Context. The formation pathways of sulfur-bearing species in the interstellar medium (ISM) are crucial for our understanding of astrochemical processes in cold molecular clouds and gaining new insights into the sulfur budget in these regions. Aims. We aim to explore the recently detected thioethanal (CH3CHS) formation mechanisms from thioethanol (CH3CH2SH) as a precursor, in addition to secondary sulfur products. Methods. We employed electronic structure methods and density functional theory for both gas-phase and ice-grain surface environments. To mimic interstellar ice-mantles, we used both medium (W6) and large amorphous (W22) water clusters, as implemented in Binding Energy Evaluation Platform (BEEP). Results. We identified a formation mechanism that is effectively barrierless with respect to the reactant asymptote for CH3CHS, which remains kinetically feasible under low-temperature interstellar conditions, in the gas phase. Surface environments modulate activation barriers in a site-specific manner, elucidated through both Langmuir-Hinshelwood and Eley-Rideal initiated surface reaction pathways. Compared to oxygen analogs, sulfur chemistry enables alternate pathways due to weaker S–H bonding, with a competing route forming ethane-1,1-di-thiol (CH3CH(SH)SH) on the ice-grain surface, potentially reducing CH3CHS yields. The first accurate binding energy for thioethanol on water ice is also reported here, confirming its greater volatility in comparison to ethanol. Conclusions. The proposed mechanism offers a tentative hypothesis for the apparent mutual exclusive detections of CH3CH2SH and CH3 CHS in TMC-1, Orion, and Sgr B2(N), which requires further validation through quantitative astrochemical modeling and also to distinguish this chemical differentiation from observational sensitivity limitations. These qualitative findings highlight the multifaceted chemical behavior of sulfur-bearing organics in the ISM and support CH3CH(SH)SH as a promising astrochemical target.
Galaxy formation models predict that galaxies grow inside-out, becoming larger over time. While observations broadly support this paradigm, the nature and timescales of this growth remain poorly constrained. We report the discovery of an extremely faint and young (∼600 Myr) stellar component in the outer regions of the nearby galaxy Messier 74 (M74). Using deep optical imaging from the TST telescope at the Teide Observatory, reaching surface brightness limits of ∼30-31.5 mag arcsec−2 in the g, r, and i bands, we detect stellar emission extending well beyond the previously known disc radius of ∼14 kpc. This newly identified component reaches galactocentric distances of ∼30 kpc, effectively doubling the known size of the stellar disc and matching the extent of the HI disc. The revised size of M74 places it in the upper envelope of the mass–size relations. The young age of the outer stellar population suggests a recent episode of disc growth, potentially occurring on timescales shorter than ∼1 Gyr. We discuss a possible scenario in which a past flyby interaction with UGC 1176 may have triggered this extended star formation. Further studies of galaxies with similarly deep imaging will be key to determining whether such rapid outer disc growth is common or exceptional.
Context.γ2 Velorum is the closest and visually brightest Wolf-Rayet (WR) binary system. Its eccentric orbit modulates the X-rays observed from the wind-wind interaction, and its large separation enables spatial resolution of both components. Aims. We aim to strengthen the constraints on the properties of γ2 Velorum and, in particular, to resolve the discrepancy between the eccentricity determined from the emission lines and that from the absorption lines. Methods. We obtained VLT/GRAVITY observations and combined them with earlier spatially resolved data covering different orbital phases. Results. We determine strong constraints on all orbital parameters and find that e = 0.322, close to the value derived from the emission lines. The X-ray light curve declines as s−3 after periastron, where s is the separation of the two stars, but its modulation is likely affected by absorption and occultation of the X-ray emitting region at other orbital phases. We find that previous discrepancies in the reddening value can be traced to a brighter K-band magnitude than predicted by the WR wind models. We derive E(B − V) = 0.02 ± 0.02 mag. Our more precise mass and radius values, combined with previously determined effective temperatures, provide strong constraints on evolutionary models. The closest match for the O star comes from a rotationally mixed model with initial mass Minit = 28.7 M⊙ and an Minit = 32 M⊙ model for the WR star, with negligible accretion onto the O star during the WR progenitor’s Roche lobe overflow phase. However, the temperature of the O star is higher and the mass of the WR star is smaller than predicted by the evolutionary tracks at the current epoch, consistent with the well-known “mass-discrepancy problem” in massive stars. Conclusions.γ2 Velorum’s strongly constrained parameters make it ideal for testing structure, evolution, and stellar wind models.
