Semi-analytical Model Research Articles

Semi-analytical prediction of energy-based acoustical parameters in proscenium theatres

Previous studies of the authors have shown that there are limitations when the existing acoustic energy models are applied to theatres. In the present study, a new semi-analytical model is developed based on site surveys and scale model measurements, aiming to overcome these limitations and provide a reliable prediction of the most relevant energy-based monaural parameters: clarity C80, definition D50, center time TS, sound strength G, early strength G80 and late strength GL, in the stall of proscenium theatres for a comprehensive evaluation of the acoustic quality. Three full-size halls plus two scale model cases of another hall, which differ in dimension, acoustical condition and style of interior decoration, have been exploited as a sample for data analysis to propose the model, and another two halls not included in the sample are chosen for model validation. The results reveal that the proposed model has significant improvement in prediction accuracy than the existing theory initially developed for concert halls. The good agreement between the predicted values of the six energy-based acoustical parameters (i.e., G80, GL, G, C80, D50 and TS) by the new model and those measured indicates that this model can be used for point-by-point predictions in the stall area of proscenium theatres with reasonable accuracy.

Dust ring and gap formation by gas flow induced by low-mass planets embedded in protoplanetary disks. II. Time-dependent model

The observed dust rings and gaps in protoplanetary disks could be imprints of forming planets. Even low-mass planets in the 1--10 Earth-mass regime, which have not yet carved deep gas gaps, can generate such dust rings and gaps by driving a radially-outward gas flow, as shown in previous work. However, understanding the creation and evolution of these dust structures is challenging due to dust drift and diffusion, requiring an approach beyond previous steady state models. Here we investigate the time evolution of the dust surface density influenced by the planet-induced gas flow based on post-processing three-dimensional hydrodynamical simulations. We find that planets larger than a dimensionless thermal mass of $m=0.05$ corresponding to $0.3$ Earth mass at 1 au or 1.7 Earth masses at 10 au generate dust rings and gaps provided that solids have small Stokes numbers St and that the disk midplane is weakly turbulent ($ diff As dust particles pile up outside the orbit of the planet, the interior gap expands with time when the advective flux dominates over diffusion. Dust gap depths range from a factor of a few to several orders of magnitude, depending on planet mass and the level of midplane particle diffusion. We constructed a semi-analytic model describing the width of the dust ring and gap, and then compared it with the observational data. We find that up to 65<!PCT!> of the observed wide-orbit gaps could be explained as resulting from the presence of a low-mass planet, assuming diff and St However, it is more challenging to explain the observed wide rings, which in our model would require the presence of a population of small particles ($ Further work is needed to explore the role of pebble fragmentation, planet migration, and the effect of multiple planets.

