Pub Date : 2023-07-01DOI: 10.3847/2041-8213/acdb5a
Can Xu, Tao Wang, Q. Gu, A. Zanella, K. Xu, Hanwen Sun, V. Strazzullo, F. Valentino, R. Gobat, E. Daddi, D. Elbaz, M. Xiao, Shiying Lu, Luwenjia Zhou
Structural properties of cluster galaxies during their peak formation epoch, z ∼ 2–4 provide key information on whether and how the environment affects galaxy formation and evolution. Based on deep Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) imaging toward the z = 2.51 cluster, J1001, we explore environmental effects on the structure, color gradients, and stellar populations of a statistical sample of cluster star-forming galaxies (SFGs). We find that the cluster SFGs are on average smaller than their field counterparts. This difference is most pronounced at the high-mass end (M ⋆ > 1010.5 M ⊙), with nearly all of them lying below the mass–size relation of field galaxies. The high-mass cluster SFGs are also generally old, with a steep negative color gradient, indicating an early formation time likely associated with strong dissipative collapse. For low-mass cluster SFGs, we unveil a population of compact galaxies with steep positive color gradients that are not seen in the field. This suggests that the low-mass compact cluster SFGs may have already experienced strong environmental effects, e.g., tidal/ram pressure stripping, in this young cluster. These results provide evidence on the environmental effects at work in the earliest formed clusters with different roles in the formation of low- and high-mass galaxies.
{"title":"Accelerated Structural Evolution of Galaxies in a Starbursting Cluster at z = 2.51","authors":"Can Xu, Tao Wang, Q. Gu, A. Zanella, K. Xu, Hanwen Sun, V. Strazzullo, F. Valentino, R. Gobat, E. Daddi, D. Elbaz, M. Xiao, Shiying Lu, Luwenjia Zhou","doi":"10.3847/2041-8213/acdb5a","DOIUrl":"https://doi.org/10.3847/2041-8213/acdb5a","url":null,"abstract":"Structural properties of cluster galaxies during their peak formation epoch, z ∼ 2–4 provide key information on whether and how the environment affects galaxy formation and evolution. Based on deep Hubble Space Telescope (HST)/Wide Field Camera 3 (WFC3) imaging toward the z = 2.51 cluster, J1001, we explore environmental effects on the structure, color gradients, and stellar populations of a statistical sample of cluster star-forming galaxies (SFGs). We find that the cluster SFGs are on average smaller than their field counterparts. This difference is most pronounced at the high-mass end (M ⋆ > 1010.5 M ⊙), with nearly all of them lying below the mass–size relation of field galaxies. The high-mass cluster SFGs are also generally old, with a steep negative color gradient, indicating an early formation time likely associated with strong dissipative collapse. For low-mass cluster SFGs, we unveil a population of compact galaxies with steep positive color gradients that are not seen in the field. This suggests that the low-mass compact cluster SFGs may have already experienced strong environmental effects, e.g., tidal/ram pressure stripping, in this young cluster. These results provide evidence on the environmental effects at work in the earliest formed clusters with different roles in the formation of low- and high-mass galaxies.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132327261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.3847/2041-8213/ace422
Hongqiang Song, Leping Li, Zhenjun Zhou, L. Xia, Xin Cheng, Yao-wu Chen
Previous survey studies reported that coronal mass ejections (CMEs) can exhibit various structures in white-light coronagraphs, and ∼30% of them have the typical three-part feature in the high corona (e.g., 2–6 R ⊙), which has been taken as the prototypical structure of CMEs. It is widely accepted that CMEs result from eruption of magnetic flux ropes (MFRs), and the three-part structure can be understood easily by means of the MFR eruption. It is interesting and significant to answer why only ∼30% of CMEs have the three-part feature in previous studies. Here we conduct a synthesis of the CME structure in the field of view (FOV) of K-Coronagraph (1.05–3 R ⊙). In total, 369 CMEs are observed from 2013 September to 2022 November. After inspecting the CMEs one by one through joint observations of the Atmospheric Imaging Assembly, K-Coronagraph, and LASCO/C2, we find 71 events according to the criteria: (1) limb event; (2) normal CME, i.e., angular width ≥30°; (3) K-Coronagraph caught the early eruption stage. All (or more than 90% considering several ambiguous events) of the 71 CMEs exhibit the three-part feature in the FOV of K-Coronagraph, while only 30%–40% have the feature in the C2 FOV (2–6 R ⊙). For the first time, our studies show that 90%–100% and 30%–40% of normal CMEs possess the three-part structure in the low and high corona, respectively, which demonstrates that many CMEs can lose the three-part feature during their early evolutions, and strongly supports that most (if not all) CMEs have the MFR structures.
