Kinematic Decomposition Research Articles

MICONIC: Dual active galactic nuclei, star formation, and ionised gas outflows in NGC 6240 seen with MIRI/JWST

Context. Galaxy mergers are an important and complex phase during the evolution of galaxies. They may trigger nuclear activity and/or strong star forming episodes in galaxy centres that potentially alter the evolution of the system. Aims. As part of the guaranteed time observations program Mid-Infrared Characterization Of Nearby Iconic galaxy Centers (MICONIC), we used the medium-resolution spectrometer (MRS) of the Mid-Infrared Instrument on board the James Webb Space Telescope (JWST) to study NGC 6240. We aim to characterise the dual active galactic nuclei (AGN), the ionised gas outflows, and the main properties of the interstellar medium over a mapped area of 6.6″ × 7.7″. Aims. We obtained integral field spectroscopic mid-infrared data (wavelength from 4.9 to 28 μm) of NGC 6240. We modelled the emission lines through a kinematic decomposition that accounts for the possible existence of various components. Methods. We have resolved both nuclei of NGC 6240 for the first time in the full 5−28 μm spectral range. The fine structure lines in the southern (S) nucleus are broader than for the northern (N) nucleus (full width at half maximum of ≥1500 versus ∼700 km s−1 on average, respectively). High excitation lines, such as [Ne V], [Ne VI], and [Mg V], are clearly detected in the N nucleus. In the S nucleus, the same lines can be detected but only after a decomposition of the polycyclic aromatic hydrocarbon features in the integrated spectrum, due to a combination of a strong mid-IR continuum, broad emission lines, and intense star formation (SF). The SF is distributed all over the mapped field of view of 3.5 kpc × 4.1 kpc (projected), with the maximum located around the S nucleus. Both nuclear regions appear to be connected by a bridge region that is detected with all the emission lines. Based on the observed MRS line ratios and the high velocity dispersion (σ ∼ 600 km s−1), shocks also dominate the emission in this system. We detected the presence of outflows as a bubble north-west from the N nucleus and at the S nucleus. We estimated an ionised mass outflow rate of 1.4 ± 0.3 M⊙ yr−1 and 1.8 ± 0.2 M⊙ yr−1, respectively. Given the derived kinetic power of these outflows, both the AGN and the starburst could have triggered them.

The Milky Way’s Rowdy Neighbors: The Effects of the Large Magellanic Cloud and Sagittarius Dwarf on the Milky Way Disk

The Milky Way (MW) is a barred spiral galaxy shaped by tidal interactions with its satellites. The Large Magellanic Cloud (LMC) and the Sagittarius dwarf galaxy (Sgr) are the dominant influences at the present day. This paper presents a suite of four 109 particle N-body simulations, illustrating the response of the stellar disk of the MW to the close approach of the LMC and the merger of Sgr into the MW. The suite is intended to provide a resource for others to study the complex interactions between the MW and its satellites independently and together, in comparison to an isolated disk control simulation. The high temporal and mass resolution allows for a quantitative Fourier decomposition of the stellar kinematics, disentangling the individual influence of each satellite on the MW. In our preliminary analysis, we find that the influences from the LMC and Sgr on the disk of the MW appear distinct, additive, and separable within our tailored simulations. Notably, the corrugations induced by Sgr reproduce the large radial velocity wave seen in the data. Overall, our findings emphasise the need to include both satellites when modeling the present-day state of the MW structure and kinematics.

Input device matters for measures of behaviour in online experiments

Studies of perception, cognition, and action increasingly rely on measures derived from the movements of a cursor to investigate how psychological processes unfold over time. This method is one of the most sensitive measures available for remote experiments conducted online, but experimenters have little control over the input device used by participants, typically a mouse or trackpad. These two devices require biomechanically distinct movements to operate, so measures extracted from cursor tracking data may differ between input devices. We investigated this in two online experiments requiring participants to execute goal-directed movements. We identify several measures that are critically influenced by the choice of input device using a kinematic decomposition of the recorded cursor trajectories. Those using a trackpad were slower to acquire targets, mainly attributable to greater times required to initiate movements and click on targets, despite showing greater peak speeds and lower variability in their movements. We believe there is a substantial risk that behavioural disparities caused by the input device used could be misidentified as differences in psychological processes. We urge researchers to collect data on input devices in online experiments and carefully consider and account for the effect they may have on their experimental data.

