Heavily reddened type 1 quasars at z > 2 I: Evidence for significant obscured black-hole growth at the highest quasar luminosities

We present a new population of z>2 dust-reddened, Type 1 quasars with 0.5<E(B-V)<1.5, selected using near infra-red (NIR) imaging data from the UKIDSS-LAS, ESO-VHS and WISE surveys. NIR spectra obtained using the Very Large Telescope (VLT) for 24 new objects bring our total sample of spectroscopically confirmed hyperluminous (>10^{13}L_0), high-redshift dusty quasars to 38. There is no evidence for reddened quasars having significantly different H$\alpha$ equivalent widths relative to unobscured quasars. The average black-hole masses (~10^9-10^10 M_0) and bolometric luminosities (~10^{47} erg/s) are comparable to the most luminous unobscured quasars at the same redshift, but with a tail extending to very high luminosities of ~10^{48} erg/s. Sixty-six per cent of the reddened quasars are detected at $>3\sigma$ at 22um by WISE. The average 6um rest-frame luminosity is log10(L6um/erg/s)=47.1+/-0.4, making the objects among the mid-infrared brightest AGN currently known. The extinction-corrected space-density estimate now extends over three magnitudes (-30 < M_i < -27) and demonstrates that the reddened quasar luminosity function is significantly flatter than that of the unobscured quasar population at z=2-3. At the brightest magnitudes, M_i < -29, the space density of our dust-reddened population exceeds that of unobscured quasars. A model where the probability that a quasar becomes dust-reddened increases at high luminosity is consistent with the observations and such a dependence could be explained by an increase in luminosity and extinction during AGN-fuelling phases. The properties of our obscured Type 1 quasars are distinct from the heavily obscured, Compton-thick AGN that have been identified at much fainter luminosities and we conclude that they likely correspond to a brief evolutionary phase in massive galaxy formation.Comment: 16 pages, 9 figures (+ 2 appendices), Accepted for publication in MNRA

A two-level method for calculation of microstress on reinforced plates with circular hole in case of extension normal to principal direction

The stress concentration must often be examined at two levels while analyzing the stress condition of composite materials. The macroconcentration depends on the presence of holes, notches and other local areas of a construction. Typical dimensions of macroconcentration distribution areas are of the order of 0,01–0,1 m. Macroconcentration analysis is performed using the models of homogeneous material. Microstress concentration occurs in structurally inhomogeneous composites due to the structural heterogeneity of the composite. The sizes of concentration areas in regular structures are defined by the sizes of periodically recurring areas. In fibrous composites, such areas have the size of approximately 0,0001 m or less. This makes it necessary to use a two-level approach for the analysis of the stress concentration in the construction of composite materials. The aim of the present study was to compute the stress concentration in unidirectional reinforced composite plate with circular hole with respect to the volume ratio of the component materials in composite. The contour of the circular hole and its dependency on the structure of plates was calculated in order to study the behaviors of macro- and microstresses. The boundary conditions at a large distance from the hole are pressure, uniformly distributed on the plate. Also this problem is analyzed with the finite element method by package ANSYS. Macroconcentration is defined based on the solution of the plane problem of elasticity theory of the orthotropic material by the virtue of functions of a complex variable. The finite element method was used to investigate the stress distribution at microlevel. Boundary conditions that model the state of the specified twodimensional representative cell in the composite structure were established. The results demonstrated the macro- and microstresses and behavior of the orthotropic plate with a circular hole calculated for two different structures

Optical parametric generator based on orientation-patterned gallium phosphide

We report the first pulsed optical parametric generator based on Orientation-patterned Gallium Phosphide. The output is tunable from 1721-1850 nm (signal) and 2504-2787 nm (idler), providing a total output power of 18 mW.Peer ReviewedPostprint (author's final draft

Critically phase-matched Ti:sapphire-laserpumped deep-infrared femtosecond optical parametric oscillator based on CdSiP2

We report a high-repetition-rate femtosecond optical parametric oscillator (OPO) for the deep-infrared (deep-IR) based on type-I critical phase-matching in CdSiP2 (CSP), pumped directly by a Ti:sapphire laser. Using angle-tuning in the CSP crystal, the OPO can be continuously tuned across 7306–8329 nm (1201–1369  cm−1) in the deep-IR. It delivers up to 18 mW of idler average power at 7306 nm and >7  mW beyond 8000 nm at 80.5 MHz repetition rate, with the spectra exhibiting bandwidths of >150  nm across the tuning range. Moreover, the signal is tunable across 1128–1150 nm in the near-infrared, providing up to 35 mW of average power in ∼266  fs pulses at 1150 nm. Both beams exhibit single-peak Gaussian distribution in TEM00 spatial profile. With an equivalent spectral brightness of ∼5.6×1020photons s−1 mm−2 sr−10.1% BW−1, this OPO represents a viable alternative to synchrotron and supercontinuum sources for deep-IR applications in spectroscopy, metrology, and medical diagnostics.Peer ReviewedPostprint (author's final draft

