Discovery of a Photoionized Bipolar Outflow towards the Massive Protostar G45.47+0.05

Abstract

Massive protostars generate strong radiation feedback, which may help set the mass they achieve by the end of the accretion process. Studying such feedback is therefore crucial for understanding the formation of massive stars. We report the discovery of a photoionized bipolar outflow towards the massive protostar G45.47+0.05 using high-resolution observations at 1.3 mm with the Atacama Large Millimeter/Submillimeter Array (ALMA) and at 7 mm with the Karl G. Jansky Very Large Array (VLA). By modeling the free-free continuum, the ionized outflow is found to be a photoevaporation flow with an electron temperature of 10,000 K and an electron number density of ~1.5x10^7 cm^-3 at the center, launched from a disk of radius of 110 au. H30alpha hydrogen recombination line emission shows strong maser amplification, with G45 being one of very few sources to show such millimeter recombination line masers. The mass of the driving source is estimated to be 30-50 Msun based on the derived ionizing photon rate, or 30-40 Msun based on the H30alpha kinematics. The kinematics of the photoevaporated material is dominated by rotation close to the disk plane, while accelerated to outflowing motion above the disk plane. The mass loss rate of the photoevaporation outflow is estimated to be ~(2-3.5)x10^-5 Msun/yr. We also found hints of a possible jet embedded inside the wide-angle ionized outflow with non-thermal emissions. The possible co-existence of a jet and a massive photoevaporation outflow suggests that, in spite of the strong photoionization feedback, accretion is still on-going.

Accepted to ApJL. 16 pages, 5 figures, 3 appendix figures

References in corpus (11)

• Circumventing the radiation pressure barrier in the formation of massive stars via disk accretion
• A Magnetized Jet from a Massive Protostar
• The Luminosity Functions and Timescales of MYSOs and Compact HII regions
• Weak and Compact Radio Emission in Early High-Mass Star Forming Regions: I. VLA Observations
• The Impact of Feedback During Massive Star Formation by Core Accretion
• Radiation Transfer of Models of Massive Star Formation. IV. The Model Grid and Spectral Energy Distribution Fitting
• Binary system and jet precession and expansion in G35.20-0.74N
• Protostellar Outflows at the EarliesT Stages (POETS). II. A possible radio synchrotron jet associated with the EGO G035.02+0.35
• Trigonometric Parallaxes of Star Forming Regions Beyond the Tangent Point of the Sagittarius Spiral Arm
• Dynamics of a Massive Binary at Birth
• Angular Momentum in Disk Wind Revealed in the Young Star MWC349A

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• The ionized heart of a molecular disk. ALMA observations of the hyper-compact HII region G24.78+0.08 A1
• Isolated Massive Star Formation in G28.20-0.05
• Vibrationally-excited Lines of HC${}_3$N Associated with the Molecular Disk around the G24.78+0.08 A1 Hyper-compact H${}_{\mathrm{II}}$ Region
• Broad-velocity-width Molecular Features in the Galactic Plane
• Imaging the jet of MWC 349A with resolved Radio Recombination Line emission from ALMA
• ngVLA Synthetic Observations of Ionized Gas in Massive Protostars
• The SOFIA Massive (SOMA) Star Formation Q-band Follow-up. II. Hydrogen Recombination Lines Toward High-Mass Protostars
• Discs and outflows in the early phases of massive star formation: influence of magnetic fields and ambipolar diffusion