z ∼ 2 dual AGN host galaxies are disky: stellar kinematics in the ASTRID Simulation

We study dual AGN host galaxy morphologies at z=2 using the ASTRID simulation, selecting black hole (BH) pairs with small separation (), high mass ( MBH,12>107M⊙), and luminosity (). We kinematically decompose (using MORDOR) ∼1000 dual AGN hosts into standard components - a ‘disk’ (thin and thick disk, pseudo-bulge) and ‘bulge’ (bulge and halo) and define disk-dominated galaxies by the disk-to-total D/T≥0.5. In ASTRID, 60.9±2.1% of dual AGN hosts (independent of separation) are disk-dominated, with the D/T distribution peaking at ∼0.7. In dual-AGN hosts, the D/T increases from $17% $ at to $ 64% $ for , and the pseudo-bulge is the dominant component of the disk fraction at the high mass end. Moreover, dual AGN hosts exhibit a higher fraction of disk/large pseudo-bulge than single-AGN hosts. The Disk-to-Total ratio is approximately constant with BH mass or AGN luminosity. We also create mock images of dual AGN host galaxies, employing morphological fitting software Statmorph to calculate morphological parameters and compare them with our kinematic decomposition results. Around 83.3±2.4% of galaxies display disk-like profiles, of which ∼60.7±2.2% are kinematically confirmed as disks. Se'rsic indices and half-mass radii of dual AGN host galaxies align with observational measurements from HST at z∼2. Around 34% are identified as mergers from the Gini−M20 relation. We find two dual AGN hosted by galaxies that exhibit disk-like se'rsic index n12<1 and (D/T)12>0.5, which are in remarkable agreement with properties of recently discovered dual quasars in disk galaxies at z∼2.

Harvesting deformation modes for micromorphic homogenization from experiments on mechanical metamaterials

A micromorphic computational homogenization framework has recently been developed to deal with materials showing long-range correlated interactions, i.e. displaying patterning modes. Typical examples of such materials are elastomeric mechanical metamaterials, in which patterning emerges from local buckling of the underlying microstructure. Because pattern transformations significantly influence the resulting effective behaviour, it is vital to distinguish them from the overall deformation. To this end, the following kinematic decomposition into three parts was introduced in the micromorphic scheme: (i) a smooth mean displacement field, corresponding to the slowly varying deformation at the macro-scale, (ii) a long-range correlated fluctuation field, related to the buckling pattern at the meso-scale, and (iii) the remaining uncorrelated local microfluctuation field at the micro-scale. The micromorphic framework has proven to be capable of predicting relevant mechanical behaviour, including size effects and spatial as well as temporal mixing of patterns in elastomeric metamaterials, making it a powerful tool to design metamaterials for engineering applications. The long-range correlated fluctuation fields need to be, however, provided a priori as input parameters. The main goal of this study is experimental identification of the decomposed kinematics in cellular metamaterials based on the three-part ansatz. To this end, a full-field micromorphic Integrated Digital Image Correlation (IDIC) technique has been developed. The methodology is formulated for finite-size cellular elastomeric metamaterial specimens deformed in (i) virtually generated images and (ii) experimental images attained during in-situ compression of specimens with millimetre sized microstructure using optical microscopy. The proposed IDIC method identifies the different kinematic fields, both before and after the microstructural buckling, and without any prior knowledge determines correctly the relevant patterning modes required by the homogenization scheme. It is further argued that patterning modes are independent of the unit cell size, the hole diameter to cell size ratio, as well as local material properties, allowing for modelling and design of (finite- and infinite-size) metamaterials and specimens with graded microstructures in terms of geometry and/or material properties. It is shown that the proposed methodology is also applicable to cellular metamaterials and structures with different microstructural designs.

