Article
Astronomy & Astrophysics
James R. Beattie, Mark R. Krumholz, Raphael Skalidis, Christoph Federrath, Amit Seta, Roland M. Crocker, Philip Mocz, Neco Kriel
Summary: Energy equipartition is a powerful theoretical tool in understanding astrophysical plasmas. This study explores the role of the magnetic coupling term between turbulent and large-scale fields. It is found that in sub-Alfvenic turbulence with a large-scale field, there is energy equipartition between the coupling term and the turbulent kinetic energy. Numerical simulations further support this conclusion and provide insights into the relation between turbulent mean field and total Alfven Mach numbers.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
James R. Beattie, Philip Mocz, Christoph Federrath, Ralf S. Klessen
Summary: The logarithmic density contrast of hydrodynamical supersonic turbulence exhibits significant non-Gaussian features that increase with the turbulent Mach number. By studying simulations with different driving modes, it is found that the non-Gaussian nature of the density contrast is more complicated than previously thought. The non-Gaussian features are present in highly magnetized plasma for low Mach numbers, but disappear for high Mach numbers.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
James R. Beattie, Philip Mocz, Christoph Federrath, Ralf S. Klessen
Summary: This study develops an anisotropic model for density variance in molecular clouds, taking into account contributions from hydrodynamical and fast magnetosonic shocks. The model predicts an upper limit for density fluctuations in high Mach number conditions and shows good agreement with simulations. By considering sub-Alfvenic magnetic fields, the study provides insights into the bimodal overdensities observed in some molecular clouds and implications for star formation theory. Creating an anisotropic model for supersonic density fluctuations lays the groundwork for understanding star formation in highly anisotropic interstellar turbulence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
James R. Beattie, Christoph Federrath, Neco Kriel, Philip Mocz, Amit Seta
Summary: The turbulent small-scale dynamo is likely the cause of the observed magnetization of the interstellar medium. This process converts kinetic energy into magnetic energy and can amplify and maintain a weak initial magnetic field. Through simulations, it has been found that the final saturated state of the turbulent dynamo is determined by the turbulence and plasma properties, regardless of the initial structure or amplitude of the magnetic field. This has implications for understanding and studying magnetic field maintenance in turbulent plasmas.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Eric R. Moseley, R. Teyssier, B. T. Draine
Summary: This study investigates the stochastic acceleration mechanism of dust grains and demonstrates that they can be effectively accelerated to speeds beyond their shattering velocities. The implementation of novel magnetohydrodynamic particle-in-cell methods into the astrophysical fluid code RAMSES allows for the validation of the method under different physical conditions. The results provide insights into the protection of relatively pristine sub-micron pre-solar grains from significant wear.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Sajay Sunny Mathew, Christoph Federrath
Summary: The study demonstrates that various factors in star cluster formation, including protostellar outflows, affect the star formation rate, mass distribution, and initial mass function. The turbulence-based model and observational IMF agree well in the high-mass and low-mass regime, but do not predict any brown dwarfs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Justin Kin Jun Hew, Christoph Federrath
Summary: This study presents novel 3D magnetohydrodynamic simulations of a laser-driven shock propagating into a stratified multiphase medium, investigating the post-shock turbulent magnetic field amplification via the turbulent dynamo mechanism. The results indicate that the growth rate of the magnetic field is consistent with the theoretical predictions for compressive turbulence driving in subsonic, compressible turbulence.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Mingrui Liu, Yue Hu, A. Lazarian, Siyao Xu, Marian Soida