Context. Diffuse γ-ray emission from cosmic-ray (CR) protons scattering off the gas in the intracluster and intergalactic medium remains out of reach for current observations. Detecting this emission would provide constraints on the nonthermal pressure support by CR protons in these environments. Aims. We provide estimates for diffuse γ-ray emission in the Fermi-LAT band from galaxy clusters and the cosmic web in the local Universe. Methods. In this work, we show results from the first cosmological magnetohydrodynamic simulation with an on-the-fly spectral CR model. We modeled CR injection at shocks, accounted for adiabatic energy changes and advection of CR protons, and obtained their γ-ray emissivity directly from the simulated CR energy density and spectra. To do this, we used constrained initial conditions that evolved in a field closely resembling that of the local Universe, allowing a direct comparison to Fermi-LAT data on massive clusters. Results. We find CR proton acceleration at all structure formation and accretion shocks in galaxy clusters and cosmic web filaments. These protons provide the basis for diffuse γ-ray emission in these regimes. The absolute value of the diffuse γ-ray emission in our simulation lies a few orders of magnitude below the current upper limits found by Fermi-LAT. Under the assumption of our model, a sensitivity of Fγ < 10−11γ s−1 cm−2 would be required for a detection of diffuse emission in Coma. This provides a lower limit for diffuse emission from CR protons accelerated at structure formation shocks.
Context. Solar active regions are the source of virtually all significant space weather events. It is therefore important to characterize the relationship between their observable properties and flare production. Aims. The flare productivity of solar active regions is analyzed across solar cycles 23–25 as a function of magnetic complexity, sunspot area, and solar-cycle phase. Additionally, the power-law index of the peak flux frequency distribution is estimated. Methods. The GOES soft X-ray event reports matched with daily Solar Region Summaries were used to create a robust active region catalog. This catalog was supplemented with the 50-year HEK flare catalog and the newly released STIX flare catalog from Solar Orbiter to estimate the power-law index. Results. Magnetically complex active regions (βγ, βδ, and βγδ) produce the majority of M- and X-class flares while comprising only ∼13% of all daily active-region observations, showing that larger flares disproportionately occur in larger area sunspots. The peak flux frequency distribution of all three catalogs can be represented with a consistent power-law index of α = 2.02 ± 0.01. However, a class-by-class analysis of the C/X and M/X flare ratios reveals that the distribution steepens significantly toward higher energies. We fit this steepening as a lognormal tail and extrapolated two decades beyond the X-class threshold, which yielded a recurrence time of 370−159+292 yr for an X100-class (“Carrington-type”) superflare, compared to only ∼26 yr from a naive single power-law extrapolation. Conclusions. While α ≈ 2 provides a useful global description of the flare frequency distribution, the steepening area-productivity relation and the divergence between the derived C/X and M/X slopes both point to a deficit of the most energetic flares relative to a single power-law extrapolation. This implies that extreme events such as Carrington-type flares are considerably rarer than a fixed power law would predict. Our extrapolated recurrence time is in much closer agreement with independent literature estimates.
Exoplanet reflection spectra contain a wealth of information, which we are now beginning to access. At a high spectral resolution, the rotation of both the star and the planet affects the shape of the reflected spectral lines. This effect must be accounted for in high-resolution analyses and could be used to measure the orbital alignment of systems. In this work, we derive the rotational broadening kernels for arbitrarily aligned systems, both for the stellar spectrum viewed by the planet and for the reflected component of the planet's spectrum. We then determine the relation between the parameters of the kernels and the standard orbital parameters of an exoplanet system. Finally, we show examples of these kernels, compare them with previous models, and investigate the limitations imposed by our assumptions. We find that the difference in the rotational broadening of a non-aligned system relative to the broadening expected from a prograde aligned orbit can be of the order of SI 50 įlo . We also highlight how the equations and kernels presented in this work could be modified for other uses, such as thermal emission spectra.
