Effective Radius Research Articles

Microphysical characteristics of precipitation within convective overshooting over East China observed by GPM DPR and ERA5

Abstract. We examine the geographical distribution and microphysical three-dimensional structure of convective overshooting over East China by matching the Global Precipitation Measurement Dual-frequency Precipitation Radar (GPM DPR) instrument with the European Centre for Medium-Range Weather Forecasts Fifth-Generation Reanalysis (ERA5). Convective overshooting mainly occurs over Northeast China (NC) and northern Middle and East China (MEC), and its frequency varies from 4×10-4 to 5.4×10-3. Radar reflectivity of convective overshooting over NC accounts for a higher proportion below the freezing level, while MEC and South China (SC) account for a higher proportion above the freezing level, indicating stronger upward motion and more ice crystal particles. The microphysical processes within convective overshooting are unique, leading to various properties of the droplets in precipitation. Droplets of convective overshooting are large but sparse, with an effective droplet radius of nearly 2.5 mm below 10 km, which is about twice that of non-overshooting precipitation. The findings of this study may have important implications for the microphysical evolution associated with convective overshooting and provide more accurate precipitation microphysical parameters as input for model simulations.

Deriving cloud droplet number concentration from surface-based remote sensors with an emphasis on lidar measurements

Abstract. Given the importance of constraining cloud droplet number concentrations (Nd) in low-level clouds, we explore two methods for retrieving Nd from surface-based remote sensing that emphasize the information content in lidar measurements. Because Nd is the zeroth moment of the droplet size distribution (DSD), and all remote sensing approaches respond to DSD moments that are at least 2 orders of magnitude greater than the zeroth moment, deriving Nd from remote sensing measurements has significant uncertainty. At minimum, such algorithms require the extrapolation of information from two other measurements that respond to different moments of the DSD. Lidar, for instance, is sensitive to the second moment (cross-sectional area) of the DSD, while other measures from microwave sensors respond to higher-order moments. We develop methods using a simple lidar forward model that demonstrates that the depth to the maximum in lidar-attenuated backscatter (Rmax⁡) is strongly sensitive to Nd when some measure of the liquid water content vertical profile is given or assumed. Knowledge of Rmax⁡ to within 5 m can constrain Nd to within several tens of percent. However, operational lidar networks provide vertical resolutions of > 15 m, making a direct calculation of Nd from Rmax⁡ very uncertain. Therefore, we develop a Bayesian optimal estimation algorithm that brings additional information to the inversion such as lidar-derived extinction and radar reflectivity near the cloud top. This statistical approach provides reasonable characterizations of Nd and effective radius (re) to within approximately a factor of 2 and 30 %, respectively. By comparing surface-derived cloud properties with MODIS satellite and aircraft data collected during the MARCUS and CAPRICORN II campaigns, we demonstrate the utility of the methodology.

Fabrication and luminous properties of BaAl2O4-LuAG:Ce composite phosphor ceramics for solid-state laser lighting

Based on the “effective ionic radius match effect” and the “charge balance substitution rule of ions”, mixed Ba2+, Al3+, Lu3+, and Ce3+ ions can be effectively regulated to a BaAl2O4-LuAG:Ce biphasic structure. The contribution of BaAl2O4 like as scattering centers can reduce overall reflection losses and enhance the light extraction efficiency of these composite phosphor ceramics (CPCs). In this work, a series of x wt.% BaAl2O4-LuAG:Ce (x = 0, 3, 5, 10, 15) CPCs were fabricated by vacuum sintering using co-precipitated composite powders. Homogenization at the atomic level of mixed Ba3+, Al3+, Lu3+, and Ce3+ ions in multiphase powders provides uniform distribution of BaAl2O4 and LuAG:Ce constituent phases in composite ceramics. The introduction of BaAl2O4 has an additive effect, which also consists in uniform aggregation of pores near their grains during sintering. It allows to adjust the size and amount of microstructural defects by varying the secondary phase content. Under the excitation of 10.8 W 450 nm LDs in a reflection mode, 3 wt% BaAl2O4-based CPCs show the optimum luminous flux of 2244 lm and a luminous efficiency of 208 lm·W−1. The obtained CPCs show a high application potential in solid-state laser lighting.

