We present an Artificial Neural Network (ANN) model of photospheric lithium depletion in cool stars (3000 < Teff/K < 6500), producing estimates and probability distributions of age from 7Li 6708Å equivalent width (LiEW) and effective temperature data inputs. The model is trained on the same sample of 6200 stars from 52 open clusters, observed in the Gaia-ESO spectroscopic survey, and used to calibrate the previously published analytical eagles model, with ages 2 – 6000 Myr and −0.3 < [Fe/H] <0.2. The additional flexibility of the ANN provides some improvements, including better modelling of the ‘lithium dip’ at ages <50 Myr and Teff ∼ 3500 K, and of the intrinsic dispersion in LiEW at all ages. Poor age discrimination is still an issue at ages > 1 Gyr, confirming that additional modelling flexibility is not sufficient to fully represent the LiEW - age - Teff relationship, and suggesting the involvement of further astrophysical parameters. Expansion to include such parameters – rotation, accretion, and surface gravity – is discussed, and the use of an ANN means these can be more easily included in future iterations, alongside more flexible functional forms for the LiEW dispersion. Our methods and ANN model are provided in an updated version 2.0 of the eagles software.
{"title":"Using Neural Network models to estimate stellar ages from lithium equivalent widths: An EAGLES expansion","authors":"G Weaver, R D Jeffries, R J Jackson","doi":"10.1093/mnras/stae2133","DOIUrl":"https://doi.org/10.1093/mnras/stae2133","url":null,"abstract":"We present an Artificial Neural Network (ANN) model of photospheric lithium depletion in cool stars (3000 &lt; Teff/K &lt; 6500), producing estimates and probability distributions of age from 7Li 6708Å equivalent width (LiEW) and effective temperature data inputs. The model is trained on the same sample of 6200 stars from 52 open clusters, observed in the Gaia-ESO spectroscopic survey, and used to calibrate the previously published analytical eagles model, with ages 2 – 6000 Myr and −0.3 &lt; [Fe/H] &lt;0.2. The additional flexibility of the ANN provides some improvements, including better modelling of the ‘lithium dip’ at ages &lt;50 Myr and Teff ∼ 3500 K, and of the intrinsic dispersion in LiEW at all ages. Poor age discrimination is still an issue at ages &gt; 1 Gyr, confirming that additional modelling flexibility is not sufficient to fully represent the LiEW - age - Teff relationship, and suggesting the involvement of further astrophysical parameters. Expansion to include such parameters – rotation, accretion, and surface gravity – is discussed, and the use of an ANN means these can be more easily included in future iterations, alongside more flexible functional forms for the LiEW dispersion. Our methods and ANN model are provided in an updated version 2.0 of the eagles software.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"12 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256397","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}
Jingyao Dou, Philip J Carter, Simon Lock, Zoë M Leinhardt
Head-on giant impacts (collisions between planet-size bodies) are frequently used to study the planet formation process as they present an extreme configuration where the two colliding bodies are greatly disturbed. With limited computing resources, focusing on these extreme impacts eases the burden of exploring a large parameter space. Results from head-on impacts are often then extended to study oblique impacts with angle corrections or used as initial conditions for other calculations, for example, the evolution of ejected debris. In this study, we conduct a detailed investigation of the thermodynamic and energy budget evolution of high-energy head-on giant impacts, entering the catastrophic impacts regime, for target masses between 0.001 and 12 M⊕. We demonstrate the complex interplay of gravitational forces, shock dynamics, and thermodynamic processing in head-on impacts at high energy. Our study illustrates that frequent interactions of core material with the liquid side of the vapour curve could have cumulative effects on the post-collision remnants, leading to fragmentary disintegration occurring at lower impact energy. This results in the mass of the largest remnant diverging significantly from previously developed scaling laws. These findings suggest two key considerations: 1) head-on planetary collisions for different target masses do not behave similarly, so caution is needed when applying scaling laws across a broad parameter space; 2) an accurate model of the liquid-vapour phase boundary is essential for modeling giant impacts. Our findings highlight the need for careful consideration of impact configurations in planetary formation studies, as head-on impacts involve a complex interplay between thermodynamic processing, shocks, gravitational forces, and other factors.
