J/AJ/159/254 Parameters for 453 metal-poor stars in NGC5139 (Johnson+, 2020)
The most metal-poor stars in Omega Centauri (NGC5139).
Johnson C.I., Dupree A.K., Mateo M., Bailey J.I., Olszewski E.W.,
Walker M.G.
<Astron. J., 159, 254 (2020)>
=2020AJ....159..254J 2020AJ....159..254J
ADC_Keywords: Clusters, globular; Stars, metal-deficient; Spectra, optical;
Spectra, infrared; Abundances, [Fe/H]; Radial velocities
Keywords: Globular star clusters ; Population II stars ; Chemical abundances ;
Metallicity
Abstract:
The most massive and complex globular clusters in the Galaxy are
thought to have originated as the nuclear cores of now tidally
disrupted dwarf galaxies, but the connection between globular clusters
and dwarf galaxies is tenuous with the M54/Sagittarius system
representing the only unambiguous link. The globular cluster Omega
Centauri (ωCen) is more massive and chemically diverse than M54,
and is thought to have been the nuclear star cluster of either the
Sequoia or Gaia-Enceladus galaxy. Local Group dwarf galaxies with
masses equivalent to these systems often host significant populations
of very metal-poor stars ([Fe/H]←2.5), and one might expect to find
such objects in ωCen. Using high-resolution spectra from
Magellan-M2FS, we detected 11 stars in a targeted sample of 395 that
have [Fe/H] ranging from -2.30 to -2.52. These are the most metal-poor
stars discovered in the cluster, and are five times more metal-poor
than ωCen's dominant population. However, these stars are not so
metal-poor as to be unambiguously linked to a dwarf galaxy origin. The
cluster's metal-poor tail appears to contain two populations near
[Fe/H]~-2.1 and -2.4, which are very centrally concentrated but do not
exhibit any peculiar kinematic signatures. Several possible origins
for these stars are discussed.
Description:
All spectroscopic data for this project were obtained using the
Michigan-Magellan Fiber System (M2FS) and MSpec spectrograph mounted
on the Magellan-Clay 6.5m telescope at Las Campanas Observatory. The
spectra were acquired in three runs via the M2FS queue that spanned
2015 February 19, 21, 22, 23, and 25 for the first set, 2015 March 1,
2, and 4 for the second set, and 2015 July 18 and 20 for the third
set.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 90 453 Sky coordinates, photometry, model atmosphere
parameters, iron abundances, errors, and radial
Velocities
--------------------------------------------------------------------------------
See also:
II/358 : SkyMapper Southern Sky Survey. DR1.1 (Wolf+, 2018)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/462/241 : Ca abundance for Omega Cen red giants (Norris+ 1996)
J/A+A/360/472 : Proper motions in omega Centauri (van Leeuwen+, 2000)
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/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/A+A/445/503 : Radial velocities in Omega Cen (NGC5139) (Reijns+, 2006)
J/A+A/465/357 : Stroemgren photometry in the Draco dSph galaxy (Faria+,2007)
J/MNRAS/382/1353 : Spectral atlas of omega Cen post-MS stars (van Loon+, 2007)
J/ApJ/663/296 : UBV phot. omega Cen (NGC5139) subgiants (Villanova+, 2007)
J/AJ/136/1039 : CaII index of SMC red giant branch stars (Carrera+, 2008)
J/ApJ/681/1505 : Abundances of red giants in ω Cen (Johnson+, 2008)
J/ApJ/706/1277 : Stromgren photometry in ω Cen (Calamida+, 2009)
J/MNRAS/396/1075 : Globular cluster nearby dwarf galaxies. II (Georgiev+, 2009)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/MNRAS/396/2183 : Radial velocities red giants in ωCen (Sollima+, 2009)
J/AJ/140/631 : HST WFC3/UVIS photometry of omega Cen core (Bellini+, 2010)
J/A+A/520/A95 : Abundances of red giants in M54 & Sgr dSph (Carretta+, 2010)
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/A+A/534/A53 : Equivalent widths of 18 subgiant ωCen (Pancino+, 2011)
J/A+A/527/A18 : EW of 6 subgiants of ω Cen (Pancino+, 2011)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/A+A/572/A82 : Abundances in outer parts of Fornax dSph (Hendricks+, 2014)
J/ApJ/795/22 : Iron abundance of Terzan 5 stars (Massari+, 2014)
J/ApJ/791/107 : Parameters of NGC 5139 SGBs stars (Villanova+, 2014)
J/MNRAS/450/815 : Red giants in NGC 5286 (Marino+, 2015)
J/ApJ/819/103 : Abundances of two very metal-poor stars (Afsar+, 2016)
J/AJ/154/150 : Spectroscopy of RGB stars in ω Centauri (An+, 2017)
J/ApJ/844/164 : HST astro-photo. analysis of NGC5139. III. (Bellini+, 2017)
J/ApJ/836/168 : Abundances & RVs for stars near NGC6273 (Johnson+, 2017)
J/MNRAS/466/2006 : Phoenix dwarf galaxy RV and [Fe/H] catalog (Kacharov+, 2017)
J/A+A/618/A134 : Omega Cen lower red giant stars abund. (Mucciarelli+, 2018)
J/ApJS/245/5 : Globular cluster intrinsic iron abund. spreads (Bailin,2019)
J/ApJ/870/115 : Reddening, dist. modulus & Fe/H of RRLs in wCen (Bono+,2019)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Leid [4013/98012] Leid identification
(Cl* NGC 5139 Leid NNNNN)
7- 15 F9.5 deg RAdeg [201.07/202.04] Degree of right ascension (J2000)
17- 25 F9.5 deg DEdeg [-47.9/-47.18] Degree of declination (J2000)
27- 32 F6.3 mag Vmag [11.9/14.7] Visual magnitude
34- 39 F6.3 mag Jmag [10.1/13.2]? J band magnitude
41- 46 F6.3 mag Ksmag [9.35/12.8]? Ks band magnitude
48- 51 I4 K Teff [4282/5822]? Effective temperature
53- 56 F4.2 cm/s2 logg [1.1/2.56]? Surface gravity
58- 62 F5.2 [-] [Fe/H] [-2.52/-0.81]? Metallicity
64- 67 F4.2 km/s ksi [0.9/1.89]? Microturbulence velocity (ξmic)
69- 72 F4.2 --- S/N [0.01/0.09]? Signal to noise ratio (σ/sqrtN)
74- 75 I2 --- Nobs [4/14]? Number of observations
77- 80 F4.2 [-] e_[Fe/H] [0.11/0.16]? Error on [Fe/H] (Δ[Fe/H])
82- 86 F5.1 km/s RVel [186/272] Heliocentric radial velocity
88- 90 F3.1 km/s e_RVel [0.1/6.1] Error on RVel
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 29-Sep-2020