Nature of striation in 21 cm channel Maps: velocity caustics
Hu Y. Lazarian A. Alina D. Pogosyan D. Ho K.W.
1 September 2023Oxford University Press
Monthly Notices of the Royal Astronomical Society
2023#524Issue 22994 - 3019 pp.
The alignment of striated intensity structures in thin neutral hydrogen (H i) spectroscopic channels with Galactic magnetic fields has been observed. However, the origin and nature of these striations are still debatable. Some studies suggest that the striations result solely from real cold-density filaments without considering the role of turbulent velocity fields in shaping the channels intensity distribution. To determine the relative contribution of density and velocity in forming the striations in channel maps, we analyse synthetic observations of channel maps obtained from realistic magnetized multiphase H i simulations with thermal broadening included. We vary the thickness of the channel maps and apply the Velocity Decomposition Algorithm to separate the velocity and density contributions. In parallel, we analyse GALFA-H i observations and compare the results. Our analysis shows that the thin channels are dominated by velocity contribution, and velocity caustics mainly generate the H i striations. We show that velocity caustics can cause a correlation between unsharp-masked H i structures and far-infrared emission. We demonstrate that the linear H i fibers revealed by the Rolling Hough Transform (RHT) in thin velocity channels originate from velocity caustics. As the thickness of channel maps increases, the relative contribution of density fluctuations in channel maps increases and more RHT-detected fibers tend to be perpendicular to the magnetic field. Conversely, the alignment with the magnetic field is the most prominent in thin channels. We conclude that similar to the velocity channel gradients (VChGs) approach, RHT traces magnetic fields through the analysis of velocity caustics in thin channel maps.
ISM: general , magnetic field , MHD , turbulence
Text of the article Перейти на текст статьи
Department of Physics, University of Wisconsin-Madison, Madison, 53706, WI, United States
Department of Astronomy, University of Wisconsin-Madison, Madison, 53706, WI, United States
Centro de Investigación en Astronomía, Universidad Bernardo OHiggins, General Gana 1760, Santiago, 8370993, Chile
Department of Physics, School of Sciences and Humanities, Nazarbayev University, Astana, 010000, Kazakhstan
Department of Physics, University of Alberta, Edmonton, T6G 2E1, AB, Canada
Department of Physics
Department of Astronomy
Centro de Investigación en Astronomía
Department of Physics
Department of Physics
10 лет помогаем публиковать статьи Международный издатель
Книга Публикация научной статьи Волощук 2026 Book Publication of a scientific article 2026