Characteristic Radius Research Articles

IMF radial gradients in most massive early-type galaxies

ABSTRACT Using new long-slit spectroscopy obtained with X-Shooter at ESO-VLT, we study, for the first time, radial gradients of optical and near-infrared initial mass function (IMF)-sensitive features in a representative sample of galaxies at the very high mass end of the galaxy population. The sample consists of seven early-type galaxies (ETGs) at z ∼ 0.05, with central velocity dispersion in the range 300 ≲ σ ≲ 350 km s−1. Using state-of-the-art stellar population synthesis models, we fit a number of spectral indices, from different chemical species (including TiO and Na indices), to constrain the IMF slope (i.e. the fraction of low-mass stars), as a function of galactocentric distance, over a radial range out to ∼4 kpc. ETGs in our sample show a significant correlation of IMF slope and surface mass density. The bottom-heavy population (i.e. an excess of low-mass stars in the IMF) is confined to central galaxy regions with surface mass density above $\rm \sim 10^{10}\, M_\odot \, kpc^{-2}$, or, alternatively, within a characteristic radius of ∼2 kpc. Radial distance, in physical units, and surface mass density are the best correlators to IMF variations, with respect to other dynamical (e.g. velocity dispersion) and stellar population (e.g. metallicity) properties. Our results for the most massive galaxies suggest that there is no single parameter that fully explains variations in the stellar IMF, but IMF radial profiles at z ∼ 0 rather result from the complex formation and mass accretion history of galaxy inner and outer regions.

Amorphous Silicon Self‐Rolling Micro Electromechanical Systems: From Residual Stress Control to Complex 3D Structures

In surface micromachining, the control of the residual stress of the films is crucial, as excessive stress can cause buckling, cracking, and peeling of the materials and fracture of the devices. However, the gradients of stress across the thickness of individual films or the stress mismatch in composite structural layers can be exploited to obtain highly complex 3D structures via self‐assembly, self‐bending, self‐positioning, or self‐rolling processes. Herein, the thin‐film residual stresses of amorphous silicon, TiW, AlSiCu, Cr, Au, and SiO2 are assessed using polymer substrates and tuned. Then, a stress‐mismatched bi‐layer of amorphous silicon (tensile) and TiW (compressive) is used in the fabrication of complex 3D self‐rolling micro electromechanical systems (MEMS) structures. The freestanding regions of the fabricated MEMS have a characteristic radius of curvature of ≈100 μm. Current‐induced thermal actuation of a suspended plate is demonstrated. The microfabrication process and materials used are compatible with standard cleanroom processing and with a variety of substrates. In the future, amorphous silicon photodiodes, photoconductors, or other semiconductor devices can be incorporated on complex MEMS fabricated by self‐rolling/self‐bending processes and applied to localized optical and electrical sensing.

The Multi-messenger Matrix: The Future of Neutron Star Merger Constraints on the Nuclear Equation of State

Abstract The electromagnetic (EM) signal of a binary neutron star (BNS) merger depends sensitively on the total binary mass, M tot, relative to various threshold masses set by the neutron star (NS) equation of state (EOS), parameterized through the neutron star (NS) maximum mass, M TOV, and characteristic radius, R 1.6. EM observations of a BNS merger detected through its gravitational-wave (GW) emission, which are of sufficient quality to ascertain the identity of the merger remnant, can therefore constrain the values of M TOV and R 1.6, given the tight connection between M tot and the well-measured chirp mass. We elucidate the present and future landscape of EOS constraints from BNS mergers, introducing the “Multi-Messenger Matrix,” a mapping between GW and EM measurables that defines the ranges of event chirp masses that provide the most leverage on constraining the EOS. By simulating a population of BNS mergers drawn from the Galactic double NS mass distribution we show that ∼10 joint detections can constrain M TOV and R 1.6 to several percent level where systematic uncertainties may become significant. Current EOS constraints imply that most mergers will produce supramassive or hypermassive remnants, a smaller minority (possibly zero) will undergo prompt collapse, while at most only a few percent of events will form indefinitely stable NSs. In support of the envisioned program, we advocate in favor of Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo releasing chirp mass estimates as early as possible to the scientific community, enabling observational resources to be allocated in the most efficient way to maximize the scientific gain from multi-messenger discoveries.