The transport of gas toward galactic centers and its connection to active galactic nucleus (AGN) activity remain key open questions in galaxy evolution. In particular, the relative roles of stellar bars and spiral arms and their possible combined influence on angular momentum redistribution and supermassive black hole fueling are not yet fully understood. We investigate the dependence of AGN activity on bar strength and spiral arm morphology in nearby spiral galaxies, with a particular emphasis on disentangling their individual and joint effects while controlling for galaxy stellar mass and color. We constructed a sample of 843 morphologically undisturbed Sa--Sd galaxies from the Mapping Nearby Galaxies at Apache Point Observatory survey in the redshift range 0.026 łeq z łeq 0.1. Bar strengths, stellar masses, colors, and AGN classes were adopted from the literature, while spiral arm classes (ACs), i.e., flocculent (FL), multi-armed (MA), and grand design (GD) systems, were visually determined for the entire sample using optical imaging together with bulge--disk decomposition residual maps. The AGN fraction increases systematically with bar strength, from 0.10^ +0.02 _ -0.02 in unbarred galaxies to 0.34^ +0.03 _ -0.03 in strongly barred systems. After controlling for stellar mass and color, a statistically significant enhancement remains detectable primarily at intermediate stellar masses (10.5 łesssim łog(M_⋆/M_⊙) łesssim 11.0), whereas no significant dependence is found at higher masses. In contrast, spiral arm morphology alone does not show a robust independent connection with AGN activity once stellar mass and color are controlled, although a weak enhancement is present in intermediate-mass GD and MA systems. When bar strength and spiral AC are considered jointly, the highest AGN fraction is observed in strongly barred GD$+MA galaxies (0.39^ +0.04 _ -0.04 )$, while the lowest AGN fractions are found in unbarred FL systems $(0.09^ +0.03 _ -0.02 )$. Our results suggest that stellar mass and color drive the primary trend in AGN activity in nearby disk galaxies, while stellar bars and spiral arms act as secondary structural drivers. The effect of spiral arm morphology is weaker and becomes most apparent when considered jointly with bars. These findings highlight the importance of simultaneously accounting for stellar mass, color, and the combined large-scale morphological structure of galaxies when investigating the triggering of nuclear activity.
GG Tau A is a young triple system consisting of the close pair, Ab_1--Ab_2, and a third component, Aa, surrounded by a massive circumtriple disk whose large inner cavity is difficult to explain in a purely binary framework. Recent astrometric studies have constrained the inner and wide orbits separately. However, only a joint treatment can provide a self-consistent description of the system and constrain the individual stellar masses. We aim to determine the orbital architecture and individual stellar masses of GG Tau A and assess how the available astrometric and disk-based constraints restrict the range of admissible solutions. We performed a joint fit using , developed specifically for hierarchical stellar systems. All astrometric measurements were placed in a common reference frame, since the historical wide-orbit astrometry is given relative to the unresolved photocenter of the Ab subsystem. The fit included one new wide-orbit astrometric epoch and a prior on the total stellar mass derived from disk kinematics. We then applied, in post-processing, an additional geometrical constraint based on the observed center of the circumtriple disk. Oracle The fit yields orbital solutions compatible with the available astrometric and disk-based constraints and provides estimates of the individual stellar masses. The additional wide-orbit epoch only marginally reduces the range of admissible solutions. By contrast, the disk-center constraint leaves the favored orbital architectures largely unchanged but significantly tightens the stellar-mass partition. This yields posterior masses of 0.521^ +0.069 _ -0.051 , 0.106^ +0.017 _ -0.013 , and 0.79^ +0.10 _ -0.10 M_⊙ for Ab_1, Ab_2, and Aa, respectively. The reported values are posterior medians with 16th--84th percentile intervals. A joint treatment of the two orbital levels is required to recover a physically meaningful architecture and constrain the individual stellar masses. The resulting solutions provide a basis for future dynamical modeling of the circumtriple disk and for testing whether the observed cavity can further constrain the system architecture.
