Journal Article

Spatially resolved study of the physical properties of the ionized gas in NGC 595

M. Relaño, A. Monreal-Ibero, J. M. Vílchez and R. C. Kennicutt

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 3, pages 1635-1648
Published in print March 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI:
Spatially resolved study of the physical properties of the ionized gas in NGC 595

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We present Integral Field Spectroscopy (IFS) of NGC 595, one of the most luminous H ii regions in M33. This type of observations allows us to study the variation of the principal emission-line ratios across the surface of the nebula. At each position of the field of view, we fit the main emission-line features of the spectrum within the spectral range of 3650–6990 Å and create maps of the principal emission-line ratios for the total surface of the region. The extinction map derived from the Balmer decrement and the absorbed Hα luminosity show good spatial correlation with the 24 μm emission from Spitzer. We also show here the capability of the IFS to study the existence of Wolf–Rayet (WR) stars, identifying the previously catalogued WR stars and detecting a new candidate towards the north of the region. The ionization structure of the region nicely follows the Hα shell morphology and is clearly related to the location of the central ionizing stars. The electron density distribution does not show strong variations within the H ii region nor any trend with the Hα emission distribution. We study the behaviour within the H ii region of several classical emission-line ratios proposed as metallicity calibrators: while [N ii]/Hα and [N ii]/[O iii] show important variations, the R23 index is substantially constant across the surface of the nebula, despite the strong variation of the ionization parameter as a function of the radial distance from the ionizing stars. These results show the reliability in using the R23 index to characterize the metallicity of H ii regions even when only a fraction of the total area is covered by the observations.

Keywords: stars: Wolf; Rayet; ISM: abundances; dust, extinction; H ii regions; galaxies: individual: M33

Journal Article.  10285 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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