A Simulation of the Dependence of Tidal Interaction on Galaxy Type in Compact Groups

We have investigated the role that different galaxy types have in galaxy-galaxy interactions in compact groups. N-body simulations of 6 galaxies consisting of a differing mixture of galaxy types were run to compare the relative importance of galaxy population demographic on evolution. Three different groups with differing galaxy content were tested: all spiral, a single elliptical and 50% elliptical. Tidal interaction strength and duration were recorded to assess the importance of an interaction. A group with an equal number of spiral and elliptical galaxies has some of the longest and strongest interactions with elliptical-elliptical interactions being most significant. These elliptical-elliptical interactions are not dominated by a single large event but consist of multiple interactions. Elliptical galaxies tidally interacting with spiral galaxies, have the next strongest interaction events. For the case when a group only has a single elliptical, the largest magnitude tidal interaction is an elliptical on a spiral. Spirals interact with each other through many small interactions. For a spiral only group, the interactions are the weakest compared to the other group types. These spiral interactions are not dominated by any singular event that might be expected to lead to a merger but are more of an ongoing harassment. These results suggest that within a compact group, early type galaxies will not form via merger out of an assemblage of spiral galaxies but rather that compact groups, in effect form around an early type galaxy.

迈进Galaxy AI新时代,三星Galaxy S24系列正式发布

2024年1月18日,三星电子正式发布了新一代高端旗舰系列产品,包括三星GalaxyS24Ultra、Galaxy S24+和Galaxy S24。通过引入创新的GalaxyAI,新一代三星Galaxy S系列将重新定义移动设备,为用户提供更强大的功能,开启全新的移动体验时代。这一系列产品将利用智能文本和通话翻译等功能,实现无障碍交流;采用Galaxy超视觉影像释放用户创意;以全新的搜索方式助力Galaxy用户更好地探索世界。三星GalaxyS24系列将充分发挥人工智能的优势,全面提升用户的移动体验。

三星Galaxy Z Fold6/Z Flip6成都品鉴会:体验智慧AI“星”生活

8月21日,三星Galaxy新品媒体品鉴会在成都举行。本次品鉴会上,三星带来了旗下最新的第6代折叠屏手机Galaxy Z Fold6和Galaxy Z Flip6,以及三星智能穿戴设备Galaxy Ring,Galaxy Watch Ultra,Galaxy Watch7与Galaxy Buds3系列。这些产品不仅展示了三星对Galaxy AI的最新探索成果,将AI赋能到Galaxy新品后还会为人们提供更便捷、智能、高效的生活新体验。

三星Galaxy S24系列中国发布,Galaxy AI塑造智能手机新体验

2024年1月25日,三星电子面向中国市场正式发布了新一代高端旗舰智能手机一—三星Galaxy S24系列,包括3款产品:三星GalaxyS24Ultra、Galaxy S24+和Galaxy S24。通过引人创新的Galaxy AI技术,三星Galaxy S24系列将人工智能优势融入智能手机。

HI in High Gas-phase Metallicity Dwarf Galaxy WISEA J230615.06+143927.9

We present resolved Giant Metrewave Radio Telescope H I observations of the high gas-phase metallicity dwarf galaxy WISEA J230615.06+143927.9(z = 0.005)(hereafter J2306) and investigate whether it could be a Tidal Dwarf Galaxy(TDG) candidate. TDGs are observed to have higher metallicities than normal dwarfs. J2306 has an unusual combination of a blue g-r color of 0.23 mag, irregular optical morphology and high-metallicity(12 +log(O/H) = 8.68 ± 0.14), making it an interesting galaxy to study in more detail. We find J2306 to be an H I rich galaxy with a large extended, unperturbed rotating H I disk. Using our H I data we estimated its dynamical mass and found the galaxy to be dark matter(DM) dominated within its H I radius. The quantity of DM, inferred from its dynamical mass, appears to rule out J2306 as an evolved TDG. A wide area environment search reveals J2306 to be isolated from any larger galaxies which could have been the source of its high gas metallicity. Additionally, the H I morphology and kinematics of the galaxy show no indication of a recent merger to explain the high-metallicity.Further detailed optical spectroscopic observations of J2306 might provide an answer to how a seemingly ordinary irregular dwarf galaxy achieved such a high level of metal enrichment.