Summary: Magnetic fields are important in galaxy formation and evolution, but are challenging to measure. This study uses synchrotron polarization and the Velocity Gradient Technique (VGT) to measure the magnetic field orientations in the Seyfert galaxy NGC 3627. The results show that the magnetic field orientations measured by VGT are globally consistent with the polarization, suggesting that the magnetic fields associated with synchrotron emission also permeate star-forming regions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Sajay Sunny Mathew, Christoph Federrath, Amit Seta
Summary: Turbulence is crucial for star formation, but its role in the initial mass function (IMF) is not fully understood. Magnetohydrodynamical simulations reveal that compressive turbulence driving produces a higher fraction of low-mass stars compared to solenoidal driving. The simulations capture the important features of the observed IMF form.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Henry B. Lane, Michael Y. Grudic, David Guszejnov, Stella S. R. Offner, Claude-Andre Faucher-Giguere, Anna L. Rosen
Summary: Simulating isolated giant molecular clouds is important for studying star formation dynamics, but the initial conditions of turbulence are uncertain. Researchers have developed a new simulation setup that combines advantages of previous methods and found that external driving can significantly suppress star formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Yue Hu, Christoph Federrath, Siyao Xu, Sajay Sunny Mathew
Summary: The interaction between turbulence, magnetic fields, self-gravity, and stellar feedback is crucial for understanding star formation. This study focuses on the effects of self-gravity and outflow feedback on the turbulent velocity within molecular clouds. The results show that outflow feedback can change the scaling of velocity fluctuations and amplify turbulence. Self-gravity and protostellar outflows increase velocity fluctuations and enhance fragmentation. The study also finds that self-gravity has a more significant effect on smaller dense clumps, while outflow feedback drives a higher fraction of solenoidal modes relative to compressive modes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
R. Skalidis, J. Sternberg, J. R. Beattie, V. Pavlidou, K. Tassis
Summary: The method of estimating magnetic field strength in interstellar clouds by measuring dust polarization has been tested through theoretical arguments and numerical simulations. The results show that the ST method reflects better the physical reality in clouds with compressible and magnetized turbulence, providing a much better estimate of the magnetic field strength compared to the DCF method.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Turlough P. Downes, Patrick Hartigan, Andrea Isella
Summary: We conducted various analyses of the turbulent dynamics of the boundary of a photodissociation region (PDR) in the Carina Nebula using high-resolution ALMA observations. Our findings suggest that the turbulence in this molecular cloud is driven by large-scale processes and dominated by shocks rather than local energy transport. The importance of length-scales in the range of 0.02-0.03 pc in the dynamics of the cloud is supported by the analysis of the dominant emission structure length-scale.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
A. Pandhi, R. K. Friesen, L. Fissel, J. E. Pineda, P. Caselli, M. C-Y Chen, J. Di Francesco, A. Ginsburg, H. Kirk, P. C. Myers, S. S. R. Offner, A. Punanova, F. Quan, E. Redaelli, E. Rosolowsky, S. Scibelli, Y. M. Seo, Y. Shirley
Summary: A study of 399 dense cores reveals that most cores have no preferred orientation between the core elongation axis, velocity gradient direction, and the ambient magnetic field orientation, supporting a triaxial and weakly magnetized origin. However, a strong evidence for a preferred anti-alignment between the core elongation axis and magnetic field is found in protostellar cores, suggesting a change in orientation from starless and prestellar populations that may result from gravitational contraction in a magnetically-regulated (but not dominant) environment. Marginal evidence for anti-alignment between the core velocity gradient and magnetic field orientation is also found in the L1228 and L1251 regions of Cepheus, suggesting a preferred orientation with respect to magnetic fields may be more prevalent in regions with locally ordered fields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yue Hu, A. Lazarian
