Class I methanol masers in low-mass star-forming regions

Abstract

Abstract. Four Class I maser sources were detected at 44, 84, and 95 GHz toward chemically rich outflows in the regions of low-mass star formation NGC 1333I4A, NGC 1333I2A, HH25, and L1157. One more maser was found at 36 GHz toward a similar outflow, NGC 2023. Flux densities of the newly detected masers are no more than 18 Jy, being much lower than those of strong masers in regions of high-mass star formation. The brightness temperatures of the strongest peaks in NGC 1333I4A, HH25, and L1157 at 44 GHz are higher than 2000 K, whereas that of the peak in NGC 1333I2A is only 176 K. However, rotational diagram analysis showed that the latter source is also a maser. The main properties of the newly detected masers are similar to those of Class I methanol masers in regions of massive star formation. The former masers are likely to be an extension of the latter maser population toward low luminosities of both the masers and the corresponding YSOs.

CLASS I METHANOL (CH3OH) MASER CONDITIONS NEAR SUPERNOVA REMNANTS

“…Their work concluded that the brightest collisionally pumped Class I methanol masers are expected at the transitions at 36.169 GHz (4 −1 − 3 0 E) and 44.070 GHz (7 0 − 6 1 A + ), with slightly weaker masers for the 84.521 GHz (5 −1 − 4 0 E) and 95.169 GHz (8 0 − 7 1 A + ) transitions. These four transitions have been observed associated with outflows in SFRs (e.g., Kurtz et al 2004;Fish et al 2011;Fontani et al 2010;Kalenskii et al 2013). In SNRs, the 84 GHz line has not yet been reported, but the 36 GHz, 44 GHz, and 95 GHz lines have all been detected (Yusef-Zadeh et al 2008;Sjouwerman et al 2010;Pihlström et al 2011a;Shulga et al 2012).…”

“…Although 84 GHz and 95 GHz methanol masers have been detected in SFRs (e.g., Plambeck & Menten 1990;Kalenskii et al 2013), there are less details available for estimates of the density and temperature for these transitions (Cragg et al 1992). The results presented here show that these transitions may be found under the same range of conditions as the 36 GHz and 44 GHz lines.…”

Class I methanol masers in low-mass star formation regions

“…1. The main LMMI properties are discussed in Kalenskii et al (2013). They can be summarised as follows:…”

Ubiquitous millimeter-wavelength Class I methanol masers associated with massive (proto)stellar outflows: ALMA and SMA results

“…Plambeck & Menten 1990, Kurtz et al 2004, Cyganowski et al 2009, Voronkov et al 2014. More recently, Kalenskii et al (2013) detected Class I CH 3 OH masers (at 44, 84, and 95 GHz) towards outflows in low-mass star-forming regions, and found that Class I maser luminosities scaled with the luminosity of the driving protostar. The Class I maser series extend into the (sub)millimeter regime (e.g.…”