Article
Astronomy & Astrophysics
Zhe-Yu Daniel Lin, Li Zhi-Yun, Yang Haifeng, Olga Munoz, Leslie Looney, Ian Stephens, Charles L. H. Hull, Manuel Fernandez-Lopez, Rachel Harrison
Summary: The size of dust grains in circumstellar discs is crucial but challenging to observe. Previous observations attribute the per cent-level polarization seen in (sub)millimetre continuum observations to scattering by 100 μm-sized spherical grains. However, this size is in conflict with the larger mm/cm-sized grains indicated by the opacity index beta. We investigate the polarization produced by large irregular grains with x greater than unity and find that they can still produce the observed level of polarization. Our results suggest that millimetre-sized grains may exist in discs, alleviating the tension between scattering and other inferred grain sizes. Additionally, the forward scattering by large irregular grains can create asymmetries in inclined discs, indicating their presence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Zhe-Yu Daniel Lin, Zhi-Yun Li, Haifeng Yang, Ian Stephens, Leslie Looney, Rachel Harrison, Manuel Fernandez-Lopez
Summary: Telescopes are now capable of studying the polarization spectrum of circumstellar discs by resolving dust polarization at multiple wavelengths. Most discs show evidence of dust scattering through unidirectional polarization at shorter wavelengths, while some discs exhibit an elliptical pattern at longer wavelengths due to aligned grains. The polarization pattern of HL Tau at 1.3 mm reveals a transition between these two patterns, making it the first example to demonstrate such a transition. By using the T-matrix method and a plane-parallel slab model, researchers were able to model elongated dust grains and properly account for scattering of non-spherical aligned grains. The study found that a change in optical depth can explain the polarization transition of HL Tau, where thermal polarization dominates at low optical depths and scattering polarization dominates at high optical depths. A simple technique was developed to separate the thermal polarization and scattering-induced polarization by analyzing the azimuthal variation of the polarization fraction. The researchers also identified other sources similar to HL Tau that could be explained by azimuthally aligned scattering prolate grains when considering optical depth effects. Additionally, the study explores how spirally aligned grains with scattering can appear in polarization images.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Gavin A. L. Coleman, Thomas J. Haworth
Summary: This study explores the evolution and dispersal of protoplanetary discs under the influence of internal and external photoevaporation and varying degrees of viscous transport. It identifies five distinct dispersal pathways and shows that the relative impact of internal and external winds, as well as the clearing pathway, vary with different stellar/disc/radiation properties. The study highlights the importance of considering both internal and external winds in understanding protoplanetary disc evolution.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Andrew D. Sellek, Cathie J. Clarke, Richard A. Booth
Summary: Thermal disc winds are important for the evolution and dispersal of protoplanetary discs. By generalizing previous models to include launch from an elevated base and non-isothermal conditions, and validating them with hydrodynamic simulations, this study found that wind launch depends on the Mach number and spatial domain filling. Elevation of the wind base has the strongest impact on launch velocity and flow morphology, while temperature gradients have minor effects.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Dafa Li, Yao Liu, Hongchi Wang, Yao Wang, Yuehui Ma
Summary: The grain size in the DS Tau protoplanetary disc decreases with radius, in line with theories of dust evolution. At the interface region between the gap and the ring, the grain size profile shows a discontinuity, with its amplitude dependent on the dust model adopted in the radiative transfer analysis.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Juanita Antilen, Simon Casassus, Lucas A. Cieza, Camilo Gonzalez-Ruilova
Summary: The (CO)-C-12 rotational lines in protoplanetary discs were studied using ALMA long baseline observations. Constraints on the gas distribution and planet-disc interactions were obtained for 10 protoplanetary discs. The results showed evidence of a tilted inner disc, gas inside inner dust cavities or gaps, and a possible outflow in one of the discs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Lin Qiao, Gavin A. L. Coleman, Thomas J. Haworth
Summary: We demonstrate that planet formation via pebble accretion is sensitive to external photoevaporation of the outer disc. Pebble accretion relies on the supply of pebble flux from the outer disc, but if external photoevaporation truncates the disc too fast, it can limit the availability of pebble mass for planet growth. However, cloud shielding can protect the disc and preserve the pebble reservoir, resulting in significant differences in planetary properties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Thomas J. Haworth, Jinyoung S. Kim, Lin Qiao, Andrew J. Winter, Jonathan P. Williams, Cathie J. Clarke, James E. Owen, Stefano Facchini, Megan Ansdell, Mikhel Kama, Giulia Ballabio
