The first neutron star-neutron star (NS-NS) merger was discovered on August 17, 2017 through gravitational waves (GW170817) and followed with electromagnetic observations. This merger was detected in ...an old elliptical galaxy with no recent star formation. We perform a suite of numerical calculations to understand the formation mechanism of this merger. We probe three leading formation mechanisms of double compact objects: classical isolated binary star evolution, dynamical evolution in globular clusters, and nuclear cluster formation to test whether they are likely to produce NS-NS mergers in old host galaxies. Our simulations with optimistic assumptions show current NS-NS merger rates at the level of 10−2 yr−1 from binary stars, 5 × 10−5 yr−1 from globular clusters, and 10−5 yr−1 from nuclear clusters for all local elliptical galaxies (within 100 Mpc3). These models are thus in tension with the detection of GW170817 with an observed rate of 1.5−1.2+3.2$1.5^{+3.2}_{-1.2}$1.5−1.2+3.2 yr−1 (per 100 Mpc3; LIGO/Virgo 90% credible limits). Our results imply that either the detection of GW170817 by LIGO/Virgo at their current sensitivity in an elliptical galaxy is a statistical coincidence; that physics in at least one of our three models is incomplete in the context of the evolution of stars that can form NS-NS mergers; or that another very efficient (unknown) formation channel with a long delay time between star formation and merger is at play.
Context. The external regions of galaxy clusters may be under strong influence of the dark energy, which was discovered by observations of supernovae Ia at redshift z< 1. The presence of the dark ...energy in the gravitational equilibrium equation, with the Einstein Λ term, balances the gravity, and extends the equilibrium configuration more in radius. Aims. We investigate the features of the equilibrium configurations to analyse how the presence of the dark energy affects the density profiles and radial extension by specifying the conditions for which the gravitational equilibrium begins. Methods. We derived the kinetic equation for an equilibrium configuration in presence of dark energy and solved the gravitational equilibrium equation by considering a Maxwell-Boltzmann distribution function with a cut-off in the framework of the Newtonian regime, because the observed velocities of galaxies inside a cluster are much lower than the velocity of light. Results. The prevalence of dark energy effects on the gravity shows a wide region in the W0–ρΛ diagram where equilibrium solutions are not possible. In these particular conditions, the galaxies located in the external regions of a cluster can flow out, following the accelerating expansion of the Universe.
Recent observations of the Virgo cluster and the Local Group suggested that some galaxies are flowing out from their parent cluster. This may be the signature that dark energy (DE) acts significantly ...also on small cosmological scales. By means of direct N-body simulations we performed several simulations, in which the effect of DE and gravity are taken into account, aiming to determine whether DE can produce an outflow of galaxies compatible with observations. Comparing the different simulations, our results suggest that the observed outflow of galaxies is likely due to the local effect of DE.
We performed a series of direct N-body simulations with the aim to follow the dynamical evolution of a galaxy cluster (GC) (\(M_{clus}\simeq 10^{14} M_{\odot}\)) in different environment. The results ...show the formation of heavy sub-structures in the cluster centre in consequence of multiple merging among the innermost galaxies. Moreover we investigate the dynamics of super-massive black holes (SMBHs) residing in the centre of galaxies that form the most massive sub-structure.
The first neutron star-neutron star (NS-NS) merger was discovered on August 17, 2017 through gravitational waves (GW170817) and followed with electromagnetic observations. This merger was detected in ...an old elliptical galaxy with no recent star formation. We perform a suite of numerical calculations to understand the formation mechanism of this merger. We probe three leading formation mechanisms of double compact objects: classical isolated binary star evolution, dynamical evolution in globular clusters and nuclear cluster formation to test whether they are likely to produce NS-NS mergers in old host galaxies. Our simulations with optimistic assumptions show current NS-NS merger rates at the level of 10^-2 yr^-1 from binary stars, 5 x 10^-5 yr^-1 from globular clusters and 10^-5 yr^-1 from nuclear clusters for all local elliptical galaxies (within 100 Mpc^3). These models are thus in tension with the detection of GW170817 with an observed rate 1.5 yr^-1 (per 100 Mpc^3; LIGO/Virgo estimate). Our results imply that either (i) the detection of GW170817 by LIGO/Virgo at their current sensitivity in an elliptical galaxy is a statistical coincidence; or that (ii) physics in at least one of our three models is incomplete in the context of the evolution of stars that can form NS-NS mergers; or that (iii) another very efficient (unknown) formation channel with a long delay time between star formation and merger is at play.