{"title":"Exploring the Catastrophic Regime: Thermodynamics and Disintegration in Head-On Planetary Collisions","authors":"Jingyao Dou, Philip J Carter, Simon Lock, Zoë M Leinhardt","doi":"10.1093/mnras/stae2134","DOIUrl":"https://doi.org/10.1093/mnras/stae2134","url":null,"abstract":"Head-on giant impacts (collisions between planet-size bodies) are frequently used to study the planet formation process as they present an extreme configuration where the two colliding bodies are greatly disturbed. With limited computing resources, focusing on these extreme impacts eases the burden of exploring a large parameter space. Results from head-on impacts are often then extended to study oblique impacts with angle corrections or used as initial conditions for other calculations, for example, the evolution of ejected debris. In this study, we conduct a detailed investigation of the thermodynamic and energy budget evolution of high-energy head-on giant impacts, entering the catastrophic impacts regime, for target masses between 0.001 and 12 M⊕. We demonstrate the complex interplay of gravitational forces, shock dynamics, and thermodynamic processing in head-on impacts at high energy. Our study illustrates that frequent interactions of core material with the liquid side of the vapour curve could have cumulative effects on the post-collision remnants, leading to fragmentary disintegration occurring at lower impact energy. This results in the mass of the largest remnant diverging significantly from previously developed scaling laws. These findings suggest two key considerations: 1) head-on planetary collisions for different target masses do not behave similarly, so caution is needed when applying scaling laws across a broad parameter space; 2) an accurate model of the liquid-vapour phase boundary is essential for modeling giant impacts. Our findings highlight the need for careful consideration of impact configurations in planetary formation studies, as head-on impacts involve a complex interplay between thermodynamic processing, shocks, gravitational forces, and other factors.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"7 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256398","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}
Arrykrishna Mootoovaloo, Jaime Ruiz-Zapatero, Carlos García-García, David Alonso
We assess the usefulness of gradient-based samplers, such as the No-U-Turn Sampler (${tt NUTS}$), by comparison with traditional Metropolis-Hastings algorithms, in tomographic 3 × 2 point analyses. Specifically, we use the DES Year 1 data and a simulated future LSST-like survey as representative examples of these studies, containing a significant number of nuisance parameters (20 and 32, respectively) that affect the performance of rejection-based samplers. To do so, we implement a differentiable forward model using JAX-COSMO, and we use it to derive parameter constraints from both datasets using the NUTS algorithm implemented in ${tt numpyro}$, and the Metropolis-Hastings algorithm as implemented in Cobaya. When quantified in terms of the number of effective number of samples taken per likelihood evaluation, we find a relative efficiency gain of ${mathcal {O}}(10)$ in favour of NUTS. However, this efficiency is reduced to a factor ∼2 when quantified in terms of computational time, since we find the cost of the gradient computation (needed by NUTS) relative to the likelihood to be ∼4.5 times larger for both experiments. We validate these results making use of analytical multi-variate distributions (a multivariate Gaussian and a Rosenbrock distribution) with increasing dimensionality. Based on these results, we conclude that gradient-based samplers such as ${tt NUTS}$ can be leveraged to sample high dimensional parameter spaces in Cosmology, although the efficiency improvement is relatively mild for moderate (${mathcal {O}}(50)$) dimension numbers, typical of tomographic large-scale structure analyses.
{"title":"Assessment of Gradient-Based Samplers in Standard Cosmological Likelihoods","authors":"Arrykrishna Mootoovaloo, Jaime Ruiz-Zapatero, Carlos García-García, David Alonso","doi":"10.1093/mnras/stae2138","DOIUrl":"https://doi.org/10.1093/mnras/stae2138","url":null,"abstract":"We assess the usefulness of gradient-based samplers, such as the No-U-Turn Sampler (${tt NUTS}$), by comparison with traditional Metropolis-Hastings algorithms, in tomographic 3 × 2 point analyses. Specifically, we use the DES Year 1 data and a simulated future LSST-like survey as representative examples of these studies, containing a significant number of nuisance parameters (20 and 32, respectively) that affect the performance of rejection-based samplers. To do so, we implement a differentiable forward model using JAX-COSMO, and we use it to derive parameter constraints from both datasets using the NUTS algorithm implemented in ${tt numpyro}$, and the Metropolis-Hastings algorithm as implemented in Cobaya. When quantified in terms of the number of effective number of samples taken per