Pub Date : 2026-01-20DOI: 10.1051/0004-6361/202556493
S. Marino, V. Gupta, P. Weber, T. D. Pearce, A. Brennan, S. Pérez, S. Mac Manamon, L. Matrà, J. Milli, M. Booth, C. del Burgo, G. Cataldi, E. Chiang, Y. Han, Th. Henning, A. M. Hughes, M. R. Jankovic, Á. Kóspál, J. B. Lovell, P. Luppe, E. Mansell, M. A. MacGregor, A. Moór, J. Olofsson, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, B. Zawadzki
Context. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin.Aims. As part of ARKS, we observed the gas-rich system HD 121617 with a 0⋅′′ 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system.Methods. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (12CO and 13CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data.Results. We find that the dust arc is narrow (1–5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system’s rotation, and represents 13% of the total dust mass (0.2 M⊕). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients.Conclusions. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 M⊕, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"S. Marino, V. Gupta, P. Weber, T. D. Pearce, A. Brennan, S. Pérez, S. Mac Manamon, L. Matrà, J. Milli, M. Booth, C. del Burgo, G. Cataldi, E. Chiang, Y. Han, Th. Henning, A. M. Hughes, M. R. Jankovic, Á. Kóspál, J. B. Lovell, P. Luppe, E. Mansell, M. A. MacGregor, A. Moór, J. Olofsson, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, B. Zawadzki","doi":"10.1051/0004-6361/202556493","DOIUrl":"https://doi.org/10.1051/0004-6361/202556493","url":null,"abstract":"<i>Context<i/>. ExoKuiper belts around young A-type stars often host CO gas, whose origin is still unclear. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) includes six of these gas-bearing belts, to characterise their dust and gas distributions and investigate the gas origin.<i>Aims<i/>. As part of ARKS, we observed the gas-rich system HD 121617 with a 0<sub>⋅<sub/><sup>′′<sup/> 12 (14 au) resolution and discovered an arc of enhanced dust density. In this paper, we analyse in detail the dust and gas distributions and the gas kinematics of this system.<i>Methods<i/>. We extracted radial and azimuthal profiles of the dust (in the millimetre and near-infrared) and gas emission (<sup>12<sup/>CO and <sup>13<sup/>CO) from reconstructed images. To constrain the morphology of the arc, we fitted an asymmetric model to the dust emission. To characterise the gas kinematics, we fitted a Keplerian model to the velocity map and extracted the gas azimuthal velocity profile by deprojecting the data.<i>Results<i/>. We find that the dust arc is narrow (1–5 au wide at a radius of 75 au), azimuthally extended with a full width at half maximum of ~90°, and asymmetric; the emission is more azimuthally compact in the direction of the system’s rotation, and represents 13% of the total dust mass (0.2 <i>M<i/><sub>⊕<sub/>). From analysis of the scattered light and CO images, we conclude that the arc is much less pronounced or absent for small grains and gas. Finally, we find strong non-Keplerian azimuthal velocities at the inner and outer wings of the ring, as was expected due to strong pressure gradients.<i>Conclusions<i/>. The dust arc resembles the asymmetries found in protoplanetary discs, often interpreted as the result of dust trapping in vortices. If the gas disc mass is high enough (≳20 <i>M<i/><sub>⊕<sub/>, requiring a primordial gas origin), both the radial confinement of the ring and the azimuthal arc may result from dust grains responding to gas drag. Alternatively, it could result from planet-disc interactions via mean motion resonances. Further studies should test these hypotheses and may provide a dynamical gas mass estimate in this CO-rich exoKuiper belt.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"276 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006201","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 : 2026-01-20DOI: 10.1051/0004-6361/202554956
F. Ahlborn, J. Higl, R. Andrassy, G. Leidi, A. Weiss, F. Röpke
Context. The efficient transport of energy and chemical elements by convective motions has a profound effect on the structure and evolution of stars. These motions occur on the relatively short dynamical timescale of convection and are intrinsically multi-dimensional. Stellar models usually rely on the one-dimensional mixing-length approximation of these processes, which is known to break down at convective boundaries. The Kuhfuß, R. (1987, Dissertation, Technische Universität München, München) convection model has been shown to handle convective boundaries in a more consistent way.Aims. We test the assumptions that enter the Kuhfuß model using multi-dimensional hydrodynamics simulations, and we compare the results with existing one-dimensional models. Where possible, we also aim to calibrate the parameters of the Kuhfuß model using the simulations.Methods. We computed one-dimensional stellar models employing the Kuhfuß model of a 3 M⊙ main-sequence star. These models were compared to three-dimensional hydrodynamic simulations obtained with the code called SEVEN-LEAGUE HYDRO and using the Reynolds-averaged Navier Stokes analysis. We analysed the global convective variables and individual contributions to the equations of the convection model.Results. The turbulent kinetic energy as predicted by the Kuhfuß model agrees well with the simulation results. Towards the boundary of the convective core, the simulations show a layer of a positive entropy gradient that coincides with a positive convective flux, as predicted by the convection model. The terms involving pressure fluctuations are found to have a non-negligible magnitude.Conclusions. The agreement of the turbulent kinetic energy equation for the convection model and the simulation is an important sign that the convection model is physically accurate. The gradient of the mean entropy that we found in the multi-dimensional simulations and in the Kuhfuß model confirms the existence of a Deardorff layer, that is, of a layer with a subadiabtic temperature stratification and positive convective flux. This is not predicted by the mixing-length theory. The assumption that turbulence is isotropic and that pressure fluctuations are negligible needs to be revisited in the convection model.
