THE CHEMICAL PROPERTIES OF MILKY WAY AND M31 GLOBULAR CLUSTERS. I. A COMPARATIVE STUDY

A comparative analysis is performed between high-quality integrated spectral indices of 30 M31 globular clusters, 20 Milky Way globular clusters, and a sample of field and cluster elliptical galaxies. We find that the Lick CN indices in the M31 and Galactic clusters are enhanced relative to the bulges of the Milky Way, M31, and elliptical spheroids, in agreement with Burstein and coworkers. Although not particularly evident in the Lick CN indices, the near-UV cyanogen feature (?3883) is strongly enhanced with respect to the Galactic globular clusters at metallicities -1.5 -0.8, we observe no systematic differences in the H?, H?, or H? indices between the M31 and Galactic globular clusters, in contrast to previous studies. The elliptical galaxy sample lies offset from the loci of the globular clusters in both the cyanogen-[MgFe] and Balmer-line?[MgFe] planes. Six of the M31 clusters appear young and are projected onto the M31 disk. Population synthesis models suggest that these are metal-rich clusters with ages 100?800 Myr, metallicities -0.20 ? [Fe/H] ? 0.35, and masses 0.7? ~ 7.0 ? 104 M?. Two other young clusters are Hubble V in NGC?205, observed as a template, and an older (~3 Gyr) cluster some 7 kpc away from the plane of the disk. The six clusters projected onto the disk show signs of rotation similar to the H I gas in M31, and three clusters exhibit thin disk kinematics, according to Morrison and coworkers. Dynamical mass estimates and detailed structural parameters are required for these objects to determine whether they are massive open clusters or globular clusters. If they are the latter, our findings suggest globular clusters may trace the buildup of galaxy disks. In either case, we conclude that these clusters are part of a young, metal-rich disk cluster system in M31, possibly as young as 1 Gyr old.

[1]  Rupali Chandar,et al.  The Globular cluster systems of five nearby spiral galaxies: New insights from Hubble Space Telescope imaging , 2004, astro-ph/0407460.

[2]  A. Weiss,et al.  Homogeneous age dating of 55 Galactic globular clusters. Clues to the Galaxy formation mechanisms , 2002 .

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

[4]  J. Huchra,et al.  Spectroscopy of Globular Clusters in M81 , 2001, astro-ph/0111063.

[5]  On the formation of globular cluster systems in a hierarchical Universe , 2002, astro-ph/0202191.

[6]  Thomas H. Puzia,et al.  Integrated spectroscopy of bulge globular clusters and fields - I. The data base and comparison of individual Lick indices in clusters and bulge , 2002 .

[7]  V. Rubin,et al.  Rotation of the Andromeda Nebula from a Spectroscopic Survey of Emission Regions , 1970 .

[8]  G. Chabrier.  Galactic Stellar and Substellar Initial Mass Function , 2003, astro-ph/0304382.

[9]  D. Minniti.  Metal-rich globular clusters with R≤3 KPC: Disk or bulge clusters? , 1995 .

[10]  A comparison of stellar populations in galaxy spheroids across a wide range of Hubble types , 2002, astro-ph/0202390.

[11]  R. Zinn,et al.  Compositions of halo clusters and the formation of the galactic halo , 1978 .

[12]  Nicholas B. Suntzeff,et al.  Spectroscopy of giants in LMC clusters. I. Velocities, abundances, and the age-metallicity relation , 1991 .

[13]  B. Madore,et al.  A DISTANT STAR CLUSTER IN HYDRA, AM-4. , 1982 .

[14]  M. Lee.  Stellar Populations in the Central Region of the Dwarf Elliptical Galaxy NGC 205 , 1996 .

[15]  N. Suntzeff,et al.  Carbon and nitrogen abundances in giant stars of the metal-poor globular cluster M92 , 1982 .

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

[17]  David Burstein,et al.  Old Stellar Populations. VI. Absorption-Line Spectra of Galaxy Nuclei and Globular Clusters , 1997, astro-ph/9712258.

[18]  J. Huchra,et al.  Extragalactic Globular Clusters. III. Metallicity Comparisons and Anomalies , 1991 .

[19]  G. Bruzual,et al.  Stellar population synthesis at the resolution of 2003 , 2003, astro-ph/0309134.

[20]  David Burstein,et al.  Old stellar populations. I. A spectroscopic comparison of galactic globular clusters, M 31 globular clusters, and elliptical galaxies. , 1984 .

[21]  U. Padova,et al.  Galactic globular cluster relative ages , 1999, astro-ph/9907394.

[22]  Sidney van den Bergh,et al.  PHOTOMETRIC AND SPECTROSCOPIC OBSERVATIONS OF GLOBULAR CLUSTERS IN THE ANDROMEDA NEBULA. , 1969 .

[23]  R. Zinn.  The globular cluster system of the galaxy. IV - The halo and disk subsystems , 1985 .

[24]  D. Burstein,et al.  Nitrogen Overabundance: Globular Cluster and Halo Formation , 2003, astro-ph/0310441.

