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J/ApJ/708/560           Spectroscopy of UMa II and Coma Ber     (Frebel+, 2010)

High-resolution spectroscopy of extremely metal-poor stars in the least evolved galaxies: Ursa Major II and Coma Berenices. Frebel A., Simon J.D., Geha M., Willman B. <Astrophys. J., 708, 560-583 (2010)> =2010ApJ...708..560F
ADC_Keywords: Equivalent widths ; Abundances ; Stars, metal-deficient ; Spectroscopy ; Galaxies, nearby Keywords: early universe - galaxies: dwarf - Galaxy: halo - Local Group - stars: abundances - stars: Population II Abstract: We present spectra of six metal-poor stars in two of the ultra-faint dwarf galaxies orbiting the Milky Way (MW), Ursa Major II, and Coma Berenices obtained with the Keck/High Resolution Echelle Spectrometer (HIRES). These observations include the first high-resolution spectroscopic observations of extremely metal-poor ([Fe/H]←3.0) stars not belonging to the MW halo field star population. We obtain abundance measurements and upper limits for 26 elements between carbon and europium. The entire sample of stars spans a range of -3.2<[Fe/H]←2.3, and we confirm that each galaxy contains a large intrinsic spread of Fe abundances. A comparison with MW halo stars of similar metallicities reveals substantial agreement between the abundance patterns of the ultra-faint dwarf galaxies and the MW halo for the light, α, and iron-peak elements (C to Zn). The abundances of neutron-capture elements (Sr to Eu) in the ultra-faint dwarf galaxies are extremely low, consistent with the most metal-poor halo stars, but not with the typical halo abundance pattern at [Fe/H]≳-3.0. Not only are our results broadly consistent with a galaxy formation model that predicts that massive dwarf galaxies are the source of the metal-rich component ([Fe/H]>-2.5) of the MW halo, but they also suggest that the faintest known dwarfs may be the primary contributors to the metal-poor end of the MW halo metallicity distribution. Description: We observed the target stars (see table 1) with the HIRES spectrograph on the Keck I telescope on 2008 February 22-24. We used a 7.0"x1.15" slit, producing a spectral resolution of R=37000 over the wavelength range from 4100 to 7200Å on the blue and green CCDs. Additional observing details are summarized in Table 2. We use two of the strong Mgb lines in the green part of the HIRES spectra as well as three other Mg lines for our radial velocity measurements. The standard deviation of the individual line measurements is typically <0.5km/s. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 88 8 Photometry and other stellar parameters (table 1 and 5 of the paper) table2.dat 92 8 Observing details ew.dat 52 2191 Equivalent width measurements (table 4) table6.dat 47 84 HIRES abundances of the UMa II stars table7.dat 47 84 HIRES abundances of the Coma Ber stars table9.dat 54 54 HIRES abundances of standard star HD 122563
See also: J/ApJS/191/352 : Abundances in stars of Milky Way dwarf satellites (Kirby+, 2010) J/MNRAS/380/281 : Faint galactic satellites spectroscopic survey (Martin+, 2007) Byte-by-byte Description of file: stars.dat
Bytes Format Units Label Explanations
1- 14 A14 --- Gal Dwarf galaxy name (Coma Berenices or Ursa Major II) 16- 19 A4 --- --- [SDSS] 21- 34 A14 --- SDSS Star SDSS designation (JHHMMSS+DDMMSS) 36- 44 A9 --- Name Star name 46 A1 --- f_Name [f] Non-member star (1) 48- 52 F5.2 mag Vmag ? V-band magnitude (2) 54- 58 F5.2 mag rmag ? SDSS-DR7 r-band magnitude (2) 60- 63 F4.2 mag g-r ? SDSS-DR7 g-r color index (2) 65- 69 F5.2 mag rMag ? Absolute r-band magnitude (2) 71- 74 I4 K Teff Effective temperature (3) 76- 78 F3.1 [cm/s2] logg Surface gravity 80- 84 F5.2 [-] [Fe/H] Fe/H abundance 86- 88 F3.1 km/s Vt Microturbulent velocity ξ
