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Tetrahedral grids in Monte Carlo radiative transfer 蒙特卡洛辐射传输中的四面体网格
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202450658
Arno Lauwers, M. Baes, P. Camps, Bert Vander Meulen
To understand the structures of complex astrophysical objects, 3D numerical simulations of radiative transfer processes are invaluable. For Monte Carlo radiative transfer, the most common radiative transfer method in 3D, the design of a spatial grid is important and non-trivial. Common choices include hierarchical octree and unstructured Voronoi grids, each of which has advantages and limitations. Tetrahedral grids, commonly used in ray-tracing computer graphics, can be an interesting alternative option. We aim to investigate the possibilities, advantages, and limitations of tetrahedral grids in the context of Monte Carlo radiative transfer. In particular, we want to compare the performance of tetrahedral grids to other commonly used grid structures. We implemented a tetrahedral grid structure, based on the open-source library TetGen, in the generic Monte Carlo radiative transfer code SKIRT. Tetrahedral grids can be imported from external applications or they can be constructed and adaptively refined within SKIRT. We implemented an efficient grid traversal method based on Pl"ucker coordinates and Pl"ucker products. The correct implementation of the tetrahedral grid construction and the grid traversal algorithm in SKIRT were validated using 2D radiative transfer benchmark problems. Using a simple 3D model, we compared the performance of tetrahedral, octree, and Voronoi grids. With a constant cell count, the octree grid outperforms the tetrahedral and Voronoi grids in terms of traversal speed, whereas the tetrahedral grid is poorer than the other grids in terms of grid quality. All told, we find that the performance of tetrahedral grids is relatively poor compared to octree and Voronoi grids. Although the adaptively constructed tetrahedral grids might not be favourable in most media representative of astrophysical simulation models, they still form an interesting unstructured alternative to Voronoi grids for specific applications. In particular, they might prove useful for radiative transfer post-processing of hydrodynamical simulations run on tetrahedral or unstructured grids.
要了解复杂天体的结构,辐射传递过程的三维数值模拟非常重要。蒙特卡洛辐射传递是最常用的三维辐射传递方法,对于它来说,空间网格的设计既重要又不简单。常见的选择包括分层八叉网格和非结构化 Voronoi 网格,这两种网格各有优势和局限性。光线跟踪计算机图形常用的四面体网格是一种有趣的替代选择。我们旨在研究四面体网格在蒙特卡罗辐射传输中的可能性、优势和局限性。特别是,我们希望将四面体网格的性能与其他常用网格结构进行比较。我们在通用蒙特卡洛辐射传递代码 SKIRT 中基于开源库 TetGen 实现了四面体网格结构。四面体网格可以从外部应用程序导入,也可以在 SKIRT 中构建并自适应细化。我们基于 Pl"ucker 坐标和 Pl"ucker 乘积实现了一种高效的网格遍历方法。使用二维辐射传输基准问题验证了 SKIRT 中四面体网格构建和网格遍历算法的正确实施。通过一个简单的三维模型,我们比较了四面体网格、八叉树网格和 Voronoi 网格的性能。在单元数不变的情况下,八叉网格的遍历速度优于四面体网格和 Voronoi 网格,而四面体网格的网格质量不如其他网格。总之,我们发现四面体网格的性能比八叉网格和 Voronoi 网格相对较差。虽然自适应构建的四面体网格在大多数具有代表性的天体物理模拟模型介质中可能并不理想,但在特定应用中,它们仍然是 Voronoi 网格的一种有趣的非结构化替代方案。特别是,对于在四面体或非结构网格上运行的流体力学模拟的辐射传递后处理,它们可能证明是有用的。
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引用次数: 0
Carbon enrichment in APOGEE disk stars as evidence of mass transfer in binaries APOGEE盘状恒星中的碳富集是双星质量转移的证据
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202450014
Steve Foster, R. Schiavon, Denise B. de Castro, S. Lucatello, C. Daher, Z. Penoyre, A. Price-Whelan, Carles Badenes, J. G. Fern'andez-Trincado, D. A. Garc'ia-Hern'andez, Jon A. Holtzman, H. Jőnsson, M. Shetrone
Carbon abundances in first-ascent giant stars are usually lowerthan those of their main-sequence counterparts.At moderate metallicities, stellar evolution of single stars cannot account for the existence of red-giant branch stars with enhanced carbon abundances. The phenomenon is usually interpreted as resulting from past mass transfer from an evolved binary companion now in the white dwarf evolutionary stage. We aim to confirm the links between C/O enhancement, $s-$process element enhancement and binary fraction using large-scale catalogues of stellar abundances and probable binary stars. We use a large data set from the 17$^ th $ data release of the SDSS-IV/APOGEE 2 survey to identify carbon-enhanced stars in the Galactic disk. We identify a continuum of carbon enrichment throughout three different sub-populations of disk stars and explore links between the degree of carbon enrichment and binary frequency, metallicity and chemical compositions. We verify a clear correlation between binary frequency and enhancement in the abundances of both carbon and cerium, lending support to the scenario whereby carbon-enhanced stars are the result of mass transfer by an evolved binary companion. In addition, we identify clustering in the carbon abundances of high-alpha disk stars, suggesting that those on the high metallicity end are likely younger, in agreement with theoretical predictions for the presence of a starburst population following the gas-rich merger of the Gaia-Enceladus/Sausage system.
