The Globular Cluster System in the Inner Region of M87

We have identified 1057 globular cluster candidates in a WFPC2 image of the inner region of M87. The globular cluster luminosity function (GCLF) can be well fitted by a Gaussian profile with a mean value of m0V=23.67±0.07 mag and σ=1.39±0.06 mag. The GCLF in five radial bins is found to be statistically the same at all points, showing no clear evidence of dynamical destruction processes based on the luminosity function (LF). Similarly, there is no obvious trend between the half-light radius of the clusters and the galactocentric distance. The core radius of the globular cluster density distribution is Rc=56'', considerably larger than the core of the stellar component (Rc=68). The mean color of the cluster candidates is V-I=1.09 mag, which corresponds to an average metallicity of Fe/H=-0.74 dex. The color distribution is bimodal everywhere, with a blue peak at V-I=0.95 mag and a red peak at V-I=1.20 mag. The red population is only 0.1 mag bluer than the underlying galaxy, indicating that these clusters formed late in the metal-enrichment history of the galaxy and were possibly created in a burst of star/cluster formation 3-6 Gyr after the blue population. We also find that both the red and the blue cluster distributions have a more elliptical shape (Hubble type E3.5) than the nearly spherical galaxy. The average half-light radius of the clusters is ≈2.5 pc, which is comparable to the 3 pc average effective radius of the Milky Way clusters, although the red clusters are ≈20% smaller than the blue ones.

[1]  J. Kormendy.  Brightness profiles of the cores of bulges and elliptical galaxies , 1985 .

[2]  J. Ostriker,et al.  The Globular Cluster Luminosity Function as a Distance Indicator: Dynamical Effects , 1996, astro-ph/9611076.

[3]  D. Lin,et al.  Globular cluster formation - The fossil record , 1992 .

[4]  William E. Harris,et al.  GLOBULAR CLUSTER SYSTEMS IN GALAXIES BEYOND THE LOCAL GROUP , 1991 .

[5]  J. Mathis.  Interstellar dust and extinction , 1987 .

[6]  P. Côté,et al.  The Formation of Giant Elliptical Galaxies and Their Globular Cluster Systems , 1998, astro-ph/9804319.

[7]  P. Stetson.  DAOPHOT: A COMPUTER PROGRAM FOR CROWDED-FIELD STELLAR PHOTOMETRY , 1987 .

[8]  W. Harris,et al.  M87, Globular Clusters, and Galactic Winds: Issues in Giant Galaxy Formation , 1998 .

[9]  Duncan A. Forbes,et al.  On the origin of globular clusters in elliptical and cD galaxies , 1997 .

[10]  Sidney van den Bergh.  Some integrated properties of galactic globular clusters , 1996 .

[11]  Stefano Casertano,et al.  THE PHOTOMETRIC PERFORMANCE AND CALIBRATION OF WFPC2 , 1995 .

[12]  K. Freeman,et al.  Structural parameters and masses for three old LMC clusters , 1985 .

[13]  M. Weinberg,et al.  Globular cluster evolution in M87 and fundamental plane ellipticals , 1996, astro-ph/9602058.

[14]  Rene Racine,et al.  Globular Clusters in Galaxies , 1979 .

[15]  D. McLaughlin.  Was the Compact Nucleus in M87 Formed by Destroyed Globular Clusters , 1995 .

[16]  B. Whitmore,et al.  Wide Field Planetary Camera 2 Imaging of the Globular Cluster System of the S0 Galaxy NGC 3115 , 1998 .

[17]  D. Crampton,et al.  The M31 Globular Cluster System , 1985 .

[18]  D. Lin,et al.  On the motions of the Sun, the Galaxy and the Andromeda nebula , 1977 .

[19]  William E. Harris,et al.  A Catalog of Parameters for Globular Clusters in the Milky Way , 1996 .

[20]  J. Blakeslee,et al.  The Ages and Abundances of a Large Sample of M87 Globular Clusters , 1997, astro-ph/9709192.

[21]  M. Bershady,et al.  The Hubble Space Telescope Medium Deep Survey with the Wide Field and Planetary Camera. 1: Methodology and results on the field near 3C 273 , 1994 .

[22]  Ivan R. King,et al.  The structure of star clusters. III. Some simple dvriamical models , 1966 .