Size–mass relations for simulated low-mass galaxies: mock imaging versus intrinsic properties

ABSTRACT The observationally inferred size versus stellar–mass relationship (SMR) for low-mass galaxies provides an important test for galaxy formation models. However, the relationship relies on assumptions that relate observed luminosity profiles to underlying stellar mass profiles. Here we use the Feedback in Realistic Environments simulations of low-mass galaxies to explore how the predicted SMR changes depending on whether one uses star-particle counts directly or mock observations. We reproduce the SMR found in The Exploration of Local Volume Satellites survey remarkably well only when we infer stellar masses and sizes using mock observations. However, when we use star particles to directly infer stellar masses and half-mass radii, we find that our galaxies are too large and obey an SMR with too little scatter compared to observations. This discrepancy between the ‘true’ galaxy size and mass and those derived in the mock observation approach is twofold. First, our simulated galaxies have higher and more varied mass-to-light ratios (MLR) at a fixed colour than those commonly adopted, which tends to underestimate their stellar masses compared to their true, simulated values. Second, our galaxies have radially increasing MLR gradients therefore using a single MLR tends to underpredict the mass in the outer regions. Similarly, the true half-mass radius is larger than the half-light radius because the light is more concentrated than the mass. If our simulations are accurate representations of the real Universe, then the relationship between galaxy size and stellar mass is even tighter for low-mass galaxies than is commonly inferred from observed relations.

A novel prediction model of oil-water relative permeability based on fractal theory in porous media

It is significant to accurately evaluate the relative permeability of oil–water two phase for multiphase seepage in porous media in low permeability and tight oil reservoir. However, stress sensitivity is an important characteristic for low permeability and tight oil reservoir. It is an effective way for fractal theory to describe the complexity and heterogeneity of the microstructure of porous media. To describe the relative permeability of oil–water two phase in porous media with complex and irregularity pores, a new relative permeability model oil–water two phases is proposed by the fractal theory and the stress sensitivity is taken into the established model in this paper. Meanwhile, the effects of effective stress, elastic modulus, porosity, maximum and minimum flow radius on oil–water relative permeability are analyzed. The new model is verified by comparing with the laboratory data and the results demonstrate that irreducible water and residual oil saturation have a negative correlation with effective stress. The relative permeability of the oil–water two-phase will shrink to the middle as the rise of effective stress, and the region of co-infiltration will decrease. The deformation quantity of porous media, irreducible water and residual oil saturation will increase as the elastic modulus decreases. The larger the maximum flow radius is, the lower the irreducible water saturation and residual oil saturation is. Both the porosity and the minimum flow radius have slight influences on the relative permeability of oil–water two-phase. The proposed relative permeability model can effectively predict the relative permeability of oil and water and help to describe and reveal the multiphase flow in porous media.

A Review of Fracturing and Enhanced Recovery Integration Working Fluids in Tight Reservoirs

Tight reservoirs, characterized by low porosity, low permeability, and difficulty in fluid flow, rely on horizontal wells and large-scale hydraulic fracturing for development. During fracturing, a significant volume of fracturing fluid is injected into the reservoir at a rate far exceeding its absorption capacity. This not only serves to create fractures but also impacts the recovery efficiency of tight reservoirs. Therefore, achieving the integration of fracturing and enhanced recovery functions within the working fluid (fracturing-enhanced recovery integration) becomes particularly crucial. This study describes the concept and characteristics of fracturing-enhanced recovery integration and analyzes the types and features of working fluids. We also discuss the challenges and prospects faced by these fluids. Working fluids for fracturing-enhanced recovery integration need to consider the synergistic effects of fracturing and recovery; meet the performance requirements during fracturing stages such as fracture creation, proppant suspension, and flowback; and also address the demand for increased recovery. The main mechanisms include (1) enlarging the effective pore radius, (2) super-hydrophobic effects, and (3) anti-swelling properties. Fracturing fluids are pumped into fractures through pipelines, where they undergo complex flow in multi-scale fractures, ultimately seeping through capillary bundles. Flow resistance is influenced by the external environment, and the sources of flow resistance in fractures of different scales vary. Surfactants with polymerization capabilities, biodegradable and environmentally friendly bio-based surfactants, crosslinking agents, and amino acid-based green surfactants with outstanding properties will unleash their application potential, providing crucial support for the effectiveness of fracturing-enhanced recovery integration working fluids. This article provides important references for the green, efficient, and sustainable development of tight oil reservoirs.

