Pub Date : 2024-09-13DOI: 10.1051/0004-6361/202449586
N. Dvořáková, D. Korčáková, F. Dinnbier, P. Kroupa
Context. FS CMa stars belong to a diverse group of stars exhibiting the B[e] phenomenon, which manifests itself mainly by the presence of forbidden emission lines and a strong infrared (IR) excess in their spectra. Only a few tens of FS CMa stars are known and their nature is still unclear. Recently, a strong magnetic field has been discovered in the FS CMa star IRAS 17449+2320. Its strength combined with an unusually high space velocity in the direction of the Galactic north pole point to the object having a post-merger nature. Such stellar mergers may provide an explanation for the complex and sometimes chaotic behaviour of some of the FS CMa stars.Aims. In order to find out whether B-type stellar mergers are detectable, we did a statistical study of numerical simulations using Aarseth’s NBODY6 code. We show the importance of stellar mergers of low- to intermediate-mass stars (from ≈1.4 to ≈8 M⊙) and for B-type stars in particular.Methods. We analysed two sets of N-body simulations with different initial orbital period distributions. In the simulations, more massive binaries are treated differently than less massive binaries and the mass limit usually used is 5 M⊙. In addition to this, we also used the value of 2 M⊙ to test the influence of this ambiguous limit on the results. Looking at mass, distance from their birth cluster, and velocity distributions, we investigated the statistical significance of individual spectral types in terms of merger dynamics and how merger events affect the stellar evolution.Results. We have found that around 50% of stars in the simulated open clusters involved in the formation of mergers are B-type stars. As a result, more than 50% of the merger products end up as a B-type star as well. Also, between 12.54% and 23.24% of all B-type stars are mergers. These results are a natural consequence of the initial mass function, initial distribution of the binary star parameters, and large range of masses for B-type stars. A non-negligible fraction of mergers occurred before entering the common envelope phase and we detected merger events at extragalactic distances. The total amount of detected mergers could have an impact on the chemical evolution of galaxies. The resulting mass distribution of merger products shows a peak for A-type stars, which is in agreement with observed massive Ap stars. Post-mergers among late B-type FS CMa stars could be the progenitors of very massive magnetic Ap stars. our results could also help to explain the nature of some magnetic white dwarfs. We present a comparison of the W component and the space velocity of the simulated mergers with a sample of observed FS CMa stars.
背景FS CMa恒星属于表现出B[e]现象的恒星中的一类，其主要表现为光谱中存在禁止发射线和强烈的红外（IR）过量。目前已知的 FS CMa 星只有几十颗，它们的性质还不清楚。最近，在 FS CMa 星 IRAS 17449+2320 中发现了一个强磁场。强磁场的强度加上银河系北极方向上异常高的空间速度表明该天体具有合并后的性质。这种恒星合并可以解释一些FS CMa恒星的复杂和有时混乱的行为。 目的：为了找出B型恒星合并是否可以被探测到，我们使用Aarseth的NBODY6代码进行了数值模拟统计研究。我们显示了中低质量恒星（从≈1.4到≈8 M⊙），尤其是B型恒星合并的重要性。我们分析了两组具有不同初始轨道周期分布的N-体模拟。在模拟中，质量较大的双星与质量较小的双星的处理方法不同，通常使用的质量极限是5 M⊙。除此以外，我们还使用了 2 M⊙的值来测试这一模糊极限对结果的影响。通过观察质量、与诞生星团的距离以及速度分布，我们研究了单个光谱类型在合并动力学方面的统计意义，以及合并事件如何影响恒星演化。我们发现，在参与合并形成的模拟疏散星团中，大约 50%的恒星是 B 型恒星。因此，超过50%的合并产物最终也是B型恒星。另外，在所有 B 型恒星中，有 12.54% 到 23.24% 是合并的。这些结果是初始质量函数、双星参数的初始分布以及B型恒星质量范围大的自然结果。不可忽略的一部分合并发生在进入共同包层阶段之前，我们在河外星系距离上探测到了合并事件。检测到的合并总量可能会对星系的化学演化产生影响。合并产物的质量分布显示出 A 型恒星的峰值，这与观测到的大质量 Ap 星一致。晚期B型FS CMa恒星的合并后产物可能是质量非常大的磁性Ap恒星的祖先。我们的研究结果也有助于解释一些磁性白矮星的性质。我们将模拟合并的 W 分量和空间速度与观测到的 FS CMa 星样本进行了比较。
{"title":"The mass distribution of stellar mergers","authors":"N. Dvořáková, D. Korčáková, F. Dinnbier, P. Kroupa","doi":"10.1051/0004-6361/202449586","DOIUrl":"https://doi.org/10.1051/0004-6361/202449586","url":null,"abstract":"<i>Context<i/>. FS CMa stars belong to a diverse group of stars exhibiting the B[e] phenomenon, which manifests itself mainly by the presence of forbidden emission lines and a strong infrared (IR) excess in their spectra. Only a few tens of FS CMa stars are known and their nature is still unclear. Recently, a strong magnetic field has been discovered in the FS CMa star IRAS 17449+2320. Its strength combined with an unusually high space velocity in the direction of the Galactic north pole point to the object having a post-merger nature. Such stellar mergers may provide an explanation for the complex and sometimes chaotic behaviour of some of the FS CMa stars.<i>Aims<i/>. In order to find out whether B-type stellar mergers are detectable, we did a statistical study of numerical simulations using Aarseth’s NBODY6 code. We show the importance of stellar mergers of low- to intermediate-mass stars (from ≈1.4 to ≈8 M<sub>⊙<sub/>) and for B-type stars in particular.<i>Methods<i/>. We analysed two sets of N-body simulations with different initial orbital period distributions. In the simulations, more massive binaries are treated differently than less massive binaries and the mass limit usually used is 5 M<sub>⊙<sub/>. In addition to this, we also used the value of 2 M<sub>⊙<sub/> to test the influence of this ambiguous limit on the results. Looking at mass, distance from their birth cluster, and velocity distributions, we investigated the statistical significance of individual spectral types in terms of merger dynamics and how merger events affect the stellar evolution.<i>Results<i/>. We have found that around 50% of stars in the simulated open clusters involved in the formation of mergers are B-type stars. As a result, more than 50% of the merger products end up as a B-type star as well. Also, between 12.54% and 23.24% of all B-type stars are mergers. These results are a natural consequence of the initial mass function, initial distribution of the binary star parameters, and large range of masses for B-type stars. A non-negligible fraction of mergers occurred before entering the common envelope phase and we detected merger events at extragalactic distances. The total amount of detected mergers could have an impact on the chemical evolution of galaxies. The resulting mass distribution of merger products shows a peak for A-type stars, which is in agreement with observed massive Ap stars. Post-mergers among late B-type FS CMa stars could be the progenitors of very massive magnetic Ap stars. our results could also help to explain the nature of some magnetic white dwarfs. We present a comparison of the W component and the space velocity of the simulated mergers with a sample of observed FS CMa stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142234251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-13DOI: 10.1051/0004-6361/202347928
Moritz Haslbauer, Zhiqiang Yan, Tereza Jerabkova, Eda Gjergo, Pavel Kroupa, Akram Hasani Zonoozi
