Extremely broad radio recombination maser lines toward the high-velocity ionized jet in Cepheus A HW2

Abstract

We present the first detection of the H40a, H34a and H31a radio recombination lines (RRLs) at millimeter wavelengths toward the high-velocity, ionized jet in the Cepheus A HW2 star forming region. From our single-dish and interferometric observations, we find that the measured RRLs show extremely broad asymmetric line profiles with zero-intensity linewidths of ~1100 kms-1. From the linewidths, we estimate a terminal velocity for the ionized gas in the jet of >500 kms-1, consistent with that obtained from the proper motions of the HW2 radio jet. The total integrated line-to-continuum flux ratios of the H40a, H34a and H31a lines are 43, 229 and 280 kms-1, clearly deviating from LTE predictions. These ratios are very similar to those observed for the RRL maser toward MWC349A, suggesting that the intensities of the RRLs toward HW2 are affected by maser emission. Our radiative transfer modeling of the RRLs shows that their asymmetric profiles could be explained by maser emission arising from a bi-conical radio jet with a semi-aperture angle of 18 deg, electron density distribution varying as r^(-2.11) and turbulent and expanding wind velocities of 60 and 500 kms-1.

6 pages, 2 figures, 3 tables, accepted for publication in ApJL

References in corpus (6)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Early Evolution of Massive Stars: Radio Recombination Line Spectra
• A wide-angle outflow with the simultaneous presence of a high-velocity jet in the high-mass Cepheus A HW2 system
• A Photoevaporating Rotating Disk in the Cepheus A HW2 Star Cluster
• SMA Imaging of the Maser Emission from the H30$\alpha$ Radio Recombination Line in MWC349A
• High-resolution study of a star-forming cluster in the Cep-A HW2 region

Cited by in corpus (23)

• Radio Jets from Young Stellar Objects
• Survey Observations of a Possible Glycine Precursor, Methanimine (CH${}_2$NH)
• Observing the onset of outflow collimation in a massive protostar
• Slow ionized wind and rotating disklike system associated with the high-mass young stellar object G345.4938+01.4677
• A non-LTE radiative transfer model to study ionized outflows and disks. The case of MWC349A
• A search for non-thermal radio emission from jets of massive young stellar objects
• A new radio recombination line maser object toward the MonR2 HII region
• A pilot search for mm-wavelength recombination lines from emerging ionized winds in pre-planetary nebulae candidates
• A photoionized accretion disk around a young high-mass star
• ALMA and VLA observations of recombination lines and continuum toward the Becklin-Neugebauer object in Orion
• Herschel Planetary Nebula Survey (HerPlaNS): Hydrogen Recombination Laser Lines in Mz 3
• The SOMA Radio Survey. I. Comprehensive SEDs Of High-Mass Protostars From Infrared To Radio And The Emergence Of Ionization Feedback
• Millimeter Spectral Line Mapping Observations Toward Four Massive Star Forming HII Regions
• Inverted level populations of hydrogen atoms in ionized gas
• A rotating fast bipolar wind and disk system around the B[e]-type star MWC 922
• Evidence for the First Extragalactic Hydrogen Recombination Line Maser in NGC 253
• An ionized outflow in Orion-KL source I?
• Imaging Molecular Outflow in Massive Star-forming Regions with HNCO Lines
• Imaging the jet of MWC 349A with resolved Radio Recombination Line emission from ALMA
• An nl-model with radiative transfer for hydrogen recombination line masers
• VLBI multi-epoch water maser observations toward massive protostars
• The SOFIA Massive (SOMA) Star Formation Q-band Follow-up. II. Hydrogen Recombination Lines Toward High-Mass Protostars
• ngVLA Synthetic Observations of Ionized Gas in Massive Protostars