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The radiative torque (RAT) alignment of interstellar grains with ordinary paramagnetic susceptibilities has been supported by earlier studies. The alignment of such grains depends on the so-called RAT parameter $q^{\max}$ that is determined…

Astrophysics of Galaxies · Physics 2016-11-15 Thiem Hoang , A. Lazarian

Earlier studies of grain alignment dealt mostly with interstellar grains that have strong internal relaxation of energy which aligns grain axis of maximum moment of inertia with respect to grain's angular momentum. In this paper, we study…

Astrophysics · Physics 2010-01-15 Thiem Hoang , Alex Lazarian

Alignment of dust grains in astrophysical environments results in the polarization of starlight as well as the polarization of radiation emitted by dust. We demonstrate the advances in grain alignment theory allow the use of linear and…

Astrophysics of Galaxies · Physics 2019-10-02 A Lazarian , Thiem Hoang

Dust grains drift through the interstellar medium (ISM) and are aligned with the magnetic field. Here we study the effect of grain alignment and grain motion on grain growth in molecular clouds (MCs). We first discuss the characteristic…

Astrophysics of Galaxies · Physics 2022-04-06 Thiem Hoang

We consider grains with superparamagnetic inclusions and report two new condensed matter effects that can enhance the internal relaxation of the energy of a wobbling grain, namely, superparamagnetic Barnett relaxation, as well as, an…

Astrophysics · Physics 2009-11-13 A. Lazarian , T. Hoang

Polarization arising from aligned dust grains presents a unique opportunity to study magnetic fields in the diffuse interstellar medium and molecular clouds. Polarization from circumstellar regions, accretion disks and comet atmospheres can…

Astrophysics of Galaxies · Physics 2016-06-21 A. Lazarian , B-G Andersson , Thiem Hoang

Motivated by a recent study by Lazarian and Draine, which showed that a high degree of grain alignment of the paramagnetic dust is achievable if the rates of internal relaxation are controlled by the Barnett relaxation process, we undertake…

Astrophysics · Physics 2009-10-31 A. Lazarian , M. Efroimsky

We generalize the magnetically enhanced radiative torque (MRAT) alignment theory for general astrophysical environments described by a dimensionless parameter $U/(n_{1}T_{2})$ with $U$ local radiation strength, $n_{1}=n_{\rm H}/(10{\rm…

Astrophysics of Galaxies · Physics 2025-09-23 Thiem Hoang

We reveal a deep connection between alignment of dust grains by RAdiative torques (RATs) and MEchanical Torques (METs) and rotational disruption of grains introduced by Hoang et al. (2019). The disruption of grains happens if they have…

Astrophysics of Galaxies · Physics 2021-02-17 A. Lazarian , Thiem Hoang

Paramagnetic alignment of thermally rotating oblate dust grains is studied analytically for finite ratios of grain to gas temperatures. For such ratios, the alignment of angular momentum J in respect to the grain axis of maximal inertia is…

Astrophysics · Physics 2015-06-24 A. Lazarian

Magnetic fields ($\textbf{B}$) are an important factor that controls the star formation process. The leading method to observe $\textbf{B}$ is using polarized thermal emission from dust grains aligned with $\textbf{B}$. However, in dense…

Astrophysics of Galaxies · Physics 2023-06-16 Nguyen Chau Giang , Thiem Hoang , Jeong-Gyu Kim , Le Ngoc Tram

The polarisation of light induced by aligned interstellar dust serves as a significant tool in investigating cosmic magnetic fields, dust properties, and poses a challenge in characterising the polarisation of the cosmic microwave…

Polarimetry is one of the most informative techniques of studying magnetic fields in molecular clouds. How reliable the interpretation of the polarization maps in terms of magnetic fields is the issue that the grain alignment theory…

Astrophysics · Physics 2016-08-30 A. Lazarian , J. Cho

Radiative Torques (RATs) or Mechanical Torques (METs) acting on irregular grains can induce the alignment of dust grains in respect to the alignment axis (AA), which can be either the direction of the magnetic field, or the direction of the…

Astrophysics of Galaxies · Physics 2020-10-21 A. Lazarian

Grain alignment by radiative torques (RATs) has been extensively studied for various environment conditions, including interstellar medium, dense molecular clouds, and accretion disks, thanks to significant progress in observational,…

Astrophysics of Galaxies · Physics 2015-06-22 Thiem Hoang , A. Lazarian

Alignment of dust by radiative torques (RATs) has proven to be the most promising mechanism to explain alignment in various astrophysical environments, from comet atmospheres to accretion disks, molecular clouds, and diffuse interstellar…

Astrophysics of Galaxies · Physics 2009-01-21 A. Lazarian , Thiem Hoang

Grain alignment theory suggests that grains should be aligned in circumstellar regions and the observational data available supports this conclusion. We discuss the alignment of grains via (1) magnetic relaxation, (2) mechanical processes,…

Astrophysics · Physics 2007-05-23 Lazarian A

Thermal dust continuum polarimetry is a powerful indirect probe of magnetic field geometry in dense molecular clouds while at the same time providing information on the alignment of dust grains with the magnetic field. The leading theory of…

We study the alignment of irregular dust grains by mechanical torques due to the drift of grains through the ambient gas. We first calculate mechanical torques (MATs) resulting from specular reflection of gas atoms for seven irregular…

Astrophysics of Galaxies · Physics 2018-01-31 Thiem Hoang , Jungyeon Cho , A. Lazarian

We study the efficiency of grain alignment by radiative torques (RATs) for an ensemble of irregular grains. The grains are modeled as ensembles of oblate and prolate spheroids, deformed as Gaussian random ellipsoids, and their scattering…

Astrophysics of Galaxies · Physics 2021-06-02 Joonas Herranen , A. Lazarian , Thiem Hoang
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