Simultaneous 22 GHz Water and 44 GHz Methanol Masers Survey of Ultracompact HII Regions

Abstract

We have carried out a multi-epoch simultaneous survey of 22 GHz H${}_2$O and 44 GHz Class I CH${}_3$OH masers toward 103 ultracompact HII regions (UCHIIs) between 2010 and 2017. We detected H${}_2$O and CH${}_3$OH maser emission in 74 (72%) and 55 (53%) UCHIIs, respectively. Among them, 3 H${}_2$O and 27 CH${}_3$OH maser sources are new detections. These high detection rates suggest that the occurrence periods of both maser species are significantly overlapped with the UCHII phase of massive star formation. The CH${}_3$OH maser lines always have small (< 10 km s${}^{-1}$) relative velocities with respect to the natal molecular cores, while H${}_2$O maser lines often show larger relative velocities. Twenty four H${}_2$O maser-detected sources have maser lines at relative velocities > 30 km s${}^{-1}$, and thirteen of them show extremely high-velocity (> 50 km s${}^{-1}$) components. The appearance and disappearance of H${}_2$O maser lines are quite frequent over six-month or one-year time intervals. In contrast, CH${}_3$OH maser lines usually do not exhibit significant variations in the line intensity, velocity, or shape for the same periods. The isotropic luminosities of both masers appear to correlate with the bolometric luminosities of the central stars. This correlation becomes much stronger in the case that data points in the low- and intermediate-mass regimes are added. The maser luminosities also tend to increase with the radio continuum luminosities of UCHIIs and the submillimeter continuum luminosities of the associated dense cores.

Accepted for publication in ApJS, 43 pages, 13 figures, and 6 tables

References in corpus (18)

• The observed spiral structure of the Milky Way
• ATLASGAL --- towards a complete sample of massive star forming clumps
• The 6-GHz Multibeam Maser Survey I. Techniques
• The Evolution of the Multiplicity of Embedded Protostars I: Sample Properties and Binary Detections
• A SCUBA imaging survey of ultracompact HII regions: The environments of massive star formation
• The Arecibo Methanol Maser Galactic Plane Survey--I: Data
• On the Relationship of UC H II Regions and Class II Methanol Masers: I. Source Catalogs
• Water maser variability over 20 years in a large sample of star-forming regions: the complete database
• The almost ubiquitous association of 6.7 GHz methanol masers with dust
• Methanol Maser Associated Outflows: Detection statistics and properties
• Associations of water and methanol masers at milli-arcsec angular resolution in two high-mass young stellar objects
• A Catalog of Methanol Masers in Massive Star-forming Regions. III. The Molecular Outflow Sample
• Occurrence Frequency of CO Outflows in Massive Protostellar Candidates
• 6.7 GHz variability characteristics of new periodic methanol maser sources
• Hot Ammonia around Young O-type Stars. II. JVLA imaging of highly-excited metastable ammonia masers in W51-North
• Simultaneous Survey of Water and Class I Methanol Masers toward Red MSX Sources
• New detections of (sub)millimeter hydrogen radio recombination lines towards high-mass star-forming clumps
• A highly variable methanol maser in G111.256-0.770