Vineet Rawat, M R Samal, D L Walker, D K Ojha, A Tej, A Zavagno, C P Zhang, Davide Elia, S Dutta, J Jose, C Eswaraiah, E Sharma
Filamentary flows toward the centre of molecular clouds have been recognized as a crucial process in the formation and evolution of stellar clusters. In this paper, we present a comprehensive observational study that investigates the gas properties and kinematics of the Giant Molecular Cloud G148.24+00.41 using the observations of CO (1-0) isotopologues. We find that the cloud is massive (105 M⊙) and is one of the most massive clouds of the outer Galaxy. We identified six likely velocity coherent filaments in the cloud having length, width, and mass in the range of 14−38 pc, 2.5−4.2 pc, and (1.3−6.9) × 103 M⊙, respectively. We find that the filaments are converging towards the central area of the cloud, and the longitudinal accretion flows along the filaments are in the range of ∼ 26−264 M⊙ Myr−1. The cloud has fragmented into 7 clumps having mass in the range of ∼ 260−2100 M⊙ and average size around ∼ 1.4 pc, out of which the most massive clump is located at the hub of the filamentary structures, near the geometric centre of the cloud. Three filaments are found to be directly connected to the massive clump and transferring matter at a rate of ∼ 675 M⊙ Myr−1. The clump hosts a near-infrared cluster. Our results show that large-scale filamentary accretion flows towards the central region of the collapsing cloud is an important mechanism for supplying the matter necessary to form the central high-mass clump and subsequent stellar cluster.
{"title":"The Giant Molecular Cloud G148.24+00.41: Gas Properties, Kinematics, and Cluster Formation at the Nexus of Filamentary Flows","authors":"Vineet Rawat, M R Samal, D L Walker, D K Ojha, A Tej, A Zavagno, C P Zhang, Davide Elia, S Dutta, J Jose, C Eswaraiah, E Sharma","doi":"10.1093/mnras/stae060","DOIUrl":"https://doi.org/10.1093/mnras/stae060","url":null,"abstract":"Filamentary flows toward the centre of molecular clouds have been recognized as a crucial process in the formation and evolution of stellar clusters. In this paper, we present a comprehensive observational study that investigates the gas properties and kinematics of the Giant Molecular Cloud G148.24+00.41 using the observations of CO (1-0) isotopologues. We find that the cloud is massive (105 M⊙) and is one of the most massive clouds of the outer Galaxy. We identified six likely velocity coherent filaments in the cloud having length, width, and mass in the range of 14−38 pc, 2.5−4.2 pc, and (1.3−6.9) × 103 M⊙, respectively. We find that the filaments are converging towards the central area of the cloud, and the longitudinal accretion flows along the filaments are in the range of ∼ 26−264 M⊙ Myr−1. The cloud has fragmented into 7 clumps having mass in the range of ∼ 260−2100 M⊙ and average size around ∼ 1.4 pc, out of which the most massive clump is located at the hub of the filamentary structures, near the geometric centre of the cloud. Three filaments are found to be directly connected to the massive clump and transferring matter at a rate of ∼ 675 M⊙ Myr−1. The clump hosts a near-infrared cluster. Our results show that large-scale filamentary accretion flows towards the central region of the collapsing cloud is an important mechanism for supplying the matter necessary to form the central high-mass clump and subsequent stellar cluster.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"21 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139413850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Luke Chamandy, Jonathan Carroll-Nellenback, Eric G Blackman, Adam Frank, Yisheng Tu, Baowei Liu, Yangyuxin Zou, Jason Nordhaus
We perform 3D hydrodynamical simulations to study recombination and ionization during the common envelope (CE) phase of binary evolution, and develop techniques to track the ionic transitions in time and space. We simulate the interaction of a 2 M⊙ red giant branch primary and a 1 M⊙ companion modeled as a particle. We compare a run employing a tabulated equation of state (EOS) that accounts for ionization and recombination, with a run employing an ideal gas EOS. During the first half of the simulations, ∼15 per cent more mass is unbound in the tabulated EOS run due to the release of recombination energy, but by simulation end the difference has become negligible. We explain this as being a consequence of (i) the tabulated EOS run experiences a shallower inspiral and hence smaller orbital energy release at late times because recombination energy release expands the envelope and reduces drag, and (ii) collision and mixing between expanding envelope gas, ejecta and circumstellar ambient gas assists in unbinding the envelope, but does so less efficiently in the tabulated EOS run where some of the energy transferred to bound envelope gas is used for ionization. The rate of mass unbinding is approximately constant in the last half of the simulations and the orbital separation steadily decreases at late times. A simple linear extrapolation predicts a CE phase duration of ∼2yr, after which the envelope would be unbound.
