TheGaia-ESO Survey

Abstract

We use Gaia-ESO Survey iDR4 data to explore the Mg-Al anti-correlation in globular clusters, that were observed as calibrators, as a demonstration of the quality of Gaia-ESO Survey data and analysis. The results compare well with the available literature, within 0.1 dex or less, after a small (compared to the internal spreads) offset between the UVES and the GIRAFFE data of 0.10-0.15 dex was taken into account. In particular, we present for the first time data for NGC 5927, one of the most metal-rich globular clusters studied in the literature so far with [Fe/H]=-0.49 dex, that was included to connect with the open cluster regime in the Gaia-ESO Survey internal calibration. The extent and shape of the Mg-Al anti-correlation provide strong constraints on the multiple population phenomenon in globular clusters. In particular, we studied the dependency of the Mg-Al anti-correlation extension with metallicity, present-day mass, and age of the clusters, using GES data in combination with a large set of homogenized literature measurements. We find a dependency with both metallicity and mass, that is evident when fitting for the two parameters simultaneously, but no significant dependency with age. We confirm that the Mg-Al anti-correlation is not seen in all clusters, but disappears for the less massive or most metal-rich ones. We also use our dataset to see whether a normal anti-correlation would explain the low [Mg/α] observed in some extragalactic globular clusters, but find that none of the clusters in our sample can reproduce it, and more extreme chemical compositions (like the one of NGC 2419) would be required. We conclude that GES iDR4 data already meet the requirements set by the main survey goals, and can be used to study in detail globular clusters even if the analysis procedures were not specifically designed for them.

Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – II. The Southern clusters and overview

“…This was verified by Mészáros et al (2015) and by Masseron et al (2019) using the APOGEE line list, but effective temperatures and surface gravities independent of ASPCAP. Interestingly, Pancino et al (2017) have also found a similar, although slightly smaller, 0.08 dex higher metallicities than Carretta et al (2009c) in the 7 clusters in common with our sample. This latter study was carried out by the Gaia-ESO survey, completely independent of APOGEE observations and using optical spectra instead of the H-band.…”

“…We show the four different iron scales on the top left panel of Figure 4. We find that the [Fe/H] metallicities we derive are on average 0.162 dex higher than those from the Harris catalog, 0.154 dex higher than Carretta et al (2009c), 0.064 dex higher than Pancino et al (2017).…”

“…We compare our metallicity scale with those of the Harris catalog, Carretta et al (2009c) and Gaia-ESO (Pancino et al 2017). The Harris catalog is a compilation of various literature sources and all our clusters were selected from it.…”

“…With the appearance of high spectral resolution sky surveys some of these southern clusters were revisited by the Gaia-ESO survey (Gilmore et al 2012) focusing on the same two element pairs (Pancino et al 2017). The first homogeneous exploration of 10 northern clusters was carried out by Mészáros et al (2015), which was updated by Masseron et al (2019), both using data from the SDSS-III (Eisenstein et al 2011) Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey.…”

When Does the Onset of Multiple Stellar Populations in Star Clusters Occur? III. No Evidence of Significant Chemical Variations in Main-sequence Stars of NGC 419

“…Almost all old globular clusters (GCs, older than ∼10 Gyr) are composed of multiple stellar populations (MPs). One signature of MPs is stars in GCs are not chemically homogeneous: they exhibit star-to-star variations in different elemental abundances, such as He, C, N, O, Na, Mg, Al, etc (Piotto et al 2007;Yong et al 2008;Carretta et al 2009;di Criscienzo et al 2010;Lardo et al 2012;Wang et al 2017;Pancino et al 2017;Milone et al 2019). The number of chemically enriched stars is comparable to, or greater than normal stars (Carretta et al 2009;Milone et al 2012b;.…”