{"title":"The Structure of Coronal Mass Ejections Recorded by the K-Coronagraph at Mauna Loa Solar Observatory","authors":"Hongqiang Song, Leping Li, Zhenjun Zhou, L. Xia, Xin Cheng, Yao-wu Chen","doi":"10.3847/2041-8213/ace422","DOIUrl":"https://doi.org/10.3847/2041-8213/ace422","url":null,"abstract":"Previous survey studies reported that coronal mass ejections (CMEs) can exhibit various structures in white-light coronagraphs, and ∼30% of them have the typical three-part feature in the high corona (e.g., 2–6 R ⊙), which has been taken as the prototypical structure of CMEs. It is widely accepted that CMEs result from eruption of magnetic flux ropes (MFRs), and the three-part structure can be understood easily by means of the MFR eruption. It is interesting and significant to answer why only ∼30% of CMEs have the three-part feature in previous studies. Here we conduct a synthesis of the CME structure in the field of view (FOV) of K-Coronagraph (1.05–3 R ⊙). In total, 369 CMEs are observed from 2013 September to 2022 November. After inspecting the CMEs one by one through joint observations of the Atmospheric Imaging Assembly, K-Coronagraph, and LASCO/C2, we find 71 events according to the criteria: (1) limb event; (2) normal CME, i.e., angular width ≥30°; (3) K-Coronagraph caught the early eruption stage. All (or more than 90% considering several ambiguous events) of the 71 CMEs exhibit the three-part feature in the FOV of K-Coronagraph, while only 30%–40% have the feature in the C2 FOV (2–6 R ⊙). For the first time, our studies show that 90%–100% and 30%–40% of normal CMEs possess the three-part structure in the low and high corona, respectively, which demonstrates that many CMEs can lose the three-part feature during their early evolutions, and strongly supports that most (if not all) CMEs have the MFR structures.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131095146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.3847/2041-8213/acdb60
S. Totorica, S. Zenitani, S. Matsukiyo, M. Machida, K. Sekiguchi, Ashis Bhattacharjee
Magnetic reconnection is an important source of energetic particles in systems ranging from astrophysics to the laboratory. The large separation of spatiotemporal scales involved makes it critical to determine the minimum physical model containing the necessary physics for modeling particle acceleration. By resolving the energy gain from ideal and nonideal magnetohydrodynamic electric fields self-consistently in kinetic particle-in-cell simulations of reconnection, we conclusively show the dominant role of the nonideal field for the early stage of energization known as injection. The importance of the nonideal field increases with magnetization, guide field, and in three dimensions, indicating its general importance for reconnection in natural astrophysical systems. We obtain the statistical properties of the injection process from the simulations, paving the way for the development of extended MHD models capable of accurately modeling particle acceleration in large-scale systems. The novel analysis method developed in this study can be applied broadly to give new insight into a wide range of processes in plasma physics.
