Development of the TRAO control system for the multi-beam receiver and Observational study of water and methanol masers in massive star-forming regions

Abstract

Multi-beam receiver can greatly increase the observation efficiency by allowing observations of wide-field of sky in a short time. World-wide observatories have made efforts to develop such multi-feed receivers. The TRAO imported a multi-beam receiver called QUARRY from the FCRAO, USA, instead of developing it by himself, to swiftly follow the trend. We developed control system for the multi-beam receiver to be compatible with the remaining system. We made a new program and an interface to control spectrometers that acquire data from the receiver, improved a front-end system that manages the receiver, and installed a new data acquisition storage that saves data from Modcomp. In software part, we applied an asynchronous timer and a non-blocking method to the back-end system, used several communication methods to carry command and data directly, and edited the front-end system program with the non-blocking method to minimize a time of tuning process. In hardware part, we revised a DIO board, connected new DIO lines and serial lines, and adopted DMA method to transfer data quickly.

By using the radio telescope equipped with the multi-feed receiver and the KVN telescope, we carried out survey observations toward star forming regions in H2O, CH3OH masers and in HCO+, H13CO+, and 13CO thermal lines to understand their association with star formation activities. The targets are taken from Arecibo methanol maser Galactic plane survey and from Methanol Multibeam catalog identified with 6.7 GHz CH3OH class II methanol maser. The detection rates of 22 GHz, 44 GHz, and 95 GHz toward 271 6.7 GHz class II methanol maser sources are 49 %, 51%, and 44%, respectively. Water maser is detected mostly with other masers, but does not show any correlation with them in terms of the flux density and the velocity. 12 sources out of the 66 sources in which water maser are detected have high-velocity (> 30kms−1) features, and the 7 sources out of the 12 sources may be related with pole-on jets. 95GHz class I methanol maser always comes with 44 GHz class I methanol maser. They are related with each other in the flux density and the velocity. Almost 44 GHz sources (87 %) come with 95 GHz maser. The distribution of velocity offset from the systemic velocity of 6.7GHz peak flux density appears as a double peak shape and differs from others.