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. V. NONLINEAR ABSORPTION-LINE INDEX VERSUS METALLICITY RELATIONS AND BIMODAL INDEX DISTRIBUTIONS OF M31 GLOBULAR CLUSTERS

Abstract

Recent spectroscopy on the globular cluster (GC) system of M31 with unprecedented precision witnessed a clear bimodality in absorption-line index distributions of old GCs. Such division of extragalactic GCs, so far asserted mainly by photometric color bimodality, has been viewed as the presence of merely two distinct metallicity subgroups within individual galaxies and forms a critical backbone of various galaxy formation theories. Given that spectroscopy is a more detailed probe into stellar population than photometry, the discovery of index bimodality may point to the very existence of dual GC populations. However, here we show that the observed spectroscopic dichotomy of M31 GCs emerges due to the nonlinear nature of metallicity-to-index conversion and thus one does not necessarily have to invoke two separate GC subsystems. We take this as a close analogy to the recent view that metallicity-color nonlinearity is primarily responsible for observed GC color bimodality. We also demonstrate that the metallicity-sensitive magnesium line displays non-negligible metallicity-index nonlinearity and Balmer lines show rather strong nonlinearity. This gives rise to bimodal index distributions, which are routinely interpreted as bimodal metallicity distributions, not considering metallicity-index nonlinearity. Our findings give a new insight into the constitution of M31's GC system, which could changemore » much of the current thought on the formation of GC systems and their host galaxies.« less

Authors:
; ; ;  [1];  [2];  [3]; ;  [4]
  1. Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of)
  2. Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
  3. Gemini Observatory, 670 North A'ohoku Place, Hilo, HI 96720 (United States)
  4. Department of Astronomy and Space Science, Chungnam University, Daejeon (Korea, Republic of)
Publication Date:
OSTI Identifier:
22126725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 768; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ACCURACY; BALMER LINES; COLOR; CONVERSION; DISTRIBUTION; EVOLUTION; GALAXIES; HOST; MAGNESIUM; NONLINEAR PROBLEMS; PHOTOMETRY; PROBES; SPECTROSCOPY; STAR CLUSTERS

Citation Formats

Kim, Sooyoung, Yoon, Suk-Jin, Chung, Chul, Lee, Young-Wook, Caldwell, Nelson, Schiavon, Ricardo P., Kang, Yongbeom, and Rey, Soo-Chang, E-mail: sjyoon@galaxy.yonsei.ac.kr. NONLINEAR COLOR-METALLICITY RELATIONS OF GLOBULAR CLUSTERS. V. NONLINEAR ABSORPTION-LINE INDEX VERSUS METALLICITY RELATIONS AND BIMODAL INDEX DISTRIBUTIONS OF M31 GLOBULAR CLUSTERS. United States: N. p., 2013. Web. doi:10.1088/0004-637X/768/2/138.
Kim, Sooyoung, Yoon, Suk-Jin, Chung, Chul, Lee, Young-Wook, Caldwell, Nelson, Schiavon, Ricardo P., Kang, Yongbeom, & Rey, Soo-Chang, E-mail: sjyoon@galaxy.yonsei.ac.kr. NONLINEAR COLOR-METALLICITY RELATIONS OF GLOBULAR CLUSTERS. V. NONLINEAR ABSORPTION-LINE INDEX VERSUS METALLICITY RELATIONS AND BIMODAL INDEX DISTRIBUTIONS OF M31 GLOBULAR CLUSTERS. United States. doi:10.1088/0004-637X/768/2/138.
Kim, Sooyoung, Yoon, Suk-Jin, Chung, Chul, Lee, Young-Wook, Caldwell, Nelson, Schiavon, Ricardo P., Kang, Yongbeom, and Rey, Soo-Chang, E-mail: sjyoon@galaxy.yonsei.ac.kr. Fri . "NONLINEAR COLOR-METALLICITY RELATIONS OF GLOBULAR CLUSTERS. V. NONLINEAR ABSORPTION-LINE INDEX VERSUS METALLICITY RELATIONS AND BIMODAL INDEX DISTRIBUTIONS OF M31 GLOBULAR CLUSTERS". United States. doi:10.1088/0004-637X/768/2/138.
@article{osti_22126725,
title = {NONLINEAR COLOR-METALLICITY RELATIONS OF GLOBULAR CLUSTERS. V. NONLINEAR ABSORPTION-LINE INDEX VERSUS METALLICITY RELATIONS AND BIMODAL INDEX DISTRIBUTIONS OF M31 GLOBULAR CLUSTERS},
author = {Kim, Sooyoung and Yoon, Suk-Jin and Chung, Chul and Lee, Young-Wook and Caldwell, Nelson and Schiavon, Ricardo P. and Kang, Yongbeom and Rey, Soo-Chang, E-mail: sjyoon@galaxy.yonsei.ac.kr},
abstractNote = {Recent spectroscopy on the globular cluster (GC) system of M31 with unprecedented precision witnessed a clear bimodality in absorption-line index distributions of old GCs. Such division of extragalactic GCs, so far asserted mainly by photometric color bimodality, has been viewed as the presence of merely two distinct metallicity subgroups within individual galaxies and forms a critical backbone of various galaxy formation theories. Given that spectroscopy is a more detailed probe into stellar population than photometry, the discovery of index bimodality may point to the very existence of dual GC populations. However, here we show that the observed spectroscopic dichotomy of M31 GCs emerges due to the nonlinear nature of metallicity-to-index conversion and thus one does not necessarily have to invoke two separate GC subsystems. We take this as a close analogy to the recent view that metallicity-color nonlinearity is primarily responsible for observed GC color bimodality. We also demonstrate that the metallicity-sensitive magnesium line displays non-negligible metallicity-index nonlinearity and Balmer lines show rather strong nonlinearity. This gives rise to bimodal index distributions, which are routinely interpreted as bimodal metallicity distributions, not considering metallicity-index nonlinearity. Our findings give a new insight into the constitution of M31's GC system, which could change much of the current thought on the formation of GC systems and their host galaxies.},
doi = {10.1088/0004-637X/768/2/138},
journal = {Astrophysical Journal},
number = 2,
volume = 768,
place = {United States},
year = {Fri May 10 00:00:00 EDT 2013},
month = {Fri May 10 00:00:00 EDT 2013}
}