Search for Class I methanol masers in low-mass star formation regions

Abstract

A survey of young bipolar outflows in regions of low-to-intermediate-mass star formation has been carried out in two Class I methanol maser transitions: 7 0 -6 1 A + at 44 GHz and 4 -1 -3 0 E at 36 GHz. We detected narrow features towards NGC 1333I2A, NGC 1333I4A, HH25MMS and L1157 at 44 GHz, and towards NGC 2023 at 36 GHz. Flux densities of the lines detected at 44 GHz are no higher than 11 Jy and the relevant source luminosities are about 10 22 erg s -1 , which is much lower than those of strong masers in high-mass star formation regions. No emission was found towards 39 outflows. All masers detected at 44 GHz are located in clouds with methanol column densities of the order of or larger than a few 10 14 cm -2 . The upper limits for the non-detections are typically of the order of 3-5 Jy. Observations in 2004Observations in , 2006Observations in and 2008 did not reveal any significant variability of the 44 GHz masers in NGC 1333I4A, HH25MMS and L1157.