Collision Debris Research Articles

Light curves and spectra for theoretical models of high-velocity red-giant star collisions

High-velocity stellar collisions driven by a supermassive black hole (BH) or BH-driven disruptive collisions in dense, nuclear clusters can rival the energetics of supergiant star explosions following the gravitational collapse of their iron core. Starting from a sample of red-giant star collisions simulated with the hydrodynamics code AREPO, we generated photometric and spectroscopic observables using the nonlocal thermodynamic equilibrium time-dependent radiative transfer code CMFGEN. Collisions from more extended giants or more violent collisions (with higher velocities or smaller impact parameters) yield bolometric luminosities on the order of 1043 erg s−1 at 1 d, evolving on a timescale of a week to a bright plateau at ∼1041 erg s−1 before plunging precipitously after 20–40 d at the end of the optically thick phase. This luminosity falls primarily in the UV in the first few days, thus when it is at its maximum, and shifts to the optical thereafter. Collisions at lower velocities or from less extended stars produce ejecta that are fainter but can remain optically thick for up to 40 d if they have a low expansion rate. This collision debris shows a similar spectral evolution as that observed or modeled for Type II supernovae from blue-supergiant star explosions, differing only in the more rapid transition to the nebular phase. Such BH-driven disruptive collisions should be detectable by high-cadence surveys in the UV such as ULTRASAT.

The evolution of collision debris near the ν6 secular resonance and its role in the origin of terrestrial water

ABSTRACT This work presents novel findings that broaden our understanding of the amount of water that can be transported to the Earth. The key innovation lies in the combined usage of smoothed particle hydrodynamics (SPH) and N-body codes to assess the role of collision fragments in water delivery. We also present a method for generating initial conditions that enables the projectile to impact at the designated location on the target’s surface with the specified velocity. The primary objective of this study is to simulate giant collisions between two Ceres-sized bodies by SPH near the ν6 secular resonance and follow the evolution of the ejected debris by numerical N-body code. With our method 6 different initial conditions for the collision were determined, and the corresponding impacts were simulated by SPH. Examining the orbital evolution of the debris ejected after collisions, we measured the amount of water delivered to the Earth, which is broadly 0.001 ocean equivalents of water, except in one case where one large body transported 7 per cent oceans of water to the planet. Based on this and taking into account the frequency of collisions, the amount of delivered water varies between 1.2 and 8.3 ocean’s worth of water, depending on the primordial disc mass. According to our results, the prevailing external pollution model effectively accounts for the assumed water content on the Earth, whether it’s estimated at 1 or 10 ocean’s worth of water.

Characterization of low surface brightness structures in annotated deep images

Context. The identification and characterization of low surface brightness (LSB) stellar structures around galaxies such as tidal debris of ongoing or past collisions is essential to constrain models of galactic evolution. So far most efforts have focused on the numerical census of samples of varying sizes, either through visual inspection or more recently with deep learning. Detailed analyses including photometry have been carried out for a small number of objects, essentially because of the lack of convenient tools able to precisely characterize tidal structures around large samples of galaxies. Aims. Our goal is to characterize in detail, and in particular obtain quantitative measurements, of LSB structures identified in deep images of samples consisting of hundreds of galaxies. Methods. We developed an online annotation tool that enables contributors to delineate the shapes of diffuse extended stellar structures with precision, as well as artifacts or foreground structures. All parameters are automatically stored in a database which may be queried to retrieve quantitative measurements. We annotated LSB structures around 352 nearby massive galaxies with deep images obtained with the Canada-France-Hawaii Telescope as part of two large programs: Mass Assembly of early-Type GaLAxies with their fine Structures and Ultraviolet Near Infrared Optical Northern Survey/Canada-France Imaging Survey. Each LSB structure was delineated and labeled according to its likely nature: stellar shells, streams associated with a disrupted satellite, tails that formed in major mergers, ghost reflections, or cirrus. Results. From our database containing 8441 annotations, the area, size, median surface brightness, and distance to the host of 228 structures were computed. The results confirm the fact that tidal structures defined as streams are thinner than tails, as expected by numerical simulations. In addition, tidal tails appear to exhibit a higher surface brightness than streams (by about 1 mag), which may be related to different survival times for the two types of collisional debris. We did not detect any tidal feature fainter than 27.5 magarcsec−2, while the nominal surface brightness limits of our surveys range between 28.3 and 29 magarcsec−2, a difference that needs to be taken into account when estimating the sensitivity of future surveys to identify LSB structures. Conclusions. We compiled an annotation database of observed LSB structures around nearby massive galaxies including tidal features that may be used for quantitative analysis and as a training set for machine learning algorithms.