在中等金属度的情况下,单星的恒星演化无法解释碳丰度增强的红巨星分支恒星的存在。在中等金属度下,单星演化无法解释存在碳丰度增强的红巨星分支恒星的原因,这种现象通常被解释为过去从处于白矮星演化阶段的演化双星伴星进行质量转移的结果。我们的目的是利用大规模的恒星丰度和可能的双星星表来证实C/O增强、$s-$过程元素增强和双星分数之间的联系。我们利用 SDSS-IV/APOGEE 2 勘测发布的第 17$^ th $ 次数据中的大型数据集来识别银河系盘中的碳增强恒星。我们在三个不同的星盘恒星亚群中发现了碳富集的连续性,并探索了碳富集程度与双星频率、金属性和化学成分之间的联系。我们验证了双星频率与碳和铈丰度增强之间的明显相关性,为碳增强恒星是进化双星伴星质量转移的结果这一假设提供了支持。此外,我们还发现了高α盘恒星碳丰度的聚类现象,这表明那些金属性较高的恒星很可能比较年轻,这与理论预测的盖亚-恩克拉多斯/香肠系统富含气体合并后出现星爆群体的情况相吻合。
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引用次数: 0
A lack of Lyman alpha emitters within 5Mpc of a luminous quasar in an overdensity at z=6.9: Potential evidence of negative quasar feedback at protocluster scales z=6.9密度过大的类星体附近5Mpc范围内缺乏莱曼α发射器:原星团尺度上类星体负反馈的潜在证据
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202449566
T. Lambert, R. Assef, C. Mazzucchelli, E. Bañados, M. Aravena, F. Barrientos, J. González-López, W. Hu, L. Infante, S. Malhotra, C. Moya-Sierralta, J. Rhoads, F. Valdes, J. Wang, I. Wold, Z. Zheng
High-redshift quasars are thought to live in the densest regions of space, which should be made evident by an overdensity of galaxies around them. However, campaigns to identify these overdensities by searching for Lyman-break galaxies (LBGs) and Lyman alpha emitters (LAEs) have had mixed results. These may be explained by either the small field of view of some of the experiments, the broad redshift ranges targeted by LBG searches, and the inherently high uncertainty of quasar redshifts estimated from ultraviolet emission lines, which makes it difficult to place the Ly-alpha emission line within a narrowband filter. Here, we present a 3 square degree search ($ 1000$ pMpc2) for LAEs around the $z=6.9$ quasar VIK J2348--3054 using the Dark Energy CAMera (DECam) housed on the 4m Blanco telescope, finding 38 LAEs. The systemic redshift of VIK J2348--3054 is known from ALMA CII observations and places the Ly-alpha emission line of companions within the NB964 narrowband of DECam. This is the largest field-of-view LAE search around a $z>6$ quasar conducted to date. We find that this field is sim ten times more overdense than Chandra Deep-Field South, observed previously with the same instrumental setup as well as several combined blank fields. This is strong evidence that VIK J2348--3054 resides in an overdensity of LAEs over several Mpc. Surprisingly, we find a lack of LAEs within 5 physical Mpc of the quasar and take this to most likely be evidence of quasar-suppressing star formation in its immediate vicinity. This result highlights the importance of performing overdensity searches over large areas to properly assess the density of those regions of the Universe.
