Hasil untuk "Astronomy"

M. Lavery, F. Speirits, S. Barnett et al.

S. Hild, M. Abernathy, F. Acernese et al.

Advanced gravitational wave detectors, currently under construction, are expected to directly observe gravitational wave signals of astrophysical origin. The Einstein Telescope (ET), a third-generation gravitational wave detector, has been proposed in order to fully open up the emerging field of gravitational wave astronomy. In this paper we describe sensitivity models for ET and investigate potential limits imposed by fundamental noise sources. A special focus is set on evaluating the frequency band below 10 Hz where a complex mixture of seismic, gravity gradient, suspension thermal and radiation pressure noise dominates. We develop the most accurate sensitivity model, referred to as ET-D, for a third-generation detector so far, including the most relevant fundamental noise contributions.

B. Thidé, H. Then, J. Sjöholm et al.

We show numerically that vector antenna arrays can generate radio beams that exhibit spin and orbital angular momentum characteristics similar to those of helical Laguerre-Gauss laser beams in paraxial optics. For low frequencies (< or = 1 GHz), digital techniques can be used to coherently measure the instantaneous, local field vectors and to manipulate them in software. This enables new types of experiments that go beyond what is possible in optics. It allows information-rich radio astronomy and paves the way for novel wireless communication concepts.

Euclid Collaboration Y. Mellier, Abdurro’uf, J. Barroso et al.

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. is a medium-class mission in the Cosmic Vision 2015--2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14\,000\,deg$^2$ of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

Billi A., Monaco L., Ferraro F. R. et al.

We studied the rotational velocities of a sample of blue straggler stars (BSSs) and reference stars belonging to the Galactic globular cluster NGC 1851 using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT. After field decontamination based on radial velocities and proper motions, the final sample of member stars was composed of 15 BSSs and 45 reference stars populating the red giant and horizontal branches of the cluster. In agreement with previous findings, the rotation of the reference stars is negligible in general (lower than 15 km s−1). In contrast, the rotational velocity is high (up to ~150 km s−1) for a subsample of BSSs. We found 4 fast-rotating BSSs (defined as stars that spin faster than 40 km s−1), which corresponds to a percentage of 27 ± 14%. This result delineates a monotonically decreasing trend (instead of a step function) between the percentage of fast-spinning BSSs and the central concentration and density of the host cluster. This supports a scenario in which recent BSS formation preferentially occurs in low-density environments from the evolution of binary systems.

Duaa Abdullah, Jasem Hamoud

In this paper, we highlight the influence of Arab/Islamic civilization in the field of the history of astronomy on European historians. We also aim to elucidate the stance of Orientalists toward the study of Arab sciences and to clarify their orientations, with a particular focus on astronomy, while revealing the significant role played by Arab scholars in this domain and the impact of their contributions-especially astronomical tables (zij)-on Western astronomers. Furthermore, we have clarified the mechanisms of transmission of Arab sciences, particularly astronomy, from Arab scholars to Western scholars, and the role of Arab astronomers in Western civilization. In addition, we address the contributions of Arab scholars to the development of astronomy and the perspective of Orientalists, particularly David King, regarding this matter. We also underscore the importance of Orientalists' works in analyzing Arab/Islamic scholarly output, identifying its influence on the West in the field of astronomy, and demonstrating how Western scholars benefited from translations of Arabic books in this discipline. In this paper, we adopt the historical retrieval methodology, by referencing previously documented astronomical information and contributions, with an emphasis on the processes of transmission of these sciences from the Arabs to the West.

The PADME collaboration, S. Bertelli, F. Bossi et al.

Abstract The PADME experiment at the Frascati DAΦNE LINAC has performed a search for the hypothetical X17 particle, with a mass of around 17 MeV, by scanning the energy of a positron beam striking a fixed target. The X17 should be produced from the resulting e + e − annihilation. Since the expected mass of this particle is only roughly known, data sidebands cannot be clearly defined. Furthermore, the need to keep the analysis blind to potentially sizable signal contributions prevents a clear assessment even of the quality of the data sample in this search. In light of these challenges, this paper presents an innovative strategy adopted by the PADME Collaboration to perform data quality checks without disclosing the X17 sample. Moreover, the procedure designed to eventually unblind the data is described, together with the statistical approach adopted to extract the limits on the coupling between the X17 and the Standard Model.