PbS Colloidal Quantum Dots: Ligand Exchange in Solution

PbS colloidal quantum dots (CQDs) have the advantages of adjustable band gap, large exciton Bohr radius, controllable size, easy synthesis, and potential multi-exciton effect, making them attractive for photodetectors and solar cells. However, the long ligand chain wrapped on PbS CQDs limits carrier transport, and defect states of as-synthesized CQDs increase non-radiative recombination, negatively affecting photovoltaic performance. Surface properties determine the characteristics of CQDs, so ligand exchange processes are crucial. Because solution phase ligand exchange reduces labor and time requirements, it is more advantageous than solid phase ligand exchange. This review discusses the solution phase ligand exchange process of PbS CQDs, emphasizing the impact of surface ligands on conformation and conductivity.

Dielectric properties of water: a molecular dynamics study on the effects of molecule count and cutoff radius.

Currently, the study of systems confined within various materials, such as graphene and graphene oxide, for diverse applications such as water desalination, metal separation from water, battery cells, and high-efficiency capacitors, is very common. Among these systems, water is a prominent subject of investigation. Understanding the impact of the number of molecules and the optimal cutoff radius is essential in order to determine the parameters. This study investigates the dielectric properties of H O in relation to both the number of molecules and the cutoff radius within the simulation cell. We employ the flexible FBA/ water model, known for its improved accuracy in reproducing water's properties across various thermodynamic states. We range from 60 to 1372 molecules and use cutoff radius from 6 to 1.2 nm, encompassing a wide range of calculations to assess their impact on the simulation results, including critical properties like the dielectric constant, density, and phase change enthalpy. Computational theoretical calculations were performed by solving the equations of motion through molecular dynamics (MD) simulations in the liquid phase. These simulations were conducted using the isothermal-isobaric (NPT) ensemble. The primary software used to solve these equations is GROMACS, and own programs for creating the initial cell and performing the analysis.

Numerical Investigation of the Effect of Deltoid Radius on Tensile Load in T-joints

In this study, T-shaped joints were designed from composites with different deltoid radius. For this purpose, carbon fiber woven fabrics were preferred as reinforcement elements. Then, tensile analyzes were performed on these composite T-joints. The effect of the deltoid radius on the maximum tensile load and damage behavior of the structure was examined. As a result of the analyses, fiber tensile-compression damage images occurring in the structure for each deltoid radius were obtained along with the load-displacement graph. The Hashin damage criterion was preferred for damage onset. Material Property Degradation (MPDG) method was used for damage progression in progressive damage analysis. By increasing the deltoid radius from 6 mm to 12 mm, the maximum contact load increased by approximately 10%, and by increasing it to 18 mm, the maximum contact load increased by approximately 20.11%. Fiber compression damage, spread over a wide area on the lower surface of the flange where it does not come into contact with the web, was determined to be the dominant damage type, and it was determined that this damage decreased with the increase of the deltoid radius. it was observed that as the deltoid radius increases, the T-jointed composite structure exhibits more rigid material behavior.