高红移类星体被认为生活在空间密度最高的区域,其周围的星系密度过高就证明了这一点。然而,通过搜索莱曼破碎星系(LBGs)和莱曼阿尔法发射体(LAEs)来确定这些超密度的活动,结果喜忧参半。这可能是由于某些实验的视场太小,LBG 搜寻的目标红移范围太广,以及根据紫外发射线估算的类星体红移本身就具有很高的不确定性,因此很难将 Ly-α 发射线置于窄带滤波器中。在此,我们利用布兰科 4 米望远镜上的暗能量相机(DECam),对 $z=6.9$ 类星 VIK J2348--3054 周围的 LAE 进行了 3 平方度($ 1000$ pMpc2)的搜索,发现了 38 个 LAE。VIK J2348--3054的系统红移是通过ALMA CII观测得知的,并将伴星的Ly-alpha发射线置于DECam的NB964窄带内。这是迄今为止在$z>6$类星体周围进行的最大视场LAE搜索。我们发现,这个视场的过密程度是钱德拉深视场南区的十倍,而钱德拉深视场南区是以前用同样的仪器设备以及几个组合空白视场观测到的。这有力地证明了VIK J2348--3054所在的LAE密度超过了几个Mpc。令人吃惊的是,我们发现在类星体5 Mpc物理范围内缺乏LAEs,并认为这很可能是类星体抑制其附近恒星形成的证据。这一结果凸显了在大范围内进行超密度搜索以正确评估宇宙中这些区域密度的重要性。
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引用次数: 0
Revisiting Jupiter's deuterium fraction in the rotational ground-state line of HD at high spectral resolution 以高光谱分辨率重新审视高清旋转基态线中木星的氘分数
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202450115
H. Wiesemeyer, R. Gusten, P. Hartogh, Yoko Okada, O. Ricken, J. Stutzki
The cosmic deuterium fraction, set by primordial nucleosynthesis and diminished by subsequent astration, is a valuable diagnostic tool to link the protosolar nebula to the history of star formation. However, in the present-day Solar System, the deuterium fraction in various carriers varies by more than an order of magnitude and reflects environmental conditions rather than the protosolar value. The latter is believed to be preserved in the atmospheres of the gas giant planets, yet determinations inferred from the CH$_3$D/CH$_4$ pair require a larger fractionation correction than those from HD/H$_2$, which are close to unity. The question of whether a stratospheric emission feature contaminates the absorption profile forming in subjacent layers was never addressed, owing to the lack of spectral resolving power. Here we report on the determination of the Jovian deuterium fraction using the rotational ground-state line of HD ($J=1-0$) at $ Employing the GREAT heterodyne spectrometer on board SOFIA, we detected the HD absorption and, thanks to the high resolving power, a weak stratospheric emission feature underneath; the former is blue-shifted with respect to the latter. The displacement is attributed to a pressure-induced line shift and reproduced by dedicated radiative-transfer modeling based on recent line-profile parameters. Using atmospheric standard models, we obtained $ D/H $, which agrees with a recent measurement in Saturn's atmosphere and with the value inferred from solar-wind measurements and meteoritic data. The result suggests that all three measurements represent bona fide protosolar D/H fractions. As a supplement and test for the consistency of the layering assumed in our model, we provide an analysis of the purely rotational $J=6-5$ line of CH$_4$ (in the vibrational ground state, at $ mu$m).