Context. Observational estimates of galaxy properties, including mass and star formation rates (SFRs), rely on the inherent galaxy-wide initial mass function (gwIMF), which systematically varies with the global SFR and metallicity, as proposed by the integrated-galactic IMF (IGIMF) theory and supported by empirical evidence.Aims. We aim to evaluate the influence of the variable gwIMF on various galaxy properties, encompassing the Ks-, K3.6-, and V-band stellar mass-to-light ratio, SFR–luminosity relation, gas depletion timescale, and stellar mass buildup timescale of local star-forming galaxies.Methods. We incorporate PARSEC and COLIBRI stellar isochrones into the GalIMF code, a galaxy chemical evolution (GCE) model featuring real-time updates of environment-dependent gwIMFs. This newly developed photometric GalIMF (photGalIMF) code allows the calculation of photometric properties for galaxies with diverse stellar populations. Subsequently, we analyze observed luminosities and metallicities of local star-forming galaxies to deduce their stellar masses assuming empirically-motivated SFHs of Local Cosmological Volume galaxies. We also compute SFR–Hα luminosity relations for varying stellar metallicities using a separate stellar population synthesis code based on PÉGASE.Results. Comparing the IGIMF theory to the canonical universal IMF, our analysis reveals that estimates of the stellar masses and SFRs for local star-forming galaxies differ by factors of approximately 2 and 10, respectively. This disparity yields a well-defined galaxy main sequence extending to dwarf galaxies. The computed gas-depletion timescale increases with gas mass, implying lower star formation efficiencies in more massive galaxies, possibly due to stronger feedback regulation, aligning with theoretical expectations. Additionally, the characteristic stellar mass buildup timescale increases with stellar mass, indicating that massive disk galaxies initiate star formation earlier than their low-mass counterparts.Conclusions. The photGalIMF code enables self-consistent computations of galactic photometry with GCE modelling adopting an environment-dependent gwIMF. Utilizing K-band and Hα luminosities of galaxies, the outcomes include galaxy mass, SFR, and fitting functions for the SFR correction factor.
{"title":"The effect of the environment-dependent stellar initial mass function on the photometric properties of star-forming galaxies","authors":"Moritz Haslbauer, Zhiqiang Yan, Tereza Jerabkova, Eda Gjergo, Pavel Kroupa, Akram Hasani Zonoozi","doi":"10.1051/0004-6361/202347928","DOIUrl":"https://doi.org/10.1051/0004-6361/202347928","url":null,"abstract":"<i>Context.<i/> Observational estimates of galaxy properties, including mass and star formation rates (SFRs), rely on the inherent galaxy-wide initial mass function (gwIMF), which systematically varies with the global SFR and metallicity, as proposed by the integrated-galactic IMF (IGIMF) theory and supported by empirical evidence.<i>Aims.<i/> We aim to evaluate the influence of the variable gwIMF on various galaxy properties, encompassing the <i>Ks<i/>-, <i>K<i/><sub>3.6<sub/>-, and <i>V<i/>-band stellar mass-to-light ratio, SFR–luminosity relation, gas depletion timescale, and stellar mass buildup timescale of local star-forming galaxies.<i>Methods.<i/> We incorporate PARSEC and COLIBRI stellar isochrones into the GalIMF code, a galaxy chemical evolution (GCE) model featuring real-time updates of environment-dependent gwIMFs. This newly developed photometric GalIMF (photGalIMF) code allows the calculation of photometric properties for galaxies with diverse stellar populations. Subsequently, we analyze observed luminosities and metallicities of local star-forming galaxies to deduce their stellar masses assuming empirically-motivated SFHs of Local Cosmological Volume galaxies. We also compute SFR–H<i>α<i/> luminosity relations for varying stellar metallicities using a separate stellar population synthesis code based on PÉGASE.<i>Results.<i/> Comparing the IGIMF theory to the canonical universal IMF, our analysis reveals that estimates of the stellar masses and SFRs for local star-forming galaxies differ by factors of approximately 2 and 10, respectively. This disparity yields a well-defined galaxy main sequence extending to dwarf galaxies. The computed gas-depletion timescale increases with gas mass, implying lower star formation efficiencies in more massive galaxies, possibly due to stronger feedback regulation, aligning with theoretical expectations. Additionally, the characteristic stellar mass buildup timescale increases with stellar mass, indicating that massive disk galaxies initiate star formation earlier than their low-mass counterparts.<i>Conclusions.<i/> The photGalIMF code enables self-consistent computations of galactic photometry with GCE modelling adopting an environment-dependent gwIMF. Utilizing <i>K<i/>-band and H<i>α<i/> luminosities of galaxies, the outcomes include galaxy mass, SFR, and fitting functions for the SFR correction factor.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142234282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-13DOI: 10.1051/0004-6361/202450244
H. George, D. M. Malaspina, D. Lee-Bellows, L. C. Gasque, K. Goodrich, Y. Ma, S. Curry
Context. Parker Solar Probe (PSP) performs Venus gravity assists (VGAs) in order to lower its perihelion. PSP takes high-cadence electric and magnetic field observations during these VGAs, providing the opportunity to study plasma waves in Venus’s induced magnetosphere.Aims. We summarize the plasma environment during these VGAs, including the regions of near-Venus space that PSP traversed and the key boundary crossings. We comprehensively identify Langmuir, ion acoustic, whistler-mode, and ion cyclotron waves during these VGAs and map the location of these waves throughout near-Venus space.Methods. This study analyzes different data products from the PSP FIELDS instrument suite from throughout the first five VGAs.Results. We compare the FIELDS instrumentation capabilities to the capabilities of the plasma wave instruments on board the Pioneer Venus Orbiter (PVO) and the Venus Express (VEX). We find that the PVO electric field instrument was well suited to observe Langmuir waves, especially near the bow shock and in the foreshock. However, evaluation of the other plasma waves detected by PSP FIELDS reveals that PVO and VEX would have often been unable to observe key features of these waves modes, including maximum power, bandwidth, and propagation direction. These wave characteristics provide critical information on the wave generation mechanisms and wave-particle interactions, so provide fundamental information on the nature of Venus’s induced magnetosphere.Conclusions. These results highlight the advances in plasma wave instrumentation capabilities that have been made in the decades since the PVO and VEX eras, and illustrate the value of a plasma wave instrument on a new Venus mission.
