RadioAstron space-VLBI project: studies of masers in star forming regions of our Galaxy and megamasers in external galaxies

TL;DR

RadioAstron space-VLBI observations achieved unprecedented angular resolution in maser studies, detecting ultra-compact features in star-forming regions and megamasers, demonstrating the technique's feasibility and opening new avenues for cosmic object research.

Contribution

First detection of cosmic water masers with baselines exceeding Earth diameter, establishing microarcsecond resolution in maser observations.

Findings

Detected fringes in water and hydroxyl masers

Achieved angular resolution of about 20 microarcseconds

Recorded fringes on baselines over 25 Earth Diameters

Abstract

Observations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20 microarcsec have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is done in the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space-VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.