A Possible X-ray Quasi-periodic Oscillation in the Narrow-line Seyfert 1 Galaxy Mrk 142

A possible quasi-periodic oscillation(QPO) at frequency 7.045 × 10^(-5) Hz is found in the narrow-line Seyfert 1galaxy Mrk 142 in the data of XMM-Newton collected on 2020 April 11.We find that the QPO signal is statistically significantly larger than the 5σ level and highly coherent with quality factor Q > 5 at the 0.3–10 keV band by using the method of the Lomb–Scargle Periodogram,the Weighted Wavelet Z-transform and the REDFIT.We analyze the data in 0.3–0.6 keV,0.6–1 keV,1–3 keV and 3–10 keV energy bands,and find obvious QPO signals at 0.3–0.6 keV and 1–3 keV bands.We then analyze the time-average spectra and time variability at the QPO frequency of 7.045 × 10^(-5) Hz,and use a model to fit them.We find that the QPO signal mainly comes from the X-ray hot corona.

Long Term X-Ray Spectral Variations of the Seyfert-1 Galaxy Mrk 279

We present the results from a long term X-ray analysis of Mrk 279 during the period 2018–2020.We use data from multiple missions–AstroSat,NuSTAR and XMM-Newton,for the purpose.The X-ray spectrum can be modeled as a double Comptonization along with the presence of neutral Fe Kαline emission,at all epochs.We determined the source’s X-ray flux and luminosity at these different epochs.We find significant variations in the source’s flux state.We also investigate the variations in the source’s spectral components during the observation period.We find that the photon index and hence the spectral shape follow the variations only over longer time periods.We probe the correlations between fluxes of different bands and their photon indices,and found no significant correlations between the parameters.

New HⅠObservations Toward the NGC 5055 Galaxy Group with FAST

We report a new high-sensitivity HⅠmapping observation of the NGC 5055 galaxy group over an area of 1°.5×0°.75 with the Five-hundred-meter Aperture Spherical radio Telescope(FAST).Our observation reveals that the warped HⅠdisk of NGC 5055 is more extended than what was previously observed by WSRT,out to239(61.7 kpc).The total HⅠmass of NGC 5055 is determined to be~1.1×10^(10)M_Θ.We identified three HⅠclouds with HⅠmasses of the order of~10^(7)M_Θat the southeastern edge of the HⅠdisk,as well as a candidate high-velocity cloud with an HⅠmass of(1.2±0.5)×10^(6)M_Θto the north of NGC 5055.The HⅠcontent of UGCA337 is robustly detected for the first time by the FAST observations.It has a narrow HⅠlinewidth of W_(50)=17.4±3.8 km s^(-1)with a total HⅠmass of(3.5±0.3)×10^(6)M_Θ.Comparing the gas content and g-r color of UGCA 337 with typical low-mass dwarf galaxies,UGCA 337 appears relatively gas-poor despite its blue color.This suggests that UGCA 337 may have undergone gas stripping in the past.We also analyzed the possible origin of the diffuse HⅠclouds located at the outskirts of NGC 5055,and speculate that they might be the remnant features of a merger event in the past.

A Hyperparameter Optimization for Galaxy Classification

In this study,the morphological galaxy classification process was carried out with a hybrid approach.Since the Galaxy classification process may contain detailed information about the universe’s formation,it remains the current research topic.Researchers divided more than 100 billion galaxies into ten different classes.It is not always possible to understand which class the galaxy types belong.However,Artificial Intelligence(AI)can be used for successful classification.There are studies on the automatic classification of galaxies into a small number of classes.As the number of classes increases,the success of the used methods decreases.Based on the literature,the classification using Convolutional Neural Network(CNN)is better.Three metaheuristic algorithms are used to obtain the optimum architecture of CNN.These are Grey Wolf Optimizer(GWO),Particle Swarm Optimization(PSO)and Artificial Bee Colony(ABC)algorithms.A CNN architecture with nine hidden layers and two full connected layers was used.The number of neurons in the hidden layers and the fully connected layers,the learning coefficient and the batch size values were optimized.The classification accuracy of my model was 85%.The best results were obtained usingGWO.Manual optimization of CNN is difficult.It was carried out with the help of the GWO meta-heuristic algorithm.

