2014/06/12 by S. Haan, Haan, Sebastian, Róbert Braun +1
Physics and Astronomy · #Astrophysics and Star Formation Studies #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.1406.3354
openalex publication_date 2014/06/12 · openalex created_date 2025/10/24 · openalex updated_date 2026/07/28
While most ram pressure studies have focused on ram pressure stripping in\ngalaxy clusters, we devise a novel approach based on a kinematic measurement of\nram pressure perturbations in HI velocity fields for intergalactic material\n(IGM) densities and relative velocities that are one to two orders of magnitude\nlower than in galaxies showing ram pressure stripping. Our model evaluates ram\npressure induced kinematic terms in gas disks with constant inclination as well\nas those with a warped geometry. Ram pressure perturbations are characterized\nby kinematic modes of even order, m=0 and m=2, corresponding to a ram wind\nperpendicular and parallel to the gas disk, respectively. Long-term\nconsequences of ram pressure, such as warped disks as well as uncertainties in\nthe disk geometry typically generate uneven modes (m=1 and m=3), that are\nclearly distinguishable from the kinematic ram pressure terms. We have applied\nour models to three nearby isolated galaxies, utilizing Markov Chain Monte\nCarlo fitting routines to determine ram pressure perturbations in the velocity\nfields of NGC 6946 and NGC 3621 of ~30km s-1 (effective line-of-sight\nvelocity change) at HI column densities below (4-10)\×1020cm-2\n(at radial scales greater than ~15kpc). In contrast, NGC 628 is dominated by a\nstrongly warped disk. Our model fits reveal the three-dimensional vector of the\ngalaxies' movement with respect to the IGM rest-frame and provide constraints\non the product of speed with IGM density, opening a new window for\nextragalactic velocity measurements and studies of the intergalactic medium.\n