宇宙氘分数由原始核合成设定,并在随后的星际沉积中减少,是将原极星云与恒星形成史联系起来的宝贵诊断工具。然而,在现今的太阳系中,各种载体中的氘分数相差一个数量级以上,反映的是环境条件而不是原极值。后者被认为保留在气态巨行星的大气中,然而从 CH$_3$D/CH$_4$ 对推断出的测定值需要比从 HD/H$_2$ 得出的值更大的分馏修正,后者接近于统一值。由于缺乏光谱分辨能力,平流层发射特征是否会污染在相邻层形成的吸收剖面这一问题从未得到解决。在此,我们报告了利用氘的旋转基态线($J=1-0$)在$处测定侏罗纪氘分数的情况。这种位移归因于压力引起的线偏移,并通过基于最新线剖面参数的专用辐射传输模型进行了再现。利用大气标准模型,我们得到了 $ D/H $,它与最近在土星大气中的测量值以及从太阳风测量和陨石数据中推断出的值相吻合。这一结果表明,所有三个测量值都代表了真正的原太阳D/H分数。作为对我们模型中假设的分层一致性的补充和检验,我们对 CH$_4$ 的纯旋转 $J=6-5$ 线(在振动基态,在 $ mu$m 处)进行了分析。
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引用次数: 0
Testing cosmic anisotropy with Padé approximations and the latest Pantheon+ sample 用帕代近似和最新的 Pantheon+ 样本测试宇宙各向异性
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202450342
J.P. Hu, J. Hu, X. Jia, B. Gao, F.Y. Wang
Cosmography can be used to constrain the kinematics of the Universe in a model-independent way. In this work, we attempt to combine the Pad$ e $ approximations with the latest Pantheon+ sample to test the cosmological principle. Based on the Pad$ e $ approximations, we first applied cosmographic constraints to different-order polynomials including third-order (Pad$ e $), fourth-order (Pad$ e $), and fifth-order (Pad$ e $) ones. The statistical analyses show that the Pad$ e $ polynomial has the best performance. Its best fits are $H_ $ = 72.53pm 0.28 km s$^ $ Mpc$^ $, $q_ $, and $j_ $. By further fixing $j_ $ = 1.00, it can be found that the Pad$ e $ polynomial can describe the Pantheon+ sample better than the regular Pad$ e $ polynomial and the usual cosmological models (including the Lambda CDM, $w$CDM, CPL, and $R_h$ = ct models). Based on the Pad$ e $ ($j_ $ = 1) polynomial and the hemisphere comparison method, we tested the cosmological principle and found the preferred directions of cosmic anisotropy, such as (l, b) = (304.6$^ circ circ $) and (311.1$^ circ circ $) for $q_ $ and $H_ $, respectively. These two directions are consistent with each other at a $1 confidence level, but the corresponding results of statistical isotropy analyses including isotropy and isotropy with real positions are quite different. The statistical significance of $ is stronger than that of $q_ $; that is, 4.75sigma and 4.39sigma for isotropy and isotropy with real positions, respectively. Reanalysis with fixed $q_ = -0.55$ (corresponds to $ m $ = 0.30) gives similar results. Overall, our model-independent results provide clear indications of a possible cosmic anisotropy, which must be taken seriously. Further testing is needed to better understand this signal.
宇宙学可以用来以一种与模型无关的方式约束宇宙运动学。在这项工作中,我们尝试将Pad$ e $近似与最新的Pantheon+样本相结合,来检验宇宙学原理。在Pad$ e $近似的基础上,我们首先将宇宙学约束应用于不同阶的多项式,包括三阶(Pad$ e $)、四阶(Pad$ e $)和五阶(Pad$ e $)多项式。统计分析显示,Pad$ e $ 多项式的性能最好。通过进一步固定$j_ $ = 1.00,可以发现Pad$ e $多项式对Pantheon+样本的描述优于常规的Pad$ e $多项式和通常的宇宙学模型(包括Lambda CDM、$w$CDM、CPL和$R_h$ = ct模型)。基于Pad$ e $ ($j_ $ = 1)多项式和半球比较法,我们检验了宇宙学原理,发现了宇宙各向异性的优选方向,如(l, b) = (304.6$^ circ circ $)和(311.1$^ circ circ $)分别为$q_ $和$H_ $。这两个方向在 1 美元的置信水平下是一致的,但包括各向同性和实位各向同性在内的统计各向同性分析的相应结果却大相径庭。$ 的统计显著性强于 $q_ $;即各向同性和实位各向同性的统计显著性分别为 4.75sigma 和 4.39sigma。用固定的 $q_ = -0.55$(相当于 $ m $ = 0.30)重新分析也得到了类似的结果。总之,我们与模型无关的结果清楚地表明了可能存在的宇宙各向异性,必须认真对待。要更好地理解这一信号,还需要进一步的测试。
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引用次数: 0
Cosmic Type Ia supernova rate and constraints on supernova Ia progenitors 宇宙Ia型超新星率和Ia型超新星原生体的约束条件
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202449740
P. Palicio, F. Matteucci, M. Della Valle, E. Spitoni
Type Ia supernovae play a key role in the evolution of galaxies by polluting the interstellar medium with a fraction of iron peak elements larger than that released in the core-collapse supernova events. Their light curve, moreover, is widely used in cosmological studies as it constitutes a reliable distance indicator on extragalactic scales. Among the mechanisms proposed to explain the Type Ia supernovae (SNe), the single- and double-degenerate channels are thought to be the dominant ones, which implies a different distribution of time delays between the progenitor formation and the explosion. In this paper, we aim to determine the dominant mechanism by comparing a compilation of Type Ia SN rates with those