The physical origin of the mass–size relation and its scatter for disk galaxies

Aims. In this study, we investigated the intricate interplay between internal (natural) and external (nurture) processes in shaping the scaling relationships between specific angular momentum (j⋆), stellar mass (M⋆), and the size of disk galaxies within the IllustrisTNG simulation. Methods. Using a kinematic decomposition of simulated galaxies, we focus on galaxies with tiny kinematically inferred stellar halos indicative of weak external influences. We examined the correlation between the mass, size, and angular momentum of galaxies by comparing simulations with observations and the theoretical predictions of the exponential hypothesis. Results. Galaxies with tiny stellar halos exhibit a large scatter in the j⋆ − M⋆ relation, which suggests that this scatter is inherently present in their initial conditions. Our analysis reveals that the disks of these galaxies adhere to the exponential hypothesis, resulting in a tight fiducial j⋆ − M⋆-scale length (size) relation that is qualitatively consistent with observations. The inherent scatter in j⋆ provides a robust explanation for the mass–size relation and its substantial variability. Notably, galaxies that are moderately influenced by external processes closely adhere to a scaling relation akin to that of galaxies with tiny stellar halos. This result underscores the dominant role of internal processes in shaping the overall j⋆ − M⋆ and mass–size relations, with external effects playing a relatively minor role in disk galaxies. Furthermore, the correlation between galaxy size and the virial radius of the dark matter halo exists but fails to provide strong evidence for a connection between galaxies and their parent dark matter halos.

Co-rotational 3D beam element using quaternion algebra to account for large rotations: Formulation theory and static applications

This paper presents a co-rotational beam element based on quaternion algebra as a means of parameterizing large rotations. This co-rotational framework is based on a decomposition of beam kinematics into a rigid element frame, which follows the element and its pure deformation. Once the decomposition between rigid body motion and deformation is obtained, the principle of virtual work allows calculating the element response projected onto large displacements and rotations. This 3D co-rotational element lies within the framework of incremental formulations. The special feature of this formulation pertains to the decomposition of kinematics to extract the rigid body motion and pure deformations through use of quaternion algebra by solving an internal nonlinear kinematic equation. Thus, from the 2 quaternions defining global rotations and the 2 displacement vectors at the ends of the beam, this method is able to extract: 1 quaternion and 1 displacement vector parameterizing the rigid body motion, plus 2 other quaternions defining the internal rotations and beam elongation. The proposed formulation based on quaternion algebra therefore constitutes an alternative to the literature’s treatment of large-rotation kinematics using a quaternion algebra. The operators are also linearized in order to obtain the algorithmic stiffness operator. Eleven distinct static numerical applications are presented, along with comparisons from the literature in the aim of demonstrating the efficiency of this proposed element.

GA-NIFS: The ultra-dense, interacting environment of a dual AGN at z ∼ 3.3 revealed by JWST/NIRSpec IFS (Corrigendum)

LBQS 0302-0019 is a blue quasar (QSO) at z ∼ 3.3, hosting powerful outflows, and residing in a complex environment consisting of an obscured AGN candidate, and multiple companions, all within 30 kpc in projection. We use JWST NIRSpec IFS observations to characterise the ionized gas in this complex system. We develop a procedure to correct for the spurious oscillations (or ‘wiggles’) in NIRSpec single-spaxel spectra, due to the spatial under-sampling of the point spread function. We perform a quasar-host decomposition with the QDeblend3D tools, and use multi-component kinematic decomposition of the optical emission line profiles to infer the physical properties of the emitting gas. The quasar-host decomposition allows us to identify i) a low-velocity component possibly tracing a warm rotating disk, with a dynamical mass Mdyn ∼10^11 Msun and a rotation-to-random motion ratio vrot/σ0 ∼2; ii) a spatially unresolved ionised outflow, with a velocity of ∼ 1000 km/s and an outflow mass rate of ∼10^4 Msun/yr. We also detect eight interacting companion objects close to LBQS 0302-0019. Optical line ratios confirm the presence of a second, obscured AGN at ∼20 kpc of the primary QSO; the dual AGN dominates the ionization state of the gas in the entire NIRSpec field-of-view. This work has unveiled with unprecedented detail the complex environment of this dual AGN, which includes nine interacting companions (five of which were previously unknown), all within 30 kpc of the QSO. Our results support a scenario where mergers can trigger dual AGN, and can be important drivers for rapid early SMBH growth.

