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A path planning heuristic for automated guided vehicles in container terminals
No full textThe use of Automated Guided Vehicles for container transportation within container termi- nals has emerged as a promising approach to enhance their efficiency and competitiveness over the last two decades. This development has created a need to optimize the utilization of these resources, partic- ularly through efficient path planning within their operating environment. In this work, we propose a Integer Linear Programming-based heuristic to address the problem of collision-free path planning for Automated Guided Vehicles in automated container terminals, where multiple transportation missions need to be performed by each vehicle. The method is evaluated and tested through extensive numeri- cal experiments. Conclusions are drawn regarding its efficiency, and directions for future research are suggested
Generative models of 21 cm Epoch of Reionisation lightcones with 3D scattering transforms
No full textThe 21 cm signal from the Epoch of Reionisation (EoR) is observed as a 3D dataset known as a lightcone, consisting of two spatial sky plane axes and a redshift (frequency) axis. Owing to its strongly non-Gaussian nature, fully characterising this signal requires summary statistics that go beyond two-point power spectra statistics. Recent developments in astrophysics, particularly in the context of the Galactic interstellar medium, demonstrate the efficacy of scattering transforms–novel summary statistics–to characterise fields with highly non-Gaussian properties. In particular, these statistics allow us to construct maximum-entropy generative models, even from a single target map, from which we can sample new, almost statistically identical realisations of a given process. Motivated by these advances, we extended the scattering transform formalism from 2D datasets to 3D EoR lightcones. To this end, we introduced a 3D wavelet set from the tensor product of 2D isotropic wavelets in the sky plane domain and 1D wavelets in the redshift domain. To test how well this 3D scattering transform can characterise an EoR lightcone, we constructed a maximum entropy generative model of EoR lightcones, which we quantitatively validated by comparing the new synthesised EoR lightcones with the single target lightcone from which the model is defined. Using independent statistics such as the power spectrum, histograms, and Minkowski functionals, we show that the synthesised lightcones agree very well with the target lightcone, both statistically and visually. The success of these generative models in quickly generating EoR lightcones, which can be extended to a broad range of 3D and heterogeneous 2+1D data, opens up a variety of potential applications, from forward modelling to uncertainty quantification
Cosmic voids and the kinetic analysis
No full textWe study the appearance and specific properties of the structures in the local Universe by means of the Vlasov kinetic technique. We consider the role of the cosmological constant in local structure formation via the theorem on the general function that satisfies the identity of the gravity of the sphere and of the point mass. Then, the Hubble tension is naturally explained as a result of two flows, a local and a global one, with non-coinciding Hubble parameters. The linearized Vlasov-Poisson equation with the cosmological term is shown to lead to van Kampen’s waves, Landau damping, and then to aperiodic structures. Aperiodicity thereby emerges as a intrinsic feature of the filamentary and void structure of the local Universe, and reveals the self-consistent field mechanism of its formation. The damping of the aperiodicity is then predicted and can be observationally traced upon the increase in the scale of the filaments
First ionization potential bias evolution in an emerging active region as observed in SPICE synoptic observations
No full textAims. We investigate the time evolution of relative elemental abundances in the context of the first ionization potential effect focusing on an active region (AR). Our aim is to characterize this evolution in different types of AR structures as well as in different atmospheric layers. We wish to assess how the measured changes relate to different magnetic topologies by computing abundance enhancement in different conditions using the ponderomotive force model.
Methods. Leveraging SPICE (Spectral Imaging of the Coronal Environment) spectroscopic observations of extreme ultraviolet lines from ions formed across a broad temperature range – from the upper chromosphere to the low corona –, we performed relative abundance ratios following differential emission measure analysis. This methodology yields abundance maps from low, intermediate, and high first ionization potential elements.
