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A Review of the Mixing Length Theory of Convection in 1D Stellar Modeling 一维恒星模拟中对流混合长度理论综述
IF 2.5
Galaxies Pub Date : 2023-03-16 DOI: 10.3390/galaxies11030075
M. Joyce, J. Tayar
{"title":"A Review of the Mixing Length Theory of Convection in 1D Stellar Modeling","authors":"M. Joyce, J. Tayar","doi":"10.3390/galaxies11030075","DOIUrl":"https://doi.org/10.3390/galaxies11030075","url":null,"abstract":"We review the application of the one-dimensional Mixing Length Theory (MLT) model of convection in stellar interiors and low-mass stellar evolution. We summarize the history of MLT, present a derivation of MLT in the context of 1D stellar structure equations, and discuss the physical regimes in which MLT is relevant. We review attempts to improve and extend the formalism, including to higher dimensions. We discuss the interactions of MLT with other modeling physics, and demonstrate the impact of introducing variations in the convective mixing length, αMLT, on stellar tracks and isochrones. We summarize the process of performing a solar calibration of αMLT and state-of-the-art on calibrations to non-solar targets. We discuss the scientific implications of changing the mixing length, using recent analyses for demonstration. We review the most prominent successes of MLT, and the remaining challenges, and we conclude by speculating on the future of this treatment of convection.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46852365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Simulating the Enrichment of Fossil Radio Electrons by Multiple Radio Galaxies 多个射电星系对化石射电电子富集的模拟
IF 2.5
Galaxies Pub Date : 2023-03-09 DOI: 10.3390/galaxies11020045
F. Vazza, D. Wittor, M. Brüggen, G. Brunetti
{"title":"Simulating the Enrichment of Fossil Radio Electrons by Multiple Radio Galaxies","authors":"F. Vazza, D. Wittor, M. Brüggen, G. Brunetti","doi":"10.3390/galaxies11020045","DOIUrl":"https://doi.org/10.3390/galaxies11020045","url":null,"abstract":"We simulate the evolution of relativistic electrons injected into the intracluster medium by five radio galaxies. We study the spatial transport and the emission properties of the injected radio plasma over a ∼5 Gyr period, and the sequence of cooling and re-acceleration events experienced by electrons, using a Lagrangian approach joined with a numerical method to model the evolution of momentum spectra of relativistic electrons. When compared with electrons injected by shock waves, electrons injected by radio galaxies (here limited to a single injection event) in our tests are unable to fuel large ∼Mpc-sized radio relics with fossil electrons, as required by current theoretical models, while electrons previously seeded by other shocks can do this. On the other hand, the combination of seeding from radio galaxies and of re-acceleration events from plasma perturbation can produce detectable, small-scale, and filamentary emissions in the proximity (≤100–200 kpc) of radio galaxies.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44947546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Characterizing the Regular Orbits of Binary Pulsars: An Initial Prospection Study 描述双星脉冲星的规则轨道:初步展望研究
IF 2.5
Galaxies Pub Date : 2023-03-08 DOI: 10.3390/galaxies11020044
Ali Taani
{"title":"Characterizing the Regular Orbits of Binary Pulsars: An Initial Prospection Study","authors":"Ali Taani","doi":"10.3390/galaxies11020044","DOIUrl":"https://doi.org/10.3390/galaxies11020044","url":null,"abstract":"The dynamical interaction between binary systems is crucial in understanding the nature of orbital motion under the influence of gravitational potential. In our study, we focused on investigating the effects of dynamical forces on the regularity of binary pulsar orbits, which represent a pure two-body system. To incorporate the necessary time dependence and have a regular 3-D axisymmetric potential, we utilized the Rebound package as a numerical integrator. This package integrates the motion of particles under the influence of gravity, allowing for changing orbital parameters at a given instant, and providing a variety of integrators to be used. By analyzing the regularity properties of binaries and their sensitivity to initial conditions, we gained insight into the importance of considering even small perturbations to the system, as they can lead to significant changes in its dynamics.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45385438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network 利用东亚VLBI网络监测2019年活动状态下Sgr A*的大小和通量密度
IF 2.5
Galaxies Pub Date : 2023-03-08 DOI: 10.3390/galaxies11020046
Xiaopeng Cheng, I. Cho, T. Kawashima, M. Kino, Guangyao Zhao, J. Algaba, Yutaro Kofuji, Sang-Sung Lee, J. Lee, Wheeyeon Cheong, Wu Jiang, J. Oh
