Bright Structures Research Articles

High-spectral-resolution Observations of the Optical Filamentary Nebula Surrounding NGC 1275

We present new high-spectral-resolution observations (R = λ/Δλ = 7000) of the filamentary nebula surrounding NGC 1275, the central galaxy of the Perseus cluster. These observations have been obtained with SITELLE, an imaging Fourier transform spectrometer installed on the Canada–France–Hawai Telescope with a field of view of 11′×11′ , encapsulating the entire filamentary structure of ionized gas despite its large size of 80 kpc × 50 kpc. Here, we present renewed fluxes, velocities, and velocity dispersion maps that show in great detail the kinematics of the optical nebula at [S ii] λ6716, [S ii] λ6731, [N ii] λ6584, Hα (6563 Å), and [N ii] λ6548. These maps reveal the existence of a bright flattened disk-shaped structure in the core extending to r ∼10 kpc and dominated by a chaotic velocity field. This structure is located in the wake of X-ray cavities and characterized by a high mean velocity dispersion of 134 km s−1. The disk-shaped structure is surrounded by an extended array of filaments spread out to r ∼ 50 kpc that are 10 times fainter in flux, remarkably quiescent, and have a uniform mean velocity dispersion of 44 km s−1. This stability is puzzling given that the cluster core exhibits several energetic phenomena. Based on these results, we argue that there are two mechanisms that form multiphase gas in clusters of galaxies: a first triggered in the wake of X-ray cavities leading to more turbulent multiphase gas and a second, distinct mechanism, that is gentle and leads to large-scale multiphase gas spreading throughout the core.

Reflectance Confocal Microscopy Combined with Dermoscopy and Histology in the Diagnostic Setting of Pigmented Eccrine Poroma: A Retrospective Study.

Pigmented eccrine poroma (PEP) is a unique variant of a benign adnexal tumor known as eccrine poroma. Distinguishing PEPs from other pigmented lesions can be challenging due to overlapping clinical and dermoscopic features. To provide a comprehensive analysis of the dermoscopic, confocal (RCM), and histological features of PEPs. We undertook a retrospective study of the clinical, dermoscopic, RCM and histopathological features of PEPs that were surgically excised and histopathologically recognized. Data on epidemiological, clinical, dermoscopic, RCM and histopathological features were collected from the databases of the Skin Cancer Unit, IRCCS Policlinico di Sant' Orsola, between January 2021 and May 2023. The study population consisted of 61 patients, including 34 females (55.7%) and 27 males (44.3%). Dermoscopic examination of 61 PEPs revealed the presence of irregular borders (55.7%), milia-like cysts (50.8%), brown pseudo-network (41%), cerebriform pattern (34.4%), comedo-like openings (29.5%), atypical vessels (26.2%), glomerular vessels (18%), fingerprint-like perifollicular structures (8.2%), dots (4.9%) and dotted vessels (4.9%). RCM imaging was collected from 11 cases and showed mostly well-defined tumor nests with small cells in 100% of cases, bright structures in the upper dermis representing melanocytes and melanophages (63.6%), dark round spaces within the tumor nests (54.5%), well-demarcated borders of the nest (45.5%) and dilated and prominent vessels in upper dermis (27.3%). Histopathological pattern analysis revealed PEP sensu stricto (PEPss) as the most frequent (54.1%). The distinctive dermoscopic patterns, along with the confocal features aid in the differentiation from other pigmented lesions.

Exact solutions of Shynaray-IIA equation (S-IIAE) using the improved modified Sardar sub-equation method

In this paper, we present an innovative approach to acquire the exact solutions of the Shynaray-IIA equations (S-IIAE), by using the improved modified Sardar sub-equation method (IMSSEM). The S-IIAE are nonlinear and coupled partial differential equations that arise in various fields of physics and engineering such as optical fibers and ferromagnetic materials. The IMSSEM is applied to S-IIAE; we successfully derived exact solutions that accurately described the wave propagation behavior of the system under consideration. The obtained solutions include rational, trigonometric, and trigonometric hyperbolic function solutions. The obtained solutions are concise and offer a deeper insight into the dynamics and characteristics of the S-IIAE. Moreover, some of the new solutions to S-IIAE are plotted in different dimensions through which bright, anti-kink and bright solitary wave structures are established. The results of the study also indicated that the proposed method is a valuable approach for achieving analytical solutions to a wide range of nonlinear partial differential equations.

