Search Results (362)

We present a comprehensive study of host galaxies of radio sources within the 1.35$R_{200}$ of the Coma cluster by combining deep $144\mathrm{MHz}$ observations from the LOFAR Two-Metre Sky Survey (LoTSS-DR2) with optical spectroscopy and photometry from DESI and SDSS. We identify 79 spectroscopically confirmed cluster members with reliable radio emission and classify them into compact, extended, and tailed subsamples according to their radio morphologies. By combining their radio and optical properties, we find compact radio sources are predominantly associated with massive, quiescent galaxies driven by $\mathrm{AGN}$ activity, while tailed sources are largely hosted by star-forming galaxies, tracing ongoing ram pressure stripping ($\mathrm{RPS}$). Using phase-space analysis and a projected infall time proxy ($d_R$), we find that extended sources are preferentially located in the cluster outskirts ($d_R>1$), while tailed sources are concentrated in the intermediate infall region ($0.4<d_R<1.0$), highlighting the influence of the dense intracluster medium. Full article

In her excellent volume Open Socrates: The Case for a Philosophical Life, Agnes Callard juxtaposes Socrates’s conclusion that the meaningfulness of life is a function of consistent critical inquiry into existence with Leo Tolstoy’s contrary insistence that existential meaning ensues from living life without constant interruptions of self-reflection. These two perspectives functionally identify the tension between whether individuals may linguistically express opinions on truth and meaning or must negotiate in some manner with an inescapable silence regarding how best to comprehend and communicate discrete interpretations of the significance and veracity of lived experience. This present article investigates that tension and how it depends on the poetic and apophatic characteristics of language to both Say and Unsay how meaning and truth may be conceived. Salient positions from Ludwig Wittgenstein and William Franke provide introductory material to set the context for a closer examination of the complementary hermeneutics of the French philosopher Paul Ricoeur and the American poet Wallace Stevens. Both thinkers concur that properly analyzing meaning and truth requires a reliance on the creative imagination with its privileging of poetic language and its dependence on the humility of an incredulous faith in approximating an operative asymptotic approach to existential meaning. Full article

The gravitational wave event GW190521 seems to be the only BH merger event possibly correlated with an electromagnetic counterpart, which appeared about 34 days after the GW event. This work aims to confirm that the electromagnetic bump towards the Active Galactic Nucleus (AGN) J1249+3449 can be explained within the framework of the gravitational microlensing phenomenon. In particular, considering the data of the Zwicky Transient Facility (ZTF), what emerges from a detailed analysis of the observed light curve using three fitting models (Point Source Point Lens, Finite Source Point Lens, Uniform Source Binary Lens) is that the optical bump can be explained as a microlensing event caused by a lens with mass $\sim$0.1 $M_{\odot }$, lying in the host galaxy of the AGN in question. Full article

The study of high-redshift active galactic nuclei (AGN) and their small-scale environment is necessary to investigate the different processes that control and influence the evolution of massive galaxies. In this paper we present a case study of cid_1253 ($z=2.15$) and its companion galaxy using archive CO(3–2) and 340 GHz continuum observations with the Atacama Large Millimeter/submillimeter Array, supplemented by multi-wavelength photometry. Previous studies treated the system as a whole, without separating its components in order to match large-beam infrared observations. Our goal is to study cid_1253 and its companion separately by re-analysing the available archive data of the system. Based on our analysis, the companion galaxy is not only more gas-rich ($M_{{\mathrm{H}}_2}\sim {10}^{11}{\mathrm{M}}_{\odot }$) but also has a higher dust mass, indicative of obscured star formation. Moreover, as cid_1253 is not detected at 340 GHz, it is possible that a large fraction of the unresolved, Herschel-detected infrared emission is associated with the companion, rather than cid_1253. The presented case study highlights the need to be more cautious with blended sources before drawing our conclusions and the necessity of high-resolution observations. Full article

The para-positronium system $\left({}^{1}S_{0}Ps\right)$ is described by means of specially constructed coherent states (CSs) in the Klauder–Perelomov sense. It is analyzed from the physical point of view and from the geometry underlying the relevant symmetry group establishing the dynamics of the processes. In this new theoretical context, the possibility of a gamma-ray laser emission is investigated within a QFT context, showing explicitly that, in addition to the oscillator solution based only on a Bogoliubov approximation for the condensate, there is a second phase or “squeezed” stage by which physical features beyond the classical ones appear. Explicitly, while the generated photons are in the active medium (e.g., Ps-BEC), the evolution is described by a Heisenberg–Weyl coherent state with displacement operators dependent on the interaction time, which is related to the condensate shape. After the interaction time has elapsed, we explicitly demonstrate that the displacement operator of the ${}^{1}S_{0}Ps$ is transformed into a squeezed operator of the photonic fields modulated by the matrix element of the Positronium decay ${\mathcal{M}}_{{}^{1}S_{0}Ps}\to 2\gamma$. We also show that this squeezed operator (belonging to the Metaplectic group) generates a non-classical radiation state spanning only even (s = 1/4) levels in the number of photons. The implications in astrophysical systems of interest, considering gamma-ray coherent emission and the possibility of an ${}^{1}S_{0}Ps-BEC$ in the context of pulsars, blazars, and quasars, are briefly discussed. Full article