上下文。能量和化学元素通过对流运动的有效传输对恒星的结构和演化有着深远的影响。这些运动发生在相对较短的对流动力学时间尺度上，本质上是多维的。恒星模型通常依赖于这些过程的一维混合长度近似值，众所周知，这种近似值在对流边界处会崩溃。Kuhfuß， R. （1987, Dissertation, Technische Universität m nchen, m nchen）对流模型已被证明以更一致的方式处理对流边界。我们使用多维流体力学模拟来检验进入Kuhfuß模型的假设，并将结果与现有的一维模型进行比较。在可能的情况下，我们还打算使用模拟方法校准Kuhfuß模型的参数。我们用Kuhfuß模型计算了一个3 M⊙主序星的一维恒星模型。这些模型与三维流体动力学模拟进行了比较，这些模拟是用名为SEVEN-LEAGUE HYDRO的代码获得的，并使用了reynolds -average Navier Stokes分析。我们分析了整体对流变量和个体对对流模式方程的贡献。Kuhfuß模型预测的湍流动能与模拟结果吻合较好。在对流核边界处，模拟结果显示出一层正熵梯度，与对流模型预测的正对流通量相吻合。发现涉及压力波动的项具有不可忽略的量级。对流模型湍流动能方程与模拟结果的一致性是对流模型物理精度的重要标志。我们在多维模拟和Kuhfuß模型中发现的平均熵梯度证实了Deardorff层的存在，即具有亚绝热温度分层和正对流通量的层。这是混合长度理论无法预测的。紊流是各向同性和压力波动可以忽略不计的假设需要在对流模型中重新考虑。
{"title":"Validating a non-local stellar convection model with 3D hydrodynamics simulations","authors":"F. Ahlborn, J. Higl, R. Andrassy, G. Leidi, A. Weiss, F. Röpke","doi":"10.1051/0004-6361/202554956","DOIUrl":"https://doi.org/10.1051/0004-6361/202554956","url":null,"abstract":"<i>Context.<i/> The efficient transport of energy and chemical elements by convective motions has a profound effect on the structure and evolution of stars. These motions occur on the relatively short dynamical timescale of convection and are intrinsically multi-dimensional. Stellar models usually rely on the one-dimensional mixing-length approximation of these processes, which is known to break down at convective boundaries. The Kuhfuß, R. (1987, Dissertation, Technische Universität München, München) convection model has been shown to handle convective boundaries in a more consistent way.<i>Aims.<i/> We test the assumptions that enter the Kuhfuß model using multi-dimensional hydrodynamics simulations, and we compare the results with existing one-dimensional models. Where possible, we also aim to calibrate the parameters of the Kuhfuß model using the simulations.<i>Methods.<i/> We computed one-dimensional stellar models employing the Kuhfuß model of a 3 M<sub>⊙<sub/> main-sequence star. These models were compared to three-dimensional hydrodynamic simulations obtained with the code called SEVEN-LEAGUE HYDRO and using the Reynolds-averaged Navier Stokes analysis. We analysed the global convective variables and individual contributions to the equations of the convection model.<i>Results.<i/> The turbulent kinetic energy as predicted by the Kuhfuß model agrees well with the simulation results. Towards the boundary of the convective core, the simulations show a layer of a positive entropy gradient that coincides with a positive convective flux, as predicted by the convection model. The terms involving pressure fluctuations are found to have a non-negligible magnitude.<i>Conclusions.<i/> The agreement of the turbulent kinetic energy equation for the convection model and the simulation is an important sign that the convection model is physically accurate. The gradient of the mean entropy that we found in the multi-dimensional simulations and in the Kuhfuß model confirms the existence of a Deardorff layer, that is, of a layer with a subadiabtic temperature stratification and positive convective flux. This is not predicted by the mixing-length theory. The assumption that turbulence is isotropic and that pressure fluctuations are negligible needs to be revisited in the convection model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"8 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006233","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 : 2026-01-20DOI: 10.1051/0004-6361/202556505
B. Zawadzki, A. Fehr, A. M. Hughes, E. Mansell, J. Kittling, Y. Han, C. Hou, M. Pan, J. Milli, J. Olofsson, T. Pearce, A. A. Sefilian, A. Nurmohamed, J. Lee, Y. Mpofu, M. Bonduelle, M. Booth, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, S. Ertel, Th. Henning, M. R. Jankovic, G. M. Kennedy, Á. Kóspál, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Mac Manamon, S. Marino, J. P. Marshall, L. Matrà, A. Moór, S. Pérez, P. Weber, D. J. Wilner, M. C. Wyatt
Context. Debris disks – collisionally sustained belts of dust and sometimes gas around main sequence stars – are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time.Aims. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks.Methods. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets.Results. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ hHWHM ≤ 0.193 and a median best-fit value of hHWHM = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 M⊕), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"B. Zawadzki, A. Fehr, A. M. Hughes, E. Mansell, J. Kittling, Y. Han, C. Hou, M. Pan, J. Milli, J. Olofsson, T. Pearce, A. A. Sefilian, A. Nurmohamed, J. Lee, Y. Mpofu, M. Bonduelle, M. Booth, A. Brennan, C. del Burgo, J. M. Carpenter, G. Cataldi, E. Chiang, S. Ertel, Th. Henning, M. R. Jankovic, G. M. Kennedy, Á. Kóspál, A. V. Krivov, J. B. Lovell, P. Luppe, M. A. MacGregor, S. Mac Manamon, S. Marino, J. P. Marshall, L. Matrà, A. Moór, S. Pérez, P. Weber, D. J. Wilner, M. C. Wyatt","doi":"10.1051/0004-6361/202556505","DOIUrl":"https://doi.org/10.1051/0004-6361/202556505","url":null,"abstract":"<i>Context<i/>. Debris disks – collisionally sustained belts of dust and sometimes gas around main sequence stars – are remnants of planet formation processes and are found in systems ≳10 Myr old. Millimeter-wavelength observations are particularly important, as the grains probed by these observations are not strongly affected by radiation pressure and stellar winds, allowing them to probe the dynamics of large bodies producing dust. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is analyzing high-resolution observations of 24 debris disks to enable the characterization of debris disk substructures across a large sample for the first time.<i>Aims<i/>. For the most highly inclined disks, it is possible to recover the vertical structure of the disk. We aim to model and analyze the most highly inclined systems in the ARKS sample in order to uniformly extract the vertical dust distributions for a sample of well-resolved debris disks.<i>Methods<i/>. We employed both parametric and nonparametric methods to constrain the vertical dust distributions for the most highly inclined ARKS targets.<i>Results<i/>. We find a broad range of aspect ratios, revealing a wide diversity in vertical structure, with a range of best-fit parametric values of 0.0026 ≤ <i>h<i/><sub>HWHM<sub/> ≤ 0.193 and a median best-fit value of <i>h<i/><sub>HWHM<sub/> = 0.021. The results obtained by nonparametric modeling are generally consistent with the parametric modeling results. We find that five of the 13 disks are consistent with having total disk masses less than that of Neptune (17 <i>M<i/><sub>⊕<sub/>), assuming stirring by internal processes (self-stirring and collisional and frictional damping). Furthermore, most systems show a significant preference for a Lorentzian vertical profile rather than a Gaussian.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"101 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006200","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 : 2026-01-20DOI: 10.1051/0004-6361/202556566
A. Brennan, L. Matrà, S. Mac Manamon, S. Marino, G. Cataldi, A. M. Hughes, P. Weber, Y. Han, J. P. Marshall, B. Zawadzki, P. Luppe, A. A. Sefilian, A. Moór, M. A. MacGregor, J. B. Lovell, A. Kóspál, M. Bonduelle, E. Mansell, M. C. Wyatt, T. D. Pearce, J. M. Carpenter, D. J. Wilner, C. del Burgo, S. Pérez, T. Henning, J. Milli, E. Chiang
Context. CO gas has been detected in ~20 debris discs, typically classified as CO-poor or CO-rich. We present observations of the CO-rich HD 121617 debris disc as part of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS).Aims. We model local CO line profiles in the HD 121617 debris disc to investigate optical depth, CO mass, and temperature. HD 121617 is a well-suited ARKS target due to its previously detected CO emission and moderate inclination, reducing the effect of Keplerian shear.Methods. Using high-resolution ALMA Band 7 observations of 12CO J=3–2 (26 m s−1, 0⋅′′ 1), we create local line profiles by aligning and stacking spectra in concentric annuli of 0⋅′′ 02 width. These profiles are modelled with both a toy model and a RADMC-3D model that includes projection effects and Keplerian shear.Results. The resulting local profiles are Gaussian-shaped and broad due to the effect of Keplerian shear. Fitting a RADMC-3D model to the 13CO data, we find that an optically thick model (temperature of 38 K and mass of 2 × 10−3 M⊕) reproduces the data, particularly the enhanced intensity at orbital azimuths of ~±45° and ±135°, which forms an X-shape in the velocity integrated intensity map, as well as the broader 12CO linewidth compared to 13CO. Scaling this model by the ISM abundance ratio (~77) also reproduces the 12CO data, but high optical depths and model assumptions limit mass constraints.Conclusions. Keplerian shear causes azimuthally averaged line profiles to appear Gaussian regardless of optical depth; therefore, we caution against using the local line profiles to distinguish between optically thin and thick emission. We constrain the mean molecular weight to 12.6−1.1+1.3, dependent on model assumptions. Although model dependent, our 13CO results indicate that C18O might also be optically thick in CO-rich debris discs, contrary to previous assumptions, and that the mean molecular weight is significantly higher than if H2 were the dominant gas species, suggesting a non-primordial composition.