Abundant sub-micron grains revealed in newly discovered extreme debris discs

ABSTRACT Extreme debris discs (EDDs) are bright and warm circumstellar dusty structures around main sequence stars. They may represent the outcome of giant collisions occuring in the terrestrial region between large planetesimals or planetary bodies, and thus provide a rare opportunity to peer into the aftermaths of these events. Here, we report on results of a mini-survey we conducted with the aim to increase the number of known EDDs, investigate the presence of solid-state features around 10 μm in eight EDDs, and classify them into the silica or silicate dominated groups. We identify four new EDDs and derive their fundamental properties. For these, and for four other previously known discs, we study the spectral energy distribution around 10 μm by means of VLT/VISIR photometry in three narrow-band filters and conclude that all eight objects likely exhibit solid-state emission features from sub-micron grains. We find that four discs probably belong to the silicate dominated subgroup. Considering the age distribution of the entire EDD sample, we find that their incidence begins to decrease only after 300 Myr, suggesting that the earlier common picture that these objects are related to the formation of rocky planets may not be exclusive, and that other processes may be involved for older objects (≳100 Myr). Because most of the older EDD systems have wide, eccentric companions, we suggest that binarity may play a role in triggering late giant collisions.

Interaction and manipulation for non-autonomous bright soliton solution of the coupled derivative nonlinear Schrödinger equations with Riemann–Hilbert method

Some bright wave solutions of the coupled derivative nonlinear Schrödinger(CDNLS) equations are derived with Riemann–Hilbert(RH) method. We observe some novel non-autonomous bright soliton structures by choosing the different nonlinear perturbation function g(t). It is shown that there are some possibilities to manipulate the interactions of non-autonomous wave solution through choosing nonlinear and gain/loss functions. Some dynamic behaviors of interactions between two bright solitons have been asymptotically analyzed, the two parabolic-type bright solitons propagate with the opposite directions after the interaction. And some interactions of the linear-, parabolic- and periodic-type bright two-solitons are elastic. A general approach is presented to manipulate soliton waves, which has the potential application for the optical self-routing, non-Kerr media and Bose–Einstein condensates(BEC).

Improving Coronal Hole Detections and Open Flux Estimates

One systematic limitation of solar coronal hole (CH) detection at extreme ultraviolet (EUV) wavelengths is the obscuration of dark regions of the corona by brighter structures along the line of sight. Another problem arises when using CHs to compute the Sun’s open magnetic flux, where surface measurements of the radial magnetic field, , are situated slightly below the effective height of coronal EUV emission. In this paper, we explore these two limitations utilizing a thermodynamic magnetohydrodynamic (MHD) model of the corona for Carrington rotation (CR) 2101, where we generate CH detections from EUV 193 Å images of the corona forward-modeled from the MHD solution, and where the modeled open field is known. We demonstrate a method to combine EUV images into a full Sun map that helps alleviate CH obscuration called the minimum intensity disk merge (MIDM). We also show the variation in measured open flux and CH area that is due to the effective height differences between EUV and measurements. We then apply the MIDM method to SDO/AIA 193 Å observations from CR 2101, and conduct an analogous analysis. In this case, the MIDM method uses time-varying images, the effects of which are discussed. We show that overall, the MIDM method and an appreciation of the effective height mismatch provide a useful new way to extract a broader view of CHs, especially near the poles. In turn, they enable improved estimates of the open magnetic flux, and help facilitate comparisons between models and observations.

