Water masers in the ALMA era: an excellent tool to study star formation at sub-arcsecond spatial scales
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Date
2023
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Abstract
The water molecule is one of the most common compounds in the Universe and it exhibits several maser transitions at submillimeter wavelengths, which can be observed at ALMA. Previous studies have primarily focused on water masers at 22 GHz, which are excited in regions of high density and high temperature. These masers are typically very bright, spectrally narrow, and originate from very compact regions. Consequently, they have been invaluable for studying circumstellar structure and dynamics at sub-arcsecond spatial scales. Different water maser transitions can be pumped over a range of astrophysical conditions. The submillimeter transitions at 321 GHz and 325 GHz, in particular, trace respectively warmer and lower density regions than the 22 GHz transition. They have been identified as tracers of mass-loss phenomena in a limited number of star-forming regions. Conversely, transitions such as the one at 183 GHz, which primarily undergo collisional pumping, can provide valuable insights on the physical conditions of the region where powerful molecular outflows interact with the material from the parental cloud. Observations of different water maser lines need to be used to constrain the physical conditions in the masing region and they constitute excellent tools to study common phenomena associated with the star formation process at sub-arcsecond resolution, if observed with interferometers like ALMA. In this poster we present the results of a survey searching for submillimeter water maser transitions at 321 and 325 GHz complemented with ALMA data at 183 GHz on a sample of young stellar objects spanning a wide range of masses, from high to low-mass.