The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early-Type Galaxies

By A. Jord'an, D. McLaughlin, P. Côté, L. Ferrarese, E. Peng, S. Mei, D. Villegas, D. Merritt, J. Tonry, M. West. 2007

241 citations recorded by the source corpus.

We analyze the luminosity function of the globular clusters (GCs) belonging to the early-type galaxies observed in the ACS Virgo Cluster Survey. We have obtained maximum likelihood estimates for a Gaussian representation of the globular cluster luminosity function (GCLF) for 89 galaxies. We have also fit the luminosity functions with an "evolved Schechter function", which is meant to reflect the preferential depletion of low-mass GCs, primarily by evaporation due to two-body relaxation, from an initial Schechter mass function similar to that of young massive clusters in local starbursts and mergers. We find a highly significant trend of the GCLF dispersion σ with galaxy luminosity, in the sense that the GC systems in smaller galaxies have narrower luminosity functions. The GCLF dispersions of our Galaxy and M31 are quantitatively in keeping with this trend, and thus the correlation between σ and galaxy luminosity would seem more fundamental than older notions that the GCLF dispersion depends on Hubble type. We show that this narrowing of the GCLF in a Gaussian description is driven by a steepening of the cluster mass function above the classic turnover mass, as one moves to lower luminosity host galaxies. In a Schechter function description, this is reflected by a steady decrease in the value of the exponential cutoff mass scale. We argue that this behavior at the high-mass end of the GC mass function is most likely a consequence of systematic variations of the initial cluster mass function rather than long-term dynamical evolution. The GCLF turnover mass MTO is roughly constant, at MTO ≃ (2.2 ± 0.4) × 105 M☉ in bright galaxies, but it decreases slightly (by ~35% on average, with significant scatter) in dwarf galaxies with MB,gal ≳ -18. It could be important to allow for this effect when using the GCLF as a distance indicator. We show that part, although perhaps not all, of the variation could arise from the shorter dynamical friction timescales in less massive galaxies. We probe the variation of the GCLF to projected galactocentric radii of 20-35 kpc in the Virgo giants M49 and M87, finding that the turnover point is essentially constant over these spatial scales. Our fits of evolved Schechter functions imply average dynamical mass losses (Δ) over a Hubble time that vary more than MTO, and systematically but nonmonotonically as a function of galaxy luminosity. If the initial GC mass distributions rose steeply toward low masses as we assume, then these losses fall in the range 2 × 105 M☉ ≲ Δ < 106 M☉ per GC for all of our galaxies. The trends in Δ are broadly consistent with observed, small variations of the mean GC half-light radius in ACSVCS galaxies, and with rough estimates of the expected scaling of average evaporation rates (galaxy densities) versus total luminosity. We agree with previous suggestions that if the full GCLF is to be understood in more detail, especially alongside other properties of GC systems, the next generation of GCLF models will have to include self-consistent treatments of dynamical evolution inside time-dependent galaxy potentials.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/c6b5b7ff34b780078828e6792b08e4784e342abc

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

Probing the role of the galactic environment in the formation of stellar clusters, using M83 as a test bench (2015, methodology): “The globular cluster mass function has been reported to be well fitted by an evolved Schechter function by Jordán et al. (2007).”
The mass function of young star clusters in spiral galaxies (2008, methodology): “Indeed, a Schechter function fit to the Zhang & Fall data yields log Mc = 5.9+0.45−0.25 (Jordán et al. 2007), while an Mc that high is ruled out at high confidence level for the spirals.”
The life cycle of star clusters in a tidal field (2011, background): “Since in the homologous phaseτrh ∝ M , there should also be a uniform distribution ofM at low mass, ordN/dM ≃ const (Hénon 1961; Fall & Zhang 2001), which is indeed found in many galaxies (Jordán et al. 2007).”
The formation and assembly history of the Milky Way revealed by its globular cluster population (2018, background): “…projected z = 0 halo masses, the observed relation between the GC system mass and the dark matter halo mass at z = 0 (MGCs/M200 = 3×10−5, Durrell et al. 2014; Harris et al. 2017), and the mean GC mass at M > 105 M , which is M = 4.7× 105 M for a typical GC mass function (e.g. Jordán et al. 2007).”
On the star formation rate – brightest cluster relation: estimating the peak star formation rate in post-merger galaxies (2008, result): “This particular limit is similar to that found by Gieles et al. (2006a,b) and used by Jordán et al. (2007), and will be justified further in Section 4.1.”
On the fraction of star formation occurring in bound stellar clusters (2012, background): “…co-formation and co-evolution of (old) star cluster populations and galaxies may eventually produce the present-day cluster systems across the entire galaxy mass range (for typical observables of interest, see e.g. Peng et al. 2006; Jordán et al. 2007; Peng et al. 2008; Burkert & Tremaine 2010).”
THE ACS VIRGO CLUSTER SURVEY XVI. SELECTION PROCEDURE AND CATALOGS OF GLOBULAR CLUSTER CANDIDATES (2008, methodology): “The GC selection method and the procedure to determine the aperture corrections described in this work have also been applied to the ACS Fornax Cluster Survey (Jordán et al. 2007b; Côté et al. 2007).”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, methodology): “…to have emerged from HST imaging surveys of nearby galaxies during the past decade, particularly the ACSVCS and ACSFCS (Côté et al. 2004, 2007; Jordán et al. 2007), is the discovery that most intermediate- and low-mass galaxies contain structurally distinct stellar components in their…”
From star clusters to dwarf galaxies: the properties of dynamically hot stellar systems (2008, background): “…surveys of extragalactic GC systems show (e.g. Larsen et al. 2001; Chandar et al. 2004 and Jordán et al. 2005 concerning the radii of GCs, and Richtler 2003 and Jordán et al. 2007 concerning the absolute magnitudes of GCs, which indicate their masses if a constant M/L ratio for them is assumed).”
Globular cluster systems in nearby dwarf galaxies – III. Formation efficiencies of old globular clusters (2010, result): “The results of Jordán et al. (2007) show that the dispersion (σ) and turn-over luminosity (lTO) of the GCLF changes as a function of host galaxy luminosity.”
A CATALOG OF GLOBULAR CLUSTER SYSTEMS: WHAT DETERMINES THE SIZE OF A GALAXY'S GLOBULAR CLUSTER POPULATION? (2013, methodology): “More detailed analysis suggests that a slightly asymmetric form such as the “evolved Schechter function” developed by Jordán et al. (2006, 2007) is a better match to the data.”
GALAXIES AT THE EXTREMES: ULTRA-DIFFUSE GALAXIES IN THE VIRGO CLUSTER (2015, background): “Adopting a Gaussian globular cluster luminosity function with a turnover at gTO = 23.8± 0.2 and σ = 1 mag (Jordán et al. 2007), the total inferred GC population is NGC,tot = 9±4.5.”
Globular clusters as the relics of regular star formation in ‘normal’ high-redshift galaxies (2015, background): “Such a strong environmental variation is is not observed (Vesperini et al. 2003; Jordán et al. 2007; McLaughlin & Fall 2008).”
The SLUGGS Survey: kinematics for over 2500 globular clusters in 12 early-type galaxies (2012, background): “Conversely, the completeness of the HST photometry in z (V) band is typically above 90 (70) per cent at the turnover magnitude even in the innermost regions, respectively (Larsen et al. 2001; Jordán et al. 2007).”