skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters

Abstract

Spectroscopy on the globular cluster (GC) system of NGC 5128 revealed bimodality in absorption-line index distributions of its old GCs. GC division is a widely observed and studied phenomenon whose interpretation has depicted host galaxy formation and evolution such that it harbors two distinct metallicity groups. Such a conventional view of GC bimodality has mainly been based on photometry. The recent GC photometric data, however, presented an alternative perspective in which the nonlinear metallicity-to-color transformation is responsible for color bimodality of GC systems. Here we apply the same line of analysis to the spectral indices and examine the absorption-line index versus metallicity relations for the NGC 5128 GC system. NGC 5128 GCs display nonlinearity in the metallicity-index planes, most prominently for the Balmer lines and by a non-negligible degree for the metallicity-sensitive magnesium line. We demonstrate that the observed spectroscopic division of NGC 5128 GCs can be caused by the nonlinear nature of the metallicity-to-index conversions and thus one does not need to resort to two separate GC subgroups. Our analysis incorporating this nonlinearity provides a new perspective on the structure of NGC 5128's GC system, and a further piece to the global picture of the formation of GC systemsmore » and their host galaxies.« less

Authors:
;  [1]
  1. Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22663446
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 843; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; BALMER LINES; COLOR; CONVERSION; DISTRIBUTION; GALACTIC EVOLUTION; GALAXIES; MAGNESIUM; METALLICITY; NONLINEAR PROBLEMS; PHOTOMETRY; SPECTROSCOPY; STAR CLUSTERS; STARS

Citation Formats

Kim, Sooyoung, and Yoon, Suk-Jin, E-mail: sjyoon0691@yonsei.ac.kr. Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA7387.
Kim, Sooyoung, & Yoon, Suk-Jin, E-mail: sjyoon0691@yonsei.ac.kr. Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters. United States. doi:10.3847/1538-4357/AA7387.
Kim, Sooyoung, and Yoon, Suk-Jin, E-mail: sjyoon0691@yonsei.ac.kr. Sat . "Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters". United States. doi:10.3847/1538-4357/AA7387.
@article{osti_22663446,
title = {Nonlinear Color–Metallicity Relations of Globular Clusters. VII. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of NGC 5128 Globular Clusters},
author = {Kim, Sooyoung and Yoon, Suk-Jin, E-mail: sjyoon0691@yonsei.ac.kr},
abstractNote = {Spectroscopy on the globular cluster (GC) system of NGC 5128 revealed bimodality in absorption-line index distributions of its old GCs. GC division is a widely observed and studied phenomenon whose interpretation has depicted host galaxy formation and evolution such that it harbors two distinct metallicity groups. Such a conventional view of GC bimodality has mainly been based on photometry. The recent GC photometric data, however, presented an alternative perspective in which the nonlinear metallicity-to-color transformation is responsible for color bimodality of GC systems. Here we apply the same line of analysis to the spectral indices and examine the absorption-line index versus metallicity relations for the NGC 5128 GC system. NGC 5128 GCs display nonlinearity in the metallicity-index planes, most prominently for the Balmer lines and by a non-negligible degree for the metallicity-sensitive magnesium line. We demonstrate that the observed spectroscopic division of NGC 5128 GCs can be caused by the nonlinear nature of the metallicity-to-index conversions and thus one does not need to resort to two separate GC subgroups. Our analysis incorporating this nonlinearity provides a new perspective on the structure of NGC 5128's GC system, and a further piece to the global picture of the formation of GC systems and their host galaxies.},
doi = {10.3847/1538-4357/AA7387},
journal = {Astrophysical Journal},
number = 1,
volume = 843,
place = {United States},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}
}