Changing disc compositions via internal photoevaporation

The chemical evolution of protoplanetary discs is a complex process that is not fully understood. Several factors influence the final spatial distribution of atoms and molecules in the disc. One such factor is the inward drift and evaporation of volatile-rich pebbles that can enrich the inner disc with vapour. In particular, the inner disc is first enriched with evaporating water-ice, resulting in a low C/O ratio, before carbon-rich gas from the outer disc – originating from the evaporation of CO, CO2, and CH4 ice – is transported viscously inwards, elevating the C/O ratio again. However, it is unclear how internal photoevaporation – which carries away gas and opens gaps in the disc that can block inward drifting pebbles – affects the chemical composition of the disc. Our goal is to study how and to what extent internal photoevaporation and the subsequent opening of gaps influence the chemical evolution of protoplanetary discs around solar-like stars (M* = 1 M⊙), where we specifically focus on the C/O ratio and the water content. To carry out our simulations, we use a semi-analytical 1D disc model. The code chemcomp includes viscous evolution and heating, pebble growth and drift, pebble evaporation and condensation, as well as a simple chemical partitioning model for the disc. We show that internal photoevaporation plays a major role in the evolution of protoplanetary discs and their chemical composition: As photoevaporation opens a gap, inward drifting pebbles are stopped and can no longer contribute to the volatile content in the gas. In addition, volatile-rich gas from the outer disc, originating from evaporated CO, CO2, or CH4 ice, is carried away by the photoevaporative winds. Consequently, the C/O ratio in the inner disc remains low. In contrast, gaps opened by giant planets still allow the gas to pass, resulting in an elevated C/O ratio in the inner disc, similar to the evolution of viscous discs without internal photoevaporation. This opens the possibility to distinguish observationally between these two scenarios when measuring the C/O ratio, implying that we can infer the root cause of deep gap structures when observing protoplanetary discs. In the case of a clear separation of the disc by photoevaporation, we additionally find an elevated water content in the inner disc, because the water vapour and ice undergo a cycle of evaporation and recondensation, preventing the inward accretion of water onto the star, in contrast to the situation for hydrogen and helium. We conclude that it is very difficult to achieve supersolar C/O ratios in the inner parts of protoplanetary discs when taking internal photoevaporation into account. This indicates the potential importance of photoevaporation for understanding the chemical evolution of these discs and the planets forming in them.

A link to the past: characterizing wandering black holes in Milky Way-type galaxies

Abstract A population of non-stellar black holes (≳100 M⊙) has been long predicted to wander the Milky Way. We aim to characterize this population by using the L-Galaxies semi-analytical model applied on top of the high resolution Millennium-II merger trees. Our results predict ∼10 wandering black holes with masses ∼2 × 103 M⊙ in a typical z = 0 Milky Way galaxy, accounting for $\sim 2\%$ of the total non-stellar black hole mass budget of the galaxy. We find that the locations of these wanderers correlate with their formation scenario. While the ones concentrated at ≲1 kpc from the galactic nucleus on the disc come from past galactic mergers, the ones formed as a consequence of ejections due to gravitational recoils or the disruption of satellite galaxies are typically located at ≳100 kpc. Such small and large distances might explain the absence of strong observational evidence for wandering black holes in the Milky Way. Our results also indicate that $\sim 67\%$ of the wandering population is conformed by the leftovers of black hole seeds that had little to no growth since their formation. We find that wandering black holes that are leftover seeds become wanderers at an earlier time with respect to grown seeds, and also come from more metal-poor galaxies. Finally, we show that the number of wandering black holes in a Milky Way-type galaxy depends on the seeding efficiency.

The Cumulation of Debris Clouds around a Fast-rotating Asteroid

Abstract The rotational mass loss has been realized to be a prevalent mechanism to produce low-speed debris near the asteroid, and the size composition of the asteroid’s surface regolith has been closely measured by in situ explorations. However, the full-scale evolution of the shedding debris has not been examined using the observed particle sizes, which may hold vital clues to the initial growth of an asteroid moonlet and help us to understand the general mechanisms that dominate the formation of asteroid systems. This paper presents our study on the cumulative evolution of the debris cloud formed by a rotationally unstable asteroid. A semianalytical model is developed to characterize the spatiotemporal evolution of the debris cloud posterior to a shedding event. Large-scale discrete element method (DEM) simulations are performed to quantify the clustering behavior of the debris particles in the mechanical environment near the asteroid. As a result, we found that the cumulation of a steady debris cloud is dominated by large pieces of debris, and the shedding particles follow a common migration trend, which fundamentally determines the mass distribution of the debris cloud. For the accretion analysis, we sketched the life cycle of a debris cluster and showed its dependency on particle size. The DEM simulations adopt physical parameters estimated from observations and asteroid missions. The results confirm that porous fluffy cluster structures can form shortly after a shedding event with magnitudes the same as the observed shedding activities. Measurements of these structures show that they themselves possess a certain strength and have the capacity to collisions to absorb dissociative particles that collide with them.