{"title":"Exact Calculation of Nonideal Fields Demonstrates Their Dominance of Injection in Relativistic Reconnection","authors":"S. Totorica, S. Zenitani, S. Matsukiyo, M. Machida, K. Sekiguchi, Ashis Bhattacharjee","doi":"10.3847/2041-8213/acdb60","DOIUrl":"https://doi.org/10.3847/2041-8213/acdb60","url":null,"abstract":"Magnetic reconnection is an important source of energetic particles in systems ranging from astrophysics to the laboratory. The large separation of spatiotemporal scales involved makes it critical to determine the minimum physical model containing the necessary physics for modeling particle acceleration. By resolving the energy gain from ideal and nonideal magnetohydrodynamic electric fields self-consistently in kinetic particle-in-cell simulations of reconnection, we conclusively show the dominant role of the nonideal field for the early stage of energization known as injection. The importance of the nonideal field increases with magnetization, guide field, and in three dimensions, indicating its general importance for reconnection in natural astrophysical systems. We obtain the statistical properties of the injection process from the simulations, paving the way for the development of extended MHD models capable of accurately modeling particle acceleration in large-scale systems. The novel analysis method developed in this study can be applied broadly to give new insight into a wide range of processes in plasma physics.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115228160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.3847/2041-8213/ace18c
Dechao Song, J. Tian, Y. Li, M. Ding, Yang Su, Sijie Yu, Jie Hong, Ye Qiu, S. Rao, Xiaofeng Liu, Qiao-Chu Li, Xingyao Chen, Chuan Li, Cheng Fang
The heating mechanisms of solar white-light flares remain unclear. We present an X1.0 white-light flare on 2022 October 2 (SOL2022-10-02T20:25) observed by the Chinese Hα Solar Explorer that provides two-dimensional spectra in the visible light for the full solar disk with a seeing-free condition. The flare shows a prominent enhancement of ∼40% in the photospheric Fe i line at 6569.2 Å, and the nearby continuum also exhibits a maximum enhancement of ∼40%. For the continuum near the Fe i line at 6173 Å from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is enhanced up to ∼20%. At the white-light kernels, the Fe i line at 6569.2 Å has a symmetric Gaussian profile that is still in absorption and the Hα line at 6562.8 Å displays a very broad emission profile with a central reversal plus a red or blue asymmetry. The white-light kernels are cospatial with the microwave footpoint sources observed by the Expanded Owens Valley Solar Array and the time profile of the white-light emission matches that of the hard X-ray emission above 30 keV from the Gamma-ray Burst Monitor (GBM) on Fermi. These facts indicate that the white-light emission is qualitatively related to a nonthermal electron beam. We also perform a radiative hydrodynamic simulation with the electron-beam parameters constrained by the hard X-ray observations from Fermi/GBM. The result reveals that the white-light enhancement cannot be well explained by a pure electron-beam heating together with its induced radiative backwarming but may need additional heating sources such as Alfvén waves.
{"title":"Spectral Observations and Modeling of a Solar White-light Flare Observed by CHASE","authors":"Dechao Song, J. Tian, Y. Li, M. Ding, Yang Su, Sijie Yu, Jie Hong, Ye Qiu, S. Rao, Xiaofeng Liu, Qiao-Chu Li, Xingyao Chen, Chuan Li, Cheng Fang","doi":"10.3847/2041-8213/ace18c","DOIUrl":"https://doi.org/10.3847/2041-8213/ace18c","url":null,"abstract":"The heating mechanisms of solar white-light flares remain unclear. We present an X1.0 white-light flare on 2022 October 2 (SOL2022-10-02T20:25) observed by the Chinese Hα Solar Explorer that provides two-dimensional spectra in the visible light for the full solar disk with a seeing-free condition. The flare shows a prominent enhancement of ∼40% in the photospheric Fe i line at 6569.2 Å, and the nearby continuum also exhibits a maximum enhancement of ∼40%. For the continuum near the Fe i line at 6173 Å from the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is enhanced up to ∼20%. At the white-light kernels, the Fe i line at 6569.2 Å has a symmetric Gaussian profile that is still in absorption and the Hα line at 6562.8 Å displays a very broad emission profile with a central reversal plus a red or blue asymmetry. The white-light kernels are cospatial with the microwave footpoint sources observed by the Expanded Owens Valley Solar Array and the time profile of the white-light emission matches that of the hard X-ray emission above 30 keV from the Gamma-ray Burst Monitor (GBM) on Fermi. These facts indicate that the white-light emission is qualitatively related to a nonthermal electron beam. We also perform a radiative hydrodynamic simulation with the electron-beam parameters constrained by the hard X-ray observations from Fermi/GBM. The result reveals that the white-light enhancement cannot be well explained by a pure electron-beam heating together with its induced radiative backwarming but may need additional heating sources such as Alfvén waves.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132942041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.3847/2041-8213/acdf5b
Jun-Ting Liu, Xi Chen, Xiaodian Chen, Zhiwei Chen, Shijie Song, You-Xin Wang, Yan-Kun Zhang, Zhang Zhao, Bin Li, B. Xia, Zhi-qiang Shen
We present observations of the 6.7 GHz methanol and 4.8 GHz formaldehyde masers toward the high-mass young stellar object G24.33+0.14 (hereafter G24). Our observations were conducted from 2019 to 2021 using the Shanghai Tianma 65 m Radio Telescope and the Very Large Array in response to the luminosity outburst event traced by these two species masers in 2019. Our results indicate that the provenance of the maser flares is unlikely to be ascribed to the protostar of G24 itself. Through analyzing NEOWISE infrared monitoring data, we identified two light curves of G24 with long-term (3083 days, ∼8.5 yr) and short-term (424 days) periods. Intriguingly, 11 periodic variable sources located in the same bubble as G24 exhibiting periods comparable to the short-term period of G24 were also detected. The analysis of the spectral energy distributions of these periodic variables revealed a possible correlation between their temperature fluctuations and the surrounding radiation field that possibly emanates from the driving source of the bubble. This source could be an individual supergiant protostar of a few hundred solar masses with periodic pulsation potentially accounting for the observed short-term period in the G24 region.