Summary: We searched for C I 1-0 emission towards eight proplyds in NGC 1977 using the APEX telescope, but no detections were made despite reaching sensitivities deeper than previous observations. Comparison with external photo-evaporation simulations suggests that the non-detections are consistent with very low mass proplyd discs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Andrew D. Sellek, Cathie J. Clarke, Barbara Ercolano
Summary: Photoevaporative winds are a promising mechanism for dispersing protoplanetary discs, but theoretical models have been unable to agree on the relative roles that X-rays, extreme ultraviolet or far-ultraviolet play in driving the winds. Our study demonstrates that X-rays in the softer regions of the spectrum are more effective in driving the winds, while X-rays with energies similar to 1000 eV interact too weakly with the gas to provide sufficient heating. These findings suggest that the choice of irradiating spectrum should be considered when interpreting the results of photoevaporative wind models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Thomas J. Haworth
Summary: The study focuses on the effect of external massive sources on the temperature and dust mass estimates of protoplanetary discs, showing that disc masses can be overestimated, significantly altering dust mass estimates. Close proximity to massive stars can influence disc properties and lead to the disappearance of the CO snow line within a certain distance.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Chiara E. Scardoni, Richard A. Booth, Cathie J. Clarke
Summary: This paper investigates whether overdensity formation via streaming instability is consistent with recent observations in the Lupus star-forming region using simulations and comparisons with data. The study finds that clump formation leads to a decrease in the optically thick fraction ff and that the spectral index alpha may increase or decrease after the action of streaming instability. This behavior is observed to drive simulations towards the region where the data are located, especially when the instability is operative over a region of the disc that contributes significantly to the total mm flux.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
T. Becker, T. Steinpilz, J. Teiser, G. Wurm
Summary: In recent years, collisional charging has been proposed as a mechanism to promote pebble growth in the early stages of planet formation. However, previous experiments on collisional charging have only been conducted under limited pressure conditions. This study presents the first pressure-dependent charge measurements of same material collisions, showing that strong charging can occur even at very low pressures. The authors suggest that the breakdown voltage between two electrodes determines the maximum charge on colliding grains in protoplanetary discs, indicating that collisional charging can occur throughout the relevant regions for planet formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Dylan C. Jones, Ka Ho Lam, Zhi-Yun Li, Yisheng Tu
Summary: With the advent of ALMA, it is now possible to observationally constrain how discs form around deeply embedded protostars. The recent observations have been interpreted as evidence for the so-called 'centrifugal barrier,' where the protostellar envelope infall is gradually decelerated to a stop by the centrifugal force in a region of super-Keplerian rotation. However, the simulations conducted in this study suggest that the classic picture of centrifugal barrier is not supported, as the infalling envelope material is not solely decelerated by the centrifugal force but rather by outward angular momentum transport in the disc.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Martijn J. C. Wilhelm, Simon Portegies Zwart
Summary: Recent studies have revealed that 'Peter Pan discs' phenomenon can only occur around M dwarf stars, not around stars of higher mass. The lifetime of primordial discs depends on the host star's mass, with stars less than 0.6 solar masses being able to retain the discs for about 50 Myr.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Haochang Jiang, Chris W. Ormel
Summary: ALMA observations have shown that dust rings in protoplanetary discs are important for planet formation, where planetesimals can grow efficiently via pebble accretion. Type-I planet migration is crucial for the evolution of rings and planets.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Shanghuo Li, Patricio Sanhueza, Chang Won Lee, Qizhou Zhang, Henrik Beuther, Aina Palau, Hong-Li Liu, Howard A. Smith, Hauyu Baobab Liu, Izaskun Jimenez-Serra, Kee-Tae Kim, Siyi Feng, Tie Liu, Junzhi Wang, Di Li, Keping Qiu, Xing Lu, Josep Miquel Girart, Ke Wang, Fei Li, Juan Li, Yue Cao, Shinyoung Kim, Shaye Strom
