Boo-1137 - An Extremely Metal-Poor Star in the Ultra-Faint Dwarf Spheroidal Galaxy Boötes I - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




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Abstract: We present high-resolution, high-S-N spectra of an extremely metal- poorgiant star Boo-1137 in the -ultra-faint- dwarf spheroidal galaxy dSph BootesI absolute magnitude Mv ~ -6.3. With Fe-H = -3.7, this the most metal-poorstar yet identified in an ultra-faint dSph.Comparison of relative abundances, X-Fe, for some 15 elements with those ofthe extremely metal-poor giants of the Galactic halo shows Boo-1137 is -normal-with respect to C and N, the odd-Z elements Na and Al, the Fe-peak elements,and the n-capture elements Sr and Ba, in comparison with the bulk of the halowith Fe-H < -3.0. The alpha- elements Mg, Si, Ca, and Ti are all higher byDeltaX-Fe ~ 0.2 than average halo values. Monte-Carlo analysis indicatesDeltaalpha-Fe values this large are expected with probability ~ 0.02. Theabundance pattern in Boo-1137 suggests inhomogeneous chemical evolution,consistent with the wide internal spread in Fe abundances we reported earlier.The similarity of most of the Boo-1137 relative abundances with respect to halovalues, and the fact that the alpha-elements are all offset by a similar smallamount from the halo averages, points to the same underlying galaxy-scalestellar initial mass function, but that Boo-1137 likely originated in astar-forming region where the abundances reflect either poor mixing ofsupernova SN ejecta, or poor sampling of the SN progenitor mass range, orboth.



Autor: John E. Norris, David Yong, Gerard Gilmore, Rosemary F. G. Wyse

Fuente: https://arxiv.org/







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