{"title":"Plasma wave survey from Parker Solar Probe observations during Venus gravity assists","authors":"H. George, D. M. Malaspina, D. Lee-Bellows, L. C. Gasque, K. Goodrich, Y. Ma, S. Curry","doi":"10.1051/0004-6361/202450244","DOIUrl":"https://doi.org/10.1051/0004-6361/202450244","url":null,"abstract":"<i>Context<i/>. Parker Solar Probe (PSP) performs Venus gravity assists (VGAs) in order to lower its perihelion. PSP takes high-cadence electric and magnetic field observations during these VGAs, providing the opportunity to study plasma waves in Venus’s induced magnetosphere.<i>Aims<i/>. We summarize the plasma environment during these VGAs, including the regions of near-Venus space that PSP traversed and the key boundary crossings. We comprehensively identify Langmuir, ion acoustic, whistler-mode, and ion cyclotron waves during these VGAs and map the location of these waves throughout near-Venus space.<i>Methods<i/>. This study analyzes different data products from the PSP FIELDS instrument suite from throughout the first five VGAs.<i>Results<i/>. We compare the FIELDS instrumentation capabilities to the capabilities of the plasma wave instruments on board the Pioneer Venus Orbiter (PVO) and the Venus Express (VEX). We find that the PVO electric field instrument was well suited to observe Langmuir waves, especially near the bow shock and in the foreshock. However, evaluation of the other plasma waves detected by PSP FIELDS reveals that PVO and VEX would have often been unable to observe key features of these waves modes, including maximum power, bandwidth, and propagation direction. These wave characteristics provide critical information on the wave generation mechanisms and wave-particle interactions, so provide fundamental information on the nature of Venus’s induced magnetosphere.<i>Conclusions<i/>. These results highlight the advances in plasma wave instrumentation capabilities that have been made in the decades since the PVO and VEX eras, and illustrate the value of a plasma wave instrument on a new Venus mission.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142234281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-12DOI: 10.1051/0004-6361/202451423
Mika Juvela
Context. Radiative transfer (RT) modelling is a necessary tool in the interpretation of observations of the thermal emission of interstellar dust. It is also often part of multi-physics modelling. In this context, the efficiency of radiative transfer calculations is important, even for one-dimensional models.Aims. We investigate the use of the so-called immediate re-emission (IRE) method for fast calculation of one-dimensional spherical cloud models. We wish to determine whether weighting methods similar to those used in traditional Monte Carlo simulations can speed up the estimation of dust temperature.Methods. We present the program DIES, a parallel implementation of the IRE method, which makes it possible to do the calculations also on graphics processing units (GPUs). We tested the program with externally and internally heated cloud models, and examined the potential improvements from the use of different weighted sampling schemes.Results. The execution times of the program compare favourably with previous programs, especially when run on GPUs. On the other hand, weighting schemes produce only limited improvements. In the case of an internal radiation source, the basic IRE method samples the re-emission well, while traditional Monte Carlo requires the use of spatial importance sampling. Some noise reduction could be achieved for externally heated models by weighting the initial photon directions. Only in optically very thin models does weighting – such as the proposed method of forced first interaction – result in noise reduction by a factor of several.Conclusions. The IRE method performs well for both internally and externally heated models, typically without the need for any additional weighting schemes. With run times of the order of one second for our test models, the DIES program is suitable even for larger parameter studies.
{"title":"DIES: Parallel dust radiative transfer program with the immediate re-emission method","authors":"Mika Juvela","doi":"10.1051/0004-6361/202451423","DOIUrl":"https://doi.org/10.1051/0004-6361/202451423","url":null,"abstract":"<i>Context<i/>. Radiative transfer (RT) modelling is a necessary tool in the interpretation of observations of the thermal emission of interstellar dust. It is also often part of multi-physics modelling. In this context, the efficiency of radiative transfer calculations is important, even for one-dimensional models.<i>Aims<i/>. We investigate the use of the so-called immediate re-emission (IRE) method for fast calculation of one-dimensional spherical cloud models. We wish to determine whether weighting methods similar to those used in traditional Monte Carlo simulations can speed up the estimation of dust temperature.<i>Methods<i/>. We present the program DIES, a parallel implementation of the IRE method, which makes it possible to do the calculations also on graphics processing units (GPUs). We tested the program with externally and internally heated cloud models, and examined the potential improvements from the use of different weighted sampling schemes.<i>Results<i/>. The execution times of the program compare favourably with previous programs, especially when run on GPUs. On the other hand, weighting schemes produce only limited improvements. In the case of an internal radiation source, the basic IRE method samples the re-emission well, while traditional Monte Carlo requires the use of spatial importance sampling. Some noise reduction could be achieved for externally heated models by weighting the initial photon directions. Only in optically very thin models does weighting – such as the proposed method of forced first interaction – result in noise reduction by a factor of several.<i>Conclusions<i/>. The IRE method performs well for both internally and externally heated models, typically without the need for any additional weighting schemes. With run times of the order of one second for our test models, the DIES program is suitable even for larger parameter studies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-12DOI: 10.1051/0004-6361/202450399
Maryna Ishchenko, Peter Berczik, Taras Panamarev, Dana Kuvatova, Mukhagali Kalambay, Anton Gluchshenko, Oleksandr Veles, Margaryta Sobolenko, Olexander Sobodar, Chingis Omarov
Context. Based on the Gaia DR3, we reconstructed the orbital evolution of the known Milky Way globular clusters and found that six objects, NGC 6681, NGC 6981, Palomar 6, NGC 6642, HP 1, and NGC 1904, very likely interact closely with the nuclear star cluster.Aims. We study the dynamical evolution of selected Milky Way globular clusters and their interactions with the Galactic centre over cosmological timescales. We examine the global dynamical mass loss of these globular cluster systems, their close interactions with the Galactic centre, and the potential capture of stars by the Milky Way nuclear star cluster.Methods. For the dynamical modelling of the clusters, we used the parallel N-body code φ-GPU, which allows star-by-star simulations of the systems. Our current code also enabled us to follow the stellar evolution of individual particles, including the formation of high-mass remnants. The modelling was carried out in a Milky Way-like, time-variable potential (with a dynamically changing mass and scale length), obtained from the IllustrisTNG-100 database, with a full integration time of eight billion years.Results. Based on extensive numerical modelling and analysis, we estimated the mass loss and the global and inner structures of the selected six clusters. Over an evolution of eight billion years, the clusters lost ≈80% of their initial mass. We analysed the phase-space evolution of the individual unbound stars NGC 6681, NGC 6642, HP 1, and NGC 1904. We found that only NGC 6642 could potentially have been a source for populating the Milky Way nuclear star cluster in the past.
