The Luminosity Function of M3

Abstract

We present a high-precision, large-sample luminosity function (LF) for the Galactic globular cluster M3. With a combination of ground-based and Hubble Space T elescope data we cover the entire radial extent of the cluster. The observed LF is well Ðtted by canonical standard stellar models from the red giant branch (RGB) tip to below the main-sequence turno † point. SpeciÐcally, neither the RGB LF bump nor subgiant branch LF indicate any breakdown in the standard models. On the main sequence we Ðnd evidence for a Ñat initial mass function and for mass segregation due to the dynamical evolution of the cluster.

Models for Old, Metal‐poor Stars with Enhanced α‐Element Abundances. III. Isochrones and Isochrone Population Functions

“…At the same Z, the bump magnitudes predicted by our models agree quite well (generally to within 0.05 mag) with those reported by Cassisi & Salaris (1997 ;see their Table 1) and with those computed by Straniero, Chieffi, & Limongi (1997), as noted by Rood et al (1999). (Some di †erences can be expected as a result of the fact that the di †erent studies assume slightly di †erent helium contents and heavyelement mixtures.)…”

“…However, as noted in Paper II (see Fig. 17 therein), the three best photometric data sets currently available for M3 have zero points that di †er by up to B0.015 mag in V [I : the Stetson et al (1999) Ðducial, which we have used, is the bluest, while those by Johnson & Bolte (1998) and Rood et al (1999) are redder. Had we used either of the latter, the o †sets applied to the isochrones in Fig.…”

“…Much more critical is the adopted metallicity. For instance, Rood et al (1999) Table 1. However, as we have argued above, such a high metal abundance for M3 is problematic.…”

“…However, as we have argued above, such a high metal abundance for M3 is problematic. Indeed, Rood et al (1999) have found that it is impossible to choose a distance and metallicity such that the corresponding models are able to reproduce the entire LF. In particular, they found that a good Ðt to the subgiant LF resulted in a poor Ðt to the luminosity of the RGB bump, and vice versa.…”

Testing multimass dynamical models of star clusters with real data: mass segregation in three Galactic globular clusters

“…Indeed, GCs are stellar systems composed by billions of stars subject to their mutual gravitational attraction being the best representation in nature of the "gravitation N-body problem". Moreover, since GCs are the oldest stellar systems known, their half-mass relaxation time is often shorter that Observational evidence of mass segregation have been shown for many GCs using as a benchmark the radial variation of the mass function (MF; Da Costa 1982;Irwin & Trimble 1984;Pryor, Smith & McClure 1986;Richer, Fahlman & Vandenberg 1988;Bolte 1989;Fahlman, Richer & Nemec 1991;Drukier et al 1993;Paresce, De Marchi & Jedrzejewski 1995;De Marchi & Paresce 1996;Ferraro et al 1997;Zaggia, Piotto & Capaccioli 1997;Fischer et al 1998;Rosenberg et al 1998;Saviane et al 1998;Rood et al 1999;Andreuzzi et al 2000Andreuzzi et al , 2004Albrow, De Marchi & Sahu 2002;Lee et al 2003Lee et al , 2004Koch et al 2004;Pasquali et al 2004;Pasquato et al 2009;Balbinot et al 2009;Beccari et al 2010;Goldsbury, Heyl & Richer 2013;Martinazzi et al 2014;Frank, Grebel & Küpper 2014;Zhang et al 2015) or the radial distribution of massive objects like Blue Straggler Stars and/or binaries Ferraro et al 2012 and references therein).…”