我们进行了三维流体力学模拟，以研究双星演化的共包层（CE）阶段的重组和电离，并开发了在时间和空间上跟踪离子转变的技术。我们模拟了一个 2 M⊙ 红巨分支主星和一个 1 M⊙ 伴星的相互作用，伴星被模拟为一个粒子。我们比较了采用表列状态方程（EOS）和理想气体状态方程（EOS）的运行情况，前者考虑了电离和重组。在模拟的前半部分，由于重组能量的释放，表列状态方程运行中未被束缚的质量比理想气体运行多出 15%，但到模拟结束时，两者之间的差异已经可以忽略不计。我们将此解释为以下原因造成的：(i) 表中的 EOS 运行经历了较浅的吸气，因此在后期释放的轨道能量较小，因为重组能量的释放使包层膨胀并减少了阻力；(ii) 膨胀的包层气体、抛射物和星周环境气体之间的碰撞和混合有助于解除包层的束缚，但在表中的 EOS 运行中，这种作用的效率较低，因为转移到束缚包层气体的部分能量被用于电离。在模拟的后半段，质量解除束缚的速率近似恒定，轨道分离度在后期稳步下降。根据简单的线性推断，CE阶段的持续时间为2年，之后包层将被解除束缚。
{"title":"How negative feedback and the ambient environment limit the influence of recombination in common envelope evolution","authors":"Luke Chamandy, Jonathan Carroll-Nellenback, Eric G Blackman, Adam Frank, Yisheng Tu, Baowei Liu, Yangyuxin Zou, Jason Nordhaus","doi":"10.1093/mnras/stae036","DOIUrl":"https://doi.org/10.1093/mnras/stae036","url":null,"abstract":"We perform 3D hydrodynamical simulations to study recombination and ionization during the common envelope (CE) phase of binary evolution, and develop techniques to track the ionic transitions in time and space. We simulate the interaction of a 2 M⊙ red giant branch primary and a 1 M⊙ companion modeled as a particle. We compare a run employing a tabulated equation of state (EOS) that accounts for ionization and recombination, with a run employing an ideal gas EOS. During the first half of the simulations, ∼15 per cent more mass is unbound in the tabulated EOS run due to the release of recombination energy, but by simulation end the difference has become negligible. We explain this as being a consequence of (i) the tabulated EOS run experiences a shallower inspiral and hence smaller orbital energy release at late times because recombination energy release expands the envelope and reduces drag, and (ii) collision and mixing between expanding envelope gas, ejecta and circumstellar ambient gas assists in unbinding the envelope, but does so less efficiently in the tabulated EOS run where some of the energy transferred to bound envelope gas is used for ionization. The rate of mass unbinding is approximately constant in the last half of the simulations and the orbital separation steadily decreases at late times. A simple linear extrapolation predicts a CE phase duration of ∼2yr, after which the envelope would be unbound.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"239 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139413795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vineet Rawat, M R Samal, Chakali Eswaraiah, Jia-Wei Wang, Davide Elia, Sandhyarani Panigrahy, A Zavagno, R K Yadav, D L Walker, J Jose, D K Ojha, C P Zhang, S Dutta
The relative importance of magnetic fields, turbulence, and gravity in the early phases of star formation is still not well understood. We report the first high-resolution dust polarization observations at 850 μm around the most massive clump, located at the hub of the Giant Molecular Cloud G148.24+00.41, using SCUBA-2/POL-2 at the James Clerk Maxwell Telescope. We find that the degree of polarization decreases steadily towards the denser portion of the cloud. Comparing the intensity gradients and local gravity with the magnetic field orientations, we find that local gravity plays a dominant role in driving the gas collapse as the magnetic field orientations and gravity vectors seem to point towards the dense clumps. We also find evidence of U-shaped magnetic field morphology towards a small-scale elongated structure associated with the central clump, hinting at converging accretion flows towards the clump. Our observation has resolved the massive clump into multiple substructures. We study the magnetic field properties of two regions, central clump (CC) and northeastern elongated structure (NES). Using the modified Davis-Chandrasekhar-Fermi method, we determine that the magnetic field strengths of CC and NES are ∼24.0 ± 6.0 μG and 20.0 ± 5.0 μG, respectively. The mass-to-flux ratios are found to be magnetically transcritical/supercritical, while the Alfv$acute{text{e}}$n Mach number indicates a trans-Alfv$acute{text{e}}$nic state in both regions. These results, along with Virial analysis, suggest that at the hub of G148.24+00.41, gravitational energy has an edge over magnetic and kinetic energies.
