2008/01/31 by Chang Hyun Baek, Takahiro Kudoh, Kohji Tomisaka · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #astro-ph
paper · pdf · doi:10.1086/589556
published as Astrophys.J. 682 (2008) 434-444 · Revised the manuscript and added references, 23 pages with 9 figures
openalex publication_date 2008/07/20 · arxiv created 2008/07/21 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
The unusual mushroom-shaped H I cloud GW 123.4–1.5 is hundreds of parsecs in size but does not show any correlations to H I shells or chimney structures. To investigate the origin and velocity structure of GW 123.4–1.5, we perform three-dimensional hydrodynamical simulations of the collision of a high-velocity cloud (HVC) with the Galactic disk. We also perform a parameter study of the density, radius, and incident angle of the impact cloud. The numerical experiments indicate that we can reproduce a mushroom-shaped structure which resembles GW 123.4–1.5 in shape, size, and position velocity across the cap of the mushroom, and the density ratio between the mushroom and surrounding gas. GW 123.4–1.5 is expected to be formed by the almost head-on collision of a HVC with velocity ~100 km s −1 and mass ~10 5 M ☉ about 5 × 10 7 yr ago. A mushroom-shaped structure like GW 123.4–1.5 must be infrequent on the Galactic plane, because the head-on collision which explains the mushroom structure seems rare for observed HVCs. An HVC-disk collision explains not only the origin of the mushroom-shaped structure but also the formation of a variety of structures like shells, loops, and vertical structures in our Galaxy.