{"title":"Luminosity Outburst of a High-mass Young Stellar Object Triggered by the Surrounding Radiation Field","authors":"Jun-Ting Liu, Xi Chen, Xiaodian Chen, Zhiwei Chen, Shijie Song, You-Xin Wang, Yan-Kun Zhang, Zhang Zhao, Bin Li, B. Xia, Zhi-qiang Shen","doi":"10.3847/2041-8213/acdf5b","DOIUrl":"https://doi.org/10.3847/2041-8213/acdf5b","url":null,"abstract":"We present observations of the 6.7 GHz methanol and 4.8 GHz formaldehyde masers toward the high-mass young stellar object G24.33+0.14 (hereafter G24). Our observations were conducted from 2019 to 2021 using the Shanghai Tianma 65 m Radio Telescope and the Very Large Array in response to the luminosity outburst event traced by these two species masers in 2019. Our results indicate that the provenance of the maser flares is unlikely to be ascribed to the protostar of G24 itself. Through analyzing NEOWISE infrared monitoring data, we identified two light curves of G24 with long-term (3083 days, ∼8.5 yr) and short-term (424 days) periods. Intriguingly, 11 periodic variable sources located in the same bubble as G24 exhibiting periods comparable to the short-term period of G24 were also detected. The analysis of the spectral energy distributions of these periodic variables revealed a possible correlation between their temperature fluctuations and the surrounding radiation field that possibly emanates from the driving source of the bubble. This source could be an individual supergiant protostar of a few hundred solar masses with periodic pulsation potentially accounting for the observed short-term period in the G24 region.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126980431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-01DOI: 10.3847/2041-8213/ace186
P. Weber, S. Pérez, A. Zurlo, J. Miley, A. Hales, L. Cieza, D. Principe, M. Cárcamo, A. Garufi, Á. Kóspál, M. Takami, J. Kastner, Zhaohuan Zhu, Jonathan P. Williams
The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due to the scarcity of observations of fragmented protoplanetary disks around young stars and the low occurrence rate of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered light with several spiral arms. This finding motivated a reanalysis of archival Atacama Large Millimeter/submillimeter Array 1.3 mm data acquired just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of gravitational instability occurring on planetary scales. This study discusses the significance of this finding for planet formation and its potential connection with the outbursting state of V960 Mon.