Neutral Shadowing Force Effect on Structural Properties and Oscillations of Dust Particles in Cryogenic Environment

Recently, it was shown that the neutral shadowing interaction can be significantly stronger in the cryogenic complex plasma than in the plasma with neutrals at room temperature. Here, we present the results of the investigation—by molecular dynamics (MD) simulations—of the impact of the neutral shadowing interaction on the radial pair distribution function and the velocity autocorrelation function (VAF) of the charged dust particles in a 2-D layer. The spectrum of VAF was computed to estimate the influence of the neutral shadowing force on the oscillations of dust particles. We found that the neutral shadowing interaction can significantly affect the structural properties and the characteristic longitudinal oscillation frequency of dust particles if the characteristic radius of the neutral shadowing interaction exceeds a mean interdust particle distance. The latter case corresponds to low pressures, $p Pa, and cryogenic temperatures less than 10 K. In addition, the dust acoustic wave taking into account that the neutral shadowing force was derived. It is found that the neutral shadowing force leads to the increase of the sound speed of the dust acoustic wave.

Dynamics of convective upwelling of large-scale weakly heated atmospheric aggregates

Equations for the center-of-mass speed of the parcel of heated air, the mass of the entrained cool air, and the resulting buoyancy of the entire air aggregate have been used to obtain exact and approximate relations for describing height and temporal dependences of the characteristic radius, the excess relative temperature, and a weakly heated large-scale (hundreds of meters and greater) air aggregate convective upwelling. It is shown that the excess temperature relaxation in the air aggregate occurs quickly, the aggregate radius increases slowly and insignificantly. The variations in the center-of-mass speed of the aggregate are not monotonous. First, the speed increases from zero to a maximum value, and then it decreases to zero. Numerical simulations have been performed for the case of interest to practical applications.

Vacuum polarization of the quantized massive scalar field in the global monopole spacetime: The renormalized quantum stress energy tensor

This paper is devoted to the construction of the renormalized quantum stress energy tensor $\left<T_{\mu}^{\nu}\right>_{ren}$ for a massive scalar field with arbitrary coupling to the gravitational field of a pointlike global monopole, using the Schwinger-DeWitt approximation, up to second order in the inverse mass $\mu$ of the field. The given stress energy tensor is constructed by functional differentiation with respect to the metric tensor of the one-loop effective action of sufficiently massive scalar field, such that the Compton length of the quantum field is much less than the characteristic radius of the curvature of the background geometry. The results are obtained for a general curvature coupling parameter $\xi$, and specified to the more physical cases of minimal and conformal coupling, showing that in this specific cases, the quantum massive scalar field in the global monopole spacetime violates all the pointwise energy conditions.

Dynamics of Convective Upwelling of Large-Scale Weakly Heated Atmospheric Aggregates

Equations for the center-of-mass speed of the parcel of heated air, the mass of the entrained cool air, and the resulting buoyancy of the entire air aggregate have been used to obtain exact and approximate relations for describing height and temporal dependences of the characteristic radius, the excess relative temperature, and convective upwelling of a weakly heated large-scale (hundreds of meters and greater) air aggregate. It is shown that the excess temperature relaxation in the air aggregate occurs quickly and the aggregate radius increases slowly and insignificantly. The variations in the center-of-mass speed of the aggregate are not monotonous. First, the speed increases from zero to the maximum value, and then it decreases to zero. Numerical simulations have been performed for the cases of interest to practical applications.

Unconventional Look at the Diameters of Quantum Systems: Could the Characteristic Atomic Radius Be Interpreted as a Reactivity Measure?

Decoding of atomic and ionic radii of transition metals in terms of energy response against changes in electron number and external potential variation has been considered. Energy as a functional of electron density by means of its derivatives is linked to response density and the electron detachment process. Employing charge sensitivity analysis and the electronegativity equalization principle, we interpret the electronic structure transformations (electron-following/preceding perspectives) into atomic diameters. Additionally, qualitative associations described within hard/soft acid/base theory and the approximate correlations of respective conceptual density functional theory reactivity descriptors were considered to meet postulates of the correspondence principle, giving the characteristic radius the attribute of latent variable related to quantum mechanical observables. By means of local density approximation, an insight from statistical analysis of frontier electron density complements the picture of...

