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J/ApJ/719/931           Chemical evolution of the UMi dSph        (Cohen+, 2010)

The chemical evolution of the Ursa Minor dwarf spheroidal galaxy. Cohen J.G., Huang W. <Astrophys. J., 719, 931-949 (2010)> =2010ApJ...719..931C
ADC_Keywords: Equivalent widths ; Stars, giant ; Effective temperatures Keywords: galaxies: abundances - galaxies: dwarf - galaxies: individual (UMi) Abstract: We present an abundance analysis based on high-resolution spectra of 10 stars selected to span the full range in metallicity in the Ursa Minor (UMi) dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from -1.35 to -3.10 dex. Combining our sample with previously published work for a total of 16 luminous UMi giants, we establish the trends of abundance ratios [X/Fe] as functions of [Fe/H] for 15 elements. In key cases, particularly for the α-elements, these trends resemble those for stars in the outer part of the Galactic halo, especially at the lowest metallicities probed. The neutron-capture elements show an r-process distribution over the full range of Fe metallicity reached in this dSph galaxy. This suggests that the duration of star formation in the UMi dSph was shorter than in other dSph galaxies. The derived ages for a larger sample of UMi stars with more uncertain metallicities also suggest a population dominated by uniformly old (∼13Gyr) stars, with a hint of an age-metallicity relationship. We note the presence of two UMi giants with [Fe/H]←3.0 dex in our sample and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies that accreted somewhat later. Description: The UMi stars in our sample were observed with HIRES-R at the Keck I Telescope during three runs, in 2008 June, 2009 August, and 2010 February. The instrument configuration yielded complete spectral coverage in a single exposure from 3810 to 6700Å, and extends to 8350Å with small gaps between orders. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 60 10 Sample of stars in the Ursa Minor dSph table2.dat 37 10 Stellar parameters for the Ursa Minor giants ew.dat 43 5290 Equivalent widths for ten stars in the Ursa Minor dSph
See also: J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009) J/ApJ/617/L41 : Red giant variable candidates in UMi dSph (Mighell+, 2004) J/AJ/125/1352 : Ursa Minor dSph M,T2, DDO51 photometry (Palma+, 2003) J/AJ/124/3222 : VI photometry of Draco and UMi galaxies (Bellazzini+, 2002) J/AJ/110/2131 : M/L for Draco and UMi. I. (Armandroff+ 1995) J/AJ/90/2221 : UMi dwarf galaxy BV photometry (Olszewski+, 1985) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Name Star designation (1) 8- 9 I2 h RAh Hour of right ascension (J2000) (1) 11- 12 I2 min RAm Minute of right ascension (J2000) 14- 18 F5.2 s RAs Second of right ascension (J2000) 20 A1 --- DE- Sign of declination (J2000) (1) 21- 22 I2 deg DEd Degree of declination (J2000) (1) 24- 25 I2 arcmin DEm Arcminute of declination (J2000) 27- 30 F4.1 arcsec DEs Arcsecond of declination (J2000) 32- 36 F5.2 mag Vmag V-band magnitude (1) 38- 42 F5.2 mag Imag I-band magnitude (1) 44- 47 A4 yr Obs.Y Year of observation 49- 51 A3 "month" Obs.M Month of observation 53- 56 I4 s Exp Exposure time 58- 60 I3 --- S/N Signal to noise ratio (2)
Note (1): The star names, coordinates, and photometry are from Winnick (2003PhDT.........9W), with the original source of the latter two being Palma et al. (2003, Cat. J/AJ/125/1352). Note (2): S/N per spectral resolution element (λ/Δλ=35000) in the continuum at the center of the echelle order at 5800Å.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Name Star designation 8- 11 I4 K Teffp Photometric effective temperature 13- 16 F4.2 [cm/s2] loggp Photometric surface gravity 18- 21 I4 K Teffs Spectroscopic effective temperature 23- 26 F4.2 [cm/s2] loggs Spectroscopic surface gravity 28- 30 F3.1 km/s Vt Turbulent velocity 32- 37 F6.1 km/s RV Heliocentric radial velocity
Byte-by-byte Description of file: ew.dat
Bytes Format Units Label Explanations
1- 6 A6 --- Name Star designation 8- 14 F7.2 0.1nm lambda Wavelength (Å) 16 A1 --- f_lambda [ab] dubious or discrepant line (1) 18- 22 A5 --- Ion Ion identification 24- 27 F4.2 eV chi Excitation potential 29- 35 F7.3 [-] log(gf) Log of the oscillator strength 37- 38 A2 --- l_EW [≤] Limit flag on EW 39- 43 F5.1 10-13m EW ? Equivalent width (mÅ)
Note (1): a = Dubious line, probably should not have been used. b = This line gives an abundance ∼1.0 dex higher than the other two Dy II lines, and is ignored in computing the Dy abundance.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 18-Jun-2012
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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