On the formation of globular cluster systems in a hierarchical Universe

By M. Beasley, C. Baugh, D. Forbes, Ray Sharples, Carlos S. Frenk. 2002

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ABSTRA C T We have investigated the formation of globular cluster (GC) systems in the fiducial semianalytic model of galaxy formation of Cole et al., by assuming that GCs are formed at high redshifts ﷿z . 5fi in protogalactic fragments, and during the subsequent gas-rich merging of these fragments. Under these assumptions we have simulated the GC systems of 450 elliptical galaxies, and find that the majority (93 per cent) are intrinsically bimodal in metallicity. We find that, in the mean, the metal-rich GC subpopulations are younger than the metal-poor GC subpopulations, with ages of 9 and 12 Gyr respectively, and that the mean ages of the metalrich GCs are dependent upon host galaxy luminosity and environment (halo circular velocity), whereas the metal-poor GCs are not. We find that the continued gaseous merging of the protogalactic fragments leads to significant age-structure amongst the metal-rich GCs. These GCs exhibit a large age-range (5 to 12 Gyr), which increases for low-luminosity galaxies, and for galaxies in low circular velocity haloes. Moreover, the metal-rich GCs associated with low-luminosity field and/or group ellipticals are , 2 Gyr younger than the metal-rich GCs in luminous cluster ellipticals. We find that the total GC populations scale with host galaxy luminosity as NGC / L 1:25 V;gal , a result in agreement with observations of luminous elliptical galaxies. This scaling is due to a systematic increase in the M/L ratios of the galaxy haloes with luminosity for LV;gal . L * galaxies in the model. A comparison between the luminosity growth of the model ellipticals and their GC formation indicates that mergers do not significantly affect SN at z , 2. We find the mean colours of the both the metal-rich and metal-poor GCs exhibit only a weak dependence upon host galaxy luminosity, a result consistent with contemporary observations. We conclude that gaseous merging, the bulk of which occurs at 1 # z # 4i n ourLCDM model, leads to the formation of the metalrich peak of the GC systems of elliptical galaxies. We suggest that the formation and subsequent truncation of the metal-poor GCs in the protogalactic fragments is closely related to the star formation rate in these fragments, which may have been significantly higher at very early times.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/989ef05c3b30a3cf8a3e393cece786c964f92a84

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Citations in the corpus

VLT spectroscopy of globular cluster systems - II. Spectroscopic ages, metallicities and [α/Fe] ratios of globular clusters in early-type galaxies (2005, methodology): “(Trager et al. 1998; Puzia et al. 2005), and the LMC (Beasley et al. 2002b).”
The SLUGGS Survey: kinematics for over 2500 globular clusters in 12 early-type galaxies (2012, background): “The challenge of producing simulations of GC bimodality formation is intertwined with our poor understanding of how GC systems formed in the first place (e.g. Beasley et al. 2002; Elmegreen, Malhotra & Rhoads 2012).”
Extragalactic Globular Clusters and Galaxy Formation (2006, methodology): “In the Galaxy formation model of Searle & Zinn (1978) and in many subsequent studies of GC formation, it was envisioned that metal-poor GCs form in protogalactic dwarf-sized clumps (e.g., Harris & Pudritz 1994; Forbes et al. 1997; Côté et al. 1998; Beasley et al. 2002).”
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters (2005, background): “A similar view has frequently been argued on other grounds (Harris & Pudritz 1994; Burgarella et al. 2001; Harris & Harris 2002; Beasley et al. 2002; Kravtsov & Gnedin 2005).”
WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, background): “In each giant galaxy, an interruption in the early, intense star formation period may have produced a break in GC metallicity (e.g., Beasley et al. 2002), with a radial gradient in each subpopulation reflecting the dissipative nature of this period.”
The Globular Cluster System of NGC 1399. I. A Wide-Field Photometric Study (2003, background): “Various models have been published that explain the observed bimodality/metallicity distribution, e.g., Ashman & Zepf (1992), Forbes, Brodie, & Grillmair (1997), Côté et al. (2001), and Beasley et al. (2002).”
The bifurcated age–metallicity relation of Milky Way globular clusters and its implications for the accretion history of the galaxy (2013, background): “Alternatively in-situ theories, which were envisioned to explain blue GC populations with a narrow range of old ages (Forbes, Brodie & Grillmair 1997; Beasley et al. 2002), typically find that the MP GCs should be older by > 2 Gyr than the MR GCs and have a very narrow range of ages.”
MODELING THE METALLICITY DISTRIBUTION OF GLOBULAR CLUSTERS (2010, methodology): “It is consistent with typical major merger criteria used in the literature (e.g., Beasley et al. 2002 use p3 = 0.3).”
GCD+: a new chemodynamical approach to modelling supernovae and chemical enrichment in elliptical galaxies (2002, background): “…chemical evolution make it possible to relate the observed chemical properties of galaxies to cosmological theory (e.g. Kauffmann & ⋆ E-mail: dkawata,bgibson@astro.swin.edu.au Charlot 1998; Cole et al. 2000; Okamoto & Nagashima 2001; Somerville, Primack, & Faber 2001; Beasley et al. 2002).”
Formation of Globular Clusters in Hierarchical Cosmology (2003, background): “However, Beasley et al. (2002) truncated the formation of blue clusters arbitrarily at z ¼ 5 to create a distinctly bimodal distribution of colors in their model.”