CLASSY. X. Highlighting Differences between Partial Covering and Semianalytic Modeling in the Estimation of Galactic Outflow Properties

Feedback-driven massive outflows play a crucial role in galaxy evolution by regulating star formation and influencing the dynamics of surrounding media. Extracting outflow properties from spectral lines is a notoriously difficult process for a number of reasons, including the possibility that a substantial fraction of the outflow is carried by dense gas in a very narrow range in velocity. This gas can hide in spectra with insufficient resolution. Empirically motivated analysis based on the apparent optical depth method, commonly used in the literature, neglects the contribution of this gas, and may therefore underestimate the true gas column density. More complex semianalytical line transfer (e.g., SALT) models, on the other hand, allow for the presence of this gas by modeling the radial density and velocity of the outflows as power laws. Here we compare the two approaches to quantify the uncertainties in the inferences of outflow properties based on 1D “down-the-barrel” spectra, using the UV spectra of the CLASSY galaxy sample. We find that empirical modeling may significantly underestimate the column densities relative to SALT analysis, particularly in the optically thick regime. We use simulations to show that the main reason for this discrepancy is the presence of a large amount of dense material at low velocities, which can be hidden by the finite spectral resolution of the data. The SALT models in turn could overestimate the column densities if the assumed power laws of the density profiles are not a property of actual outflows.

Energy Evolution in the Progenitor of Galaxy Shells: A Semi-analytical Model

The stellar shells surrounding an elliptical galaxy, as remnants of a dwarf galaxy disrupted during merging, reveal the distribution of energy and angular momentum of the progenitor dwarf galaxy. We develop a semi-analytical model to describe the changes in energy ΔE i and angular momentum ΔLz i for particles during the first infall. We show that these changes, induced by the self-gravity of the progenitor, are important in broadening the initial energy distribution of the Plummer or Hernquist progenitor model. Consequently, these changes are crucial in shaping the shells. In the freefall stage following the disintegration of the progenitor potential, particles are no longer bound by self-gravity but move within the gravitational potential of the target galaxy. We investigate the relationship between the radial period and the energy of particles undergoing radial motion. We show that an accurate model of the energy range of the dwarf galaxy at disruption is essential to predict the number of observable shells.

An upper limit on the spins of merging binary black holes formed through isolated binary evolution

As the sensitivity of ground-based gravitational wave detectors progressively increases, observations of black hole mergers will provide us with the joint distribution of their masses and spins. This will be a critical benchmark to validate different formation scenarios. Merging binary black holes formed through the evolution of isolated binary systems require both components to be stripped of their hydrogen envelopes before core-collapse. The rotation rates of such stripped stars are constrained by the critical rotation limit at their surface, including its deviation from the Keplerian value owing to the outward force provided by radiation. This sets a restriction on their angular momentum content at core-collapse. We aim to determine if this restriction plays a role in the spins of binary black hole mergers. We used detailed calculations of stripped stars with the MESA code at low metallicities ($Z=Z_ $Z_ and $Z_ to determine the dimensionless spins of black holes produced by critically rotating stellar progenitors. To study how such progenitors can arise, we considered their formation through chemically homogeneous evolution (CHE) in binary stars. We used a semi-analytical model to study the physical processes that determine the final angular momentum of CHE binaries, and compared our results against available population synthesis models that rely on detailed binary evolution calculations. We find that above black hole masses of $ 25M_ the dimensionless spin parameter of critically rotating stripped stars ($a=Jc/(GM^2)$) is below unity. This results in an exclusion region at high chirp masses and effective spins that cannot be populated by isolated binary evolution. CHE can produce binaries where both black holes hit this limit, producing a pileup at the boundary of the excluded region. High-spin black holes arise from very low-metallicity CHE systems with short delay times, which merge at higher redshifts. On the other hand, the contribution of CHE to merging binary black holes detected in the third observing run of the LVK collaboration is expected to be dominated by systems with low spins ($ eff <0.5$) that merge near redshift zero. Owing to its higher projected sensitivity and runtime, the fourth observing run of the LVK collaboration can potentially place constraints on the high-spin population and the existence of a limit set by critical rotation.