{"title":"Spirals and Clumps in V960 Mon: Signs of Planet Formation via Gravitational Instability around an FU Ori Star?","authors":"P. Weber, S. Pérez, A. Zurlo, J. Miley, A. Hales, L. Cieza, D. Principe, M. Cárcamo, A. Garufi, Á. Kóspál, M. Takami, J. Kastner, Zhaohuan Zhu, Jonathan P. Williams","doi":"10.3847/2041-8213/ace186","DOIUrl":"https://doi.org/10.3847/2041-8213/ace186","url":null,"abstract":"The formation of giant planets has traditionally been divided into two pathways: core accretion and gravitational instability. However, in recent years, gravitational instability has become less favored, primarily due to the scarcity of observations of fragmented protoplanetary disks around young stars and the low occurrence rate of massive planets on very wide orbits. In this study, we present a SPHERE/IRDIS polarized light observation of the young outbursting object V960 Mon. The image reveals a vast structure of intricately shaped scattered light with several spiral arms. This finding motivated a reanalysis of archival Atacama Large Millimeter/submillimeter Array 1.3 mm data acquired just two years after the onset of the outburst of V960 Mon. In these data, we discover several clumps of continuum emission aligned along a spiral arm that coincides with the scattered light structure. We interpret the localized emission as fragments formed from a spiral arm under gravitational collapse. Estimating the mass of solids within these clumps to be of several Earth masses, we suggest this observation to be the first evidence of gravitational instability occurring on planetary scales. This study discusses the significance of this finding for planet formation and its potential connection with the outbursting state of V960 Mon.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128489718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-30DOI: 10.3847/2041-8213/ace77d
Z. He 何
This Letter presents a study of the geometry and motion of the Galactic disk using open clusters in the Gaia era. The findings suggest that the inclination θ i of the Galactic disk increases gradually from the inner to the outer disk, with a shift in orientation at the Galactocentric radius of approximately 6 ± 1 kpc. Furthermore, this study brings forth the revelation that the mid-plane of the Milky Way may not possess a stationary or fixed position. A plausible explanation is that the inclined orbits of celestial bodies within our Galaxy exhibit a consistent pattern of elliptical shapes, deviating from perfect circularity; however, more observations are needed to confirm this. An analysis of the vertical motion along the Galactocentric radius reveals that the disk has warped with precession and that the line of node shifts at different radii, aligning with the results from the classical Cepheids. Although there is uncertainty for precession/peculiar motion in solar orbit, after considering the uncertainty, the study derives a median value of ϕ̇LON = 6.8 km s−1 kpc−1 in the Galaxy. This value for the derived precession in the outer disk is lower than those in the literature due to the systematic motion in solar orbit (θ i = 0.°6). The study also finds that the inclinational variation of the disk is significant and can cause systematic motion, with the variation rate θ̇i decreasing along the Galactic radius with a slope of −8.9 μas yr−1 kpc−1. Moreover, the derived θ̇i in solar orbit is 59.1 ± 11.2sample ± 7.7 VZ⊙ μas yr−1, which makes it observable for high-precision astrometry.
这封信提出了在盖亚时代使用疏散星团对银河盘的几何和运动的研究。结果表明，银盘的倾角θ i由内到外逐渐增大，在银心半径处方向变化约为6±1 kpc。此外，这项研究还揭示了银河系的中间面可能不具有静止或固定的位置。一个合理的解释是，我们银河系内天体的倾斜轨道呈现出一致的椭圆形状，偏离完美的圆形;然而，需要更多的观察来证实这一点。对沿星系中心半径垂直运动的分析显示，星盘已经随着进动而弯曲，并且星节线在不同的半径上移动，这与经典造父变星的结果一致。尽管太阳轨道的进动/特殊运动存在不确定性，但在考虑了不确定性之后，该研究得出银河系中φ (LON) = 6.8 km s−1 kpc−1的中值。由于太阳轨道上的系统运动(θ i = 0. 6)，推导出的外盘进动值比文献中的值要低。研究还发现，盘的倾角变化显著，可引起系统运动，其变化率θ i沿银河系半径递减，斜率为−8.9 μas yr−1 kpc−1。推导出的太阳轨道θ i为59.1±11.2sample±7.7 VZ⊙μas yr−1，可用于高精度天体测量。
{"title":"Geometry and Kinematics of a Dancing Milky Way: Unveiling the Precession and Inclination Variation across the Galactic Plane via Open Clusters","authors":"Z. He 何","doi":"10.3847/2041-8213/ace77d","DOIUrl":"https://doi.org/10.3847/2041-8213/ace77d","url":null,"abstract":"This Letter presents a study of the geometry and motion of the Galactic disk using open clusters in the Gaia era. The findings suggest that the inclination θ i of the Galactic disk increases gradually from the inner to the outer disk, with a shift in orientation at the Galactocentric radius of approximately 6 ± 1 kpc. Furthermore, this study brings forth the revelation that the mid-plane of the Milky Way may not possess a stationary or fixed position. A plausible explanation is that the inclined orbits of celestial bodies within our Galaxy exhibit a consistent pattern of elliptical shapes, deviating from perfect circularity; however, more observations are needed to confirm this. An analysis of the vertical motion along the Galactocentric radius reveals that the disk has warped with precession and that the line of node shifts at different radii, aligning with the results from the classical Cepheids. Although there is uncertainty for precession/peculiar motion in solar orbit, after considering the uncertainty, the study derives a median value of ϕ̇LON = 6.8 km s−1 kpc−1 in the Galaxy. This value for the derived precession in the outer disk is lower than those in the literature due to the systematic motion in solar orbit (θ i = 0.