Effects of Leading Edge Radius on Stall Characteristics of Rotor Airfoil

The effects of leading edge radius on the static and dynamic stall characteristics of rotor airfoils are investigated. Initially, a parametric airfoil (PARFOIL) method is employed to generate four morphed airfoils with different leading edge radii based on a NACA 0012 airfoil. Subsequently, the Reynolds-averaged Navier–Stokes (RANS) method is employed to simulate the aerodynamic characteristics of static airfoils, while the improved delayed detached-eddy simulation (IDDES) method is employed for pitching airfoils. The effectiveness and accuracy of the computational fluid dynamics (CFD) methods are demonstrated through favorable agreement between the numerical and experimental results. Finally, both the static and dynamic aerodynamic characteristics are simulated and analyzed for the airfoils with varying leading edge radii. Comparative analyses indicate that at low Mach numbers, the high adverse pressure gradient near the leading edge is the primary cause of leading edge separation and stall. A larger leading edge radius helps to reduce the suction pressure peak and adverse pressure gradients, thus delaying the leading edge separation and stall of airfoil. At high Mach numbers, the leading edge separation and stall are mainly induced by the shock wave. Variations in leading edge radius have minimal impacts on the high adverse pressure gradient induced by the shock wave, thus making the stall characteristics of airfoils almost unaffected at high Mach numbers.

Microphysical Simulation of the 2022 Hunga Volcano Eruption Using a Sectional Aerosol Model

AbstractApproximately 150 Tg of water vapor and 0.42 Tg of sulfur dioxide were injected directly into the stratosphere by the January 2022 Hunga volcanic eruption, which represents the largest water vapor injection in the satellite era. A comparison of numerical simulations to balloon‐borne and satellite observations of the water‐rich plume suggests that particle coagulation contributed to the Hunga aerosol's effective dry radius increase from 0.2 μm in February to around 0.4 μm in March. Our model suggests that the stratospheric aerosol effective radius is persistently perturbed for years by moderate and large‐magnitude volcanic events, whereas extreme wildfire events show limited impact on the stratospheric background particle size. Our analysis further suggests that both the particle optical efficiency and the aerosols' stratospheric lifetime explain Hunga's unusually large aerosol optical depth per unit of the SO2 injection, as compared with the Pinatubo eruption.

Impact of nanopore confinement on phase behavior and enriched gas minimum miscibility pressure in asphaltenic tight oil reservoirs

Miscible gas injection in tight/shale oil reservoirs presents a complex problem due to various factors, including the presence of a large number of nanopores in the rock structure and asphaltene and heavy components in crude oil. This method performs best when the gas injection pressure exceeds the minimum miscibility pressure (MMP). Accordingly, accurate calculation of the MMP is of special importance. A critical issue that needs to be considered is that the phase behavior of the fluid in confined nanopores is substantially different from that of conventional reservoirs. The confinement effect may significantly affect fluid properties, flow, and transport phenomena characteristics in pore space, e.g., considerably changing the critical properties and enhancing fluid adsorption on the pore wall. In this study, we have investigated the MMP between an asphaltenic crude oil and enriched natural gas using Peng-Robinson (PR) and cubic-plus-association (CPA) equations of state (EoSs) by considering the effect of confinement, adsorption, the shift of critical properties, and the presence of asphaltene. According to the best of our knowledge, this is the first time a model has been developed considering all these factors for use in porous media. We used the vanishing interfacial tension (VIT) method and slim tube test data to calculate the MMP and examined the effects of pore radius, type/composition of injected gas, and asphaltene type on the computed MMP. The results showed that the MMP increased with an increasing radius of up to 100 nm and then remained almost constant. This is while the gas enrichment reduced the MMP. Asphaltene presence changed the trend of IFT reduction and delayed the miscibility achievement so that it was about 61% different from the model without the asphaltene precipitation effect. However, the type of asphaltene had little impact on the MMP, and the controlling factor was the amount of asphaltene in the oil. Moreover, although cubic EoSs are particularly popular for their simplicity and accuracy in predicting the behavior of hydrocarbon fluids, the CPA EoS is more accurate for asphaltenic oils, especially when the operating pressure is within the asphaltene precipitation range.