Off-Axis Color Characteristics of Binary Neutron Star Merger Events: Applications for Space Multi-Band Variable Object Monitor and James Webb Space Telescope

With advancements in gravitational wave detection technology, an increasing number of binary neutron star (BNS) merger events are expected to be detected. Due to the narrow opening angle of jet cores, many BNS merger events occur off-axis, resulting in numerous gamma-ray bursts (GRBs) going undetected. Models suggest that kilonovae, which can be observed off-axis, offer more opportunities to be detected in the optical/near-infrared band as electromagnetic counterparts of BNS merger events. In this study, we calculate kilonova emission using a three-dimensional semi-analytical code and model the GRB afterglow emission with the open-source Python package afterglowpy at various inclination angles. Our results show that it is possible to identify the kilonova signal from the observed color evolution of BNS merger events. We also deduce the optimal observing window for SVOM/VT and JWST/NIRCam, which depends on the viewing angle, jet opening angle, and circumburst density. These parameters can be cross-checked with the multi-band afterglow fitting. We suggest that kilonovae are more likely to be identified at larger inclination angles, which can also help determine whether the observed signals without accompanying GRBs originate from BNS mergers.

A prediction method of oil recovery for hot water chemical flooding in heavy oil reservoirs: Semi-analytical stream tube model

Abstract Chemical agents (polymer and surfactant) assisted hot water flooding is an effective means of enhancing oil recovery in heterogeneous and heavy oil reservoirs. The rapid prediction of oil recovery through hot water chemical flooding is very important. The stream tube model is a fast analytical method for predicting water flooding recovery, but it is not suitable for hot water chemical flooding. In this paper, a permeability distribution model for multi-stream tubes is established based on permeability variation coefficient using normal distribution function for reservoir heterogeneity, Using GOMPERTZ growth function model to characterize the changes in stream tube temperature, polymer viscosity, and surfactant concentration with injection volume, Using Brooks-Corey model to describe the influence of interfacial tension and temperature on the relative permeability curve. Finally, an analytical stream tube model for hot water chemical flooding of heavy oil reservoirs was established. The time discrete method is used to solve the model, then the graphs of the relationship between oil recovery and water cut are obtained. Compared with numerical simulation methods, the prediction error of oil recovery is less than 2%, and the calculation time is reduced by 89%. This model has been successfully applied to X oilfield. Based on historical fitting, it is predicted that hot water chemical flooding can enhance oil recovery by 6.3% compared to water flooding. This paper provides a fast calculation method for predicting and evaluating the effectiveness of hot water chemical flooding in heavy oil reservoirs.

Impact of human-induced alterations in bathymetry and geometry on tidal and salt dynamics: Thresholds for morphological dimensions in a convergent estuary

Estuary morphology changes significantly with intensive human intervention, resulting in dynamic structural variations in the estuary. However, little is known about the threshold sizes of estuary morphology that ensure water security. A two-dimensional width-averaged semi-analytical model is applied to explore the impacts of human-induced alterations in bathymetry and geometry on tidal and salt dynamics in Lingdingyang Bay (LDYB). Salt flux (Fs) is positively correlated with tidal flux (Ft) and negatively correlated with tidal energy flux (Fte). Greater geometric convergence reduces Ft and increase Fte. Increased water depth increases Ft and Fte. Thus, both greater geometric convergence and increased bathymetry enhance tidal hydrodynamics. Saltwater transport is weakened by greater geometric convergence and enhanced by increasing water depth. Sensitivity experiments are conducted using maximum water level and salt intrusion length as the criterion. Thresholds for morphological sizes in the LDYB are found to be a convergence ratio (convergence length over mouth width,LcB0) of 0.83–0.88 and a combined depth factor (α) of 1.04–1.07. Moreover, transition of the estuarine morphology from an exponential convergent shape to a prismatic shape had a limited effect on tidal hydrodynamics when the convergent length rate (e-folding convergence length over total convergence length,LeLc) is >0.61. These results notice that human activities, such as reclamation and tidal channel dredging, exacerbate the risk of salt intrusion and should be applied with caution.

