Star cluster formation and feedback in different environments of a Milky Way-like galaxy

It remains unclear how galactic environment affects star formation and stellar cluster properties. This is difficult to address in Milky Way-mass galaxy simulations because of limited resolution and less accurate feedback compared to cloud-scale models. We carry out zoom-in simulations to re-simulate 100-300 pc regions of a Milky Way-like galaxy using smoothed particle hydrodynamics, including finer resolution (0.4 M-circle dot per particle), cluster-sink particles, ray-traced photoionization from O stars, H-2/CO chemistry, and interstellar medium heating/cooling. We select similar to 10(6) M-circle dot cloud complexes from a galactic bar, inner spiral arm, outer arm, and inter-arm region (in order of galactocentric radius), retaining the original galactic potentials. The surface densities of star formation rate and neutral gas follow Sigma(SFR) proportional to Sigma(1.3)(gas), with the bar lying higher up the relation than the other regions. However, the inter-arm region forms stars two to three times less efficiently than the arm models at the same Sigma(gas). The bar produces the most massive cluster, the inner arm the second, and the inter-arm the third. Almost all clusters in the bar and inner arm are small (radii <5 pc), while 30-50 per cent of clusters in the outer arm and inter-arm have larger radii more like associations. Bar and inner arm clusters rotate at least twice as fast, on average, than clusters in the outer arm and inter-arm regions. The degree of spatial clustering also decreases from bar to inter-arm. Our results indicate that young massive clusters, potentially progenitors of globular clusters, may preferentially form near the bar/inner arm compared to outer arm/inter-arm regions.

Automated summary

It is still not clear how the galactic environment affects star formation and stellar cluster properties. Previous simulations of Milky Way-mass galaxies have limitations in resolution and accurate feedback. In this study, we conducted zoom-in simulations to re-simulate specific regions of a Milky Way-like galaxy with higher resolution and more accurate modeling. We found that the surface densities of star formation rate and neutral gas follow a certain relation in different regions, with the bar region showing higher values. The bar region also produces the most massive clusters and the inner arm region produces the second most massive clusters. The degree of spatial clustering decreases from the bar to the inter-arm region. These results suggest that young massive clusters, potentially progenitors of globular clusters, may preferentially form near the bar/inner arm compared to the outer arm/inter-arm regions.