上下文。在约20个碎片盘中检测到CO气体，通常分为贫CO和富CO两类。我们提出了对富含co的HD 121617碎片盘的观测，作为ALMA调查的一部分，以解决外柯伊伯带亚结构（ARKS）。我们模拟了HD 121617碎片盘中的局部CO线剖面，以研究光学深度、CO质量和温度。HD 121617是一个非常适合的ARKS目标，因为它以前检测到CO发射和适度的倾角，减少了开普勒剪切的影响。利用高分辨率ALMA Band 7观测12CO J= 3-2 (26 m s−1,0⋅”1)，我们通过对齐和叠加光谱在0⋅”02宽度的同心环空中创建局部线剖面。这些剖面用玩具模型和RADMC-3D模型建模，其中包括投影效果和开普勒剪切。由于开普勒剪切的影响，得到的局部剖面是高斯形的，而且很宽。将RADMC-3D模型拟合13CO数据，我们发现一个光学厚模型（温度为38 K，质量为2 × 10−3 M⊕）再现了数据，特别是在轨道方位角为~±45°和±135°处的强度增强，在速度综合强度图中形成x形，并且与13CO相比，12CO线宽更宽。用ISM丰度比（~77）对该模型进行缩放也能再现12CO的数据，但较高的光学深度和模型假设限制了质量约束。无论光学深度如何，开普勒剪切都会导致方位平均线轮廓呈现高斯分布；因此，我们警告不要使用局部线轮廓来区分光学薄和厚发射。根据模型假设，我们将平均分子量限制为12.6−1.1+1.3。虽然依赖于模型，但我们的13CO结果表明，在富含co的碎片盘中，C18O也可能具有光学厚度，这与之前的假设相反，并且平均分子量明显高于H2为主要气体的情况，表明其非原始成分。
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"A. Brennan, L. Matrà, S. Mac Manamon, S. Marino, G. Cataldi, A. M. Hughes, P. Weber, Y. Han, J. P. Marshall, B. Zawadzki, P. Luppe, A. A. Sefilian, A. Moór, M. A. MacGregor, J. B. Lovell, A. Kóspál, M. Bonduelle, E. Mansell, M. C. Wyatt, T. D. Pearce, J. M. Carpenter, D. J. Wilner, C. del Burgo, S. Pérez, T. Henning, J. Milli, E. Chiang","doi":"10.1051/0004-6361/202556566","DOIUrl":"https://doi.org/10.1051/0004-6361/202556566","url":null,"abstract":"<i>Context<i/>. CO gas has been detected in ~20 debris discs, typically classified as CO-poor or CO-rich. We present observations of the CO-rich HD 121617 debris disc as part of the ALMA survey to Resolve exoKuiper belt Substructures (ARKS).<i>Aims<i/>. We model local CO line profiles in the HD 121617 debris disc to investigate optical depth, CO mass, and temperature. HD 121617 is a well-suited ARKS target due to its previously detected CO emission and moderate inclination, reducing the effect of Keplerian shear.<i>Methods<i/>. Using high-resolution ALMA Band 7 observations of <sup>12<sup/>CO J=3–2 (26 m s<sup>−1<sup/>, 0<sub>⋅<sub/>′′ 1), we create local line profiles by aligning and stacking spectra in concentric annuli of 0<sub>⋅<sub/>′′ 02 width. These profiles are modelled with both a toy model and a RADMC-3D model that includes projection effects and Keplerian shear.<i>Results<i/>. The resulting local profiles are Gaussian-shaped and broad due to the effect of Keplerian shear. Fitting a RADMC-3D model to the <sup>13<sup/>CO data, we find that an optically thick model (temperature of 38 K and mass of 2 × 10<sup>−3<sup/> M<sub>⊕<sub/>) reproduces the data, particularly the enhanced intensity at orbital azimuths of ~±45° and ±135°, which forms an X-shape in the velocity integrated intensity map, as well as the broader <sup>12<sup/>CO linewidth compared to <sup>13<sup/>CO. Scaling this model by the ISM abundance ratio (~77) also reproduces the <sup>12<sup/>CO data, but high optical depths and model assumptions limit mass constraints.<i>Conclusions<i/>. Keplerian shear causes azimuthally averaged line profiles to appear Gaussian regardless of optical depth; therefore, we caution against using the local line profiles to distinguish between optically thin and thick emission. We constrain the mean molecular weight to 12.6<sub>−1.1<sub/><sup>+1.3<sup/>, dependent on model assumptions. Although model dependent, our <sup>13<sup/>CO results indicate that C<sup>18<sup/>O might also be optically thick in CO-rich debris discs, contrary to previous assumptions, and that the mean molecular weight is significantly higher than if H<sub>2<sub/> were the dominant gas species, suggesting a non-primordial composition.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006176","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 : 2026-01-20DOI: 10.1051/0004-6361/202556605
S. Mac Manamon, L. Matrà, S. Marino, A. Brennan, Y. Han, M. R. Jankovic, P. Weber, M. Bonduelle, J. M. Carpenter, G. Cataldi, A. M. Hughes, A. Kóspál, J. P. Marshall, B. C. Matthews, J. Milli, A. Moór, K. Öberg, S. Pérez, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, E. Chiang, A. S. Hales, J. B. Lovell, P. Luppe, M. A. MacGregor, T. Pearce, M. Booth, C. del Burgo, A. Fehr, E. Mansell, B. Zawadzki
Context. CO gas is detected in a significant number (~20) of debris discs (exoKuiper belts), but understanding its origin and evolution remains elusive. Crucial pieces of evidence are its mass and spectro-spatial distribution, which are coupled through optical depth and have only been analysed at low to moderate resolution so far. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is the first ALMA large program to target debris discs at high spectro-spatial resolution.Aims. We used 12CO and 13CO J=3-2 line data of 18 debris belts observed by ARKS, 5 of which were already known to be gas-bearing, in order to analyse the spectro-spatial distribution of CO and constrain the gas mass in discs that were known to host gas previously, and to search for gas in the remaining 13 discs without previous CO detections.Methods. We developed a line-imaging pipeline for ARKS CO data with a high spectro-spatial resolution. Using this tool, we produced line cubes for each of the ARKS targets, with a spatial resolution down to about 70 mas and a spectral resolution of 26 m s−1. We used spectro-spatial shifting and stacking techniques to produce a gallery of maps with the highest possible signal-to-noise ratio (S/N) and with radial and spectral profiles that reveal the distribution and kinematics of gas in five gas-bearing discs at unprecedented detail.Results. For each of the five gas-bearing discs (HD 9672/49 Ceti, HD 32297, HD 121617, HD 131488, and HD 131835), we constrained the inner radius of the 12CO (rmin ~ 3-68 au), and we found that the radial brightness profile of CO peaked interior to the dust ring, but that CO was also more radially extended than the dust. In a second-generation scenario, this would require significant shielding of CO that would allow it to viscously spread to the observed widths. We present the first radially resolved 12CO/13CO isotopologue flux ratios in five gas-bearing debris discs and found them to be constant with radius for the majority (four out of five) of systems. This indicates that 12CO and 13CO are both optically thick or optically thin throughout the discs. We report CO line fluxes or upper limits for all systems and optical depth dependant masses for the five systems with detected CO. Finally, we analysed the 12CO J=3-2 line luminosities for a range of ARKS debris discs and for debris discs from the literature. We confirm that gas is mostly detected in young systems. However, the high scatter seen in young/high fractional luminosity systems indicates no trend within the systems with detected gas. This could be caused by different system properties and/or evolution pathways.