Bringing into Focus the Debris of Heavy-Ion Collisions

Bringing into Focus the Debris of Heavy-Ion Collisions

Study of Pb-Pb and Pb-p Collision Debris in the CERN LHC in View of HL-LHC Operation

Study of Pb-Pb and Pb-p Collision Debris in the CERN LHC in View of HL-LHC Operation

Collision risk prediction for constellation design

INDEMN is an object-oriented program dedicated to the modeling of the evolution of the densities of space objects. Following the work achieved by D. Kessler (1978) and by other authors more recently (G. L. Somma, IAC 2016, A6-IP3; A. Rossi, DPPS 2004, 197), the dynamical model is based on a source and sink approach for various altitudes. The source terms represent the future launches, the explosion of intact spacecrafts, and the collision between objects. Different collision cross sections are used for the various types of objects and the number of debris generated is based on the NASA break-up model. The sink terms are the drag and the end-of-life de-orbitation for the satellites launched after 2009, with a controllable success rate. The code was validated against former simulations performed with statistical and semi-deterministic models. In addition to the classical object types featured in several statistical codes, which are intact objects, explosion debris, and collision debris, a new type representing the satellites of a specific constellation is included. These satellites orbit with altitudes close to 1200 km and they can perform collision avoidance maneuvers as long as they are fully operational. It is shown that, under realistic assumptions, if only one primary collision occurs at an altitude of 800 km, the probability of a collision involving a constellation satellite becomes larger than 2% by 2035, which highly jeopardizes the satellite constellation as a whole.

A coupled multiphysics FEM model to investigate electromagnetic, thermal and mechanical effects in complex assemblies: The design of the High-Luminosity Large Hadron Collider beam screen

• A multiphysics model is proposed to assess the mechanical response of a complex assembly to a magnetic field variation. • The one-way and two-way couplings between the magnetic, thermal and mechanical physics are fully investigated. • The two-way coupling between the magnetic and thermal physics turns out to lower the induced forces up to approximately 40%. • Dynamic effects such as self-inductance phenomena lower and delay in time the induced forces for highly conductive materials. In the framework of the High-Luminosity Large Hadron Collider (HL-LHC) project, new beam screens will be installed by 2024 within the cold bore of the superconducting magnets. The beam screen is an octagonal shaped pipe that shields the 1.9 K magnet cryogenic system from the heat loads and damage to the magnet coils that would be otherwise induced by the highly penetrating collision debris. It also ensures that proper vacuum conditions required for the stability of the beam are met. A failure scenario of the beam screen is represented by the magnet quench, a resistive transition of the superconducting magnets, that can compromise its mechanical integrity. During a quench the magnet gradient of the quadrupole, in which the beam screen is inserted, decays from 140 T/m to about 0 T/m in 0.4 s inducing high magnitude forces in the assembly. Understanding the magnetic, thermal and mechanical behaviours of the beam screen assembly during the quench is critical to enable its effective design and operation. A numerical model, that can accurately predict the behaviours of the beam screen during a magnet quench, has been developed. Compared to the analytical formulations used to design the beam screen currently installed in the LHC, the multiphysics FEM model developed in this research introduces multiple elements of novelty and improved performance. First, self-inductance effects are accounted for and found to reduce the induced forces up to approximately 2000% at high electrical conductivity values. Second, the one-way and two-way coupling of the magnetic with the mechanical and thermal interfaces are explored and the best trade-off is defined. Third, the mechanical response of the assembly is evaluated dynamically over the evolution of the magnetic field decay rather than just in a quasi-static manner. Fourth, three dimensional geometries can also be studied enabling the design of the components to be placed along the beam axis. The model has been verified by comparison to a closed form expression showing the advantages of considering self-inductance phenomena. The mechanical integrity of the new beam screen has been demonstrated and a less conservative design has been obtained, which has permitted to relax the tight constraints on interfacing systems. Amongst other applications, the model has already been applied at CERN to support the conceptual design of an ad-hoc beam screen for the Future Circular Collider (FCC).