Summary: This study aims to map the Galactic magnetic field (GMF) in 3D by utilizing the MM2 technique, the velocity gradient technique (VGT), the column density variance approach, and the Galactic Arecibo L-band Feed Array HI survey. The results reveal the sub-Alfvenic and subsonic nature of the H i gas, with mean M-A ranging from 0.6 to 0.9 and mean M-s ranging from 0.2 to 1.5. The mean magnetic field strength varies from 0.5 to 2.5 μG, showing a decreasing trend towards the Galaxy's outskirt. This work provides a new avenue for mapping the GMF in 3D.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
P. A. Gonzalez-Morales, E. Khomenko, T. P. Downes, A. de Vicente
ASTRONOMY & ASTROPHYSICS
(2018)
Article
Astronomy & Astrophysics
Britton D. Smith, John A. Regan, Turlough P. Downes, Michael L. Norman, Brian W. O'Shea, John H. Wise
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2018)
Article
Physics, Fluids & Plasmas
D. Schworer, N. R. Walkden, H. Leggate, B. D. Dudson, F. Militello, T. Downes, M. M. Turner
PLASMA PHYSICS AND CONTROLLED FUSION
(2019)
Article
Multidisciplinary Sciences
John H. Wise, John A. Regan, Brian W. O'Shea, Michael L. Norman, Turlough P. Downes, Hao Xu
Article
Astronomy & Astrophysics
John A. Regan, Turlough P. Downes, Marta Volonteri, Ricarda Beckmann, Alessandro Lupi, Maxime Trebitsch, Yohan Dubois
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2019)
Article
Computer Science, Interdisciplinary Applications
Stephen O'Sullivan
JOURNAL OF COMPUTATIONAL PHYSICS
(2019)
Article
Astronomy & Astrophysics
D. Rodgers-Lee, A. M. Taylor, T. P. Downes, T. P. Ray
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Correction
Astronomy & Astrophysics
D. Rodgers-Lee, A. M. Taylor, T. P. Ray, T. P. Downes
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
D. Rodgers-Lee, A. A. Vidotto, A. M. Taylor, P. B. Rimmer, T. P. Downes
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2020)
Article
Astronomy & Astrophysics
D. Rodgers-Lee, A. M. Taylor, A. A. Vidotto, T. P. Downes
Summary: Stellar cosmic rays, particularly those accelerated by impulsive flare events, play a significant role in the habitable zone of exoplanets, with their impact increasing with stellar rotation rate. The influence of stellar cosmic rays may dominate over Galactic cosmic rays during flare events, even at a young stellar age of 0.6 Gyr. Additionally, the properties of the inner solar wind are crucial for understanding the behavior of high-energy particles around Sun-like stars.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Tyrone E. Woods, Chris J. Willott, John A. Regan, John H. Wise, Turlough P. Downes, Michael L. Norman, Brian W. O'Shea
Summary: The article discusses the importance of identifying stars formed in pristine environments and how high-resolution cosmological simulations can be used to detect these stars. The study found that rapidly accreting stars in primordial halos exhibit prominent spectral features that can be detected by future instruments.
ASTROPHYSICAL JOURNAL LETTERS
(2021)
Article
Astronomy & Astrophysics
Patrick Hartigan, Maxwell Hummel, Andrea Isella, Turlough Downes
Summary: In this study, the authors present observations of continuum and line emission from various molecules in the Carina star-forming complex. The data reveal how a molecular cloud responds to radiation and shed light on the star formation process in regions with massive young stars.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Turlough P. Downes, Patrick Hartigan, Andrea Isella
Summary: We conducted various analyses of the turbulent dynamics of the boundary of a photodissociation region (PDR) in the Carina Nebula using high-resolution ALMA observations. Our findings suggest that the turbulence in this molecular cloud is driven by large-scale processes and dominated by shocks rather than local energy transport. The importance of length-scales in the range of 0.02-0.03 pc in the dynamics of the cloud is supported by the analysis of the dominant emission structure length-scale.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Patrick Hartigan, Turlough Downes, Andrea Isella
ASTROPHYSICAL JOURNAL LETTERS
(2020)
Article
Astronomy & Astrophysics
Leonardo Krapp, Oliver Gressel, Pablo Benitez-Llambay, Turlough P. Downes, Gopakumar Mohandas, Martin E. Pessah
ASTROPHYSICAL JOURNAL
(2018)