Properties of Globular Cluster Systems in Nearby Early-Type Galaxies

By S. Larsen, J. Brodie, J. Huchra, D. Forbes, C. Grillmair. 2001

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We present a study of globular clusters (GCs) in 17 relatively nearby early-type galaxies, based on deep F555W and F814W images from the Wide Field Planetary Camera 2, on board the Hubble Space Telescope. A detailed analysis of color distributions, cluster sizes, and luminosity functions is performed and compared with GCs in the Milky Way. In nearly all cases, a KMM test returns a high confidence level for the hypothesis that a sum of two Gaussians provides a better fit to the observed color distribution than a single Gaussian, although histograms of the (V-I)0 distribution are not always obviously bimodal. The blue and red peak colors returned by the KMM test are both found to correlate with absolute host galaxy B-band magnitude and central velocity dispersion (at about the 2–3 σ level). Red GCs are generally smaller than blue GCs by about 20%. The size difference is seen at all radii at least out to 4′ and within sub-bins in (V-I)0 color, and exists also in the Milky Way and Sombrero (M104) spiral galaxies. Fitting t5 functions to the luminosity functions of blue and red GC populations separately, we find that the V-band turnover of the blue GCs is brighter than that of the red ones by about 0.3 mag on the average, as expected if the two GC populations have similar ages and mass distributions but different metallicities. Brighter than the turnover at MV ∼ -7.5, the luminosity functions (LFs) are well approximated by power laws with an exponent of about -1.75. This is similar to the LF for young star clusters, suggesting that young and old globular clusters form by the same basic mechanism. We discuss scenarios for GC formation and conclude that our data appear to favor in situ models in which all GCs in a galaxy formed after the main body of the protogalaxy had assembled into a single potential well.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9efd5255742647a71e513ad077c3785bc77c77fd

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Citations in the corpus

On the formation of globular cluster systems in a hierarchical Universe (2002, methodology): “…metallicities of GC systems (and their sub-populations) correlate with host galaxy luminosity has been a controversial one (e.g. Brodie & Huchra 1990; Ashman & Bird 1993; Secker et al. 1995; Durrell et al. 1996; Forbes et al. 1996; Kundu & Whitmore 2001; Forbes & Forte 2001; Larsen et al. 2001).”
The ACS Virgo Cluster Survey. XII. The Luminosity Function of Globular Clusters in Early-Type Galaxies (2007, background): “Larsen et al. (2001) studied the GCLF for 17 nearby early-type galaxies.”
On the fraction of star formation occurring in bound stellar clusters (2012, background): “…but it is also a key ingredient for work that aims to trace the (star) formation histories of galaxies using their star cluster populations (e.g. Larsen et al. 2001; Bastian et al. 2005; Smith et al. 2007; Konstantopoulos et al. 2009; Fedotov et al. 2011), or studies of star cluster disruption…”
A CATALOG OF GLOBULAR CLUSTER SYSTEMS: WHAT DETERMINES THE SIZE OF A GALAXY'S GLOBULAR CLUSTER POPULATION? (2013, background): “The MDF in particular – in most cases measured through broadband color indices – has stimulated much ongoing discussion of the cluster formation process (e.g. Ashman & Zepf 1992; Larsen et al. 2001; Peng et al. 2006; Harris 2009; Spitler et al. 2008; Mieske et al. 2010, among many others).”
Extragalactic Globular Clusters and Galaxy Formation (2006, background): “Subsequently, a correlation between the color of just the metal-rich GCs and host galaxy luminosity was found by Forbes et al. (1997), Larsen et al. (2001a), and Forbes & Forte (2001).”
The Colors of Dwarf Elliptical Galaxy Globular Cluster Systems, Nuclei, and Stellar Halos (2004, result): “In the bottom panel of Figure 4, we plot the dE 〈V −I〉GC and σ(V −I) with the results of bi-modal Gaussian fits to “red” and “blue” globular cluster peaks for 16 E/S0s (Larsen et al. 2001).”
The bifurcated age–metallicity relation of Milky Way globular clusters and its implications for the accretion history of the galaxy (2013, background): “…parameter (c = log10(rt/r0); Harris 2010) and progenitor mass in the top right panel of Figure 8 is particularly interesting in light of the correlation between GC size and colour (or metallicity) seen in the MW and many extragalactic GC systems in giant ellipticals (e.g., Larsen et al. 2001).”
THE NEXT GENERATION VIRGO CLUSTER SURVEY (NGVS). I. INTRODUCTION TO THE SURVEY (2012, methodology): “The power of high-quality, homogeneous imaging for star clusters in large samples of galaxies was demonstrated by early archival programs with HST (Gebhardt & Kissler-Patig 1999; Kundu & Whitmore 2001; Larsen et al. 2001).”
BEASTS OF THE SOUTHERN WILD: DISCOVERY OF NINE ULTRA FAINT SATELLITES IN THE VICINITY OF THE MAGELLANIC CLOUDS (2015, background): “It is interesting that in the size luminosity plane the ambigiously classified objects in our sample seem to join the sequence of objects observed in other galaxies labelled as faint-fuzzies (FF) or Extended Clusters (EC) (see Larsen et al. 2001; Brodie et al. 2011; Forbes et al. 2013).”
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).”
The ACS Virgo Cluster Survey. I. Introduction to the Survey (2004, methodology): “This latter filter/camera combination is the most commonly used in previous HST studies of extragalactic GC systems and SBF measurements (e.g., Gebhardt & Kissler-Patig 1999; Kundu & Whitmore 2001; Larsen et al. 2001; Ajhar et al. 1997; Neilsen & Tsvetanov 2000).”
WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, background): “Larsen et al. (2001) suggested approximate uncertainties of 1 pc for WFPC2 data of GCs in Virgo cluster galaxies, but the bulk of their objects were fainter than ours.”
The Luminosity Function of Star Clusters in Spiral Galaxies (2002, methodology): “With adequate signal-to-noise ratio (S/N), objects with intrinsic FWHM down to 0.2 pixels can be resolved by ISH- APE (e.g., Larsen et al. 2001c), corresponding to about 0.8 pc at the assumed distance of NGC 6946.”
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters (2005, methodology): “And in M87 a hint of this same feature may also be seen in the WFPC2 observations of Whitmore et al. (1995) and Larsen et al. (2001), though both the sample size and metallicity sensitivity of the (V − I) index used there are too low to make it unambiguous.”
The Globular Cluster System of NGC 1399. I. A Wide-Field Photometric Study (2003, background): “The GCLF is frequently used as a distance indicator for early-type galaxies because of its universal peak luminosity (e.g., Harris et al. 1991, Harris 2001; Ashman, Conti, & Zepf 1995; Kundu &Whitmore 2001a; Larsen et al. 2001).”
The ACS Virgo Cluster Survey. X. Half-Light Radii of Globular Clusters in Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for Distance Estimation (2005, background): “…that, in the mean, the half-light radii of GCs, 〈rh〉, depends on their color (g−z)gc, with the red GCs being ≈ 20% smaller than their blue counterparts (Kundu & Whitmore 1998; Kundu et al. 1999; Puzia et al. 1999; Larsen, Forbes & Brodie 2001; Barmby, Holland & Huchra 2002; Larsen et al. 2001).”
Globular Clusters in Virgo Ellipticals: Unexpected Results for Giants and Dwarfs from Advanced Camera for Surveys Imaging (2005, methodology): “Among the largerHST studies of early-type galaxies using deep imaging are Larsen et al. (2001) and Kundu & Whitmore (2001).”