Results. We obtained the temporal evolution of a number of abundance ratios for different structures on the Sun. We compared these results with the outcomes of the ponderomotive force model. We find good correlation between the model and our results, suggesting an Alfvén-wave driven fractionation of the plasma. Fan loops, loop footpoints and AR boundaries exhibit coronal abundances, while the AR core shows more photospheric-like composition. A slow and steady increase in the Mg/Ne first ionization potential bias values is observed, starting around 1.5 and increasing by about 50% after two days. The S/O evolution coupled with the model provides evidence of resonant waves fractionating the plasma in transition region structures
Dwarf galaxies within the Kilo Degree Survey
No full textContext. Constraining the properties, spatial distribution, and luminosity function of dwarf galaxies in different galactic environments is crucial for understanding the dwarf galaxy formation and evolution. Large surveys such as the Kilo Degree Survey (KiDS) provide useful publicly available datasets that can be used to identify dwarf galaxy candidates in a range of galactic neighborhoods. The resulting catalogs are useful for constraining the abundance of dwarfs in different environments and also provide useful galaxy samples for future follow-up studies. Ultimately this analysis of low-mass galaxies also provides constraints on our cosmological galaxy formation models.
Aims. We generated a dwarf galaxy candidate catalog based on the KiDS images. KiDS data covers a 1004 deg2 area in u′, g′, r′, and i′ filters that is centered on two horizontal stripes at the equator and in the southern hemisphere. In our catalog we provide the locations, photometric properties, and visual classifications of dwarf galaxy candidates within 60 Mpc in all different environments covered by the KiDS. We also use the catalog to analyze the dwarf galaxy numbers and distributions in groups as a function of groups’ virial mass.
Methods. We used Max-Tree Objects (MTO) to identify sources from the KiDS data. We then selected objects based on their detection sizes and surface brightness. We used automated photometric pipeline to run GALFIT on the images in order to measure the structure, brightness, and color of the objects. We then used size, surface brightness, and color cuts to exclude the likely background galaxies and classify the likelihoods of the remaining objects being dwarf galaxies based on their visual appearance. We also probed the completeness limits and detection biases of our detection procedure, by embedding simulated galaxies into the KiDS images.
Results. Our catalog contains galaxies that have Re larger than 3 arcsec and reaches the 50% completeness limit at the r′-band mean effective surface brightness of 26 mag arcsec−2. Near the completeness limit there is a slight selection bias toward detecting more round and centrally peaked objects more effectively than the more elongated and centrally flat. Altogether we identified 4 × 107 objects from the KiDs data. After applying the size, color, and surface brightness cuts, we were left with 6230 objects for which we performed photometry and visual classifications. We ranked those objects into five classes based on their likeliness of being a dwarf. We identified 763 galaxies as clear dwarfs, 793 as likely dwarfs, and 933 as possible dwarfs. The remaining objects are likely not dwarfs. Based on the distances of groups that the dwarfs are likely to be associated with, the dwarfs are expected to lie at distances of between 14 Mpc −60 Mpc. The majority of dwarfs in the sample have magnitudes of between 14 mag < mr <20 mag, effective radii of between 1 arcsec < Re <30 arcsec, and mean effective surface brightnesses of between 21 mag arcsec−2 < μ̄r,e < 25 mag arcsec−2. We compare the measured properties of the galaxies in our catalog with values from the literature and find mostly good agreement between those, when considering the differences in the data qualities. The only exceptions are the effective radii, which are systematically smaller in our catalog, due to the background subtraction method used in the KiDS data reduction. We also identify the most likely associations with groups and cluster for all the dwarfs in our catalog. Additionally we compare the number of dwarfs and their distribution within the groups with similar dwarfs found in the Illustris-TNG simulations. We find no statistically significant tension between the dwarf numbers and distributions between the observations and the simulations.
Conclusions. Our catalog contains locations, colors, structural parameters, and likely group memberships for 2489 dwarf galaxy candidates. All the measurements are publicly available. The catalog can be used to study properties of dwarfs in a range of environments and it provides a good dataset for follow-up studies
and IRTF abundance of A-type main-belt asteroids
No full textContext. The so-called missing-mantle problem is a long-standing issue in planetary science. It states that olivine-rich asteroids should be abundant in the main belt, while this is observationally found not to be the case by dedicated surveys. Conversely, olivine-rich asteroids appear to be more abundant among near-Earth asteroids than those surveys would suggest.
Aims. We aim to provide a revised estimate of the abundance of A-type (olivine-rich) asteroids in the main belt by combining taxonomic classifications from Gaia Data Release 3 reflectance spectra with ground-based near-infrared observations from NASA’s IRTF.