背景。基于盖亚DR3，我们重建了已知银河球状星团的轨道演化，发现NGC 6681、NGC 6981、Palomar 6、NGC 6642、HP 1和NGC 1904这六个天体很可能与核星团有密切的相互作用。我们研究了部分银河系球状星团的动力学演化及其在宇宙学时间尺度上与银河系中心的相互作用。我们研究了这些球状星团系统的全球动态质量损失、它们与银河中心的密切相互作用以及银河核星团对恒星的潜在捕获。为了建立球状星团的动力学模型，我们使用了并行 N-body 代码 φ-GPU，它可以对系统进行逐星模拟。我们目前的代码还可以跟踪单个粒子的恒星演化，包括高质残余物的形成。建模是在类似银河系的时变势能（质量和尺度长度动态变化）中进行的，该势能来自 IllustrisTNG-100 数据库，完整的积分时间为 80 亿年。基于大量的数值建模和分析，我们估算了所选六个星团的质量损失以及整体和内部结构。在80亿年的演化过程中，这些星团的质量损失≈80%。我们分析了 NGC 6681、NGC 6642、HP 1 和 NGC 1904 等单个非束缚恒星的相空间演化。我们发现，只有 NGC 6642 有可能是过去银河系核星团的填充源。
{"title":"Dynamical evolution of Milky Way globular clusters on the cosmological timescale","authors":"Maryna Ishchenko, Peter Berczik, Taras Panamarev, Dana Kuvatova, Mukhagali Kalambay, Anton Gluchshenko, Oleksandr Veles, Margaryta Sobolenko, Olexander Sobodar, Chingis Omarov","doi":"10.1051/0004-6361/202450399","DOIUrl":"https://doi.org/10.1051/0004-6361/202450399","url":null,"abstract":"<i>Context.<i/> Based on the <i>Gaia<i/> DR3, we reconstructed the orbital evolution of the known Milky Way globular clusters and found that six objects, NGC 6681, NGC 6981, Palomar 6, NGC 6642, HP 1, and NGC 1904, very likely interact closely with the nuclear star cluster.<i>Aims.<i/> We study the dynamical evolution of selected Milky Way globular clusters and their interactions with the Galactic centre over cosmological timescales. We examine the global dynamical mass loss of these globular cluster systems, their close interactions with the Galactic centre, and the potential capture of stars by the Milky Way nuclear star cluster.<i>Methods.<i/> For the dynamical modelling of the clusters, we used the parallel <i>N<i/>-body code <i>φ<i/>-GPU, which allows star-by-star simulations of the systems. Our current code also enabled us to follow the stellar evolution of individual particles, including the formation of high-mass remnants. The modelling was carried out in a Milky Way-like, time-variable potential (with a dynamically changing mass and scale length), obtained from the IllustrisTNG-100 database, with a full integration time of eight billion years.<i>Results.<i/> Based on extensive numerical modelling and analysis, we estimated the mass loss and the global and inner structures of the selected six clusters. Over an evolution of eight billion years, the clusters lost ≈80% of their initial mass. We analysed the phase-space evolution of the individual unbound stars NGC 6681, NGC 6642, HP 1, and NGC 1904. We found that only NGC 6642 could potentially have been a source for populating the Milky Way nuclear star cluster in the past.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142174593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-11DOI: 10.1051/0004-6361/202451635
Klaus Werner, Kareem El-Badry, Boris T. Gänsicke, Ken J. Shen
The hot white dwarf (WD) J0927−6335 (Gaia DR3 5250394728194220800 with an effective temperature of Teff = 60 000 K and a surface gravity of logg = 7) was detected as the fastest known Galactic hypervelocity star with a space velocity of ≈2800 km s−1 and an atmosphere dominated by carbon and oxygen. It is thought to be the surviving WD donor predicted by the so-called dynamically driven double-degenerate double-detonation (D6) type Ia supernova formation model. We analysed an ultraviolet spectrum of J0927−6335 that was recently obtained with the Hubble Space Telescope and found very high abundances of iron and nickel. This might originate in the pollution of the remnant by the supernova Ia explosion, but it is uncertain to which extent atomic diffusion altered the chemical composition of the accreted material.
