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Title: THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES

Abstract

We present a spectroscopic analysis of the metallicities, ages, and alpha-elements of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo Cluster. Line indices of the GCs are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph on the Subaru 8.2 m Telescope. We derive [Fe/H] values of 59 GCs based on the Brodie and Huchra method, and [Z/H], age, and [{alpha}/Fe] values of 33 GCs from the comparison of the Lick line indices with single stellar population models. The metallicity distribution of NGC 4636 GCs shows a hint of a bimodality with two peaks at [Fe/H] = -1.23({sigma} = 0.32) and -0.35({sigma} = 0.19). The age spread is large from 2 Gyr to 15 Gyr and the fraction of young GCs with age <5 Gyr is about 27%. The [{alpha}/Fe] of the GCs shows a broad distribution with a mean value [{alpha}/Fe] Almost-Equal-To 0.14 dex. The dependence of these chemical properties on the galactocentric radius is weak. We also derive the metallicities, ages, and [{alpha}/Fe] values for the GCs in other nearby gEs (M87, M49, M60, NGC 5128, NGC 1399, and NGC 1407) from the line index data in themore » literature using the same methods as used for NGC 4636 GCs. The metallicity distribution of GCs in the combined sample of seven gEs including NGC 4636 is found to be bimodal, supported by the KMM test with a significance level of >99.9%. All these gEs harbor some young GCs with ages less than 5 Gyr. The mean age of the metal-rich GCs ([Fe/H] >-0.9) is about 3 Gyr younger than that of the metal-poor GCs. The mean value of [{alpha}/Fe] of the gE GCs is smaller than that of the Milky Way GCs. We discuss these results in the context of GC formation in gEs.« less

Authors:
;  [1];  [2];  [3]; ;  [4];  [5];  [6]
  1. Astronomy Program, Department of Physics and Astronomy, Seoul National University (Korea, Republic of)
  2. Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)
  4. National Astronomical Observatory of Japan, Tokyo (Japan)
  5. Kavli Institute for Physics and Mathematics of the Universe, University of Tokyo, Kashiwa City 277-8583 (Japan)
  6. Institute for Astronomy, ETH Zuerich, Wolfgang-Pauli-strasse 27, 8093 Zuerich (Switzerland)
Publication Date:
OSTI Identifier:
22086397
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; CAMERAS; CHEMICAL PROPERTIES; COMPARATIVE EVALUATIONS; ELEMENT ABUNDANCE; EMISSION SPECTRA; HYDROGEN; INDEXES; IRON; MILKY WAY; SPATIAL DISTRIBUTION; STAR CLUSTERS; TELESCOPES

Citation Formats

Park, Hong Soo, Lee, Myung Gyoon, Hwang, Ho Seong, Kim, Sang Chul, Arimoto, Nobuo, Yamada, Yoshihiko, Tamura, Naoyuki, and Onodera, Masato, E-mail: hspark@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr, E-mail: hhwang@cfa.harvard.edu, E-mail: sckim@kasi.re.kr, E-mail: arimoto.n@nao.ac.jp, E-mail: yoshihiko.yamada@nao.ac.jp, E-mail: naoyuki.tamura@ipmu.jp, E-mail: monodera@phys.ethz.ch. THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/116.
Park, Hong Soo, Lee, Myung Gyoon, Hwang, Ho Seong, Kim, Sang Chul, Arimoto, Nobuo, Yamada, Yoshihiko, Tamura, Naoyuki, & Onodera, Masato, E-mail: hspark@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr, E-mail: hhwang@cfa.harvard.edu, E-mail: sckim@kasi.re.kr, E-mail: arimoto.n@nao.ac.jp, E-mail: yoshihiko.yamada@nao.ac.jp, E-mail: naoyuki.tamura@ipmu.jp, E-mail: monodera@phys.ethz.ch. THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES. United States. doi:10.1088/0004-637X/759/2/116.
Park, Hong Soo, Lee, Myung Gyoon, Hwang, Ho Seong, Kim, Sang Chul, Arimoto, Nobuo, Yamada, Yoshihiko, Tamura, Naoyuki, and Onodera, Masato, E-mail: hspark@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr, E-mail: hhwang@cfa.harvard.edu, E-mail: sckim@kasi.re.kr, E-mail: arimoto.n@nao.ac.jp, E-mail: yoshihiko.yamada@nao.ac.jp, E-mail: naoyuki.tamura@ipmu.jp, E-mail: monodera@phys.ethz.ch. Sat . "THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES". United States. doi:10.1088/0004-637X/759/2/116.
@article{osti_22086397,
title = {THE GLOBULAR CLUSTER SYSTEM OF NGC 4636 AND FORMATION OF GLOBULAR CLUSTERS IN GIANT ELLIPTICAL GALAXIES},
author = {Park, Hong Soo and Lee, Myung Gyoon and Hwang, Ho Seong and Kim, Sang Chul and Arimoto, Nobuo and Yamada, Yoshihiko and Tamura, Naoyuki and Onodera, Masato, E-mail: hspark@astro.snu.ac.kr, E-mail: mglee@astro.snu.ac.kr, E-mail: hhwang@cfa.harvard.edu, E-mail: sckim@kasi.re.kr, E-mail: arimoto.n@nao.ac.jp, E-mail: yoshihiko.yamada@nao.ac.jp, E-mail: naoyuki.tamura@ipmu.jp, E-mail: monodera@phys.ethz.ch},
abstractNote = {We present a spectroscopic analysis of the metallicities, ages, and alpha-elements of the globular clusters (GCs) in the giant elliptical galaxy (gE) NGC 4636 in the Virgo Cluster. Line indices of the GCs are measured from the integrated spectra obtained with Faint Object Camera and Spectrograph on the Subaru 8.2 m Telescope. We derive [Fe/H] values of 59 GCs based on the Brodie and Huchra method, and [Z/H], age, and [{alpha}/Fe] values of 33 GCs from the comparison of the Lick line indices with single stellar population models. The metallicity distribution of NGC 4636 GCs shows a hint of a bimodality with two peaks at [Fe/H] = -1.23({sigma} = 0.32) and -0.35({sigma} = 0.19). The age spread is large from 2 Gyr to 15 Gyr and the fraction of young GCs with age <5 Gyr is about 27%. The [{alpha}/Fe] of the GCs shows a broad distribution with a mean value [{alpha}/Fe] Almost-Equal-To 0.14 dex. The dependence of these chemical properties on the galactocentric radius is weak. We also derive the metallicities, ages, and [{alpha}/Fe] values for the GCs in other nearby gEs (M87, M49, M60, NGC 5128, NGC 1399, and NGC 1407) from the line index data in the literature using the same methods as used for NGC 4636 GCs. The metallicity distribution of GCs in the combined sample of seven gEs including NGC 4636 is found to be bimodal, supported by the KMM test with a significance level of >99.9%. All these gEs harbor some young GCs with ages less than 5 Gyr. The mean age of the metal-rich GCs ([Fe/H] >-0.9) is about 3 Gyr younger than that of the metal-poor GCs. The mean value of [{alpha}/Fe] of the gE GCs is smaller than that of the Milky Way GCs. We discuss these results in the context of GC formation in gEs.},
doi = {10.1088/0004-637X/759/2/116},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}