computed from various cosmic star-formation histories coupled with different delay-time distribution functions. We also evaluate the relative contributions of both channels. By using a least-squares fitting procedure, we modeled the observations of Type Ia SN rates assuming different combinations of three recent cosmic star-formation rates and seven delay-time distributions. The goodness of these fits are statistically quantified by the $ test. For two of the three cosmic star-formation rates, the single degenerate scenario provides the most accurate explanation for the observations, while a combination of 34 single-degenerate- and 66 double-degenerate delay-time distributions is more plausible for the remaining tested cosmic star-formation rates. Though dependent on the assumed cosmic star-formation rate, we find arguments in favor of the single-degenerate model. From the theoretic point of view, at least sim 34 of the Type Ia SN must have been produced through the single-degenerate channel to account for the observations. The wide, double-degenerate mechanism slightly under-predicts the observations at redshift $z 1$, unless the cosmic SFR flattens in that regime. On the contrary, although the purely close double-degenerate scenario can be ruled out, we cannot rule out a mixed scenario with single- and double-degenerate progenitors.
Ia 型超新星在星系的演化过程中发挥着关键作用,因为它污染了星际介质,其铁峰值元素的比例大于核心坍缩超新星事件中释放的铁峰值元素的比例。此外,它们的光变曲线也被广泛用于宇宙学研究,因为它是银河系外尺度上可靠的距离指标。在解释 Ia 型超新星(SNe)的机制中,单衰变和双衰变通道被认为是最主要的,这意味着原生体形成和爆炸之间的时间延迟分布不同。在本文中,我们旨在通过比较 Ia 型 SN 的速率汇编和根据不同的宇宙恒星形成历史以及不同的延迟时间分布函数计算出的速率,来确定主导机制。我们还评估了两种渠道的相对贡献。通过使用最小二乘拟合程序,我们对Ia型SN速率的观测结果进行了建模,假设了三种近期宇宙恒星形成速率和七种延迟时间分布的不同组合。这些拟合的好坏通过 $ 检验进行统计量化。对于三种宇宙恒星形成率中的两种,单退化方案为观测提供了最准确的解释,而对于其余测试过的宇宙恒星形成率,34 种单退化和 66 种双退化延迟时间分布的组合则更为合理。尽管这取决于假定的宇宙恒星形成率,但我们发现了支持单衰变模型的论据。从理论的角度来看,至少有模拟 34 的 Ia 型 SN 必须是通过单衰变通道产生的,才能解释观测结果。宽幅双衰减机制对红移$z 1$处的观测结果的预测略显不足,除非宇宙SFR在该机制下趋于平缓。相反,虽然可以排除纯粹的近距离双蜕变情况,但我们不能排除有单蜕变和双蜕变原生体的混合情况。
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引用次数: 0
Evolutionary pathways of disk galaxies with different sizes 不同大小盘状星系的演化路径
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202450397
Hong-Chuan Ma, Min Du, Luis C. Ho, Ming-Jie Sheng, Shihong Liao
This work delves into the complex interaction between disk galaxies and their host dark matter halos. It specifically focuses on scenarios with minimal external ("nurture") influences such as mergers and substantial tidal interactions. The study uncovers the varied evolutionary paths of disk galaxies of different sizes, shaped by the initial conditions of their parent dark matter halos and subsequent internal processes. Thus, we can explore the ``nature'' of these galaxies. From the TNG50 simulation, a sample of 836 central disk galaxies with tiny stellar halos is chosen to study the inherent evolution of galaxies driven by nature. These galaxies are classified as compact, normal, or extended by referencing their locations on the mass-size ($M_ $) diagram. Scaling relations were then established to measure the correlations driven by internal mechanisms. This research demonstrates the distinctive evolutionary pathways of galaxies with different sizes in IllustrisTNG simulations, primarily driven by their nature. It is confirmed that disk galaxies inherit the angular momentum of their parent dark matter halos. More compact galaxies form earlier within halos that exhibit a lower specific angular momentum through heightened star formation during the early phase at redshifts above 2. During the later phase, the size of extended galaxies experiences more pronounced growth by accreting gas with a high angular momentum. Additionally, we reveal that many key characteristics of galaxies are linked to their mass and size: (1) compact galaxies tend to exhibit higher metal content, proportional to the potential well, $ M_ star R_ $; (2) compact galaxies host more massive bulges and black holes, along with a higher central concentration. Furthermore, our analysis indicates that galaxies of all types continue to actively engage in star formation, with no evident signs of quenching attributed to their varying sizes and angular momenta.
