Pub Date : 2023-11-01DOI: 10.3847/1538-4357/acf75b
Yang Guo, Jinhan Guo, Yiwei Ni, M. D. Ding, P. F. Chen, Chun Xia, Rony Keppens, Kai E. Yang
Abstract Solar eruptive activities could occur in weak magnetic field environments and over large spatial scales, which are especially relevant to eruptions involving intermediate or quiescent solar filaments. To handle the large scales, we implement and apply a flux rope embedding method using regularized Biot–Savart laws in the spherical coordinate system. Combined with a potential field source surface model and a magneto-frictional method, a nonlinear force-free field comprising a flux rope embedded in a potential field is constructed. Using the combined nonlinear force-free field as the initial condition, we then perform a zero- β data-constrained magnetohydrodynamic (MHD) simulation for an M8.7 flare at 03:38 UT on 2012 January 23. The MHD model reproduces the eruption process, flare ribbon evolution (represented by the quasi-separatrix layer evolution), and kinematics of the flux rope. This approach could potentially model global-scale eruptions from weak field regions.
{"title":"Data-constrained Magnetohydrodynamic Simulation of an Intermediate Solar Filament Eruption","authors":"Yang Guo, Jinhan Guo, Yiwei Ni, M. D. Ding, P. F. Chen, Chun Xia, Rony Keppens, Kai E. Yang","doi":"10.3847/1538-4357/acf75b","DOIUrl":"https://doi.org/10.3847/1538-4357/acf75b","url":null,"abstract":"Abstract Solar eruptive activities could occur in weak magnetic field environments and over large spatial scales, which are especially relevant to eruptions involving intermediate or quiescent solar filaments. To handle the large scales, we implement and apply a flux rope embedding method using regularized Biot–Savart laws in the spherical coordinate system. Combined with a potential field source surface model and a magneto-frictional method, a nonlinear force-free field comprising a flux rope embedded in a potential field is constructed. Using the combined nonlinear force-free field as the initial condition, we then perform a zero- β data-constrained magnetohydrodynamic (MHD) simulation for an M8.7 flare at 03:38 UT on 2012 January 23. The MHD model reproduces the eruption process, flare ribbon evolution (represented by the quasi-separatrix layer evolution), and kinematics of the flux rope. This approach could potentially model global-scale eruptions from weak field regions.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135515066","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 : 2023-11-01DOI: 10.3847/1538-4357/acf9a3
Ze-Nan Liu, Jin-Jun Geng, Yuan-Pei Yang, Wei-Yang Wang, Zi-Gao Dai
Abstract Fast radio bursts (FRBs) are extragalactic radio transients with extremely high brightness temperature, which strongly suggests the presence of coherent emission mechanisms. In this study, we introduce a novel radiation mechanism for FRBs involving coherent Cherenkov radiation (ChR) emitted by bunched particles that may originate within the magnetosphere of a magnetar. We assume that some relativistic particles are emitted from the polar cap of a magnetar and move along magnetic field lines through a charge-separated magnetic plasma, emitting coherent ChR along their trajectory. The crucial condition for ChR to occur is that the refractive index of the plasma medium, denoted as n r , must satisfy the condition nr2>1 . We conduct comprehensive calculations to determine various characteristics of ChR, including its characteristic frequency, emission power, required parallel electric field, and coherence factor. Notably, our proposed bunched coherent ChR mechanism has the remarkable advantage of generating a narrower-band spectrum. Furthermore, a frequency downward-drifting pattern and ∼100% linearly polarized emission can be predicted within the framework of this emission mechanism.
