Evolution of the local spiral structure of the Milky Way revealed by open clusters

Abstract

The structure and evolution of the spiral arms of our Milky Way are basic but long-standing questions in astronomy. In particular, the lifetime of spiral arms is still a puzzle and has not been well constrained from observations. In this work, we aim to inspect these issues using a large catalogue of open clusters. We compiled a catalogue of 3794 open clusters based on Gaia EDR3. A majority of these clusters have accurately determined parallaxes, proper motions, and radial velocities. The age parameters for these open clusters are collected from references or calculated in this work. In order to understand the nearby spiral structure and its evolution, we analysed the distributions, kinematic properties, vertical distributions, and regressed properties of subsamples of open clusters. We find evidence that the nearby spiral arms are compatible with a long-lived spiral pattern and might have remained approximately stable for the past 80 million years. In particular, the Local Arm, where our Sun is currently located, is also suggested to be long-lived in nature and probably a major arm segment of the Milky Way. The evolutionary characteristics of nearby spiral arms show that the dynamic spiral mechanism might be not prevalent for our Galaxy. Instead, density wave theory is more consistent with the observational properties of open clusters.

Strong spiral arms drive secular growth of pseudo bulges in disk galaxies

“…The spiral shock could also explain the high number density and mass in the mass spectrum of gas clouds along the arms (Colombo et al 2014), shorter gas depletion associated with arms (Rebolledo et al 2012, but see Foyle et al 2010, enhanced global sSFR in strongly-armed galaxies (Seigar & James 2002;Kendall et al 2015;Yu et al 2021), offset in pitch angle of different tracers Martínez-García et al 2014;Egusa et al 2009), although the turbulence and streaming motions in the dense gas reservoir prevent cloud collapse and curtail star formation efficiency (Meidt et al 2013;Leroy et al 2017). The relative position, morphology, and kinematics of gaseous and stellar mass in the Milky Way are consistent with models based on the spiral shock (Sakai et al 2015;Hao et al 2021). Signatures supporting the inflow of gas driven by spiral arms have been detected, although a small sample size limits these studies.…”

The Spiral Structure in the Solar Neighborhood

“…In this work, we adopted the OC sample provided by Hao et al (2021), in which the OC parameters are based on the latest Gaia EDR3. There are 627 young OCs (ages < 20 Myr) in their catalogue.…”

Newly detected open clusters in the Galactic disk using Gaia EDR3

“…4, which reveals the consistency of the age estimations with the previously known OC population compiled by . Besides, it can be seen that these new OCs gradually migrated further from the Galactic disk as they age, which has been mentioned by Hao et al (2021).…”

“…An open cluster (OC) is a group of stars that formed in the same molecular cloud, so its member stars have approximately the same age and are gravitationally bound to each other. The known ages of OCs cover a wide range, from a few million years to billions of years, making them potentially good tracers for studying the structure and evolution of the Milky Way (e.g., Janes & Adler 1982;Friel 1995;Buckner & Froebrich 2014;Hao et al 2021;Castro-Ginard et al 2021a;Poggio et al 2021). In addition, all OCs play an important role in constraining stellar structure and evolutionary models (e.g., Vandenberg 1983;Barnes 2007;Bertelli Motta et al 2017;Marino et al 2018).…”