New Insights into the Physical Conditions and Internal Structure of a Candidate Proto-globular Cluster

Abstract We present ∼0.″1 resolution (∼10 pc) Atacama Large Millimeter/submillimeter Array observations of a molecular cloud identified in the merging Antennae galaxies with the potential to form a globular cluster, nicknamed the “Firecracker.” Since star formation has not yet begun at an appreciable level in this region, this cloud provides an example of what the birth environment of a globular cluster may have looked like before stars formed and disrupted the natal physical conditions. Using emission from 12CO(2–1), 12CO(3–2), 13CO(2–1), HCN(4–3), and HCO+(4–3) molecular lines, we are able to resolve the cloud’s structure and find that it has a characteristic radius of 22 pc and a mass of (1–9) × 106 M ⊙. We also put constraints on the abundance ratios 12CO/13CO and H2/12CO. Based on the calculation of the mass, we determine that the commonly used CO-to-H2 conversion factor in this region varies spatially, with average values in the range cm−2 (K km s−1)−1. We demonstrate that if the cloud is bound (as is circumstantially suggested by its bright, compact morphology), an external pressure in excess of P/k &gt; 108 K cm−3 is required. This would be consistent with theoretical expectations that globular cluster formation requires high-pressure environments, much higher than typical values found in the Milky Way. The position–velocity diagram of the cloud and its surrounding material suggests that this high pressure may be produced by ram pressure from the collision of filaments. The radial profile of the column density can be fit with both a Gaussian and a Bonnor–Ebert profile. If the Bonnor–Ebert fit is taken to be indicative of the cloud’s physical structure, it would imply the cloud is gravitationally stable and pressure-confined. The relative line strengths of HCN and HCO+ in this region also suggest that these molecular lines can be used as a tracer for the evolutionary stage of a cluster.

Sublimation of buried cometary ice

The sublimation of ice covered by dust is a common way of outgassing of comets. The rate of this process depends on the thermal conductivity and permeability of dust, as well as the properties of the ice itself. It can be calculated using the Hertz-Knudsen equation, corrected for temperature dependent sublimation coefficient αs(T) (Gundlach et al., 2011; Kossacki et al., 1999; Kossacki & Leliwa-Kopystynski, 2014; Kossacki et al., 2017) and the Knudsen equation for the permeability of dust. In this work we present direct experimental verification of this set of equations using sand with different granulation: coarse (grain radii rg = 0.5 − 1 mm), medium (rg = 0.25 − 0.5 mm), fine (rg = 0.125 = 0.25 mm) and unsorted (rg = 0 − 1 mm, rg, av = 0.5 mm). We have found that at T < 220 K the measured rate of recession of the surface is correctly reproduced if αs(T) is the same as determined for the uncovered ice (Kossacki & Leliwa-Kopystynski, 2014). The characteristic radius of pores in the Knudsen equation is approximately equal to, or greater than the arithmetic average of the largest and the smallest radii of grains.

Stability Criterion for the Centrifugal Instability of Surface Intensified Anticyclones

AbstractWe investigate the linear stability of intense baroclinic anticyclones, with a particular focus on the centrifugal (inertial) instability. Various vertical and radial velocity profiles are studied. The vertical profiles are such that the velocity is maximum at the surface. These profiles correspond to oceanic eddies such as submesoscale mixed-layer eddies or intense mesoscale eddies in the upper thermocline. The results show that the main characteristics of the centrifugal instability (growth rate, vertical wavelength) depend weakly on the baroclinic structure of the anticyclone. The dominant azimuthal wavenumber is for small Burger number (Bu) and for higher Bu, where Bu is the square root of the ratio of the deformation radius over the characteristic eddy radius where the velocity is maximum. The marginal stability limits of the centrifugal instability for the different velocity profiles collapse approximately on a single curve in the parameter space (Ro, Bu), where is the Rossby number, with being the maximum velocity. By means of an asymptotic analysis for short vertical wavelength, an explicit prediction for the marginal stability limit is derived for a wide range of velocity profiles. We then suggest to use, for most of oceanic anticyclones, the instability criterion valid for a Gaussian eddy: where is the Ekman number, H is the eddy depth, and ν is the turbulent viscosity at the ocean surface. Some baroclinic anticyclones can remain stable even if they have a core region of negative absolute vorticity provided that they are small enough. This formula explains the few observations of intense anticyclonic eddies having a negative core vorticity around .

