Astron. Astrophys. Suppl. Ser. 143, 269-301

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

I. Data

M. Szymczak - G. Hrynek - A.J. Kus

Send offprint request: M. Szymczak

Torun Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, PL-87100 Torun, Poland

Received December 17, 1999; accepted February 4, 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 $-20^{\circ}$ with the flux densities greater than 100 Jy at 60 $\mu$m and the flux density ratio F₆₀/F₂₅>1. Observations were made with the sensitivity of 1.7 Jy and the velocity resolution of 0.04 km s^-1 using the 32-m Torun 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.

Key words: masers -- surveys -- stars: formation -- ISM: molecules -- radio lines: ISM -- HII regions