A single-merger scenario for the formation of the giant stream and the warp of M31

We propose that the accretion of a dwarf spheroidal galaxy provides a common origin for the giant southern stream and the warp of M31. We run about 40 full N-body simulations with live M31, infalling galaxies with varying masses and density profiles, and cosmologically-plausible initial orbital parameters. Excellent agreement with a full range of observational data is obtained for a model in which a dark-matter-rich dwarf spheroidal, whose trajectory lies on the thin plane of corotating satellites of M31, is accreted from its turnaround radius of about 200 kpcs into M31 at approximately 3 Gyrs ago. The satellite is disrupted as it orbits in the potential well of the galaxy and forms the giant stream and in return heats and warps the disk of M31. We show that our cosmologically-motivated model is favoured by the kinematic data over the phenomenological models in which the satellite starts its infall from a close distance of M31. Our model predicts that the remnant of the disrupted satellite resides in the region of the North-Eastern shelf of M31. The results here suggest that the surviving satellites of M31 that orbit on the same thin plane, as the disrupted satellite once did, could have all been accreted from an intergalactic filament.Comment: 18 pages, 22 figures, 3 table

Finite Element Analysis of Interlocking Loadbearing Hollow Block

The interlocking hollow block system (IHB) is used recently for the construction of loadbearing and non loadbearing walls. The IHB system draws the attention of engineers and scientists all over the world due to its simplicity and lower construction cost, in addition to its good structural performance. The mechanical interlocking between different block units are designed to replace the mortar layers. This study covers the theoretical investigation of different hollow block systems in terms of their mechanical, physical and structural properties. The research focus mainly on the structural analysis of "Putra block" which is an interlocking hollow block system developed recently by the Housing Research Centre at UPM. The analysis of the putra interlocking hollow block has been carried out using the finite element method. The Finite Element analysis covers the structural behaviour of an individual block, interlocking prism and panel walls using different types of interlocking blocks i.e. stretcher, half and corner block, under vertical and horizontal loads. The structural behaviour of individual blocks, prisms and wall panels are studied in terms of stress distribution, deformation and the location of the maximum stresses as well as failure load. In addition, the effect of eccentricity of the vertical axial load on the ultimate load capacity of the wall panel has been investigated. The maximum compressive stresses developed in the individual blocks (stretcher, half and comer block) are 3.92 MPa, 3.16 MPa and 2.95 MPa respectively, while the maximum tensile stresses are 1.47 MPa, 1.43 MPa and 0.92 MPa respectively. Interlocking block prism has been modeled using interface elements between blocks. The maximum compressive and tensile stresses have been found to be equal to 4.65 MPa and 2.38 MPa respectively. A panel wall with dimensions of 1200 mm W x 1200 mm H x 150 mm T has been elastically analysed under unifomtly distributed load. The result obtained indicates that the stress distribution is similar to the stress distribution observed in the prism. Interlocking block panel has been nonlinearly analyzed under concentric and different eccentricities loading (0.05t, O.lt, 0.2t, and O.3t). The failure loads obtained were 25.63, 24.0, 22.4, 19.95 and 17.96 N/mm2 respectively. The efficiency of the panel wall with the increase of the eccentricity of the load have been compared with the experimental observations. Panel walls with heights of 2.0 m, 2.4 m and 3.0 m have been nonlinearly analysed under lateral load and the maximum lateral displacements observed in different walls are 6.96 mm, 8.28 rom and 11.89 rom respectively. The failure load decrease with increasing the height of the panel. The joint opening in the tensile side of the wall has been observed. The opening suddenly increases to a large value when the applied load approaches the failure stress, indicating a brittle failure mechanism. The overall conclusions drawn from this investigation indicates that the theoretical analysis performed in this study indicates possible cracking in the webs when the putra block is used to construct loadbearing walls in 5-storey buildings and considered critical. This is due to neglecting the geometric nonlinearity and initial imperfection, which is quite possible in the construction field. the construction of loadbearing walls in 1-2 storey buildings. While, more comprehensive experimental and theoretical study is required to ensure the applicability of putra block in 5- storey building

The Baryon Cycle at High Redshifts: Effects of Galactic Winds on Galaxy Evolution in Overdense and Average Regions

We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at $z\sim 6-12$, in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent in the "normal" region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on both environments, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR-stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in volume-filling factor of hot, high-metallicity gas which is near unity for CW, while it remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent in the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties to those of host galaxies. Further constraints on the state of the IGM at high-$z$ are needed to separate different wind models.Comment: 22 pages, 15 figures, accepted for publication in the Astrophysical Journa

M - sigma relation between SMBHs and the velocity dispersion of globular cluster systems

We find evidence that the mass MBH of central supermassive black holes (SMBHs) correlates with the velocity dispersion sigma_GC of globular cluster systems of their host galaxies. This extends the well-known MBH - sigma_sph relation between black hole mass and velocity dispersion of the host spheroidal component. We compile published measurements of both MBH and sigma_GC for a sample of 13 systems and find the relation log(MBH) = alpha + beta log(sigma_GC/200) with alpha = 8.63 \pm 0.09 and beta = 3.76 \pm 0.52. We also consider blue (metal-poor) and red (metal-rich) globular clusters sub-populations separately and obtain a surprisingly tight correlation using only the velocity dispersion sigma_GC^red of the red clusters with alpha = 8.73 \pm 0.09 and beta = 3.84 \pm 0.52 and an intrinsic scatter eps_0 = 0.22 dex compared to eps_0 = 0.27 dex for the MBH - sigma_sph of our sample. We use our MBH - sigma_GC relation to estimate the central black hole mass in five galaxies for which sigma_GC^red is measured.Comment: 6 pages, 3 figures, 3 tables, accepted for publication in MNRA

Ce que le politique dit de la violence

Toute la philosophie politique se présente comme une réflexion sur l’ordre juste. Elle est traversée par les rapports qui s’instituent et se déploient entre violence et politique. Que nous dit le politique de la violence ? À quelles conceptions de l’humanité de l’homme et du socle de la socialité ces rapports renvoient-ils ? Deux figures permettent de comprendre la question : le refoulement de la violence comme fondation de l’autorité ; la reconnaissance de la violence comme fondation de l’interaction. À partir de ces deux figures, on peut comprendre ce que signifient, aujourd’hui, les rapports entre l’assomption ou le refus de la violence, d’une part, la définition du politique, d’autre part

Extraction of the electrical parameters of the Au/InSb/InP Schottky diode in the temperature range (300 K- 425 K)

In this work, we have presented a theoretical study of  Au/InSb/InP Schottky diode based on current-voltage (I-V) measurement in the temperature range ( 300 K- 425 K). Electrical parameters of Au/InSb/InP such as barrier height (Φb), ideality factor and series resistance have been calculated by employing the conventional (I-V), Norde, Cheung and Chattopadhyay methods. Measurements show that the Schottky barrier height (SBH), ideality factor and series resistance, RS for Au/InSb/InP Schottky diode in the temperature range (300 K–425 K)  are 0.602-0.69eV, 1.683-1.234 and 84.54-18.95 (Ω), respectively. These parameters were extracted using Atlas-Silvaco-Tcad logical