A global study of the HII region M43 and its ionizing star (I. Stellar parameters and nebular empirical analysis)

Abstract

We have selected the Galactic HII region M43, a close-by apparently spherical nebula ionized by a single star (HD37061) to investigate several topics of recent interest in the field of HII 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. We collected for this study a set of high-quality observations, including the optical spectrum of HD37061, 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. We determine the stellar parameters of HD37061 and the total number of ionizing photons emitted by the star. We find observational evidence of the presence of scattered light from the Huygens region (brightest part of the Orion nebula) in the M43 region. We show the importance of an adequate correction of this scattered light from the imagery and spectroscopic observations of M43 for a proper determination of the total nebular H_alpha luminosity, the nebular physical conditions and chemical abundances. We perform a detailed nebular empirical analysis of 9 apertures extracted from a long-slit located to the west of HD37061, obtaining the spatial distribution of the physical conditions and ionic abundances. For three of the analyzed elements (O, S, and N) we could determine total abundances directly from observable ions (no ionization correction factors were 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.

13 pages, 10 figs, 5 tables. Accepted for publication in A&A. After language correction

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• Expanding bubbles in Orion A: [CII] observations of M42, M43, and NGC 1977
• Density biases and temperature relations for DESIRED HII regions
• [CII] 158 μm self-absorption and optical depth effects
• The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia
• Pumping up the [N I] nebular lines
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• NU Ori: a hierarchical triple system with a strongly magnetic B-type star
• Photoionized Herbig-Haro objects in the Orion Nebula through deep high-spectral resolution spectroscopy II: HH204
• Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method
• [CII] $158\mu \mathrm{m}$ line emission from Orion A. I. A template for extragalactic studies?
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• First Detection of the Molecular Cloud Population in the Extended Ultraviolet (XUV) Disk of M83
• SIRIUS Project. V. Formation of off-center ionized bubbles associated with Orion Nebula Cluster
• Constraining the LyC escape fraction from LEGUS star clusters with SIGNALS HII region observations: A pilot study of NGC 628
• Multiline observations of hydrogen, helium, and carbon radio-recombination lines toward Orion A: A detailed dynamical study and direct determination of physical conditions
• Quantitative spectroscopy of multiple OB stars: I. The quadruple system HD 37061 at the centre of Messier 43
• Dynamical masses of young stellar objects with the VLBA: DYNAMO-VLBA: Radio binary stars in Orion