[23]  Stephen E. Zepf,et al.  The Formation of Globular Clusters in Merging and Interacting Galaxies , 1992 .

[24]  W. Zeilinger,et al.  Multicolour surface photometry of NGC 4486 (M87) and its jet , 1993 .

[25]  W. Harris,et al.  The spatial structure of the M87 globular cluster system , 1994 .

[26]  Destruction of the Galactic Globular Cluster System , 1996, astro-ph/9603042.

[27]  W. A. Baum.  THE DISTRIBUTION OF LUMINOSITY IN ELLIPTICAL GALAXIES , 1955 .

[28]  S. Bergh.  Radii, structure, and orbits of globular clusters , 1994 .

[29]  B. Santiago,et al.  The globular clusters in M87: a bimodal colour distribution , 1995, astro-ph/9506116.

[30]  C. Grillmair,et al.  The distribution of globular clusters associated with M 87 = NGC 4486. , 1986 .

[31]  The effect of the Galactic spheroid on globular cluster evolution , 1996, astro-ph/9604049.

[32]  G. Worthey.  Comprehensive stellar population models and the disentanglement of age and metallicity effects , 1994 .

[33]  K. Ashman,et al.  Globular cluster systems formed in galaxy mergers , 1993 .

[34]  D. Wells,et al.  The halo globular clusters of the giant elliptical galaxy Messier 87. , 1981 .

[35]  Stefano Casertano,et al.  THE PERFORMANCE AND CALIBRATION OF WFPC2 ON THE HUBBLE SPACE TELESCOPE , 1995 .

[36]  William B. Sparks,et al.  Hubble Space Telescope Observations of Globular Clusters in M87 and an Estimate of H0 , 1995 .

[37]  R. Davies,et al.  A CRITICAL REVIEW OF SELECTED TECHNIQUES FOR MEASURING EXTRAGALACTIC DISTANCES , 1992 .

[38]  Keith M. Ashman,et al.  Detecting Bimodality in Astronomical Datasets , 1994 .

[39]  R. Shaw,et al.  SOFTWARE FOR THE ANALYSIS OF EMISSION LINE NEBULAE , 1995 .

[40]  G. Vaucouleurs,et al.  On the corona of M87. , 1978 .

[41]  C. Carollo,et al.  Ellipticals with Kinematically--Distinct Cores: WFPC2 Imaging of Globular Clusters , 1996, astro-ph/9604146.

[42]  T. Lauer,et al.  The core of the M87 globular cluster system , 1986 .

[43]  O. Gnedin.  On the Evolution of the Globular Cluster Luminosity Function: The Differences , 1996, astro-ph/9610171.

[44]  B. Santiago,et al.  The M87 globular cluster system revisited , 1996 .

[45]  W. Harris.  Globular clusters in galaxies beyond the local group. V. The giant ellipticals reconsidered. , 1986 .

[46]  S. M. Fall,et al.  Survival and disruption of galactic substructure , 1977 .

[47]  J. Cohen.  Globular cluster systems of the three Virgo ellipticals , 1988 .

[48]  Jeremiah P. Ostriker,et al.  On the evolution of globular cluster systems. I - Present characteristics and rate of destruction in our Galaxy , 1988 .

[49]  Stephen E. Zepf,et al.  Globular Cluster Systems , 1998 .

[50]  R. Wade,et al.  A TWO-COLOR PHOTOMETRIC SYSTEM FOR THE NEAR INFRARED. , 1979 .

[51]  H. Ford,et al.  The Surface Brightness Fluctuations and Globular Cluster Population of NGC 4478 , 1997, astro-ph/9712339.

[52]  W. Harris,et al.  BVI Photometry of Globular Clusters in M87 , 1990 .

[53]  T. Boroson,et al.  Color distributions in early-type galaxies. I. BVRI observations with a scanning CCD , 1983 .

[54]  D. Geisler,et al.  Metal abundances for a large sample of globular clusters in M87 and NGC 1399. , 1993 .

[55]  Allan Sandage,et al.  An Alternate Calculation of the Distance to M87 Using the Whitmore et al. Luminosity Function for Its Globular Clusters: H0 Therefrom , 1996 .

[56]  C. Heiles,et al.  Reddening estimates for galaxies in the Second Reference Catalog and the Uppsala General Catalog , 1984 .