Revisiting Galactic Disk and Spiral Arms Using Open Clusters

Abstract

We use the largest catalog of open clusters in the post-Gaia era to provide an observational view of the Galactic disk. By compiling physical parameters such as age, distance, and kinematic information, we investigate the spatial distribution of open clusters and revisit the spiral arms and other asymmetries in the Galactic disk. Using young open clusters as a tracer of spiral arms, we map the spiral structure of the Galaxy and find that most of the clusters start migrating away from the spiral arms in about 10–20 Myr and fill the interarm regions as they age. Using the 3D kinematic information on 371 open star clusters, we derive different individual pattern speeds for spiral arms that closely follow the rotation curve of the Milky Way, hence favoring the transient nature of spiral arms in the Milky Way. The pattern rotation speeds of each spiral arm suggest that the spiral arms have not accelerated in the last 80 Myr. Based on the distribution of open clusters younger than 700 Myr above or below the Galactic plane, we found a solar offset of z ⊙ = 17.0 ± 0.9 pc north of the Galactic plane and estimated the scale height z h = 91.7 ± 1.9 pc from the Galactic plane.

A study on the metallicity gradients in the galactic disk using open clusters

“…For a long time, open clusters (OCs) have been used to trace the kinematical, dynamical, and chemical evolution of the galaxy (Allen et al, 1998;Minchev et al, 2014;Bobylev et al, 2019). Since OCs span a wide range of ages and chemical compositions and mostly lie in the galactic plane, they are identified as tracers of the galactic disk (Luck et al, 2011;Toyouchi and Masashi, 2014;Joshi and Malhotra, 2023). As the ages and chemical compositions of OCs can be determined with a higher precision in comparison to the field stars, they are believed to be better tracers of the temporal and chemical evolution of the galactic properties (Netopil, 2016;Magrini et al, 2017;Donor, 2018;Spina, 2021;Zhang et al, 2021;Netopil, 2022).…”

“…As the ages and chemical compositions of OCs can be determined with a higher precision in comparison to the field stars, they are believed to be better tracers of the temporal and chemical evolution of the galactic properties (Netopil, 2016;Magrini et al, 2017;Donor, 2018;Spina, 2021;Zhang et al, 2021;Netopil, 2022). With over 6,000 OCs discovered in the galaxy so far, we now have a much better understanding of their properties and, as a result, of the composition of the galaxy (Joshi and Malhotra, 2023;Magrini, 2023). In recent years, the number of OCs having metallicity information has increased significantly, with large-scale spectroscopic surveys such as the Gaia-ESO Public Spectroscopic Survey (Magrini et al, 2017), GALAH (Martell et al, 2017), APOGEE (Majewski et al, 2017;Donor, 2020), and the LAMOST survey…”