上下文。CO气体在相当数量（~20）的碎片盘（外柯伊伯带）中被检测到，但对其起源和演化的理解仍然难以捉摸。关键的证据是它的质量和光谱空间分布，它们是通过光学深度耦合的，到目前为止只在低到中等分辨率下进行了分析。ALMA调查外柯伊伯带子结构（ARKS）是ALMA第一个以高光谱空间分辨率瞄准碎片盘的大型项目。我们利用ARKS观测到的18个碎片带的12CO和13CO J=3-2线数据，其中5个已经已知含气，以分析CO的光谱空间分布，并限制先前已知含有气体的圆盘中的气体质量，并在其余13个先前未检测到CO的圆盘中寻找气体。我们开发了一种具有高光谱空间分辨率的ARKS CO数据线成像管道。使用该工具，我们为每个ARKS目标生成了线立方，空间分辨率低至约70 mas，光谱分辨率为26 m s - 1。我们使用光谱空间移位和叠加技术，以最高可能的信噪比（S/N）和径向和光谱剖面制作了一个图库，以前所未有的细节揭示了五个含气圆盘中的气体分布和运动学。对于5个含气盘（HD 9672/49 Ceti、HD 32297、HD 121617、HD 131488和HD 131835），我们限制了12CO的内部半径（rmin ~ 3-68 au），我们发现CO的径向亮度剖面在尘埃环内部达到峰值，但CO也比尘埃更径向延伸。在第二代方案中，这将需要CO的大量屏蔽，使其能够粘性地扩散到观察到的宽度。我们首次在5个含气岩屑盘中径向解析了12CO/13CO同位素通量比，并发现它们在大多数（5个中的4个）系统中随半径不变。这表明12CO和13CO在整个光盘上都是光学厚或光学薄。我们报告了所有系统的CO线通量或上限以及检测到CO的五个系统的光学深度依赖质量。最后，我们分析了一系列ARKS碎片盘和文献中碎片盘的12CO J=3-2线光度。我们确认气体主要在年轻的系统中被探测到。然而，在年轻/高分数光度系统中看到的高散射表明，在检测到气体的系统中没有趋势。这可能是由不同的系统特性和/或进化途径引起的。
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"S. Mac Manamon, L. Matrà, S. Marino, A. Brennan, Y. Han, M. R. Jankovic, P. Weber, M. Bonduelle, J. M. Carpenter, G. Cataldi, A. M. Hughes, A. Kóspál, J. P. Marshall, B. C. Matthews, J. Milli, A. Moór, K. Öberg, S. Pérez, A. A. Sefilian, D. J. Wilner, M. C. Wyatt, E. Chiang, A. S. Hales, J. B. Lovell, P. Luppe, M. A. MacGregor, T. Pearce, M. Booth, C. del Burgo, A. Fehr, E. Mansell, B. Zawadzki","doi":"10.1051/0004-6361/202556605","DOIUrl":"https://doi.org/10.1051/0004-6361/202556605","url":null,"abstract":"<i>Context<i/>. CO gas is detected in a significant number (~20) of debris discs (exoKuiper belts), but understanding its origin and evolution remains elusive. Crucial pieces of evidence are its mass and spectro-spatial distribution, which are coupled through optical depth and have only been analysed at low to moderate resolution so far. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) is the first ALMA large program to target debris discs at high spectro-spatial resolution.<i>Aims<i/>. We used <sup>12<sup/>CO and <sup>13<sup/>CO J=3-2 line data of 18 debris belts observed by ARKS, 5 of which were already known to be gas-bearing, in order to analyse the spectro-spatial distribution of CO and constrain the gas mass in discs that were known to host gas previously, and to search for gas in the remaining 13 discs without previous CO detections.<i>Methods<i/>. We developed a line-imaging pipeline for ARKS CO data with a high spectro-spatial resolution. Using this tool, we produced line cubes for each of the ARKS targets, with a spatial resolution down to about 70 mas and a spectral resolution of 26 m s<sup>−1<sup/>. We used spectro-spatial shifting and stacking techniques to produce a gallery of maps with the highest possible signal-to-noise ratio (S/N) and with radial and spectral profiles that reveal the distribution and kinematics of gas in five gas-bearing discs at unprecedented detail.<i>Results<i/>. For each of the five gas-bearing discs (HD 9672/49 Ceti, HD 32297, HD 121617, HD 131488, and HD 131835), we constrained the inner radius of the <sup>12<sup/>CO (<i>r<i/><sub>min<sub/> ~ 3-68 au), and we found that the radial brightness profile of CO peaked interior to the dust ring, but that CO was also more radially extended than the dust. In a second-generation scenario, this would require significant shielding of CO that would allow it to viscously spread to the observed widths. We present the first radially resolved <sup>12<sup/>CO/<sup>13<sup/>CO isotopologue flux ratios in five gas-bearing debris discs and found them to be constant with radius for the majority (four out of five) of systems. This indicates that <sup>12<sup/>CO and <sup>13<sup/>CO are both optically thick or optically thin throughout the discs. We report CO line fluxes or upper limits for all systems and optical depth dependant masses for the five systems with detected CO. Finally, we analysed the <sup>12<sup/>CO J=3-2 line luminosities for a range of ARKS debris discs and for debris discs from the literature. We confirm that gas is mostly detected in young systems. However, the high scatter seen in young/high fractional luminosity systems indicates no trend within the systems with detected gas. This could be caused by different system properties and/or evolution pathways.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"64 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006173","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 : 2026-01-20DOI: 10.1051/0004-6361/202556489
S. Marino, L. Matrà, A. M. Hughes, J. Ehrhardt, G. M. Kennedy, C. del Burgo, A. Brennan, Y. Han, M. R. Jankovic, J. B. Lovell, S. Mac Manamon, J. Milli, P. Weber, B. Zawadzki, R. Bendahan-West, A. Fehr, E. Mansell, J. Olofsson, T. D. Pearce, A. Bayo, B. C. Matthews, T. Löhne, M. C. Wyatt, P. Ábrahám, M. Bonduelle, M. Booth, G. Cataldi, J. M. Carpenter, E. Chiang, S. Ertel, A. S. Hales, Th. Henning, Á. Kóspál, A. V. Krivov, P. Luppe, M. A. MacGregor, J. P. Marshall, A. Moór, S. Pérez, A. A. Sefilian, A. G. Sepulveda, D. J. Wilner
Context. The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity in terms of radii, widths, and scale heights. At the same time, ALMA has also shown that some belts contain CO gas, whose origin and implications are still highly uncertain. Most of this progress, however, has been limited by low angular resolution observations that hinder our ability to test existing models and theories.Aims. High-resolution observations of these belts are crucial for understanding the detailed distribution of solids and for constraining the gas distribution and kinematics.Methods. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to best address our main objectives: analysing the detailed radial and vertical structure, and characterising the gas content. The data were reduced and corrected to account for several systematic effects, and then imaged. Using parametric and non-parametric models, we constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models.Results. The first results of ARKS are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits substructures in the form of multiple dusty rings that may have been inherited from their protoplanetary discs. For highly inclined belts, we found that non-Gaussian vertical distributions are common and could be indicative of multiple dynamical populations. Half of the derived scale heights are small enough to be consistent with self-stirring in low-mass belts (Mbelt ≤ MNeptune). We also found that 10 of the 24 belts present asymmetries in the form of density enhancements, eccentricities, or warps. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas-rich systems, pushing the small grains to wider orbits than the large grains.Conclusions. ARKS has revealed a great diversity of radial and vertical structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products that we have made public through a dedicated website.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"S. Marino, L. Matrà, A. M. Hughes, J. Ehrhardt, G. M. Kennedy, C. del Burgo, A. Brennan, Y. Han, M. R. Jankovic, J. B. Lovell, S. Mac Manamon, J. Milli, P. Weber, B. Zawadzki, R. Bendahan-West, A. Fehr, E. Mansell, J. Olofsson, T. D. Pearce, A. Bayo, B. C. Matthews, T. Löhne, M. C. Wyatt, P. Ábrahám, M. Bonduelle, M. Booth, G. Cataldi, J. M. Carpenter, E. Chiang, S. Ertel, A. S. Hales, Th. Henning, Á. Kóspál, A. V. Krivov, P. Luppe, M. A. MacGregor, J. P. Marshall, A. Moór, S. Pérez, A. A. Sefilian, A. G. Sepulveda, D. J. Wilner","doi":"10.1051/0004-6361/202556489","DOIUrl":"https://doi.org/10.1051/0004-6361/202556489","url":null,"abstract":"<i>Context<i/>. The outer regions of planetary systems host dusty debris discs analogous to the Kuiper belt (exoKuiper belts), which provide crucial constraints on planet formation and evolution processes. ALMA dust observations have revealed a great diversity in terms of radii, widths, and scale heights. At the same time, ALMA has also shown that some belts contain CO gas, whose origin and implications are still highly uncertain. Most of this progress, however, has been limited by low angular resolution observations that hinder our ability to test existing models and theories.<i>Aims<i/>. High-resolution observations of these belts are crucial for understanding the detailed distribution of solids and for constraining the gas distribution and kinematics.<i>Methods<i/>. We conducted the first ALMA large programme dedicated to debris discs: the ALMA survey to Resolve exoKuiper belt Substructures (ARKS). We selected the 24 most promising belts to best address our main objectives: analysing the detailed radial and vertical structure, and characterising the gas content. The data were reduced and corrected to account for several systematic effects, and then imaged. Using parametric and non-parametric models, we constrained the radial and vertical distribution of dust, as well as the presence of asymmetries. For a subset of six belts with CO gas, we constrained the gas distribution and kinematics. To interpret these observations, we used a wide range of dynamical models.<i>Results<i/>. The first results of ARKS are presented as a series of ten papers. We discovered that up to 33% of our sample exhibits substructures in the form of multiple dusty rings that may have been inherited from their protoplanetary discs. For highly inclined belts, we found that non-Gaussian vertical distributions are common and could be indicative of multiple dynamical populations. Half of the derived scale heights are small enough to be consistent with self-stirring in low-mass belts (<i>M<i/><sub>belt<sub/> ≤ <i>M<i/><sub>Neptune<sub/>). We also found that 10 of the 24 belts present asymmetries in the form of density enhancements, eccentricities, or warps. We find that the CO gas is radially broader than the dust, but this could be an effect of optical depth. At least one system shows non-Keplerian kinematics due to strong pressure gradients, which may have triggered a vortex that trapped dust in an arc. Finally, we find evidence that the micron-sized grains may be affected by gas drag in gas-rich systems, pushing the small grains to wider orbits than the large grains.<i>Conclusions<i/>. ARKS has revealed a great diversity of radial and vertical structures in exoKuiper belts that may arise when they are formed in protoplanetary discs or subsequently via interactions with planets and/or gas. We encourage the community to explore the reduced data and data products that we have made public through a dedicated website.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"63 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006202","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 : 2026-01-20DOI: 10.1051/0004-6361/202556450
Yinuo Han, Elias Mansell, Jeff Jennings, Sebastian Marino, A. Meredith Hughes, Brianna Zawadzki, Anna Fehr, Jamar Kittling, Catherine Hou, Aliya Nurmohamed, Junu Lee, Allan Cheruiyot, Yamani Mpofu, Mark Booth, Richard Booth, Myriam Bonduelle, Aoife Brennan, Carlos del Burgo, John M. Carpenter, Gianni Cataldi, Eugene Chiang, Steve Ertel, Thomas Henning, Marija R. Jankovic, Ágnes Kóspál, Alexander V. Krivov, Joshua B. Lovell, Patricia Luppe, Meredith A. MacGregor, Sorcha Mac Manamon, Jonathan P. Marshall, Luca Matrà, Julien Milli, Attila Moór, Johan Olofsson, Tim Pearce, Sebastián Pérez, Antranik A. Sefilian, Philipp Weber, David J. Wilner, Mark C. Wyatt
Context. Debris discs are populated by belts of planetesimals, whose structure carries dynamical imprints of planets and the formation and evolutionary history of the planetary system. The relatively faint emission of debris discs has previously made it challenging to obtain a large sample of high-resolution ALMA images to characterise their substructures.Aims. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) was recently completed to cover the lack of high-resolution observations and to investigate the prevalence of substructures such as radial gaps and rings in a sample of 24 debris discs. This study characterises the radial structure of debris discs in the ARKS programme.Methods. We modelled all discs with a range of non-parametric and parametric approaches, including those that deconvolve and deproject the image or fit the visibilities directly, in order to identify and quantify the disc substructures.Results. Across the sample we find that of the 24 discs, 5 host multiple rings, 7 are single rings that display halos or additional low-amplitude rings, and 12 are single rings with at most tentative evidence of additional substructures. The fractional ring widths that we measured are significantly narrower than previously derived values, and they follow a distribution similar to the fractional widths of individual rings resolved in protoplanetary discs. However, there exists a population of rings in debris discs that are significantly wider than those in protoplanetary discs. We also find that discs with steep inner edges consistent with planet sculpting tend to be found at smaller (<100 au) radii, while more radially extended discs tend to have shallower edges more consistent with collisional evolution. An overwhelming majority of discs have radial profiles that are well-described by either a double power law or double-Gaussian parametrisation.Conclusions. While our findings suggest that it may be possible for some debris discs to inherit their structures directly from pro-toplanetary discs, there exists a sizeable population of broad debris discs that cannot be explained in this way. Assuming that the distribution of millimetre dust reflects the distribution of planetesimals, mechanisms that cause rings in protoplanetary discs to migrate or debris discs to broaden soon after formation may be at play, possibly mediated by planetary migration or scattering.