When treating patients with Autism Spectrum Disorder (ASD) the doctor-patient relationship can be very challenging. The dentist is often forced to work under general anaesthesia or conscious ...sedation. Children with ASD are patients with an increased risk of caries due to poor oral hygiene, a cariogenic diet and the use of xerostomal drugs. In this work therapeutic strategies used to treat this kind of patients are evaluated and a new method to treat children with ASD is presented in order to increase awareness about this condition in the dental field.
The Atlas Center (a non-profit organisation in Peurgia, Italy) has developed a software, called paINTeraction, that allows these special children to immerse themselves in a virtual reality with the help of an operator. Through this system the child can explore the dental office (and all its sounds and noises) before the real dental visit, thus connecting to the dental professional, achieving greater compliance and reducing anxiety.
paINTeraction, with the use of digital technology tools, may be particularly well suited to introduce patients to the therapeutic environment, particularly in the dental setting.
This study presents a comprehensive chemodynamical analysis of LAMOST J1109+0754, a bright (V = 12.8), extremely metal-poor (Fe/H = −3.17) star, with a strong r-process enhancement (Eu/Fe = +0.94 ...0.12). Our results are based on the 7D measurements supplied by Gaia and the chemical composition derived from a high-resolution (R ∼ 110,000), high signal-to-noise ratio ( optical spectrum obtained by the 2.4 m Automated Planet Finder Telescope at Lick Observatory. We obtain chemical abundances of 31 elements (from lithium to thorium). The abundance ratios (X/Fe) of the light elements (Z ≤ 30) suggest a massive Population III progenitor in the 13.4-29.5 M mass range. The heavy-element (30 < Z ≤ 90) abundance pattern of J1109+075 agrees extremely well with the scaled-solar r-process signature. We have developed a novel approach to trace the kinematic history and orbital evolution of J1109+0754 with a cOsmologically deRIved timE-varyiNg Galactic poTential (the ORIENT) constructed from snapshots of a simulated Milky Way analog taken from the Illustris-TNG simulation. The orbital evolution within this Milky Way-like galaxy, along with the chemical abundance pattern, implies that J1109+0754 likely originated in a low-mass dwarf galaxy located ∼60 kpc from the center of the Galaxy, which was accreted ∼6-7 Gyr ago, and that the star now belongs to the outer-halo population.
Introducción: La prevalencia de infecciones periprotésicas luego de una artroplastia total de cadera primaria es aproximadamente del 2%. El objetivo de este estudio fue determinar si existen ...diferencias estadísticamente significativas entre la tasa de infecciones periprotésicas agudas ante una profilaxis antibiótica extendida (7 días) y una profilaxis antibiótica estándar (24 h).
Materiales y Métodos: Se realizó un estudio clínico prospectivo, entre julio de 2021 y mayo de 2022, que incluyó a 28 adultos con fractura de cadera sometidos a una artroplastia primaria que recibieron profilaxis antibiótica con cefalosporinas de primera generación durante 7 días a quienes se comparó con 95 adultos con fracturas de cadera con una artroplastia primaria y profilaxis antibiótica de 24 h, extraídos de una base de datos secundaria del registro del hospital.
Resultados: La tasa de infecciones periprotésicas agudas fue del 10,71% en el grupo con profilaxis extendida y del 17,89% en quienes recibieron profilaxis estándar, sin diferencias estadísticamente significativas (p = 0,36).
Conclusiones: Si bien, según la bibliografía disponible, la prolongación de la profilaxis antibiótica puede ser una medida simple, segura y rentable para contrarrestar los factores no modificables del paciente y asíreducir las infecciones periprotésicas; en este estudio, no se demostró que la profilaxis antibiótica extendida disminuya la tasa de infecciones periprotésicas agudas a los 30 días en pacientes con artroplastias de cadera primarias.
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