The dynamic factor particle swarm optimization (DFPSO) to inverse kinematics of CMOR based on pose decomposition strategy

The Chinese Fusion Engineering Testing Reactor (CFETR) is a superconducting Tokamak device, whose components would get gradually damaged by being susceptible to high temperature, strong magnetic field, radiation, and so on, and should be maintained regularly. The CFETR Multipurpose Overload Robot (CMOR) is a redundant robot designed as a macro-micro arm structure for a gigantic workspace in the blanket and diverter of CFETR's maintenance. Due to the macro-micro arm structure, the robot has a high degree of freedom, and its serial DOF is up to 16 so the traditional algorithm is low efficient for the robot's kinematics. Hence, in this paper, a kinematic decomposition strategy is proposed to allocate or decouple the position aim. Besides, a novel particle swarm optimization (PSO) with dynamic accuracy called dynamic factor particle swarm optimization (DFPSO) is designed to accelerate solving the high-dimensional nonlinear kinematic problem and to improve accuracy. The results of the research show the validation and efficiency of DFPSO in the CMOR system's kinematics. Moreover, it's also a universal kinematic algorithm for all high-DOF robots.

Multi-Furcation Variations of Two Novel Double-Centered Mechanisms Based on Higher Order Kinematic Analyses and Singular Value Decomposition

Abstract This paper explores a class of extended double-centered linkages and presents two novel multi-bifurcated double-centered metamorphic and reconfigurable mechanisms. Higher order kinematic analyses and singular value decomposition are combined to demonstrate the characteristics of multi-furcation and to reveal motion branch transformation. These findings show that the presented double-centered linkages are able to evolve to distinct motion branches including two spherical 4R linkages, line-symmetric Bricard linkage or Bennett linkage. Furthermore, by exploring the local properties of singular configurations on geometric constraints and algebraic relationships, a systematic approach for the synthesis of the singular configurations can be designed to discover more novel multi-bifurcated metamorphic and reconfigurable mechanisms.

Chronostar – II. Kinematic age and substructure of the Scorpius–Centaurus OB2 association

ABSTRACT The nearest region of massive star formation – the Scorpius–Centaurus OB2 association (Sco–Cen) – is a local laboratory ideally suited to the study of a wide range of astrophysical phenomena. Precision astrometry from the Gaia mission has expanded the census of this region by an order of magnitude. However, Sco–Cen’s vastness and complex substructure make kinematic analysis of its traditional three regions, Upper Scorpius, Upper Centaurus-Lupus, and Lower Centaurus-Crux, challenging. Here, we use chronostar, a Bayesian tool for kinematic age determination, to carry out a new kinematic decomposition of Sco–Cen using full six-dimensional kinematic data. Our model identifies eight kinematically distinct components consisting of 8185 stars distributed in dense and diffuse groups, each with an independently fit kinematic age; we verify that these kinematic estimates are consistent with isochronal ages for K dwarfs. Both Upper Centaurus-Lupus and Lower Centaurus-Crux are split into two parts. The kinematic age of the component that includes PDS 70, one of the most well-studied systems currently forming planets, is 15 ± 3 Myr.

A plastic-damage approach to the excavation response of a circular opening in weak rock

During opening construction, the accumulated wall displacement and the developing excavation damaged zone are the results of stress redistribution and inelastic behavior induced by both the microcracking damage and the irreversible plastic deformation. The current approach to predict ground response to excavation disturbance is usually based on the Convergence-Confinement Method, which fails to consider the rock damage and the plastic-damage coupled mechanism, resulting in inaccurate estimation of rock deformation, particularly in the case of the weak rock with high deformability. This study establishes a plastic-damage theoretical approach for a circular opening by a kinematic decomposition of strains into an elastic, plastic and damage parts within the framework of finite strain using a hypoelastic–plastic theory, in order to investigate the inelastic behavior-induced excavation response. In this regard, the damage model provides the effective stress to the plasticity model defining the yield criterion, in combination with the strength-stiffness degradation and damage evolution. The numerical implementation is given and two examples are considered for validation. Extensive works are then carried out to clarify some issues, including the capacity of the model to characterize the inelastic behavior, the role of rock damage and confining stress dependence on ground response, and the preliminary critical support pressure for the residual failure zone.