°6). The study also finds that the inclinational variation of the disk is significant and can cause systematic motion, with the variation rate θ̇i decreasing along the Galactic radius with a slope of −8.9 μas yr−1 kpc−1. Moreover, the derived θ̇i in solar orbit is 59.1 ± 11.2sample ± 7.7 VZ⊙ μas yr−1, which makes it observable for high-precision astrometry.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122862653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-29DOI: 10.3847/2041-8213/acd7e7
Y. Chi, C. Shen, Junyan Liu, Zhihui Zhong, M. Owens, C. Scott, L. Barnard, Bingkun Yu, D. Heyner, H. Auster, I. Richter, Yuming Wang, Tielong Zhang, Jingnan Guo, B. Sánchez–Cano, Z. Pan, Zhuxuan Zou, Mengjiao Xu, L. Cheng, Z. Su, Dongwei Mao, Zhiyong Zhang, Can Wang, Zhiyong Wu, Guoqiang Wang, S. Xiao, Kai Liu, X. Hao, Yiren Li, Manming Chen, M. Lockwood
We present two multipoint interplanetary coronal mass ejections (ICMEs) detected by the Tianwen-1 and Mars Atmosphere and Volatile Evolution spacecraft at Mars and the BepiColombo (0.56 au ∼0.67 au) upstream of Mars from 2021 December 5 to 31. This is the first time that BepiColombo is used as an upstream solar wind monitor ahead of Mars and that Tianwen-1 is used to investigate the magnetic field characteristics of ICMEs at Mars. The Heliospheric Upwind Extrapolation time model was used to connect the multiple in situ observations and the coronagraph observations from STEREO/SECCHI and SOHO/LASCO. The first fast coronal mass ejection event (∼761.2 km s−1), which erupted on December 4, impacted Mars centrally and grazed BepiColombo by its western flank. The ambient slow solar wind decelerated the west flank of the ICME, implying that the ICME event was significantly distorted by the solar wind structure. The second slow ICME event (∼390.7 km s−1) underwent an acceleration from its eruption to a distance within 0.69 au and then traveled with the constant velocity of the ambient solar wind. These findings highlight the importance of background solar wind in determining the interplanetary evolution and global morphology of ICMEs up to Mars distance. Observations from multiple locations are invaluable for space weather studies at Mars and merit more exploration in the future.
本文介绍了从2021年12月5日至31日在火星上游的BepiColombo (0.56 au ~ 0.67 au)和火星大气和挥发物演化探测器在火星和BepiColombo (0.56 au ~ 0.67 au)探测到的两个多点行星际日冕物质抛射(ICMEs)。这是BepiColombo卫星第一次被用作火星前的上游太阳风监测仪，也是天文一号卫星第一次被用来研究火星ICMEs的磁场特征。利用日球逆风外推时间模型将STEREO/SECCHI和SOHO/LASCO的日冕观测与多个原位观测相连接。12月4日爆发的第一次快速日冕物质抛射事件(~ 761.2 km s - 1)撞击了火星的中心，并从火星的西侧掠过了比皮可伦坡。周围缓慢的太阳风使ICME的西侧翼减速，表明ICME事件受到太阳风结构的显著扭曲。第二次缓慢的ICME事件(~ 390.7 km s−1)经历了从喷发到0.69 au距离内的加速，然后以周围太阳风的恒定速度行进。这些发现强调了背景太阳风在确定火星距离内ICMEs的行星际演化和全球形态方面的重要性。来自多个地点的观测对火星的空间天气研究是无价的，值得未来进行更多的探索。
{"title":"The Dynamic Evolution of Multipoint Interplanetary Coronal Mass Ejections Observed with BepiColombo, Tianwen-1, and MAVEN","authors":"Y. Chi, C. Shen, Junyan Liu, Zhihui Zhong, M. Owens, C. Scott, L. Barnard, Bingkun Yu, D. Heyner, H. Auster, I. Richter, Yuming Wang, Tielong Zhang, Jingnan Guo, B. Sánchez–Cano, Z. Pan, Zhuxuan Zou, Mengjiao Xu, L. Cheng, Z. Su, Dongwei Mao, Zhiyong Zhang, Can Wang, Zhiyong Wu, Guoqiang Wang, S. Xiao, Kai Liu, X. Hao, Yiren Li, Manming Chen, M. Lockwood","doi":"10.3847/2041-8213/acd7e7","DOIUrl":"https://doi.org/10.3847/2041-8213/acd7e7","url":null,"abstract":"We present two multipoint interplanetary coronal mass ejections (ICMEs) detected by the Tianwen-1 and Mars Atmosphere and Volatile Evolution spacecraft at Mars and the BepiColombo (0.56 au ∼0.67 au) upstream of Mars from 2021 December 5 to 31. This is the first time that BepiColombo is used as an upstream solar wind monitor ahead of Mars and that Tianwen-1 is used to investigate the magnetic field characteristics of ICMEs at Mars. The Heliospheric Upwind Extrapolation time model was used to connect the multiple in situ observations and the coronagraph observations from STEREO/SECCHI and SOHO/LASCO. The first fast coronal mass ejection event (∼761.2 km s−1), which erupted on December 4, impacted Mars centrally and grazed BepiColombo by its western flank. The ambient slow solar wind decelerated the west flank of the ICME, implying that the ICME event was significantly distorted by the solar wind structure. The second slow ICME event (∼390.7 km s−1) underwent an acceleration from its eruption to a distance within 0.69 au and then traveled with the constant velocity of the ambient solar wind. These findings highlight the importance of background solar wind in determining the interplanetary evolution and global morphology of ICMEs up to Mars distance. Observations from multiple locations are invaluable for space weather studies at Mars and merit more exploration in the future.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132786700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-29DOI: 10.3847/2041-8213/acdde0
