Brightness Distribution Research Articles

A CNN-LSTM model using elliptical constraints for temporally consistent sun position estimation

More accurate sun position estimation could transform the design and operation of solar power systems, weather forecasting services, and outdoor augmented reality systems. Although several image-based approaches to sun position estimation have been proposed, their performance is significantly affected by momentary disruptions in cloud cover because they use only a single image as input. This study proposes a deep learning-based sun position estimation system that leverages spatial, temporal, and geometric features to accurately regress sun positions even when the sun is partially or entirely occluded. In the proposed approach, spatial features are extracted from an input image sequence by applying a separate Resnet-based convolution network to each frame. To ensure that the temporal changes in the brightness distribution across frames are considered, the spatial features are concatenated and passed on to a stack of LSTM layers prior to regressing the final sun position. The proposed network is also trained with elliptical (geometric) constraints to ensure that predicted sun positions are consistent with the natural elliptical path of the sun in the sky. The proposed approach's performance was evaluated on the Sirta and Laval datasets along with a custom dataset, and an R2 Score of 0.98 was achieved, which is at least 0.1 higher than that of previous approaches. The proposed approach is capable of identifying the position of the sun even when occluded and was employed in a novel sky imaging system consisting of only a camera and fisheye lens in place of a complex array of sensors.

Highlight mask‐guided adaptive residual network for single image highlight detection and removal

AbstractSpecular highlights detection and removal is a challenging task. Although various methods exist for removing specular highlights, they often fail to effectively preserve the color and texture details of objects after highlight removal due to the high brightness and nonuniform distribution characteristics of highlights. Furthermore, when processing scenes with complex highlight properties, existing methods frequently encounter performance bottlenecks, which restrict their applicability. Therefore, we introduce a highlight mask‐guided adaptive residual network (HMGARN). HMGARN comprises three main components: detection‐net, adaptive‐removal network (AR‐Net), and reconstruct‐net. Specifically, detection‐net can accurately predict highlight mask from a single RGB image. The predicted highlight mask is then inputted into the AR‐Net, which adaptively guides the model to remove specular highlights and estimate an image without specular highlights. Subsequently, reconstruct‐net is used to progressively refine this result, remove any residual specular highlights, and construct the final high‐quality image without specular highlights. We evaluated our method on the public dataset (SHIQ) and confirmed its superiority through comparative experimental results.

Coriolis darkening in late-type stars

Context. Modeling the surface brightness distribution of stars is of prime importance to interpret the large amount of available interferometric, spectropolarimetric, or photometric observations. Beyond stellar physics, this is also a prerequisite to characterize exoplanets or our Galaxy. Nevertheless, this remains quite challenging for cool stars as it requires one to model the magnetohydrodynamic turbulence that develops in their convective envelope. Aims. In Paper I (Raynaud, R., Rieutord, M., Petitdemange, L., Gastine, T., & Putigny, B. 2018, A&A, 609, A124), the effect of the Coriolis acceleration on the surface heat flux has been studied by means of hydrodynamic simulations. In this paper, we aim to investigate the additional effect of dynamo magnetic fields that can be generated in the thick convective envelopes of cool stars. We focus on an envelope thickness that is representative of either a ∼0.35 M⊙ M dwarf, a young red giant star or a pre-main sequence star. Methods. We performed a parametric study using numerical magnetohydrodynamic simulations of anelastic convection in thick rotating spherical shells. The stratification in density ranges from a few tens to a few hundreds. The setup assumes a constant entropy jump between the inner and outer layers to force convection, with stress-free boundary conditions for the velocity field. The magnetic Prandtl number was systematically varied in order to vary the magnetic field intensity. For each model, we computed the azimuthally and temporally averaged surface distribution of the heat flux, and examined the leading-order effect of the magnetic field on the obtained latitudinal luminosity profile. Results. We identify three different regimes. Close to the onset of convection, while the first unstable modes tend to convey heat more efficiently near the equator, magnetic fields are shown to generally enhance the mean heat flux close to the polar regions (and the tangent cylinder). By progressively increasing the Rayleigh number, the development of a prograde equatorial jet was previously shown to make the equator darker when no magnetic field is taken into account. For moderate Rayleigh numbers, magnetic fields can instead inverse the mean pole-equator brightness contrast (which means going from a darker to a brighter equator when a dynamo sets in) and finally induce a similar regime to that found close to the onset of convection. For more turbulent models with larger Rayleigh numbers, magnetic fields alternatively tend to smooth out the brightness contrast. This general behavior is shown to be related to the quenching of the surface differential rotation by magnetic fields and remains valid regardless of the magnetic morphology. Conclusions. Mean global trends regarding the impact of rotation and magnetic fields on the surface brightness distribution of cool stars are theoretically depicted and need to be tested by future observations. This work opens the door to more detailed theoretical studies including the effect of nonaxisymmetric and time-variable surface features associated with magnetic activity.