Kinematic Decomposition of the H i Gaseous Component in the Large Magellanic Cloud

Abstract We perform a profile analysis of the combined H i data cube of the Large Magellanic Cloud (LMC) from observations with the Australia Telescope Compact Array and the Parkes radio telescope. For the profile analysis, we use a newly developed algorithm that decomposes individual line profiles into an optimal number of Gaussian components based on a Bayesian nested sampling. The decomposed Gaussian components are then classified into kinematically cold, warm, and hot gas components based on their velocity dispersion. The estimated masses of the kinematically cold, warm, and hot gas components are ∼12.2%, ∼58.3%, and ∼29.5% of the total H i mass of the LMC, respectively. Our analysis reveals the highly complex H i structure and kinematics of the LMC that are seen in previous studies but in a more quantitative manner. We also extract the undisturbed H i gas bulk motions and derive new H i gas bulk rotation curves of the LMC by applying a 2D tilted-ring analysis. In contrast to previously derived H i rotation curves, the newly derived bulk rotation curves are much more consistent with the carbon star kinematics, with rotation velocity linearly increasing in the inner part and reaching a maximum of ∼60 km s−1 at the outermost measured radius. By comparing the lower bulk rotation curves with previous studies, we conclude that there is a lower dynamical contribution of dark matter in the central part of the LMC.

Emergence of galactic morphologies at cosmic dawn: input from numerical modelling

ABSTRACTWe employ a series of high-resolution zoom-in cosmological simulations to analyse the emerging morphology of main galaxies in dark matter haloes at z ≳ 2. We choose haloes of similar masses, ${\rm log}\, M_{\rm vir}/{\rm M_\odot }\sim 11.65\pm 0.05$, at the target zf = 6, 4, and 2. The rationale for this choice allows us to analyse how the different growth rate in these haloes propagates down to galaxy scales, affecting their basic parameters. Halos were embedded in high/low overdensity regions, and two versions of a galactic wind feedback were employed. Our main results are: (1) Although our galaxies evolve in different epochs, their global parameters remain within narrow range. Their morphology, kinematics, and stellar populations differ substantially, yet all host sub-kpc stellar bars; (2) The star formation rates appear higher for larger zf; (3) Bulges and stellar spheroids were separated by stellar kinematics, discy bulges were revealed using the Sersic method and photometry.The bulge-to-total mass ratios appear independent of the last merger time for all zf. The spheroid-to-total mas ratios lie within ∼0.5–0.8; (4) The synthetic redshifted, pixelized, and PSF-degraded JWST images allow detection of stellar discs at all zf. (5) Based on the kinematic decomposition, rotational support in discs depends on the feedback type, but increases with decreasing zf; (6) Finally, the ALMA images detect discs at all zf, but spiral structure is detectable in zf = 2 galaxies. Moreover, galaxies follow the Tully–Fisher relation, being separated only by the galactic wind feedback.

A generalized framework for determination of functional musculoskeletal joint coordinate systems

Establishing anatomical coordinate systems (CS) from anatomical landmarks is sensitive to landmark selection. Vastly different results can be obtained amongst observers which can greatly affect the resulting joint kinematics. The aim of this study is to introduce an objective method for calculating functional CS definitions for bones in joints that observe three-cylindrical-joint kinematic chain decomposition methods and to apply the method on tibiofemoral joint specimens. This method is driven by low resistance joint motion during loading profiles and not from anatomical landmark selection. Two anatomical CS definitions were established from points collected by five observers, for twelve knees. The knees underwent passive flexion and internal/external rotation using the anatomical CSs. The kinematics from these profiles were used in linear least squares minimization of off-axis motions to redefine the tibia and femur origins, the femur flexion axis and the tibia internal rotation axis. Significant improvements in reproducibility of 7.4 mm (tibia origin, p < 0.001), 3.4 mm (femur origin, p < 0.001), and 2.9° (femur FE-axis, p < 0.001) between the two functional CSs compared to the two anatomical CSs were observed.Functional CSs led to significant decreases in off-axis motion during discrete passive flexion profiles. This new strategy for establishing functional CSs provides an objective approach that will reduce the effects of observer error in establishing CSs. Additionally, functional CSs allow for better interpretations of kinematic responses due to loading because effects of kinematic cross-talk is minimized.