Electromagnetic-Wave Mechanism of Formation and Propagation of Astrophysical Vortex Jets Generated in the Jumper of a Spiral Galaxy

An explanation of the mechanism of generation and acceleration of jets in outer space is given on the basis of experiments in the physics of electrical discharge. The presence of two arms in the spiral Galaxy gives grounds to assume that they have excess charges of the opposite sign. At the moment when the electric field strength between the tips of the arms becomes sufficient, an electrical breakdown occurs, which is accompanied by the movement of the current-plasma leader in the jumper between the tips of the arms. In the head part of the leader there is a flat electric domain of a strong field, which, during its inception, emits intense transverse electromagnetic waves in a direction perpendicular to the direction of the leader’s motion and to the plane of the accretion disk. The electric domain periodically appears and collapses due to the entry of neutral particles. Transverse electromagnetic waves capture charged particles from the discharge region and accelerate them in the direction of wave propagation. The crossed fields of an electromagnetic wave perform the functions of a multistage accelerator. The acceleration of the particles of the plasma produced in the discharge to relativistic energy values in the region of narrow vortex jets occurs under the action of forces caused by the components of the electromagnetic wave fields and the pressure gradient. The charged particles of a vortex jet acquire a significant rotational moment under the action of the Lorentz force. Explanations of the generation of microwave, bremsstrahlung and optical radiation from the region of the jumper between the arms of the Galaxy in the absence of electrical breakdown are also given.

Mock X-Ray Observations of Hot Gas with L-Galaxies Semi-analytic Models of Galaxy Formation

We create mock X-ray observations of hot gas in galaxy clusters with a new extension of the L-Galaxies semianalytic model of galaxy formation,which includes the radial distribution of hot gas in each halo.Based on the model outputs,we first build some mock light cones,then generate mock spectra with the SOXS package and derive the mock images in the light cones.Using the mock data,we simulate mock X-ray spectra for the ROSAT all-sky survey,and compare the mock spectra with the observational results.Then,we consider the design parameters of the HUBS mission and simulate the observation of the halo hot gas for HUBS as an important application of our mock work.We find:(1)our mock data match the observations by current X-ray telescopes.(2)The survey of hot baryons in resolved clusters by HUBS is effective below redshift 0.5,and the observations of the emission lines in point-like sources at z>0.5 by HUBS help us understand the hot baryons in the early universe.(3)By taking advantage of the large simulation box and flexibility in semi-analytic models,our mock X-ray observations provide the opportunity to select targets and observation strategies for forthcoming X-ray facilities.

Velocity Dispersion σ_(aper)Aperture Corrections as a Function of Galaxy Properties from Integral-field Stellar Kinematics of 10,000 MaNGA Galaxies

The second moment of the stellar velocity within the effective radius,denoted by σ^(2)_(e),is a crucial quantity in galaxy studies,as it provides insight into galaxy properties and their mass distributions.However,large spectroscopic surveys typically do not measure σ_(e) directly,instead providing σ_(aper),the second moment of the stellar velocity within a fixed fiber aperture.In this paper,we derive an empirical aperture correction formula,given byσ_(aper)/σ_(e)=(R_(aper)/R_(e))^(α),using spatially resolved stellar kinematics extracted from approximately 10,000 Sloan Digital Sky Survey-Mapping Nearby Galaxies at Apache Point Observatory integral field unit observations.Our analysis reveals a strong dependence ofαon the r-band absolute magnitude M_(r),g-i color,and Sérsic index nSer,whereαvalues are lower for brighter,redder galaxies with higher Sérsic indices.Our results demonstrate that the aperture correction derived from previous literature on early-type galaxies cannot be applied to predict the aperture corrections for galaxies with intermediate Sérsic indices.We provide a lookup table ofαvalues for different galaxy types,with parameters in the ranges of-18>M_(r)>-24,0.4<g-i<1.6,and 0<n_(Ser)<8.A Python script is provided to obtain the correction factors from the lookup table.