AI in Action: AI's early proving ground: the hunt for new particles

High-energy physicists use machine learning to sift through the debris of particle collisions

Numerical Simulation on Concrete Median Barrier for Reducing Concrete Fragment Under Harsh Impact Loading of a 25-ton Truck

Recently, there was a collision accident involving vehicle–concrete median barrier in South Korea, and unfortunately, passengers on the opposite direction road were killed by the flying broken pieces of concrete generated by the collision. Primarily after this accident, we felt the need for developing an improved concrete median barrier up to level of SB6 impact severity in order to minimize the amount of broken pieces of concrete and any possibility of traffic accident casualty under the impact loading of truck. Accordingly, in this study, several designs of concrete median barriers have been examined, and a preliminary study has been conducted for developing and verifying appropriate collision model. First, type of vehicle was selected based on impact analysis on rigid wall. Then, the effects of element size and other key parameters on the capacity of the concrete median barrier under impact were studied. It was found that the key parameters for controlling behaviors of the median barrier under impact loading were contact option, threshold value, and mesh and boundary conditions. Furthermore, as a parametric study, effect of geometry and amount of wire-mesh or steel rebar in concrete median barrier on impact resistances of median barrier for reducing the collision debris were investigated. The amount of volume loss after the collision of truck was compared for various reinforcement ratios.

A Postulated Planetary Collision, the Terrestrial Planets, the Moon and Smaller Solar-System Bodies

In a scenario produced by the Capture Theory of planetary formation, a collision between erstwhile solar-system giant planets, of masses 798.75 and 598.37 M⊕, is simulated using smoothed-particle hydrodynamics. Due to grain-surface chemistry that takes place in star-forming clouds, molecular species containing hydrogen, with a high D/H ratio taken as 0.01, form a layer around each planetary core. Temperatures generated by the collision initiate D–D reactions in these layers that, in their turn, trigger a reaction chain involving heavier elements. The nuclear explosion shatters and disperses both planets, leaving iron-plus-silicate stable residues identified as a proto-Venus and proto-Earth. A satellite of one of the colliding planets, captured or retained by the proto-Earth core, gave the Moon; two massive satellites released into heliocentric orbits became Mercury and Mars. For the Moon and Mars, abrasion of their surfaces exposed to collision debris results in hemispherical asymmetry. Mercury, having lost a large part of its mantle due to massive abrasion, reformed to give the present high-density body. Debris from the collision gave rise to asteroids and comets, much of the latter forming an inner reservoir stretching outwards from the inner Kuiper Belt that replenishes the Oort Cloud when it is depleted by a severe perturbation. Other features resulting from the outcome of the planetary collision are the relationship of Pluto and Triton to Neptune, the presence of dwarf planets and light-atom isotopic anomalies in meteorites.

Steady State Heat Deposits Modeling in the ${\hbox {Nb}}_{3}{\hbox {Sn}}$ Quadrupole Magnets for the Upgrade of the LHC Inner Triplet

In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. In previous papers, a Network Model has been used to study the thermodynamic behavior of magnet coils and to calculate the quench levels in the LHC magnets for expected beam loss profiles. This model was subsequently used for thermal analysis and design optimization of quadrupole magnets, which LARP (US LHC Accelerator Research Program) is developing for possible use in the LHC luminosity upgrade. For these new magnets, the heat transport efficiency from the coil to the helium bath needs to be determined and optimized. In this paper the study of helium cooling channels and the heat evacuation scheme are presented and discussed.

Counter-orbiting tidal debris as the origin of the MW DoS

The Milky Way satellite galaxies show a phase-space distribution that is not expected from the standard scenario of galaxy formation. This is a strong hint at them being of tidal origin, which would naturally explain their spacial distribution in a disc of satellites. It is shown that also their orbital directions can be reproduced with the debris of galaxy collisions. Both co- and counter-orbiting satellites are formed naturally in merger and fly-by interactions.