The effect of scalar hair on the charged black hole with the images from accretions disk

In this paper, we investigate the optical properties of a charged black hole with scalar hair (CSH) within the context of four-dimensional Einstein–Maxwell–Dilaton gravity. To achieve this, we consider three distinct toy models of thin accretion disks. The presence of dilaton coupling allows us to express both the solutions of CSH and the Reissner–Nordström (RN) black hole in terms of their mass (M) and charge (Q). Our findings reveal differences in the effective potentials Veff\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$V_{eff}$$\\end{document}, photon sphere radii rph\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_{ph}$$\\end{document}, and innermost stable circular orbit risco\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$r_{isco}$$\\end{document} between the CSH and RN black hole cases, which become increasingly pronounced as the charge parameter Q increases. However, no noticeable distinctions are observed concerning the critical impact parameter bph\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$b_{ph}$$\\end{document}. When the ratio of the photon ring band and the lensed ring band exceeds 0.1, it may suggest the presence of a charged black hole with scalar hair. Furthermore, our results underscore the significant influence of the charge parameter Q on the brightness distributions of the direct, lensed ring, and photon ring for three standard emission functions. These findings emphasize the potential for distinguishing between CSH and RN black holes through an analysis of direct intensity and peak brightness in specific accretion disk models.

Characterisation of optical waveguides for photonic integrated circuits

Fast signal processing at the speed of light is the main advantage of photonic integrated circuits. Therefore, these circuits have good prospects for the implementation of mathematical calculations, including matrix to vector multiplication. The purpose of the research was to create and investigate a technique for automatic measurement of brightness distribution along optical waveguides of analogue photonic integrated circuits. Empirical methods (observation, measurement, comparison, experiment) and a complex method (analysis and synthesis) have been used during the research. The proposed technique uses a digital camera that captures images of optical waveguide illuminated by light emitting diodes and image processing software to calculate brightness distribution. This technique determines the best approximation of this distribution, calculates parameters of brightness non-uniformity and losses of optical radiation. Measurements of a set of optical waveguides help to identify the best candidates for photonic integrated circuits. It has been found that optical waveguides with grinded surfaces acting as diffusive scattering have good combination of smooth brightness distribution and small losses of optical radiation. Due to multiple diffuse reflection and scattering within waveguide material, these waveguides are promising candidates for analogue photonic integrated circuits. All other waveguides with non-processed surface, with grooves or grinded with a large grain have sufficient losses of optical radiation. These losses are usually caused by the exit of optical radiation from waveguide surface. The obtained results are necessary for accurate design of circuits that takes into account scattering and losses in optical waveguides. The proposed technique can be applied in automatic technological process of manufacturing a fast and economical photonic matrix to vector multiplication, which does not require expensive electron-beam, optical or laser lithographic equipment

Recovering the gas properties of protoplanetary disks through parametric visibility modeling: MHO 6