快速射电暴(FRBs)是一种具有极高亮度温度的河外射电瞬变现象，强烈表明存在相干发射机制。在这项研究中，我们引入了一种新的快速射电暴辐射机制，涉及由可能起源于磁星磁层内的束状粒子发射的相干切伦科夫辐射(ChR)。我们假设一些相对论性粒子从磁星的极帽发射出来，沿着磁力线穿过电荷分离的磁等离子体，沿着它们的轨迹发射出相干的ChR。ChR发生的关键条件是等离子体介质的折射率，记为n r，必须满足条件n r 2 >1。我们进行了综合计算，确定了ChR的各种特性，包括其特征频率、发射功率、所需并联电场和相干系数。值得注意的是，我们提出的聚束相干ChR机制具有产生窄带频谱的显著优势。此外，在这种发射机制的框架内，可以预测频率向下漂移模式和~ 100%线极化发射。
{"title":"Coherent Cherenkov Radiation by Bunches in Fast Radio Bursts","authors":"Ze-Nan Liu, Jin-Jun Geng, Yuan-Pei Yang, Wei-Yang Wang, Zi-Gao Dai","doi":"10.3847/1538-4357/acf9a3","DOIUrl":"https://doi.org/10.3847/1538-4357/acf9a3","url":null,"abstract":"Abstract Fast radio bursts (FRBs) are extragalactic radio transients with extremely high brightness temperature, which strongly suggests the presence of coherent emission mechanisms. In this study, we introduce a novel radiation mechanism for FRBs involving coherent Cherenkov radiation (ChR) emitted by bunched particles that may originate within the magnetosphere of a magnetar. We assume that some relativistic particles are emitted from the polar cap of a magnetar and move along magnetic field lines through a charge-separated magnetic plasma, emitting coherent ChR along their trajectory. The crucial condition for ChR to occur is that the refractive index of the plasma medium, denoted as n r , must satisfy the condition <?CDATA ${n}_{r}^{2}gt 1$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>r</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>></mml:mo> <mml:mn>1</mml:mn> </mml:math> . We conduct comprehensive calculations to determine various characteristics of ChR, including its characteristic frequency, emission power, required parallel electric field, and coherence factor. Notably, our proposed bunched coherent ChR mechanism has the remarkable advantage of generating a narrower-band spectrum. Furthermore, a frequency downward-drifting pattern and ∼100% linearly polarized emission can be predicted within the framework of this emission mechanism.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"137 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566304","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 : 2023-11-01DOI: 10.3847/1538-4357/acfd30
Jongho Park, Keiichi Asada, Do-Young Byun
Abstract We present a new method of time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). This method has been implemented in the recently developed polarization calibration pipeline GPCAL. Instrumental polarization, also known as polarimetric leakage, is a direction-dependent effect, and it is not constant across the beam of a telescope. Antenna pointing model accuracy is usually dependent on time, resulting in off-axis polarimetric leakages that can vary with time. The method is designed to correct for the off-axis leakages with large amplitudes that can severely degrade linear polarization images. Using synthetic data generated based on real Very Long Baseline Array (VLBA) data observed at 43 GHz, we evaluate the performance of the method. It was able to reproduce the off-axis leakages assumed in the synthetic data, particularly those with large amplitudes. The method has been applied to two sets of real VLBA data, and the derived off-axis leakages show very similar trends over time for pairs of nearby sources. Furthermore, the amplitudes of the off-axis leakages are strongly correlated with the antenna gain correction factors. The results demonstrate that the method is capable of correcting for the off-axis leakages present in VLBI data. By calibrating time-dependent instrumental polarization, the rms noise levels of the updated linear polarization images have been significantly reduced. The method is expected to substantially enhance the quality of linear polarization images obtained from existing and future VLBI observations.
{"title":"Calibrating VLBI Polarization Data Using GPCAL. II. Time-dependent Calibration","authors":"Jongho Park, Keiichi Asada, Do-Young Byun","doi":"10.3847/1538-4357/acfd30","DOIUrl":"https://doi.org/10.3847/1538-4357/acfd30","url":null,"abstract":"Abstract We present a new method of time-dependent instrumental polarization calibration for very long baseline interferometry (VLBI). This method has been implemented in the recently developed polarization calibration pipeline GPCAL. Instrumental polarization, also known as polarimetric leakage, is a direction-dependent effect, and it is not constant across the beam of a telescope. Antenna pointing model accuracy is usually dependent on time, resulting in off-axis polarimetric leakages that can vary with time. The method is designed to correct for the off-axis leakages with large amplitudes that can severely degrade linear polarization images. Using synthetic data generated based on real Very Long Baseline Array (VLBA) data observed at 43 GHz, we evaluate the performance of the method. It was able to reproduce the off-axis leakages assumed in the synthetic data, particularly those with large amplitudes. The method has been applied to two sets of real VLBA data, and the derived off-axis leakages show very similar trends over time for pairs of nearby sources. Furthermore, the amplitudes of the off-axis leakages are strongly correlated with the antenna gain correction factors. The results demonstrate that the method is capable of correcting for the off-axis leakages present in VLBI data. By calibrating time-dependent instrumental polarization, the rms noise levels of the updated linear polarization images have been significantly reduced. The method is expected to substantially enhance the quality of linear polarization images obtained from existing and future VLBI observations.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"49 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135566705","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 : 2023-11-01DOI: 10.3847/1538-4357/ad003a