Chemo-kinematics of the Gaia RR Lyrae: the halo and the disc

ABSTRACT We present the results of a multicomponent kinematic model of a large sample of RR Lyrae detected by Gaia. By imposing a fourfold symmetry and employing Gaia proper motions, we are able to infer the behaviour of the velocity ellipsoid between ≈3 and ≈30 kpc from the centre of the Galaxy. We detect the presence of two distinct components: a dominant non-rotating halo-like population and a much smaller rotating disc-like population. We demonstrate that the halo RR Lyrae can be described as a superposition of an isotropic and radially biased parts. The radially biased portion of the halo is characterized by a high orbital anisotropy β ≈ 0.9 and contributes between 50 per cent and 80 per cent of the halo RR Lyrae at 5 &amp;lt; R(kpc)&amp;lt;25. In line with previous studies, we interpret this high-β component as the debris cloud of the ancient massive merger also known as the Gaia Sausage (GS) whose orbital extrema we constrain. The light-curve properties of the RR Lyrae support the kinematic decomposition: the GS stars are more metal-rich and boast higher fractions of Oosterhoff Type 1 and high-amplitude short period (HASP) variables compared to the isotropic halo component. The metallicity/HASP maps reveal that the inner 10 kpc of the halo is likely inhabited by the RR Lyrae born in situ. The mean azimuthal speed and the velocity dispersion of the disc RR Lyrae out to R ≈ 30 kpc are consistent with the behaviour of a young and metal-rich thin disc stellar population.

Stellar angular momentum distribution linked to galaxy morphology

ABSTRACT We study the spatially resolved stellar specific angular momentum j* in a high-quality sample of 24 Calar Alto Legacy Integral Field Area galaxies covering a broad range of visual morphology, accounting for stellar velocity and velocity dispersion. The shape of the spaxelwise probability density function of normalized s = j*/j*mean, PDF(s), deviates significantly from the near-universal initial distribution expected of baryons in a dark matter halo and can be explained by the expected baryonic effects in galaxy formation that remove and redistribute angular momentum. Further we find that the observed shape of the PDF(s) correlates significantly with photometric morphology, where late-type galaxies have a PDF(s) that is similar to a normal distribution, whereas early types have a strongly skewed PDF(s) resulting from an excess of low-angular momentum material. Galaxies that are known to host pseudo-bulges (bulge Sérsic index nb &amp;lt; 2.2) tend to have less skewed bulge PDF(s), with skewness (b1rb) ≲ 0.8. The PDF(s) encodes both kinematic and photometric information and appears to be a robust tracer of morphology. Its use is motivated by the desire to move away from traditional component-based classifications which are subject to observer bias, to classification on a galaxy’s fundamental (stellar mass and angular momentum) properties. In future, PDF(s) may also be useful as a kinematic decomposition tool.

Collision Avoidance for an Unmanned Aerial Vehicle in the Presence of Static and Moving Obstacles

A new collision-avoidance procedure for an unmanned aerial vehicle (UAV) in the presence of static and moving obstacles is presented. The proposed procedure is based on a new form of local parameterized guidance vector fields, called collision-avoidance vector fields, which produce smooth and intuitive maneuvers around obstacles. These vector fields are generated from a decomposition of UAV kinematics and a proximity-based velocity modulation. The proposed kinematic decomposition encodes both collision avoidance and constant-speed motion for the UAV. As such, the resulting maneuvers follow nominal collision-free paths, which are referred to as streamlines of the collision-avoidance vector fields, with constant speed. Next, in accordance with the computed guidance vector fields, different collision-avoidance controllers that generate collision-free maneuvers are developed. Furthermore, it is shown that any tracking controller with convergence guarantees can be used with the avoidance controllers to track the streamlines of the collision-avoidance vector fields. Finally, numerical simulations demonstrate the efficacy of the proposed approach and its ability to avoid collisions with static and moving pop-up threats in different practical scenarios.