The SPHERE High-contrast Imaging survey for Exoplanets (SHINE) represents one of the largest and most sensitive direct imaging campaigns conducted to date with the VLT, targeting over 400 young, nearby stars with the goal of detecting and characterizing giant exoplanets and brown dwarfs. This extensive dataset offers a unique opportunity to revisit observations using modern, data-driven approaches, potentially uncovering new substellar candidates that may have been overlooked by classical analysis techniques. In this context, our study focuses on reprocessing and re-analysing the so-called F150 sample, a well-defined subset of 150 main-sequence stars within 100 pc observed in the H band with VLT/SPHERE as part of the SHINE survey. We applied , a supervised deep learning model specifically tailored for detecting faint planetary signals in angular differential imaging (ADI) sequences. Designed to model local noise properties by capturing spatio-temporal correlations, produces network-confidence detection maps that push the detection of faint companions closer to the noise floor than classical S/N-based approaches. To translate the model's pixel-wise confidence maps into actionable detections, we introduced a novel thresholding strategy that selects, for each annulus, the confidence threshold maximizing the F_1 score (the harmonic mean of precision and recall) from injection-recovery experiments. This principled approach balances sensitivity and specificity, addressing a key limitation in current deep learning-based methods. NA-SODINN NA-SODINN NA-SODINN recovers all known companions and some of the debris disks in the F150 sample, and it identifies 13 new substellar candidates not reported in previous studies: ten detected in both the H2 and H3 bands, and three in only one band. For the ten sources detected in both bands, we used the H2--H3 colour–magnitude diagram to perform a first assessment of their nature. Based on this analysis, we identified two ambiguous cases and three photometrically promising candidates. However, in light of the currently available multi-epoch SPHERE data, only the candidate around Smethells 20 remains a strong target for follow-up.
We aim to investigate how galaxy interactions affect the incidence and strength of nuclear activity in active galactic nucleus (AGN) host galaxies. We also aim to determine the roles played by projected separation, dual activation, and the mass (luminosity) ratio between interacting companions. We combined AGN hosts from SDSS DR7 with a large catalog of galaxy pairs identified in SDSS and Galaxy Zoo DECaLS. Physical pairs were selected using projected separation (r_p < 100 kpc h -1 $) and radial velocity difference (Δ V < 350 km s$^ -1 ). Nuclear activity was traced using attenuation-corrected O iii luminosity, while control samples matched in redshift, stellar mass, luminosity, concentration index, and local density were constructed for comparison. In addition, we classified interactions into major and minor mergers based on luminosity ratios. We find that AGNs in interacting pairs exhibit enhanced nuclear activity compared to isolated AGN, with a systematic increase in O iii luminosity toward smaller projected separations. This enhancement is strongest for close pairs (r_p < 25 kpc h -1 $). Systems hosting two AGNs show higher O iii luminosities than single-AGN pairs, particularly at small separations. Major mergers display significantly higher mean O iii luminosities than minor mergers. It is only these interactions that show a clear rise in activity toward small $r_p values. The AGN luminosity is positively correlated with the luminosity of the companion galaxy, and only weakly with its color. Our results indicate that interactions enhance AGN activity primarily in regimes of close proximity and when the companion is of a comparable or moderate mass. Minor mergers exhibit a scarce influence on nuclear activity, suggesting that only sufficiently strong tidal perturbations efficiently channel gas to the central engine.
