The OCCASO survey: presentation and radial velocities of 12 Milky Way open clusters

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.

The open cluster King 1 in the second quadrant

“…The mean radial velocity derived in Section 5 yields to radial velocities with respect to the galactic standard of rest (GSR) and the regional standard of rest (RSR) of 178.3 ± 11.6 and −4.5 ± 11.8 km s 1 , respectively. The values have been computed as in Casamiquela et al (2016). In comparison with the clusters studied in that paper, the values of King 1 are in good agreement with those of NGC 7789, in spite of the different ages.…”

“…For this purpose we have analysed two well know stars: Arcturus and µ Leo. Since these stars have not been observed with AF2, we have smoothed the high-resolution high signal-to-noise spectra obtained with HERMES at the Mercator telescope (La Palma, Spain) in the framework of the Open Clusters Chem- ical Abundance from Spanish Observatories project (OC-CASO; Casamiquela et al 2016) to match the AF2 resolution. Moreover, we have degraded the signal-to-noise ratio of these spectra to ∼20 to match those of the spectra used in this work.…”

Characterising open clusters in the solar neighbourhood with the Tycho-Gaia Astrometric Solution

“…We computed the cylindrical (U S , V S , W S ) 1 components of the peculiar motion as described in Sect. 3.5.1 of Casamiquela et al (2016), adopting a Galactic rotation curve with Θ 0 = 240 km s −1 , R = 8.34 kpc, and dR dΘ = −0.2 km s −1 kpc −1 , and taking into account the Sun's own peculiar motion as (U , V , W ) = (10.7, 15.6, 8.9) km s −1 (Reid et al 2014). The results of this computation are listed in Table 5 and shown in Fig.…”

The Swift UVOT Stars Survey. III. Photometry and Color–Magnitude Diagrams of 103 Galactic Open Clusters

“…The only estimates of age and distance come from the global survey of K16. Casamiquela et al(2016) studied the radial velocity but did not measure metallicity. The cluster is quite large (K13 measure a radius of 26.…”