Constraining Stellar Population Models. I. Age, Metallicity and Abundance Pattern Compilation for Galactic Globular Clusters

Abstract

We present an extenstive literature compilation of age, metallicity, and chemical abundance pattern information for the 41 Galactic globular clusters (GGCs) studied by Schiavon et al. (2005). Our compilation constitutes a notable improvement over previous similar work, particularly in terms of chemical abundances. Its primary purpose is to enable detailed evaluations of and refinements to stellar population synthesis models designed to recover the above information for unresolved stellar systems based on their integrated spectra. However, since the Schiavon sample spans a wide range of the known GGC parameter space, our compilation may also benefit investigations related to a variety of astrophysical endeavours, such as the early formation of the Milky Way, the chemical evolution of GGCs, and stellar evolution and nucleosynthesis. For instance, we confirm with our compiled data that the GGC system has a bimodal metallicity distribution and is uniformly enhanced in the α-elements. When paired with the

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

“…[Ca/Fe] is also enhanced in the majority of GGCs (∼ +0.3; Roediger et al (2014) [Ca/Fe] in GGCs behave similarly when compared to the α-enhanced grids is both reassuring and not surprising -both Mg and Ca are α-elements. However, as pointed out by Roediger et al (2014), the lack of any correlation between [Mg/Fe] and [Ca/Fe] in GGCs seems to suggest that, while both are indeed α-elements, they are possibly produced in different nucleosynthetic sites.…”

“…It is well established that GGCs (e.g. Burstein et al 1984;Cannon et al 1998;Roediger et al 2014) and extragalactic GCs (e.g. Burstein et al 1984;Brodie & Huchra 1991;Kuntschner et al 2002a;Strader et al 2003;Beasley et al 2004;Cenarro et al 2007b;Schiavon et al 2013) show enhanced CN when compared to solar neighbourhood stars.…”

“…The typical [Mg/Fe] for GGC stars is ∼ +0.4 (Roediger et al 2014) (Carretta et al 2001;Coelho et al 2001) and +0.32±0.08 (Barbuy et al 1992) respectively. Our result for these two clusters are also in good agreement with Lee et al (2009b) (see their figure 13).…”

Radial Trends in Imf-Sensitive Absorption Features in Two Early-Type Galaxies: Evidence for Abundance-Driven Gradients

“…Using the deprojection procedure of Gebhardt et al (1996), we find that the luminosity densities of NGC 1023 and NGC 2974 rise from 2-6 L e pc −3 at r 0.1 eff to 200-400 L e pc −3 at r 0.01 eff , comparable to the average densities of some globular clusters. An extremely high value of [Na/Fe] » 1 dex has been measured in the central 15 pc of M31 (Conroy & van Dokkum 2012b;Zieleniewski et al 2015), while red giants in the Galactic bulge and Galactic globular clusters both exhibit [Na/Fe] between 0 dex and +0.5 dex (e.g., Lecureur et al 2007;Johnson et al 2014Johnson et al , 2015Roediger et al 2014). Although support for this mechanism in globular clusters is still contentious, the rapid increase in sodium abundance toward these galaxies' densest regions is at least a plausible consequence of pollution by stellar ejecta.…”

A New Catalog of Homogenized Absorption Line Indices for Milky Way Globular Clusters From High-Resolution Integrated Spectroscopy

“…Furthermore, reliable databases for GGCs are crucial for validating and calibrating theoretical stellar population models. Many studies (e.g., Burstein et al 1984;Covino et al 1995;Cohen et al 1998;Trager et al 1998;Puzia et al 2002, hereafter PSK02;Schiavon et al 2005, hereafter SRC05; Schiavon et al 2012, hereafter S12; Pipino & Danziger 2011;Roediger et al 2014) have investigated the line-strength indices from integrated spectra of GGCs. Among them, PSK02 presents a set of Lick indices for 12 GGCs including metal-rich bulge GCs.…”