Travis J. Thieme, Shih-Ping Lai, Nagayoshi Ohashi, John J. Tobin, Jes K. Jørgensen, Jinshi Sai (Insa Choi), Yusuke Aso, Jonathan P. Williams, Yoshihide Yamato, Yuri Aikawa, Itziar de Gregorio-Monsalvo, Ilseung Han, Woojin Kwon, Chang Won Lee, Jeong-Eun Lee, Zhi-Yun Li, Zhe-Yu Daniel Lin, Leslie W. Looney, Suchitra Narayanan, Nguyen Thi Phuong, Adele L. Plunkett, Alejandro Santamaría-Miranda, Rajeeb Sharma, Shigehisa Takakuwa, Hsi-Wei Yen
Abstract Protostellar disks are an ubiquitous part of the star formation process and the future sites of planet formation. As part of the Early Planet Formation in Embedded Disks large program, we present high angular resolution dust continuum (∼40 mas) and molecular line (∼150 mas) observations of the Class 0 protostar IRAS 15398–3359. The dust continuum is small, compact, and centrally peaked, while more extended dust structures are found in the outflow directions. We perform a 2D Gaussian fitting and find the deconvolved size and 2 σ radius of the dust disk to be 4.5 × 2.8 au and 3.8 au, respectively. We estimate the gas+dust disk mass assuming optically thin continuum emission to be 0.6 M J –1.8 M J , indicating a very low mass disk. The CO isotopologues trace components of the outflows and inner envelope, while SO traces a compact, rotating disk-like component. Using several rotation curve fittings on the position–velocity diagram of the SO emission, the lower limits of the protostellar mass and gas disk radius are 0.022 M ⊙ and 31.2 au, respectively, from our Modified 2 single power-law fitting. A conservative upper limit of the protostellar mass is inferred to be 0.1 M ⊙ . The protostellar mass accretion rate and the specific angular momentum at the protostellar disk edge are found to be in the range of (1.3–6.1) × 10 −6 M ⊙ yr −1 and (1.2–3.8) × 10 −4 km s −1 pc, respectively, with an age estimated between 0.4 × 10 4 yr and 7.5 × 10 4 yr. At this young age with no clear substructures in the disk, planet formation would likely not yet have started. This study highlights the importance of high-resolution observations and systematic fitting procedures when deriving dynamical properties of deeply embedded Class 0 protostars.
原恒星盘是恒星形成过程中无处不在的一部分，也是未来行星形成的地点。作为嵌入式圆盘早期行星形成大型项目的一部分，我们展示了0级原恒星IRAS 15398-3359的高角分辨率尘埃连续体(~ 40 mas)和分子线(~ 150 mas)观测结果。尘埃连续体小而致密，中心呈尖峰状，而在出流方向发现了更多的扩展尘埃结构。我们进行了二维高斯拟合，发现尘埃盘的反卷积尺寸和2 σ半径分别为4.5 × 2.8 au和3.8 au。假设光学薄连续辐射为0.6 M J -1.8 M J，我们估计气体+尘埃盘的质量是非常低的。CO同位素示踪组分为流出液和内包壳，而SO示踪组分为致密的旋转圆盘状组分。通过对SO发射位置-速度图的几个旋转曲线拟合，得到原恒星质量和气体盘半径的下限分别为0.022 M⊙和31.2 au。原恒星质量的保守上限被推断为0.1 M⊙。原恒星质量吸积率和原恒星盘边缘的特定角动量分别在(1.3-6.1)× 10−6 M⊙yr−1和(1.2-3.8)× 10−4 km s−1 pc的范围内，年龄估计在0.4 × 10.4年和7.5 × 10.4年之间。在这个年轻的年龄，盘内没有明确的亚结构，行星的形成可能还没有开始。这项研究强调了高分辨率观测和系统拟合程序在推导深嵌0级原恒星动力学特性时的重要性。
{"title":"Early Planet Formation in Embedded Disks (eDisk). VIII. A Small Protostellar Disk around the Extremely Low Mass and Young Class 0 Protostar IRAS 15398–3359","authors":"Travis J. Thieme, Shih-Ping Lai, Nagayoshi Ohashi, John J. Tobin, Jes K. Jørgensen, Jinshi Sai (Insa Choi), Yusuke Aso, Jonathan P. Williams, Yoshihide Yamato, Yuri Aikawa, Itziar de Gregorio-Monsalvo, Ilseung Han, Woojin Kwon, Chang Won Lee, Jeong-Eun Lee, Zhi-Yun Li, Zhe-Yu Daniel Lin, Leslie W. Looney, Suchitra Narayanan, Nguyen Thi Phuong, Adele L. Plunkett, Alejandro Santamaría-Miranda, Rajeeb Sharma, Shigehisa Takakuwa, Hsi-Wei Yen","doi":"10.3847/1538-4357/ad003a","DOIUrl":"https://doi.org/10.3847/1538-4357/ad003a","url":null,"abstract":"Abstract Protostellar disks are an ubiquitous part of the star formation process and the future sites of planet formation. As part of the Early Planet Formation in Embedded Disks large program, we present high angular resolution dust continuum (∼40 mas) and molecular line (∼150 mas) observations of the Class 0 protostar IRAS 15398–3359. The dust continuum is small, compact, and centrally peaked, while more extended dust structures are found in the outflow directions. We perform a 2D Gaussian fitting and find the deconvolved size and 2 σ radius of the dust disk to be 4.5 × 2.8 au and 3.8 au, respectively. We estimate the gas+dust disk mass assuming optically thin continuum emission to be 0.6 M J –1.8 M J , indicating a very low mass disk. The CO isotopologues trace components of the outflows and inner envelope, while SO traces a compact, rotating disk-like component. Using several rotation curve fittings on the position–velocity