磁场、湍流和引力在恒星形成早期阶段的相对重要性还没有得到很好的理解。我们利用詹姆斯-克拉克-麦克斯韦望远镜（James Clerk Maxwell Telescope）的SCUBA-2/POL-2，首次在位于巨分子云G148.24+00.41中心的最大质量团块周围进行了850微米的高分辨率尘埃极化观测。我们发现，偏振程度在向云的高密度部分逐渐减弱。将强度梯度和当地引力与磁场方向进行比较，我们发现当地引力在驱动气体塌缩方面起着主导作用，因为磁场方向和引力矢量似乎都指向高密度团块。我们还发现了与中心团块相关的小尺度拉长结构的 U 形磁场形态证据，暗示着向团块汇聚的吸积流。我们的观测将大质量星团解析为多个子结构。我们研究了中央团块（CC）和东北拉长结构（NES）这两个区域的磁场特性。利用改进的 Davis-Chandrasekhar-Fermi 方法，我们确定 CC 和 NES 的磁场强度分别为 ∼24.0 ± 6.0 μG 和 20.0 ± 5.0 μG。质量流量比被认为是跨临界/超临界磁场，而 Alfv$acute{text{e}$n 马赫数则表明这两个区域都处于跨 Alfv$acute{text{e}$nic 状态。这些结果以及室温分析表明，在G148.24+00.41的枢纽处，引力能比磁能和动能更有优势。
{"title":"Understanding the relative importance of magnetic field, gravity, and turbulence in star formation at the hub of the giant molecular cloud G148.24+00.41","authors":"Vineet Rawat, M R Samal, Chakali Eswaraiah, Jia-Wei Wang, Davide Elia, Sandhyarani Panigrahy, A Zavagno, R K Yadav, D L Walker, J Jose, D K Ojha, C P Zhang, S Dutta","doi":"10.1093/mnras/stae053","DOIUrl":"https://doi.org/10.1093/mnras/stae053","url":null,"abstract":"The relative importance of magnetic fields, turbulence, and gravity in the early phases of star formation is still not well understood. We report the first high-resolution dust polarization observations at 850 μm around the most massive clump, located at the hub of the Giant Molecular Cloud G148.24+00.41, using SCUBA-2/POL-2 at the James Clerk Maxwell Telescope. We find that the degree of polarization decreases steadily towards the denser portion of the cloud. Comparing the intensity gradients and local gravity with the magnetic field orientations, we find that local gravity plays a dominant role in driving the gas collapse as the magnetic field orientations and gravity vectors seem to point towards the dense clumps. We also find evidence of U-shaped magnetic field morphology towards a small-scale elongated structure associated with the central clump, hinting at converging accretion flows towards the clump. Our observation has resolved the massive clump into multiple substructures. We study the magnetic field properties of two regions, central clump (CC) and northeastern elongated structure (NES). Using the modified Davis-Chandrasekhar-Fermi method, we determine that the magnetic field strengths of CC and NES are ∼24.0 ± 6.0 μG and 20.0 ± 5.0 μG, respectively. The mass-to-flux ratios are found to be magnetically transcritical/supercritical, while the Alfv$acute{text{e}}$n Mach number indicates a trans-Alfv$acute{text{e}}$nic state in both regions. These results, along with Virial analysis, suggest that at the hub of G148.24+00.41, gravitational energy has an edge over magnetic and kinetic energies.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"39 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139413852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It has recently been suggested that black holes (BHs) may grow with time, so that their mass is proportional to the cosmological scale factor to the power n, with suggested values n ≈ 3 for supermassive BHs in elliptical galaxies. Here we test these predictions with stellar mass BHs in X-ray binaries using their masses and ages. We perform two sets of tests to assess the compatible values of n. First, we assume that no compact object grows over the Tolman-Oppenheimer-Volkof limit which marks the borderline between neutron stars and BHs. We show that half of BHs would be born with a mass below this limit if n = 3 applies. The possibility that all BHs were born above the limit is rejected at 4 σ if n = 3 applies. In the second test, we assume that masses of BHs at their formation stay the same over cosmic history. We compare the mass distribution of the youngest BHs, which could have not grown yet, to their older counterparts. Distributions are compatible for $n = -0.9^{+1.3}_{-4.6}$, with n = 3 excluded formally with 87% confidence. This result may be biased, because massive BHs tend to have a massive companion. Correcting for this bias yields n ≈ 0. We can therefore conclude that while our results are not a clear rejection of BH scaling with n = 3, we show that n = 0 is much more consistent with the data.
