J/AJ/154/150 Spectroscopy of RGB stars in ω Centauri (An+, 2017)
Medium-resolution spectroscopy of red giant branch stars in ω Centauri.
An D., Lee Y.S., Jung J.In, Rey S.-C., Rhee J., Lee J.-W., Lee Y.-W.,
Joe Y.H.
<Astron. J., 154, 150 (2017)>
=2017AJ....154..150A 2017AJ....154..150A (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, giant ; Spectroscopy ; Abundances ;
Effective temperatures ; Radial velocities
Keywords: globular clusters: individual (omega Centauri) - stars: abundances
Abstract:
We present [Fe/H] and [Ca/Fe] of ∼600 red giant branch (RGB) members
of the globular cluster Omega Centauri (ω Cen). We collect
medium-resolution (R∼2000) spectra using the Blanco 4 m telescope at
the Cerro Tololo Inter-American Observatory equipped with Hydra, the
fiber-fed multi-object spectrograph. We demonstrate that blending of
stellar light in optical fibers severely limits the accuracy of
spectroscopic parameters in the crowded central region of the cluster.
When photometric temperatures are taken in the spectroscopic analysis,
our kinematically selected cluster members, excluding those that are
strongly affected by flux from neighboring stars, include relatively
fewer stars at intermediate metallicity ([Fe/H]~-1.5) than seen in
the previous high-resolution survey for brighter giants in
Johnson & Pilachowski (2010, J/ApJ/722/1373). As opposed to the trend
of increasing [Ca/Fe] with [Fe/H] found by those authors, our [Ca/Fe]
estimates, based on Ca II H & K measurements, show essentially the
same mean [Ca/Fe] for most of the metal-poor and metal-intermediate
populations in this cluster, suggesting that mass- or metallicity-dependent
SN II yields may not be necessary in their proposed chemical evolution
scenario. Metal-rich cluster members in our sample show a large spread
in [Ca/Fe], and do not exhibit a clear bimodal distribution in [Ca/Fe].
We also do not find convincing evidence for a radial metallicity
gradient among RGB stars in ω Cen.
Description:
We selected spectroscopic targets among RGB stars in ω Cen based
on a BV color-magnitude diagram (CMD) of Rey et al. (2004, J/AJ/127/958).
We collected medium-resolution spectra using the Blanco 4 m telescope
equipped with Hydra at the Cerro Tololo Inter-American Observatory (CTIO).
The Hydra is a fiber-fed multi-object spectrograph with 138 large optical
fibers, each of which has a ∼300 µm diameter or a ∼2" aperture on a
focal plane. We observed ω Cen in 11 different fiber configurations
on UT 2005 May 27 and 28.
In this study, we present spectroscopic parameters of 712 stars
(including cluster non-members) for which there exist at least one
spectrum, with a signal-to-noise ratio (S/N) equal to or greater than
52 per resolution elements at 4500=<λ(Å)=<5500.
Objects:
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RA (ICRS) DE Designation(s)
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13 26 47.28 -47 28 46.1 omega Centauri = NGC 5139
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 108 712 Spectroscopic Properties of Stars in ω Cen
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See also:
J/ApJ/462/241 : Ca abundance for Omega Cen red giants (Norris+ 1996)
J/AJ/127/958 : CCD BV photometry on Omega Cen (Rey+, 2004)
J/MNRAS/357/265 : BVI photometry of omega Cen red giants (Sollima+, 2005)
J/ApJ/661/L155 : Radial velocities RGB stars in omega Cen (Pancino+, 2007)
J/ApJ/681/1505 : Abundances of red giants in ω Cen (Johnson+, 2008)
J/MNRAS/396/2183 : Radial velocities of red giants in ω Cen
(Sollima+ 2009)
J/ApJ/722/1373 : ω Centauri giants abundances (Johnson+, 2010)
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/MNRAS/416/L6 : AGB and RGB stars in ω Cen (McDonald+, 2011)
J/MNRAS/427/1153 : Stellar parameters of giants in ω Cen (Simpson+, 2012)
J/MNRAS/433/1892 : Abundances of 848 giants of ω Cen (Simpson+, 2013)
J/ApJ/837/176 : Spectroscopic obs. of 2 red giant stars in omega Cen
(Yong+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/712] Sequential running star identifier
5- 6 I2 h RAh Hour of Right Ascension (J2000)
8- 9 I2 min RAm Minute of Right Ascension (J2000)
11- 15 F5.2 s RAs Second of Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18- 19 I2 deg DEd Degree of Declination (J2000)
21- 22 I2 arcmin DEm Arcminute of Declination (J2000)
24- 28 F5.2 arcsec DEs Arcsecond of Declination (J2000)
30- 35 F6.3 mag Vmag [14.201/14.998] V band magnitude from
Rey et al. 2004 (J/AJ/127/958)
37- 41 F5.3 mag B-V [0.802/1.281] B-V color from Rey et al. 2004
(J/AJ/127/958)
43- 46 I4 K Teff [4601/5410] Adjusted IRFM (Infrared Flux
Method) effective temperature
48- 50 I3 K e_Teff [0/107]?=-99 Uncertainty in Teff
53- 56 F4.2 [cm/s2] logg [0.5/4.04] Surface gravity
58- 62 F5.2 [cm/s2] e_logg [0/1.49]?=-9.99 Uncertainty in logg
64- 68 F5.2 [-] [Fe/H] [-2.28/0.21] Metallicity
70- 74 F5.2 [-] e_[Fe/H] [0/1.54]?=-9.99 Uncertainty in [Fe/H]
76- 80 F5.2 [-] [Ca/Fe] [-1.87/1.19] Calcium abundance
82- 86 F5.2 [-] e_[Ca/Fe] [0.01/0.72]?=-9.99 Uncertainty in [Ca/Fe]
88- 93 F6.1 km/s RV [-89.6/286.9]?=-999.9 Radial velocity
95- 98 F4.1 km/s e_RV [0/60.4]?=-9.9 Uncertainty in RV
100-104 F5.2 --- Fneighb [0/0.98]?=-9.99 Fractional contribution of
flux in B passband from neighboring stars
106 I1 --- Nobs [1/3] Number of spectra with S/N≥52
108 A1 --- Mem [mx] Cluster membership (1)
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Note (1): Cluster membership, based on radial velocities and proper motions, is
defined as follows:
m = Cluster member;
x = Non-member.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 10-Jul-2018