The composition and distribution of the gas in a protoplanetary disk plays a key role in shaping the outcome of the planet formation process. Observationally, the recovery of information such as the emission height and brightness temperature from interferometric data is often limited by the imaging processes. To overcome the limitations of image-reconstruction when analyzing gas emission from interferometric observations, we have introduced a parametric model to fit the main observable properties of the gaseous disk component in the visibility plane. This approach is also known as parametric visibility modeling. We applied our parametric visibility modeling to the gas brightness distribution of the molecular line emission from 12CO J=3-2 and 13CO J=3-2 in the disk around MHO\,6, a very-low-mass star in the Taurus star-forming Region. To improve the flux fidelity of our parametric models, we combined models with different pixel resolution before the computation of their visibilities, referred to as ``nesting images.'' When we apply our parametric visibility modeling to MHO\,6, with independent fits to the emission from its CO isopotologues, the models return the same consistent results for the stellar mass, disk geometry, and central velocity. The surface height and brightness temperature distribution are also recovered. When compared to other disks, MHO\,6 surface height is among the most elevated surfaces, consistent with the predictions for disks around very-low-mass stars. This work demonstrates the feasibility of running rapidly iterable parametric visibility models in moderate resolution and sensitivity interferometric observations. More importantly, this methodology opens the analysis of disk's gas morphology to observations where image-based techniques are unable to robustly operate, as in the case of the compact disk around MHO\,6.

The GRAVITY young stellar object survey

Context. Temporal variability in the photometric and spectroscopic properties of protoplanetary disks is common in young stellar objects. However, evidence pointing toward changes in their morphology over short timescales has only been found for a few sources, mainly due to a lack of high-cadence observations at high angular resolution. Understanding this type of variation could be important for our understanding of phenomena related to disk evolution. Aims. We study the morphological variability of the innermost circumstellar environment of HD 98922, focusing on its dust and gas content. Methods. Multi-epoch observations of HD 98922 at milliarcsecond resolution with VLTI/GRAVITY in the K-band at low (R = 20) and high (R = 4000) spectral resolution are combined with VLTI/PIONIER archival data covering a total time span of 11 yr. We interpret the interferometric visibilities and spectral energy distribution with geometrical models and through radiative transfer techniques using the code MCMax. We investigated high-spectral-resolution quantities (visibilities and differential phases) to obtain information on the properties of the HI Brackett-γ (Brγ)-line-emitting region. Results. Comparing observations taken with similar (u,v) plane coverage, we find that the squared visibilities do not vary significantly, whereas we find strong variability in the closure phases, suggesting temporal variations in the asymmetric brightness distribution associated to the disk. Our observations are best fitted by a model of a crescent-like asymmetric dust feature located at ~1 au and accounting for ~70 % of the near-infrared (NIR) emission. The feature has an almost constant magnitude and orbits the central star with a possible sub-Keplerian period of ~12 months, although a 9 month period is another, albeit less probable, solution. The radiative transfer models show that the emission originates from a small amount of carbon-rich (25%) silicates, or quantum-heated particles located in a low-density region. Among different possible scenarios, we favor hydrodynamical instabilities in the inner disk that can create a large vortex. The high spectral resolution differential phases in the Brγ line show that the hot-gas compact component is offset from the star and in some cases is located between the star and the crescent feature. The scale of the emission does not favor magnetospheric accretion as a driving mechanism. The scenario of an asymmetric disk wind or a massive accreting substellar or planetary companion is discussed. Conclusions. With this unique observational data set for HD 98922, we reveal morphological variability in the innermost 2 au of its disk region. This property is possibly common to many other protoplanetary disks, but is not commonly observed due to a lack of high-cadence observation. It is therefore important to pursue this approach with other sources for which an extended dataset with PIONIER, GRAVITY, and possibly MATISSE is available.