METHODOLOGY FOR EVALUATING THE EFFECTIVENESS OF OPTOELECTRONIC SYSTEMS WHEN OBSERVING REMOTE SMALL-SIZED INCONSPICUOUS OBJECTS

Aspects of the functioning of optical-electronic systems (OES) in the observation of remote, inconspicuous objects are considered. A technique has been developed for determining the effectiveness of the OES with an assessment of the results of observation of remote objects. A feature of the technique is the ability to identify and take into account the most significant factors that affect the result of the functioning of the OES: the characteristics of the brightness structure of the observed objects, the state of the radiation propagation path to the observation point, the circuitry of the optical system, and the parameters of the modes of the photodetector with a given topology. It is shown that the technique makes it possible to implement the optimal choice of algorithms for determining the coordinates and geometric features of inconspicuous objects. The practical application of the methodology makes it possible to more reliably assess the accuracy of coordinate information about remote objects, as well as to determine the degree of influence of various external and internal factors on the performance indicators of the OES, on the one hand, on the other hand, to form the main parameters of the system for given conditions of observation and solving target problems.

Formation and Dynamics in an Observed Preeruptive Filament

The formation of filaments/prominences is still a debated topic. Many different processes have been proposed: levitation, injection of cool plasma, merging filaments, and cooling plasma in hot loops. We take the opportunity to make a multiwavelength analysis of the formation of an active-region filament, combining several UV and EUV observations including the new Ne vii 465 Å filtergrams provided by the Solar Upper Transition Region Imager on board the Space Advanced Technology satellite. The filament is mainly observed at the limb for 3 hr. It is progressively formed through a series of stages, including emergence and cooling of hot loops, reconnection between small filaments, material transfer in a large filament channel, and reconnection between filaments and emerged hot loops. From the observations at 465 Å, we find that the new-formed filaments show bright structures as in 304 Å, while the long-lived stable filaments display dark morphology as in 211 Å. This suggests that the plasma around 0.5 MK would be an essential component of new-formed filaments and the material temperature in filaments would be variable during their evolution. The filament formed by the recombination of two filaments and an emerged hot loop finally erupts. After reconnection, the final filament shows a highly twisted structure of both bright and dark strands, which is surrounded by several weak and dispersive looplike structures. This eruptive filament has a complex multichannel topology and covers a wide range of temperatures.

On the study of bright, dark and optical wave structures for the coupled fractional nonlinear Schrödinger equations in plasma physics

On the study of bright, dark and optical wave structures for the coupled fractional nonlinear Schrödinger equations in plasma physics

A deep learning approach for automated segmentation of magnetic bright points in the solar photosphere

Context. Magnetic bright points (MBPs) are small, bright, and conspicuous magnetic structures observed in the solar photosphere and are widely recognized as tracers of magnetic flux tubes. Previous studies have underscored the significance of MBPs in elucidating the mechanisms of coronal heating. The continuous advancement of solar telescopes and observation techniques has significantly enhanced the resolution of solar images, enabling a more detailed examination of MBP structures. In light of the growing availability of MBP observation images, the implementation of large-scale automated and precise MBP segmentation methods holds tremendous potential to facilitate significant progress in solar physics research. Aims. The objective of this study is to propose a deep learning network called MBP-TransCNN that enables the automatic and precise pixel-level segmentation of MBPs in large quantities, even with limited annotated data. This network is designed to effectively handle MBPs of various shapes and backgrounds, including those with complex features. Methods. First, we normalized our sample of MBP images. We then followed this with elastic deformation and rotation translation to enhance the images and expand the dataset. Next, a dual-branch encoder was used to extract the features of the MBPs, and a Transformer-based global attention mechanism was used to extract global contextual information, while a convolutional neural network (CNN) was used to extract detailed local information. Afterwards, an edge aware module was proposed to extract detailed edge features of MBPs, which were used to optimize the segmentation results. Focal loss was used during the training process to address the problem of the small number of MBP samples. Results. The average values of precision, recall, F1, pixel accuracy, and intersection over union of the MBP-TransCNN are 0.976, 0.827, 0.893, 0.999, and 0.808, respectively. Experimental results show that the proposed MBP-TransCNN deep learning network can quickly and accurately segment the fine structure of MBPs.