Despite several efforts to investigate the accretion disk and torus, near-simultaneous broadband studies of the nuclear regions of radio-quiet AGNs remain lacking. NGC 4151, one of the closest and brightest Seyfert galaxies, provides an excellent laboratory for probing the circum-nuclear regions of AGNs. A detailed, near-simultaneous broadband spectral study of NGC 4151 is carried out during one of its historic minimum activity states, using archival data from the Ultraviolet (UV) to the Infrared (IR) regions. We used the radiative transfer code SKIRT to model the source and to constrain the properties of the torus. We found that the observed broadband spectral energy distribution is best explained by a two-torus geometry with a polar conical shell structure. Full article

In dynamic equilibria, benzylsilicon pyridine-2-olate (BnSi(pyO)₃, L) and benzaldehyde react with addition of the Si(pyO) moieties to the PhHC=O carbonyl group and formation of compounds BnSi(–O–C(H,Ph)–N^(2-pyridone))_x(pyO)_3−x (L’, L’’, and L’’’, for x = 1, 2, 3, respectively). Addition of CuCl to a solution containing L, L’, L’’, and L’’’ results in the formation of BnSi(pyO)₃CuCl (LCuCl), shifting the equilibrium towards L with liberation of benzaldehyde. In THF as a solvent, the reaction of L in the presence of excess CuCl affords the complex LCuClCuCl. Upon dissolving in chloroform, it transforms into LCuCl with precipitation of CuCl. The solid state structure of LCuClCuCl features both the monomeric complex with CuClCuCl pattern and a dimer thereof with CuClCu(Cl)₂CuClCu pattern and a central Cu₂Cl₂ four-membered ring. This dimer of LCuClCuCl is the first crystallographically characterized representative of this Cu(I)-only Cu₄Cl₄ motif. The reaction of LCuCl and silver tosylate (AgOTos) in THF affords LCuOTos with precipitation of AgCl, whereas LAgOTos was obtained from L and AgOTos. In the crystal structure, LAgOTos features tetracoordinate Ag(I) in a distorted tetrahedral AgN₃O coordination sphere and a short Ag···Si trans-annular contact (3.3245(7) Å). ¹⁰⁹Ag NMR spectroscopy indicates a change in the coordination in solution, with δ ¹⁰⁹Ag = +551 and +419 ppm in the solid and in CDCl₃ solution, respectively. In combination, ²⁹Si NMR spectroscopy indicates changes in the Si coordination sphere, with δ ²⁹Si = −74.2 and −66.5 ppm in the solid and in CDCl₃ solution, respectively. Conversion of LAgOTos with tetraethylammonium chloride results in the precipitation of AgCl with release of L. Full article

Perseus A (3C 84), a powerful radio source located at the centre of the giant elliptical galaxy NGC 1275—classified as a Seyfert type II AGN and the dominant member of the X-ray bright Abell 426 cluster–exhibits radio emission variability over a wide range of timescales, from decades to hours. This study investigates intraday variability (IDV) in the 6.5 GHz radio emission of 3C 84 using the RT-32 radio telescope in Zolochiv, Ukraine. A novel low-amplitude azimuthal scanning method enabled quasi-simultaneous measurements of antenna and system temperatures, allowing for separation of intrinsic source variations from propagation effects. During an observation session in August 2021, a burst with a peak intensity of 13.5 Jy above the background was detected, likely corresponding to a Fast Radio Burst (FRB). Additionally, quasi-periodic low-amplitude variations with timescales from 0.3 to 6 h were observed. These fluctuations correlate strongly with local atmospheric changes, such as dew formation on the telescope structure, and, to a lesser extent, with ionospheric acoustic–gravity waves. The findings highlight the importance of accounting for propagation conditions when interpreting short-timescale radio variability in AGNs and suggest the need for multi-station, multi-frequency monitoring campaigns to distinguish between intrinsic and environmental modulation of AGN flux densities. Full article