最近有人提出，黑洞（BHs）可能会随着时间的推移而增长，因此它们的质量与宇宙尺度因子的幂 n 成正比，对于椭圆星系中的超大质量黑洞，建议值 n ≈ 3。在这里，我们用X射线双星中恒星质量的BH的质量和年龄来检验这些预测。我们进行了两组测试来评估n的兼容值。首先，我们假定没有紧凑的天体生长超过托尔曼-奥本海默-沃尔科夫极限（Tolman-Oppenheimer-Volkof limit），该极限标志着中子星和BHs之间的边界。我们的研究表明，如果 n = 3 适用，一半的 BHs 在诞生时的质量会低于这个极限。如果 n = 3 适用，在 4 σ 时，所有诞生的 BH 都高于极限的可能性被否定。在第二个测试中，我们假定在整个宇宙历史中，BH 形成时的质量保持不变。我们将可能尚未长大的最年轻的黑体的质量分布与它们较老的质量分布进行比较。在n=-0.9^{+1.3}_{-4.6}$时，两者的质量分布是一致的，其中n=3被正式排除在外，置信度为87%。这个结果可能是有偏差的，因为大质量的黑体往往有一个大质量的伴星。因此，我们可以得出结论，虽然我们的结果并没有明确地否定n = 3的BH缩放，但我们表明n = 0与数据更为一致。
{"title":"Determining cosmological growth parameter for stellar - mass black holes","authors":"Ema Mlinar, Tomaž Zwitter","doi":"10.1093/mnras/stae059","DOIUrl":"https://doi.org/10.1093/mnras/stae059","url":null,"abstract":"It has recently been suggested that black holes (BHs) may grow with time, so that their mass is proportional to the cosmological scale factor to the power n, with suggested values n ≈ 3 for supermassive BHs in elliptical galaxies. Here we test these predictions with stellar mass BHs in X-ray binaries using their masses and ages. We perform two sets of tests to assess the compatible values of n. First, we assume that no compact object grows over the Tolman-Oppenheimer-Volkof limit which marks the borderline between neutron stars and BHs. We show that half of BHs would be born with a mass below this limit if n = 3 applies. The possibility that all BHs were born above the limit is rejected at 4 σ if n = 3 applies. In the second test, we assume that masses of BHs at their formation stay the same over cosmic history. We compare the mass distribution of the youngest BHs, which could have not grown yet, to their older counterparts. Distributions are compatible for $n = -0.9^{+1.3}_{-4.6}$, with n = 3 excluded formally with 87% confidence. This result may be biased, because massive BHs tend to have a massive companion. Correcting for this bias yields n ≈ 0. We can therefore conclude that while our results are not a clear rejection of BH scaling with n = 3, we show that n = 0 is much more consistent with the data.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"54 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139413793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xianyu Tan, Thaddeus D Komacek, Natasha E Batalha, Drake Deming, Roxana Lupu, Vivien Parmentier, Raymond T Pierrehumbert
Ultra-hot Jupiters (UHJs) are natural laboratories to study extreme physics in planetary atmospheres and their rich observational data sets are yet to be confronted with models with varying complexities at a population level. In this work, we update the general circulation model of Tan & Komacek (2019) to include a non-grey radiative transfer scheme and apply it to simulate the realistic thermal structures, phase-dependent spectra, and wavelength-dependent phase curves of UHJs. We performed grids of models over a large range of equilibrium temperatures and rotation periods for varying assumptions, showing that the fractional day-night brightness temperature differences remain almost constant or slightly increase with increasing equilibrium temperature from the visible to mid-infrared wavelengths. This differs from previous work primarily due to the increasing planetary rotation rate with increasing equilibrium temperature for fixed host star type. Radiative effects of varying atmospheric compositions become more significant in dayside brightness temperature in longer wavelengths. Data-model comparisons of dayside brightness temperatures and phase curve amplitudes as a function of equilibrium temperature are in broad agreement. Observations show a large scatter compared to models even with a range of different assumptions, indicating significantly varying intrinsic properties in the hot Jupiter population. Our cloud-free models generally struggle to match all observations for individual targets with a single set of parameter choices, indicating the need for extra processes for understanding the heat transport of UHJs.