Charting circumstellar chemistry of carbon-rich asymptotic giant branch stars

Context. Asymptotic giant branch (AGB) stars are major contributors to the chemical enrichment of the interstellar medium through nucleosynthesis and extensive mass loss. Direct measures of both processes can be obtained by studying their circumstellar envelopes in molecular line emission. Most of our current knowledge of circumstellar chemistry, in particular in a C-rich environment, is based on observations of the carbon star IRC +10216. Aims. We aim to obtain a more generalised understanding of the chemistry in C-rich AGB circumstellar envelopes by studying a sample of three carbon stars, IRAS 15194–5115, IRAS 15082–4808, and IRAS 07454–7112, and to observationally test the archetypal status often attributed to IRC +10216. Methods. We performed spatially resolved, unbiased spectral surveys in ALMA Band 3 (85–116 GHz). We estimated the sizes of the molecular emitting regions using azimuthally averaged radial profiles of the line brightness distributions. We derived abundance estimates, using a population diagram analysis for molecules with multiple detected lines, and using single-line analytical calculations for the others. Results. We identify a total of 132 rotational transitions from 49 molecular species. There are two main morphologies of the brightness distributions: centrally peaked (CS, SiO, SiS, HCN) and shell-like (CN, HNC, C2H, C3H, C4H, C3N, HC5N, c-C3H2). The brightness distributions of HC3N and SiC2 have both a central and a shell component. The qualitative behaviour of the brightness distributions of all detected molecules, in particular their relative locations with respect to the central star, is the same for all three stars, and consistent with those observed towards IRC +10216. Of the shell distributions, the cyanopolyynes peak at slightly smaller radii than the hydrocarbons, and CN and HNC show the most extended emission. The emitting regions for each species are the smallest for IRAS 07454–7112, consistent with this object having the lowest circumstellar density within our sample. We find that, within the uncertainties of the analysis, the three stars present similar abundances for most species, and also compared to IRC +10216. We find, tentatively, that SiO is more abundant in our three stars compared to IRC+10216, and that the hydrocarbons are under-abundant in IRAS 07454–7112 compared to the other stars and IRC +10216. Our estimated 12C/13C ratios match well the literature values for the three sources and our estimated silicon and sulphur isotopic ratios are very similar across the three stars and IRC +10216. Conclusions. The observed circumstellar chemistry appears very similar across our sample and compared to that of IRC +10216, both in terms of the relative location of the emitting regions and molecular abundances. This implies that, to a first approximation, the chemical models tailored to IRC +10216 are, at least, able to reproduce the observed chemistry in C-rich envelopes across roughly an order of magnitude in wind density.

Deprojection and stellar dynamical modelling of boxy/peanut bars in edge-on discs

ABSTRACT We present a new method to infer the 3D luminosity distributions of edge-on barred galaxies with boxy-peanut/X (BP/X) shaped structures from their 2D surface brightness distributions. Our method relies on forward modelling of newly introduced parametric 3D density distributions for the BP/X bar, disc and other components using an existing image fitting software package (imfit). We validate our method using an N-body simulation of a barred disc galaxy with a moderately strong BP/X shape. For fixed orientation angles, the derived 3D BP/X-shaped density distribution is shown to yield a gravitational potential that is accurate to at least 5 per cent and forces that are accurate to at least 15 per cent, with average errors being $\sim 1.5~{{\ \rm per\ cent}}$ for both. When additional quantities of interest, such as the orientation of the bar to the line of sight, its pattern speed, and the stellar mass-to-light ratio are unknown they can be recovered to high accuracy by providing the parametric density distribution to the Schwarzschild modelling code FORSTAND. We also explore the ability of our models to recover the mass of the central supermassive black hole. This method is the first to be able to accurately recover both the orientation of the bar to the line of sight and its pattern speed when the disc is perfectly edge-on.

Designing a LED Luminaire for Street Lighting with the Most Uniform Brightness Distribution

Designing a LED Luminaire for Street Lighting with the Most Uniform Brightness Distribution

Low and high temperature effects on friction and wear performance of Cr-plated cylinder liner

Cr-plated cylinder liners with good wear and corrosion resistance as well as high strength are suitable for application in low-carbon fuel engines. A reciprocating friction and wear tester was used to measure the friction and wear performance of the Mo-sprayed piston ring and Cr-plated cylinder liner at low and high temperatures. For the low temperature conditions from −20 °C to 20 °C, the worn surface of tribo-pair was more prone to spalling. Once the load went up to 66 MPa under low temperatures, cylinder liner scuffing occurred. As the temperature increased from 90 °C to 240 °C, the honing textures of the Cr-plated cylinder liner presented gradually shallow with more abrasive marks along the sliding direction. The tribo-chemical reaction products of zinc dialkyldithiophosphates (ZDDP) with white bright spots distribution provided better protection of the tribo-pair to avoid severe fatigue spalling. The influence of temperature effects on the ZDDP decomposition and surface spalling damage should not be underestimated for Cr-plated cylinder liners.