热白矮星（WD）J0927-6335（Gaia DR3 5250394728194220800，有效温度为 Teff = 60 000 K，表面重力为 logg = 7）是已知银河系超高速恒星中速度最快的一颗，空间速度≈2800 km s-1，大气中主要是碳和氧。它被认为是所谓的动力学驱动双退行性双爆破（D6）Ia型超新星形成模型所预测的幸存的WD供体。我们分析了最近用哈勃太空望远镜获得的J0927-6335的紫外光谱，发现铁和镍的丰度非常高。这可能源于 Ia 型超新星爆炸对残留物的污染，但目前还不能确定原子扩散在多大程度上改变了吸积物质的化学成分。
{"title":"Ultraviolet spectroscopy of the supernova Ia hypervelocity runaway white dwarf J0927−6335","authors":"Klaus Werner, Kareem El-Badry, Boris T. Gänsicke, Ken J. Shen","doi":"10.1051/0004-6361/202451635","DOIUrl":"https://doi.org/10.1051/0004-6361/202451635","url":null,"abstract":"The hot white dwarf (WD) J0927−6335 (Gaia DR3 5250394728194220800 with an effective temperature of <i>T<i/><sub>eff<sub/> = 60 000 K and a surface gravity of log<i>g<i/> = 7) was detected as the fastest known Galactic hypervelocity star with a space velocity of ≈2800 km s<sup>−1<sup/> and an atmosphere dominated by carbon and oxygen. It is thought to be the surviving WD donor predicted by the so-called dynamically driven double-degenerate double-detonation (D<sup>6<sup/>) type Ia supernova formation model. We analysed an ultraviolet spectrum of J0927−6335 that was recently obtained with the <i>Hubble<i/> Space Telescope and found very high abundances of iron and nickel. This might originate in the pollution of the remnant by the supernova Ia explosion, but it is uncertain to which extent atomic diffusion altered the chemical composition of the accreted material.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142170665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-10DOI: 10.1051/0004-6361/202450694
Luca Tortorelli, Jamie McCullough, Daniel Gruen
Context. The forward modelling of galaxy surveys has recently gathered interest as one of the primary methods to achieve the required precision on the estimate of the redshift distributions for stage IV surveys, allowing them to perform cosmological tests with unprecedented accuracy. One of the key aspects of forward modelling a galaxy survey is the connection between the physical properties drawn from a galaxy population model and the intrinsic galaxy spectral energy distributions (SEDs), achieved through stellar population synthesis (SPS) codes (e.g. FSPS). However, SPS requires a large number of detailed assumptions on the constituents of galaxies, for which the model choice or parameter values are currently uncertain.Aims. In this work, we perform a sensitivity study of the impact that the variations of the SED modelling choices have on the mean and scatter of the tomographic galaxy redshift distributions.Methods. We assumed the PROSPECTOR-β model as the fiducial input galaxy population model and used its SPS parameters to build 9-bands ugriZYJHKs observed-frame magnitudes of a fiducial sample of galaxies. We then built samples of galaxy magnitudes by varying one SED modelling choice at a time. We modelled the colour-redshift relation of these galaxy samples using the self-organising map (SOM) approach that optimally groups similar redshifts galaxies by their multidimensional colours. We placed galaxies in the SOM cells according to their simulated observed-frame colours and used their cell assignment to build colour-selected tomographic bins. Finally, we compared each variant’s binned redshift distributions against the estimates obtained for the original PROSPECTOR-β model.Results. We find that the SED components related to the initial mass function, as well as the active galactic nuclei, the gas physics, and the attenuation law substantially bias the mean and the scatter of the tomographic redshift distributions with respect to those estimated with the fiducial model.Conclusions. For the uncertainty of these choices currently present in the literature and regardless of the applied stellar mass function based re-weighting strategy, the bias in the mean and the scatter of the tomographic redshift distributions are greater than the precision requirements set by next-generation Stage IV galaxy surveys, such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) and Euclid.
背景星系巡天的前向建模最近引起了人们的兴趣，它是第四阶段巡天对红移分布的估计达到所要求的精度的主要方法之一，使它们能够以前所未有的精度进行宇宙学检验。对星系巡天进行前向建模的关键之一，是将星系种群模型得出的物理特性与固有的星系光谱能量分布（SED）联系起来，通过恒星种群合成（SPS）代码（如 FSPS）来实现。然而，SPS 需要对星系的组成成分做出大量详细的假设，而这些假设的模型选择或参数值目前还不确定。 在这项工作中，我们对 SED 建模选择的变化对断层星系红移分布的平均值和散度的影响进行了敏感性研究。我们假定 PROSPECTOR-β 模型为基本输入星系群模型，并使用它的 SPS 参数建立了一个基本星系样本的 9 波段 ugriZYJHKs 观测框架星等。然后，我们通过每次改变一个 SED 建模选择来建立星系星等样本。我们利用自组织图（SOM）方法对这些星系样本的颜色-红移关系进行建模，这种方法通过星系的多维颜色对类似的红移星系进行优化分组。我们根据星系的模拟观测框颜色，将星系置于自组织图单元中，并利用它们的单元分配来建立颜色选择的层析箱。最后，我们将每个变体的分档红移分布与原始 PROSPECTOR-β 模型的估计值进行了比较。我们发现，与初始质量函数以及活动星系核、气体物理和衰减定律有关的 SED 成分，与用固定模型估算的结果相比，在很大程度上偏离了层析红移分布的平均值和散度。就目前文献中这些选择的不确定性而言，无论采用基于恒星质量函数的再加权策略，层析红移分布的平均值和散度偏差都大于下一代第四阶段星系巡天所设定的精度要求，如 Vera C. Rubin 天文台的时空遗留巡天（LSST）和 Euclid。
{"title":"Impact of stellar population synthesis choices on forward modelling-based redshift distribution estimates","authors":"Luca Tortorelli, Jamie McCullough, Daniel Gruen","doi":"10.1051/0004-6361/202450694","DOIUrl":"https://doi.org/10.1051/0004-6361/202450694","url":null,"abstract":"<i>Context.<i/> The forward modelling of galaxy surveys has recently gathered interest as one of the primary methods to achieve the required precision on the estimate of the redshift distributions for stage IV surveys, allowing them to perform cosmological tests with unprecedented accuracy. One of the key aspects of forward modelling a galaxy survey is the connection between the physical properties drawn from a galaxy population model and the intrinsic galaxy spectral energy distributions (SEDs), achieved through stellar population synthesis (SPS) codes (e.g. FSPS). However, SPS requires a large number of detailed assumptions on the constituents of galaxies, for which the model choice or parameter values are currently uncertain.<i>Aims.<i/> In this work, we perform a sensitivity study of the impact that the variations of the SED modelling choices have on the mean and scatter of the tomographic galaxy redshift distributions.