Galaxy Interactions in Filaments and Sheets:Insights from EAGLE Simulations

We study the color and star formation rates of paired galaxies in filaments and sheets using the EAGLE simulations.We find that the major pairs with pair separation<50 kpc are bluer and more star-forming in filamentary environments compared to those hosted in sheet-like environments.This trend reverses beyond a pair separation of~50 kpc.The interacting pairs with larger separations(>50 kpc)in filaments are on average redder and low-star-forming compared to those embedded in sheets.The galaxies in filaments and sheets may have different stellar mass and cold gas mass distributions.Using a KS test,we find that for paired galaxies with pair separation<50 kpc,there are no significant differences in these properties in sheets and filaments.The filaments transport gas toward the cluster of galaxies.Some earlier studies find preferential alignment of galaxy pairs with the filament axis.Such alignment of galaxy pairs may lead to different gas accretion efficiency in galaxies residing in filaments and sheets.We propose that the enhancement of star formation rate at smaller pair separation in filaments is caused by the alignment of galaxy pairs.A recent study with SDSS data reports the same findings.The confirmation of these results by the EAGLE simulations suggests that the hydrodynamical simulations are powerful theoretical tools for studying galaxy formation and evolution in the cosmic web.

New Continuum Observations of the Andromeda galaxy M31 with FAST

We present a new total intensity image of M31 at 1.248 GHz,observed with the Five-hundred-meter Aperture Spherical radio telescope(FAST)with an angular resolution of 4'and a sensitivity of about 16 mK.The new FAST image clearly reveals weak emission outside the ring due to its high sensitivity on large-scale structures.We derive a scale length of 2.7 kpc for the cosmic ray electrons and find that the cosmic ray electrons propagate mainly through diffusion by comparing the scale length at 4.8 GHz.The spectral index of the total intensity varies along the ring,which can be attributed to the variation of the spectra of synchrotron emission.This variation is likely caused by the change of star formation rates along the ring.We find that the azimuthal profile of the non-thermal emission can be interpreted by an axisymmetric large-scale magnetic field with varying pitch angle along the ring,indicating a complicated magnetic field configuration in M31.

The Way to Quench:Galaxy Evolution in A2142

We show how the star formation activity of galaxies is progressively inhibited from the outer region to the center of the massive cluster A2142.From an extended spectroscopic redshift survey of 2239 galaxies covering a circular area of radius~11 Mpc from the cluster center,we extract a sample of 333 galaxies with known stellar mass,star formation rate,and spectral index D_(n)4000.We use the Blooming Tree algorithm to identify the substructures of the cluster and separate the galaxy sample into substructure galaxies,halo galaxies,and outskirt galaxies.The substructure and halo galaxies are cluster members,whereas the outskirt galaxies are only weakly gravitationally bound to the cluster.For the cluster members,the star formation rate per stellar mass decreases with decreasing distance R from the cluster center.Similarly,the spectral index D_(n)4000 increases with R,indicating an increasing average age of the stellar population in galaxies closer to the cluster center.In addition,star formation in substructure galaxies is generally more active than in halo galaxies and less active than in outskirt galaxies,proving that substructures tend to slow down the transition between field galaxies and cluster galaxies.We finally show that most actively star-forming galaxies are within the cluster infall region,whereas most galaxies in the central region are quiescent.

The Unusual AGN Host NGC 1266:Evidence for Shocks in a Molecular Gas Rich S0 Galaxy with a Low Luminosity Nucleus

NGC 1266 is a lenticular galaxy(S0)hosting an active galactic nucleus(AGN),and known to contain a large amount of shocked gas.We compare the luminosity ratio of mid-J CO lines to IR continuum with star-forming galaxies(SFGs),and then model the CO spectral line energy distribution(SLED).We confirm that in the mid-and high-J regions(J_(up)=4-13),the C-type shock(v_(s)=25 km s^(-1),n_(H)=5×10^(4)cm^(-3))can reproduce the CO observations well.The galaxy spectral energy distribution(SED)is constructed and modeled by the code X-CIGALE and obtains a set of physical parameters including the star formation rate(SFR,1.17±0.47 M_(⊙)yr^(-1)).Also,our work provides SFR derivation of[C II]from the neutral hydrogen regions only(1.38±0.14 M_(⊙)yr^(-1)).Previous studies have illusive conclusions on the AGN or starburst nature of the NGC 1266 nucleus.Our SED model shows that the hidden AGN in the system is intrinsically low-luminosity,consequently the infrared luminosity of the AGN does not reach the expected level.Archival data from Nu STAR hard X-ray observations in the 3-79 keV band shows a marginal detection,disfavoring presence of an obscured luminous AGN and implying that a compact starburst is more likely dominant for the NGC 1266 nucleus.