Effect of Radial Directional Vibration-Assisted Ductile-Mode Grinding of Al2O3 Ceramics

Effect of Radial Directional Vibration-Assisted Ductile-Mode Grinding of Al₂O₃ Ceramics

Observations of magnetic reconnection in the deep solar atmosphere in the Hεline

Context.Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon known as Ellerman bombs (EBs). It is most common to observe EBs in the Hαand Hβspectral lines. High-quality shorter-wavelength Balmer line observations of EBs are rare, but have the potential to provide the most highly resolved view on magnetic reconnection.Aims.We aim to evaluate the Hε3970 Å line as an EB diagnostic by analyzing high-quality observations in different Balmer lines.Methods.Observations of different targets and viewing angles were acquired with the Swedish 1-m Solar Telescope. These observations sample EBs in different environments: active regions, the quiet Sun, and the penumbra and moat of a sunspot. We employed an automated detection method for quiet-Sun EBs based onk-means clustering.Results.Ellerman bombs in the Hεline show similar characteristics as in the longer-wavelength Balmer lines: a higher intensity than in the surroundings, rapid variability, and a flame-like morphology. In a 24 min quiet-Sun time series, we detected 1674 EBs in the Hεline. This is 1.7 times more EBs than in Hβ. The quiet-Sun EBs measured in Hεare very similar to those in Hβ: They have similar lifetimes and a similar area, brightness, and spatial distribution. Most of the EBs detected in Hεare closer to the limb than their Hβcounterparts because the Hεline core EB emission is formed higher in the atmosphere than the HβEB wing emission.Conclusions.We conclude that the Hεline is well suited for studying EBs, and consequently, for measuring the dynamics of magnetic reconnection in the solar atmosphere at the smallest scales. Our findings suggests that the deep atmosphere in the quiet Sun may host more than 750 000 reconnection events with an EB signature at any time. This is significantly more than what was found in earlier Hβobservations.

Looking for a needle in a haystack: Measuring the length of a stellar bar

One of the challenges related to stellar bars is to accurately determine the length of the bar in a disc galaxy. In the literature, a wide variety of methods have been employed to measure the extent of a bar. However, a systematic study on determining the robustness and accuracy of different bar length estimators is still beyond our grasp. Here, we investigate the accuracy and the correlation (if any) between different bar length measurement methods while using an N-body model of a barred galaxy, where the bar evolves self-consistently in the presence of a live dark matter halo. We investigate the temporal evolution of the bar length, using different estimators (involving isophotal analysis of de-projected surface brightness distribution and Fourier decomposition of surface density), and we study their robustness and accuracy. We made further attempts to determine correlations among any two of these bar length estimators used here. In the presence of spirals, the bar length estimators that only consider the amplitudes of different Fourier moments (and do not take into account the phase-angle of m = 2 Fourier moment) systematically overestimate the length of the bar. The strength of dark-gaps (produced by bars) is strongly correlated with the bar length in early rapid growth phase and is only weakly anti-correlated during subsequent quiescent phase of bar evolution. However, the location of dark-gaps is only weakly correlated to the bar length, hence, this information cannot be used as a robust proxy for determining the bar length. In addition, the bar length estimators, obtained using isophotal analysis of de-projected surface brightness distribution, systematically overestimate the bar length. The implications of bar length over(under)estimation in the context of determining fast and slow bars are further discussed in this work.

LOFAR detection of extended emission around a mini halo in the galaxy cluster Abell 1413