<i>Methods.<i/> We assumed the PROSPECTOR-<i>β<i/> model as the fiducial input galaxy population model and used its SPS parameters to build 9-bands <i>ugriZYJHK<i/><sub><i>s<i/><sub/> observed-frame magnitudes of a fiducial sample of galaxies. We then built samples of galaxy magnitudes by varying one SED modelling choice at a time. We modelled the colour-redshift relation of these galaxy samples using the self-organising map (SOM) approach that optimally groups similar redshifts galaxies by their multidimensional colours. We placed galaxies in the SOM cells according to their simulated observed-frame colours and used their cell assignment to build colour-selected tomographic bins. Finally, we compared each variant’s binned redshift distributions against the estimates obtained for the original PROSPECTOR-<i>β<i/> model.<i>Results.<i/> We find that the SED components related to the initial mass function, as well as the active galactic nuclei, the gas physics, and the attenuation law substantially bias the mean and the scatter of the tomographic redshift distributions with respect to those estimated with the fiducial model.<i>Conclusions.<i/> For the uncertainty of these choices currently present in the literature and regardless of the applied stellar mass function based re-weighting strategy, the bias in the mean and the scatter of the tomographic redshift distributions are greater than the precision requirements set by next-generation Stage IV galaxy surveys, such as the <i>Vera C. Rubin<i/> Observatory’s Legacy Survey of Space and Time (LSST) and <i>Euclid<i/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142166255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-06DOI: 10.1051/0004-6361/202347568
I. Bešlić, A. T. Barnes, F. Bigiel, M. J. Jiménez-Donaire, A. Usero, J. D. Henshaw, C. Faesi, A. K. Leroy, E. Rosolowsky, J. S. den Brok, M. Chevance, C. Eibensteiner, K. Grasha, R. S. Klessen, J. M. D. Kruijssen, D. Liu, S. Meidt, J. Neumann, L. Neumann, H. Pan, J. Puschnig, M. Querejeta, E. Schinnerer, T. G. Williams
Context. Investigating molecular gas tracers, such as hydrogen cyanide (HCN), to probe higher densities than CO emission across nearby galaxies remains challenging. This is due to the large observing times required to detect HCN at a high sensitivity and spatial resolution. Although approximate kiloparsec scales of HCN maps are available for tens of galaxies, higher-resolution maps still need to be available.Aims. We aim to study the properties of molecular gas, the contrast in intensity between two tracers that probe different density regimes (the HCN(1–0)/CO(2–1) ratio), and their kinematics across NGC 253, one of the closest starburst galaxies. With its advanced capabilities, the Atacama Large Millimeter/submillimeter Array (ALMA) can map these features at a high resolution across a large field of view and uncover the nature of such dense gas in extragalactic systems.Methods. We present new ALMA Atacama Compact Array and Total Power (ACA+TP) observations of the HCN emission across NGC 253. The observations cover the inner 8.6′ of the galaxy disk at a spatial resolution of 300 pc. Our study examines the distribution and kinematics of the HCN-traced gas and its relationship with the bulk molecular gas traced by CO(2–1). We analyze the integrated intensity and mean velocity of HCN and CO along each line of sight. We also used the SCOUSE software to perform spectral decomposition, which considers each velocity component separately.Results. We find that the denser molecular gas traced by HCN piles up in a ring-like structure at a radius of 2 kpc. The HCN emission is enhanced by two orders of magnitude in the central 2 kpc regions, beyond which its intensity decreases with increasing galactocentric distance. The number of components in the HCN spectra shows a robust environmental dependence, with multiple velocity features across the center and bar. The HCN spectra exhibit multiple velocity features across the center and bar, which shows a robust environmental dependence. We have identified an increase in the HCN/CO ratio in these regions, corresponding to a velocity component likely associated with a molecular outflow. We have also discovered that the ratio between the total infrared luminosity and dense gas mass, which is an indicator of the star formation efficiency of dense gas, is anticorrelated with the molecular gas surface density up to approximately 200 M⊙ pc−2. However, beyond this point, the ratio starts to increase.Conclusions. We argue that using information about spectroscopic features of molecular emission is an important aspect of understanding molecular properties in galaxies.
背景。研究分子气体示踪剂，如氰化氢（HCN），以探测附近星系中比 CO 辐射更高的密度，仍然具有挑战性。这是因为以高灵敏度和高空间分辨率探测 HCN 需要大量的观测时间。尽管目前已经可以获得数十个星系的近似千帕斯卡尺度的 HCN 地图，但仍然需要更高分辨率的地图。我们的目标是研究分子气体的性质、两种探测不同密度状态的示踪剂之间的强度对比（HCN(1-0)/CO(2-1)比值）以及它们在最接近星爆星系之一的 NGC 253 中的运动学特性。阿塔卡马大型毫米波/亚毫米波阵列（ALMA）凭借其先进的功能，可以在大视野范围内以高分辨率绘制这些特征，并揭示银河系外这种高密度气体的性质。我们展示了 ALMA 阿塔卡马紧凑阵列和总功率（ACA+TP）对整个 NGC 253 的 HCN 发射的最新观测结果。观测覆盖了星系盘内部8.6′的区域，空间分辨率为300 pc。我们的研究考察了 HCN 追踪气体的分布和运动学特性，以及它与 CO(2-1) 追踪的大量分子气体之间的关系。我们分析了每条视线上 HCN 和 CO 的综合强度和平均速度。我们还使用 SCOUSE 软件进行了光谱分解，分别考虑了每个速度分量。我们发现，由 HCN 追踪到的密度较高的分子气体在半径为 2 kpc 的地方堆积成一个环状结构。在半径为 2 kpc 的中心区域，HCN 的发射增强了两个数量级，而在该区域之外，其强度会随着银心距离的增加而降低。HCN 光谱中的分量数量与环境密切相关，在中心和棒状区域有多个速度特征。HCN光谱在中心和条带上呈现出多个速度特征，这显示出强烈的环境依赖性。我们在这些区域发现了 HCN/CO 比率的增加，这与可能与分子外流有关的速度成分相对应。我们还发现，作为致密气体恒星形成效率指标的红外总光度与致密气体质量之比，在大约 200 M⊙ pc-2 的范围内与分子气体表面密度是反相关的。然而，超过这一点后，该比率开始增加。我们认为，利用分子发射光谱特征的信息是了解星系分子性质的一个重要方面。
