On the compact HII galaxy UM 408 as seen by GMOS-IFU: Physical conditions - Astrophysics > Cosmology and Nongalactic AstrophysicsReportar como inadecuado




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Abstract: We present Integral Field Unit GMOS-IFU data of the compact HII galaxy UM408,obtained at Gemini South telescope, in order to derive the spatial distributionof emission lines and line ratios, kinematics, plasma parameters, and oxygenabundances as well the integrated properties over an area of 3-x4-.4~750x1100pc located in the central part of the galaxy. The starburst in this area isresolved into two giant regions of ~375 and 250pc diameter, respectively. Theages of these two regions, estimated using Hb equivalent widths, suggest thatthey are coeval events of ~5Myr with stellar masses of ~10^4M o. We have alsoused OIII-Hb and SII-Ha ratio maps to explore the excitation mechanisms inthis galaxy. The Ha emission line was used to measure the radial velocity andvelocity dispersion. We derived an integrated oxygen abundance of12+logO-H=7.87 summing over all spaxels in our field of view. An averagevalue of 12+logO-H=7.77 and a difference of DO-H=0.47 between the minimumand maximum values 7.58+-0.06-8.05+-0.04 were found, considering all datapoints where the oxygen abundance was measured. The spatial distribution ofoxygen abundance does not show any significant gradient across the galaxy. Onthe other hand, the bulk of data points are lying in a region of +-2sigmadispersion with sigma=0.1 dex around the average value, confirming that thiscompact HII galaxy as other previously studied dwarf irregular galaxies ischemically homogeneous. Therefore, the new metals processed and injected by thecurrent star formation episode are possibly not observed and reside in the hotgas phase, whereas the metals from previous events are well mixed andhomogeneously distributed through the whole extent of the galaxy.



Autor: Patricio Lagos 1,2, Eduardo Telles 1,3, Casiana Munoz-Tunon 2, Eleazar R. Carrasco 4, Francois Cuisinier 5, Guillermo Tenorio-Tag

Fuente: https://arxiv.org/







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