In this paper, we consider Cover’s and Pombra’s formulation of feedback capacity of additive Gaussian noise (AGN) channels, with jointly Gaussian nonstationary and nonergodic noise. We derive closed-form feedback capacity formulas, using Karush–Kuhn–Tucker (KKT) conditions and convergence properties of difference Riccati equations to limiting algebraic Riccati equations of filtering theory, for unstable and stable autoregressive (AR) noise. Surprisingly, the capacity formulas depend on the parameters of the AR noise, its pole $c\in (-\infty ,\infty )$ and noise variance $K_W\in (0,\infty )$, and the total transmit power $\kappa \in [0,\infty )$, indicating substantial gains for the unstable noise region $\forall c^2\in (1,\infty ),\forall \kappa >{\kappa }_{min}\stackrel{▵}{=}{\displaystyle \frac{K_W\left(1+\sqrt{4c^2-3}\right)}{2{\left(c^2-1\right)}^2}}$ compared to its complement region. In particular, feedback capacity is distinguished by three regimes, as follows. Regime 1, $\forall c^2\in (1,\infty ),\forall \kappa >{\kappa }_{min}$: the optimal channel input includes an innovations part, the capacity increases as $\left|c\right|>1$ increases, while ${\kappa }_{min}$ and the allocated transmit power decrease. Regime 2, $\forall c^2\in (1,\infty ),\forall \kappa \le {\kappa }_{min}$, Regime 3, $\forall c\in [-1,1],\forall \kappa \in [0,\infty )$ (complement of Regime 1): the innovations part of the optimal channel is asymptotically zero and the capacity is fundamentally different compared to Regime 1. The differences of capacity formulas for Regimes 1, 2 and 3 are directly related to their operational meaning: (i) Regime 1 is an ergodic capacity while Regimes 2 and 3 are nonergodic capacities; (ii) Regime 1 is achieved by an asymptotically stationary channel input with a non-zero innovations part, while Regimes 2 and 3 are achieved by an asymptotically zero innovations part. The gains of capacity for Regime 1 are attributed to the high correlation of noise samples compared to stable noise and the use of an informative innovations part by the optimal channel input, which make possible the prediction of future noise samples from past samples, unlike memoryless noise. Our results provide answers to certain open questions regarding the validity of capacity formulas of stable noise that appeared in the literature. Full article

Measuring supermassive black hole (SMBH) masses is fundamental to understanding active galactic nuclei (AGN) and their coevolution with host galaxies. Among existing techniques, H₂O megamaser observations with Very Long Baseline Interferometry (VLBI) provide the most direct and geometric determinations of SMBH masses by tracing molecular gas in sub-parsec Keplerian disks. Over the past two decades, the Megamaser Cosmology Project (MCP) has surveyed thousands of nearby AGNs and obtained high-sensitivity VLBI maps of dozens of maser disks that lead to accurate SMBH masses with uncertainties typically below 10%. In this paper, we present a comprehensive review that summarizes the essential elements required to obtain accurate black hole masses with the H₂O megamaser technique—including the physical conditions for maser excitation, observational requirements, disk modeling, and sources of SMBH mass uncertainty—and we discuss the implications of maser-based measurements for exploring SMBH demographics. In particular, we will show that maser-derived black hole masses, largely free from the systematic biases of stellar or gas-dynamical methods, provide critical anchors at the low-mass end of the SMBH population (M_BH∼10⁷M_⊙), and reveal possible deviations from the canonical M_BH–σ_∗ relation. With forthcoming spectroscopic surveys and advances in millimeter/submillimeter VLBI, the maser technique promises to extend precise dynamical mass measurements to both larger local samples and high-redshift galaxies. Full article

In this work, the plasmonic performance of SERS substrates fabricated by two methods was evaluated: the first method involves simultaneously reducing and depositing silver nanostars (AgNSs) onto copper hydroxide nanowires (Cu(OH)₂-NWs), and the second method involves dripping a pre-synthesized and concentrated solution of AgNSs onto the surface of the Cu(OH)₂-NWs. The distribution of AgNSs was characterized by SEM and compared with those deposited on glass after reaction times from 1 to 21 h. A more homogeneous AgNS distribution was observed on the nanowires. The SERS performance was evaluated using methylene blue (MB) as a probe molecule. The SERS intensity on substrates with Cu(OH)₂-NWs was 10 times better than the substrates with glass. Furthermore, the SERS intensity was tripled by dripping a more concentrated solution of AgNSs. This demonstrates that Cu(OH)₂-NWs significantly improve the homogeneity of SERS substrates by increasing the distribution of the metallic nanostructures. Full article