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"Yinuo Han, Elias Mansell, Jeff Jennings, Sebastian Marino, A. Meredith Hughes, Brianna Zawadzki, Anna Fehr, Jamar Kittling, Catherine Hou, Aliya Nurmohamed, Junu Lee, Allan Cheruiyot, Yamani Mpofu, Mark Booth, Richard Booth, Myriam Bonduelle, Aoife Brennan, Carlos del Burgo, John M. Carpenter, Gianni Cataldi, Eugene Chiang, Steve Ertel, Thomas Henning, Marija R. Jankovic, Ágnes Kóspál, Alexander V. Krivov, Joshua B. Lovell, Patricia Luppe, Meredith A. MacGregor, Sorcha Mac Manamon, Jonathan P. Marshall, Luca Matrà, Julien Milli, Attila Moór, Johan Olofsson, Tim Pearce, Sebastián Pérez, Antranik A. Sefilian, Philipp Weber, David J. Wilner, Mark C. Wyatt","doi":"10.1051/0004-6361/202556450","DOIUrl":"https://doi.org/10.1051/0004-6361/202556450","url":null,"abstract":"<i>Context<i/>. Debris discs are populated by belts of planetesimals, whose structure carries dynamical imprints of planets and the formation and evolutionary history of the planetary system. The relatively faint emission of debris discs has previously made it challenging to obtain a large sample of high-resolution ALMA images to characterise their substructures.<i>Aims<i/>. The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) was recently completed to cover the lack of high-resolution observations and to investigate the prevalence of substructures such as radial gaps and rings in a sample of 24 debris discs. This study characterises the radial structure of debris discs in the ARKS programme.<i>Methods<i/>. We modelled all discs with a range of non-parametric and parametric approaches, including those that deconvolve and deproject the image or fit the visibilities directly, in order to identify and quantify the disc substructures.<i>Results<i/>. Across the sample we find that of the 24 discs, 5 host multiple rings, 7 are single rings that display halos or additional low-amplitude rings, and 12 are single rings with at most tentative evidence of additional substructures. The fractional ring widths that we measured are significantly narrower than previously derived values, and they follow a distribution similar to the fractional widths of individual rings resolved in protoplanetary discs. However, there exists a population of rings in debris discs that are significantly wider than those in protoplanetary discs. We also find that discs with steep inner edges consistent with planet sculpting tend to be found at smaller (<100 au) radii, while more radially extended discs tend to have shallower edges more consistent with collisional evolution. An overwhelming majority of discs have radial profiles that are well-described by either a double power law or double-Gaussian parametrisation.<i>Conclusions<i/>. While our findings suggest that it may be possible for some debris discs to inherit their structures directly from pro-toplanetary discs, there exists a sizeable population of broad debris discs that cannot be explained in this way. Assuming that the distribution of millimetre dust reflects the distribution of planetesimals, mechanisms that cause rings in protoplanetary discs to migrate or debris discs to broaden soon after formation may be at play, possibly mediated by planetary migration or scattering.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"92 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006219","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 : 2026-01-20DOI: 10.1051/0004-6361/202556637
M. R. Jankovic, N. Pawellek, J. Zander, T. Löhne, A. V. Krivov, J. Olofsson, A. Brennan, J. Milli, M. Bonduelle, M. C. Wyatt, A. A. Sefilian, T. D. Pearce, S. Mac Manamon, Y. Han, S. Marino, L. Matrà, A. Moór, M. Booth, E. Chiang, E. Mansell, P. Weber, A. M. Hughes, D. J. Wilner, P. Luppe, B. Zawadzki, C. del Burgo, Á. Kóspál, S. Pérez, J. M. Carpenter, T. Henning
Context. Dusty discs detected around main-sequence stars are thought to be signs of planetesimal belts in which the dust distribution is shaped by collisional and dynamical processes, including interactions with gas if present. The debris disc around the young A-type star HD 131835 is composed of two dust rings at ∼65 au and ∼100 au, a third unconstrained innermost component, and a gaseous component centred at ∼65 au. New ALMA observations show that the inner of the two dust rings is brighter than the outer one, in contrast with previous observations in scattered light.Aims. We explore two scenarios that could explain these observations: the two dust rings might represent distinct planetesimal belts with different collisional properties, or only the inner ring might contain planetesimals while the outer ring consists entirely of dust that has migrated outwards due to gas drag.Methods. To explore the first scenario, we employed a state-of-the-art collisional evolution code. To test the second scenario, we used a simple dynamical model of dust grain evolution in an optically thin gaseous disc. In each case we identified the parameters of the planetesimal and the gaseous disc that best reproduce the observational constraints.Results. Collisional models of two planetesimal belts cannot fully reproduce the observations by only varying their dynamical excitation, and matching the data through a different material strength requires an extreme difference in dust composition. The gas-driven scenario can reproduce the location of the outer ring and the brightness ratio of the two rings from scattered light observations, but the resulting outer ring is too faint overall in both scattered light and sub-millimetre emission.Conclusions. The dust rings in HD 131835 could be produced from two planetesimal belts, although how these belts would attain the required extremely different properties needs to be explained. The dust-gas interaction is a plausible alternative explanation and deserves further study using a more comprehensive model.