STAR FORMATION IN COLLISION DEBRIS: INSIGHTS FROM THE MODELING OF THEIR SPECTRAL ENERGY DISTRIBUTION

During galaxy-galaxy interactions, massive gas clouds can be injected into the intergalactic medium which in turn become gravitationally bound, collapse and form stars, star clusters or even dwarf galaxies. The objects resulting from this process are both "pristine", as they are forming their first generation of stars, and chemically evolved because the metallicity inherited from their parent galaxies is high. Such characteristics make them particularly interesting laboratories to study star formation. After having investigated their star-forming properties, we use photospheric, nebular and dust modeling to analyze here their spectral energy distribution (SED) from the far-ultraviolet to the mid-infrared regime for a sample of 7 star-forming regions. Our analysis confirms that the intergalactic star forming regions in Stephan's Quintet, around Arp 105, and NGC 5291, appear devoid of stellar populations older than 10^9 years. We also find an excess of light in the near-infrared regime (from 2 to 4.5 microns) which cannot be attributed to stellar photospheric or nebular contributions. This excess is correlated with the star formation rate intensity suggesting that it is probably due to emission by very small grains fluctuating in temperature as well as the polycyclic aromatic hydrocarbons (PAH) line at 3.3 micron. Comparing the attenuation via the Balmer decrement to the mid-infrared emission allows us to check the reliability of the attenuation estimate. It suggests the presence of embedded star forming regions in NGC 5291 and NGC 7252. Overall the SED of star-forming regions in collision debris (and Tidal Dwarf Galaxies) resemble more that of dusty star-forming regions in galactic disks than to that of typical star-forming dwarf galaxies.

Value of paint transfer and damage examinations in the forensic investigation of boat collisions

Key information sought in a boat collision investigation includes: path and direction of boats, speed, impact angle, impact site, and evasive actions. Boat collision and road traffic collision investigations are similar in application of dynamics, Newton's Laws and kinetic energy, and in examiningdamages, contact evidence, and navigation lights. Unlike road accidents, boat collisions do not leave skidmarks and scars on roads. Road vehicles usually follow clearly marked lanes and directions and come to rest on the ground after collision, unlike boats in open seas. The positions and orientations of boats when investigated can differ markedly from those immediately after engagement. Finding collision debris is more difficult in boat collisions— debris could sink to a murky seabed or disperse and float away from the impact site. Like road vehicles, boats may suffer full impact or partial impact collisions. A displacement hull may cause a slamming (full impact) or a sideswipe, dependingwhether impact occurredator away from the impactedboat's point of rotation. A high-speed boat with a planing hull may ramp up onto a low-profile boat, pushing it down into water. The nature and extent of damages depend on relative sizes, boat design, construction, strength of the structural framework, hard parts, and shell plating materials. 3-D movements such as rotation (yaw), pitching, and rolling are easier and more pronounced on water. Flooding due to the entry of water can critically affect buoyancy, centre of gravity and stability, and may capsize and sink the swamped boat. The analysis of damages on the gunwale, bow, deck, and hull, complemented by identification of paint transfers (chips, smears and rub-off), can reveal contacting surfaces and the directionality of the colliding vessels. Contact damage and induced damage include: holes, dents, imprints, bending, collapse, protrusions, fractures, abrasion, scrapes (scoring), and scuffmarks. Damages in the boat and injuries to occupants may indicate occupant kinematics. If undisturbed, the positions of the throttle, levers, gauges and switches, propellers and rudder provide a critical snapshot at collision. GPS equipment and voyage data recorders provide critical information, but unfortunately are usually found only on larger and more sophisticated vessels or military and law enforcement boats. Toxicological analysis indicates whether the boat operator was under influence of medication, alcohol or drugs. Eyewitness accounts must be carefully evaluated against physical evidence. Case studieswill be used to illustrate the value of damage and paint evidence in boat collision investigations.