likelihood evaluation, we find a relative efficiency gain of ${mathcal {O}}(10)$ in favour of NUTS. However, this efficiency is reduced to a factor ∼2 when quantified in terms of computational time, since we find the cost of the gradient computation (needed by NUTS) relative to the likelihood to be ∼4.5 times larger for both experiments. We validate these results making use of analytical multi-variate distributions (a multivariate Gaussian and a Rosenbrock distribution) with increasing dimensionality. Based on these results, we conclude that gradient-based samplers such as ${tt NUTS}$ can be leveraged to sample high dimensional parameter spaces in Cosmology, although the efficiency improvement is relatively mild for moderate (${mathcal {O}}(50)$) dimension numbers, typical of tomographic large-scale structure analyses.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"74 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256402","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 use high-resolution MHD simulations of isolated disk galaxies to investigate the co-evolution of magnetic fields with a self-regulated, star-forming interstellar medium (ISM). The simulations are conducted using the Ramses AMR code on the standard Agora initial condition, with gas cooling, star formation and feedback. We run galaxies with a variety of initial magnetic field strengths. The fields evolve and achieve approximate saturation within 500 Myr, but at different levels. The galaxies reach a quasi-steady state, with slowly declining star formation due to both gas consumption and increases in the field strength at intermediate ISM densities. We connect this behaviour to differences in the gas properties and overall structure of the galaxies. Stronger magnetic fields limit supernova bubble sizes. Different cases support the ISM using varying combinations of magnetic pressure, turbulence and thermal energy. Initially ≳ 1 μG magnetic fields evolve modestly and dominate support at all radii. Conversely, initially weaker fields grow through feedback and turbulence but never dominate the support. This is reflected in the stability of the gas disk. This interplay determines the overall distribution of star formation in each case. We conclude that an initially weak field can grow to produce a realistic model of a local disk galaxy, but starting with typically assumed field strengths (≳ 1 μG) will not.
我们利用孤立盘状星系的高分辨率 MHD 模拟来研究磁场与自我调节、恒星形成的星际介质（ISM）的共同演化。模拟是使用 Ramses AMR 代码在标准 Agora 初始条件下进行的，包括气体冷却、恒星形成和反馈。我们运行了具有各种初始磁场强度的星系。这些磁场在 500 Myr 内不断演化并达到近似饱和状态，但强度各不相同。星系达到准稳定状态，在中等 ISM 密度时，由于气体消耗和磁场强度增加，恒星形成缓慢下降。我们将这种行为与星系的气体性质和整体结构的差异联系起来。较强的磁场限制了超新星泡的大小。不同的情况下，ISM 使用不同的磁压、湍流和热能组合来支持。最初≳ 1 μG 磁场的演化并不强，在所有半径上的支持都占主导地位。相反，最初较弱的磁场会通过反馈和湍流增长，但永远不会主导支撑。这反映在气体盘的稳定性上。这种相互作用决定了每种情况下恒星形成的总体分布。我们的结论是，最初较弱的场可以增长，从而产生一个逼真的局部盘状星系模型，但从通常假定的场强（≳ 1 μG）开始就不行了。
{"title":"Regulating star formation in a magnetized disk galaxy","authors":"Hector Robinson, James Wadsley","doi":"10.1093/mnras/stae2132","DOIUrl":"https://doi.org/10.1093/mnras/stae2132","url":null,"abstract":"We use high-resolution MHD simulations of isolated disk galaxies to investigate the co-evolution of magnetic fields with a self-regulated, star-forming interstellar medium (ISM). The simulations are conducted using the Ramses AMR code on the standard Agora initial condition, with gas cooling, star formation and feedback. We run galaxies with a variety of initial magnetic field strengths. The fields evolve and achieve approximate saturation within 500 Myr, but at different levels. The galaxies reach a quasi-steady state, with slowly declining star formation due to both gas consumption and increases in the field strength at intermediate ISM densities. We connect this behaviour to differences in the gas properties and overall structure of the galaxies. Stronger magnetic fields limit supernova bubble sizes. Different cases support the ISM using varying combinations of magnetic pressure, turbulence and thermal energy. Initially ≳ 1 μG magnetic fields evolve modestly and dominate support at all radii. Conversely, initially weaker fields grow through feedback and turbulence but never dominate the support. This is reflected in the stability of the gas disk. This interplay determines the overall distribution of star formation in each case. We conclude that an initially weak field can grow to produce a realistic model of a local disk galaxy, but starting with typically assumed field strengths (≳ 1 μG) will not.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"31 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256113","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}
Boyuan Liu, James Gurian, Kohei Inayoshi, Shingo Hirano, Takashi Hosokawa, Volker Bromm, Naoki Yoshida