Summary: This study presents the observation results of narrow filaments in the NGC 6334S infrared dark cloud using ALMA. The filaments are found to be narrower and have lower turbulence compared to previously proposed filaments. Embedded cores show smaller widths and lower velocity dispersions compared to their corresponding filaments. The physical properties of the filaments are analogous to those found in low- to high-mass star-forming regions.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Paulo C. Cortes, Patricio Sanhueza, Martin Houde, Sergio Martin, Charles L. H. Hull, Josep M. Girart, Qizhou Zhang, Manuel Fernandez-Lopez, Luis A. Zapata, Ian W. Stephens, Hua-bai Li, Benjamin Wu, Fernando Olguin, Xing Lu, Andres E. Guzman, Fumitaka Nakamura
Summary: In this study, polarized emission from dust, CS(J = 5 -> 4), and (CS)-S-33(J = 5 -> 4) towards NGC 6334I(N) in a high-mass star-forming region was detected by ALMA, revealing an hourglass magnetic field morphology. The study also found that the CS emission is optically thick while the C(33)5 emission is optically thin, suggesting the presence of anisotropies in the radiation field. The magnetic field strength estimates obtained from different emissions enable a tomographic view of the magnetic field within a single ALMA observation.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Rosario Lopez, Robert Estalella, Maria T. Beltran, Fabrizio Massi, Jose A. Acosta-Pulido, Josep M. Girart
Summary: This study confirms the collision scenario of two bipolar CO outflows in IC 1396N by analyzing the proper motions of H-2 knots. The velocity pattern of the post-collision knots shows a deviation from that of the pre-collision knots, indicating the interaction between the two outflows. This supports the interpretation of the IC 1396N outflows as a true collision between two protostellar jets.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
F. Massi, R. Lopez, M. T. Beltran, R. Estalella, J. M. Girart
Summary: This study characterizes the kinematics and physical conditions of H-2 emission features in the IC 1396N region. The results reveal a chain-like morphology with jet-like features and trace different H-2 outflows. The knots exhibit complex kinematic structures.
ASTRONOMY & ASTROPHYSICS
(2022)
Correction
Astronomy & Astrophysics
Rachel E. Harrison, Leslie W. Looney, Ian W. Stephens, Zhi-Yun Li, Richard Teague, Richard M. Crutcher, Haifeng Yang, Erin Cox, Manuel Fernandez-Lopez, Hiroko Shinnaga
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Zhe-Yu Daniel Lin, Zhi-Yun Li, Haifeng Yang, Ian Stephens, Leslie Looney, Rachel Harrison, Manuel Fernandez-Lopez
Summary: Telescopes are now capable of studying the polarization spectrum of circumstellar discs by resolving dust polarization at multiple wavelengths. Most discs show evidence of dust scattering through unidirectional polarization at shorter wavelengths, while some discs exhibit an elliptical pattern at longer wavelengths due to aligned grains. The polarization pattern of HL Tau at 1.3 mm reveals a transition between these two patterns, making it the first example to demonstrate such a transition. By using the T-matrix method and a plane-parallel slab model, researchers were able to model elongated dust grains and properly account for scattering of non-spherical aligned grains. The study found that a change in optical depth can explain the polarization transition of HL Tau, where thermal polarization dominates at low optical depths and scattering polarization dominates at high optical depths. A simple technique was developed to separate the thermal polarization and scattering-induced polarization by analyzing the azimuthal variation of the polarization fraction. The researchers also identified other sources similar to HL Tau that could be explained by azimuthally aligned scattering prolate grains when considering optical depth effects. Additionally, the study explores how spirally aligned grains with scattering can appear in polarization images.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Haifeng Yang, Zhi-Yun Li
Summary: This study focuses on the polarization of light scattered off magnetically aligned grains in protoplanetary disks. The results show that the polarization direction can deviate from the canonical azimuthal direction, particularly in highly inclined disks with toroidally dominated magnetic fields. The presence of (magnetically) aligned nonspherical grains can be inferred through observational features such as polarization reversal and a significant level of U (phi)/I. These findings provide important insights into the properties and evolution of protoplanetary disks.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Hanpu Liu, Gregory J. Herczeg, Doug Johnstone, Carlos Contreras-Pena, Jeong-Eun Lee, Haifeng Yang, Xingyu Zhou, Sung-Yong Yoon, Ho-Gyu Lee, Masanobu Kunitomo, Jessy Jose
Summary: FU Ori-type objects are studied by constructing models and calculating emission components from various sources. The models are validated by fitting to multiwavelength photometry of confirmed objects. The results provide insights into the characteristics of FUors.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Zhe-Yu Daniel Lin, Li Zhi-Yun, Yang Haifeng, Olga Munoz, Leslie Looney, Ian Stephens, Charles L. H. Hull, Manuel Fernandez-Lopez, Rachel Harrison
