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The interstellar turbulence is magnetized and thus anisotropic. The anisotropy of turbulent magnetic fields and velocities is imprinted in the related observables, rotation measures (RMs), and velocity centroids (VCs). This anisotropy…

Astrophysics of Galaxies · Physics 2021-04-07 Siyao Xu , Yue Hu

The alignment of striated intensity structures in thin neutral hydrogen (HI) spectroscopic channels with Galactic magnetic fields has been observed. However, the origin and nature of these striations are still debatable. Some studies…

Astrophysics of Galaxies · Physics 2023-07-05 Yue Hu , A. Lazarian , D. Alina , D. Pogosyan , Ka Wai Ho

The detection of primordial B-mode polarization is still challenging due to the relatively low amplitude compared to the galactic foregrounds. To remove the contribution from the foreground, a comprehensive picture of the galactic magnetic…

Astrophysics of Galaxies · Physics 2020-07-07 Yue Hu , A. Lazarian

We apply Velocity Channel Gradients (VChGs) and Reduced Velocity Centroids Gradients (RVCGs) to H I data (the LAB survey), obtaining the plane-of-sky component (POS) of the magnetic field as a function of the relative velocity. Assuming a…

Astrophysics of Galaxies · Physics 2019-06-13 Diego F. Gonzalez-Casanova , A. Lazarian

This paper studies how to employ synchrotron emission gradient techniques to reveal the properties of the magnetic field within the interstellar media. Based on data cubes of three-dimensional numerical simulations of magnetohydrodynamic…

High Energy Astrophysical Phenomena · Physics 2020-01-08 Jian-Fu Zhang , Qian Liu , Alex Lazarian

Dust polarization orientations in molecular clouds often tend to be close to tangential to the Stokes $I$ dust continuum emission contours. The magnetic field and the emission gradient orientations, therefore, show some correlation. A…

Astrophysics of Galaxies · Physics 2015-06-03 Patrick M. Koch , Ya-Wen Tang , Paul T. P. Ho

Magnetic fields, while ubiquitous in many astrophysical environments, are challenging to measure observationally. Based on the properties of anisotropy of eddies in magnetized turbulence, the Velocity Gradient Technique is a method…

On the basis of the modern understanding of MHD turbulence, we propose a new way of using synchrotron radiation, namely using synchrotron intensity gradients for tracing astrophysical magnetic fields. We successfully test the new technique…

Astrophysics of Galaxies · Physics 2018-03-21 A. Lazarian , Ka Ho Yuen , Hyeseung Lee , Jungyeon Cho

Probing magnetic fields in the interstellar medium (ISM) is notoriously challenging. Motivated by the modern theories of magnetohydrodynamic (MHD) turbulence and turbulence anisotropy, we introduce the Structure-Function Analysis (SFA) as a…

Astrophysics of Galaxies · Physics 2021-04-21 Yue Hu , Siyao Xu , A. Lazarian

Magnetic fields are a defining yet enigmatic aspect of the interstellar medium (ISM), with their three-dimensional mapping posing a substantial challenge. In this study, we harness the innovative Velocity Gradient Technique (VGT),…

Astrophysics of Galaxies · Physics 2024-01-15 Tyler Schmaltz , Yue Hu , A. Lazarian

Super-Alfvenic turbulence is important for many astrophysical objects, particularly galaxy clusters. In this paper, we explore the accuracy of Synchrotron Intensity Gradients (SIGs) and X-ray intensity gradients to map magnetic fields in…

Astrophysics of Galaxies · Physics 2024-12-04 Ka Wai Ho , Alex Lazarian

As a novel approach for tracing interstellar magnetic fields, the Velocity Gradient Technique (VGT) has been proven to be effective for probing magnetic fields in the diffuse interstellar medium (ISM). In this work, we verify the VGT in a…

Astrophysics of Galaxies · Physics 2022-01-26 Mingrui Liu , Yue Hu , Alex Lazarian

Recent development of the velocity gradient technique shows the {\toreferee capability} of the technique in the way of tracing magnetic fields morphology in diffuse interstellar gas and molecular clouds. In this paper, we perform the…

Astrophysics of Galaxies · Physics 2023-02-01 Ka Wai Ho , Alex Lazarian

The observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the…

Cosmology and Nongalactic Astrophysics · Physics 2020-01-29 Yue Hu , Ka Ho Yuen , Alex Lazarian

We use a set of magnetohydrodynamics (MHD) simulations of fully-developed (driven) turbulence to study the anisotropy in the velocity field that is induced by the presence of the magnetic field. In our models we study turbulence…

Astrophysics of Galaxies · Physics 2015-05-30 Alejandro Esquivel , Alex Lazarian

We study the properties of sub-Alfvenic magnetohydrodynamic (MHD) turbulence, i.e., turbulence with Alfven Mach number $M_A=V_L/V_A<1$, where $V_L$ is the velocity at the injection scale and $V_A$ is the Alfven velocity. We demonstrate that…

Astrophysics of Galaxies · Physics 2024-10-28 Alex Lazarian , Ka Wai HO , Ka Ho Yuen , Ethan Vishniac

We study possibility of obtaining velocity spectra by studying turbulence in an optically thick medium using velocity centroids (VCs).We find that the regime of universal, i.e. independent of underlying turbulence statistics, fluctuations…

Astrophysics of Galaxies · Physics 2016-10-12 D. Kandel , A. Lazarian , D. Pogosyan

Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this…

Astrophysics of Galaxies · Physics 2016-10-05 Che-Yu Chen , Patrick K. King , Zhi-Yun Li

The strengths of magnetic fields in interstellar gas clouds are obtained through observations of the circular polarization of spectral line radiation. Irregularities in this magnetic field may be present due to turbulence, waves or perhaps…

Astrophysics · Physics 2009-10-31 W. D. Watson , D. S. Wiebe , R. M. Crutcher

Magnetic fields and turbulence are fundamental to the evolution of galaxies, yet their precise measurement and analysis present significant challenges. The recently developed Velocity Gradient Technique (VGT), which capitalizes on the…

Astrophysics of Galaxies · Physics 2025-03-07 Yue Hu , Joseph Whittingham , A. Lazarian , Christoph Pfrommer , Siyao Xu , Thomas Berlok