http://arxiv.org/abs/2205.04215
Simulations suggest that galactic gas disks can be treated as “modified accretion disks”, in which coplanar gas spirals into the inner regions of the disk, while being consumed by star-formation and removed by outflows. Observationally there is little evidence for such inflows within the outer disks of galaxies. Taking realistic gas surface densities from observations, the radial velocity of the inflow is only a few km s$^{-1}$ within two scalelengths, but gradually increases with radius to of order 50-100 km s$^{-1}$ at the very outer disk. The effects of this inflow on the 2-d velocity field are examined and shown to be broadly similar to those produced by warped disks, with twist distortions of both the kinematic major and minor axes. By examining the twists of kinematic distortions and the spiral arms for a sample of nearby galaxies, we find that the effect of warps are likely to dominate over the effect of radial inflows. However, we then model mock HI velocity fields that combine warps with inflow velocities of the strength required in the modified accretion disks, and show that these composite systems can actually also be very well matched by pure warped disk models, with $\sim$85\% of the mock galaxies having a mean absolute error in the residuals of less than 10 km s$^{-1}$. This suggests that the signatures of significant radial inflows can easily be “hidden” within the warps and that this may therefore explain the apparent failure to detect radial inflows in galactic disks.
E. Wang and S. Lilly
Tue, 10 May 22
49/70
Comments: 18 pages, 12 figures, submitted to AAS