这项研究深入探讨了盘状星系与其宿主暗物质晕之间复杂的相互作用。它特别关注外部("孕育")影响最小的情况,如合并和大量潮汐相互作用。研究揭示了不同大小的盘状星系的不同演化路径,这些演化路径是由其母体暗物质晕的初始条件和随后的内部过程形成的。因此,我们可以探索这些星系的 "本质"。从TNG50模拟中,我们选取了836个具有微小恒星晕的中心盘星系样本,来研究星系受自然驱动的内在演化。根据这些星系在质量-大小($M_ $)图中的位置,将它们分为紧凑星系、正常星系和扩展星系。然后建立比例关系来测量内部机制驱动的相关性。这项研究表明,在IllustrisTNG模拟中,不同大小的星系有着不同的演化路径,这主要是由它们的性质所驱动的。研究证实,盘状星系继承了其母体暗物质晕的角动量。在红移超过 2 的早期阶段,恒星形成速度加快,从而在比角动量较小的光环内较早形成了更紧凑的星系。在后期阶段,扩展星系的大小会因为吸积高角动量的气体而发生更明显的增长。此外,我们还揭示了星系的许多关键特征都与它们的质量和大小有关:(1)紧凑星系往往表现出较高的金属含量,与势阱成正比,即 $ M_ star R_$;(2)紧凑星系承载着更大质量的隆起和黑洞,以及更高的中心浓度。此外,我们的分析表明,各种类型的星系都在继续积极地进行恒星形成,并没有因为它们的大小和角矩不同而出现明显的熄灭迹象。
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引用次数: 0
Considering the incidence rate of RR Lyrae stars with non-radial modes 考虑到具有非辐射模式的天琴座 RR 星的入射率
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202348964
H. Netzel, V. Varga, R. Szabo, R. Smolec, E. Plachy
Over recent years, additional low-amplitude non-radial modes have been detected in many first-overtone RR Lyrae stars. These non-radial modes form a characteristic period ratio with the dominant first overtone of around 0.61. The incidence rate of this phenomenon varies from population to population. It is also strongly dependent on the quality of the analyzed data. Current models aimed at explaining these additional signals involve non-radial modes of degrees of 8 and 9. Using synthetic horizontal branch populations, we investigate the incidence rate of first-overtone RR Lyrae stars with non-radial modes, depending on the population properties, namely, ages and metallicities. We compare our results with the observed results for globular clusters and the vast collection of field first-overtone RR Lyrae stars to test the model predictions. We used synthetic horizontal branches combined with pulsation models to predict how the incidence rate would depend on the age and metallicity of the population. To test whether the results based on synthetic horizontal branches are realistic, we compared them to incidence rates observed by TESS in first-overtone field RR Lyrae stars, using photometric metallicity values from a newly established calibration for TESS. The analysis of synthetic horizontal branches indicates that the incidence rate decreases with decreasing metallicity. We inferred the photometric metallicity for RR Lyrae stars observed by TESS and showed that the theoretical predictions are in agreement with the observations. Using the same method, we also concluded that the metallicity distribution of RR Lyrae stars showing an additional mode with a period-ratio around $0.68$ appears to be different from that of 1) all first-overtone stars and 2) those showing additional non-radial modes.