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

[26]  W. Sargent,et al.  Search for globular clusters in M31. I - The disk and the minor axis , 1977 .

[27]  D. Ottaviani,et al.  Hγ and Hδ Absorption Features in Stars and Stellar Populations , 1997 .

[28]  M. Tripicco.  Spectroscopy of metal-rich M31 globular clusters , 1986 .

[29]  J. Cohen.  The age-metallicity relationship for the clusters of the Large Magellanic Cloud. , 1982 .

[30]  David Burstein,et al.  Old stellar populations. 5: Absorption feature indices for the complete LICK/IDS sample of stars , 1994 .

[31]  Judith G. Cohen,et al.  Carbon Abundances of Faint Stars in M13: Evidence of Two Abundance-altering Mechanisms* , 2002, astro-ph/0210121.

[32]  Judith G. Cohen,et al.  The Chemical Inhomogeneity of Faint M13 Stars: Carbon and Nitrogen Abundances , 2003, astro-ph/0312315.

[33]  J. B. Oke.  Faint Spectrophotometric Standard Stars , 1990 .

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

[35]  TO APPEAR IN THE ASTROPHYSICAL JOURNAL LETTERS Preprint typeset using L ATEX style emulateapj v. 04/03/99 EVIDENCE FOR A SIGNIFICANT INTERMEDIATE-AGE POPULATION IN THE M31 HALO FROM , 2003 .

[36]  S. Bergh.  Stellar Populations in Galaxies , 1972 .

[37]  Michel Casse,et al.  Origin and evolution of the elements , 1993 .

[38]  M31's Undisturbed Thin Disk of Globular Clusters , 2003, astro-ph/0307302.

[39]  Michael J. West,et al.  Evidence for the Hierarchical Formation of the Galactic Spheroid , 1999, astro-ph/9911527.

[40]  J. Mould,et al.  The continuity of cluster formation in the Large Magellanic Cloud , 1988 .

[41]  J. P. Huchra,et al.  The Kinematics and Metallicity of the M31 Globular Cluster System , 2002, astro-ph/0205026.

[42]  C. Baugh,et al.  Evolution of the Hubble sequence in hierarchical models for galaxy formation , 1996, astro-ph/9602085.

[43]  UCOLick,et al.  The Stellar Population Histories of Early-Type Galaxies. II. Controlling Parameters of the Stellar Populations , 2000, astro-ph/0004095.

[44]  H. Ford,et al.  Star Clusters in M33. I. Detection, Morphology, and Photometry , 1999 .

[45]  S. M. Fall,et al.  Dynamical Evolution of the Mass Function of Globular Star Clusters , 2001, astro-ph/0107298.

[46]  Hyun-chul Lee,et al.  The Hβ Index as an Age Indicator of Old Stellar Systems: The Effects of Horizontal-Branch Stars , 2000, astro-ph/0004247.

[47]  Bulge Globular Clusters in Spiral Galaxies , 2001, astro-ph/0106459.

[48]  Paolo Ventura,et al.  Predictions for Self-Pollution in Globular Cluster Stars , 2001 .

[49]  Evolutionary Stellar Population Synthesis at 2 Å Spectral Resolution , 1999 .

[50]  John P. Huchra,et al.  Extragalactic globular clusters. II, The M31 globular cluster system , 1991 .

[51]  K. Freeman,et al.  The cyanogen distribution of the giants in 47 Tucanae. , 1979 .

[52]  THE GLOBULAR CLUSTER SYSTEM OF THE CANIS MAJOR DWARF GALAXY , 2004, astro-ph/0403136.

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

[54]  L. Ho,et al.  Deep Photometry in a Remote M31 Major-Axis Field Near G1 , 2003, astro-ph/0309296.

[55]  R. G. Gratton,et al.  The O-Na and Mg-Al anticorrelations in turn-off and early subgiants in globular clusters , 2001 .

[56]  Spain.,et al.  Differences in carbon and nitrogen abundances between field and cluster early - type galaxies , 2003, astro-ph/0305244.

[57]  S. Holland.  The Distance to the M31 Globular Cluster System , 1998, astro-ph/9802088.

[58]  N. B. Suntzeff,et al.  The Globular Cluster Systems of the Sculptor Group , 1999 .

[59]  Galactic halo stars in phase space: a hint of satellite accretion? , 2003, astro-ph/0301596.

[60]  The local group of galaxies , 1999, astro-ph/9908050.

[61]  Michael J. West,et al.  The globular cluster system of the Galaxy. III: measurements of radial velocity and metallicity for 60 clusters and a compilation of metallicities for 121 clusters , 1984 .

[62]  J. Rose,et al.  Analyzing Starbursts Using Magellanic Cloud Star Clusters as Simple Stellar Populations , 2003, astro-ph/0306358.

[63]  S. M. Fall,et al.  The Structure of Young Star Clusters in the Large Magellanic Cloud , 1987 .

[64]  N. Suntzeff.  Carbon and nitrogen abundances in the giant stars of the globular clusters M3 and M13 , 1981 .

