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Title: The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations

Abstract

We present a multi-band photometric catalog of ≈1.7 million cluster members for a field of view of ≈2° × 2° across ω Cen. Photometry is based on images collected with the Dark Energy Camera on the 4 m Blanco telescope and the Advanced Camera for Surveys on the Hubble Space Telescope . The unprecedented photometric accuracy and field coverage allowed us, for the first time, to investigate the spatial distribution of ω Cen multiple populations from the core to the tidal radius, confirming its very complex structure. We found that the frequency of blue main-sequence stars is increasing compared to red main-sequence stars starting from a distance of ≈25′ from the cluster center. Blue main-sequence stars also show a clumpy spatial distribution, with an excess in the northeast quadrant of the cluster pointing toward the direction of the Galactic center. Stars belonging to the reddest and faintest red-giant branch also show a more extended spatial distribution in the outskirts of ω Cen, a region never explored before. Both these stellar sub-populations, according to spectroscopic measurements, are more metal-rich compared to the cluster main stellar population. These findings, once confirmed, make ω Cen the only stellar system currently known where metal-rich stars havemore » a more extended spatial distribution compared to metal-poor stars. Kinematic and chemical abundance measurements are now needed for stars in the external regions of ω Cen to better characterize the properties of these sub-populations.« less

Authors:
;  [1]; ;  [2]; ; ;  [3];  [4]; ; ;  [5]
  1. National Optical Astronomy Observatory—AURA, 950 N Cherry Avenue, Tucson, AZ, 85719 (United States)
  2. Space Telescope Science Institute—AURA, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  3. INAF—Osservatorio Astronomico di Roma—Via Frascati 33, I-00040, Monteporzio Catone, Rome (Italy)
  4. The University of Chicago, The Kavli Institute for Cosmological Physics, William Eckhardt Research Center—Suite 499, 5640 South Ellis Avenue, Chicago, IL 60637 (United States)
  5. Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)
Publication Date:
OSTI Identifier:
22663722
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (Online); Journal Volume: 153; Journal Issue: 4; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; ACCURACY; CAMERAS; CATALOGS; COMPARATIVE EVALUATIONS; IMAGES; MAIN SEQUENCE STARS; METALS; NONLUMINOUS MATTER; PHOTOMETRY; SPACE; SPATIAL DISTRIBUTION; STAR CLUSTERS; TELESCOPES

Citation Formats

Calamida, A., Saha, A., Strampelli, G., Rest, A., Bono, G., Ferraro, I., Iannicola, G., Scolnic, D., James, D., Smith, C., and Zenteno, A., E-mail: calamida@noao.edu. The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations. United States: N. p., 2017. Web. doi:10.3847/1538-3881/AA6397.
Calamida, A., Saha, A., Strampelli, G., Rest, A., Bono, G., Ferraro, I., Iannicola, G., Scolnic, D., James, D., Smith, C., & Zenteno, A., E-mail: calamida@noao.edu. The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations. United States. doi:10.3847/1538-3881/AA6397.
Calamida, A., Saha, A., Strampelli, G., Rest, A., Bono, G., Ferraro, I., Iannicola, G., Scolnic, D., James, D., Smith, C., and Zenteno, A., E-mail: calamida@noao.edu. Sat . "The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations". United States. doi:10.3847/1538-3881/AA6397.
@article{osti_22663722,
title = {The Not So Simple Globular Cluster ω Cen. I. Spatial Distribution of the Multiple Stellar Populations},
author = {Calamida, A. and Saha, A. and Strampelli, G. and Rest, A. and Bono, G. and Ferraro, I. and Iannicola, G. and Scolnic, D. and James, D. and Smith, C. and Zenteno, A., E-mail: calamida@noao.edu},
abstractNote = {We present a multi-band photometric catalog of ≈1.7 million cluster members for a field of view of ≈2° × 2° across ω Cen. Photometry is based on images collected with the Dark Energy Camera on the 4 m Blanco telescope and the Advanced Camera for Surveys on the Hubble Space Telescope . The unprecedented photometric accuracy and field coverage allowed us, for the first time, to investigate the spatial distribution of ω Cen multiple populations from the core to the tidal radius, confirming its very complex structure. We found that the frequency of blue main-sequence stars is increasing compared to red main-sequence stars starting from a distance of ≈25′ from the cluster center. Blue main-sequence stars also show a clumpy spatial distribution, with an excess in the northeast quadrant of the cluster pointing toward the direction of the Galactic center. Stars belonging to the reddest and faintest red-giant branch also show a more extended spatial distribution in the outskirts of ω Cen, a region never explored before. Both these stellar sub-populations, according to spectroscopic measurements, are more metal-rich compared to the cluster main stellar population. These findings, once confirmed, make ω Cen the only stellar system currently known where metal-rich stars have a more extended spatial distribution compared to metal-poor stars. Kinematic and chemical abundance measurements are now needed for stars in the external regions of ω Cen to better characterize the properties of these sub-populations.},
doi = {10.3847/1538-3881/AA6397},
journal = {Astronomical Journal (Online)},
number = 4,
volume = 153,
place = {United States},
year = {Sat Apr 01 00:00:00 EDT 2017},
month = {Sat Apr 01 00:00:00 EDT 2017}
}
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