H. Iijima, Takuma Matsumoto, H. Hotta, S. Imada
The physical connection between thermal convection in the solar interior and the solar wind remains unclear due to their significant scale separation. Using an extended version of the three-dimensional radiative magnetohydrodynamic code RAMENS, we perform the first comprehensive simulation of the solar wind formation, starting from the wave excitation and the small-scale dynamo below the photosphere. The simulation satisfies various observational constraints as a slow solar wind emanating from the coronal hole boundary. The magnetic energy is persistently released in the simulated corona, showing a hot upward flow at the interface between open and closed fields. To evaluate the energetic contributions from Alfvén wave and interchange reconnection, we develop a new method to quantify the cross-field energy transport in the simulated atmosphere. The measured energy transport from closed coronal loops to open field accounts for approximately half of the total. These findings suggest a significant role of the supergranular-scale interchange reconnection in solar wind formation.
{"title":"A Comprehensive Simulation of Solar Wind Formation from the Solar Interior: Significant Cross-field Energy Transport by Interchange Reconnection near the Sun","authors":"H. Iijima, Takuma Matsumoto, H. Hotta, S. Imada","doi":"10.3847/2041-8213/acdde0","DOIUrl":"https://doi.org/10.3847/2041-8213/acdde0","url":null,"abstract":"The physical connection between thermal convection in the solar interior and the solar wind remains unclear due to their significant scale separation. Using an extended version of the three-dimensional radiative magnetohydrodynamic code RAMENS, we perform the first comprehensive simulation of the solar wind formation, starting from the wave excitation and the small-scale dynamo below the photosphere. The simulation satisfies various observational constraints as a slow solar wind emanating from the coronal hole boundary. The magnetic energy is persistently released in the simulated corona, showing a hot upward flow at the interface between open and closed fields. To evaluate the energetic contributions from Alfvén wave and interchange reconnection, we develop a new method to quantify the cross-field energy transport in the simulated atmosphere. The measured energy transport from closed coronal loops to open field accounts for approximately half of the total. These findings suggest a significant role of the supergranular-scale interchange reconnection in solar wind formation.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131278571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-06-28DOI: 10.3847/2041-8213/acdac6
G. Agazie, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, B. Bécsy, L. Blecha, A. Brazier, P. Brook, S. Burke-Spolaor, R. Burnette, R. Case, M. Charisi, S. Chatterjee, K. Chatziioannou, B. Cheeseboro, Siyuan Chen, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, C. Cutler, M. DeCesar, D. DeGan, P. Demorest, Heling Deng, T. Dolch, B. Drachler, J. Ellis, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, N. Garver-Daniels, P. Gentile, K. A. Gersbach, J. Glaser, D. Good, K. Gultekin, J. Hazboun, S. Hourihane, K. Islo, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, T. C. Klein, N. Laal, M. Lam, W. Lamb, T. Lazio, N. Lewandowska, T. Littenberg, Tianyu Liu, A. Lommen, D. Lorimer, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, M. A. Mattson, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, P. Meyers, C. Mingarelli, A. Mitridate, P. Natarajan, C. Ng, D. Nice, S. Ocker, K. Olum, T. Pennucci, B. Perera, P. Petrov, N. Pol, H. Radovan
We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 1014, and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10−3 (≈3σ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10−5 to 1.9 × 10−4 (≈3.5σ–4σ). Assuming a fiducial f −2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is 2.4−0.6+0.7×10−15 (median + 90% credible interval) at a reference frequency of 1 yr−1. The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.
