When LAMOST meets Gaia DR3

Exploring the metallicity of open clusters

¹ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, PR China
² School of Physical Science and Technology, Xinjiang University, Urumqi 830046, PR China
³ INAF-Osservatorio Astronomico di Padova, vicolo Osservatorio 5, 35122 Padova, Italy
⁴ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Universita di Padova, Vicolo Osservatorio 3, 35122 Padova, Italy
⁵ Department of Physics, Stellenbosch University, Matieland 7602, Stellenbosch, South Africa
⁶ National Institute for Theoretical and Computational Sciences (NITheCS), Stellenbosch, South Africa
⁷ Astrophysics Department, American Museum of Natural History, Central Park West, New York, NY 10024, USA
⁸ Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, PR China
⁹ School of Physics and Astronomy, Beijing Normal University, Beijing 100875, PR China
¹⁰ Institute for Advanced Studies, Technische Universität München, Lichtenbergstraße 2 a, 85748 Garching bei München, Germany
¹¹ Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210023, China

^★ Corresponding author; ruyuan.zhang@ynao.ac.cn, yl4331@columbia.edu, guosufen@ynao.ac.cn

Received: 15 May 2024
Accepted: 9 October 2024

Abstract

Context. Open clusters (OCs) are excellent probes as their age and abundance can be tightly constrained, allowing us to explore the distribution of metallicity and composition across the disk of the Milky Way. By conducting a comprehensive analysis of the metallicity of OCs, we can obtain valuable information about the history of their chemical enrichment. Moreover, by observing stars in different regions of the Milky Way, we can identify significant spatial structures in their chemical composition and abundance. This enables us to understand stellar birth radii through chemical tagging. Nevertheless, it remains challenging to infer the original positions of OCs using current data alone.

Aims. The aim of this study is to investigate the distribution of metallicity in the solar neighborhood using a large dataset from Gaia DR3 combined with LAMOST spectra. With accurate ages and metallicity measurements, we can determine birth radii for the stars and attempt to understand their migration pattern.

Methods. We chose a total of 1131 OCs within 3 kpc of the Sun from the Gaia DR3 and LAMOST DR8 low-resolution spectral database (R=1800). We used an artificial neural network to correct the LAMOST data by incorporating high-resolution spectral data from GALAH DR3 (R=28 000). The average metallicity of the OCs was determined based on the reliable [Fe/H] values for their members. We then examined the distribution of metallicity across different regions within the Galaxy and inferred birth radii of the OCs from their age and metallicity.

Results. The correction method presented here can partially eliminate the systematic offset for LAMOST data. We discuss the metal- licity trend as a function of Galactocentric distance and the guiding radii. We also compare these observational results with those from chemo-dynamic simulations. Values derived from observational metallicity data are slightly lower than predicted values when the uncertainties are not considered. However, the metallicity gradients are consistent with previous calculations. Finally, we investigated the birthplace of OCs and find hints that the majority of OCs near the Sun have migrated from the outer Galactic disk.