diagram of the SO emission, the lower limits of the protostellar mass and gas disk radius are 0.022 M ⊙ and 31.2 au, respectively, from our Modified 2 single power-law fitting. A conservative upper limit of the protostellar mass is inferred to be 0.1 M ⊙ . The protostellar mass accretion rate and the specific angular momentum at the protostellar disk edge are found to be in the range of (1.3–6.1) × 10 −6 M ⊙ yr −1 and (1.2–3.8) × 10 −4 km s −1 pc, respectively, with an age estimated between 0.4 × 10 4 yr and 7.5 × 10 4 yr. At this young age with no clear substructures in the disk, planet formation would likely not yet have started. This study highlights the importance of high-resolution observations and systematic fitting procedures when deriving dynamical properties of deeply embedded Class 0 protostars.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"14 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714564","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 : 2023-11-01DOI: 10.3847/1538-4357/acfd25
Emanuele Contini, Seyoung Jeon, Jinsu Rhee, San Han, Sukyoung K. Yi
Abstract We investigate the role of halo concentration in the formation of intracluster light (ICL) in galaxy groups and clusters, as predicted by a state-of-the-art semianalytic model of galaxy formation, coupled with a set of high-resolution dark-matter-only simulations. The analysis focuses on how the fraction of ICL correlates with halo mass, concentration, and fraction of early-type galaxies (ETGs) in a large sample of groups and clusters with 13.0≤logMhalo≤15.0 . The fraction of ICL follows a normal distribution, a consequence of the stochastic nature of the physical processes responsible for the formation of the diffuse light. The fractional budget of ICL depends on both halo mass (very weakly) until group scales, and concentration (remarkably). More interestingly, the ICL fraction is higher in more concentrated objects, a result of the stronger tidal forces acting in the innermost regions of the halos where the concentration is the quantity playing the most relevant role. Our model predictions do not show any dependence between the ICL and ETGs fractions, and so we instead suggest the concentration rather than the mass, as recently claimed, to be the main driver of the ICL formation. The diffuse light starts to form in groups via stellar stripping and mergers and later assembled in more-massive objects. However, the formation and assembly keep going on group/cluster scales at lower redshift through the same processes, mainly via stellar stripping in the vicinity of the central regions where tidal forces are stronger.
{"title":"The Intracluster Light and Its Link with the Dynamical State of the Host Group/Cluster: The Role of the Halo Concentration","authors":"Emanuele Contini, Seyoung Jeon, Jinsu Rhee, San Han, Sukyoung K. Yi","doi":"10.3847/1538-4357/acfd25","DOIUrl":"https://doi.org/10.3847/1538-4357/acfd25","url":null,"abstract":"Abstract We investigate the role of halo concentration in the formation of intracluster light (ICL) in galaxy groups and clusters, as predicted by a state-of-the-art semianalytic model of galaxy formation, coupled with a set of high-resolution dark-matter-only simulations. The analysis focuses on how the fraction of ICL correlates with halo mass, concentration, and fraction of early-type galaxies (ETGs) in a large sample of groups and clusters with <?CDATA $13.0leqslant mathrm{log}{M}_{mathrm{halo}}leqslant 15.0$?> <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mn>13.0</mml:mn> <mml:mo>≤</mml:mo> <mml:mi>log</mml:mi> <mml:msub> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>halo</mml:mi> </mml:mrow> </mml:msub> <mml:mo>≤</mml:mo> <mml:mn>15.0</mml:mn> </mml:math> . The fraction of ICL follows a normal distribution, a consequence of the stochastic nature of the physical processes responsible for the formation of the diffuse light. The fractional budget of ICL depends on both halo mass (very weakly) until group scales, and concentration (remarkably). More interestingly, the ICL fraction is higher in more concentrated objects, a result of the stronger tidal forces acting in the innermost regions of the halos where the concentration is the quantity playing the most relevant role. Our model predictions do not show any dependence between the ICL and ETGs fractions, and so we instead suggest the concentration rather than the mass, as recently claimed, to be the main driver of the ICL formation. The diffuse light starts to form in groups via stellar stripping and mergers and later assembled in more-massive objects. However, the formation and assembly keep going on group/cluster scales at lower redshift through the same processes, mainly via stellar stripping in the vicinity of the central regions where tidal forces are stronger.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"139 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135714766","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 : 2023-11-01DOI: 10.3847/1538-4357/acfc1a