近年来,在许多天琴座RR星的第一泛音中探测到了额外的低振幅非径向模式。这些非辐射模与主要的第一泛音形成了一个特征周期比,约为 0.61。这种现象的发生率因星群而异。它还在很大程度上取决于分析数据的质量。目前旨在解释这些额外信号的模型涉及 8 度和 9 度的非辐射模式。我们利用合成的水平分支星群,研究了具有非辐射模式的天琴座RR第一叠调恒星的发生率,这取决于星群的特性,即年龄和金属性。我们将我们的结果与球状星团的观测结果和大量的野外天琴座RR第一叠加星的观测结果进行比较,以检验模型的预测结果。我们使用合成水平分支结合脉动模型来预测发生率如何取决于星群的年龄和金属性。为了检验基于合成水平分支的结果是否符合实际情况,我们将其与TESS观测到的天琴座RR星第一重叠场的入射率进行了比较,并使用了新近为TESS建立的校准中的测光金属度值。对合成水平分支的分析表明,入射率随着金属性的降低而降低。我们推断了 TESS 观测到的天琴座 RR 星的测光金属度,结果表明理论预测与观测结果一致。利用同样的方法,我们还得出结论,显示出周期比在0.68$左右的附加模式的天琴座RR星的金属性分布似乎不同于:1)所有第一叠加模式的恒星;2)显示出附加非径向模式的恒星。
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引用次数: 0
Impact of the numerical conversion to optical depth on the transfer of polarized radiation 光学深度的数值转换对偏振辐射传输的影响
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202449780
Matteo D'Anna, G. Janett, L. Belluzzi
Making the conversion from the geometrical spatial scale to the optical depth spatial scale is usefulin obtaining numerical solutions for the radiative transfer equation. This is because it allows for the use of exponential integrators,while enforcing numerical stability.Such a conversion involves the integration of the total opacity of the medium along the considered ray path.This is usually approximated by applying a piecewise quadrature in each spatial cell of the discretized medium. However, a rigorous analysis of this numerical stepis lacking. This work is aimed at clearly assessing the performance of different optical depth conversion schemeswith respect to the solution of the radiative transfer problem for polarized radiation, out of the local thermodynamic equilibrium. We analyzed different optical depth conversion schemes and their combinations with common formal solvers, bothin terms of the rate of convergence as a function of the number of spatial points and the accuracy of the emergent Stokes profiles.The analysis was performed in a 1D semi-empirical model of the solar atmosphere,both in the absence and in the presence of a magnetic field. We solved the transfer problem of polarized radiation in different settings:the continuum, the photospheric Sr i AA modeled under the assumption of complete frequency redistribution, and the chromospheric Ca i AA taking the partial frequency redistribution effects into account during the modeling. High-order conversion schemes generally outperform low-order methods when a sufficiently high number of spatial grid points is considered.In the synthesis of the emergent Stokes profiles, the convergence rate, as a function of the number of spatial points, is impacted by both the conversion scheme and formal solver.The use of low-order conversion schemes significantly reduces the accuracy of high-order formal solvers. In practical applications, the use of low-order optical depth conversion schemesintroduces large numerical errors in the formal solution.To fully exploit high-order formal solvers and obtain accurate synthetic emergent Stokes profiles,it is necessary to use high-order optical depth conversion schemes.
将几何空间尺度转换为光学深度空间尺度有助于获得辐射传递方程的数值解。这种转换涉及沿所考虑的射线路径对介质的总不透明度进行积分,通常通过在离散介质的每个空间单元中应用分段正交来近似实现。然而,目前还缺乏对这一数值步骤的严格分析。这项工作旨在明确评估不同光学深度转换方案在解决偏振辐射辐射传递问题方面的性能,以及在局部热力学平衡状态下的性能。我们分析了不同的光学深度转换方案及其与普通形式求解器的组合,包括作为空间点数量函数的收敛速度和出现的斯托克斯剖面的精确度。我们在不同的环境中解决了偏振辐射的转移问题:连续体、在完全频率再分布假设下建模的光球层 Sr i AA,以及在建模过程中考虑了部分频率再分布效应的色球层 Ca i AA。在合成新出现的斯托克斯剖面时,收敛速度作为空间点数的函数,受到转换方案和形式求解器的影响。在实际应用中,使用低阶光学深度转换方案会在形式解中产生较大的数值误差。要充分利用高阶形式解算器并获得精确的合成新兴斯托克斯剖面,就必须使用高阶光学深度转换方案。
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引用次数: 0