Radio-loud high-redshift quasars (RHRQs) provide crucial insights into the evolution of relativistic jets and their connection to the growth of supermassive black holes. Beyond the extensively studied population at $z\ge 5$, the cosmic morning epoch ($3\lesssim z\lesssim 5$) marks the peak of active galactic nucleus (AGN) activity and black hole accretion, yet remains relatively unexplored. In this work, we compiled the radio high-redshift quasar catalog (RHzQCat) by cross-matching the SDSS DR16Q catalog with four major radio surveys—FIRST, NVSS, RACS, and GLEAM. Our tier-based cross-matching framework and visual validation ensured reliable source identification across surveys with diverse beam sizes. The catalog included 1629 reliable and 315 candidate RHRQs, with radio luminosities uniformly spanning ${10}^{25.5}$–${10}^{29.3}$ W Hz⁻¹. About 95% of the confirmed sources exhibited compact morphologies, consistent with Doppler-boosted or young AGN populations at high redshifts. Our catalog increases the number of known RHRQs at $z\ge 3$ by an order of magnitude, representing the largest and most homogeneous catalog of radio quasars at cosmic morning, filling the observational gap between the early ($z>6$) and local Universe. It provides a robust reference for future statistical studies of jet evolution, AGN feedback, and cosmic magnetism with next-generation facilities such as the Square Kilometer Array (SKA). Full article

What do images ask of the future, and what promises do we owe them? Reading Agnès Varda’s Mur Murs and Visages Villages with Derrida’s archive and de Certeau’s city-writing in mind, I treat Varda’s walls as contested palimpsests. Film overwrites and counter-inscribes surfaces, yet it keeps undertexts legible. I set aside Michael Cramer’s divide between community murals and externally authored photomurals; rather than framing them as opposed projects, the films share one practice: collective inscription, archival method, shifting temporal sense. In Mur Murs, Varda’s camera lets living people eclipse their monumental doubles and turns trompe-l’œil and hushed voices into layers of the palimpsest that refuse closure. In Visages Villages, the larger-than-life portrait of the last remaining inhabitant of a former mining town and the colossal figures of dockworkers’ wives recenter overlooked lives while keeping their impermanence in view. Across both films, cinema becomes the archivable surface: framing, montage, and projection “write” the wall, preserving disappearance even as each screening adds a new layer. Varda practices a careful ethics of remembering that remains future-facing, aware of institutions, and shaped by reality, yet always keeping the walls of stucco, metal, glass, and rock open to re-reading and re-inscription. Full article

Silver nanoparticles (AgNPs) are extensively utilized in cosmetics and healthcare products, creating an urgent need for sensitive quantification methods. We report the first application of a metal–organic framework for electrochemical AgNPs sensing in cosmetic samples. A glassy carbon electrode was modified with polyethyleneimine-encapsulated MOF-235 (PEI-MOF-235/GCE); the PEI layer enriches AgNPs through Ag–N coordination, whereas the high-surface-area MOF catalyzes their oxidative dissolution. Under optimized conditions (catalyst loading 1.4 µg mm⁻³, pH 4.3 PBS), differential-pulse voltammetry provided a linear range of 10–100 ng L⁻¹ and a detection limit of 3.93 ng L⁻¹ (S/N = 3). The sensor exhibited excellent stability (RSD ≤ 4.7%) and good anti-interference capability toward common aquatic ions. Compared with a standard HPLC method, recoveries in spiked cosmetic samples were 97.9–102.6%. This MOF-based strategy offers a sensitive, selective, and field-deployable platform for routine monitoring of trace AgNPs. Full article

To reduce the pollutant emissions of water ecological POI logistics, the water ecological POI logistics route-planning method based on the improved water network space AGNES clustering model and the symmetrical simulated Huffman spatial searching tree (SHSST) algorithm is innovatively established. The improved AGNES algorithm is established for water ecological POI clustering, and then the logistics distribution center location model based on water ecological POI clustering is constructed. On the basis of an optimal distribution center, combining the symmetrical feature of vehicle moving paths and distances in logistics sub-intervals and logistics intervals, the sub-interval optimal route-searching algorithm based on the symmetrical SHSST is constructed to determine the optimal path for each logistics sub-interval, and then the global logistics route-planning algorithm based on undirected complete graph spatial search is constructed to search for the global optimal logistics route. Experiments prove that the proposed algorithm can accurately cluster water ecological POIs and output the logistics route with the lowest costs and pollutant emissions. Compared to the traditional AGNES and other clustering algorithms, the improved AGNES algorithm has lower time complexity. Compared to the traditional logistics route algorithms, SHSST has lower algorithm complexity, route costs, and pollutant emissions, and strong stability. The minimum and maximum optimization rates for the same route are 10.06% and 17.58%, while the minimum and maximum optimization rates for the optimal route are 11.41% and 14.29%; it could effectively reduce the negative impact of pollutants on the water ecological environment and POIs. Full article