The chemical composition of two supergiants in the dwarf irregular galaxy WLM

The chemical composition of two stars in WLM has been determined from high-quality Ultraviolet-Visual Echelle Spectrograph (UVES) data obtained at the VLT-UT2. The model atmospheres analysis shows that they have the same metallicity, [Fe/H] = - 0.38 +/- 0.20 (+/- 0.29). Reliable magnesium abundances are determined from several lines of two ionization states in both stars resulting in [Mg/Fe] = - 0.24 +/- 0.16 (+/- 0.28). This result suggests that the [alpha(Mg)/Fe] ratio in WLM may be suppressed relative to solar abundances ( also supported by differential abundances relative to similar stars in NGC 6822 and the Small Magellanic Cloud [SMC]). The absolute Mg abundance, [Mg/H] = -0.62, is high relative to what is expected from the nebulae though, where two independent spectroscopic analyses of the H II regions in WLM yield [O/H] = - 0.89. Intriguingly, the oxygen abundance determined from the O I lambda6158 feature in one WLM star is [O/H] = - 0.21 +/- 0.10 (+/- 0.05), corresponding to 5 times higher than the nebular oxygen abundance. This is the first time that a significant difference between stellar and nebular oxygen abundances has been found, and currently, there is no simple explanation for this difference. The two stars are massive supergiants with distances that clearly place them in WLM. They are young ( less than or equal to 10 Myr) and should have a similar composition to the ISM. Additionally, differential abundances suggest that the O/Fe ratio in the WLM star is consistent with similar stars in NGC 6822 and the SMC, galaxies where the average stellar oxygen abundances are in excellent agreement with the nebular results. If the stellar abundances reflect the true composition of WLM, then this galaxy lies well above the metallicity-luminosity relationship for dwarf irregular galaxies. It also suggests that WLM is more chemically evolved than currently interpreted from its color-magnitude diagram. The similarities between the stars in WLM and NGC 6822 suggest that these two galaxies may have had similar star formation histories.

La accesibilidad y el diseño universal entendido por todos. De cómo Stephen Hawking viajó por el espacio

La publicación ‘La accesibilidad y el diseño universal entendido por todos. De cómo Stephen Hawking viajó por el espacio’ es un libro al alcance de todos los públicos para acercarse a la accesibilidad universal, al diseño para todos y a la importancia de la igualdad de oportunidades para todas las personas. Sin duda, el autor se esfuerza con este libro en recopilar y sintetizar gran parte del conocimiento que había disperso en la materia, para condensarlo en una obra amena y apta para cualquier persona, independientemente si es profesional de la accesibilidad o está relacionada con el mundo de la discapacidad.

University Chorale, March 1, 1977

Concert program for University Chorale, March 1, 1977

The Contemporary Group, February 12 and 13 , 1975

Concert program for The Contemporary Group, February 12 and 13, 1975

Training the public health workforce we need. Exploring perceptions for future public heath workers in Ecuador

Thesis (Master's)--University of Washington, 2015

The Consul March 2 & 5, 1966

Concert program for The Consul March 2 & 5, 1966

A Concert of American Music, February 9, 1964

Concert Program for A Concert of American Music, February 9, 1964

The University Wind Sinfonietta, May 17, 1967

Concert program for The University Wind Sinfonietta, May 17, 1967

The Guitar Ensemble May 24, 2003

Concert Program for The Guitar Ensemble May 24 2003

The Guitar Ensemble February 8, 2003

Concert Program for The Guitar Ensemble February 8, 2003