J.-D. do Nascimento, S. A. Barnes, S. H. Saar, G. F. Porto de Mello, J. C. Hall, F. Anthony, L. de Almeida, E. N. Velloso, J. S. da Costa, P. Petit, A. Strugarek, B. J. Wargelin, M. Castro, K. G. Strassmeier, A. S. Brun
Abstract Characterizing the cyclic magnetic activity of stars that are close approximations of our Sun offers our best hope for understanding our Sun’s current and past magnetism, the space weather around solar-type stars, and more generally, the dynamos of other cool stars. The nearest current approximation to the Sun is the solar twin 18 Scorpii, a naked-eye Sun-like star of spectral type G2 Va. However, while 18 Scorpii’s physical parameters closely match those of the Sun, its activity cycle is about 7 yr, and shorter than the solar cycle. We report the measurement of a periodicity of 15 yr that corresponds to a longer activity cycle for 18 Scorpii based on observations extending to the last three decades. The global magnetic geometry of 18 Scorpii changes with this 15 yr cycle and appears to be equivalent to the solar 22 yr magnetic polarity cycle. These results suggest that 18 Scorpii is also a magnetic proxy for a younger Sun, adding an important new datum for testing dynamo theory and magnetic evolution of low-mass stars. The results perturb our understanding of the relationship between cycle and rotation, constrain the Sun’s magnetism and the Sun–Earth connection over the past billion years, and suggest that solar Schwabe and Hale cycle periods have increased over that time span.
{"title":"A Hale-like Cycle in the Solar Twin 18 Scorpii","authors":"J.-D. do Nascimento, S. A. Barnes, S. H. Saar, G. F. Porto de Mello, J. C. Hall, F. Anthony, L. de Almeida, E. N. Velloso, J. S. da Costa, P. Petit, A. Strugarek, B. J. Wargelin, M. Castro, K. G. Strassmeier, A. S. Brun","doi":"10.3847/1538-4357/acfc1a","DOIUrl":"https://doi.org/10.3847/1538-4357/acfc1a","url":null,"abstract":"Abstract Characterizing the cyclic magnetic activity of stars that are close approximations of our Sun offers our best hope for understanding our Sun’s current and past magnetism, the space weather around solar-type stars, and more generally, the dynamos of other cool stars. The nearest current approximation to the Sun is the solar twin 18 Scorpii, a naked-eye Sun-like star of spectral type G2 Va. However, while 18 Scorpii’s physical parameters closely match those of the Sun, its activity cycle is about 7 yr, and shorter than the solar cycle. We report the measurement of a periodicity of 15 yr that corresponds to a longer activity cycle for 18 Scorpii based on observations extending to the last three decades. The global magnetic geometry of 18 Scorpii changes with this 15 yr cycle and appears to be equivalent to the solar 22 yr magnetic polarity cycle. These results suggest that 18 Scorpii is also a magnetic proxy for a younger Sun, adding an important new datum for testing dynamo theory and magnetic evolution of low-mass stars. The results perturb our understanding of the relationship between cycle and rotation, constrain the Sun’s magnetism and the Sun–Earth connection over the past billion years, and suggest that solar Schwabe and Hale cycle periods have increased over that time span.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"21 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135715172","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 : 2023-11-01DOI: 10.3847/1538-4357/acf92f
Anirban Roy, Dariannette Valentín-Martínez, Kailai Wang, Nicholas Battaglia, Alexander van Engelen
Abstract Mapping of multiple lines such as the fine-structure emission from [C ii ] (157.7 μ m), [O iii ] (52 and 88.4 μ m), and rotational emission lines from CO are of particular interest for upcoming line intensity mapping (LIM) experiments at millimeter wavelengths, due to their brightness features. Several upcoming experiments aim to cover a broad range of scientific goals, from detecting signatures of the epoch of reionization to the physics of star formation and its role in galaxy evolution. In this paper, we develop a semianalytic approach to modeling line strengths as functions of the star formation rate (SFR) or infrared luminosity based on observations of local and high- z galaxies. This package, LIMpy (Line Intensity Mapping in Python), estimates the intensity and power spectra of [C ii ], [O iii ], and CO rotational transition lines up to the J levels (1–0) to (13–12) based both on analytic formalism and on simulations. We develop a relation among halo mass, SFR, and multiline intensities that permits us to construct a generic formula for the evolution of several line strengths up to z ∼ 10. We implement a variety of star formation models and multiline luminosity relations to estimate the astrophysical uncertainties on the intensity power spectrum of these lines. As a demonstration, we predict the signal-to-noise ratio of [C ii ] detection for an EoR-Spec-like instrument on the Fred Young Submillimeter Telescope. Furthermore, the ability to use any halo catalog allows the LIMpy code to be easily integrated into existing simulation pipelines, providing a flexible tool to study intensity mapping in the context of complex galaxy formation physics.