Combined neurological and cardiac rehabilitation:a tale of cardiac tumour operation during inpatient rehabilitation care

Purpose: To encourage screening for cardiac tumours in embolic stroke and improve awareness of cardiac papillary fibroelastoma (PEFs), its treatment and prognosis. Materials and methods: We report the case of a 55 year old lady who was referred for neurological rehabilitation with a diagnosis of ischaemic stroke following right sided hemiparesis and dysarthria. Echocardiogram showed non valvular left atrial tumour. Histopathology confirmed the cardiac tumour to be a cardiac papillary fibroelastoma. Her neurological rehabilitation was recommenced afterwards along with her cardiac rehabilitation with improvement in ability to manage basic activities of daily living with adaptations. Results: Transthoracic echocardiogram revealed ejection fraction of 55% and a bright mobile echogenic structure in the left atrium. Transoesophageal echocardiogram showed possible left atrial myxoma 1.3 cm x 0.96 cm. Surgical excision showed a friable and jelly like mass containing blood deposits. Histology showed papillary fibroelastoma of the left atrium. Conclusion: Cardiac causes, including Papillary fibroelastomas should be considered whilst investigating patients for secondary causes of ischaemic strokes even when they have been transferred for their neurological rehabilitation phase of their care.

The haloes and environments of nearby galaxies (HERON) – III. A 45-kpc spiral structure in the GLSB galaxy UGC 4599

ABSTRACT We use a 0.7-m telescope in the framework of the Halos and Environments of Nearby Galaxies (HERON) survey to probe low surface brightness (LSB) structures in nearby galaxies. One of our targets, UGC 4599, is usually classified as an early-type galaxy surrounded by a blue ring making it a potential Hoag’s Object analogue. Prior photometric studies of UGC 4599 were focused on its bright core and the blue ring. However, the HERON survey allows us to study its faint extended regions. With an 8-h integration, we detect an extremely faint outer disc with an extrapolated central surface brightness of μ0, d(r) = 25.5 mag arcsec−2 down to 31 mag arcsec−2 and a scale length of 15 kpc. We identify two distinct spiral arms of pitch angle ∼6○ surrounding the ring. The spiral arms are detected out to ∼45 kpc in radius and the faint disc continues to ∼70 kpc. These features are also seen in the GALEX far- and near-ultraviolet bands, in a deep u-band image from the 4.3-m Lowell Discovery Telescope (which reveals inner spiral structure emerging from the core), and in H i. We compare this galaxy to ordinary spiral and elliptical galaxies, giant low surface brightness (GLSB) galaxies, and Hoag’s Object itself using several standard galaxy scaling relations. We conclude that the pseudo-bulge and disc properties of UGC 4599 significantly differ from those of Hoag’s Object and of normal galaxies, pointing toward a GLSB galaxy nature and filamentary accretion of gas to generate its outer disc.

High-resolution Observations of Plume Footpoints in a Solar Coronal Hole

Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume’s footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg ii k Dopplergrams show strong blueshifted emission (∼50 km s−1) and a high brightness temperature (Mg ii k2 line) at the footpoint of the plume. The long-period PDs (P ≈ 20–25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume’s footpoint is the most likely candidate to produce upflows and associated PDs along the plume.

Isolas of localized structures and Raman–Kerr frequency combs in micro-structured resonators

We theoretically investigate the combined impact of the Kerr and stimulated Raman scattering effect on the formation of localized structures and frequency comb generation. We focus on the regime of traveling wave instability. We first perform a real-order parameter description by deriving a Swift–Hohenberg equation with nonlocal delayed feedback. Second, we characterize the motion of traveling wave periodic solutions by estimating their thresholds as well their speed. By using a numerical continuation method, we construct a bifurcation diagram showing the emergence of traveling wave periodic solutions, as well as bright and dark moving localized structures. Numerical simulations of the generalized Lugiato–Lefever equation confirm evidence of isolas of localized structures. More importantly, we show that the stimulated Raman scattering strongly impacts the dynamics of localized structures by creating isolas consisting of bright and dark localized structures, and by inducing a motion of these structures. Finally, we provide a geometrical interpretation of the formation of isola stacks based on dynamical systems theory.

