Chemical and photometric evolution of extended ultraviolet disks: Optical spectroscopy of M83 (NGC 5236) and NGC 4625



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Gil de Paz, Armando and otros, ... (2007) Chemical and photometric evolution of extended ultraviolet disks: Optical spectroscopy of M83 (NGC 5236) and NGC 4625. Astrophysical journal, 661 (1). pp. 115-134. ISSN 0004-637X

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We present the results from the analysis of optical spectra of 31 Hα-selected regions in the extended UV (XUV) disks of M83 (NGC 5236) and NGC 4625 recently discovered by GALEX. The spectra were obtained using IMACS at the Las Campanas Observatory 6.5 m Magellan I telescope and COSMIC at the Palomar 200 inch (5 m) telescope, respectively, for M83 and NGC 4625. The line ratios measured indicate nebular oxygen abundances (derived from the R23 parameter) of the order of Z_☉/5-Z_☉/10. For most emission-line regions analyzed the line fluxes and ratios measured are best reproduced by models of photoionization by single stars with masses in the range 20-40 M_☉ and oxygen abundances comparable to those derived from the R23 parameter. We find indications for a relatively high N/O abundance ratio in the XUV disk of M83. Although the metallicities derived imply that these are not the first stars formed in the XUV disks, such a level of enrichment could be reached in young spiral disks only 1 Gyr after these first stars would have formed. The amount of gas in the XUV disks allows maintaining the current level of star formation for at least a few Gyr.

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© 2007. The American Astronomical Society. All rights reserved. Artículo firmado por 24 autores. GALEX (Galaxy Evolution Explorer) is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA’s support for construction, operation, and science analysis for the GALEX mission, developed in cooperation with the Centre National d’Etudes Spatiales of France and the Korean Ministry of Science and Technology. We thank the anonymous referee for his/ her constructive comments that have considerably improved the content of the paper. A. G. d. P. is financed by the MAGPOP EU Marie Curie Research Training Network and partially by the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2003-01676. We thank Judith Cohen for kindly providing her Hα filter for COSMIC. We are also thankful to Sergio González and Wojtek Krzeminski for carrying out the imaging observations at the Las Campanas 40 inch telescope.

Uncontrolled Keywords:H-II regions; Chemo-spectrophotometric evolution; Emission-line galaxies; Star-formation rate; Oxygen abundance determination; Combined stellar structure; De-Madrid list; Spiral galaxies; Infrared-emission; Galactic disks
Subjects:Sciences > Physics > Astrophysics
Sciences > Physics > Astronomy
ID Code:35834
Deposited On:22 Feb 2016 15:17
Last Modified:10 Dec 2018 15:05

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