超热木星（UHJs）是研究行星大气中极端物理学的天然实验室，其丰富的观测数据集还有待于在群体水平上用不同复杂程度的模型来面对。在这项工作中，我们更新了 Tan & Komacek（2019）的大气环流模型，加入了非灰色辐射传递方案，并将其用于模拟 UHJs 的现实热结构、相位相关光谱和波长相关相位曲线。我们在很大的平衡温度和旋转周期范围内对不同假设条件下的模型进行了网格计算，结果表明，从可见光到中红外波段，随着平衡温度的升高，昼夜亮度温差分数几乎保持不变或略有增加。这与以往的研究不同，主要是因为在固定的主星类型下，随着平衡温度的升高，行星自转速率也在增加。在较长的波长中，不同大气成分的辐射效应对日侧亮度温度的影响更加显著。作为平衡温度函数的日侧亮度温度和相位曲线振幅的数据与模型比较结果基本一致。即使在一系列不同的假设条件下，观测结果与模型相比也有很大的差异，这表明热木星群的内在性质有很大的不同。我们的无云模型通常很难在选择一组参数的情况下与单个目标的所有观测结果相匹配，这表明需要额外的过程来理解超高质量木星的热传输。
{"title":"Modeling the day-night temperature variations of ultra-hot Jupiters: confronting non-grey general circulation models and observations","authors":"Xianyu Tan, Thaddeus D Komacek, Natasha E Batalha, Drake Deming, Roxana Lupu, Vivien Parmentier, Raymond T Pierrehumbert","doi":"10.1093/mnras/stae050","DOIUrl":"https://doi.org/10.1093/mnras/stae050","url":null,"abstract":"Ultra-hot Jupiters (UHJs) are natural laboratories to study extreme physics in planetary atmospheres and their rich observational data sets are yet to be confronted with models with varying complexities at a population level. In this work, we update the general circulation model of Tan & Komacek (2019) to include a non-grey radiative transfer scheme and apply it to simulate the realistic thermal structures, phase-dependent spectra, and wavelength-dependent phase curves of UHJs. We performed grids of models over a large range of equilibrium temperatures and rotation periods for varying assumptions, showing that the fractional day-night brightness temperature differences remain almost constant or slightly increase with increasing equilibrium temperature from the visible to mid-infrared wavelengths. This differs from previous work primarily due to the increasing planetary rotation rate with increasing equilibrium temperature for fixed host star type. Radiative effects of varying atmospheric compositions become more significant in dayside brightness temperature in longer wavelengths. Data-model comparisons of dayside brightness temperatures and phase curve amplitudes as a function of equilibrium temperature are in broad agreement. Observations show a large scatter compared to models even with a range of different assumptions, indicating significantly varying intrinsic properties in the hot Jupiter population. Our cloud-free models generally struggle to match all observations for individual targets with a single set of parameter choices, indicating the need for extra processes for understanding the heat transport of UHJs.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"79 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139415342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Studies of the dynamics of globular clusters assume different values of bar parameters (mass, velocity, size) and analyse the results of orbit classifications over the range of the chosen values. It is also a usual thing that a spherical bulge component is converted into the bar to obtain a non-axisymmetric potential from an axisymmetric one. The choice of bar parameters and the way the bar is converted from the bulge introduce systematics into the orbit classifications that we explore in the present study. We integrate orbits of 30 bulge globular clusters residing in the inner area of the Galaxy (R ≲ 5 kpc) backwards in time for three different potentials, two of which are obtained by fitting the rotation curve, and one is taken from the surrogate N-body model representing our Galaxy. We analyse each orbit in terms of dominant frequencies obtained from its coordinate spectra. We find that the bar pattern speed is a key factor in orbital classification. With an increase of it, frequencies deviate more and more from the “bar” frequency ratio 2:1. The bar-to-bulge mass ratio (assuming the total mass of the bar plus the bulge is fixed) and size of the bar play a smaller role. We also find that, in the N-body potential, the fraction of orbits that follow the bar is higher than in those obtained from fitting the rotation curve.
