A detailed study of the H ii region M 43 and its ionizing star

Simón-Díaz, S.; García-Rojas, J.; Esteban, C.; Stasińska, G.; López-Sánchez, A. R.; Morisset, C.
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Astronomy and Astrophysics, Volume 530, id.A57

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Aims: We have selected the Galactic H ii region M 43, a close-by apparently spherical nebula ionized by a single star (HD 37061, B0.5 V) to investigate several topics of recent interest in the field of H ii regions and massive stars. In a series of two papers, we perform a combined, comprehensive study of the nebula and its ionizing star by using as many observational constraints as possible. Methods: We collected for this study a set of high-quality observations, including the optical spectrum of HD 37061, along with nebular optical imaging and long-slit spatially resolved spectroscopy. The first part of our study comprises a quantitative spectroscopic analysis of the ionizing star, and the empirical analysis of the nebular images and spectroscopy. All the information obtained here will be used to construct a customised photoionization model of the nebula in Paper II. Results: We determine the stellar parameters of HD 37061 and the total number of ionizing photons emitted by the star. We find observational evidence of scattered light from the Huygens region (the brightest part of the Orion nebula) in the M 43 region. We show the importance of an adequate correction of this scattered light in both the imagery and spectroscopic observations of M 43 in accurately determining the total nebular Hα luminosity, the nebular physical conditions. and chemical abundances. We perform a detailed nebular empirical analysis of nine apertures extracted from a long-slit located to the west of HD 37061 (east-west direction), obtaining the spatial distribution of the physical conditions and ionic abundances. For three of the analyzed elements (O, S, and N), we determine total abundances directly from observable ions (no ionization correction factors are needed). The comparison of these abundances with those derived from the spectrum of the Orion nebula indicates the importance of the atomic data and, specially in the case of M 42, the considered ionization correction factors. The INT and WHT telescopes are operated on the island of La Palma by the RGO in the Spanish Roque de los Muchachos Observatory of the Instituto de Astrofísica de Canarias.
Related projects
Izquierda - Imagen RGB de la nebulosa de Orión y M43 obtenida filtros estrechos con la cámara WFC en el INT: H alfa (rojo), [S II] 6716+30 (verde), [O III] 5007 (azul). Derecha - Imagen en falso color de la nebulosa planetaria NGC 6778. En azul se ve la emisión en la línea de O II tomada con el filtro sintonizable azul del instrumento OSIRIS en el GTC; en verde imagen con el filtro estrecho de [O III] del Nordic Optical Telescope (NOT).
Physics of Ionized Nebulae
The research that is being carried out by the group can be condensed into two main lines: 1) Study of the structure, dynamics, physical conditions and chemical evolution of Galactic and extragalactic ionized nebulae through detailed analysis and modelization of their spectra. Investigation of chemical composition gradients along the disk of our
García Rojas
Projets' image
Physical properties and evolution of Massive Stars
This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction). Massive stars are central objects to
Simón Díaz