Water Masers as an Early Tracer of Star Formation

Abstract

We present a study of the correlation between 22 GHz water maser emission and far-infrared/submillimeter (IR/sub-mm) sources. The generalized linear model (GLM) is used to predict H2O maser detection in a particular source with defined physical parameters. We checked the GLM predictions by observing a sample of selected sources with the Effelsberg 100 m telescope. In total, 359 sources were observed. H2O masers were detected in 124 sources, with 56 new detections. We found 22 sources with a significant flux variability. Using the GLM analysis, we estimate that 2392 ± 339 star formation regions (SFRs) in the Galaxy may harbor H2O masers detectable by single-dish observations at the noise level of ∼0.05 Jy. Analyzing the luminosity-to-mass ratio (L/M) of the ATLASGAL and Hi-GAL clumps associated with different maser species, we find that 22 GHz water masers have significantly lower values of L/M in comparison to 6.7 GHz class II methanol and 1665 MHz OH masers. This implies that 22 GHz water masers may appear prior to 6.7 GHz methanol and OH masers in the evolutionary sequence of SFRs. From the analysis of physical offsets between host clumps and maser interferometric positions, we found no significant difference between the H2O and class II methanol maser offsets against the host clump position. We conclude that the tight association between water masers and IR/sub-mm sources may provide insight into the pumping conditions of these masers and the evolutionary stages of their onset.

Luminosity Outburst Energized by the Collision between the Infalling Streamer and Disk in W51 North

“…In particular, our monitoring for the H 2 O maser was not intense enough to catch the details of this burst event in 2020, which limits our development of such a model. Therefore, an intense monitoring of a H 2 O maser with duration <10 days (Felli et al 2007;Ladeyschikov et al 2022) or other molecules is needed in the future.…”

Radio Continuum and Water Maser Observations of the High-mass Protostar IRAS 19035+0641 A

“…As a by-product of our radio continuum survey, we observed the 22.2 GHz (6 1,6 − 5 2,3 ) H 2 O (water) maser emission toward the jet candidates. Water masers are collisionally pumped in high-density regions (n ∼ 10 8 -10 10 cm −3 ; Elitzur 1992) and are usually associated with jets and outflows from early-stage highmass YSOs (e.g., Moscadelli et al 2019;Ladeyschikov et al 2022). The detection of water masers in close proximity to the jet candidates would therefore strongly support the jet interpretation for the radio continuum sources.…”

In Search of Infall Motion in Molecular Clumps. V. HCO+ (1–0) and HCN (1–0) Observations toward 210 Infall Candidates

“…To further increase the confidence levels of the infall candidates, we searched for other star-forming activities such as masers and outflows in the literature and website database that are associated with our sources. The associated known star-forming regions are taken from Simbad, 6 while masers are from the MaserDB database 7 (Ladeyschikov et al 2019(Ladeyschikov et al , 2022. The MaserDB database collects the most complete data on maser emission in various lines such as CH 3 OH, H 2 O, OH, etc., including negative registrations from accumulated literature.…”