Methods. We performed a principal component analysis on Gaia Data Release 3 visible-light reflectance spectra to identify A-type candidates and confirmed a subset of these using near-infrared spectroscopy from the IRTF. We combined our observations with data from the literature to compute the A-type probability distribution as a function of the principal components of Gaia reflectance spectra. This probability distribution was then used to estimate the abundance of A-type asteroids in the main belt and its sub-populations as a function of heliocentric distance. We also examined the distribution of A-type asteroids among known collisional families.
Results. We found that the abundance of A types in the main belt is (2.00 ± 0.15)%, which is significantly higher than previous estimates for the same region. Our analysis also shows that some collisional families, such as those of Vesta and Flora, have above-average A-type fractions, whereas others, such as Themis and Hygiea, exhibit negligible abundance.
Conclusions. Our results support the idea that olivine-rich material is more widespread than previously thought. In particular, the high A-type abundance in the Flora family is consistent with the hypothesis of a second differentiated parent body in the inner main belt, beyond Vesta. This work provides new observational constraints on the missing-mantle problem and the distribution of differentiated material in the asteroid main belt. In particular, our results deepen the compositional diversity observed in the inner main belt and have important implications for our understanding of early Solar System differentiation processes
Geminids are initially cracked by atmospheric thermal stress
No full textContext. Geminids have the highest bulk density of all major meteor showers and their mechanical strength appears to depend on their mass. They are also the most active annual shower, enabling detailed studies of the dependence of their physical and mechanical properties on mass.
Aims. We calculated the fragmentation cascades of 39 bright Geminid fireballs, as well as faint video meteors, to derive fragmentation pressures and other physical properties characterizing the meteoroids, such as their bulk densities. Our goal is to describe the mechanical properties across a broad range of initial masses and explain the cause of the observed behavior.
Methods. We used a physical fragmentation model with a semiautomatic method based on parallel genetic algorithms to fit the radiometric and regular light curve and dynamics data. We also calculated the thermal stress of model bodies with the type of physical properties and trajectories as the observed Geminids. Then, we compared the outcomes of these simulations to our observations.
Results. We find that the Geminids are probably cracked by thermal stress in the atmosphere first and then eroded by mechanical forces. The most compact Geminids are in the 20–200 g mass range. The largest observed meteoroids have a wide range of grain sizes, from about 20 μm to large, non-fragmenting parts of 1–20 mm in size. The derived bulk densities range from about 1400 to 2800 kg m−3 for smaller meteoroids and approach the assumed grain density of 3000 kg m−3 for larger Geminids
Elemental abundance ratios for the bulge of M31
No full textWe present radial trends of metallicity ([Fe/H]) and abundance ratios ([X/Fe]) for several chemical elements–including C, N, Na, and the so-called α-elements (O, Mg, Si, Ca, and Ti)–in the bulge of M31, out to a projected galactocentric distance of ∼0.6 kpc. We estimated abundances using multiple approaches, including full-spectrum fitting, full-index fitting, and line-strength analysis, in combination with different stellar population models. We first tested these techniques on mock spectra and SDSS stacked spectra of early-type galaxies (ETGs), and then applied them to high-quality long-slit spectroscopy of the M31 bulge obtained with the OSIRIS spectrograph at the Gran Telescopio CANARIAS. We find that O, N, and Na are significantly enhanced relative to Fe across the bulge, with typical abundances ≳0.3 dex. In particular, N and Na show steep central enhancements, reaching ∼0.5 dex. C, Mg, and Si exhibit intermediate enhancements of [X/Fe] ∼ 0.2 dex, with C and Mg decreasing toward the center to ≲0.1 dex; while Ca, and to a lesser extent Ti, closely follow Fe, with [X/Fe] < 0.1 dex within uncertainties. Applying the same analysis to SDSS stacked spectra of ETGs as a function of velocity dispersion revealed that the abundance pattern of the M31 bulge closely resembles that of the most massive galaxies, except for N, which is significantly more enhanced (by ∼0.1 dex) in the bulge. For the bulk of the bulge, chemical evolution models assuming high star-formation efficiency and a short gas infall timescale reproduce the overall trends in [Fe/H] and [X/Fe]. In the central region (≲100 pc), the high metallicity content of the bulge can be explained by either an Initial Mass Function flatter than Salpeter at high mass, or a prolonged star formation. Additional processes, such as differential galactic winds, appear necessary to account for the observed decoupling among α elements and the strong central N enhancement. Our results support a scenario whereby the bulk of the M31 bulge formed during a fast and intense episode of star formation