Context. The relation between giant radio halos and mini halos in galaxy clusters is not understood. The former are usually associated with merging clusters, while the latter are found in relaxed systems. In recent years, the advent of low-frequency radio observations has challenged this dichotomy by finding intermediate objects with a hybrid radio morphology. Aims. We aim to investigate the presence of diffuse radio emission in the cluster Abell 1413 and determine its dynamical status to explore the relation between mini halos and giant radio halos. Methods. We used LOFAR observations centred at 144 MHz to study the diffuse radio emission. To investigate the dynamical state of the system, we used newly analysed XMM-Newton archival data. Abell 1413 shows features that are typically present in both relaxed (e.g., peaked X-ray surface brightness distribution and some large-scale inhomogeneities) and disturbed (e.g., flatter temperature and metallicity profiles) clusters. Results. This suggests that Abell 1413 is neither disturbed nor fully relaxed, and we argue that it is an intermediate-phase cluster. At 144 MHz, we discover a wider diffuse component surrounding the previously known mini halo at the cluster center. By fitting the radio surface-brightness profile with a double-exponential model, we can disentangle the two components. We find an inner mini halo with an e-folding radius, re, 1 = 28 ± 5 kpc, and an extended component with re, 2 = 290 ± 60 kpc. We also evaluated the point-to-point correlation between the radio and X-ray surface brightness, finding a sublinear relation for the outer emission and a superlinear relation for the mini halo. The mini halo and the diffuse emission extend over different scales and show different features, confirming the double nature of the radio emission and suggesting that the mechanisms responsible for the re-acceleration of the radio-emitting particle might be different.

Proper motion of the radio jets in two blazars at redshift above 3

ABSTRACT There is still a limited number of high-redshift (z > 3) active galactic nuclei (AGNs) whose jet kinematics have been studied with very long baseline interferometry (VLBI). Without a dedicated proper motion survey, regularly conducted astrometric VLBI observations of bright radio-emitting AGN with sensitive arrays can be utilized to follow changes in the jets, by means of high-resolution imaging and brightness distribution modelling. Here, we present a first-time VLBI jet kinematic study of NVSS J080518 + 614423 (z = 3.033) and NVSS J165844 − 073918 (z = 3.742), two flat-spectrum radio quasars that display milliarcsecond-scale jet morphology. Archival astrometric observations carried out mainly with the Very Long Baseline Array, supplemented by recent data taken with the European VLBI Network, allowed us to monitor changes in their radio structure in the 7.6−8.6 GHz frequency band, covering almost two decades. By identifying individual jet components at each epoch, we were able to determine the apparent proper motion for multiple features in both sources. Apparent superluminal motions range $(1-14)\, c$, and are found to be consistent with studies of other high-redshift AGN targets. Using the physical parameters derived from the brightness distribution modelling, we estimate the Doppler-boosting factors (δ ≈ 11.2 and δ ≈ 2.7), the Lorentz factors (Γ ≈ 7.4 and Γ ≈ 36.6), and the jet viewing angles (θ ≈ 4.4° and θ ≈ 8.0°), for NVSS J080518 + 614423 and NVSS J165844 − 073918, respectively. The data revealed a stationary jet component with negligible apparent proper motion in NVSS J165844 − 073918.

Revisiting a Core–Jet Laboratory at High Redshift: Analysis of the Radio Jet in the Quasar PKS 2215+020 at z = 3.572

The prominent radio quasar PKS 2215+020 (J2217+0220) was once labelled as a new laboratory for core–jet physics at redshift z=3.572 because of its exceptionally extended jet structure traceable with very long baseline interferometric (VLBI) observations up to a ∼600 pc projected distance from the compact core and a hint of an arcsec-scale radio and an X-ray jet. While the presence of an X-ray jet could not be confirmed later, this active galactic nucleus is still unique at high redshift with its long VLBI jet. Here, we analyse archival multi-epoch VLBI imaging data at five frequency bands from 1.7 to 15.4 GHz covering a period of more than 25 years from 1995 to 2020. We constrain apparent proper motions of jet components in PKS 2215+020 for the first time. Brightness distribution modeling at 8 GHz reveals a nearly 0.02 mas yr−1 proper motion (moderately superluminal with apparently two times the speed of light), and provides δ=11.5 for the Doppler-boosting factor in the inner relativistic jet that is inclined within 2∘ to the line of sight and has a Γ=6 bulk Lorentz factor. These values qualify PKS 2215+020 as a blazar, with rather typical jet properties in a small sample of only about 20 objects at z>3.5 that have similar measurements to date. According to the 2-GHz VLBI data, the diffuse and extended outer emission feature at ∼60 mas from the core, probably a place where the jet interacts with and decelerated by the ambient galactic medium, is consistent with being stationary, albeit slow motion cannot be excluded based on the presently available data.