Halo Concentrations and the Fundamental Plane of Galaxy Clusters

According to the standard cold dark matter (CDM) cosmology, the structure of dark halos including those of galaxy clusters reflects their mass accretion history. Older clusters tend to be more concentrated than younger clusters. Their structure, represented by the characteristic radius r s and mass M s of the Navarro–Frenk–White (NFW) density profile, is related to their formation time. In this study, we showed that r s , M s , and the X-ray temperature of the intracluster medium (ICM), T X , form a thin plane in the space of ( log r s , log M s , log T X ) . This tight correlation indicates that the ICM temperature is also determined by the formation time of individual clusters. Numerical simulations showed that clusters move along the fundamental plane as they evolve. The plane and the cluster evolution within the plane could be explained by a similarity solution of structure formation of the universe. The angle of the plane shows that clusters have not achieved “virial equilibrium” in the sense that mass/size growth and pressure at the boundaries cannot be ignored. The distribution of clusters on the plane was related to the intrinsic scatter in the halo concentration–mass relation, which originated from the variety of cluster ages. The well-known mass–temperature relation of clusters ( M Δ ∝ T X 3 / 2 ) can be explained by the fundamental plane and the mass dependence of the halo concentration without the assumption of virial equilibrium. The fundamental plane could also be used for calibration of cluster masses.

Влияние силы атомного увлечения на диффузию пылевых частиц в криогенной плазме

At cryogenic temperatures of atoms, the thermophoretic force (atomic drag force) is stronger than at room temperature. The temperature difference between the surface of the dust particles and the surrounding gas was previously evaluated. This difference was the reason of the manifestation of the so-called thermophoretic force between dust particles. This paper presents the results of a study obtained using molecular dynamics modeling of the effect of thermophoretic force on the mean-square displacement of charged dust particles in a two-dimensional layer. The mean-square displacement (MSD) characterizes the diffusion of particles. By changing parameters that describe thermophoretic force, there were identified cases when this force leads to significant changes in the properties of the cryogenic complex plasma. Also the data on computer simulation are provided. MSD was calculated for different values of the coupling parameter. The ratios MSD curves with and without thermophoretic force are given. It was found that the thermophoretic force can drastically influence the diffusion of dust particles if the characteristic interaction radius due tothermophoretic force exceeds the average distance between dust particles. The aforementioned effect can take place at low density of neutral and temperatures relevant to cryogenic conditions. The force with increasing value of cutoff raduis causes deviation of the curves from data obtained on the basis neglecting thermophoretic force. Deviation becomes more visible, with increasing coupling parameter, due to the force.

Role of Four Gravitational Constants in Nuclear Structure

This paper attempts to understand the role of the four gravitational constants in the nuclear structure whichhelps in understanding the nuclear elementary charge, the strong coupling constant, nuclear charge radii,nucleon magnetic moments, nuclear stability, nuclear binding energy and Neutron life time. The three assumed atomic gravitational constants help in understanding neutron-proton stability. Electromagnetic and nuclear gravitational constants play a role in understanding proton-electron mass ratio, Bohr radius and characteristic atomic radius. With reference to the weak gravitational constant, it is possible to predict the existence of a weakly interacting fermion of rest energy 585 GeV, called Higg’s fermion. Cosmological ‘dark matter’ research and observations can be carried out in this direction also.

On the Final State of Black Holes

The final state of a black hole and its force balance is considered, in the limit where all available energy is radiated away and all matter remains in the lowest form of Zero Point Energy (ZPE). In conventional theory without the concept of ZPE, the gravitational contraction would transfer the system into a mass point, being questionable from the theoretical point of view. But the inclusion of ZPE makes a force balance possible, resulting in a finite characteristic radius of a black hole mass distribution. This radius is of the same order as that of the so-called Schwarzschild radius, but is not related to the physics of the latter, which is due to particle trapping in the gravitational field.

A UV complete picture of black hole conforming to low energy effective field theory

In this paper, we propose a UV complete, quantum improved picture of a black hole geometry that conforms to the IR gravity of effective field theory. Our work builds on identifying an effective space-distributed notion of black hole fluid in quantum improved regular Einstein gravity and its theoretical correspondence with a cosmology inspired power law fluctuation of matter. Hence, we make use of phenomenological asymptotic scales of matter fluctuation in static space to consequently derive a UV complete line-element of black hole space–time. In this appraisal, it gets explicit how principle of causality is preserved even while there is an effective spread of black hole fluid across horizon(s). Gravity changes from its conventional classical geometry-state to a quantum masked profile across a hypersurface of characteristic radius [Formula: see text]. We make analyses that probe the newly proposed quantum improved gravity in the contexts of regularity of Einstein fields, complete predictability of Hawking radiation process, and first law of black hole thermodynamics. It emerges that quantum black hole geometry self-regulates a regular timelike core that is abide by every quantum theoretical constraint while being flat around its center.