FAUST
No full textMeasuring the properties of disks around Class 0/I protostars is crucial for understanding protostellar assembly and early planet formation. We present high-resolution (~7.5 au) ALMA continuum observations at 1.3 and 3 mm of 16 disks around Class 0/I protostars across multiple star-forming regions (Taurus, Ophiuchus, and Corona Australis) and a variety of multiplicities. Our observations show a wide range of deconvolved disk sizes (~2–100 au) and the presence of circumbinary disks (CBDs) in all binaries with separations <100 au. The measured properties show similarities to Class II disks, including (a) low spectral index values (αdisks = 2.1−0.3+0.5) that increase with disk radius, (b) 3 mm disk sizes only marginally smaller than at 1.3 mm (<10%), and (c) radial intensity morphologies well described by modified self-similar profiles. However, there are some key differences: (i) the α1.3-3 mm values increase monotonically with radius but exceed two only at the disk edge; (ii) higher brightness temperatures, Tb, comparable to or higher than the predicted midplane temperatures due to irradiation; and (iii) an approximately ten times higher luminosity at a given size compared to the Class II disks. Together, the results confirm significant optical depth in the observed Class 0/I disks, most with Tbol < 200 K, at both 1.3 and 3 mm. Assuming fully optically thick disks at these wavelengths can explain the higher luminosities compared with Class II disks, but the most compact (≲40 au) disks also require higher temperatures, suggesting additional heating from viscous accretion. Taking into account the high optical depths, most disk dust masses are estimated in the range 30–900 M⊕ (or 0.01–0.3 M⊙ in gas), with some disks potentially reaching marginal gravitational instability. Based on the elevated Tb1.3 mm, the median location of the water iceline is ~3 au, but this location can extend to more than 10–20 au for the hottest disks in the sample. The CBDs exhibit lower optical depths at both wavelengths and hence higher spectral index values (τ3 mm ≲ 1, αCBD = 3.0−0.3+0.2), dust masses of ~102 M⊕, and dust emissivity indices of βCBD ~ 1.5 (two Class 0 CBDs) and ~1 (one Class I CBD), suggesting substantial grain growth only in the more evolved CBD. The high optical depths inferred from our analysis provide a compelling explanation for the apparent scarcity of dust substructures in the younger Class 0/I disks at ~1 mm despite the mounting evidence of early planet formation
Kinematic and extinction analysis of a potential spiral arm beyond the Galactic bar
No full textContext. Determining the structure of the Milky Way is essential for understanding its morphology, dynamics, and evolution. However, studying its innermost regions is challenging due to high extinction and crowding. The detection of a double red clump (RC; core-helium-burning stars) feature at very low Galactic latitudes suggests the presence of a spiral arm beyond the Galactic bar, providing new insights into the Galaxy’s structure along this complex line of sight.
Aims. We aim to evaluate the presence of this spiral arm by analysing the proper motion and extinction distributions of the detected RC features.
Methods. We constructed proper motion and extinction difference maps to investigate the kinematic and reddening properties of the RC populations. We also confirmed the kinematic difference we see in observational data with N-body simulations of a Milky Way-like galaxy.
Results. We find that the two RC features are kinematically distinct, with a relative proper motion difference of −0.16 ± 0.02 mas/yr in the component parallel to the Galactic plane. This difference can be explained by Galactic rotation if the two RC features are located at different distances along the line of sight, consistent with our simulation results. The extinction towards the secondary RC is also ~0.05 mag higher than that of the primary RC. Additionally, we estimate that the extinction difference between the RC features corresponds to only ~5% of the total extinction from Earth to the first RC, suggesting little interstellar material between the farthest edge of the Galactic bar and the kinematically distinct structure traced by the secondary RC. As a secondary result, we derived the extinction curve using JKs photometry, obtaining AJ/AKs = 3.34 ± 0.07, consistent with previous studies of the innermost Milky Way. We find no significant variation of the extinction curve across fields or along the line of sight, within the uncertainties. The results are compatible with the secondary clump stars belonging to the spiral arm, although we cannot exclude that the population belongs to the disc