First Detection of a Linear Structure in the Midplane of the Young HH 211 Protostellar Disk: A Spiral Arm?

Spiral structures have been detected in evolved protostellar disks, driving the disk accretion toward the central protostars to facilitate star formation. However, it is still unclear if these structures can form earlier in young protostellar disks. With the Atacama Large Millimeter/submillimeter Array, we have detected and spatially resolved a very young and nearly edge-on dusty disk with a radius of only ∼20 au in the HH 211 protostellar system at submillimeter wavelength. It is geometrically thick, indicating that the submillimeter-light-emitting dust grains have yet to settle to the midplane for planet formation. Intriguingly, it shows three bright linear structures parallel to the equatorial plane, resembling a three-layer pancake that has not been seen before. The top and bottom ones arise from the warm disk surfaces, unveiling the flared structure of the disk. More importantly, the middle one is in the dense midplane of the disk and can be modeled as a trailing spiral arm excited by disk gravity, as seen in evolved protostellar disks, supporting the presence of spiral structures in the very early phase for disk accretion.

Evaluating the saturation effect of vegetation indices in forests using 3D radiative transfer simulations and satellite observations

Vegetation indices (VIs) have been used extensively for qualitative and quantitative remote sensing monitoring of vegetation vigor and growth dynamics. However, the saturation phenomenon of VIs (i.e., insignificant change at moderate to high vegetation densities) poses a known limitation to their ability to characterize surface vegetation over the dense canopy. Although the mechanisms underlying saturation are relatively straightforward and several VIs have been proposed to mitigate the saturation effect, the assessment of the saturation effect of VIs remains insufficient. Notably, no unified metric has been proposed to quantify the VI saturation phenomenon, limiting VI selection in practical applications. In this study, we proposed two indicators to describe the saturation phenomenon and utilized a well-validated three-dimensional (3D) canopy radiative transfer (RT) model large-scale remote sensing data and image simulation framework (LESS) to simulate the bidirectional reflectance factor (BRF) of six forests scenes and assessed the variations in VIs in relation to leaf area index (LAI) values over different backgrounds, sun-sensor geometries, and spatial distribution types. The saturation characteristics of 36 VIs were evaluated in combination with simulation results and satellite observations from multiple sensors. The ranking of VI saturation from simulated and satellite results revealed a good agreement. Our results indicated that the simple ratio vegetation index (SR) performed best with the highest saturation point and can well characterize the surface vegetation condition until LAI reaches 4. Besides, we found that the saturation effect of VIs was influenced by soil brightness, sun-sensor geometry, and canopy structure. SR, modified simple ratio (MSR) and normalized green red difference index (NGRDI) were the most susceptible to these disturbing factors, although they had higher resistance to saturation. Modified triangular vegetation index 1 (MTVI1), modified non-linear vegetation index (MNLI), triangular greenness index (TGI), and triangular vegetation index (TriVI) performed well overall, combining the ability to resist saturation and disturbance factors. Appropriate application of VIs can help better understand vegetation responses to climate change and accurately assess ecosystem status. Our results contribute to the understanding of the VI saturation effect and provide a combined model and satellite data experimental workflow in appropriate VI selection to accurately characterize vegetation.

A morphological analysis of the substructures in radio relics

ABSTRACT Recent observations of radio relics – diffuse radio emission in galaxy clusters – have revealed that these sources are not smooth but consist of structures in the form of threads and filaments. We investigate the origin of these filamentary structures and the role of projection effects. To this end, we have developed a tool that extracts the filamentary structures from background emission. Moreover, it is capable of studying both two-dimensional and three-dimensional objects. We apply our structure extractor to both observations and cosmological simulations of radio relics. Using Minkowski functionals, we determine the shape of the identified structures. In our 2D analysis, we find that the brightest structures in the observed and simulated maps are filaments. Our analysis of the 3D simulation data shows that radio relics do not consist of sheets but only of filaments and ribbons. Furthermore, we did not find any measurable projection effect that could hide any sheet-like structures in projection. We find that both the magnetic field and the shock front consist of filaments and ribbons that cause filamentary radio emission.

