The OCCASO survey: Presentation and radial velocities of twelve Milky Way Open Clusters

TL;DR

The OCCASO survey provides homogeneous high-resolution spectroscopic data for 12 Milky Way open clusters, enabling improved studies of Galactic structure, chemical patterns, and kinematics.

Contribution

This study presents the first data release of radial velocities for 12 open clusters, including new high-resolution spectroscopic data for clusters previously unstudied at this level.

Findings

Radial velocities for 77 stars in 12 clusters are provided.

Clusters previously unstudied with high-resolution spectroscopy are included.

Preliminary kinematic analysis of the clusters in relation to the Galactic disc.

Abstract

Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analyzed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories survey (OCCASO). We aim to provide homogeneous radial velocities, physical parameters and individual chemical abundances of six or more Red Clump stars for a sample of 25 old and intermediate-age OCs visible from the Northern hemisphere. To do so, we use high resolution spectroscopic facilities (R> 62,000) available at Spanish observatories. We present the motivation, design and current status of the survey, together with the first data release of radial velocities for 77 stars in 12 OCs, which represents about 50% of the survey. We include clusters never studied with high-resolution spectroscopy before (NGC~1907, NGC~6991, NGC~7762), and clusters in common with other large spectroscopic surveys like the Gaia-ESO Survey (NGC~6705) and APOGEE (NGC~2682 and NGC~6819). We perform internal comparisons between instruments to evaluate and correct internal systematics of the results, and compare our radial velocities with previous determinations in the literature, when available. Finally, radial velocities for each cluster are used to perform a preliminar kinematic study in relation with the Galactic disc.