From theory to observation: understanding filamentary flows in high-mass star-forming clusters

TL;DR

This paper tackles how mass moves through filamentary networks to form high-mass star clusters by using multi-scale galactic MHD simulations and FilFinderPPV to identify filaments and quantify three flow-rate components (along, onto, polar) across active and quiet environments and multiple inclinations. It validates the observational approach by comparing flow rates derived from PPV data with true 3D PPP values, revealing that environment and feeder filaments fundamentally shape flow patterns on tens of parsecs. The results show along-filament flows of order $10^{-4}$–$10^{-5}\,\mathrm{M}_{\odot}\,\mathrm{yr}^{-1}$ and onto/polar flows typically smaller, with feeders distributing material and enabling sustained accretion toward hubs. The findings confirm that filamentary dynamics depend strongly on galactic environment and projection, and they demonstrate that observational flow-rate methods can faithfully recover underlying 3D flows, providing a robust framework for interpreting filament-mediated star formation in galaxies.

Abstract

Here we use data from multi-scale galactic MHD simulations to observe filaments and star forming clumps on 10's of pc scales and investigate flow rate relationships along, and onto filaments as well as flows towards the clumps. Using the FilFinderPPV identification technique, we identify the prominent filamentary structures in each data cube. Each filament and its corresponding clump are analysed by calculating flow rates along each filament towards the clump, onto each filament from increasing distances, and radially around each clump. This analysis is conducted for two cubes, one feedback dominated region, and one with less feedback. Looking at the face-on inclination of the simulations (0 degrees), we observe different trends depending on the environmental conditions (more or less feedback). The median flow rate in the region with more feedback is 8.9$\times$10$^{-5}$ M$_{sun}\mathrm{yr}^{-1}$ and we see that flow rates along the filaments toward the clumps generally decrease in these regions. In the region with less feedback we have a median flow rate of 2.9$\times$10$^{-4}$ M$_{sun}\mathrm{yr}^{-1}$ and when looking along the filaments here we see the values either increase or remain constant. We find that the flow rates from the environments onto the primary filaments are of an order of magnitude sufficient to sustain the flow rates along these filaments. When discussing the effects of galactic and filamentary inclination, we also observe that viewing the filaments from different galactic inclinations can reveal the presence of feeder structures (smaller filamentary structures aiding in the flow of material). The method used to estimate these flow rates, which has been previously applied to observational data, produced results consistent with those obtained from the simulations themselves, providing high confidence in the flow rate calculation method.

Figures (14)

• Figure 1: Galaxy overview from ZhaoPudritz2024. The central panels show the two snapshots of the galaxy we are using, the top showing the location of the less feedback dominated region (quiet) and the bottom showing the location of the feedback-dominated region (active). The first zoom-in panels show the regions down to a few kpc (top left and bottom right panels), followed by the close ups of the regions in 100 x 100 pc boxes (bottom left and top right panels).
• Figure 2: Density projections of high-resolution zoom-in simulation data of ZhaoPudritz2024. White streamlines represent magnetic field structure. Quivers show velocity direction and magnitude relative to the velocity of the central cores in each snapshot.
• Figure 3: 0th moment maps of the column density cubes with the identified filamentary structure, colour coded by velocity, overlaid on top. 2.85 pc scale bars are shown in the top right corners.
• Figure 4: 0th moment map of the Active column density cube with the identified filamentary structure, colour coded by velocity, overlaid on top. Green, red and blue points indicating the different types of flow rate, green is along the filamentary structure, red is onto, and blue is polar around the clumps. 2.85 pc scale bar in the top right corner.
• Figure 5: Distributions of flow rates Left: along filaments Right: onto the filaments in the active cube.