Correction of uneven illumination in microscopic image through robust brightness distribution estimation and deviation rectification

For diagnostic purposes, the automatic microscopic scanning system can scan and stitch multiple slide images together to produce a Whole Slide Image. This process provides a clear, high-resolution picture of the slide sample under the high-power objective lens of the microscope, enabling accurate diagnosis and analysis. However, uneven illumination affects every image acquired by a microscope, resulting in the existence of artifacts. In this paper, a novel retrospective approach based on robust brightness distribution estimation and deviation rectification is proposed. Least squares estimation and Cauchy estimation with a smooth regularization term are used to obtain the accurate estimation of background illumination distribution. Then the deviation map is given based on the deviation function of the two directions for illumination correction. This method leverages the statistical properties of image sequences to enhance stability and robustness against biological image artifacts. Through experimental validation, this approach successfully eliminates visible edge artifacts that commonly appear between neighboring tiles and exhibits superior performance when compared to other methods.

Feeding and feedback processes in the Spiderweb proto-intracluster medium

Context. We present a detailed analysis of the thermal, diffuse emission of the proto-intracluster medium (proto-ICM) detected in the halo of the Spiderweb Galaxy at z = 2.16, within a radius of ∼150 kpc. Aims. Our main goal is to derive the thermodynamic profiles of the proto-ICM, establish the potential presence of a cool core and constrain the classical mass deposition rate (MDR) that may feed the nuclear and the star formation (SF) activity, and estimate the available energy budget of the ongoing feedback process. Methods. We combined deep X-ray data from Chandra and millimeter observations of the Sunyaev–Zeldovich (SZ) effect obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Results. Thanks to independent measurements of the pressure profile from the ALMA SZ observation and the electron density profile from the available X-ray data, we derived, for the first time, the temperature profile in the ICM of a z > 2 protocluster. It reveals the presence of a strong cool core (comparable to local ones) that may host a significant mass deposition flow, consistent with the measured local SF values. We also find mild evidence of an asymmetry in the X-ray surface brightness distribution, which may be tentatively associated with a cavity carved into the proto-ICM by the radio jets. In this case, the estimated average feedback power would be in excess of ∼1043 erg s−1. Alternatively, the asymmetry may be due to the young dynamical status of the halo. Conclusions. The cooling time of baryons in the core of the Spiderweb protocluster is estimated to be ∼0.1 Gyr, implying that the baryon cycle in the first stages of protocluster formation is characterized by a high-duty cycle and a very active environment. In the case of the Spiderweb protocluster, we are witnessing the presence of a strongly peaked core that is possibly hosting a cooling flow with a MDR up to 250–1000 M⊙ yr−1, responsible for feeding both the central supermassive black hole (SMBH) and the high star formation rate (SFR) observed in the Spiderweb Galaxy. This phase is expected to be rapidly followed by active galactic nucleus (AGN) feedback events, whose onset may have already left an imprint in the radio and X-ray appearance of the Spiderweb protocluster, eventually driving the ICM into a self-regulated, long-term evolution in less than one Gyr.

Introducing LensCharm

Strong gravitational lensing, a phenomenon rooted in the principles of general relativity, grants us a unique window into the distant cosmos by offering a direct probe into dark matter and providing independent constraints on the Hubble constant. These research objectives call for the utmost precision in the estimation of the lens mass and the source brightness distributions. Recent strides in telescope technology promise to provide an abundance of yet undiscovered strong-lensing systems, presenting observations of unprecedented quality. Realizing the full potential of these advancements hinges on achieving the highest fidelity in both source and lens reconstruction. In this study, we introduce LensCharm, a novel Bayesian approach for strong-lensing signal reconstruction. Unlike more prevalent methods, LensCharm enables the nonparametric reconstruction of both the source and lens concurrently, along with their associated uncertainties. We showcase the distinctive strengths of our approach through comprehensive analyses of both real-world and simulated astronomical data, underscoring its superiority in achieving precise reconstructions. We have made LensCharm publicly accessible, envisioning its empowerment of the next generation of astronomical observation reconstructions and cosmological constraints derived from strong gravitational lensing.