The Neutral Atomic Hydrogen in the solar neighborhood (NeAtHood) project I. Ghost in the shell: Neutral atomic hydrogen in the extended Orion nebula

Abstract

The Orion Nebula is the nearest site of ongoing and recent high-mass star formation. It is a unique laboratory for studying the mass, energy, and momentum input from high-mass stars. We present 21-centimeter emission line observations that resolve for the first time the neutral atomic hydrogen (HI) gas in the extended Orion nebula (EON) at a resolution of one arcminute, which corresponds to a physical scale of 0.12 parsecs at the standard distance to the region. Our HI emission maps reveal an expanding shell that matches the EON contours delineated by recent observations of ionized carbon ([CII]) line emission. However, our combination of single-dish and interferometric HI observations suggests 100 solar masses of material for the front hemisphere of the shell, which is lower by roughly a factor of ten than the mass inferred from [CII] observations. This discrepancy suggests that the mass of the nearest wind-blown bubble has been overestimated, although we do not rule out the possibility that a significant amount of molecular hydrogen (H_2) in the shell may account for part of the difference. Our extended 21 cm line maps also reveal uncharted structures in and around the EON. They include a probable secondary bubble and a linear protrusion extending roughly four parsecs from the shell boundary. Our results illustrate the potential of HI interferometric observations to elucidate key aspects of the multiphase structure of star-forming regions and their connection to their surroundings.

16 pages, 19 figures

References in corpus (22)

• The distance to the Orion Nebula
• The chemical make-up of the Sun: A 2020 vision
• Herschel-Planck dust optical-depth and column-density maps: I. Method description and results for Orion
• Million-Degree Plasma Pervading the Extended Orion Nebula
• The 21-SPONGE HI Absorption Survey I: Techniques and Initial Results
• Expanding bubbles in Orion A: [CII] observations of M42, M43, and NGC 1977
• The Alma catalog of OB stars. II. A cross-match with Gaia DR2 and an updated map of the solar neighbourhood
• The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and HI overview
• Deviations from He I Case B Recombination Theory and Extinction Corrections in the Orion Nebula
• Gamma-ray observations of the Orion Molecular Clouds with the Fermi Large Area Telescope
• IRAM-30m large scale survey of ${}^{12}$CO(2-1) and ${}^{13}$CO(2-1) emission in the Orion molecular cloud
• Catalog of dense cores in the Orion A giant molecular cloud
• Thermal and turbulent properties of the Warm Neutral Medium in the solar neighborhood
• Molecular globules in the Veil bubble of Orion. IRAM 30m 12CO, 13CO, and C18O 2-1 expanded maps of Orion A
• Data Combination: Interferometry and Single-dish Imaging in Radio Astronomy
• On the accuracy of HI observations in molecular clouds -- More cold HI than thought?
• Bottling the Champagne: Dynamics and Radiation Trapping of Wind-Driven Bubbles around Massive Stars
• Breaking Orion's Veil bubble with fossil outflows
• The Energy and Dynamics of Trapped Radiative Feedback with Stellar Winds
• Dents in the Veil: Protostellar feedback in Orion
• SIRIUS Project. V. Formation of off-center ionized bubbles associated with Orion Nebula Cluster
• The NEMESIS Catalogue of Young Stellar Objects for the Orion Star Formation Complex. I. General description of data curation