Giant Extragalactic HII Regions in the Southern Sky

Details Giant Extragalactic HII Regions in the Southern Sky Giant Extragalactic HII Regions in the Southern Sky

Jun 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006rmxac..26..160f&link_type=abstract

XI IAU Regional Latin American Meeting of Astronomy (Eds. L. Infante & M. Rubio) Revista Mexicana de Astronomía y Astrofísica (S

Astronomy and Astrophysics

Astronomy

Scientific paper

The present work aims to discover the presence of Giant H II Regions (GH IIR) in spiral galaxies of the southern hemisphere sky. We have obtained data of eight luminous H II regions in the galaxies NGC 7552, NGC 6070 and NGC 2997 using the Magellan Inamori Kyocera Echelle spectrograph (MIKE) at the Clay Magellan Telescope (LCO), covering the spectral range 3500-7500 Å resolution R ˜ 60K. The high S/N ratio, together with the resolution of the echelle allowed us to solve the profile of emission lines and to calculate the velocity dispersion of the ionized gas. This analysis was done measuring the observed width of the recombination lines profile after correcting for the instrumental profile and the thermal contribution. We have discovered the giant nature of seven out of the eight candidate regions. These giant H II regions lie, within errors, on the already observed regression in the L- σ plane.
The extended wavelength coverage and proper flux calibration for our targets has been ideal to analyze the properties of the ionized gas and determine the nature and evolutionary state of its source of energy.
We have made use of photoionization models to derive abundances based on the use of strong optical emission lines. We can assure that the mechanism of excitation is due to photoionization by stars and that our GHIIRs present solar metallicities. On the other hand, the electron temperature can be determined from the ratio of the auroral line [OIII] λ4363 to a lower excitation line such as [OIII] λ5007. However, we could not measure reliable intensities for the weaker emission lines due to their relatively high metallicity, for these we could only derive an upper limit for their temperatures.

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