ALMA Observation of the 658 GHz Vibrationally Excited H${}_2$O Maser in Orion KL Source I

Abstract

We present an observational study of the vibrationally excited H${}_2$O line at 658 GHz (${\nu }_2$=1, 1${}_{1,0}$-1${}_{0,1}$) toward Orion KL using the Atacama Large Millimeter/Submillimeter Array (ALMA). This line is clearly detected at the position of the massive protostar candidate, the Source I. The spatial structure is compact with a size of about 100 AU and is elongated along the northeast-southwest low-velocity (18 km s${}^{-1}$) bipolar outflow traced by 22 GHz H${}_2$O masers, SiO masers, and thermal SiO lines. A velocity gradient can be seen perpendicular to the bipolar outflow. Overall spatial and velocity structure seems analogous to that of the 321 GHz H${}_2$O maser line previously detected with ALMA and vibrationally excited SiO maser emission. The brightness temperature of the 658 GHz H${}_2$O line is estimated to be higher than 2$\times$10${}^4$ K, implying that it is emitted via maser action. Our results suggest that the 658 GHz H${}_2$O maser line is emitted from the base of the outflow from a rotating and expanding accretion disk as observed for the SiO masers and the 321 GHz H${}_2$O maser. We also search for two other H${}_2$O lines at 646 GHz (9${}_{7,3}$-8${}_{8,0}$ and 9${}_{7,2}$-8${}_{8,1}$), but they are not detected in Orion KL.

9 pages, 6 figures, accepted for publication in ApJ

References in corpus (11)

• The distance to the Orion Nebula
• Monitoring the Large Proper Motions of Radio Sources in the Orion BN/KL Region
• Imaging the Ionized Disk of the High-Mass Protostar Orion-I
• The Orion Fingers: Near-IR Adaptive Optics Imaging of an Explosive Protostellar Outflow
• ALMA sub-mm maser and dust distribution of VY Canis Majoris
• Submillimeter vibrationally excited water emission from the peculiar red supergiant VY CMa
• Identifying the outflow driving sources in Orion-KL
• ALMA Imaging of Millimeter/Submillimeter Continuum Emission in Orion KL
• VERA and ALMA Observations of the H2O Supermaser Burst in Orion KL
• Submillimeter Array Observations of 321 GHz Water Maser Emission in Cepheus A
• Model of the vibrationally excited H${}_2$O maser at 658 GHz in circumstellar envelopes around asymptotic giant branch stars

Cited by in corpus (10)

• ExoMol molecular line lists XXX: a complete high-accuracy line list for water
• Disk-Driven Rotating Bipolar Outflow in Orion Source I
• ALMA Observations of Orion Source I at 350 and 660 GHz
• Massive Outflows Driven by Magnetic Effects II: Comparison with Observations
• Vibrationally excited water emission at 658 GHz from evolved stars
• ALMA band 8 continuum emission from Orion Source I
• Extremely high excitation SiO lines in disk-outflow system in Orion Source I
• An ionized outflow in Orion-KL source I?
• ALMA observations of submillimeter H2O and SiO lines in Orion Source I
• Survey of (sub)mm water masers in low-mass star-forming regions