{"title":"Globular clusters and bar: captured or not captured?","authors":"Anton A Smirnov, Anisa T Bajkova, Vadim V Bobylev","doi":"10.1093/mnras/stae029","DOIUrl":"https://doi.org/10.1093/mnras/stae029","url":null,"abstract":"Studies of the dynamics of globular clusters assume different values of bar parameters (mass, velocity, size) and analyse the results of orbit classifications over the range of the chosen values. It is also a usual thing that a spherical bulge component is converted into the bar to obtain a non-axisymmetric potential from an axisymmetric one. The choice of bar parameters and the way the bar is converted from the bulge introduce systematics into the orbit classifications that we explore in the present study. We integrate orbits of 30 bulge globular clusters residing in the inner area of the Galaxy (R ≲ 5 kpc) backwards in time for three different potentials, two of which are obtained by fitting the rotation curve, and one is taken from the surrogate N-body model representing our Galaxy. We analyse each orbit in terms of dominant frequencies obtained from its coordinate spectra. We find that the bar pattern speed is a key factor in orbital classification. With an increase of it, frequencies deviate more and more from the “bar” frequency ratio 2:1. The bar-to-bulge mass ratio (assuming the total mass of the bar plus the bulge is fixed) and size of the bar play a smaller role. We also find that, in the N-body potential, the fraction of orbits that follow the bar is higher than in those obtained from fitting the rotation curve.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"10 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139398709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We probe the small-scale absorption line variability using absorption depth based analysis of a sample of 64 ultra fast outflow (UFO) C iv broad absorption line (BAL) quasars monitored using the Southern African Large Telescope. We confirm the strong monotonic increase in the strength of variability with increasing outflow velocity. We identify regions inside the BAL trough for each source where the normalized flux difference between two epochs is >0.1 for a velocity width ≥500 km s−1(called ‘variable regions’). We find the total number of variable regions increases with the time interval probed and the number of BALs showing variable regions almost doubles from short (<2 yrs) to long (>2 yrs) time scales. We study the distributions of variable region properties such as its velocity width, depth, and location. These regions typically occupy a few-tenths of the entire width of the BAL. Their widths are found to increase with increasing time scales having typical widths of ∼ 2000 km s−1 for Δt > 2 yr. However, their absolute velocity with respect to zem and their relative position within the BAL profile remain random irrespective of the time scale probed. The equivalent width variations of the BALs are strongly dependent on the size and depth of the variable regions but are little dependent on their total number. Finally, we find that ∼17% of the UFO BALs show uncorrelated variability within the BAL trough.
我们对利用南部非洲大型望远镜监测到的 64 个超快外流（UFO）C iv 宽吸收线（BAL）类星体样本进行了基于吸收深度的分析，从而探究了小尺度吸收线的可变性。我们证实，随着外流速度的增加，变异性的强度也会出现强烈的单调增加。我们确定了每个源的宽吸收线槽内，在速度宽度≥500 km s-1时，两个纪元之间的归一化通量差为>0.1的区域（称为 "可变区域"）。我们发现变区的总数随着探测时间间隔的增加而增加，从短（<2 年）时间尺度到长（>2 年）时间尺度，显示变区的 BALs 数量几乎增加了一倍。我们研究了变区属性的分布，如速度宽度、深度和位置。这些区域通常占整个 BAL 宽度的几十分之一。然而，无论探测的时间尺度如何，它们相对于zem的绝对速度及其在BAL剖面中的相对位置仍然是随机的。BALs的等效宽度变化与变区的大小和深度有很大关系，但与变区的总数关系不大。最后，我们发现有 17%的 UFO BALs 在 BAL 波谷内显示出不相关的变化。
{"title":"Time variability of ultra-fast BAL outflows using SALT: C iv absorption depth based analysis","authors":"P Aromal, R Srianand, P Petitjean","doi":"10.1093/mnras/stae018","DOIUrl":"https://doi.org/10.1093/mnras/stae018","url":null,"abstract":"We probe the small-scale absorption line variability using absorption depth based analysis of a sample of 64 ultra fast outflow (UFO) C iv broad absorption line (BAL) quasars monitored using the Southern African Large Telescope. We confirm the strong monotonic increase in the strength of variability with increasing outflow velocity. We identify regions inside the BAL trough for each source where the normalized flux difference between two epochs is &gt;0.1 for a velocity width ≥500 km s−1(called ‘variable regions’). We find the total number of variable regions increases with the time interval probed and the number of BALs showing variable regions almost doubles from short (&lt;2 yrs) to long (&gt;2 yrs) time scales. We study the distributions of variable region properties such as its velocity width, depth, and location. These regions typically occupy a few-tenths of the entire width of the BAL. Their widths are found to increase with increasing time scales having typical widths of ∼ 2000 km s−1 for Δt &gt; 2 yr. However, their absolute velocity with respect to zem and their relative position within the BAL profile remain random irrespective of the time scale probed. The equivalent width variations of the BALs are strongly dependent on the size and depth of the variable regions but are little dependent on their total number. Finally, we find that ∼17% of the UFO BALs show uncorrelated variability within the BAL trough.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"107 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139396601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gopal Bhatta, Sarvesh Gharat, Abhimanyu Borthakur, Aman Kumar
Machine learning has emerged as a powerful tool in the field of gamma-ray astrophysics. The algorithms can distinguish between different source types, such as blazars and pulsars, and help uncover new insights into the high-energy universe. The Large Area Telescope on-board the Fermi Gamma-ray telescope has significantly advanced our understanding of the Universe. The instrument has detected a large number of gamma-ray emitting sources, among which a significant number of objects have been identified as active galactic nuclei. The sample is primarily composed of blazars; however, more than one-third of these sources are either of an unknown class or lack a definite association with a low-energy counterpart. In this work, we employ multiple machine learning algorithms to classify the sources based on their other physical properties. In particular, we utilized smart initialisation techniques and self-supervised learning for classifying blazars into BL Lacertae objects (BL Lac, also BLL) and flat spectrum radio quasars (FSRQ). The core advantage of the algorithm is its simplicity, usage of minimum number of features and easy deployment due to lesser number of parameters without compromising on the performance along with increase in inference speed (at least 7 times more than existing algorithms). As a result, the best performing model is deployed on multiple platforms so that any user irrespective of their coding background can use the tool. The model predicts that out of the 1115 sources of uncertain type in the 4FGL-DR3 catalog, 820 can be classified as BL Lacs, and 295 can be classified as FSRQs.