Influence of the shape of a conducting chamber on the stability of rigid ballooning modes in a mirror trap

MHD stabilization of flute and ballooning modes in an axisymmetric mirror trap is studied under the assumption of strong finite Larmor radius effect that suppresses all perturbations with azimuthal numbers m⩾2 and makes the m = 1 mode ‘rigid’. The rigid mode can be effectively suppressed using perfectly conducting lateral wall without any additional means of stabilization or in combination with end MHD anchors. Numerical calculations were carried out for an anisotropic plasma produced in the course of neutral beam injection into the minimum of the magnetic field at the right angle to the trap axis. The stabilizing effect of the conducting shell made of a straightened cylinder is compared with a proportional chamber, which, on an enlarged scale, repeats the shape of the plasma column. It is confirmed that for convincing wall stabilization of the rigid modes, the plasma beta (β, the ratio of the plasma pressure to the magnetic field pressure) must exceed some critical value βcr2 . When conducting lateral wall is combined with conducting end plates imitating MHD end anchors, there are two critical betas and, respectively, two stability zones β<βcr1 and β>βcr2 that can merge, making the entire range 0<β<1 of betas allowable for stable plasma confinement. The dependence of the critical betas on the plasma anisotropy, mirror ratio, width of the vacuum gap between the plasma column and the lateral wall, radial pressure profile and the axial magnetic field profile is examined.

Final results of the search for new Milky Way satellites in the Hyper Suprime-Cam Subaru Strategic Program survey: Discovery of two more candidates

Abstract We present the final results of our search for new Milky Way (MW) satellites using the data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (SSP) survey over ∼1140 deg2. In addition to three candidates that we have already reported, we have identified two new MW satellite candidates in the constellations of Sextans, at a heliocentric distance of D⊙ ≃ 126 kpc, and Virgo, at D⊙ ≃ 151 kpc, named Sextans II and Virgo III, respectively. Their luminosities (Sext II: MV ≃ −3.9 mag; Vir III: MV ≃ −2.7 mag) and half-light radii (Sext II: rh ≃ 154 pc; Vir III: rh ≃ 44 pc) place them in the region of size–luminosity space of ultra-faint dwarf galaxies (UFDs). Including four previously known satellites, there are a total of nine satellites in the HSC-SSP footprint. This discovery rate of UFDs is much higher than that predicted from the recent models for the expected population of MW satellites in the framework of cold dark matter models, thereby suggesting that we encounter a too many satellites problem. Possible solutions to settle this tension are also discussed.

Deriving physical parameters of unresolved star clusters. VIII. Limits of aperture photometry for star cluster studies

Recently, it has been noticed that the discrepancies in the integrated colour indices (CIs) between star clusters and models are mostly due to the projection of bright stars in the apertures. In order to reduce this problem, the method of adaptive aperture photometry has been proposed. This method has been applied to star clusters from the M\,31 Panchromatic $Hubble$ Andromeda Treasury (PHAT) survey, and studies show that the adaptive aperture photometry performs better than the conventional approach. The aim of this study is to determine the best achievable limits on the accuracy and applicability of the aperture photometry method for studying star clusters in the local Universe. We computed a large network of artificial 3D star clusters spanning the parameter space of the M\,31 clusters. We then simulated images of these clusters by projecting each onto a 2D plane from 100 directions. Star cluster images were generated in six passbands to match the PHAT survey. To investigate the limiting accuracy of aperture photometry and the limits of its applicability to star cluster studies, we measured the simulated images and performed parameter determination tests. We demonstrate that star clusters with and without post-main-sequence stars have significant photometric differences. We show that in order to obtain reliable physical parameters of star clusters, the CIs must be measured using an aperture with a radius larger than the cluster’s half-light radius. Furthermore, we demonstrate that the parameter determination of young clusters (sim 10\,Myr) is problematic regardless of the aperture size used. Therefore, it is advisable to determine the parameters of these clusters using colour-magnitude diagram fitting methods, when possible. We also show that the randomness of the viewing angle can lead to a CI uncertainty of up to 0.1\,mag, depending on cluster parameters and aperture size.