JWST has brought us new insights into Cosmic Dawn with tentative detection of the unique signatures of metal-free Population III (Pop III) stars, such as strong He II emission, extremely blue ultraviolet spectrum, and enhanced nitrogen abundance. Self-consistent theoretical predictions of the formation rates, sites, and masses of Pop III stars are crucial for interpreting the observations, but are challenging due to complex physical processes operating over the large range of length-scales involved. One solution is to combine analytical models for the small-scale star formation process with cosmological simulations that capture the large-scale physics such as structure formation, radiation backgrounds, and baryon-dark matter streaming motion that regulate the conditions of Pop III star formation. We build an analytical model to predict the final masses of Pop III stars/clusters from the properties of star-forming clouds, based on the key results of small-scale star formation simulations and stellar evolution models. Our model for the first time considers the interplay between feedback and fragmentation and covers different modes of Pop III star formation ranging from ordinary small ($sim!{10{-}2000} rm M_odot$) clusters in molecular-cooling clouds to massive ($gtrsim!{10^{4}} rm M_odot$) clusters containing supermassive ($sim!{10^{4}{-}3}times 10^{5} rm M_odot$) stars under violent collapse of atomic-cooling clouds with large gas accretion rates of $gtrsim!{0.1} rm M_odot yr^{-1}$. As an example, the model is applied to the Pop III star-forming clouds in the progenitors of typical haloes hosting high-z luminous quasars ($M_{rm h}sim 10^{12} rm M_odot$ at $zsim 6$), which shows that formation of Pop III massive clusters is common ($sim!{20{-}70}{{ rm per cent}}$) in such biased ($sim!{4}sigma$) regions, and the resulting heavy black hole seeds from supermassive stars can account for a significant fraction of observed luminous ($gtrsim!{10^{46}} rm erg s^{-1}$) quasars at $zsim 6$.
JWST 初步探测到了无金属种群 III（Pop III）恒星的独特特征，如强烈的 He II 发射、极蓝的紫外光谱和增强的氮丰度，从而为我们带来了对宇宙黎明的新认识。对 Pop III 星的形成率、位置和质量进行自洽的理论预测对解释观测结果至关重要，但由于涉及的长度尺度范围大，物理过程复杂，因此具有挑战性。解决方法之一是将小尺度恒星形成过程的分析模型与宇宙学模拟相结合，后者能捕捉到大尺度物理过程，如结构形成、辐射背景和重子-暗物质流运动等，这些都调节着 Pop III 恒星形成的条件。我们根据小尺度恒星形成模拟和恒星演化模型的主要结果，建立了一个分析模型，从恒星形成云的性质预测波普III恒星/星团的最终质量。我们的模型首次考虑了反馈和碎裂之间的相互作用，涵盖了Pop III恒星形成的不同模式，从分子冷却云中的普通小（$sim!{10{-}2000}rm M_odot$）星团到大质量（$gtrsim！{的超大质量恒星（10^{4}{-}3}倍于10^{5} rm M_odot$）的星团，这些恒星是在原子冷却云的剧烈坍缩下形成的，气体吸积率为$gtrsim!{0.1} rm M_odot yr^{-1}$。作为一个例子，我们把这个模型应用到了承载高z亮度类星体的典型光环（$M_{rm h}sim 10^{12}rm M_odot$ at $zsim 6$）的原生体中的Pop III恒星形成云，结果表明Pop III大质量星团的形成是很常见的（$sim！{20{-}70}{{rm per cent}}$），而由此产生的来自超大质量恒星的重黑洞种子可以解释在$zsim 6$观测到的发光类星体（$gtrsim!{10^{46}} rm erg s^{-1}$）的很大一部分。
{"title":"Towards a universal analytical model for Population III star formation: interplay between feedback and fragmentation","authors":"Boyuan Liu, James Gurian, Kohei Inayoshi, Shingo Hirano, Takashi Hosokawa, Volker Bromm, Naoki Yoshida","doi":"10.1093/mnras/stae2066","DOIUrl":"https://doi.org/10.1093/mnras/stae2066","url":null,"abstract":"JWST has brought us new insights into Cosmic Dawn with tentative detection of the unique signatures of metal-free Population III (Pop III) stars, such as strong He II emission, extremely blue ultraviolet spectrum, and enhanced nitrogen abundance. Self-consistent theoretical predictions of the formation rates, sites, and masses of Pop III stars are crucial for interpreting the observations, but are challenging due to complex physical processes operating over the large range of length-scales involved. One solution is to combine analytical models for the small-scale star formation process with cosmological simulations that capture the large-scale physics such as structure formation, radiation backgrounds, and baryon-dark matter streaming motion that regulate the conditions of Pop III star formation. We build an analytical model to predict the final masses of Pop III stars/clusters from the properties of star-forming clouds, based on the key results of small-scale star formation simulations and stellar evolution models. Our model for the first time considers the interplay between feedback and fragmentation and covers different modes of Pop III star formation ranging from ordinary small ($sim!{10{-}2000} rm M_odot$) clusters in molecular-cooling clouds to massive ($gtrsim!{10^{4}} rm M_odot$) clusters containing supermassive ($sim!{10^{4}{-}3}times 10^{5} rm M_odot$) stars under violent collapse of atomic-cooling clouds with large gas accretion rates of $gtrsim!{0.1} rm M_odot yr^{-1}$. As an example, the model is applied to the Pop III star-forming clouds in the progenitors of typical haloes hosting high-z luminous quasars ($M_{rm h}sim 10^{12} rm M_odot$ at $zsim 6$), which shows that formation of Pop III massive clusters is common ($sim!{20{-}70}{{ rm per cent}}$) in such biased ($sim!{4}sigma$) regions, and the resulting heavy black hole seeds from supermassive stars can account for a significant fraction of observed luminous ($gtrsim!{10^{46}} rm erg s^{-1}$) quasars at $zsim 6$.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"28 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256119","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}