Acoustic radiation characteristics of shark skin inspired surface modified plates

This paper aims to evaluate the acoustic radiation characteristics of thin plates featuring a layer of small-scale biomimetic shark skin type additive surface treatment. The shark skin dermal denticles are modelled as point masses arranged in a bi-directional pattern on both the upper and lower surfaces of the plate. The governing equations are obtained through a variational approach, incorporating the Dirac Delta function in the derivation of the proposed semi-analytical model for the shark skin layer. A semi-analytical method based on the Rayleigh–Ritz formulation is utilized to analyze the vibrations of these plates with surface modification. The sound radiation characteristics are then derived from the solution of the Rayleigh integral. A comprehensive investigation is performed on the influence of surface modification on different vibro-acoustic characteristics, using a continuous structural mode and power transfer matrix-based approach. Notable observations include a reduction in peak vibro-acoustic responses with dense denticle arrangements, especially at resonance, demonstrating a direct relationship with mass ratios, i.e., the ratio of denticle mass to plate mass. The study further reveals a shift of vibro-acoustic responses towards low frequencies with an increase in mass ratios. A thorough comparative study indicates that while additive surface modifications inspired by shark skin may weaken sound radiation characteristics at resonance frequencies, a reverse effect can be observed at intermittent operational frequencies.

A new semi-analytic model for Stern-layer polarization in pore throats

SUMMARY To explain induced polarization, membrane polarization is often referred to as a relevant process taking place in granular media – particularly, when narrow pore throats are present. This polarization effect is based on the membrane-like behaviour of pore throats caused by the presence of an usually negative charge on the pore surface, that influences charge transport in the pore fluid. Existing analytical, 1D models describe the pore system as a series of cylindrical pores with different radii and lengths. The polarization response is calculated by solving the Poisson–Nernst–Planck system for the current densities of one single anion and one single cation species representing the charge transport in the electrolyte and the diffuse layer at the pore surface. To include charge transport in the Stern layer, cations in the Stern layer have so far simply been considered by increasing the concentration of the diffuse layer cations. As we know from numerical modelling, this approach fails to predict the polarization response when the Stern layer is significantly charged. Here, we present a new semi-analytical model that treats the Stern-layer cations as a separate ion species and allows the Stern layer to polarize individually. To validate our new model, we compare it to the previously used analytical model and numerical simulations for different relative charges in Stern- and diffuse layer. We also use electrostatic surface-complexation models for two mineral surfaces (quartz and montmorillonite) to simulate the response of real geologic material under varying chemical conditions. This work is a step forward for considering realistic pore properties in induced-polarization modelling.

A semi-analytical model for predicting the shear buckling of laminated composite honeycomb cores in sandwich panels

Laminated composite honeycomb cellular core sandwich panels are widely utilized in various industries due to their exceptional stiffness-to-weight ratio and strength characteristics. Current analytical models often simplify honeycomb cores as homogenized continua, effectively predicting stiffness but falling short in capturing crucial failure modes, particularly shear buckling of honeycomb core walls. Existing theoretical studies on shear buckling are limited to isotropic materials and specific honeycomb geometries. While numerical models can simulate cell wall buckling, their computational demands render them impractical for large structures employing sandwich panels. This paper introduces a novel, simplified semi-analytical approach that accurately predicts the shear buckling load of laminated composite honeycomb cellular cores. The model accounts for bend-twist coupling effects and rotational restraints at laminate wall boundaries. To validate the proposed approach, predictions are compared with finite element analysis results for hexagonal honeycomb cores and cores of varying shapes, incorporating diverse fibre lay-up configurations. The findings demonstrate excellent agreement between the proposed approach and finite element analysis, indicating its reliability in predicting shear buckling. This research addresses the gap in existing methodologies by offering a practical and efficient tool for predicting shear buckling in laminated composite honeycomb cores, extending applicability beyond isotropic materials and specific honeycomb geometries. The proposed approach holds promise for optimizing the design and structural integrity of sandwich panels, impacting industries relying on these lightweight and high-performance structures.