Dalya Baron, Karin M. Sandstrom, Jessica Sutter et al.

The structure and chemistry of the dusty interstellar medium (ISM) are shaped by complex processes that depend on the local radiation field, gas composition, and dust grain properties. Of particular importance are polycyclic aromatic hydrocarbons (PAHs), which emit strong vibrational bands in the mid-infrared, and play a key role in the ISM energy balance. We recently identified global correlations between PAH band and optical line ratios across three nearby galaxies, suggesting a connection between PAH heating and gas ionization throughout the ISM. In this work, we perform a census of the PAH heating–gas ionization connection using ∼700,000 independent pixels that probe scales of 40–150 pc in 19 nearby star-forming galaxies from the PHANGS survey. We find a universal relation between $\mathrm{log}$ PAH(11.3 μ m/7.7 μ m) and $\mathrm{log}$ ([S ii ]/H α ) with a slope of ∼0.2 and a scatter of ∼0.025 dex. The only exception is a group of anomalous pixels that show unusually high (11.3 μ m/7.7 μ m) PAH ratios in regions with old stellar populations and high starlight-to-dust emission ratios. Their mid-infrared spectra resemble those of elliptical galaxies. Active galactic nucleus hosts show modestly steeper slopes, with a ∼​​​​​​10% increase in PAH(11.3 μ m/7.7 μ m) in the diffuse gas on kiloparsec scales. This universal relation implies an emerging simplicity in the complex ISM, with a sequence that is driven by a single varying property: the spectral shape of the interstellar radiation field. This suggests that other properties, such as gas-phase abundances, gas ionization parameter, and grain charge distribution, are relatively uniform in all but specific cases.

Yisheng Gao, Yingyu Wang, Jianye Zhang et al.

Souvik Manik, Netai Bhukta, Sabyasachi Pal et al.

Giant radio quasars (GRQs) are radiatively efficient radio-loud active galactic nuclei that propel large-scale radio jets with projected lengths of more than 0.7 Mpc. We report the discovery of 53 new GRQs within a redshift range of 0.14–2.38, as well as 316 new nongiant extended radio quasars (NGERQs) within a redshift range of 0.037–3.356, from the TIFR GMRT Sky Survey Alternative Data Release 1. The projected lengths of the new GRQs range from 0.7 to ∼2.2 Mpc, and the projected lengths of the new NGERQs range from 67 to 695 kpc. We found that the spectral indices of GRQs are statistically similar to those of NGERQs. We have also investigated the large-scale environmental and jet asymmetry properties of the combined sample, which includes new sources and previously discovered extended radio quasars (ERQs) from the literature. The results indicate that at least 13% of GRQs and 14% of NGERQs in the sample are located in galaxy groups and cluster environments. Similar lower-bound percentages reside near large-scale filamentary structures, with median projected distances of 5.9 and 4.3 Mpc from their respective host quasars. At the current survey noise levels, we find that the projected lengths of ERQs in our sample at z ≥ 1 are smaller than those at z  < 1. Furthermore, GRQs at z ≥ 1 exhibit greater arm-length asymmetry compared to NGERQs, which may be attributed to an asymmetric environment.

Camille Granier, Daniel Grošelj, Luca Comisso et al.

We investigate the onset of driven collisionless reconnection and plasmoid formation in a magnetically dominated pair plasma, using 2D particle-in-cell simulations. Two force-free flux tubes of radius R are initially pushed together with a prescribed velocity, forming a current sheet whose width shrinks until reconnection sets in. Even in our largest simulation with R  ≈ 1600 plasma skin depths, the sheet thickness at reconnection onset is comparable to the skin depth. Plasmoid chains develop when the sheet length-to-width aspect ratio A  ≳ 30. In the strongly magnetized limit, the onset of reconnection occurs in roughly 2–6 light-crossing times, depending on the imposed driving timescale, which controls the duration of the thinning phase. In the subsequent nonlinear merging phase, the evolution becomes effectively independent of the initially imposed velocity, leading to magnetic-energy dissipation consistent with a normalized reconnection rate ∼0.1. Our results have important implications for explosive release of magnetic energy in magnetospheres of astrophysical compact objects and their surroundings.

Younes Chahid, Carolyn Atkins, Greg Lister et al.