Modeling of twinning-induced plasticity using crystal plasticity and thermodynamic framework

In many applications of steels, especially in aerospace and petroleum industry, large deformation is required in order to achieve complex shape and geometry of finished products. In these, advanced high-strength steels play a vital role by attaining favorable amalgamation of high strength and ductility. Among all second-generation steels, twinning-induced plasticity contains a significant percentage of austenite phase, shows outstanding tensile strength and ductility. The primary cause of having these outstanding properties is found to be stress-assisted austenite to martensite phase transformation, commonly described as twinning. In this paper, a micromechanical model is developed in the thermomechanical framework to investigate elastic–plastic deformation of twinning-induced plasticity steel. It is assumed that plastic deformation is caused due to slip and mechanical twinning under given loading conditions. Firstly, a micromechanical constitutive model, considering slip and mechanical twinning as sources of permanent deformation, is developed by kinematic decomposition of an austenite crystal into intermediate configurations. Secondly, a thermodynamic framework is used to formulate driving potentials for slip and twinning mechanisms. Thirdly, the developed model is numerically implemented into finite element software ABAQUS by a user-defined material subroutine. Finally, the deformation behavior of single and polycrystalline austenite are predicted by numerical simulations in tension compression, and simple shear loading conditions. It is found that in tension twin deformation plays a dominant role, while the reverse is observed in compression. In simple shear, on an activation of twin mode, slip systems encounter higher slip resistance due to slip–slip and slip–twin interactions.

The properties of the kinematically distinct components in NGC 448 and NGC 4365

Aims. We study the kinematically distinct components in two early-type galaxies NGC 448 and NGC 4365 aided by integral-field observations with the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope. The former galaxy has previously been shown to host a counter-rotating stellar disc while the latter harbours a central (apparently) decoupled core that has been suggested to not be physically distinct from the main body and instead stems from the different orbital types in the core and main body due to its triaxial nature. We aim to measure the brightness profiles, kinematics, and stellar population properties of the peculiar kinematic structures in these galaxies and shed light on their true nature and formation mechanism.Methods. We use a kinematic decomposition technique to separate the individual contributions to the spectra of the two distinct kinematic components observed at each spatial position in the field of view. Furthermore, by folding back the outcome of a photometric decomposition we reduce the intrinsic degeneracies in recovering the kinematics and the best-fitting stellar spectral templates. Finally, by extracting the Lick line-strength indices for the individual components and fitting them to single stellar population models we derive their ages, metallicities, andα/Fe overabundances.Results. The two kinematically decoupled stellar components in NGC 448 have similar ages, but different chemical compositions. The distinct kinematic feature in NGC 448 has a nearly exponential surface-brightness light profile, dominates in the innermost ∼10″, is smaller in size, and is very likely an embedded counter-rotating disc as also indicated by its kinematics. It has higher metallicity than the main galaxy stellar body and lowerα/Fe overabundance. By contrast, we do not find evidence for true decoupling in the two distinct kinematic components in NGC 4365. This confirms earlier work suggesting that the kinematically distinct core is likely not a separate dynamical structure, but most certainly likely a projection effect stemming from the orbital structure of this galaxy that was previously found to be intrinsically triaxial in shape.Conclusions. Our findings indicate that the kinematically decoupled component in NGC 448 is truly decoupled, has external origin, and was formed through either the acquisition of gas and a subsequent star-formation episode or from the direct accretion of stars from a companion. Conversely, the presence of a kinematically distinct component in NGC 4365 is not associated to a true kinematic decoupling and is instead most likely due to a projection effect stemming from the triaxial nature of this galaxy.