{"title":"LIMpy: A Semianalytic Approach to Simulating Multiline Intensity Maps at Millimeter Wavelengths","authors":"Anirban Roy, Dariannette Valentín-Martínez, Kailai Wang, Nicholas Battaglia, Alexander van Engelen","doi":"10.3847/1538-4357/acf92f","DOIUrl":"https://doi.org/10.3847/1538-4357/acf92f","url":null,"abstract":"Abstract Mapping of multiple lines such as the fine-structure emission from [C ii ] (157.7 μ m), [O iii ] (52 and 88.4 μ m), and rotational emission lines from CO are of particular interest for upcoming line intensity mapping (LIM) experiments at millimeter wavelengths, due to their brightness features. Several upcoming experiments aim to cover a broad range of scientific goals, from detecting signatures of the epoch of reionization to the physics of star formation and its role in galaxy evolution. In this paper, we develop a semianalytic approach to modeling line strengths as functions of the star formation rate (SFR) or infrared luminosity based on observations of local and high- z galaxies. This package, LIMpy (Line Intensity Mapping in Python), estimates the intensity and power spectra of [C ii ], [O iii ], and CO rotational transition lines up to the J levels (1–0) to (13–12) based both on analytic formalism and on simulations. We develop a relation among halo mass, SFR, and multiline intensities that permits us to construct a generic formula for the evolution of several line strengths up to z ∼ 10. We implement a variety of star formation models and multiline luminosity relations to estimate the astrophysical uncertainties on the intensity power spectrum of these lines. As a demonstration, we predict the signal-to-noise ratio of [C ii ] detection for an EoR-Spec-like instrument on the Fred Young Submillimeter Telescope. Furthermore, the ability to use any halo catalog allows the LIMpy code to be easily integrated into existing simulation pipelines, providing a flexible tool to study intensity mapping in the context of complex galaxy formation physics.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"28 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371889","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 : 2023-11-01DOI: 10.3847/1538-4357/acf466
Marijana Smailagić, Jason Xavier Prochaska, Joseph Burchett, Guangtun Zhu
Abstract We study ultraviolet H i and metal-line transitions in the circumgalactic medium (CGM) of 15 massive, quenched luminous red galaxies (LRGs) at redshift z ∼ 0.5 and with impact parameters up to 400 kpc. We selected eight LRG–CGM systems to study general properties of the CGM around LRGs, while the other seven are already known to contain cool CGM gas from Mg ii optical studies (Mg ii -LRGs). In the general LRG population, we detect H i in four of eight LRGs, in all cases with N H I < 10 16.7 cm −2 . In contrast, all Mg ii -LRGs show H i ; for four LRGs, the H i column density is N H I ≳ 10 18 cm −2 . The CGM of LRGs also shows low and intermediate ionized lines (such as C iii , C ii , Si iii , and Si ii ) and highly ionized lines of O vi (we detect O vi around five of seven Mg ii -LRGs and one of eight in the random sample). Next, we combine our sample with literature LRGs and ≲ L * galaxies, and we find that while for ≲ L * galaxies CGM H i Ly α absorption is stronger as galaxies are more massive, the cool CGM traced by H i Ly α is suppressed above stellar masses of M * ∼ 10 11.5 M ☉ . While most LRG–CGM systems show weak or nondetectable O vi (equivalent width < 0.2 Å), a few LRG–CGM systems show strong O vi 1031, which in most cases likely originates from groups containing both an LRG and a blue star-forming neighboring galaxy.