Despite the established role of additive manufacturing (AM) in aerospace and medical fields, its adoption in astronomy remains low. Encouraging AM integration in a risk-averse community necessitates documentation and dissemination of previous case studies. The objective of this study is to create the first review of AM in astronomy hardware, answering: where is AM currently being used in astronomy, what is the status of its adoption, and what challenges are preventing its widespread use? The review starts with an introduction to astronomical instruments size/cost challenges, alongside the role of manufacturing innovation. This is followed by highlighting the benefits/challenges of AM and used materials/processes in both space-based and ground-based applications. The review case studies include mirrors, optomechanical structures, compliant mechanisms, brackets and tooling applications that are either in research phase or are implemented.

Manjuleshwar Panda, Yogesh Chandra

With its immensity and numerous mysteries waiting to be solved, the cosmos has always captivated humankind. A ground-breaking field that has given us a profound understanding of the mysteries of the cosmos is radio astronomy. This paper presents a comprehensive overview of radio astronomy, exploring its techniques, discoveries, and the profound insights it offers into celestial objects. Radio astronomy, which uses radio waves to analyse celestial phenomena, has completely changed how we think about the universe. This field has given us crucial information about the formation of stars, galaxies, and other celestial objects through the analysis of radio emissions. Radio astronomy has enabled researchers to study cosmic processes that are undetectable to the human eye by penetrating the furthest reaches of space. We explore radio astronomy techniques in this article, revealing how it can be used to see through interstellar dust and collect signals from the universe's furthest reaches. Pulsars, quasars, and cosmic microwave background radiation are significant discoveries that have helped astronomers understand dark matter and dark energy in great detail. We also look into how radio astronomy might be used in cosmology and astrophysics. In conclusion, radio astronomy has become a potent tool for solving the cosmos' riddles. Its capacity for the detection and analysis of radio emissions has produced a fundamental understanding of the beginnings and evolution of the universe. Radio astronomy continues to advance our understanding of the cosmos and arouses interest in additional cosmic research by shedding light on celestial objects that are invisible to the human eye.

Phung Van Dong, Tran Ngoc Hung, Duong Van Loi

Abstract Quark has an electric charge either $$-1/3$$ - 1 / 3 or 2/3 and a baryon number 1/3, where the divisions 3’s match the color number. Although the electric charge and the baryon number have a nature distinct from the color charge, the matching is necessary for the standard model or a relevant $$B-L$$ B - L extension consistent at quantum level, since the relevant anomaly $$[SU(2)_L]^2U(1)_A$$ [ S U ( 2 ) L ] 2 U ( 1 ) A for $$A=Y$$ A = Y or $$B-L$$ B - L must vanish. If elementary particles have a new U(1) charge differently from A, such anomaly is not cancelled for each family. However, if we demand that the anomaly is cancelled over all families, this relates the color number to the family number instead of the electric charge and baryon number, and interestingly the family number guides us to a novel U(1) theory. We will discuss the implication of this theory for neutrino mass, recent W-boson mass anomaly, FCNC, and particle colliders.

Christian I. Johnson, Annalisa Calamida, Justin A. Kader et al.

Wide-field and deep DECam multiband photometry, combined with HST data for the core of the Galactic globular cluster NGC 2808, allowed us to study the distribution of various stellar subpopulations and stars in different evolutionary phases out to the cluster tidal radius. We used the C _ugi = ( u − g ) − ( g − i ) index to identify three chemically distinct subpopulations along the red giant branch and compared their spatial distributions. The most light-element-enriched subpopulation (P3) is more centrally concentrated; however, it shows a more extended distribution in the external regions of the cluster compared to the primordial (P1) and intermediate (P2) composition populations. Furthermore, the P3 subpopulation centroid is off-center relative to those of the P1 and P2 groups. We also analyzed the spatial distribution of horizontal branch stars and found that the relative fraction of red horizontal branch stars increases for radial distances larger than ≈1.′5, while that of the blue and hotter stars decreases. These new observations, combined with literature spectroscopic measurements, suggest that the red horizontal branch stars are the progeny of all the stellar subpopulations in NGC 2808, i.e., primordial and light-element enhanced, while the blue stars are possibly the result of a combination of the “hot-flasher” and the “helium-enhanced” scenarios. A similar distribution of different red giant branch subpopulations and horizontal branch stars was also found for the most massive Galactic globular cluster, ω Cen, based on combined DECam and HST data, which suggests that the two may share a similar origin.