Femtosecond deep-infrared optical parametric oscillator pumped directly by a Ti:sapphire laser

We report a high-repetition-rate femtosecond optical parametric oscillator (OPO) for the deep-infrared (deep-IR) based on the nonlinear optical crystal, CdSiP2 (CSP), pumped directly by a Ti:sapphire laser, for the first time. By pumping CSP at <1 μm, we have achieved practical output powers at the longest wavelengths generated by any Ti:sapphire-pumped OPO. Using a combination of pump wavelength tuning, type-I critical phase-matching, and cavity delay tuning, we have generated continuously tunable radiation across 6654−8373 nm (1194−1503 cm-1) at 80.5 MHz repetition rate, providing up to 20 mW of average power at 7314 nm and <7 mW beyond 8000 nm, with idler spectra exhibiting bandwidths of 140−180 nm across the tuning range. Moreover, the near-IR signal is tunable across 1127−1192 nm, providing up to 37 mW of average power at 1150 nm. Signal pulses, characterised using intensity autocorrelation, have durations of ∼260–320 fs, with corresponding time-bandwidth product of ∆υ∆τ∼1. The idler and signal output exhibit a TEM00 spatial profile with single-peak Gaussian distribution. With an equivalent spectral brightness of ∼6.68×1020 photons s-1 mm-2 sr-1 0.1% BW-1, this OPO represents a viable table-top alternative to synchrotron and supercontinuum sources for deep-IR applications in spectroscopy, metrology and medical diagnostics.Peer ReviewedPostprint (author's final draft

A New Numerical Method for Calculation of Micro- Stress on Unidirectionally Reinforced Plates with Circular Hole In Case of Extension to a Principal Direction

The aim of the present study was to compute the stress concentration in reinforced composite plate with circular hole with respect to the volume ratio of the component materials in composite. The contour of the circular hole and its dependency on the structure of plates were calculated in order to study the behaviors of macro and micro-stresses. The boundary conditions at a large distance from the hole are pressure, uniformly distributed on the plate. Also this problem is analyzed with the finite element method by package ANSYS. The results demonstrated the macro and micro stress and behavior of the orthotropic plate with a circular hole calculated for two different structures

Shocked molecular gas towards the SNR G359.1-0.5 and the Snake

We have found a bar of shocked molecular hydrogen (H2) towards the OH(1720 MHz) maser located at the projected intersection of supernova remnant (SNR) G359.1-0.5 and the nonthermal radio filament, known as the Snake. The H2 bar is well aligned with the SNR shell and almost perpendicular to the Snake. The OH(1720 MHz) maser is located inside the sharp western edge of the H2 emission, which is consistent with the scenario in which the SNR drives a shock into a molecular cloud at that location. The spectral-line profiles of 12CO, HCO+ and CS towards the maser show broad-line absorption, which is absent in the 13CO spectra and most probably originates from the pre-shock gas. A density gradient is present across the region and is consistent with the passage of the SNR shock while the H2 filament is located at the boundary between the pre--shocked and post-shock regions.Comment: 8 pages, 12 figures, accepted by the MNRAS, typos fixe

A New Numerical Procedure for Determination of Effective Elastic Constants in Unidirectional Composite Plates

In this paper a composite plate with similar unidirectional fibers is considered. Assuming orthotropic structure, theory of elasticity is used for investigating the stress concentration. Also, complex variable functions are utilized for solving the plane stress problems. Then the effective characteristics of this plate are studied numerically by using ANSYS software. In this research a volume element of fibers in square array is considered. In order to investigate the numerical finite element modeling, the modeling of a quarter unit cell is considered. For determining the elasticity coefficients, stress analysis is performed for considered volume with noting to boundary conditions. Effective elasticity and mechanical properties of composite which polymer epoxy is considered as its matrix, are determined theoretically and also by the proposed method in this paper with finite element method. Finally, the variations of mechanical properties with respect to fiber-volume fraction are studied

Frequency-Doubling of Femtosecond Pulses in “Thick” Nonlinear Crystals With Different Temporal and Spatial Walk-Off Parameters

We present a comparative study on frequency-doubling characteristics of femtosecond laser pulses in thick nonlinear crystals with different temporal and spatial walk-off parameters. Using single-pass second harmonic generation (SHG) of 260 fs pulses at 1064 nm from a high-average-power femtosecond Yb-fiber laser in 5-mm-long crystals of β-BaB2O4 (BBO) and BiB3O6 (BIBO), we find that for comparable values of temporal and spatial walk-off parameters in each crystal, the optimum focusing condition for SHG is more strongly influenced by spatial walk-off than temporal walk-off. It is also observed that under such conditions, the Boyd and Kleinman theory commonly used to define the optimum focusing condition for frequency-doubling of cw and long-pulse lasers is also valid for SHG of ultrafast lasers. We also investigate the effect of focusing on the spectral, temporal, and spatial characteristics of the second harmonic (SH) radiation, as well as angular acceptance bandwidth for the SHG process, under different temporal and spatial walk-off conditions in the two crystalsPeer ReviewedPostprint (author's final draft