BOO-1137-AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOOeTES I
Abstract
We present high-resolution (R {approx} 40,000), high-signal-to-noise ratio (20-90) spectra of an extremely metal-poor giant star Boo-1137 in the 'ultra-faint' dwarf spheroidal galaxy (dSph) Booetes I, absolute magnitude M{sub V} {approx} -6.3. We derive an iron abundance of [Fe/H] = -3.7, making this the most metal-poor star as yet identified in an ultra-faint dSph. Our derived effective temperature and gravity are consistent with its identification as a red giant in Booetes I. Abundances for a further 15 elements have also been determined. Comparison of the relative abundances, [X/Fe], with those of the extremely metal-poor red giants of the Galactic halo shows that Boo-1137 is 'normal' with respect to C and N, the odd-Z elements Na and Al, the iron-peak elements, and the neutron-capture elements Sr and Ba, in comparison with the bulk of the Milky Way halo population having [Fe/H] {approx}<-3.0. The alpha-elements Mg, Si, Ca, and Ti are all higher by DELTA[X/Fe] {approx} 0.2 than the average halo values. Monte Carlo analysis indicates that DELTA[alpha/Fe] values this large are expected with a probability {approx}0.02. The elemental abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in iron abundances we previously reported. The similarity ofmore »
- Authors:
-
- Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia)
- Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)
- Department of Physics and Astronomy, Johns Hopkins University, 3900 North Charles Street, Baltimore, MD 21218 (United States)
- Publication Date:
- OSTI Identifier:
- 21394364
- Resource Type:
- Journal Article
- Journal Name:
- Astrophysical Journal
- Additional Journal Information:
- Journal Volume: 711; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/711/1/350; Journal ID: ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABUNDANCE; CALCIUM; GALACTIC EVOLUTION; GIANT STARS; GRAVITATION; IRON; MAGNESIUM; MASS; MILKY WAY; MONTE CARLO METHOD; NEUTRON REACTIONS; SAMPLING; SIGNAL-TO-NOISE RATIO; SILICON; TITANIUM; ALKALINE EARTH METALS; BARYON REACTIONS; CALCULATION METHODS; DIMENSIONLESS NUMBERS; ELEMENTS; EVOLUTION; GALAXIES; HADRON REACTIONS; METALS; NUCLEAR REACTIONS; NUCLEON REACTIONS; SEMIMETALS; STARS; TRANSITION ELEMENTS
Citation Formats
Norris, John E, Yong, David, Gilmore, Gerard, and Wyse, Rosemary F. G.,. BOO-1137-AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOOeTES I. United States: N. p., 2010.
Web. doi:10.1088/0004-637X/711/1/350.
Norris, John E, Yong, David, Gilmore, Gerard, & Wyse, Rosemary F. G.,. BOO-1137-AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOOeTES I. United States. https://doi.org/10.1088/0004-637X/711/1/350
Norris, John E, Yong, David, Gilmore, Gerard, and Wyse, Rosemary F. G.,. 2010.
"BOO-1137-AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOOeTES I". United States. https://doi.org/10.1088/0004-637X/711/1/350.
@article{osti_21394364,
title = {BOO-1137-AN EXTREMELY METAL-POOR STAR IN THE ULTRA-FAINT DWARF SPHEROIDAL GALAXY BOOeTES I},
author = {Norris, John E and Yong, David and Gilmore, Gerard and Wyse, Rosemary F. G.,},
abstractNote = {We present high-resolution (R {approx} 40,000), high-signal-to-noise ratio (20-90) spectra of an extremely metal-poor giant star Boo-1137 in the 'ultra-faint' dwarf spheroidal galaxy (dSph) Booetes I, absolute magnitude M{sub V} {approx} -6.3. We derive an iron abundance of [Fe/H] = -3.7, making this the most metal-poor star as yet identified in an ultra-faint dSph. Our derived effective temperature and gravity are consistent with its identification as a red giant in Booetes I. Abundances for a further 15 elements have also been determined. Comparison of the relative abundances, [X/Fe], with those of the extremely metal-poor red giants of the Galactic halo shows that Boo-1137 is 'normal' with respect to C and N, the odd-Z elements Na and Al, the iron-peak elements, and the neutron-capture elements Sr and Ba, in comparison with the bulk of the Milky Way halo population having [Fe/H] {approx}<-3.0. The alpha-elements Mg, Si, Ca, and Ti are all higher by DELTA[X/Fe] {approx} 0.2 than the average halo values. Monte Carlo analysis indicates that DELTA[alpha/Fe] values this large are expected with a probability {approx}0.02. The elemental abundance pattern in Boo-1137 suggests inhomogeneous chemical evolution, consistent with the wide internal spread in iron abundances we previously reported. The similarity of most of the Boo-1137 relative abundances with respect to halo values, and the fact that the alpha-elements are all offset by a similar small amount from the halo averages, points to the same underlying galaxy-scale stellar initial mass function, but that Boo-1137 likely originated in a star-forming region where the abundances reflect either poor mixing of supernova (SN) ejecta, or poor sampling of the SN progenitor mass range, or both.},
doi = {10.1088/0004-637X/711/1/350},
url = {https://www.osti.gov/biblio/21394364},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 711,
place = {United States},
year = {Mon Mar 01 00:00:00 EST 2010},
month = {Mon Mar 01 00:00:00 EST 2010}
}