Simultaneous Survey of Water and Class I Methanol Masers toward Red MSX Sources

TL;DR

This study conducts simultaneous surveys of water and methanol masers in protostellar sources, revealing their detection rates, correlations, and evolutionary trends, providing insights into maser origins and star formation processes.

Contribution

First simultaneous survey of water and class I methanol masers toward a large sample of protostellar sources, establishing correlations and evolutionary patterns.

Findings

Detection rates: 45% for water, 28% for 44 GHz methanol, 23% for 95 GHz methanol.

Strong correlations between 44 and 95 GHz masers suggest common origins.

Maser detection rates increase with source evolution, contrasting low-mass star formation trends.

Abstract

We report simultaneous single-dish surveys of 22 GHz H2O and 44 and 95 GHz class I CH3OH masers toward 299 Red MSX Sources in the protostellar stage. The detection rates are 45% at 22 GHz, 28% at 44 GHz, and 23% at 95 GHz. There are 15, 53, and 51 new discoveries at 22, 44, and 95 GHz, respectively. We detect high-velocity (>30 km/s) features in 27 H2O maser sources. The 95 GHz maser emission is detected only in 44 GHz maser sources. The two transitions show strong correlations in the peak velocity, peak flux density, and isotropic maser luminosity, indicating that they are likely generated in the same sites by the same mechanisms. The 44 GHz masers have much narrower distributions than 22 GHz masers in the relative peak velocity and velocity range, while 6.7 GHz class II CH3OH masers have distributions intermediate between the two. The maser luminosity significantly correlates with the parental clump mass, while it correlates well with the bolometric luminosity of the central protostar only when data of the low-mass regime from the literature are added. Comparison with the results of previous maser surveys toward massive star-forming regions suggests that the detection rates of 22 and 44 GHz masers tend to increase as the central objects evolve. This is contrary to the trends found in low- and intermediate-mass star-forming regions. Thus the occurrence of both masers might depend on the surrounding environments as well as on the evolution of the central object.