In the core accretion model of planet formation, envelope cooling regulates the accretion of material and ultimately sets the timescale to form a giant planet. Given the diversity of planet-forming environments, opacity uncertainties, and the advective transport of energy by 3-dimensional recycling flows, it is unclear whether 1D models can adequately describe envelope structure and accretion in all regimes. Even in 3D models, it is unclear whether approximate radiative transfer methods sufficiently model envelope cooling particularly at the planetary photosphere. To address these uncertainties, we present a suite of 3D radiation hydrodynamics simulations employing methods that directly solve the transfer equation. We perform a parameter space study, formulated in terms of dimensionless parameters, for a variety of envelope optical depths and cooling times. We find that the thermodynamic structure of the envelope ranges from adiabatic to isothermal based on the cooling time and by extension, the background disk temperature and density. By adopting a dimensionless framework, these models can be applied to a wide range of formation conditions and assumed opacities. In particular, we dimensionalize them to the case of a super-Earth and proto-Jupiter and place upper limits on the 3D mass accretion rates prior to runaway growth. Finally, we evaluate the fidelity of approximate radiative transfer methods and find that even in the most challenging cases, more approximate methods are sufficiently accurate and worth their savings in computational cost.
{"title":"A Systematic Study of Planetary Envelope Growth with 3D Radiation-Hydrodynamics Simulations","authors":"Avery Bailey, James M Stone, Jeffrey Fung","doi":"10.1093/mnras/stae2126","DOIUrl":"https://doi.org/10.1093/mnras/stae2126","url":null,"abstract":"In the core accretion model of planet formation, envelope cooling regulates the accretion of material and ultimately sets the timescale to form a giant planet. Given the diversity of planet-forming environments, opacity uncertainties, and the advective transport of energy by 3-dimensional recycling flows, it is unclear whether 1D models can adequately describe envelope structure and accretion in all regimes. Even in 3D models, it is unclear whether approximate radiative transfer methods sufficiently model envelope cooling particularly at the planetary photosphere. To address these uncertainties, we present a suite of 3D radiation hydrodynamics simulations employing methods that directly solve the transfer equation. We perform a parameter space study, formulated in terms of dimensionless parameters, for a variety of envelope optical depths and cooling times. We find that the thermodynamic structure of the envelope ranges from adiabatic to isothermal based on the cooling time and by extension, the background disk temperature and density. By adopting a dimensionless framework, these models can be applied to a wide range of formation conditions and assumed opacities. In particular, we dimensionalize them to the case of a super-Earth and proto-Jupiter and place upper limits on the 3D mass accretion rates prior to runaway growth. Finally, we evaluate the fidelity of approximate radiative transfer methods and find that even in the most challenging cases, more approximate methods are sufficiently accurate and worth their savings in computational cost.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"17 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256117","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}
Heterocycles have not been detected in the interstellar medium (ISM) yet. However, the direct involvement of some pentagonal heterocycles within the formation of key biomolecules for the origin of life makes the search for these systems in the ISM relevant for understanding whether some of the bricks of life could be formed in the ISM. We have explored the possible formation of the simple heterocycle furan (c-C4H4O) under interstellar conditions, through the reaction between two interstellar species, syn-vinyl alcohol (syn-VA) and the CCH radical. We employed state-of-the-art quantum-chemical calculations to elucidate the reaction mechanism between the reaction of CCH radical and syn-VA. Kinetic simulations were carried out aiming to quantitatively assess the viability of this reaction in the ISM. We have found a reaction pathway to furan where all energy barriers are submerged. However, the formation of this heterocycle is not feasible because the intermediates leading to furan can evolve through more favourable routes. In contrast, we have found viable pathways for the formation of the four isomers of 1-butenol-3-yne (HCCCHCHOH) (Z-syn, E-syn, E-anti and Z-anti), which thus are promising species to be detected in the ISM. Our theoretical work indicates that the four isomers of 1-butenol-3-yne should be present in the ISM, because the precursors are known interstellar species, and the kinetic simulations indicates that their formation is very likely. We then encourage the observational search of these molecules in the ISM.