{"title":"Monitoring the Size and Flux Density of Sgr A* during the Active State in 2019 with East Asian VLBI Network","authors":"Xiaopeng Cheng, I. Cho, T. Kawashima, M. Kino, Guangyao Zhao, J. Algaba, Yutaro Kofuji, Sang-Sung Lee, J. Lee, Wheeyeon Cheong, Wu Jiang, J. Oh","doi":"10.3390/galaxies11020046","DOIUrl":"https://doi.org/10.3390/galaxies11020046","url":null,"abstract":"In this work, we studied the Galactic Center supermassive black hole (SMBH), Sagittarius A* (Sgr A*), with the KVN and VERA Array (KaVA)/East Asian VLBI Network (EAVN) monitoring observations. Especially in 13 May 2019, Sgr A* experienced an unprecedented bright near infra-red (NIR) flare; so, we find a possible counterpart at 43 GHz (7 mm). As a result, a large temporal variation of the flux density at the level ∼15.4%, with the highest flux density of 2.04 Jy, is found on 11 May 2019. Interestingly, the intrinsic sizes are also variable, and the area and major-axis size show marginal correlation with flux density with ≳2 σ. Thus, we interpret that the emission region at 43 GHz follows the larger-when-brighter relation in 2019. The possible origins are discussed with an emergence of a weak jet/outflow component and the position angle change of the rotation axis of the accretion disk in time.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42013256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Explaining the Hardening Structures of Helium Spectrum and Boron to Carbon Ratio through Different Propagation Models 用不同的传播模型解释氦谱和硼碳比的硬化结构
IF 2.5
Galaxies Pub Date : 2023-03-08 DOI: 10.3390/galaxies11020043
Q. Luo, Jie Feng, P. Tam
{"title":"Explaining the Hardening Structures of Helium Spectrum and Boron to Carbon Ratio through Different Propagation Models","authors":"Q. Luo, Jie Feng, P. Tam","doi":"10.3390/galaxies11020043","DOIUrl":"https://doi.org/10.3390/galaxies11020043","url":null,"abstract":"Recently, a series of high-precision measurements by various experiments show that cosmic ray nuclei spectra begin to harden at ∼200 GV and the boron-to-carbon (B/C) ratio has a similar trend around the same energy. These anomalous structures possibly result from the journey of cosmic rays (CRs) from their sources to our solar system, which has important implications for our understanding of the origin and propagation of Galactic cosmic rays (GCRs). In this work, we investigate several propagation models and attempt to explain these anomalous observations. We have verified that an extension of the traditional propagation model taking into account spatially dependent propagation and secondary particle acceleration provides a more accurate description of the latest B/C ratio and the Helium flux data measured by DAMPE, CALET, and AMS-02.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45893496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 2
Gravitational Instability of Gas–Dust Circumnuclear Disks in Galaxies 星系中气体-尘埃环核盘的引力不稳定性
IF 2.5
Galaxies Pub Date : 2023-03-07 DOI: 10.3390/galaxies11020041
R. Tkachenko, V. Korchagin, B. Jmailov
{"title":"Gravitational Instability of Gas–Dust Circumnuclear Disks in Galaxies","authors":"R. Tkachenko, V. Korchagin, B. Jmailov","doi":"10.3390/galaxies11020041","DOIUrl":"https://doi.org/10.3390/galaxies11020041","url":null,"abstract":"We numerically study the origin of the multi-armed spiral structure observed in the circumnuclear gaseous mini-disks of nearby galaxies. We show that the presence of dust in such disks and its interaction with the gravitationally stable gaseous component leads to the development of a multi-armed spiral structure. As a particular example, we study the formation of the multi-armed spiral pattern in the mini-disk of the galaxy NGC 4736, for which the observational data for the rotation and the density distribution are available. We find that the multi-armed spiral structure grows in the stable gaseous mini-disk of NGC 4736 if the gas-to-dust ratio is about 5–20 percent. We also demonstrate that together with the dust concentration, the important factor for the development of instability is the size of the dust grains. A nonlinear multi-armed spiral pattern develops in the stable gaseous disk with sizes of grains larger than one micron. If future observations confirm the presence of a large amount of dust in the mini-disks of galaxies, this will pinpoint the mechanism of the formation of the multi-armed spiral structure in them.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43747715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
High-Frequency and High-Resolution VLBI Observations of GHz Peaked Spectrum Objects GHz峰值谱目标的高频高分辨率VLBI观测
IF 2.5
Galaxies Pub Date : 2023-03-06 DOI: 10.3390/galaxies11020042
Xiaopeng Cheng, T. An, Ailing Wang, S. Jaiswal
{"title":"High-Frequency and High-Resolution VLBI Observations of GHz Peaked Spectrum Objects","authors":"Xiaopeng Cheng, T. An, Ailing Wang, S. Jaiswal","doi":"10.3390/galaxies11020042","DOIUrl":"https://doi.org/10.3390/galaxies11020042","url":null,"abstract":"Observational studies of GHz peaked spectrum (GPS) sources contribute to the understanding of the radiative properties and interstellar environment of host galaxies. We present the results from the multi-frequency high-resolution VLBI observations of a sample of nine GPS sources at 8, 15, and 43 GHz. All sources show core-jet structure. Four sources show relativistic jets with Doppler boosting factors ranging from 2.0 to 5.0 and a jet viewing angle between 10° and 30°. The core brightness temperatures of the other five sources are below the equipartition brightness temperature limit with their jet viewing angles in the range of 13.6° to 71.9°, which are systematically larger than those of relativistic jets in this sample. The sources show diverse variability properties, with variability levels ranging from 0.11 to 0.56. The measured turnover frequency in the radio spectrum ranges from 6.2 and 31.8 GHz (in the source’s rest frame). We estimate the equipartition magnetic field strength to be between 9 and 48 mG. These results strongly support the notion that these GPS sources are young radio sources in the very early stage of their evolution.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41822148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Magnetism in High-Mass Stars 高质量恒星的磁性