Summary: The size of dust grains in circumstellar discs is crucial but challenging to observe. Previous observations attribute the per cent-level polarization seen in (sub)millimetre continuum observations to scattering by 100 μm-sized spherical grains. However, this size is in conflict with the larger mm/cm-sized grains indicated by the opacity index beta. We investigate the polarization produced by large irregular grains with x greater than unity and find that they can still produce the observed level of polarization. Our results suggest that millimetre-sized grains may exist in discs, alleviating the tension between scattering and other inferred grain sizes. Additionally, the forward scattering by large irregular grains can create asymmetries in inclined discs, indicating their presence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Junhao Liu, Qizhou Zhang, Patrick M. Koch, Hauyu Baobab Liu, Zhi-Yun Li, Shanghuo Li, Josep Miquel Girart, Huei-Ru Vivien Chen, Tao-Chung Ching, Paul T. P. Ho, Shih-Ping Lai, Keping Qiu, Ramprasad Rao, Ya-wen Tang
Summary: In this study, we use ALMA observations to analyze the relative orientations between magnetic fields, column density gradients, local gravity, and velocity gradients in NGC 6334. Our results show that the alignment between the magnetic field and column density changes with the density of the region, indicating the influence of star formation activities. Additionally, we find that the magnetic field plays a significant role in the star formation process at small scales as well.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Bo Huang, Ke Wang, Josep M. Girart, Wenyu Jiao, Qianru He, Enwei Liang
Summary: To study the initial conditions of massive star formation, a sample of 463 high-mass starless clumps (HMSCs) was built, and (CO)-C-13(2-1) line data from the SEDIGISM survey was used to investigate their global dynamical state. The study found that most HMSCs are highly turbulent and a significant number of them are gravitationally bound. Magnetic field strength was found to be correlated with density and a certain strength was required to support these bound clumps against collapse.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Junhao Liu, Qizhou Zhang, Hauyu Baobab Liu, Keping Qiu, Shanghuo Li, Zhi-Yun Li, Paul T. P. Ho, Josep Miquel Girart, Tao-Chung Ching, Huei-Ru Vivien Chen, Shih-Ping Lai, Ramprasad Rao, Ya-wen Tang
Summary: We used molecular line data from different telescopes to study the velocity statistics in the massive star formation region NGC 6334 at various scales. The nonthermal motions revealed by the velocity dispersion function (VDF) remained supersonic across different scales. The nonthermal motions revealed by different instruments did not follow the same continuous power law, indicating the influence of massive star formation activities. The scaling relation of velocity fields in NGC 6334 deviated from a continuous and universal turbulence cascade due to the presence of massive star formation.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
M. Fernandez-Lopez, J. M. Girart, J. A. Lopez-Vazquez, R. Estalella, G. Busquet, S. Curiel, N. Anez-Lopez
Summary: We present new observations of the GGD 27-MM1 high-mass protostellar system, revealing the compositions of the dust disk, molecular disk, and envelope. We also identify possible accretion streamers and successfully reproduce their trajectories and velocities using a theoretical model. Additionally, the analysis of the rotation pattern in the molecular disk suggests the existence of an inner zone devoid of molecular content.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
M. Fernandez-Lopez, P. Sanhueza, L. A. Zapata, I. Stephens, C. Hull, Q. Zhang, J. M. Girart, P. M. Koch, P. Cortes, A. Silva, K. Tatematsu, F. Nakamura, A. E. Guzman, Q. Nguyen Luong, E. Guzman Ccolque, Y. -W. Tang, H. -R. V. Chen
Summary: The study conducted polarized continuum emission observations towards the high-mass star formation region G5.89-0.39 with the Atacama Large Millimeter/submillimeter Array, revealing a prominent north-south filamentary structure and an ultracompact H ii region that divides the filament. The millimeter emission shows a dusty belt surrounding an inner part of ionized gas, with a lattice of convex arches possibly produced by a dispersal event involving the O5 Feldt's star.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Paulo C. Cortes, Valentin J. M. Le Gouellec, Charles L. H. Hull, Josep M. Girart, Fabien Louvet, Edward B. Fomalont, Seiji Kameno, George A. Moellenbrock, Hiroshi Nagai, Kouichiro Nakanishi, Eric Villard
Summary: In this study, the first linear-polarization mosaicked observations performed by ALMA on the Orion-KL nebula were presented. The magnetic field morphology in the nebula was derived, showing that the magnetic field at the center has been overwhelmed by the explosive CO outflow, with a shock propagating from the center.
ASTROPHYSICAL JOURNAL
(2021)