星际介质（ISM）中尚未探测到杂环。然而，由于一些五角杂环直接参与了生命起源的关键生物分子的形成，因此在星际介质中寻找这些系统与了解一些生命之砖是否可能在星际介质中形成息息相关。我们探索了在星际条件下，通过合成乙烯醇（syn-VA）和 CCH 自由基这两种星际物质之间的反应，形成简单杂环呋喃（c-C4H4O）的可能性。我们采用了最先进的量子化学计算方法来阐明 CCH 自由基与 syn-VA 之间的反应机理。我们还进行了动力学模拟，旨在定量评估该反应在 ISM 中的可行性。我们发现了一条通向呋喃的反应途径，在这条途径中，所有能量障碍都被淹没。然而，这种杂环的形成并不可行，因为导致呋喃的中间产物可以通过更有利的途径演化。与此相反，我们发现了形成 1-丁烯醇-3-炔（HCCCHCHOH）的四种异构体（Z-syn、E-syn、E-anti 和 Z-anti）的可行途径，因此这四种异构体有望在 ISM 中被探测到。我们的理论研究表明，1-丁烯醇-3-炔的四种异构体应该存在于 ISM 中，因为它们的前体是已知的星际物质，而且动力学模拟表明它们的形成是非常有可能的。因此，我们鼓励在 ISM 中对这些分子进行观测搜索。
{"title":"Unfruitful chemical pathway for interstellar furan: formation of the four isomers of 1-butenol-3-yne","authors":"J García de la Concepción, V M Rivilla","doi":"10.1093/mnras/stae2118","DOIUrl":"https://doi.org/10.1093/mnras/stae2118","url":null,"abstract":"Heterocycles have not been detected in the interstellar medium (ISM) yet. However, the direct involvement of some pentagonal heterocycles within the formation of key biomolecules for the origin of life makes the search for these systems in the ISM relevant for understanding whether some of the bricks of life could be formed in the ISM. We have explored the possible formation of the simple heterocycle furan (c-C4H4O) under interstellar conditions, through the reaction between two interstellar species, syn-vinyl alcohol (syn-VA) and the CCH radical. We employed state-of-the-art quantum-chemical calculations to elucidate the reaction mechanism between the reaction of CCH radical and syn-VA. Kinetic simulations were carried out aiming to quantitatively assess the viability of this reaction in the ISM. We have found a reaction pathway to furan where all energy barriers are submerged. However, the formation of this heterocycle is not feasible because the intermediates leading to furan can evolve through more favourable routes. In contrast, we have found viable pathways for the formation of the four isomers of 1-butenol-3-yne (HCCCHCHOH) (Z-syn, E-syn, E-anti and Z-anti), which thus are promising species to be detected in the ISM. Our theoretical work indicates that the four isomers of 1-butenol-3-yne should be present in the ISM, because the precursors are known interstellar species, and the kinetic simulations indicates that their formation is very likely. We then encourage the observational search of these molecules in the ISM.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"23 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256118","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}
Mainak Mukhopadhyay, Mukul Bhattacharya, Kohta Murase
Recent radio observations and coincident neutrino detections suggest that some tidal disruption events (TDEs) exhibit late-time activities, relative to the optical ehmission peak, and these may be due to delayed outflows launched from the central supermassive black hole. We investigate te possibility that jets launched with a time delay of days to months, interact with a debris that may expand outwards. We discuss the effects of the time delay and expansion velocity on the outcomes of jet breakout and collimation. We find that a jet with an isotropic-equivalent luminosity of ≲ 5 × 1045 erg/s is likely to be choked for a delay time of ∼3 months. We also study the observational signatures of such delayed choked jets. The jet-debris interaction preceding the breakout would lead to particle acceleration and the resulting synchrotron emission can be detected by current and near-future radio, optical and X-ray telescopes, and the expanding jet-driven debris could explain late-time radio emission. We discuss high-energy neutrino production in delayed choked jets, and the time delay can significantly alleviate the difficulty of the hidden jet scenario in explaining neutrino coincidences.