{"title":"The properties and kinematics of HCN emission across the closest starburst galaxy NGC 253 observed with ALMA","authors":"I. Bešlić, A. T. Barnes, F. Bigiel, M. J. Jiménez-Donaire, A. Usero, J. D. Henshaw, C. Faesi, A. K. Leroy, E. Rosolowsky, J. S. den Brok, M. Chevance, C. Eibensteiner, K. Grasha, R. S. Klessen, J. M. D. Kruijssen, D. Liu, S. Meidt, J. Neumann, L. Neumann, H. Pan, J. Puschnig, M. Querejeta, E. Schinnerer, T. G. Williams","doi":"10.1051/0004-6361/202347568","DOIUrl":"https://doi.org/10.1051/0004-6361/202347568","url":null,"abstract":"<i>Context.<i/> Investigating molecular gas tracers, such as hydrogen cyanide (HCN), to probe higher densities than CO emission across nearby galaxies remains challenging. This is due to the large observing times required to detect HCN at a high sensitivity and spatial resolution. Although approximate kiloparsec scales of HCN maps are available for tens of galaxies, higher-resolution maps still need to be available.<i>Aims.<i/> We aim to study the properties of molecular gas, the contrast in intensity between two tracers that probe different density regimes (the HCN(1–0)/CO(2–1) ratio), and their kinematics across NGC 253, one of the closest starburst galaxies. With its advanced capabilities, the Atacama Large Millimeter/submillimeter Array (ALMA) can map these features at a high resolution across a large field of view and uncover the nature of such dense gas in extragalactic systems.<i>Methods.<i/> We present new ALMA Atacama Compact Array and Total Power (ACA+TP) observations of the HCN emission across NGC 253. The observations cover the inner 8.6′ of the galaxy disk at a spatial resolution of 300 pc. Our study examines the distribution and kinematics of the HCN-traced gas and its relationship with the bulk molecular gas traced by CO(2–1). We analyze the integrated intensity and mean velocity of HCN and CO along each line of sight. We also used the SCOUSE software to perform spectral decomposition, which considers each velocity component separately.<i>Results.<i/> We find that the denser molecular gas traced by HCN piles up in a ring-like structure at a radius of 2 kpc. The HCN emission is enhanced by two orders of magnitude in the central 2 kpc regions, beyond which its intensity decreases with increasing galactocentric distance. The number of components in the HCN spectra shows a robust environmental dependence, with multiple velocity features across the center and bar. The HCN spectra exhibit multiple velocity features across the center and bar, which shows a robust environmental dependence. We have identified an increase in the HCN/CO ratio in these regions, corresponding to a velocity component likely associated with a molecular outflow. We have also discovered that the ratio between the total infrared luminosity and dense gas mass, which is an indicator of the star formation efficiency of dense gas, is anticorrelated with the molecular gas surface density up to approximately 200 M<sub>⊙<sub/> pc<sup>−2<sup/>. However, beyond this point, the ratio starts to increase.<i>Conclusions.<i/> We argue that using information about spectroscopic features of molecular emission is an important aspect of understanding molecular properties in galaxies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-06DOI: 10.1051/0004-6361/202450121
J. A. Wojtczak, B. Tessore, L. Labadie, K. Perraut, J. Bouvier, C. Dougados, H. Nowacki, A. Soulain, E. Alécian, G. Pantolmos, J. Ferreira, C. Straubmeier, A. Eckart
<i>Context.<i/> Hydrogen recombination lines such as Br<i>γ<i/> are tracers of hot gas within the inner circumstellar disk of young stellar objects (YSOs). In the relatively cool innermost environment of T Tauri stars specifically, Br<i>γ<i/> emission is closely associated with magnetically driven processes, such as magnetospheric accretion. Magnetospheric emission alone would arise from a relatively compact region that is located close to the co-rotation radius of the star-disk system. Since it was previously found that the Br<i>γ<i/> emission region in these objects can be significantly more extended than this, it was speculated that Brγ emission may also originate from a larger structure, such as a magnetised disk wind.<i>Aims.<i/> Our aim is to build upon the analysis presented in our previous work by attempting to match the observational data obtained with VLTI GRAVITY for RU Lup in 2021 with an expanded model. Specifically, we will determine if the inclusion of an additional disk wind as a Brγ emitter in the inner disk will be able to reproduce the trend of increasing sizes at higher velocities. In addition, we will investigate whether the additional component will alter the obtained photocentre shift profiles to be more consistent with the observational results.<i>Methods.<i/> We make use of the MCFOST radiative transfer code to solve for Br<i>γ<i/> line formation in the innermost disk of an RU Lup-like system. From the resulting images we compute synthetic interferometric observables in the form of the continuum-normalised line profiles, visibilities, and differential phases. Based on these computations, we first investigate how individual parameter variations in a pure magnetospheric accretion model and a pure parameteric disk wind model translate to changes in these derived quantities. Then we attempt to reproduce the RU Lup GRAVITY data with different parameter variants of magnetospheric accretion models, disk wind models, and combined hybrid models.<i>Results.<i/> We demonstrate that magnetospheric accretion models and disk wind models on their own can emulate certain individual characteristics from the observational results, but individually fail to comprehensively reproduce the observational trends. Disk wind plus accretion hybrid models are in principle capable of explaining the variation in characteristic radii across the line and the corresponding flux ratios. While the model parameters of the hybrid models are mostly in good agreement with the known attributes of RU Lup, we find that our best-fitting models deviate in terms of rotational period and the size of the magnetosphere. The best-fitting hybrid model does not respect the co-rotation criterion, as the magnetospheric truncation radius is about 50% larger than the co-rotation radius.<i>Conclusions.<i/> The deviation of the found magnetospheric size when assuming stable accretion with funnel flows indicates that the accretion process in RU Lup is more complex than what the a