Context . We developed a probabilistic machine learning method with the aim of performing the O (10)-way classification of low- and high-resolution spectra of stellar and extragalactic targets for the upcoming 4MOST survey. In fulfilment of the survey requirements, this method should be able to express uncertainty in the input data as well as uncertainty introduced in its prediction. Methods . Four different methods are explored: (1) convolutional neural networks (CNNs), (2) the Dirichlet distribution, (3) Monte Carlo dropout (MCD), (4) Bayesian neural Networks (BNNs) + variational inference (VI). Training and validation was performed using labelled spectra from the SDSS database and a custom 4MOST mock dataset. All the methods were compared in terms of the same metrics: accuracy, area under the curve (AUC), expected calibration error (ECE), Shannon entropy, negative log-likelihood (NLL), Brier score, training time, and inference time. Aims . A CNN with simple architecture and ∼2 × 10 5 parameters was trained to achieve classification accuracies of 91.5% on SDSS data and 92.8% on 4MOST mock data. The direct Dirichlet prediction and VI models tested provide uncertainties on class membership probabilities, but they confuse classes more often. The MCD on a CNN is found to be the most suitable; it boosts the point-estimate accuracies to 92.6% and 93.9%, while still providing fast training and sufficiently fast inference. Compared to a standard CNN, the method additionally provides well-calibrated uncertainties at marginal extra cost.
Context. Low-ionization nuclear emission-line regions (LINERs) commonly host ionized gas outflows. Their role as high-energy particle accelerators is currently debated, especially following the recent very high-energy γ -ray detection of NGC 4278, which showed extreme radiative efficiencies that challenged standard shock-driven emission models. Aims. We aim to empirically determine the γ -ray radiative efficiency of a local sample of LINERs to test whether their high-energy emission can be powered by their extended ionized outflows or whether compact nuclear jets are required. Methods. We combined spatially resolved optical integral-field kinematics from the Multi-Espectrógrafo en GTC de Alta Resolución para Astronomísa at the Gran Telescopio de Canarias, yielding the kinetic powers of ionized outflows ( Ė OF ), with 17 years of Fermi -Large Area Telescope observations to derive 0.05–500 GeV luminosities or 95% confidence upper limits. We constructed an optical/ γ diagram placing our sample in the context of archetypal starbursts (M82, NGC 253) and radio galaxies (Centaurus A, M87). Results. We present the first empirical upper limits on the γ -ray radiative efficiency of LINER outflows as a population. Our likelihood analysis yields no formal detections ( TS ≥ 16) for the LINERs in our sample. The most physically constraining limit is found for the radio-loud LINER NGC 1052, where the maximum efficiency is restricted to η < 41%. For the rest of the sample, the Fermi -LAT upper limits generally lie well above the kinetic power of the ionized outflows ( η ≫ 100%). While three sources show marginal hints of emission (9 < TS < 16), they remain below the discovery threshold. Conclusions. We conclude that the extended ionized outflows in LINERs are highly inefficient high-energy particle accelerators, analogous to starburst superwinds. These sample-level constraints demonstrate that extreme putative efficiencies cannot be sustained by the ionized outflows alone, favoring a compact nuclear jet origin for the most efficient γ -ray emitting LINERs.