{"title":"The ALMA survey to Resolve exoKuiper belt Substructures (ARKS)","authors":"M. R. Jankovic, N. Pawellek, J. Zander, T. Löhne, A. V. Krivov, J. Olofsson, A. Brennan, J. Milli, M. Bonduelle, M. C. Wyatt, A. A. Sefilian, T. D. Pearce, S. Mac Manamon, Y. Han, S. Marino, L. Matrà, A. Moór, M. Booth, E. Chiang, E. Mansell, P. Weber, A. M. Hughes, D. J. Wilner, P. Luppe, B. Zawadzki, C. del Burgo, Á. Kóspál, S. Pérez, J. M. Carpenter, T. Henning","doi":"10.1051/0004-6361/202556637","DOIUrl":"https://doi.org/10.1051/0004-6361/202556637","url":null,"abstract":"<i>Context<i/>. Dusty discs detected around main-sequence stars are thought to be signs of planetesimal belts in which the dust distribution is shaped by collisional and dynamical processes, including interactions with gas if present. The debris disc around the young A-type star HD 131835 is composed of two dust rings at ∼65 au and ∼100 au, a third unconstrained innermost component, and a gaseous component centred at ∼65 au. New ALMA observations show that the inner of the two dust rings is brighter than the outer one, in contrast with previous observations in scattered light.<i>Aims<i/>. We explore two scenarios that could explain these observations: the two dust rings might represent distinct planetesimal belts with different collisional properties, or only the inner ring might contain planetesimals while the outer ring consists entirely of dust that has migrated outwards due to gas drag.<i>Methods<i/>. To explore the first scenario, we employed a state-of-the-art collisional evolution code. To test the second scenario, we used a simple dynamical model of dust grain evolution in an optically thin gaseous disc. In each case we identified the parameters of the planetesimal and the gaseous disc that best reproduce the observational constraints.<i>Results<i/>. Collisional models of two planetesimal belts cannot fully reproduce the observations by only varying their dynamical excitation, and matching the data through a different material strength requires an extreme difference in dust composition. The gas-driven scenario can reproduce the location of the outer ring and the brightness ratio of the two rings from scattered light observations, but the resulting outer ring is too faint overall in both scattered light and sub-millimetre emission.<i>Conclusions<i/>. The dust rings in HD 131835 could be produced from two planetesimal belts, although how these belts would attain the required extremely different properties needs to be explained. The dust-gas interaction is a plausible alternative explanation and deserves further study using a more comprehensive model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006172","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 : 2026-01-20DOI: 10.1051/0004-6361/202557602
Mats Ola Sand, Quentin Noraz, Guillaume Aulanier, Juan Martínez-Sykora, Mats Carlsson, Luc Rouppe van der Voort
Context. The formation mechanism for the dynamic type II spicules has remained elusive for many years. Their dynamical behaviour has long been linked to magnetic reconnection, yet no conclusive evidence has been provided. However, one recent observational study found signs of magnetic reconnection, as traced by Ellerman bombs (EBs), at the footpoints of many spicules. The triggering of EBs is generally linked to magnetic reconnection due to flux emergence and convective motions in the photosphere.Aims. We aim to explore whether we can connect EBs to type II spicules, and determine to what extent we can use EBs as an observational proxy to probe magnetic reconnection in this dynamic. We also aim to provide further insight into the mechanisms that trigger EBs.Methods. We used a simulation run with the radiative magnetohydrodynamics code Bifrost to track spicules and study the physical processes underlying their formation. To detect EBs and classify the spicules, we synthesised the chromospheric Hα spectral line using the multilevel radiative transfer code RH1.5D. We also traced shocks and current sheets to decipher the origin of EBs and spicules. We selected one type II spicule with a strong EB near its footpoint and studied their formation in detail.Results. A magnetoacoustic shock advects the magnetic field lines towards an oppositely directed ambient field, creating a current sheet. The current sheet accelerates dense plasma via a whiplash effect generated by magnetic reconnection into the inclined ambient field, launching the spicule. Several EB profiles trace shock- and magnetic-reconnection-induced dynamics during this process at the spicule footpoint.Conclusions. We present a new EB triggering mechanism in which a shock-induced current sheet reconnects, triggering an EB in the lower solar atmosphere. The shock-induced current sheet generates the upwards propagation of a type II spicule via reconnection outflows. These results provide a plausible physical origin for the recently observed connection between EBs and spicules.