CCD UBV(RI)KC photometry and dynamics of the open cluster NGC 1513

ABSTRACT We derive astrophysical parameters of the open cluster NGC 1513 by means of colour indices built with new CCD UBV(RI)KC photometry. Based on early-type members, the mean foreground reddening and total to selective extinction ratio are E(B − V) = 0.79 ± 0.09 mag and RV = 2.85 ± 0.05. Through the differential grid method, we derive the metal abundance [Fe/H] = −0.06 dex (Z = +0.013), which is consistent with the value [Fe/H] = −0.088 of the bright giant member – LAMOST 695710060. Z = +0.013 isochrone fit to the V × (B − V) colour–magnitude diagram leads to a turn-off age of 224 ± 27 Myr (thus an intermediate-age cluster), and a distance modulus of (V0 − MV) = 10.90 ± 0.15 mag, thus implying a distance from the Sun d = 1514 ± 105 pc. Within the uncertainties, our photometric distance is consistent with the value d = 1435 ± 14 pc from the Gaia DR3 parallax. We find signs of small mass segregation through a minimum spanning tree analysis for the 190 most massive stars, together with the rather steep mass function (χ = +2.39) slope. The high core to half-light radius ratio Rcore/Rh = 0.82, together with the compact half-light to tidal radius ratio Rh/Rt = 0.22, suggest that it is probably related to cluster-formation effects, due to little dynamical evolution, instead of driving its dynamical evolution by internal relaxation. Indeed, NGC 1513 is located in the second quadrant (ℓ = 152${_{.}^{\circ}}$59 and Galactocentric distance RGC = 9.57 kpc), which tends to minimize tidal effects by external processes and tidal disruption. Therefore, internal mass segregation effects in NGC 1513 seem to be more efficient than cluster evaporation processes. We find that NGC 1513 migrated about 0.50 kpc from its birth place.

Thermal spalling failure mechanism of heterogeneous granite under moving heat source

The conventional mechanical methods employed for rock breaking encounter substantial challenges in deep, hard formation drilling, characterized by low penetration rates and exorbitant drilling costs. Consequently, there exists an urgent necessity to explore novel drilling methods and technologies. Thermal spallation drilling, as a non-contact rock breaking technique, offers high efficiency in rock fragmentation and substantially reduces drilling costs. However, the mechanism underlying rock fragmentation induced by thermal spallation remains unclear. Therefore, this study establishes a thermo-mechanical coupling model based on heterogeneous granite subjected to a high-temperature moving heat source. The model comprehensively considers the geometric shape, contact, and strength heterogeneity of rock minerals, and analyzes the effects of heating source speed, radius, mineral composition, heterogeneity index, and grain size on the thermal spallation mechanism of rock. The research findings indicate that lower heating source speeds and larger radii result in higher surface temperatures and greater damage volumes, whereas increasing speed and reducing radius enhance fragmentation efficiency, with speed exerting a more significant influence. Thermal spallation primarily results in tensile damage to rocks, with the surface damage and depth of damage being respectively influenced by the heating source speed and radius. Particle size exhibits minimal impact on thermal spallation, while increased quartz content enhances the rock's thermal properties, resulting in significant thermal spallation effects. Additionally, the location of rock damage is closely correlated with thermal parameters. These findings significantly contribute to a better understanding of the thermal spallation fracture mechanism in granite and facilitate the development of technical solutions for thermal spallation drilling methods.

The SAMI Galaxy Survey: impact of star formation and AGN feedback processes on the ionized gas velocity dispersion

ABSTRACT We investigate the influence of star formation and instantaneous active galactic nuclei (AGN) feedback processes on the ionized gas velocity dispersion in a sample of 1285 emission-line galaxies with stellar masses $\log \, (M_*/\mathrm{ M}_{\odot }) \ge 9$ from the integral-field spectroscopy Sydney-AAO Multi-object Integral-field Galaxy Survey. We fit both narrow- and broad-emission-line components using aperture spectra integrated within one effective radius, while ensuring the elimination of velocity differences between the spectra of individual spaxels. Our analysis reveals that 386 (30 per cent) galaxies can be adequately described using a single-emission component while 356 (28 per cent) galaxies require two (broad and narrow) components. Galaxies characterized by high-mass, elevated star formation rate surface density, or type-2 AGN-like emissions tend to feature an additional broad-emission-line component, leading to their classification as double-component galaxies. We explore the correlations between M* and gas velocity dispersions, highlighting that the prominence of the broad component significantly contributes to elevating the gas velocity dispersion. Galaxies displaying AGN-like emission based on optical definitions show enhanced gas velocity dispersions. In star-forming galaxies, both stellar mass and star-formation rate surface density substantially contribute to the velocity dispersion of the narrow component. Increased star-forming activity appears to elevate the velocity dispersion of the narrow component. The broad component exhibits a weaker dependence on stellar mass and is primarily driven by galactic outflows. We suggest that strong star-forming activity leads to the formation of a broad-emission-line component, but the impact on inflating gas velocity dispersion is moderate. On the other hand, AGN-driven outflows appear to be a more important contributor to the elevated velocity dispersion of the ionized gas.