{"title":"Gamma-ray Blazar Classification using Machine Learning with Advanced Weight Initialization and Self-Supervised Learning Techniques","authors":"Gopal Bhatta, Sarvesh Gharat, Abhimanyu Borthakur, Aman Kumar","doi":"10.1093/mnras/stae028","DOIUrl":"https://doi.org/10.1093/mnras/stae028","url":null,"abstract":"Machine learning has emerged as a powerful tool in the field of gamma-ray astrophysics. The algorithms can distinguish between different source types, such as blazars and pulsars, and help uncover new insights into the high-energy universe. The Large Area Telescope on-board the Fermi Gamma-ray telescope has significantly advanced our understanding of the Universe. The instrument has detected a large number of gamma-ray emitting sources, among which a significant number of objects have been identified as active galactic nuclei. The sample is primarily composed of blazars; however, more than one-third of these sources are either of an unknown class or lack a definite association with a low-energy counterpart. In this work, we employ multiple machine learning algorithms to classify the sources based on their other physical properties. In particular, we utilized smart initialisation techniques and self-supervised learning for classifying blazars into BL Lacertae objects (BL Lac, also BLL) and flat spectrum radio quasars (FSRQ). The core advantage of the algorithm is its simplicity, usage of minimum number of features and easy deployment due to lesser number of parameters without compromising on the performance along with increase in inference speed (at least 7 times more than existing algorithms). As a result, the best performing model is deployed on multiple platforms so that any user irrespective of their coding background can use the tool. The model predicts that out of the 1115 sources of uncertain type in the 4FGL-DR3 catalog, 820 can be classified as BL Lacs, and 295 can be classified as FSRQs.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"22 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139396356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Richard Anantua, Angelo Ricarte, George Wong, Razieh Emami, Roger Blandford, Lani Oramas, Hayley West, Joaquin Duran, Brandon Curd
Horizon-scale observations of the jetted active galactic nucleus M87 are compared with simulations spanning a broad range of dissipation mechanisms and plasma content in three-dimensional general relativistic flows around spinning black holes. Observations of synchrotron radiation from radio to X-ray frequencies can be compared with simulations by adding prescriptions specifying the relativistic electron-plus-positron distribution function and associated radiative transfer coefficients. A suite of time-varying simulations with various spins, plasma magnetizations and turbulent heating and equipartition-based emission prescriptions (and piecewise combinations thereof) is chosen to represent distinct possibilities for the M87 jet/accretion flow/black hole (JAB) system. Simulation jet morphology, polarization and variation are then ‘observed’ and compared with real observations to infer the rules that govern the polarized emissivity. Our models support several possible spin/emission model/plasma composition combinations supplying the jet in M87, whose black hole shadow has been observed down to the photon ring at 230 GHz by the Event Horizon Telescope (EHT). Net linear polarization and circular polarization constraints favor magnetically arrested disk (MAD) models whereas resolved linear polarization favors standard and normal evolution (SANE) in our parameter space. We also show that some MAD cases dominated by intrinsic circular polarization have near-linear V/I dependence on un-paired electron or positron content while SANE polarization exhibits markedly greater positron-dependent Faraday effects – future probes of the SANE/MAD dichotomy and plasma content with the EHT. This is the second work in a series also applying the ‘observing’ simulations methodology to near-horizon regions of supermassive black holes in Sgr A* and 3C 279.