A Novel Model of Quasi-Stationary Vortices in the Earth’s Atmosphere

In the great variety of vortex motions in the atmosphere, concentrated vortices, attracting increased interest from the point of view of both fundamental research and practice, clearly stick out. A sufficiently precise definition of the concentrated vortex can be given for the case of an ideal fluid—it is an area localized in the space, surrounded by a potential flow and having a nonzero vorticity. Such vortices can be combined into a class of small-scale concentrated vortices including dust devils (DDs), waterspouts, fire vortices, and larger scale and more intense tornadoes. Unlike planetary-scale vortices (cyclones and anticyclones), DDs and tornadoes are small-scale vortices. DDs and tornadoes are generated in different environments (tornadoes occur in strong storm clouds), but they have much in common in regards to their structure. The speed of rotation in such vortices reaches the maximum value at a characteristic radius and tends to zero when approaching the center. The rotation speed in them has much in common with the rotation speed in stationary Rankine or Burgers vortices. This work is devoted to the study of a novel low-parameter model of stationary vortices. The model is most suitable for describing concentrated vortices in the Earth’s atmosphere. Within the framework of ideal hydrodynamics, a new model of thin vortex filaments is constructed at heights that are small when compared to the vertical scale of the Earth’s atmosphere. Unlike Rankine and Burgers vortices, it allows one to describe the structure limited in the radial direction. Quasi-stationary vortices in such a model arise as a result of the balance of two effects: the concentration of vertical vorticity to the center and the advection of the vortex motion in the vertical direction.

System-size Convergence of Nonthermal Particle Acceleration in Relativistic Plasma Turbulence

Abstract We apply collisionless particle-in-cell simulations of relativistic pair plasmas to explore whether driven turbulence is a viable high-energy astrophysical particle accelerator. We characterize nonthermal particle distributions for varying system sizes up to L/2πρ e0 = 163, where L/2π is the driving scale and ρ e0 is the initial characteristic Larmor radius. We show that turbulent particle acceleration produces power-law energy distributions that, when compared at a fixed number of large-scale dynamical times, slowly steepen with increasing system size. We demonstrate, however, that convergence is obtained by comparing the distributions at different times that increase with system size (approximately logarithmically). We suggest that the system-size dependence arises from the time required for particles to reach the highest accessible energies via Fermi acceleration. The converged power-law index of the energy distribution, α ≈ 3.0 for magnetization σ = 3/8, makes turbulence a possible explanation for nonthermal spectra observed in systems such as the Crab Nebula.

Searching for environmental effects on galaxy kinematics in groups and clusters atz∼ 1 from the ORELSE survey

We present an investigation of the dependence of galaxy kinematics on the environment for a sample of 94 star-forming galaxies at $z\sim0.9$ from the ORELSE survey. ORELSE is a large photometric and spectroscopic campaign dedicated to mapping out and characterizing galaxy properties across a full range of environments in 15 fields containing large-scale structures (LSSs) in a redshift range of $0.6 < z < 1.3$. We constrained the rotation velocity for our kinematic sample in an ORELSE field, containing the SC1604 supercluster, by fitting high-resolution semi-analytical models to the data. We constructed the stellar-mass/B-band Tully-Fisher relation and found no dependence of the intrinsic scatter on both local and global environment. Moreover, we compared the stellar-to-dynamical mass ratio ($M_\ast/M_{dyn}$) of SC1604 galaxies to those residing in less dense local environment by leveraging data from the HR-COSMOS sample. We found that, at fixed stellar mass, SC1604 galaxies have $\sim30\%$ smaller dynamical masses on average. By comparing the distributions of the galaxy parameters that define $M_{dyn}$ (i.e., circular velocity and the characteristic radius $r_{2.2}$) between SC1604 and HR-COSMOS, we found that smaller dynamical masses are mostly caused by smaller $r_{2.2}$ for SC1604 galaxies. We also observed that SC1604 galaxies in general show $\sim20\%$ lower stellar specific angular momentum ($j_\ast$) with respect to the HR-COSMOS sample. Adopting literature estimates for (1) the excess rate of galaxy-galaxy mergers in intermediate/high-density environments and (2) the average amount of $j_\ast$ loss per merger event, we investigated the possibility that galaxy mergers are mainly responsible for the loss of angular momentum in higher density environments.

Folded orthotropic tape-springs

We consider the large-displacement, elastic folding of orthotropic tape-springs—thin-walled curved strips made from metal and from a woven laminated composite. Bending of the strips leads to a tight localised fold with a characteristic radius, connected on both sides to straight parts by doubly-curved transition, or ploy, regions. We calculate the shapes of these consistent features for a range of orthotropic parameters using geometrically non-linear, compact models. This study is our initial foray into the performance of tape-springs as safety latching mechanisms for aircraft landing gear.