The Globular Clusters in M87: A Bimodal Colour Distribution

Abstract

We present $V$ and $I$ photometry for $\sim 150$ globular clusters with $20<V<27$ $\sim 2.5$ arcmin from the centre of M87, the cD galaxy in the Virgo cluster. The data were acquired with the Hubble Space Telescope which, with effective resolution 0.1 arcsec, allows us for the first time to distinguish between globular clusters and most background galaxies on the basis of morphology, and to obtain accurate photometry even at faint magnitudes. The $(V-I)$ distribution of the clusters is clearly bimodal, implying a corresponding bimodality in the metallicity distribution, with peaks at [Fe/H]$\approx -1.5$ and $-0.5$. We also find that the brightest clusters are predominantly metal poor, while the fainter clusters are divided roughly eaually between metal poor and metal rich. Our sample is essentially complete to $V\approx 25$, a full magnitude past the expected peak of a ``universal" luminosity function, and the observed luminosity function is well represented by the standard gaussian distribution with $<M_V>=-7.2$ and $\sigma =1.4$.

16 pages + 4 figures, the later submitted in tar, compressed, uuencoded form. Fig. 1 not included

Cited by in corpus (16)

• Properties of Globular Cluster Systems in Nearby Early-type Galaxies
• The Ages and Abundances of the M87 Globular Clusters
• The Globular Cluster System in the Inner Region of M87
• M87, Globular Clusters, and Galactic Winds: Issues in Giant Galaxy Formation
• Globular Cluster Abundances from High-Resolution Integrated Light Spectra, I: 47 Tuc
• HST Imaging of the Globular Clusters in the Fornax Cluster: Color and Luminosity Distributions
• The Spin of M87 as measured from the Rotation of its Globular Clusters
• An optical/NIR survey of globular clusters in early-type galaxies III. On the colour bimodality of GC systems
• Dynamics of the Globular Cluster System Associated with M87 (NGC 4486). I. New CFHT MOS Spectroscopy and the Composite Database
• A Subaru/Suprime-Cam wide-field survey of globular cluster populations around M87 - II: Colour and spatial distribution
• The Survey of Centaurus A's Baryonic Structures (SCABS). II. The Extended Globular Cluster System of NGC5128 and its Nearby Environment
• An optical/NIR survey of globular clusters in early-type galaxies. I. Introduction and data reduction procedures
• On the Formation of Giant Elliptical Galaxies and Globular Clusters
• The Surface Brightness Fluctuations and Globular Cluster Populations of M87 and its Companions
• The Next Generation Virgo Cluster Survey. XXXIII. Stellar Population Gradients in the Virgo Cluster Core Globular Cluster System
• NLTE Stellar Population Synthesis of Globular Clusters using Synthetic Integrated Light Spectra I: Constructing the IL Spectra