{"title":"Shock-induced magnetic reconnection driving Ellerman bomb emission and a spicule","authors":"Mats Ola Sand, Quentin Noraz, Guillaume Aulanier, Juan Martínez-Sykora, Mats Carlsson, Luc Rouppe van der Voort","doi":"10.1051/0004-6361/202557602","DOIUrl":"https://doi.org/10.1051/0004-6361/202557602","url":null,"abstract":"<i>Context.<i/> The formation mechanism for the dynamic type II spicules has remained elusive for many years. Their dynamical behaviour has long been linked to magnetic reconnection, yet no conclusive evidence has been provided. However, one recent observational study found signs of magnetic reconnection, as traced by Ellerman bombs (EBs), at the footpoints of many spicules. The triggering of EBs is generally linked to magnetic reconnection due to flux emergence and convective motions in the photosphere.<i>Aims.<i/> We aim to explore whether we can connect EBs to type II spicules, and determine to what extent we can use EBs as an observational proxy to probe magnetic reconnection in this dynamic. We also aim to provide further insight into the mechanisms that trigger EBs.<i>Methods.<i/> We used a simulation run with the radiative magnetohydrodynamics code Bifrost to track spicules and study the physical processes underlying their formation. To detect EBs and classify the spicules, we synthesised the chromospheric H<i>α<i/> spectral line using the multilevel radiative transfer code RH1.5D. We also traced shocks and current sheets to decipher the origin of EBs and spicules. We selected one type II spicule with a strong EB near its footpoint and studied their formation in detail.<i>Results.<i/> A magnetoacoustic shock advects the magnetic field lines towards an oppositely directed ambient field, creating a current sheet. The current sheet accelerates dense plasma via a whiplash effect generated by magnetic reconnection into the inclined ambient field, launching the spicule. Several EB profiles trace shock- and magnetic-reconnection-induced dynamics during this process at the spicule footpoint.<i>Conclusions.<i/> We present a new EB triggering mechanism in which a shock-induced current sheet reconnects, triggering an EB in the lower solar atmosphere. The shock-induced current sheet generates the upwards propagation of a type II spicule via reconnection outflows. These results provide a plausible physical origin for the recently observed connection between EBs and spicules.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"187 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146006203","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 : 2026-01-15DOI: 10.1051/0004-6361/202557293
Angelos Nersesian, Yasha Kaushal, Marco Martorano, Arjen van der Wel, Po-Feng Wu, Rachel Bezanson, Eric F. Bell, Francesco D’Eugenio, Anna R. Gallazzi, Joel Leja, Stefano Zibetti, Sandro Tacchella
Aims. We analyzed the sizes and star formation histories (SFHs) of 2908 galaxies with M★ ≥ 109 M⊙ at 0.6 < z < 1.0, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. The goal is to investigate the connection between galaxy sizes with SFH, stellar age, and metallicity.Methods. The SFHs were derived with Prospector by fitting the high signal-to-noise ratio, high spectral resolution spectroscopy drawn from the LEGA-C DR3 together with the broadband photometry from the UltraVISTA catalog. The galaxy sizes were measured by fitting a 2D Sérsic profile to the HST ACS F814W images.Results. We find diverse SFHs and quenching timescales (τq). The main quiescent population quenched over τq = 1.23 ± 0.04 Gyr, whereas the compact post-starburst galaxies (PSBs) quenched much faster, τq = 0.13 ± 0.03 Gyr. At fixed stellar mass, smaller quiescent galaxies quenched more rapidly than larger ones; at fixed size, the dependence on stellar mass is weak. Larger quiescent galaxies are marginally younger, quenched more slowly, and have near-solar metallicities, while compact quiescent galaxies are older, metal-rich, and quenched faster. PSBs formed half their mass later (zform ∼ 1.9) and quenched on the shortest timescales. The general trends with galaxy size, Z★, and zform for the quiescent populations remain consistent regardless of the method used to derive the stellar properties.Conclusions. We conclude that compact quiescent galaxies are consistent with both early moderately fast quenching and with more rapid late quenching. While this may suggest the existence of multiple quenching channels, our data are also compatible with a continuous distribution of quenching timescales. These findings suggest that different physical mechanisms may drive quenching across galaxy populations, potentially leading to similar morphological outcomes despite the differing evolutionary histories.
{"title":"The LEGA-C galaxy survey: Multiple quenching channels for quiescent galaxies at z ∼ 1","authors":"Angelos Nersesian, Yasha Kaushal, Marco Martorano, Arjen van der Wel, Po-Feng Wu, Rachel Bezanson, Eric F. Bell, Francesco D’Eugenio, Anna R. Gallazzi, Joel Leja, Stefano Zibetti, Sandro Tacchella","doi":"10.1051/0004-6361/202557293","DOIUrl":"https://doi.org/10.1051/0004-6361/202557293","url":null,"abstract":"<i>Aims.<i/> We analyzed the sizes and star formation histories (SFHs) of 2908 galaxies with <i>M<i/><sub>★<sub/> ≥ 10<sup>9<sup/> M<sub>⊙<sub/> at 0.6 < <i>z<i/> < 1.0, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. The goal is to investigate the connection between galaxy sizes with SFH, stellar age, and metallicity.<i>Methods.<i/> The SFHs were derived with Prospector by fitting the high signal-to-noise ratio, high spectral resolution spectroscopy drawn from the LEGA-C DR3 together with the broadband photometry from the UltraVISTA catalog. The galaxy sizes were measured by fitting a 2D Sérsic profile to the <i>HST<i/> ACS F814W images.<i>Results.<i/> We find diverse SFHs and quenching timescales (<i>τ<i/><sub>q<sub/>). The main quiescent population quenched over <i>τ<i/><sub>q<sub/> = 1.23 ± 0.04 Gyr, whereas the compact post-starburst galaxies (PSBs) quenched much faster, <i>τ<i/><sub>q<sub/> = 0.13 ± 0.03 Gyr. At fixed stellar mass, smaller quiescent galaxies quenched more rapidly than larger ones; at fixed size, the dependence on stellar mass is weak. Larger quiescent galaxies are marginally younger, quenched more slowly, and have near-solar metallicities, while compact quiescent galaxies are older, metal-rich, and quenched faster. PSBs formed half their mass later (<i>z<i/><sub>form<sub/> ∼ 1.9) and quenched on the shortest timescales. The general trends with galaxy size, <i>Z<i/><sub>★<sub/>, and <i>z<i/><sub>form<sub/> for the quiescent populations remain consistent regardless of the method used to derive the stellar properties.<i>Conclusions.<i/> We conclude that compact quiescent galaxies are consistent with both early moderately fast quenching and with more rapid late quenching. While this may suggest the existence of multiple quenching channels, our data are also compatible with a continuous distribution of quenching timescales. These findings suggest that different physical mechanisms may drive quenching across galaxy populations, potentially leading to similar morphological outcomes despite the differing evolutionary histories.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"100 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972362","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}
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