The chemistry of sulfur-bearing complex organic molecules in dense star-forming environments remains uncertain, partly because the dominant sulfur reservoirs in dense gas and ices are poorly identified. Alcohol–thioalcohol pairs provide a direct basis for comparing the abundance behavior of structurally related O- and S-bearing molecules. We present ALMA Band 6 observations of G35.2N and investigate the alcohol–thioalcohol pairs CH 3 OH/CH 3 SH and C 2 H 5 OH/C 2 H 5 SH toward three selected spectral-extraction positions, MM3-pos, MM4-pos, and MM5-pos, in the MM3–MM5 region. Local thermodynamic equilibrium spectral modeling was used to derive molecular column densities and abundance ratios. The CH 3 OH column density was derived from 13 CH 3 OH by adopting 12 C/ 13 C = 50, because the main isotopologue is affected by optical-depth effects. Robust column-density constraints were obtained for CH 3 OH, CH 3 SH, and C 2 H 5 OH at all three positions. C 2 H 5 SH was robustly constrained toward MM3-pos and MM5-pos but remains tentative toward MM4-pos. The adopted column densities vary moderately across the three positions, with ranges of (1.8-2.7) × 10 18 cm −2 for CH 3 OH, (1.7-2.6) × 10 16 cm −2 for CH 3 SH, (5.7-8.5) × 10 16 cm −2 for C 2 H 5 OH, and (2.4-4.6) × 10 15 cm −2 for C 2 H 5 SH. Within the adopted uncertainties, the CH 3 OH/C 2 H 5 OH and CH 3 OH/CH 3 SH ratios are consistent across MM3-pos, MM4-pos, and MM5-pos, with nominal values of 31–32 and 100–110, respectively. Comparison with other chemically rich sources and warm-up chemical models shows that the CH 3 OH/C 2 H 5 OH ratio in G35.2N lies within the range measured in other sources, whereas CH 3 OH/CH 3 SH shows a larger source-to-source variation. The ethyl-level O/S comparison remains less certain because many literature C 2 H 5 SH measurements provide only lower limits. CH 3 OH/CH 3 SH is therefore the best-constrained O/S alcohol–thioalcohol analog ratio in the present data and provides a useful empirical probe of source-dependent sulfur-bearing organic chemistry, while higher-sensitivity C 2 H 5 SH observations are needed to test the C 2 H 5 OH/C 2 H 5 SH ratio.
Context. Changing-look active galactic nuclei (CL-AGNs) challenge the unified model of AGNs and offer key insights into the physics of the accretion processes of super-massive black holes. While systematic spectroscopic comparisons have successfully identified large samples of CL-AGNs, photometric selection based on variability features provides an efficient alternative. Aims. We used the color–magnitude (CM) variability pattern method to continue our identification of the CL transition in AGNs. The resulting CL-AGN sample can help improve understanding of this phenomenon. Methods. The CM variability pattern method utilizes the slope ( k ) of the CM variations to identify strong “bluer-when-brighter” behavior, while the variation amplitudes in optical and mid-infrared (MIR) bands are also considered. The candidates selected from the Type-2 AGNs given in the Sloan Digital Sky Survey catalog were spectroscopically observed by us using the 3.6-m Devasthal Optical Telescope and the 2-m Himalayan Chandra Telescope. Results. We successfully confirm seven turn-on CL-AGNs among 12 candidates in this work. Compared with both the general AGN populations and the spectroscopically identified CL-AGN sample, these CL-AGNs show larger optical and MIR variations and k values. The extreme CM variabilities of these sources (with optical magnitude changes > 0.9) occurred recently. For four sources, flare-like brightening episodes were temporally associated with turn-on transitions within 3–7 years, suggesting that these flares may trace short-timescale accretion enhancement, central brightening, and broad-line region re-illumination. In addition, the estimated Eddington ratios for the confirmed CL-AGNs appear to cluster around a critical value of λ Edd ∼ 0.01. Conclusions. The extreme CM variability serves as a highly efficient criterion for finding CL-AGNs. The properties of the CL-AGNs thus found suggest that they may represent AGNs at a pivotal state, which likely occurs in CL transitions due to enhanced accretion activity, while the cause of the accretion activity, which was determined to have a timescale of several years in this work, remains to be investigated further.
Context.γ 2 Velorum is the closest and visually brightest Wolf-Rayet (WR) binary system. Its eccentric orbit modulates the X-rays observed from the wind-wind interaction, and its large separation enables spatial resolution of both components. Aims. We aim to strengthen the constraints on the properties of γ 2 Velorum and, in particular, to resolve the discrepancy between the eccentricity determined from the emission lines and that from the absorption lines. Methods. We obtained VLT/GRAVITY observations and combined them with earlier spatially resolved data covering different orbital phases. Results. We determine strong constraints on all orbital parameters and find that e = 0.322, close to the value derived from the emission lines. The X-ray light curve declines as s −3 after periastron, where s is the separation of the two stars, but its modulation is likely affected by absorption and occultation of the X-ray emitting region at other orbital phases. We find that previous discrepancies in the reddening value can be traced to a brighter K -band magnitude than predicted by the WR wind models. We derive E ( B − V ) = 0.02 ± 0.02 mag. Our more precise mass and radius values, combined with previously determined effective temperatures, provide strong constraints on evolutionary models. The closest match for the O star comes from a rotationally mixed model with initial mass M init = 28.7 M ⊙ and an M init = 32 M ⊙ model for the WR star, with negligible accretion onto the O star during the WR progenitor’s Roche lobe overflow phase. However, the temperature of the O star is higher and the mass of the WR star is smaller than predicted by the evolutionary tracks at the current epoch, consistent with the well-known “mass-discrepancy problem” in massive stars. Conclusions.γ 2 Velorum’s strongly constrained parameters make it ideal for testing structure, evolution, and stellar wind models.
