Expanding bubbles in Orion A: [C II] observations of M 42, M 43, and NGC 1977

¹ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
e-mail: pabst@strw.leidenuniv.nl
² Instituto de Fisica Fundamental, CSIC, Calle Serrano 121-123, 28006 Madrid, Spain
³ Telespazio Vega UK Ltd. for ESA/ESAC, Urbanizacion Villafranca del Castillo, 28691 Madrid, Spain
⁴ IRAP, Université de Toulouse, CNRS, CNES, UPS, 9 Av. colonel Roche, 31028 Toulouse Cedex 4, France
⁵ I. Physikalisches Institut der Universität zu Köln, Zülpicher Strasse 77, 50937 Köln, Germany
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁷ USRA/SOFIA, NASA Ames Research Center, Mail Stop 232-12, Building N232, PO Box 1, Moffett Field, CA 94035-0001, USA

Received: 23 January 2020
Accepted: 22 April 2020

Abstract

Context. The Orion Molecular Cloud is the nearest massive-star forming region. Massive stars have profound effects on their environment due to their strong radiation fields and stellar winds. Stellar feedback is one of the most crucial cosmological parameters that determine the properties and evolution of the interstellar medium in galaxies.

Aims. We aim to understand the role that feedback by stellar winds and radiation play in the evolution of the interstellar medium. Velocity-resolved observations of the [C II] 158 μm fine-structure line allow us to study the kinematics of UV-illuminated gas. Here, we present a square-degree-sized map of [C II] emission from the Orion Nebula complex at a spatial resolution of 16′′ and high spectral resolution of 0.2 km s⁻¹, covering the entire Orion Nebula (M 42) plus M 43 and the nebulae NGC 1973, 1975, and 1977 to the north. We compare the stellar characteristics of these three regions with the kinematics of the expanding bubbles surrounding them.

Methods. We use [C II] 158 μm line observations over an area of 1.2 deg² in the Orion Nebula complex obtained by the upGREAT instrument onboard SOFIA.

Results. The bubble blown by the O7V star θ¹ Ori C in the Orion Nebula expands rapidly, at 13 km s⁻¹. Simple analytical models reproduce the characteristics of the hot interior gas and the neutral shell of this wind-blown bubble and give us an estimate of the expansion time of 0.2 Myr. M 43 with the B0.5V star NU Ori also exhibits an expanding bubble structure, with an expansion velocity of 6 km s⁻¹. Comparison with analytical models for the pressure-driven expansion of H II regions gives an age estimate of 0.02 Myr. The bubble surrounding NGC 1973, 1975, and 1977 with the central B1V star 42 Orionis expands at 1.5 km s⁻¹, likely due to the over-pressurized ionized gas as in the case of M 43. We derive an age of 0.4 Myr for this structure.

Conclusions. We conclude that the bubble of the Orion Nebula is driven by the mechanical energy input by the strong stellar wind from θ¹ Ori C, while the bubbles associated with M 43 and NGC 1977 are caused by the thermal expansion of the gas ionized by their central later-type massive stars.