Gas inflows from cloud to core scales in G332.83-0.55: Hierarchical hub-filament structures and tide-regulated gravitational collapse

The massive star-forming region G332.83-0.55 contains at least two levels of hub-filament structures. The hub-filament structures may form through the “gravitational focusing” process. High-resolution LAsMA and ALMA observations can directly trace the gas inflows from cloud to core scales. We investigated the effects of shear and tides from the protocluster on the surrounding local dense gas structures. Our results seem to deny the importance of shear and tides from the protocluster. However, for a gas structure, it bears the tidal interactions from all external material, not only the protocluster. To fully consider the tidal interactions, we derived the tide field according to the surface density distribution. Then, we used the average strength of the external tidal field of a structure to measure the total tidal interactions that are exerted on it. For comparison, we also adopted an original pixel-by-pixel computation to estimate the average tidal strength for each structure. Both methods give comparable results. After considering the total tidal interactions, for the scaling relation between the velocity dispersion σ, the effective radius R, and the column density N of all the structures, the slope of the σ − N * R relation changes from 0.20 ± 0.04 to 0.52 ± 0.03, close to 0.5 of the pure free-fall gravitational collapse, and the correlation also becomes stronger. Thus, the deformation due to the external tides can effectively slow down the pure free-fall gravitational collapse of gas structures. The external tide tries to tear up the structure, but the external pressure on the structure prevents this process. The counterbalance between the external tide and external pressure hinders the free-fall gravitational collapse of the structure, which can also cause the pure free-fall gravitational collapse to be slowed down. These mechanisms can be called “tide-regulated gravitational collapse”.

The ALPINE-ALMA [CII] survey: Dust emission effective radius up to 3 kpc in the early Universe

Aims. Measurements of the size of dust continuum emission are an important tool for constraining the spatial extent of star formation, and hence the buildup of stellar mass. Compact dust emission has generally been observed at cosmic noon (z ∼ 2 − 3). However, at earlier epochs, toward the end of the reionization (z ∼ 4 − 6), only the sizes of a handful of infrared (IR) bright galaxies have been measured. In this work, we derive the dust emission sizes of main-sequence (MS) galaxies at z ∼ 5 from the ALPINE survey. Methods. We measured the dust effective radius, re, FIR, in the uv-plane in Band 7 of ALMA for seven ALPINE galaxies with resolved emission and we compared it with rest-frame ultraviolet (UV) and [CII]158 μm measurements. We studied the re, FIR − LIR scaling relation by considering our dust size measurements and all the data in the literature at z ∼ 4 − 6. Finally, we compared our size measurements with predictions from simulations. Results. The dust emission in the selected ALPINE galaxies is rather extended (re, FIR ∼ 1.5 − 3 kpc), similar to [CII]158 μm but a factor of ∼2 larger than the rest-frame UV emission. Putting together all the measurements at z ∼ 5, spanning two decades in luminosity from LIR ∼ 1011 L⊙ to LIR ∼ 1013 L⊙, the data highlight a steeply increasing trend of the re, FIR − LIR relation at LIR &lt; 1012 L⊙, followed by a downturn and a decreasing trend at brighter luminosities. Finally, simulations that extend up to the stellar masses of the ALPINE galaxies considered in the present work predict a subset of galaxies (∼25% at 1010 M⊙ &lt; M⋆ &lt; 1011 M⊙) with sizes as large as those measured.