Galaxy Morphology Classification Using a Semi-supervised Learning Algorithm Based on Dynamic Threshold

Machine learning has become a crucial technique for classifying the morphology of galaxies as a result of the meteoric development of galactic data.Unfortunately,traditional supervised learning has significant learning costs since it needs a lot of labeled data to be effective.FixMatch,a semi-supervised learning algorithm that serves as a good method,is now a key tool for using large amounts of unlabeled data.Nevertheless,the performance degrades significantly when dealing with large,imbalanced data sets since FixMatch relies on a fixed threshold to filter pseudo-labels.Therefore,this study proposes a dynamic threshold alignment algorithm based on the FixMatch model.First,the class with the highest amount has its reliable pseudo-label ratio determined,and the remaining classes'reliable pseudo-label ratios are approximated in accordance.Second,based on the predicted reliable pseudo-label ratio for each category,it dynamically calculates the threshold for choosing pseudo-labels.By employing this dynamic threshold,the accuracy bias of each category is decreased and the learning of classes with less samples is improved.Experimental results show that in galaxy morphology classification tasks,compared with supervised learning,the proposed algorithm significantly improves performance.When the amount of labeled data is 100,the accuracy and F1-score are improved by 12.8%and 12.6%,respectively.Compared with popular semisupervised algorithms such as FixMatch and MixMatch,the proposed algorithm has better classification performance,greatly reducing the accuracy bias of each category.When the amount of labeled data is 1000,the accuracy of cigar-shaped smooth galaxies with the smallest sample is improved by 37.94%compared to FixMatch.

Spatially Resolved Properties of the GW170817 Host Galaxy

GW170817 is the unique gravitational-wave(GW)event associated with the electromagnetic(EM)counterpart GRB 170817A.NGC 4993 is identified as the host galaxy of GW170817/GRB 170817A.In this paper,we focus on the spatially resolved properties of NGC 4993.We present the photometric results from the comprehensive data analysis of the high spatial-resolution images in the different optical bands.The morphological analysis reveals that NGC 4993 is a typical early-type galaxy without significant remnants of a major galaxy merger.The spatially resolved stellar population properties of NGC 4993 suggest that the galaxy center has passive evolution with the outskirt formed by gas accretion.We derive the merging rate of the compact object per galaxy by a co-evolution scenario of a supermassive black hole and its host galaxy.If the galaxy formation is at redshift 1.0,the merging rate per galaxy is from 3.2×10^(-4)to 7.7×10^(-5)within the merging decay time from 1.0 to 5.0 Gyr.The results provide vital information for ongoing GW EM counterpart detections.The Hubble space telescope data analysis presented in this paper can be also applied to Chinese Space Station Telescope research in the future.

HⅠGalaxy Detections in the Zone of Avoidance with FAST

The Zone of Avoidance(ZoA)is a region of low galactic latitude that is heavily obscured by the Milky Way.Observations with radio telescopes are basically unaffected by dust extinction and can unveil the structure behind it through the Milky Way.One of the scientific goals of the Five-hundred-meter Aperture Spherical radio Telescope(FAST)is to search for the neutral hydrogen and understand the large-scale physics to explore the origin and evolution of the universe.We take the 15,500 IRAS(the Infrared Astronomical Satellite)galaxies from PSCz(“Point Source Catalog”)survey to reconstruct the density field of the local universe,obtain the distribution of the relative density of galaxies in the ZoA region with a redshift z below 0.07,and the number of detectable galaxies with FAST is estimated by using the neutral hydrogen mass function of the ALFA(Arecibo L-band Feed Array)survey.We conclude that FAST can observe more than 2000 ZoA galaxies within a distance of 300 Mpc h_(70)^(-1),and present preliminary results of the partial GPPS(the FAST Galactic Plane Pulsar Snapshot survey)data,compared with ALFA ZoA(The Arecibo L-band Feed Array Zone of Avoidance),show that FAST has a higher detection sensitivity to search for HI galaxies in the ZoA area.

The Yukawa and Exponential Potentials for a Galaxy’s Spherical Central Bulge*

By adding an extra term to the Newtonian potential, matter outside the orbit of a star adds to the gravitational acceleration acting on that star. In this work, we solve the Poisson equation for non-Newtonian potentials of a spherically symmetric distribution of mass. We derive equations for calculating the centripetal acceleration and velocity of galactic disk stars that are due to the Newtonian and exponential potentials of the galaxy’s central bulge.