2015 Seminar List:
We report simultaneous surveys of 22 GHz water and 44/95 GHz class I methanol masers toward 299 high-mass protostellar objects.
The sources were selected from the catalog of Red MSX Sources (RMSs).
Using the Korea VLBI Network (KVN) 21-m telescopes, we performed a simultaneous survey of 22 GHz and 44 GHz masers in 2011 and a simultaneous survey of 22 GHz, 44 GHz, and 95 GHz masers in 2012.
These surveys aimed to investigate the relationship among the three masers and to explore the relationship of each maser with the central (proto)stars or the natal dense cores.
The detection rates are 38%, 27%, and 23% for 22 GHz, 44 GHz, and 95 GHz masers, respectively.
There are 17 new detections at 22 GHz, 57 at 44 GHz, 52 at 95 GHz.
We detected 8 dominant blue- and red-shifted water maser sources.
Using available ammonia line and submillimeter continuum data, we derived the physical properties of the parent cores and clumps.
The sources with maser emission usually have wider ammonia linewidths and higher kinetic temperatures than those without it.
The estimated virial parameters suggest that the occurrence of maser emission reflects active stage in high-mass star formation.
The sources with only class I methanol masers have significantly lower kinetic temperatures and L / M than those with only water masers.
The statistical analysis of 54 sources associated with class II methanol masers reveals that the sources with only class II methanol masers accompany narrower ammonia linewidths and lower kinetic temperatures than those with only class I methanol masers.
Our findings suggest that class II methanol masers appear at the earliest stage of high-mass star formation and class I methanol masers are present prior to water masers.