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

Published online by Cambridge University Press:  16 July 2018

A. M. Sobolev ,
N. N. Shakhvorostova ,
A. V. Alakoz  and
W. A. Baan
A. M. Sobolev
Affiliation:
Astronomical Observatory, Ural Federal University, Lenin Ave. 51, Ekaterinburg 620083, Russia email: Andrej.Sobolev@urfu.ru
N. N. Shakhvorostova
Affiliation:
Astro-Space Center of LPI RAS, Moscow, Russia
A. V. Alakoz
Affiliation:
Astro-Space Center of LPI RAS, Moscow, Russia
W. A. Baan
Affiliation:
ASTRON, Netherlands
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Abstract

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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 two 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\muas\, 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 achieved by 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.

Keywords

masersstars: formationgalaxies: fundamental parameterstechniques: high angular resolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S336: Astrophysical Masers: Unlocking the Mysteries of the Universe , September 2017 , pp. 417 - 421
Copyright
Copyright © International Astronomical Union 2018 

References

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Likhachev, S. F., Kostenko, V. I., Girin, I. et al., 2017, J. Astron. Instrum., 6, 1750004–131CrossRefGoogle Scholar
Shakhvorostova, N. N., Alakoz, A. V., & Sobolev, A. M. 2017, Proc. IAU, this volumeGoogle Scholar