Far-infrared polarization of the supernova remnant Cassiopeia A with SOFIA HAWC +

ABSTRACT We present polarization observations of the young supernova remnant (SNR) Cas A using the High-resolution Airborne Wideband Camera-Plus (HAWC +) instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The polarization map at 154 $\mu$m reveals dust grains with strong polarization fractions (5–30 per cent), supporting previous measurements made over a smaller region of the remnant at 850 $\mu$m. The 154-$\mu$m emission and the polarization signal is coincident with a region of cold dust observed in the southeastern shell and in the unshocked central ejecta. The highly polarized far-IR emission implies the grains are large (>0.14 $\mu$m) and silicate-dominated. The polarization level varies across the SNR, with an inverse correlation between the polarization degree and the intensity and smaller polarization angle dispersion for brighter SNR emission. Stronger polarization is detected between the bright structures. This may result from a higher collision rate between the gas and dust producing a lower grain alignment efficiency where the gas density is higher. We use the dust emission to provide an estimate of the magnetic field strength in Cas A using the Davis–Chandrasekhar–Fermi method. The high polarization level is direct evidence that grains are highly elongated and strongly aligned with the magnetic field of the SNR. The dust mass from the polarized region is 0.14 ± 0.04 M⊙, a lower limit of the amount of dust present within the ejecta of Cas A. This result strengthens the hypothesis that core-collapse SNe are an important contributor to the dust mass in high redshift galaxies.

Analysis of Low Mechanical Properties of 1420 Al-Li Alloy in Tensile Test

The mechanical properties of 1420 Al-Li alloy tensile specimen were tested after T6 heat treatment. The mechanical properties of some specimens were lower than the standard requirements. In this paper, the reasons for the low mechanical properties of tensile specimens were analyzed by means of electron microscope observation, metallographic examination and hardness examination. The results show that after T6 heat treatment, the surface of the sample is rough and the depth of the oxide layer is different, and the notch sensitivity of 1420 alloy is very high. During the mechanical properties testing, the deep oxide layer becomes the stress concentration point and the source zone of tensile fracture, which reduces the overall mechanical properties of the sample. After heat treatment, the surface of the specimen is formed with low hardness white bright band structure, which also reduces the mechanical properties of the specimen. The high content of Zr in the fracture source region of some samples also leads to the unqualified mechanical properties.

Morphological analysis of the polarized synchrotron emission with WMAP and Planck

The bright polarized synchrotron emission, away from the Galactic plane, originates mostly from filamentary structures. We implement a filament finder algorithm which allows the detection of bright elongated structures in polarized intensity maps. We analyse the sky at 23 and 30 GHz as observed respectively by WMAP and Planck. We identify 19 filaments, 13 of which have been previously observed. For each filament, we study the polarization fraction, finding values typically larger than for the areas outside the filaments, excluding the Galactic plane, and a fraction of about 30% is reached in two filaments. We study the polarization spectral indices of the filaments, and find a spectral index consistent with the values found in previous analysis (about -3.1) for more diffuse regions. Decomposing the polarization signals into the E and B families, we find that most of the filaments are detected in PE , but not in PB . We then focus on understanding the statistical properties of the diffuse regions of the synchrotron emission at 23 GHz. Using Minkowski functionals and tensors, we analyse the non-Gaussianity and statistical isotropy of the polarized intensity maps. For a sky coverage corresponding to 80% of the fainter emission, and on scales smaller than 6 degrees (ℓ > 30), the deviations from Gaussianity and isotropy are significantly higher than 3σ. The level of deviation decreases for smaller scales, however, it remains significantly high for the lowest analised scale (∼ 1.5°). When 60% sky coverage is analysed, we find that the deviations never exceed 3σ. Finally, we present a simple data-driven model to generate non-Gaussian and anisotropic simulations of the synchrotron polarized emission. The simulations are fitted in order to match the spectral and statistical properties of the faintest 80% sky coverage of the data maps.