{"title":"The interplay between disk wind and magnetospheric accretion mechanisms in the innermost environment of RU Lup","authors":"J. A. Wojtczak, B. Tessore, L. Labadie, K. Perraut, J. Bouvier, C. Dougados, H. Nowacki, A. Soulain, E. Alécian, G. Pantolmos, J. Ferreira, C. Straubmeier, A. Eckart","doi":"10.1051/0004-6361/202450121","DOIUrl":"https://doi.org/10.1051/0004-6361/202450121","url":null,"abstract":"<i>Context.<i/> Hydrogen recombination lines such as Br<i>γ<i/> are tracers of hot gas within the inner circumstellar disk of young stellar objects (YSOs). In the relatively cool innermost environment of T Tauri stars specifically, Br<i>γ<i/> emission is closely associated with magnetically driven processes, such as magnetospheric accretion. Magnetospheric emission alone would arise from a relatively compact region that is located close to the co-rotation radius of the star-disk system. Since it was previously found that the Br<i>γ<i/> emission region in these objects can be significantly more extended than this, it was speculated that Brγ emission may also originate from a larger structure, such as a magnetised disk wind.<i>Aims.<i/> Our aim is to build upon the analysis presented in our previous work by attempting to match the observational data obtained with VLTI GRAVITY for RU Lup in 2021 with an expanded model. Specifically, we will determine if the inclusion of an additional disk wind as a Brγ emitter in the inner disk will be able to reproduce the trend of increasing sizes at higher velocities. In addition, we will investigate whether the additional component will alter the obtained photocentre shift profiles to be more consistent with the observational results.<i>Methods.<i/> We make use of the MCFOST radiative transfer code to solve for Br<i>γ<i/> line formation in the innermost disk of an RU Lup-like system. From the resulting images we compute synthetic interferometric observables in the form of the continuum-normalised line profiles, visibilities, and differential phases. Based on these computations, we first investigate how individual parameter variations in a pure magnetospheric accretion model and a pure parameteric disk wind model translate to changes in these derived quantities. Then we attempt to reproduce the RU Lup GRAVITY data with different parameter variants of magnetospheric accretion models, disk wind models, and combined hybrid models.<i>Results.<i/> We demonstrate that magnetospheric accretion models and disk wind models on their own can emulate certain individual characteristics from the observational results, but individually fail to comprehensively reproduce the observational trends. Disk wind plus accretion hybrid models are in principle capable of explaining the variation in characteristic radii across the line and the corresponding flux ratios. While the model parameters of the hybrid models are mostly in good agreement with the known attributes of RU Lup, we find that our best-fitting models deviate in terms of rotational period and the size of the magnetosphere. The best-fitting hybrid model does not respect the co-rotation criterion, as the magnetospheric truncation radius is about 50% larger than the co-rotation radius.<i>Conclusions.<i/> The deviation of the found magnetospheric size when assuming stable accretion with funnel flows indicates that the accretion process in RU Lup is more complex than what the a","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142158708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}
Pub Date : 2024-09-05DOI: 10.1051/0004-6361/202449935
A. R. Costa Silva, O. D. S. Demangeon, N. C. Santos, D. Ehrenreich, C. Lovis, H. Chakraborty, M. Lendl, F. Pepe, S. Cristiani, R. Rebolo, M. R. Zapatero-Osorio, V. Adibekyan, Y. Alibert, R. Allart, C. Allende Prieto, T. Azevedo Silva, F. Borsa, V. Bourrier, E. Cristo, P. Di Marcantonio, E. Esparza-Borges, P. Figueira, J. I. González Hernández, E. Herrero-Cisneros, G. Lo Curto, C. J. A. P. Martins, A. Mehner, N. J. Nunes, E. Palle, S. Pelletier, J. V. Seidel, A. M. Silva, S. G. Sousa, A. Sozzetti, M. Steiner, A. Suárez Mascareño, S. Udry
Context. Ultra hot Jupiters (gas giants with Teq > 2000 K) are intriguing exoplanets due to the extreme physics and chemistry present in their atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy.Aims. We search for signatures of neutral and singly ionised iron (Fe I and Fe II, respectively) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties.Methods. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates created with petitRADTRANS, using cross-correlation function techniques.Results. We detect a blueshifted (−4.7 ± 0.3 km s−1) Fe I emission signature on the dayside of WASP-76 b at 6.0σ. The signal is detected independently both before and after the eclipse, and it is blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy.Conclusions. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of the ultra hot Jupiter WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies. It also highlights the ability of ESPRESSO to probe the dayside of this class of exoplanets.
背景超高温木星（Teq > 2000 K的气态巨行星）是引人入胜的系外行星，因为它们的大气中存在着极端的物理和化学成分。可以利用地面高分辨率发射光谱来描述它们的炙热天体。我们在超热木星 WASP-76 b 的日侧寻找中性铁和单质电离铁（分别为 Fe I 和 Fe II）的特征，因为在这颗系外行星中通过透射光谱探测到了这些物种。此外，我们的目的是证实之前研究中报道的热反转层的存在，并尝试对其特性进行约束。我们利用 VLT 的 ESPRESSO 对 WASP-76 b 进行了四次观测，分别是在二次凌日前不久和凌日后不久的轨道阶段，当时日面在观测范围内。我们首次分析了这颗系外行星的高分辨率光学发射光谱。我们利用交叉相关函数技术，将数据与用 petitRADTRANS 创建的合成模板进行了比较。我们在 WASP-76 b 的日侧 6.0σ 处探测到一个蓝移（-4.7 ± 0.3 km s-1）的 Fe I 发射信号。该信号在日食之前和之后都被探测到，而且都是蓝移。铁发射特征的存在证实了热反转层的存在。铁 II 没有被探测到，可能是因为这种物质位于大气的上层，光学厚度较薄。因此，WASP-76 b日侧的铁II特征太弱，无法用发射光谱探测到。我们认为蓝移铁一特征是由从热点上升到大气上层的物质产生的，并讨论了与热点位置有关的可能情况。这项工作通过分析超热木星 WASP-76 b 大气层中的铁离子特征，揭示了其日侧正在发生的一些动态过程，并补充了之前从透射研究中获得的知识。它还凸显了ESPRESSO探测这类系外行星日侧的能力。
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