J/ApJ/832/99 HK', CN & CH chemical indexes in NGC 362 & NGC 6723 (Lim+, 2016)
Reversed trend of radial distribution of subpopulations in the globular clusters
NGC 362 and NGC 6723.
Lim D., Lee Y.-W., Pasquato M., Han S.-I., Roh D.-G.
<Astrophys. J., 832, 99-99 (2016)>
=2016ApJ...832...99L 2016ApJ...832...99L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Abundances ; Spectroscopy ; Photometry
Keywords: globular clusters: general; globular clusters: individual: (NGC 362,
NGC 6723); stars: abundances; stars: evolution
Abstract:
Most globular clusters (GCs) are now known to host multiple stellar
populations with different abundances of light elements. Here we use
narrow-band photometry and low-resolution spectroscopy for NGC 362 and
NGC 6723 to investigate their chemical properties and radial
distributions of subpopulations. We confirm that NGC 362 and NGC 6723
are among the GCs with multiple populations showing bimodal CN
distribution and CN-CH anticorrelation without a significant spread in
calcium abundance. These two GCs show more centrally concentrated
CN-weak, earlier generation stars compared to the CN-strong, later
generation stars. These trends are reversed with respect to those
found in previous studies for many other GCs. Our findings, therefore,
seem contradictory to the current scenario for the formation of
multiple stellar populations, but mass segregation acting on the two
subpopulations might be a possible solution to explain this reversed
radial trend.
Description:
Our photometry was obtained at the Cerro Tololo Inter-American
Observatory (CTIO) 4m Blanco telescope with a "Ca+CN" filter in 2009
July.
The spectroscopic data were obtained from Las Campanas Observatory
2.5m duPont telescope in 2011 July and 2014 June (central wavelength
of 3700Å).
Finally, we have obtained spectra for 35 stars in NGC 362, and 31
stars in NGC 6723, which are identified in Figures 1 and 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 112 66 Index measurements for the sample stars in
NGC 362 and NGC 6723
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See also:
J/ApJ/824/73 : Abundances of NGC 6362 member stars (Mucciarelli+, 2016)
J/ApJS/219/7 : Ca,by photometry in globular clusters. I. M22 (Lee, 2015)
J/ApJS/216/19 : Spectroscopic HK' index for 3 globular clusters (Lim+, 2015)
J/ApJ/804/71 : HST/WFC3 observations of stars in M15 (Larsen+, 2015)
J/MNRAS/449/4038 : Li abundance of giants in 3 GCs (D'Orazi+, 2015)
J/A+A/573/A92 : Horizontal branch stars in NGC 6723 (Gratton+, 2015)
J/A+A/557/A138 : Chemical abundances in the GlC NGC 362 (Carretta+ 2013)
J/ApJ/754/L38 : Abundances & radial velocities of M13 giants (Johnson+, 2012)
J/AJ/142/126 : CN & CH in SDSS Galactic globular clusters (Smolinski+, 2011)
J/A+A/533/A69 : Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)
J/A+A/524/A44 : CN and CH line strengths in 12 globulars (Pancino+, 2010)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/A+A/490/625 : Abundances of NGC 6121 red giants (Marino+, 2008)
J/A+A/486/437 : CN and CH line strengths in 8 Galactic GlCl (Kayser+, 2008)
J/A+A/463/589 : Variables stars in NGC 362 (Szekely+, 2007)
J/ApJ/643/680 : Imaging & spectroscopy around PKS 0405-123 (Prochaska+, 2006)
J/AJ/125/197 : CN abundances of the 47 Tuc main sequence (Harbeck+, 2003)
J/AJ/122/2569 : VI photometry of NGC 288, 362 and 1851 (Bellazzini+, 2001)
J/AJ/106/1508 : Dynamics of globular cluster NGC 362 (Fischer+ 1993)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Gal Galaxy identifier (N362 or N6723)
6 A1 --- --- [-]
7- 10 I4 --- ID [1003/4162] Star identifier within Gal
12- 20 F9.5 deg RAdeg Right Ascension in decimal degrees (J2000)
22- 30 F9.5 deg DEdeg Declination in decimal degrees (J2000)
32- 38 F7.4 mag ymag [13.6/17.5] The CTIO y band magnitude
40- 45 F6.4 --- hk-Ca+CN [0.5/1.3] The hkCa+CN index (1)
47- 52 F6.4 --- HK' [0.3/0.7] The HK' index (2)
54- 59 F6.4 --- e_HK' [0.01/0.06] Uncertainty in HK'
61- 67 F7.4 --- delHK' [-0.12/0.1] The delta HK' index (3)
69- 75 F7.4 --- CN [-0.5/0.5] The CN index (2)
77- 82 F6.4 --- e_CN [0.01/0.2] Uncertainty in CN
84- 90 F7.4 --- delCN [-0.4/0.4] The delta CN index (3)
92- 97 F6.4 --- CH [0.9/1.3] The CH index (2)
99-104 F6.4 --- e_CH [0.008/0.04] Uncertainty in CH
106-112 F7.4 --- delCH [-0.2/0.07] The delta CH index (3)
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Note (1): Where hk-Ca+CN=(Ca-b)-(b-y).
Note (2): These indices definitions are:
HK' = -2.5*log(F3916-3985/(2*F3894-3911+F3990-4025)),
CN = -2.5*log(F3861-3884/F3894-3910),
CH = -2.5*log(F4285-4315/(0.5*F4240-4280+0.5*F4390-4460)).
Note (3): The delta indices are the difference between the original index and
the least squares fitting of the full sample in a globular cluster.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 20-Feb-2017