A piezoelectric acoustic black hole absorber for rail vibration reduction and energy harvesting: Semi-analytical model

Theoretically, vibration energy can be converted and harvested during the process of vibration reduction, thus enabling a self-powered supply for sensor nodes. However, little research was reported on rail absorbers that combine vibration reduction and energy harvesting. Accordingly, this study aims to design an absorber based on the acoustic black hole (ABH) effect, termed the P-ABH absorber, that can simultaneously achieve broadband vibration reduction and energy harvesting. Firstly, the P-ABH absorber was preliminarily designed, and the semi-analytical model of the track with the P-ABH absorber was established by the Rayleigh-Ritz method. Secondly, the semi-analytical model was verified by the 3D finite element method, and the vibration reduction and energy harvesting performance were initially evaluated. The dimensions of the ABH structure, along with the sizes of the piezoelectric patches, were then determined. Finally, the vibration reduction and energy harvesting performances of the P-ABH absorbers fully deployed between each fastener were evaluated. The results demonstrated that the P-ABH absorber exhibited a wider vibration reduction bandwidth than the uniform piezoelectric absorber and the piezoelectric patches, with an increase in energy harvesting power by 27.47 % and 115.26 %, respectively. The vibration reduction and energy harvesting performance were significantly affected by the number of piezoelectric patches but little affected by the thickness and total length. When the P-ABH absorbers were fully attached to the rail, the overall mean square velocities at the three resonant frequencies, which required emphatic control, were reduced by 36.77 %, 98.37 %, and 3.52 %, respectively. Meanwhile, the energy harvesting performance was excellent. The P-ABH absorber presents a promising solution for improving the sustainability and cost-effectiveness of track systems.

Acoustic materials based on the Gosper curve

In this work, slotted acoustic materials based on a space filling curve called the Peano-Gosper curve are proposed and investigated. The slits in such materials form a complex pattern because they are divided by walls built along lines generated by the Gosper curve algorithm. The pattern can be twisted around an axis normal to its surface to increase the tortuosity inside the material, and therefore, modify its acoustic properties, which can be controlled by the turning angle or pitch of the twist. A highly efficient semi-analytical model has been developed to accurately predict the acoustic properties, in particular the sound absorption of such materials. It only requires a representative part of the pattern, or better, scanning the surface of the fabricated material so that the actual geometry and dimensions (in particular slit widths) are well reproduced in a two-dimensional finite element mesh generated on a representative fluid domain. The mesh is used to solve a dedicated Poisson problem and determine a few key parameters, and the rest of the modelling is based on analytical formulas. Material samples with straight and twisted slit patterns were 3D printed and then measured in an impedance tube to confirm semi-analytical sound absorption predictions.

Noise propagation variations over long distances over water

This paper investigates the short temporal variations of noise propagation over a water surface for long distances. Analysis is formed on the results of a measurement campaign for downwind noise propagation over water for elevated sound sources. Noise propagation over water for elevated noise sources is specifically relevant for offshore wind turbines, near shore wind turbines or wind turbines on land close to large water bodies. The measurement setup is a height-adjustable sound source placed at three different heights 81 m, 50 m and 30 m above ground and microphones positioned downwind at shore and ~100 m inland at three different distances over water from the sound source ~3 km, ~5 km and ~7 km. The meteorological conditions wind speed, wind direction, atmospheric stability, temperature, humidity, etc. were monitored continuously at both ends of the setup, utilizing both a tall met mast, a wind profiler and sonic anemometers at multiple heights. The results are used for improving auralisations of noise from offshore wind turbines and offshore wind farms. In addition to this a semi-analytical model for propagation over water is tested.

