J/ApJ/726/L20 Spectroscopy of Terzan 5 (Origlia+, 2011)
Spectroscopy unveils the complex nature of Terzan 5.
Origlia L., Rich R.M., Ferraro F.R., Lanzoni B., Bellazzini M.,
Dalessandro E., Mucciarelli A., Valenti E., Beccari G.
<Astrophys. J., 726, L20 (2011)>
=2011ApJ...726L..20O 2011ApJ...726L..20O
ADC_Keywords: Stars, giant ; Abundances ; Radial velocities ;
Associations, stellar ; Clusters, globular
Keywords: Galaxy: abundances - Galaxy: bulge - infrared: stars -
stars: abundances - stars: late-type - techniques: spectroscopic
Abstract:
We present the chemical abundance analysis of 33 red giant stars
belonging to the complex stellar system Terzan 5. We confirm the
discovery of two stellar populations with distinct iron abundances: a
relatively metal-poor component with [Fe/H]=-0.25±0.07rms and
another component with [Fe/H]=+0.27±0.04rms, exceeding in
metallicity any known Galactic globular cluster (GC). The two
populations also show different [α/Fe] abundance ratios. The
metal-poor component has an average [α/Fe]=+0.34±0.06rms,
consistent with the canonical scenario for rapid enrichment by core
collapse supernovae (SNe). The metal-rich component has
[α/Fe]=+0.03±0.04rms, suggesting that the gas from which it
formed was polluted by both type II and type Ia SNe on a longer
timescale. Neither of the two populations shows evidence of the
[Al/Fe] over [O/Fe] anti-correlation that is typically observed in
Galactic GCs. Because these chemical abundance patterns are unique, we
propose that Terzan 5 is not a true GC, but a stellar system with a
much more complex history of star formation and chemical enrichment.
Description:
High-resolution spectra have been acquired on 2010 July 1-2 by using
NIRSPEC at Keck II. A slit width of 0.43", giving an overall spectral
resolution R=25000, and the standard NIRSPEC-5 setting, which covers a
large fraction of the 1.5-1.8um H band, have been used.
Here, we report and discuss the results for 33 giants having radial
velocities consistent with the systemic velocity of Terzan 5, i.e.,
likely members of the system.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 128 33 Stellar parameters and abundances for the sample
of observed giants in Terzan 5
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See also:
III/249 : Stellar radial velocities bibliographic catalog (Malaroda+, 2006)
VII/151 : Structure Parameters of Galactic Globular Clusters (Webbink 1985)
VII/103 : Galactic Globular Clusters (Monella 1985)
VII/44 : Star Clusters Associations II. Globular Clusters (Ruprecht+ 1981)
J/AJ/140/1043 : GCs in M31 and the Galaxy (van den Bergh+, 2010)
J/PASP/121/1378 : Positions of variable stars in GCs (Samus+, 2009)
J/AJ/133/1287 : JHK photometry of 24 Galactic GCs (Valenti+, 2007)
J/AJ/133/99 : JHKs surface brightness of Galactic GCs. (Cohen+, 2007)
J/AJ/130/2140 : Abundances and velocities in GCs (Pritzl+, 2005)
J/ApJS/161/304 : Star clusters in the Milky Way and satellites (McLaughlin+,
2005)
J/ApJ/590/797 : Parameters of galactic GCs (Van Den Bregh+, 2003)
J/PAZh/29/253 : GCs as gravitational lenses (Bukhmastova, 2003)
J/A+A/308/733 : NTT VI photometry in Terzan 5 (Ortolani+ 1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Index number
4- 14 F11.7 deg RAdeg Right Ascension in decimal degrees (J2000)
16- 26 F11.7 deg DEdeg Declination in decimal degrees (J2000)
28- 31 I4 K Teff [3400/4500] Effective temperature
33- 35 F3.1 [cm/s2] log(g) [0.5/2] Log of the surface gravity
37- 40 I4 km/s HRV Heliocentric radial velocity
42- 46 F5.2 [Sun] [Fe/H] Log of the Fe/H number abundance
48- 51 F4.2 [Sun] e_[Fe/H] Uncertainty in [Fe/H]
53- 57 F5.2 [Sun] [O/Fe] Log of the O/Fe number abundance
59- 62 F4.2 [Sun] e_[O/Fe] Uncertainty in [O/Fe]
64- 68 F5.2 [Sun] [Si/Fe] Log of the Si/Fe number abundance
70- 73 F4.2 [Sun] e_[Si/Fe] Uncertainty in [Si/Fe]
75- 79 F5.2 [Sun] [Mg/Fe] Log of the Mg/Fe number abundance
81- 84 F4.2 [Sun] e_[Mg/Fe] Uncertainty in [Mg/Fe]
86- 90 F5.2 [Sun] [Ca/Fe] Log of the Ca/Fe number abundance
92- 95 F4.2 [Sun] e_[Ca/Fe] Uncertainty in [Ca/Fe]
97-101 F5.2 [Sun] [Ti/Fe] Log of the Ti/Fe number abundance
103-106 F4.2 [Sun] e_[Ti/Fe] Uncertainty in [Ti/Fe]
108-112 F5.2 [Sun] [Al/Fe] Log of the Al/Fe number abundance
114-117 F4.2 [Sun] e_[Al/Fe] Uncertainty in [Al/Fe]
119-123 F5.2 [Sun] [C/Fe] Log of the C/Fe number abundance
125-128 F4.2 [Sun] e_[C/Fe] Uncertainty in [C/Fe]
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 17-Aug-2012