Wan-Jin Lu, Zhen-Yin Zhao, F. Y. Wang et al.

Fast radio bursts (FRBs) are energetic millisecond phenomena in the radio band. Polarimetric studies of repeating FRBs indicate that many of these sources occupy extreme and complex magnetoionized environments. Recently, a frequency-dependent depolarization has been discovered in several repeating FRBs. However, the temporal evolution of polarization properties is limited by the burst rate and observational cadence of telescopes. In this Letter, the temporal evolution of depolarization in repeating FRB 20201124A is explored. Using the simultaneous variation of rotation measure and dispersion measure, we also measure the strength of a magnetic field parallel to the line of sight. The strength ranges from a few μ G to 10 ^3 μ G. In addition, we find that the evolution of depolarization and magnetic field traces the evolution of rotation measure. Our result supports that the variation of depolarization, rotation measure, and the magnetic field are determined by the same complex magnetoionized screen surrounding the FRB source. The derived properties of the screen are consistent with the wind and the decretion disk of a massive star.

Mohsen Javaherian, Halime Miraghaei, Hooman Moradpour

The morphology of radio galaxies can provide significant clues to describe the formation and evolution of galaxies in the Universe. Here, we aim to extract the morphological parameters of radio galaxies and define symmetry criteria as some of the essential factors of their shape explanations. We employed 67 radio galaxies, which include Fanaroff–Riley type 1 and type 2 galaxies, and their radio images from the FIRST and LoTSS surveys. We developed an automatic segmentation process to extract morphological properties such as the size of objects, eccentricity, and orientation of segmented regions from data sets. Using a maximum likelihood estimator, we show that the distributions of sizes follow a power-law function with exponents of −0.39 ± 0.06 and −0.55 ± 0.05 for the FIRST and LoTSS data, respectively. We found that type 2 radio galaxies have slightly lower eccentricities than type 1. We studied the relationships between size, eccentricity, and redshift in scatter plots. The size of galaxies (kpc ^2 ) demonstrates gently growing trends with increasing eccentricity in their scatter plots. We discussed the possible effect of the redshifts of the galaxies on this result. Depending on the number of segmented regions, we defined symmetry criteria based on proximity to the center of a galaxy in the optical band, eccentricity, orientation, and the quarter ( q ) of appearance in the image. We found that the mean symmetry obtained for two segmented regions that mainly emerged in two quarters via the condition of $| {q}^{{\prime} }-q^{\prime\prime} | =2$ has a higher value than those obtained for other cases.

Francisco Ley, Ellen G. Zweibel, Mario Riquelme et al.

Turbulence driven by active galactic nuclei activity, cluster mergers, and galaxy motion constitutes an attractive energy source for heating the intracluster medium (ICM). How this energy dissipates into the ICM plasma remains unclear, given its low collisionality and high magnetization (precluding viscous heating by Coulomb processes). Kunz et al. proposed a viable heating mechanism based on the anisotropy of the plasma pressure under ICM conditions. The present paper builds upon that work and shows that particles can be heated by large-scale turbulent fluctuations via magnetic pumping. We study how the anisotropy evolves under a range of forcing frequencies, what waves and instabilities are generated, and demonstrate that the particle distribution function acquires a high-energy tail. For this, we perform particle-in-cell simulations where we periodically vary the mean magnetic field B ( t ). When B ( t ) grows (dwindles), a pressure anisotropy P _⊥ > P _∥ ( P _⊥ < P _∥ ) builds up ( P _⊥ and P _∥ are, respectively, the pressures perpendicular and parallel to B ( t )). These pressure anisotropies excite mirror ( P _⊥ > P _∥ ) and oblique firehose ( P _∥ > P _⊥ ) instabilities, which trap and scatter the particles, limiting the anisotropy, and providing a channel to heat the plasma. The efficiency of this mechanism depends on the frequency of the large-scale turbulent fluctuations and the efficiency of the scattering the instabilities provide in their nonlinear stage. We provide a simplified analytical heating model that captures the phenomenology involved. Our results show that this process can be relevant in dissipating and distributing turbulent energy at kinetic scales in the ICM.