COLLISIONAL DEBRIS AS LABORATORIES TO STUDY STAR FORMATION

In this paper we address the question whether star formation is driven by local processes or the large scale environment. To do so, we investigate star formation in collisional debris where the gravitational potential well and velocity gradients are shallower and compare our results with previous work on star formation in non-interacting spiral and dwarf galaxies. We have performed multiwavelength spectroscopic and imaging observations (from the far-ultraviolet to the mid-infrared) of 6 interacting systems, identifying a total of 60 star-forming regions in their collision debris. Our analysis indicates that in these regions a) the emission of the dust is at the expected level for their luminosity and metallicity, b) the usual tracers of star formation rate display the typical trend and scatter found in classical star forming regions, and c) the extinction and metallicity are not the main parameters governing the scatter in the properties of intergalactic star forming regions; age effects and variations in the number of stellar populations, seem to play an important role. Our work suggests that local properties such as column density and dust content, rather than the large scale environment seem to drive star formation. This means that intergalactic star forming regions can be used as a reliable tool to study star formation.

Collision debris increases risk to Earth-observing satellites

Collision debris increases risk to Earth-observing satellites

Toward the AdS/CFT gravity dual for high energy collisions. III. Gravitationally collapsing shell and quasiequilibrium

The equilibration of matter and onset of hydrodynamics can be understood in the AdS/CFT context as a gravitational collapse process, in which "collision debris" create a horizon. In this paper we consider the simplest geometry possible, a flat shell (or membrane) falling in the holographic direction toward the horizon. The metric is a combination of two well known solutions: thermal AdS above the shell and pure AdS below, while motion of the shell is given by the Israel junction condition. Furthermore, when the shell motion can be considered slow, we were able to solve for two-point functions of all boundary stress tensor and found that an observer on the boundary sees a very peculiar $quasiequilibrium$: while the average stress tensor $<T_{\mu\nu>}$ contains the equilibrium plasma energy and pressure at all times, the spectral densities of the correlators(related with occupation probabilities of the modes) reveal additional oscillating terms absent in equilibrium. This is explained by the "echo" phenomenon, a partial return of the field coherence at certain "echo" times.

Analysis methodologies for assessing micro-meteoroids and orbital debris risk to spacecraft

Every space system is exposed to the risk of collision with space debris and micro-meteoroids throughout its orbital life. Because of the large collision velocities, debris or meteoroids in the millimetre to centimetre range may cause significant damage to a spacecraft, which can result in potential generation of debris, loss of equipment and mission failure. The current paper deals with the probabilistic risk assessment of spacecraft survivability under micro-meteoroids and orbital debris (MMOD) impact. The typical process to calculate the MMOD induced risk is summarized and the main uncertainties and limitations affecting the assessment are discussed together with a simple example of a MMOD risk assessment performed for the European spaceship automated transfer vehicle. In order to increase the level of accuracy of MMOD risk assessments, improvements are necessary in the following critical areas: failure criteria analysis, project-dedicated hypervelocity impact testing and debris environment models.

SPH simulations of clumps formation by dissipative collision of molecular clouds

We performed computer simulations of interstellar cloud-cloud collisions using the three-dimensional smoothed particle magnetohydrodynamics method. In order to study the role of the magnetic eld on the pro- cess of collision-triggered fragmentation, we focused our attention on head-on supersonic collisions between two identical spherical molecular-clouds. Two extreme congurations of the magnetic eld were adopted: parallel and perpendicular to the initial clouds motion. The initial magnetic eld strength was approximately 12.0 G. In the parallel case, much more of the collision debris were retained in the shocking region than in the non-magnetic case where gas escaped freely throughout the symmetry plane. Dierently from the non-magnetic case, eddy-like vortices were formed. The regions of highest vorticity and the the regions of highest density are oset. We found clumps formation only in the parallel case, however, they were larger, hotter and less dense than in the analogous non-magnetic case. In the perpendicular case, the compressed eld works as a magnetic wall, preventing a stronger compression of the colliding clouds. This last eect inhibits direct contact of the two clouds. In both cases, we found that the eld lines show a chaotic aspect in large scales. Also, the eld magnitude is considerably amplied in the shock layer. However, the eld distribution is almost coherent in the higher density regions.

Tidal Dwarf Galaxies

We review the observational evidences for tidal dwarf galaxies, a class of small galaxies formed out of the tidal debris of collisions between massive galaxies. Tidal dwarfs are found far from the interacting parent galaxies, associated with massive clouds of atomic hydrogen located at the tip of long tidal tails. These newly formed galaxies are among the best cases for the study of galaxy formation in the nearby Universe.