{"title":"The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background","authors":"G. Agazie, A. Anumarlapudi, A. Archibald, Z. Arzoumanian, P. Baker, B. Bécsy, L. Blecha, A. Brazier, P. Brook, S. Burke-Spolaor, R. Burnette, R. Case, M. Charisi, S. Chatterjee, K. Chatziioannou, B. Cheeseboro, Siyuan Chen, T. Cohen, J. Cordes, N. Cornish, F. Crawford, H. Cromartie, K. Crowter, C. Cutler, M. DeCesar, D. DeGan, P. Demorest, Heling Deng, T. Dolch, B. Drachler, J. Ellis, E. Ferrara, W. Fiore, E. Fonseca, G. Freedman, N. Garver-Daniels, P. Gentile, K. A. Gersbach, J. Glaser, D. Good, K. Gultekin, J. Hazboun, S. Hourihane, K. Islo, R. Jennings, A. Johnson, Megan L. Jones, A. Kaiser, D. Kaplan, L. Kelley, M. Kerr, J. Key, T. C. Klein, N. Laal, M. Lam, W. Lamb, T. Lazio, N. Lewandowska, T. Littenberg, Tianyu Liu, A. Lommen, D. Lorimer, Jing Luo, R. Lynch, Chung-Pei Ma, D. Madison, M. A. Mattson, A. McEwen, J. McKee, M. Mclaughlin, N. McMann, B. W. Meyers, P. Meyers, C. Mingarelli, A. Mitridate, P. Natarajan, C. Ng, D. Nice, S. Ocker, K. Olum, T. Pennucci, B. Perera, P. Petrov, N. Pol, H. Radovan","doi":"10.3847/2041-8213/acdac6","DOIUrl":"https://doi.org/10.3847/2041-8213/acdac6","url":null,"abstract":"We report multiple lines of evidence for a stochastic signal that is correlated among 67 pulsars from the 15 yr pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves. The correlations follow the Hellings–Downs pattern expected for a stochastic gravitational-wave background. The presence of such a gravitational-wave background with a power-law spectrum is favored over a model with only independent pulsar noises with a Bayes factor in excess of 1014, and this same model is favored over an uncorrelated common power-law spectrum model with Bayes factors of 200–1000, depending on spectral modeling choices. We have built a statistical background distribution for the latter Bayes factors using a method that removes interpulsar correlations from our data set, finding p = 10−3 (≈3σ) for the observed Bayes factors in the null no-correlation scenario. A frequentist test statistic built directly as a weighted sum of interpulsar correlations yields p = 5 × 10−5 to 1.9 × 10−4 (≈3.5σ–4σ). Assuming a fiducial f −2/3 characteristic strain spectrum, as appropriate for an ensemble of binary supermassive black hole inspirals, the strain amplitude is 2.4−0.6+0.7×10−15 (median + 90% credible interval) at a reference frequency of 1 yr−1. The inferred gravitational-wave background amplitude and spectrum are consistent with astrophysical expectations for a signal from a population of supermassive black hole binaries, although more exotic cosmological and astrophysical sources cannot be excluded. The observation of Hellings–Downs correlations points to the gravitational-wave origin of this signal.","PeriodicalId":179976,"journal":{"name":"The Astrophysical Journal Letters","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122909804","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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