摘要研究了15个大质量、淬灭红星系(LRGs)在红移z ~ 0.5、冲击参数高达400kpc的环星系介质(CGM)中的紫外H和金属谱线跃迁。我们选择了8个LRG-CGM系统来研究LRGs周围CGM的一般性质，而其他7个已经从Mg ii光学研究中已知含有冷CGM气体(Mg ii -LRGs)。在一般LRG人群中，我们在8个LRG中检测到4个i，在所有的nh i <病例中;10 16.7 cm−2。相反，所有Mg ii -LRGs均显示H i;对于4个LRGs, H i柱密度为N H i > 10 18 cm−2。LRGs的CGM也显示出低和中等电离谱线(如C iii、C ii、Si iii和Si ii)和O vi的高电离谱线(我们在7个Mg ii -LRGs中检测到5个O vi，在随机样本中检测到8个O vi)。接下来，我们将我们的样本与文献LRGs和> L *星系结合起来，我们发现对于> L *星系，随着星系质量的增加，CGM H i Ly α的吸收更强，而H i Ly α追踪到的冷CGM在恒星质量M * ~ 10 11.5 M☉以上被抑制。虽然大多数LRG-CGM系统显示弱或不可检测的O vi(等效宽度<0.2 Å)，一些LRG - cgm系统显示出强烈的O vi 1031，在大多数情况下，它可能来自包含LRG和蓝色恒星形成邻近星系的星系群。
{"title":"Circumgalactic Medium at High Halo Masses—Signatures of Cold Gas Depletion in Luminous Red Galaxies","authors":"Marijana Smailagić, Jason Xavier Prochaska, Joseph Burchett, Guangtun Zhu","doi":"10.3847/1538-4357/acf466","DOIUrl":"https://doi.org/10.3847/1538-4357/acf466","url":null,"abstract":"Abstract We study ultraviolet H i and metal-line transitions in the circumgalactic medium (CGM) of 15 massive, quenched luminous red galaxies (LRGs) at redshift z ∼ 0.5 and with impact parameters up to 400 kpc. We selected eight LRG–CGM systems to study general properties of the CGM around LRGs, while the other seven are already known to contain cool CGM gas from Mg ii optical studies (Mg ii -LRGs). In the general LRG population, we detect H i in four of eight LRGs, in all cases with N H I < 10 16.7 cm −2 . In contrast, all Mg ii -LRGs show H i ; for four LRGs, the H i column density is N H I ≳ 10 18 cm −2 . The CGM of LRGs also shows low and intermediate ionized lines (such as C iii , C ii , Si iii , and Si ii ) and highly ionized lines of O vi (we detect O vi around five of seven Mg ii -LRGs and one of eight in the random sample). Next, we combine our sample with literature LRGs and ≲ L * galaxies, and we find that while for ≲ L * galaxies CGM H i Ly α absorption is stronger as galaxies are more massive, the cool CGM traced by H i Ly α is suppressed above stellar masses of M * ∼ 10 11.5 M ☉ . While most LRG–CGM systems show weak or nondetectable O vi (equivalent width < 0.2 Å), a few LRG–CGM systems show strong O vi 1031, which in most cases likely originates from groups containing both an LRG and a blue star-forming neighboring galaxy.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"28 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135371890","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 : 2023-11-01DOI: 10.3847/1538-4357/acfb88
Takeru K. Suzuki
Abstract By performing ideal magnetohydrodynamical (MHD) simulations with weak vertical magnetic fields in unstratified cylindrical shearing boxes with modified boundary treatment, we investigate MHD turbulence excited by magnetorotational instability. The cylindrical simulation exhibits extremely large temporal variation in the magnetic activity compared with the simulation in a normal Cartesian shearing box, although the time-averaged field strengths are comparable in the cylindrical and Cartesian setups. Detailed analysis of the terms describing magnetic energy evolution with “triangle diagrams” surprisingly reveals that in the cylindrical simulation the compression of toroidal magnetic field is unexpectedly as important as the winding due to differential rotation in amplifying magnetic fields and triggering intermittent magnetic bursts, which are not seen in the Cartesian simulation. The importance of the compressible amplification is also true for a cylindrical simulation with tiny curvature; the evolution of magnetic fields in the nearly Cartesian shearing box simulation is fundamentally different from that in the exact Cartesian counterpart. The radial gradient of epicyclic frequency , κ , which cannot be considered in the normal Cartesian shearing box model, is the cause of this fundamental difference. An additional consequence of the spatial variation of κ is continuous and ubiquitous formation of narrow high-density (low-density) and weak-field (strong-field) localized structures; seeds of these ring gap structures are created by the compressible effect and subsequently amplified and maintained under the marginally unstable condition regarding “viscous-type” instability.