We present the construction and characterization of a multiwavelength catalog of galaxy groups and clusters by matching optical detections from the Southern Photometric Local Universe Survey (S-PLUS) with extended X-ray emission from the first eROSITA all-sky survey data release (eRASS1). We employed a probabilistic matching framework, based on the modified Hausdorff distance, to associate galaxy systems identified by the PZWav cluster finder and characterized by the AME membership estimator with X-ray surface brightness contours. This method explicitly accounts for the photometric redshift probability distribution of galaxies and allowed us to explore the critical trade-off between catalog completeness and purity. We investigated the change in the matched sample with different optical selection depths, defined by absolute magnitude cuts of M r < -18.5, −19, and −19.5, and −20 sampling redshifts within 0.08 < z < 0.25, and for purity levels of 80%, 90%, and 95%. Fainter optical cuts enhance the recovery of low-mass low-luminosity groups, while brighter cuts favor more massive clusters and increase the effective survey volume at higher redshifts. Stricter purity requirements reduce contamination, but systematically lower completeness, particularly for low-luminosity systems. The derived X-ray luminosity functions agree well with previous determinations, and the log N –log S distributions confirm the high recovery rate of luminous clusters. Comparisons with the redMaPPer cluster catalog validate our approach, showing consistent trends and significant overlap, while our method offers improved completeness at the group scale. This work demonstrates a robust, flexible method for creating reliable multiwavelength cluster catalogs, which is essential for cosmological studies and investigations of galaxy evolution in dense environments.
Context . Long-term H α variability provides a direct probe of the dynamical evolution of Be-star circumstellar disks, but interpreting these changes in terms of physical disk properties remains challenging. Aims . We explore the entropy–complexity ( H–C ) plane as a compact diagnostic to link changes in the H α emission-line morphology to the physical evolution of Be-star disks. Methods . We applied entropy and López–Ruiz–Mancini–Calbet complexity diagnostics to H α line profiles from a grid of viscous decretion disk (VDD) models and from time-resolved observations of the late-type Be star β Psc. We compared their respective evolutionary pathways in the H–C plane. Results . The star exhibits an abrupt excursion and a subsequent secular recovery in the H–C plane, associated with rapid changes in the disk mass and apparent inclination within the adopted framework, before returning to a spectroscopic state similar to that observed prior to the major disk event around 2007. Conclusions . The H–C diagram provides a simple diagnostic that is capable of tracing long-term structural evolution and rapid transitions in Be-star disks using the morphology of the H α line profile alone.
