55 degrees during equinox and from 20 degrees onward during winter. In the low latitude (20 to −20 degrees invdip) F-region there is almost no change with solar activity during solstice and a positive correlation during equinox. A positive correlation is also observed during summer from 30 degrees onward.     

Determination of reconnected flux via remote sensing

Magnetic reconnection is one of the most fundamental processes in the magnetosphere. We present here a simple method to determine the essential parameters of reconnection such as reconnected flux and location of the reconnection site out of single spacecraft data via remote sensing. On the basis of a time-dependent reconnection model, the dependence of the reconnected flux on the magnetic field z-component B_z is shown. The integral of B_z over time is proportional to the reconnected flux and depends on the distance between the reconnection site and the actual position where B_z is measured. This distance can be estimated from analysis of magnetic field B_z data. We apply our method to Cluster measurements in the Earth’s magnetotail.     

Rotational constants of linear and/or bent Cn+1H and CnN(n = 1–6): A DFT study

The geometries, dipole moments, and rotational constants for the linear and/or bent cations, C_n+1H⁺ and C_nN⁺(n = 1–6), were studied by the B3LYP method with the modest basis sets. For C_nH⁺(n = odd; 3, 5, 7) and C_nN⁺(n = even; 2, 4, 6), the theoretical rotational constants (B_es) of closed-shell singlet C₃H⁺, C₅H⁺, C₇H⁺, CCN⁺, C₄N⁺, and C₆N⁺ were calculated to be about 11,244, 2420, 885.2, 11,970, 2439, and 880.8 MHz, respectively. By contrast, the triplets are stable than the corresponding singlets for C_nH⁺(n = odd; 2, 4, 6) and C_nN⁺(n = even; 3, 5) except CN⁺.     

The role of volcanic aerosols and relativistic electrons in modulating winter storm vorticity

Small changes in the vorticity of winter storms, responding to solar wind variations, are found in winters from 1957 to 2011, and are greater for winters with higher levels of stratospheric volcanic aerosols. Using 1993–2011 data, the response of the vorticity area index (VAI) is shown to be of larger amplitude when the days of minima in the relativistic electron flux (REF) precipitating from the radiation belts are used, instead of heliospheric current sheet (HCS) crossings, as key days in superposed epoch analyses. The HCS crossings mostly occur within a few days of the REF minima. The VAI is an objective measure of the area of high cyclonic vorticity, and for the present work is derived from ERA-40 and ERA-Interim reanalyses of global meteorological data. The VAI dependencies on the stratospheric aerosol content (SAC) and the REF are consistent with a model in which the ionosphere-earth current density (J_z) affects cloud microphysics. One of the ways in which J_z is modulated is by changes in stratospheric column resistance (S), which is increased by stratospheric aerosols. Because S is in series with the tropospheric column resistance (T), J_z modulation by REF requires that S be not negligible with respect to T. So the J_z modulation and the VAI response appear when the SAC is very high, or the REF reductions (which also increase S) are very deep, and when the product of the SAC and the reciprocal of the REF exceeds a threshold value dependent on T.     

Global electric circuit modulation of winter cyclone vorticity in the northern high latitudes

Small changes in extended winter (November–March) 500 hPa vorticity area index (VAI) values for the 60–80°N latitude band are shown to be positively correlated with changes in a proxy for the high latitude ionosphere-to-surface current density _Jz$J_z$.     

The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r?0.1$r?0.1$ pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHM_Hβ ? 2000 km s⁻¹) and narrow line (1000 km s⁻¹ ?FWHM_Hβ ? 2000 km s⁻¹) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z=0.35$z=0.35$, and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe Kα emission and we use these parameters to assess the consistency of our current AGN understanding.