{"title":"On the Comparison of AGN with GRMHD Simulations: II. M87","authors":"Richard Anantua, Angelo Ricarte, George Wong, Razieh Emami, Roger Blandford, Lani Oramas, Hayley West, Joaquin Duran, Brandon Curd","doi":"10.1093/mnras/stad3998","DOIUrl":"https://doi.org/10.1093/mnras/stad3998","url":null,"abstract":"Horizon-scale observations of the jetted active galactic nucleus M87 are compared with simulations spanning a broad range of dissipation mechanisms and plasma content in three-dimensional general relativistic flows around spinning black holes. Observations of synchrotron radiation from radio to X-ray frequencies can be compared with simulations by adding prescriptions specifying the relativistic electron-plus-positron distribution function and associated radiative transfer coefficients. A suite of time-varying simulations with various spins, plasma magnetizations and turbulent heating and equipartition-based emission prescriptions (and piecewise combinations thereof) is chosen to represent distinct possibilities for the M87 jet/accretion flow/black hole (JAB) system. Simulation jet morphology, polarization and variation are then ‘observed’ and compared with real observations to infer the rules that govern the polarized emissivity. Our models support several possible spin/emission model/plasma composition combinations supplying the jet in M87, whose black hole shadow has been observed down to the photon ring at 230 GHz by the Event Horizon Telescope (EHT). Net linear polarization and circular polarization constraints favor magnetically arrested disk (MAD) models whereas resolved linear polarization favors standard and normal evolution (SANE) in our parameter space. We also show that some MAD cases dominated by intrinsic circular polarization have near-linear V/I dependence on un-paired electron or positron content while SANE polarization exhibits markedly greater positron-dependent Faraday effects – future probes of the SANE/MAD dichotomy and plasma content with the EHT. This is the second work in a series also applying the ‘observing’ simulations methodology to near-horizon regions of supermassive black holes in Sgr A* and 3C 279.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"27 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139398693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Todor V Veltchev, Philipp Girichidis, Lyubov Marinkova, Sava Donkov, Orlin Stanchev, Ralf S Klessen
We present a numerical study of the evolution of power-law tails (PLTs) in the (column-)density distributions (N-PDF, ρ-PDF) in contracting star-forming clumps in primordial gas, without and with some initial rotational and/or turbulent support. In all considered runs multiple PLTs emerge shortly after the formation of the first protostar. The first PLT (PLT 1) in the ρ-PDF is a stable feature with slope q1 ≃ −1.3 which corresponds – under the condition of preserved spherical symmetry – to the outer envelope of the protostellar object with density profile ρ∝l−2 in the classical Larson-Penston collapse model, where l is the radius. The second PLT (PLT 2) in the ρ-PDF is stable in the pure-infall runs but fluctuates significantly in the runs with initial support against gravity as dozens of protostars form and their mutual tidal forces change the density structure. Its mean slope, 〈q2〉 ≃ −2, corresponds to a density profile of ρ∝l−3/2 which describes a core in free fall in the classical Larson-Penston collapse model or an attractor solution at scales with dominating protostellar gravity. PLT 1 and PLT 2 in the N-PDFs are generally consistent with the observational data of Galactic low-mass star-forming regions from Herschel data. In the runs with initial support against gravity a third PLT (PLT 3) in the ρ-PDFs appears simultaneously with or after the emergence of PLT 2. It is very shallow, with mean slope of 〈q3〉 ≃ −1, and is associated with the formation of thin protostellar accretion disks.
{"title":"Multiple power-law tails in the density and column-density distribution in contracting star-forming clumps","authors":"Todor V Veltchev, Philipp Girichidis, Lyubov Marinkova, Sava Donkov, Orlin Stanchev, Ralf S Klessen","doi":"10.1093/mnras/stae031","DOIUrl":"https://doi.org/10.1093/mnras/stae031","url":null,"abstract":"We present a numerical study of the evolution of power-law tails (PLTs) in the (column-)density distributions (N-PDF, ρ-PDF) in contracting star-forming clumps in primordial gas, without and with some initial rotational and/or turbulent support. In all considered runs multiple PLTs emerge shortly after the formation of the first protostar. The first PLT (PLT 1) in the ρ-PDF is a stable feature with slope q1 ≃ −1.3 which corresponds – under the condition of preserved spherical symmetry – to the outer envelope of the protostellar object with density profile ρ∝l−2 in the classical Larson-Penston collapse model, where l is the radius. The second PLT (PLT 2) in the ρ-PDF is stable in the pure-infall runs but fluctuates significantly in the runs with initial support against gravity as dozens of protostars form and their mutual tidal forces change the density structure. Its mean slope, 〈q2〉 ≃ −2, corresponds to a density profile of ρ∝l−3/2 which describes a core in free fall in the classical Larson-Penston collapse model or an attractor solution at scales with dominating protostellar gravity. PLT 1 and PLT 2 in the N-PDFs are generally consistent with the observational data of Galactic low-mass star-forming regions from Herschel data. In the runs with initial support against gravity a third PLT (PLT 3) in the ρ-PDFs appears simultaneously with or after the emergence of PLT 2. It is very shallow, with mean slope of 〈q3〉 ≃ −1, and is associated with the formation of thin protostellar accretion disks.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"116 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139374423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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