Context. The origin of prompt emission in gamma-ray bursts (GRBs) remains a fundamental open question. The internal shock (IS) model is a leading mechanism proposed to explain the dissipation of kinetic energy from relativistic ejecta into gamma rays. However, the model parameters have yet to be fully optimised to reproduce the diverse morphological properties observed in real GRB light curves (LCs). Aims. Utilising a machine-learning framework, we evaluated the IS model through parameter optimisation, comparing the statistical properties of simulated LCs against those of observed data. Methods. Our dataset consists of three GRB catalogues ( Swift /BAT, Fermi /GBM, and CGRO /BATSE). By adopting a model for the GRB formation rate as a function of redshift, we employed a genetic algorithm to optimise the IS model parameters. The algorithm minimises a total loss function based on six independent metrics, representing both the average properties and the statistical distributions of real LCs. Results. The calibrated IS model successfully reproduces the average post-peak GRB temporal profile, together with the corresponding root-mean-square and third-moment temporal profiles, as well as the average autocorrelation function. Furthermore, it recovers the observed distributions of duration, signal-to-noise ratio, peak count per burst, peak flux, and fluence. We find that a generalised Zipf distribution governs the number of shells emitted per GRB, while rest-frame emission times follow a negative exponential distribution. Conclusions. The optimised formulation of the IS model reproduces a wide range of observed GRB LC properties, despite its simplified treatment of radiation physics. Moreover, it provides two key insights into the central engine’s activity: (i) the emission times suggest a stochastic process where all shells within a given burst have an identical, independent, and constant probability of ejection per unit time; and (ii) the heavy-tailed distribution of the number of shells per GRB mirrors the frequency-magnitude distribution of earthquakes, known as the Gutenberg-Richter law. Finally, this optimised model serves as a predictive tool for the GRB populations expected to be detected by future missions.
Giant planets form in protoplanetary discs, where the coupled dynamical and chemical evolution of gas and solids determines the composition of the material they accrete. We investigate how planet formation and migration in evolving discs shape the primordial elemental makeup of giant planet atmospheres. Our aim is to establish a multi-element framework linking atmospheric compositions to the formation pathways of planets and the time-dependent chemical properties of their natal discs. We coupled one-dimensional models of viscously evolving discs – incorporating radial dust drift and a comprehensive treatment of volatile chemistry – with N -body simulations of planetesimals interacting with a growing and migrating giant planet. Four chemical scenarios (inheritance and reset under low and high ionisation) and three representative grain sizes (0.1, 20, and 100 μm) were explored. The coupled outputs were post-processed to track the accretion of carbon, oxygen, nitrogen, and sulphur, and to derive atmospheric elemental ratios normalised to stellar values (* denotes stellar normalisation). We identified three atmospheric classes corresponding to distinct accretion regimes: gas-dominated (GD), characterised by N/O* > C/O* > C/N* and unconstrained or substellar S/N* (near-stellar C/S*); planetesimal-dominated (PD), showing N/O* < C/O* < C/N*, S/N* ≥ C/N*, and C/S* ≤ C/O*; and drift-enhanced (DE), exhibiting N/O* < C/O* < C/N* and markedly super-stellar volatile-to-refractory ratios. We see that N/O*, C/N*, and S/N* vary systematically with migration extent, although degeneracies arise for planets forming beyond the CO and N 2 snow lines; in addition, C/O* remains largely insensitive. Metallicity alone does not uniquely trace the balance between solid and gas accretion in drift-dominated regimes. Variations in the disc’s chemical state and dust size imprint distinctive volatile-ratio patterns across the atmospheric classes, providing complementary constraints on disc properties. This multi-element framework establishes predictive trends to guide the interpretation of atmospheric spectra from current and forthcoming facilities, such as JWST and Ariel, in the context of giant planet formation.
Understanding how galaxy evolution is affected in forming high-z overdensities is a major open question in modern astrophysics. Here, we present the average properties of the quiescent galaxy population recently identified in the core of the Spiderweb protocluster at z = 2.16. By stacking observations from the Hubble Space Telescope (HST; F160W imaging and G141 grism spectroscopy), the James Webb Space Telescope (JWST; PaBeta narrowband imaging), and the Atacama Large Millimeter/submillimeter Array (ALMA; 1.2 mm dust continuum imaging), we constrained their ensemble star formation history (SFH), residual dust-obscured star formation, and cold gas mass, respectively. The inferred average SFH indicates steady stellar mass growth, with progenitor SFRs consistent with those of massive Halpha emitters (HAEs) in the same structure. This is followed by rapid quenching, on average 500 Myr prior to observation. No significant age differences are found between active galactic nucleus (AGN) hosts and non-AGN systems. We find weak PaBeta emission for 80