{"title":"Multi-messenger signatures of delayed choked jets in tidal disruption events","authors":"Mainak Mukhopadhyay, Mukul Bhattacharya, Kohta Murase","doi":"10.1093/mnras/stae2080","DOIUrl":"https://doi.org/10.1093/mnras/stae2080","url":null,"abstract":"Recent radio observations and coincident neutrino detections suggest that some tidal disruption events (TDEs) exhibit late-time activities, relative to the optical ehmission peak, and these may be due to delayed outflows launched from the central supermassive black hole. We investigate te possibility that jets launched with a time delay of days to months, interact with a debris that may expand outwards. We discuss the effects of the time delay and expansion velocity on the outcomes of jet breakout and collimation. We find that a jet with an isotropic-equivalent luminosity of ≲ 5 × 1045 erg/s is likely to be choked for a delay time of ∼3 months. We also study the observational signatures of such delayed choked jets. The jet-debris interaction preceding the breakout would lead to particle acceleration and the resulting synchrotron emission can be detected by current and near-future radio, optical and X-ray telescopes, and the expanding jet-driven debris could explain late-time radio emission. We discuss high-energy neutrino production in delayed choked jets, and the time delay can significantly alleviate the difficulty of the hidden jet scenario in explaining neutrino coincidences.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"44 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256125","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}
Steven R Janssens, Duncan A Forbes, Aaron J Romanowsky, Jonah Gannon, Joel Pfeffer, Warrick J Couch, Jean P Brodie, William E Harris, Patrick R Durrell, Kenji Bekki
We present Hubble Space Telescope ACS/WFC and WFC3/UVIS imaging for a sample of 50 low surface brightness (LSB) galaxies in the ∼1015 M⊙ Perseus cluster, which were originally identified in ground-based imaging. We measure the structural properties of these galaxies and estimate the total number of globular clusters (GCs) they host. Around half of our sample galaxies meet the strict definition of an ultra-diffuse galaxy (UDG), while the others are UDG-like but are either somewhat more compact or slightly brighter. A small number of galaxies reveal systems with many tens of GCs, rivalling some of the richest GC systems known around UDGs in the Coma cluster. We find the sizes of rich GC systems, in terms of their half-number radii, extending to ∼1.2 times the half-light radii of their host galaxy on average. The mean colours of the GC systems are the same, within the uncertainties, as those of their host galaxy stars. This suggests that GCs and galaxy field stars may have formed at the same epoch from the same enriched gas. It may also indicate a significant contribution from disrupted GCs to the stellar component of the host galaxy as might be expected in the ‘failed galaxy’ formation scenario for UDGs.