IF 2.5
Galaxies Pub Date : 2023-03-05 DOI: 10.3390/galaxies11020040
Z. Keszthelyi
{"title":"Magnetism in High-Mass Stars","authors":"Z. Keszthelyi","doi":"10.3390/galaxies11020040","DOIUrl":"https://doi.org/10.3390/galaxies11020040","url":null,"abstract":"Magnetism is a ubiquitous property of astrophysical plasmas, yet stellar magnetism still remains far from being completely understood. In this review, we describe recent observational and modelling efforts and progress to expand our knowledge of the magnetic properties of high-mass stars. Several mechanisms (magneto-convection, mass-loss quenching, internal angular momentum transport, and magnetic braking) have significant implications for stellar evolution, populations, and end-products. Consequently, it remains an urgent issue to address and resolve open questions related to magnetism in high-mass stars.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44619396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 1
Hydrodynamic Simulations of a Relativistic Jet Interacting with the Intracluster Medium: Application to Cygnus A 相对射流与星系团内介质相互作用的流体动力学模拟:在天鹅座a中的应用
IF 2.5
Galaxies Pub Date : 2023-03-04 DOI: 10.3390/galaxies11020051
J. Zuhone, P. Nulsen, Po-Hsun Tseng, Hsi-Yu Schive, T. Jones
{"title":"Hydrodynamic Simulations of a Relativistic Jet Interacting with the Intracluster Medium: Application to Cygnus A","authors":"J. Zuhone, P. Nulsen, Po-Hsun Tseng, Hsi-Yu Schive, T. Jones","doi":"10.3390/galaxies11020051","DOIUrl":"https://doi.org/10.3390/galaxies11020051","url":null,"abstract":"The Fanaroff–Riley Class II radio galaxy Cygnus A hosts jets that produce radio emission, X-ray cavities, cocoon shocks, and X-ray hotspots, where the jet interacts with the ICM. Surrounding one hotspot is a peculiar “hole” feature, which appears as a deficit in X-ray emission. We used relativistic hydrodynamic simulations of a collimated jet interacting with an inclined interface between lobe and cluster plasma to model the basic processes that may lead to such a feature. We found that the jet reflects off of the interface into a broad, turbulent flow back out into the lobe, which is dominated by gas stripped from the interface at first and from the intracluster medium itself at later times. We produced simple models of X-ray emission from the ICM, the hotspot, and the reflected jet to show that a hole of emission surrounding the hotspot as seen in Cygnus A may be produced by Doppler de-boosting of the emission from the reflected jet, as seen by an observer with a sight line nearly along the axis of the outgoing material.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45940743","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Super-Resolved Image of M87 Observed with East Asian VLBI Network 东亚VLBI网络观测M87的超分辨图像
IF 2.5
Galaxies Pub Date : 2023-02-28 DOI: 10.3390/galaxies11020039
F. Tazaki, Yuzhu Cui, K. Hada, M. Kino, I. Cho, Guangyao Zhao, K. Akiyama, Y. Mizuno, H. Ro, M. Honma, R. Lu, Zhi-qiang Shen, L. Cui, Y. Yonekura
{"title":"Super-Resolved Image of M87 Observed with East Asian VLBI Network","authors":"F. Tazaki, Yuzhu Cui, K. Hada, M. Kino, I. Cho, Guangyao Zhao, K. Akiyama, Y. Mizuno, H. Ro, M. Honma, R. Lu, Zhi-qiang Shen, L. Cui, Y. Yonekura","doi":"10.3390/galaxies11020039","DOIUrl":"https://doi.org/10.3390/galaxies11020039","url":null,"abstract":"Obtaining high-resolution images at centimeter-or-longer wavelengths is vital for understanding the physics of jets. We reconstructed images from the M87 22 GHz data observed with the East Asian VLBI Network (EAVN) by using the regularized maximum likelihood (RML) method, which is different from the conventional imaging method CLEAN. Consequently, a bright core and jet extending about 30 mas to the northwest were detected with a higher resolution than in the CLEAN image. The width of the jet was 0.5 mas at 0.3 mas from the core, consistent with the width measured in the 86 GHz image in the previous study. In addition, three ridges were able to be detected at around 8 mas from the core, even though the peak-to-peak separation was only 1.0 mas. This indicates that the RML image’s spatial resolution is at least 30% higher than that of the CLEAN image. This study is an important step for future multi-frequency and high-cadence observations of the EAVN to discuss the more detailed structure of the jet and its time variability.","PeriodicalId":37570,"journal":{"name":"Galaxies","volume":" ","pages":""},"PeriodicalIF":2.5,"publicationDate":"2023-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44263786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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