Evolution of the star formation rate and Sigma_SFR of galaxies at cosmic morning (4 星系的恒星形成率和 Sigma_SFR 在宇宙晨的演变(4
Pub Date : 2024-07-24 DOI: 10.1051/0004-6361/202449768
A. Calabrò, L. Pentericci, P. Santini, A. Ferrara, M. Llerena, S. Mascia, L. Napolitano, L. Yung, L. Bisigello, M. Castellano, N. Cleri, A. Dekel, M. Dickinson, M. Franco, M. Giavalisco, M. Hirschmann, B. Holwerda, A. Koekemoer, R. A. Lucas, F. Pacucci, N. Pirzkal, G. Roberts-Borsani, L. Seillé, S. Tacchella, S. Wilkins, R. Amor'in, P. Arrabal Haro, M. Bagley, S. Finkelstein, J. Kartaltepe, C. Papovich
The galaxy-integrated star formation rate (SFR) surface density measurement ($ SFR $) has been proposed as a valuable diagnostic of the mass accumulation in galaxies given it is more tightly related to the physics of star formation and stellar feedback than other indicators. In this work, we assembled a statistical sample of $230$ galaxies observed with JWST in the GLASS and CEERS spectroscopic surveys to estimate Balmer line-based dust attenuations and SFRs (i.e., from Halpha , Hbeta , and Hgamma ), along with the UV rest-frame effective radii. We studied the evolution of galaxy SFR and $ SFR $ in the first $1.5$ billion years of our Universe, from a redshift of $z to $z We found that $ SFR $ is mildly increasing with redshift with a linear slope of $0.16 0.06$. We explored the dependence of SFR and $ SFR $ on stellar mass, showing that a star-forming main sequence and a $ SFR $ main sequence are present out to $z=10$. This dependence exhibits a similar slope compared to the same relations at lower redshifts, but with a higher normalization. We find that the specific SFR (sSFR) and $ SFR $ are correlated with the ratio and with indirect estimates of the escape fraction of Lyman continuum photons; hence, they are likely to play an important role in the evolution of ionization conditions at higher redshifts and in the escape of ionizing radiation. We also searched for spectral outflow signatures in the Halpha and emission lines in a subset of galaxies observed at high resolution (R$=2700$) by the GLASS survey, finding an outflow incidence of $2/11$ 32 9 $) at $z<6$, but no evidence at $z>6$ ($0/6$, $<26$). Finally, we find a positive correlation between A$_V$ and $ SFR $, and a flat trend as a function of sSFR, indicating that there is no evidence of a drop in A$_V$ in extremely star-forming galaxies between $z 4$ and $ 10$. This result might be at odds with a dust-clearing outflow scenario, which may instead take place at redshifts of $z 10$, as suggested by some theoretical models.
星系综合恒星形成率(SFR)表面密度测量($ SFR $)被认为是星系质量积累的重要诊断指标,因为它比其他指标与恒星形成和恒星反馈物理学的关系更紧密。在这项工作中,我们收集了JWST在GLASS和CEERS光谱巡天中观测到的230美元星系的统计样本,以估算基于巴尔默线的尘埃衰减和SFR(即来自Halpha、Hbeta和Hgamma),以及紫外静帧有效半径。我们研究了星系SFR和$ SFR $在宇宙最初15亿年的演化,从红移$z到$z 我们发现$ SFR $随着红移轻微增加,线性斜率为$0.16 0.06$。我们还探讨了 SFR 和 SFR $ 与恒星质量的关系,结果表明恒星形成主序和 SFR $ 主序在 $z=10 $ 时都存在。与较低红移下的相同关系相比,这种依赖关系表现出相似的斜率,但归一化程度更高。我们发现,比 SFR(sSFR)和 $ SFR $ 与莱曼连续光子逸出分数的比率和间接估计值相关;因此,它们很可能在较高红移下电离条件的演变和电离辐射的逸出中发挥重要作用。我们还在 GLASS 勘测以高分辨率(R$=2700$)观测到的星系子集中搜索了 Halpha 和发射线中的光谱外流特征,发现在 $z6$ 时外流发生率为 2/11$ 32 9$($0/6$, $<26$)。最后,我们发现A$_V$和$SFR$之间存在正相关关系,并且与sSFR的函数关系趋于平稳,这表明在$z 4$到$10$之间的极高恒星形成星系中,没有证据表明A$_V$会下降。这一结果可能与尘埃清除外流的情况不符,正如一些理论模型所建议的那样,尘埃清除外流可能发生在红移 $z 10$的时候。
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引用次数: 0
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Astronomy &amp; Astrophysics
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