{"title":"The PIPER survey. II. The globular cluster systems of low surface brightness galaxies in the perseus cluster","authors":"Steven R Janssens, Duncan A Forbes, Aaron J Romanowsky, Jonah Gannon, Joel Pfeffer, Warrick J Couch, Jean P Brodie, William E Harris, Patrick R Durrell, Kenji Bekki","doi":"10.1093/mnras/stae2137","DOIUrl":"https://doi.org/10.1093/mnras/stae2137","url":null,"abstract":"We present Hubble Space Telescope ACS/WFC and WFC3/UVIS imaging for a sample of 50 low surface brightness (LSB) galaxies in the ∼1015 M⊙ Perseus cluster, which were originally identified in ground-based imaging. We measure the structural properties of these galaxies and estimate the total number of globular clusters (GCs) they host. Around half of our sample galaxies meet the strict definition of an ultra-diffuse galaxy (UDG), while the others are UDG-like but are either somewhat more compact or slightly brighter. A small number of galaxies reveal systems with many tens of GCs, rivalling some of the richest GC systems known around UDGs in the Coma cluster. We find the sizes of rich GC systems, in terms of their half-number radii, extending to ∼1.2 times the half-light radii of their host galaxy on average. The mean colours of the GC systems are the same, within the uncertainties, as those of their host galaxy stars. This suggests that GCs and galaxy field stars may have formed at the same epoch from the same enriched gas. It may also indicate a significant contribution from disrupted GCs to the stellar component of the host galaxy as might be expected in the ‘failed galaxy’ formation scenario for UDGs.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"1 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256201","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}
Black holes are believed to be crucial in regulating star formation in massive galaxies, which makes it essential to faithfully represent the physics of these objects in cosmological hydrodynamics simulations. Limited spatial and mass resolution and the associated discreteness noise make following the dynamics of black holes especially challenging. In particular, dynamical friction, which is responsible for driving massive black holes towards the centres of galaxies, cannot be accurately modelled with softened N-body interactions. A number of subgrid models have been proposed to mimic dynamical friction or directly include its full effects in simulations. Each of these methods has its individual benefits and shortcomings, while all suffer from a common issue of being unable to represent black holes with masses below a few times the simulated dark matter particle mass. In this paper, we propose a correction for unresolved dynamical friction, which has been calibrated on simulations run with the code KETJU, in which gravitational interactions of black holes are not softened. We demonstrate that our correction is able to sink black holes with masses greater than the dark matter particle mass at the correct rate. We show that the impact of stochasticity is significant for low-mass black holes (MBH ≤ 5MDM) and propose a correction for stochastic heating. Combined, this approach is applicable to next generation cosmological hydrodynamics simulations that jointly track galaxy and black hole growth with realistic black hole orbits.
黑洞被认为是调节大质量星系恒星形成的关键，因此在宇宙学流体力学模拟中忠实再现这些天体的物理特性至关重要。有限的空间和质量分辨率以及相关的离散性噪声使得跟踪黑洞的动力学尤其具有挑战性。尤其是动力学摩擦，它是驱动大质量黑洞向星系中心移动的原因，但却无法用软化的 N 体相互作用来准确模拟。为了模拟动力学摩擦或直接将其全部影响纳入模拟，人们提出了许多子网格模型。这些方法各有利弊，但都有一个共同的问题，即无法表示质量低于模拟暗物质粒子质量几倍的黑洞。在本文中，我们提出了一种未解决的动力学摩擦校正方法，并在 KETJU 代码运行的模拟中进行了校正，在该模拟中，黑洞的引力相互作用没有被软化。我们证明，我们的修正能够以正确的速率使质量大于暗物质粒子质量的黑洞下沉。我们证明随机性对低质量黑洞（MBH ≤ 5MDM）的影响很大，并提出了随机加热的修正方法。结合起来，这种方法适用于下一代宇宙学流体力学模拟，即用现实的黑洞轨道联合跟踪星系和黑洞的增长。
{"title":"A calibrated model for N-body dynamical friction acting on supermassive black holes","authors":"Anna Genina, Volker Springel, Antti Rantala","doi":"10.1093/mnras/stae2144","DOIUrl":"https://doi.org/10.1093/mnras/stae2144","url":null,"abstract":"Black holes are believed to be crucial in regulating star formation in massive galaxies, which makes it essential to faithfully represent the physics of these objects in cosmological hydrodynamics simulations. Limited spatial and mass resolution and the associated discreteness noise make following the dynamics of black holes especially challenging. In particular, dynamical friction, which is responsible for driving massive black holes towards the centres of galaxies, cannot be accurately modelled with softened N-body interactions. A number of subgrid models have been proposed to mimic dynamical friction or directly include its full effects in simulations. Each of these methods has its individual benefits and shortcomings, while all suffer from a common issue of being unable to represent black holes with masses below a few times the simulated dark matter particle mass. In this paper, we propose a correction for unresolved dynamical friction, which has been calibrated on simulations run with the code KETJU, in which gravitational interactions of black holes are not softened. We demonstrate that our correction is able to sink black holes with masses greater than the dark matter particle mass at the correct rate. We show that the impact of stochasticity is significant for low-mass black holes (MBH ≤ 5MDM) and propose a correction for stochastic heating. Combined, this approach is applicable to next generation cosmological hydrodynamics simulations that jointly track galaxy and black hole growth with realistic black hole orbits.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"54 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256116","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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