{"title":"MHD in a Cylindrical Shearing Box. II. Intermittent Bursts and Substructures in MRI Turbulence","authors":"Takeru K. Suzuki","doi":"10.3847/1538-4357/acfb88","DOIUrl":"https://doi.org/10.3847/1538-4357/acfb88","url":null,"abstract":"Abstract By performing ideal magnetohydrodynamical (MHD) simulations with weak vertical magnetic fields in unstratified cylindrical shearing boxes with modified boundary treatment, we investigate MHD turbulence excited by magnetorotational instability. The cylindrical simulation exhibits extremely large temporal variation in the magnetic activity compared with the simulation in a normal Cartesian shearing box, although the time-averaged field strengths are comparable in the cylindrical and Cartesian setups. Detailed analysis of the terms describing magnetic energy evolution with “triangle diagrams” surprisingly reveals that in the cylindrical simulation the compression of toroidal magnetic field is unexpectedly as important as the winding due to differential rotation in amplifying magnetic fields and triggering intermittent magnetic bursts, which are not seen in the Cartesian simulation. The importance of the compressible amplification is also true for a cylindrical simulation with tiny curvature; the evolution of magnetic fields in the nearly Cartesian shearing box simulation is fundamentally different from that in the exact Cartesian counterpart. The radial gradient of epicyclic frequency , κ , which cannot be considered in the normal Cartesian shearing box model, is the cause of this fundamental difference. An additional consequence of the spatial variation of κ is continuous and ubiquitous formation of narrow high-density (low-density) and weak-field (strong-field) localized structures; seeds of these ring gap structures are created by the compressible effect and subsequently amplified and maintained under the marginally unstable condition regarding “viscous-type” instability.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135410185","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 : 2023-11-01DOI: 10.3847/1538-4357/acfd91
Gabor Toth, Marco Velli, Bart van der Holst
Abstract Magnetic switchbacks are rapid high-amplitude reversals of the radial magnetic field in the solar wind that do not involve a heliospheric current sheet crossing. First seen sporadically in the 1970s in Mariner and Helios data, switchbacks were later observed by the Ulysses spacecraft beyond 1 au and have been recently discovered to be a typical component of solar wind fluctuations in the inner heliosphere by the Parker Solar Probe spacecraft. While switchbacks are now well understood to be spherically polarized Alfvén waves thanks to Parker Solar Probe observations, their formation has been an intriguing and unsolved puzzle. Here we provide a simple yet predictive theory for the formation of these magnetic reversals: the switchbacks are produced by the distortion and twisting of circularly polarized Alfvén waves by a transversely varying radial wave propagation velocity. We provide an analytic expression for the magnetic field variation, establish the necessary and sufficient conditions for the formation of switchbacks, and show that the proposed mechanism works in a realistic solar wind scenario. We also show that the theoretical predictions are in excellent agreement with observations, and the high-amplitude radial oscillations are strongly correlated with the shear of the wave propagation speed. The correlation coefficient is around 0.3–0.5 for both encounter 1 and encounter 12. The probability of this being a lucky coincidence is essentially zero with p -values below 0.1%.
{"title":"Theory of Magnetic Switchbacks Fully Supported by Parker Solar Probe Observations","authors":"Gabor Toth, Marco Velli, Bart van der Holst","doi":"10.3847/1538-4357/acfd91","DOIUrl":"https://doi.org/10.3847/1538-4357/acfd91","url":null,"abstract":"Abstract Magnetic switchbacks are rapid high-amplitude reversals of the radial magnetic field in the solar wind that do not involve a heliospheric current sheet crossing. First seen sporadically in the 1970s in Mariner and Helios data, switchbacks were later observed by the Ulysses spacecraft beyond 1 au and have been recently discovered to be a typical component of solar wind fluctuations in the inner heliosphere by the Parker Solar Probe spacecraft. While switchbacks are now well understood to be spherically polarized Alfvén waves thanks to Parker Solar Probe observations, their formation has been an intriguing and unsolved puzzle. Here we provide a simple yet predictive theory for the formation of these magnetic reversals: the switchbacks are produced by the distortion and twisting of circularly polarized Alfvén waves by a transversely varying radial wave propagation velocity. We provide an analytic expression for the magnetic field variation, establish the necessary and sufficient conditions for the formation of switchbacks, and show that the proposed mechanism works in a realistic solar wind scenario. We also show that the theoretical predictions are in excellent agreement with observations, and the high-amplitude radial oscillations are strongly correlated with the shear of the wave propagation speed. The correlation coefficient is around 0.3–0.5 for both encounter 1 and encounter 12. The probability of this being a lucky coincidence is essentially zero with p -values below 0.1%.","PeriodicalId":50735,"journal":{"name":"Astrophysical Journal","volume":"62 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135411379","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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