Vibration damping of sandwich panels using the Acoustic Black Hole effect

Among the existing passive vibration control techniques, the use of the acoustic black hole (ABH) is a solution that has the advantage of not increasing the mass of the structure in which it is integrated. In this paper, the benefits of inserting an ABH into a three-layer sandwich panel (fibreglass skins and honeycomb core) are investigated. It is known that an ABH effect can be achieved in a panel by locally reducing its stiffness (using a reduction in plate thickness according to a power law profile) and increasing local damping (using a coating of viscoelastic material). A sandwich panel induces a shear effect that strongly affect the wave propagation and lead to specific properties to the ABH effect. The equations of motion of a thick, symmetrical sandwich panel with non-uniform characteristics are obtained within the framework of zig-zag theory by applying Hamilton's principle. These equations lead to a semi-analytical model of order 6, from which an effective bending stiffness, dependent on both frequency and space can be derived. Using this model, it is demonstrated that the sandwich effective bending stiffness favours the ABH effect. This interesting property is also validated by experimental tests on sandwich panels using laser vibrometry.

Layout Optimization of Wave Energy Park Based on Multi-Objective Optimization Algorithm

Abstract In this paper, both semi-analytical method and numerical simulation is applied to investigate the hydrodynamic behavior of large arrays of point-absorber wave energy converters (WECs). To analyze wave interactions among multiple WECs within an array, a semi-analytical model is developed based on the potential flow theory and the matched eigen-function expansions method. The fluid domain is divided into two kinds of regions: interior regions underneath the cylinders and an exterior region surrounding all the cylinders. The matched eigenfunction expansions method is employed to solve the radiation potential problem in each domain, and the hydrodynamic coefficients and motion response of the cylinders in the array are evaluated. To validate the accuracy of the semi-analytical method, WAMIT is adopted to simulate the wave energy park numerically and compared with the results by the semi-analytical model. The hydrodynamic characteristics and power absorption performance of the WECs within the wave energy park are analyzed. The power performance of a wave energy park is studied as functions of layout geometry, incident wave direction and separation distance between WECs respectively. Finally, MOPSO based on a surrogate model is used to optimize the layout of wave energy array.

The Impact of Positive AGN Feedback on the Properties of Galaxies in a Semianalytic Model of Galaxy Formation

We introduce the state-of-the-art semianalytic model Formation and Evolution of GAlaxies (FEGA), which incorporates updated prescriptions for key physical processes in galaxy formation. Notably, FEGA features an unprecedented semianalytic modeling of positive active galactic nucleus (AGN) feedback. The model combines the latest prescriptions for gas infall and cooling, a revised star formation recipe that incorporates the extended Kennicutt–Schmidt relation, disk instability, updated supernova feedback, reincorporation of ejected gas, hot gas stripping from satellite galaxies, and the formation of diffuse light. A novel description of AGN feedback is introduced, describing the positive mode as a burst of star formation from a cooling gas fraction. FEGA is rigorously calibrated using a Markov Chain Monte Carlo procedure to match the evolution of the stellar mass function from high redshift to the present. Subsequently, the model is tested against several observed and predicted scaling relations, including the star formation rate (SFR)–mass, black hole–bulge and stellar mass, stellar-to-halo mass, and red fraction–mass relations. Additionally, we test FEGA against other galaxy properties, such as the distribution of specific SFRs, stellar metallicity, and morphology. Our results demonstrate that the inclusion of positive AGN feedback can coexist with its negative counterpart without drastic alterations to other prescriptions. Importantly, this inclusion improves the ability of the model to describe the primary scaling relations observed in galaxies.