Numerical models for the dust in RCW 120

Abstract

Context. The interstellar bubble RCW 120 seen around a type O runaway star is driven by the stellar wind and the ionising radiation emitted by the star. The boundary between the stellar wind and interstellar medium (ISM) is associated with the arc-shaped midinfrared dust emission around the star within the HII region. Aims. We aim to investigate the arc-shaped bow shock in RCW 120 by means of numerical simulations, including the radiation, dust, HII region, and wind bubble. Methods. We performed 3D radiation-hydrodynamic simulations including dust using the guacho code. Our model includes a detailed treatment of dust grains in the ISM and takes into account the drag forces between dust and gas and the effect of radiation pressure on the gas and dust. The dust is treated as a pressureless gas component. The simulation uses typical properties of RCW 120. We analyse five simulations to deduce the effect of the ionising radiation and dust on both the emission intensity and the shape of the shock. Results. The interaction of the wind and the ionising radiation from a runaway star with the ISM forms an arc-shaped bow shock where the dust from the ISM accumulates in front of the moving star. Moreover, the dust forms a second small arc-shaped structure within the rarefied region at the back of the star inside the bubble. In order to obtain the decoupling between the gas and the dust, it is necessary to include the radiation-hydrodynamic equations together with the dust and the stellar motion. In this work all these elements are considered together, and we show that the decoupling between gas and dust obtained in the simulation is in agreement with the morphology of the infrared observations of RCW 120.

Wind nebulae and supernova remnants of very massive stars

“…This well-known problem (Mackey et al 2015) is unavoidable in two-dimensional axisymmetric simulations of this kind using uniform grids. It can be circumvented by means of three-dimensional calculations, however at the cost of losses in spatial resolution (Rodríguez- González et al 2019).…”

Stellar feedback and triggered star formation in the prototypical bubble RCW 120

“…RCW 120 is considered to be the prototypical triggered star formation source given the simple region morphology and the abundance of ongoing star formation around its edges. Because of its vicinity and its importance in the context of triggered star formation, RCW 120 has been studied extensively through observations (15,16,18,19,(21)(22)(23)(24) and simulations (25)(26)(27)(28)(29).…”

The Role of Magnetic Fields in Triggered Star Formation of RCW 120

“…Alternative hydrodynamic simulations including stellar winds and stellar motions of RCW 120 relative to the ambient cloud, however, favours an inclination angle of 72 • for RCW 120 to match the closer spherical dust shell in the south to the ionizing source and the observed elongation to the northwest (Rodríguez-González et al 2019).…”

“…In this paper, we adopt the most recent distance estimate of 1.68 kpc. RCW 120 is the testbed for studying the interaction of H II region feedback with the ambient gas, dust, and triggered star formation (Zavagno et al 2007(Zavagno et al , 2010(Zavagno et al , 2020Deharveng et al 2009;Martins et al 2010;Anderson et al 2010Anderson et al , 2012Anderson et al , 2015Pavlyuchenkov et al 2013;Tremblin et al 2014b;Ochsendorf et al 2014;Torii et al 2015;Rodón et al 2015;Walch et al 2015;Mackey et al 2016;Akimkin et al 2017;Figueira et al 2017Figueira et al , 2018Figueira et al , 2020Marsh & Whitworth 2019;Rodríguez-González et al 2019;Kirsanova et al 2019Kirsanova et al , 2021Luisi et al 2021;Kabanovic et al 2022). These results greatly enrich our understandings of RCW 120, especially to the star formation on the boarder of RCW 120.…”