[65]  J. Huchra,et al.  Extragalactic globular clusters. I, The metallicity calibration , 1990 .

[66]  D. Geisler,et al.  Ages and metallicities of eight star clusters and their surrounding fields in the inner disc of the Large Magellanic Cloud , 2003 .

[67]  Stephen Holland,et al.  Deep HST V- and I-Band Observations of the Halo of M31: Evidence for Multiple Stellar Populations , 1996 .

[68]  R. Pelló,et al.  STELIB: A library of stellar spectra at R 2000 ?;?? , 2003, astro-ph/0302334.

[69]  K. Freeman,et al.  The New Galaxy: Signatures of Its Formation , 2002, astro-ph/0208106.

[70]  R. Proctor,et al.  Ages and metallicities of Hickson compact group galaxies , 2004, astro-ph/0401096.

[71]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[72]  J. Mathis,et al.  The relationship between infrared, optical, and ultraviolet extinction , 1989 .

[73]  L. Searle,et al.  A classification of star clusters in the Magellanic Clouds. , 1980 .

[74]  P. Hodge,et al.  The Large Magellanic Cloud , 1967 .

[75]  J. Rose,et al.  Constraints on stellar populations in elliptical galaxies. , 1985 .

[76]  D. Forbes,et al.  Keck spectroscopy and imaging of globular clusters in the lenticular galaxy NGC 524 , 2003, astro-ph/0312354.

[77]  S. White,et al.  The form of the galactic globular cluster system and the distance to the Galactic Centre , 1982 .

[78]  P. Côté.  Kinematics of the Galactic Globular Cluster System: New Radial Velocities for Clusters in the Direction of the Inner Galaxy , 1999, astro-ph/9906465.

[79]  Russell D. Cannon,et al.  Carbon and nitrogen abundance variations on the main sequence of 47 Tucanae , 1998 .

[80]  Garching,et al.  Stellar population models of Lick indices with variable element abundance ratios , 2003 .

[81]  Paul Goudfrooij,et al.  Hubble Space Telescope observations of globular cluster systems along the Hubble sequence of spiral galaxies , 2003, astro-ph/0304195.

[82]  R. P. Kraft.  ABUNDANCE DIFFERENCES AMONG GLOBULAR CLUSTER GIANTS: PRIMORDIAL VS. EVOLUTIONARY SCENARIOS , 1994 .

[83]  M. Steinmetz,et al.  Simulations of Galaxy Formation in a Λ Cold Dark Matter Universe. I. Dynamical and Photometric Properties of a Simulated Disk Galaxy , 2002, astro-ph/0211331.

[84]  Harland W. Epps,et al.  THE KECK LOW-RESOLUTION IMAGING SPECTROMETER , 1995 .

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

[86]  S. Kent.  An improved bulge model for M31 , 1989 .

[87]  J. Clariá,et al.  Bar star clusters in the LMC : formation history from UBV integrated photometry , 1992 .

[88]  Ucla,et al.  The Andromeda project - I. Deep HST-WFPC2 V, I photometry of 16 fields toward the disk and the halo of the M 31 galaxy. Probing the stellar content and metallicity distribution , 2002, astro-ph/0212531.

[89]  H. Kuntschner,et al.  VLT spectroscopy of NGC 3115 globular clusters , 2002, astro-ph/0209129.

[90]  W. Sargent,et al.  An Improved Mass Determination for M31 from Its Satellite Galaxies , 2000 .

[91]  Judith G. Cohen,et al.  Carbon and Nitrogen Abundances in Stars at the Base of the Red Giant Branch in M5 , 2001, astro-ph/0112199.

[92]  S. Larsen,et al.  Keck Spectroscopy of Young and Old Star Clusters in NGC 1023 , 2001, astro-ph/0111542.

[93]  M. Rieke,et al.  Integrated Ultraviolet Spectra and Line Indices of M31 Globular Clusters and the Cores of Elliptical Galaxies , 1998 .

[94]  J. Hunter,et al.  On the mass of M31 , 2002, astro-ph/0207450.

[95]  The stellar populations of spiral galaxies , 1999, astro-ph/9909402.

[96]  E. Grebel,et al.  CN Abundance Variations on the Main Sequence of 47 Tucanae , 2002, astro-ph/0210364.

[97]  J. Mould,et al.  The globular clusters of the dwarf elliptical galaxies NGC 147, NGC 185, and NGC 205. I: Abundances , 1988 .

[98]  J. P. Huchra,et al.  M31 Globular Clusters: Colors and Metallicities* ** *** , 2000 .

[99]  Metal-Poor Globular Clusters and Galaxy Formation , 2004, astro-ph/0403160.

[100]  D. Geisler,et al.  Young star clusters immersed in intermediate-age fields in the Large Magellanic Cloud bar , 2003 .

[101]  W. Saslaw.  THE DYNAMICS OF DENSE STELLAR SYSTEMS , 1973 .

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

[103]  R. Sharples,et al.  Ages and Metallicities of Globular Clusters in NGC 4472 , 2000, astro-ph/0007063.