A survey of the 6.7 GHz methanol maser emission from IRAS sources^*

I. Data

Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, PL–87100 Toruń, Poland

Send offprint request to: M. Szymczak

Received: 17 December 1999
Accepted: 4 February 2000

Abstract

We report the first results of a search for 6.7 GHz methanol masers in the direction of 1399 IRAS objects north of declination with the flux densities greater than 100 Jy at 60 μm and the flux density ratio . Observations were made with the sensitivity of 1.7 Jy and the velocity resolution of 0.04 km s^-1 using the 32-m Toruń radio telescope. Maser emission was found in 182 sources, including 70 new detections. 32 new sources were identified with objects of radio emission associated with star-forming regions. Comparison of the present data set with other observations suggests that about 65% of methanol masers exhibit moderate or strong variations on time-scales of about 4 and 8 years.