Note (1): f = UMa II-NM was observed but was later determined not to be a member of UMa II. Note (2): The r magnitudes and g-r colors were obtained from the updated SDSS DR7 (Abazajian et al. 2009, Cat. II/294), while the V magnitudes were determined from g and r using the conversions given by Smith et al. (2002AJ....123.2121S). Note (3): Temperature are rounded to the nearest 10K.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Name Star name 11- 12 I2 h RAh Hour of right ascension (J2000) 14- 15 I2 min RAm Minute of right ascension (J2000) 17- 21 F5.2 s RAs Second of right ascension (J2000) 23 A1 --- DE- Sign of declination (J2000) 24- 25 I2 deg DEd Degree of declination (J2000) 27- 28 I2 arcmin DEm Arcminute of declination (J2000) 30- 34 F5.2 arcsec DEs Arcsecond of declination (J2000) 36- 44 F9.1 d JD Julian Date of observation 46- 49 F4.2 h Exp Exposure time 51- 53 I3 --- S/N5 5000AA signal to noise ratio (4) 55- 57 I3 --- S/N6 6000AA signal to noise ratio (4) 59- 61 I3 --- S/N65 6500AA signal to noise ratio (4) 63- 68 F6.1 km/s RVH HIRES radial velocity 70- 72 F3.1 km/s e_RVH RVH uncertainty 74- 79 F6.1 km/s RVD ? DEIMOS radial velocity 81- 83 F3.1 km/s e_RVD ? RVD uncertainty 85- 92 A8 --- Comm Comment
Note (4): The S/N measurements are for ∼22mÅ ("blue" CCD), ∼26mÅ ("green" CCD), and ∼28mÅ ("green" CCD) pixel sizes, respectively.
Byte-by-byte Description of file: ew.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Name Star name 11- 14 A4 --- Ion Species identification 16- 22 F7.2 0.1nm lambda Wavelength in Angstroms 24- 27 F4.2 eV ExPot ? Excitation potential 29- 35 F7.3 [-] log(gf) ? Log of the oscillator strength 37 A1 --- l_EW Limit flag on EW 38- 42 F5.1 0.1pm EW ? Equivalent width in milli-Angstroms 44 A1 --- f_EW [s] s: indicates a spectrum synthesis measurement 46 A1 --- l_log(e) Limit flag on log(e) 47- 52 F6.2 [-] log(e) ? logε abundance (H=12)
Byte-by-byte Description of file: table6.dat table7.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Name Star name 11- 15 A5 --- Ion Species identification 17 A1 --- l_log(e) Limit flag on loge 18- 22 F5.2 [-] log(e) logε abundance (X) 24 A1 --- f_log(e) [a] distorted lines (1) 26 A1 --- l_[X/H] Limit flag on [X/H] 27- 31 F5.2 [Sun] [X/H] X/H abundance 33 A1 --- l_[X/Fe] Limit flag on [X/Fe] 34- 38 F5.2 [Sun] [X/Fe] ? X/Fe abundance (G1) 40- 42 I3 --- N Number of spectra used 44- 47 F4.2 [-] Sig ? Abundance uncertainty
Note (1): a = The Zn lines are somewhat distorted; this may lead to an overestimated Zn abundance.
Byte-by-byte Description of file: table9.dat
Bytes Format Units Label Explanations
1- 9 A9 --- Name Star name 11- 15 A5 --- Ion Species identification 17- 20 F4.2 [-] log(e)X0 ? Log ε abundance (X)0 22 A1 --- l_log(e) Limit flag on loge 23- 27 F5.2 [-] log(e) ? Log ε abundance (X) 29 A1 --- f_log(e) [b] neutron capture element (1) 31 A1 --- l_[X/H] Limit flag on [X/H] 32- 36 F5.2 [Sun] [X/H] ? X/H abundance 38 A1 --- l_[X/Fe] Limit flag on [X/Fe] 39- 43 F5.2 [Sun] [X/Fe] ? X/Fe abundance (G1) 45- 47 I3 --- N ? Number of spectra used 49- 52 F4.2 [-] Sig ? Abundance uncertainty 54 A1 --- ref [cd] source of the data: c=this paper, d=Aoki et al. (2007ApJ...660..747A)
Note (1): b = Neutron-capture abundances are taken from Honda et al. (2006ApJ...643.1180H).
Global notes: Note (G1): [X/Fe] ratios are computed with [FeI/H] abundances of the respective stars. Solar abundances have been taken from Asplund et al. (2005ASPC..336...25A). For abundances measured from only one line, we adopt a nominal uncertainty of 0.20dex.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 02-Feb-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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