J/MNRAS/442/1680 Red giants in SMC. Abundances (Dobbie+, 2014)
Red giants in the Small Magellanic Cloud.
II. Metallicity gradient and age-metallicity relation.
Dobbie P.D., Cole A.A., Subramaniam A., Keller S.
<Mon. Not. R. Astron. Soc., 442, 1680-1692 (2014)>
=2014MNRAS.442.1680D 2014MNRAS.442.1680D
ADC_Keywords: Magellanic Clouds ; Stars, giant ; Abundances
Keywords: stars: abundances - galaxies: abundances - galaxies: evolution -
galaxies: individual: SMC - Local Group
Abstract:
We present results from the largest Caii triplet line metallicity
study of Small Magellanic Cloud (SMC) field red giant stars to date,
involving 3037 objects spread across approximately 37.5deg2, centred
on this galaxy. We find a median metallicity of [Fe/H]=-0.99±0.01,
with clear evidence for an abundance gradient of -0.075±0.011dex/deg
over the inner 5°. We interpret the abundance gradient to be the
result of an increasing fraction of young stars with decreasing
galactocentric radius, coupled with a uniform global age-metallicity
relation. We also demonstrate that the age-metallicity relation for an
intermediate-age population located 10kpc in front of the north-east
of the cloud is indistinguishable from that of the main body of the
galaxy, supporting a prior conjecture that this is a stellar analogue
of the Magellanic Bridge. The metal-poor and metal-rich quartiles of
our red giant branch star sample (with complementary optical
photometry from the Magellanic Clouds Photometric Survey) are
predominantly older and younger than approximately 6Gyr, respectively.
Consequently, we draw a link between a kinematical signature,
tentatively associated by us with a disc-like structure, and the
upsurges in stellar genesis imprinted on the star formation history of
the central regions of the SMC. We conclude that the increase in the
star formation rate around 5-6Gyr ago was most likely triggered by an
interaction between the SMC and Large Magellanic Cloud.
Description:
The details of our selection and optical spectroscopic follow-up
of SMC red giant stars are described in Paper I: Dobbie et al.
(2014MNRAS.442.1663D 2014MNRAS.442.1663D, Cat. J/MNRAS/442/1663).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 83 3037 Details of the 3037 SMC red giant stars, including
our CaII triplet equivalent width measurements
and abundance estimates
table4.dat 85 1865 Details derived from the 1865 RGB star sources
(1835 of which are unique) for which both V- and
I-band photometry is available in the MCPS (Cat.
J/AJ/123/855) and extinction levels can be
estimated from the work of Haschke et al.
(2011AJ....141..158H 2011AJ....141..158H)
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See also:
J/A+A/304/347 : 40 field red supergiants in the SMC (Meliani+, 1995)
J/AJ/123/855 : Magellanic Clouds Photometric Survey: SMC (Zaritsky+, 2002)
J/AJ/131/2514 : Radial velocities of red giants in the SMC (Harris+, 2006)
J/AJ/136/1039 : CaII index of SMC red giant branch stars (Carrera+, 2008)
J/AJ/138/517 : CaII spectroscopy of SMC red giants (Parisi+, 2009)
J/ApJ/754/35 : Red supergiant stars in the SMC. II. (Yang+, 2012)
J/MNRAS/442/1663 : Red giants in the SMC. Velocities (Dobbie+, 2014)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 11 F5.2 s RAs Right ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 40 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs)
42- 46 F5.2 mag Jmag [14/15.2] 2MASS J magnitude
48- 51 F4.2 mag e_Jmag [0.02/0.08] rms uncertainty on Jmag
53- 57 F5.2 mag Ksmag [12.95/14.59] 2MASS Ks magnitude
59- 62 F4.2 mag e_Ksmag [0.02/0.11] rms uncertainty on Ksmag
64- 67 F4.2 0.1nm EW [0.16/9.1] CaII triplet equivalent width
69- 72 F4.2 0.1nm e_EW [0.11/1.42] rms uncertainty on EW
74- 78 F5.2 [Sun] [Fe/H] [-3.28/-0.39] Metallicity
80- 83 F4.2 [Sun] e_[Fe/H] [0.06/0.47] rms uncertainty on [Fe/H]
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 2 I2 h RAh Right ascension (J2000)
4- 5 I2 min RAm Right ascension (J2000)
7- 11 F5.2 s RAs Right ascension (J2000)
13 A1 --- DE- Declination sign (J2000)
14- 15 I2 deg DEd Declination (J2000)
17- 18 I2 arcmin DEm Declination (J2000)
20- 23 F4.1 arcsec DEs Declination (J2000)
25- 40 A16 --- 2MASS 2MASS name (HHMMSSss+DDMMSSs)
42- 46 F5.2 mag Vmag [16.18/19.21] V magnitude
48- 51 F4.2 mag e_Vmag [0.02/0.47] rms uncertainty on Vmag
53- 56 F4.2 mag AV [0.02/0.38] Absorption in V band
58- 62 F5.2 mag Imag [14.83/16.49] I magnitude
64- 67 F4.2 mag e_Imag [0.02/0.53] rms uncertainty on Imag
69- 72 F4.2 mag AI [0.01/0.23] Absorption in I band
74- 78 F5.2 [Gyr] Age [9/10.13] log(Age)
80- 85 F6.2 [Gyr] e_Age [] rms uncertainty on log(Age)
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History:
From electronic version of the journal
References:
Dobbie et al., Paper I, 2014MNRAS.442.1663D 2014MNRAS.442.1663D, Cat. J/MNRAS/442/1663
(End) Patricia Vannier [CDS] 02-Mar-2015