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

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.Comment: To be published in Astrophysical Masers: Unlocking the Mysteries of the Universe, IAU Symposium 336, 201

RadioAstron probes the ultra-fine spatial structure in the H2_2O maser emission in the star forming region W49N

H$_2$O maser emission associated with the massive star formation region W49N were observed with the Space-VLBI mission RadioAstron. The procedure for processing of the maser spectral line data obtained in the RadioAstron observations is described. Ultra-fine spatial structures in the maser emission were detected on space-ground baselines of up to 9.6 Earth diameters. The correlated flux densities of these features range from 0.1% to 0.6% of the total flux density. These low values of correlated flux density are probably due to turbulence either in the maser itself or in the interstellar medium.Comment: Accepted for publication in Advances in Space Researc

JVLA overview of the bursting H2_2O maser source G25.65+1.05

The source G25.65+1.05 (RAFGL7009S, IRAS 18316-0602) is the least studied of the three regions of massive star formation known to show exceptionally powerful H$_2$O maser bursts. We report spectral line observations of the H$_2$O maser at 22 GHz, the methanol maser transitions at 6.7, 12.2 and 44 GHz, and the continuum in these same frequency bands with The Karl G. Jansky Very Large Array (JVLA) at the post-burst epoch of 2017. For the first time, maps of 22 GHz H$_2$O and 44 GHz CH$_3$OH maser spots are obtained and the absolute position of the 22 GHz H$_2$O bursting feature is determined with milliarcsecond precision. We detected four continuum components, three of which are closely spaced in a linear orientation, suggesting a physical link between them

Brightness temperatures of galactic masers observed in the RadioAstron project

We present estimates of brightness temperature for 5 galactic masers in star-forming regions detected at space baselines. Very compact features with angular sizes of ~23-60 μas were detected in these regions with corresponding linear sizes of ~4-10×10 6 km. Brightness temperatures range from 10 14 up to 10 16 K. © International Astronomical Union 2018

Online Database of Multiwavelength Water Masers in Galactic Star-Forming Regions

In this paper, we present an online multiwavelength database of water masers in star-forming regions of the Galaxy. The collected data represent 1/495% of all observations of water masers in star-forming regions published since 1989. Nineteen transitions are included, from 22 GHz to 1.88 THz. The MaserDB.net information system provides fast and open access to the collected data, including maser tabular data, spectra, and interferometric maser spot data. The database covers 1/418,700 individual observations and 1/47200 maser detections. The data on the water maser detection are available for 1/42600 sources, and interferometric data are available for 1/4560 sources. Statistical analysis of the water masers' data and comparison with other abundant maser species found in star-forming regions (OH and CH3OH of class I and II) show that water masers are the most ubiquitous maser type. Access to the water maser database is available online at https://MaserDB.net. The database can be queried using a web search form or Structured Query Language. © 2022. The Author(s). Published by the American Astronomical Society.The work on development of the water masers database and association with external catalogs (Section ), the web interface improve (Section ) and the analysis of the water masers’ distribution in the Galaxy (Section ) were funded by Russian Science Foundation grant 20-72-00137. The work on checking the quality of the source classification scheme (Section ) was supported by the Russian Ministry of Science and Higher Education, No. FEUZ-2020-0030. The work on the detection rate of water masers in star-forming regions (Section ) was funded by Russian Science Foundation grant 18-12-00193

Vlbi research in the ”Radioastron” project: structure of the H2O maser in NGC 2071 IRS 1

В рамках научной программы интерферометра «Радиоастрон» обработаны данные наблюдений мазера Н2О на частоте 22.2280 ГГц в туманности NGC 2071. В наблюдениях принимали участие космический радиотелескоп (КРТ — 10 м) и три радиотелескопа наземной сети: РТ — 32 м (Медичина, Италия), РТ — 32 м (Торунь, Польша) и РТ — 64 м (Калязин, РФ). Получена карта распределения мазерных пятен, где присутствуют 13 пространственных компонентов в интервале VLSR = (4.7—20.5) км/с. Зафиксирован компонент (VLSR = 14.3 км/с), для которого на наземно-космических базах наблюдается корреляция. На основании анализа зависимости функции видности от величины проекций баз предложена двухкомпонентная модель пространственной структуры этого компонента с размерами протяженной и компактной составляющей 4 и 0.06 мс, т. е. 1.56 и 0.023 a. e. соответственно.Within the Radioastron interferometer scientific program, observational data of the H2O maser at a frequency of 22.2280 GHz in the NGC 2071 nebula were processed. A space radio telescope (SRT — 10 m) and three radio telescopes of the ground network: RT — 32 m (Medicina, Italy), RT — 32 m (Torun, Poland) and RT —64 m (Kalyazin, RF) took part in the observations. A map of the maser spot distribution has been obtained, where there are 13 spatial components with VLSR in the range 4.7 — 20.5 km/s. Correlation is observed on ground-space baselines for the component on VLSR = 14.3 km/s. Based on the visibility function dependence analysis from the baseline projection values, there was proposed a twocomponent model of this component spatial structure with the dimensions of the extended and compact constituent of 4 and 0.06 msec, i.e. 1.56 and 0.023 au, respectively

VLBI observations of the G25.65+1.05 water maser superburst

This paper reports observations of a 22 GHz water maser 'superburst' in the G25.65+1.05 massive star-forming region, conducted in response to an alert from the Maser Monitoring Organisation (M2O). Very long baseline interferometry (VLBI) observations using the European VLBI Network (EVN) recorded a maser flux density of 1.2 × 104 Jy. The superburst was investipgated in the spectral, structural, and temporal domains and its cause was determined to be an increase in maser path length generated by the superposition of multiple maser emitting regions aligning in the line of sight to the observer. This conclusion was based on the location of the bursting maser in the context of the star-forming region, its complex structure, and its rapid onset and decay. © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyRAB acknowledges support through the EACOA Fellowship from the East Asian Core Observatories Association. GO acknowledges support from the Australian Research Council Discovery project DP180101061 funded by the Australian Government, the CAS ‘Light of West China’ Program 2018-XBQNXZ-B-021, and the National Key R&D Program of China 2018YFA0404602. TH is financially supported by the MEXT/JSPS KAKENHI Grant Number 17K05398. BM acknowledges support from the Spanish Ministerio de Economía y Competitividad (MINECO) under grants AYA2016-76012-C3-1-P and MDM-2014-0369 of ICCUB (Unidad de Excelencia ‘María de Maeztu’). NS acknowledges support from Russian Science Foundation grant 18-12-00193. AMS is supported by the Ministry of Science and High Education (the basic part of the State assignment, RK No. AAAA-A17-117030310283-7) and by the Act 211 Government of the Russian Federation, contract No.02.A03.21.0006. JOC acknowledges support by the Italian Ministry of Foreign Affairs and International ..