Observations of Extended Green Objects in the 1.35-cm H2O Line on the 22-m Pushchino Radio Telescope

Rudnitskii, G.M.; Lekht, E.E.; Bayandina, O.S.; Val'tts, I.E.; Khan, E.R.

Авторы: Rudnitskii G.M., Lekht E.E., Bayandina O.S., Val'tts I.E., Khan E.R.
Журнал: Astronomy Reports
Том: 60
Номер: 1
Год издания: 2016
Издательство: Maik Nauka/Interperiodica Publishing
Местоположение издательства: Russian Federation
Первая страница: 129
Последняя страница: 144
DOI: 10.1134/S1063772916010029
Аннотация: Observations of H2O maser sources at 1.35 cm associated with extended regions of 4.5-μm emission (indicated as “green” on Spitzer survey maps — so-called Extended Green Objects, EGOs) are reported. EGOs are considered as characteristic signposts of regions of formation of massive stars, which host high-velocity outflows, as well as methanol, water, and hydroxyl masers. The observations were carried out in January–May 2015 on the 22-meter radio telescope of the Pushchino Radio Astronomy Observatory. The sample studied includes 24 EGOs north of declination −29◦ taken from the Spitzer GLIMPSE survey, together with one of the brightest Class I methanol masers G6.05−1.45 (M8E) and the Class I methanol maser in an IRDC G359.94+0.17. H2O maser emission was detected toward 11 of the EGOs: G11.94−0.62, G14.33−0.64, G16.59−0.06, G23.01−0.41, G24.943+0.074, G28.83−0.25, G34.3+0.2, G34.403+0.233, G35.20−0.74, G45.47+0.07, and G49.267−0.337. These including the well known H2O maser in the W44 region, G34.3+0.2. H2O emission from G28.83−0.25 was detected for the first time, at 77.6 km/s, with a flux density of 19 Jy in January and 16 Jy in February 2015. The source was probably caught at an early stage of the propagation of a shock wave. The Class I methanol masers G359.94+0.17 and G6.05−1.45 (M8E) and 13 of the EGOs were not detected in the H2O line, with 3σ upper limits of ∼6−7 Jy. Spectra and maser-emission parameters are given for the detected H2O masers, for some of which strong variability of the H2O maser emission was observed. The detected H2O masers, together with the Class I methanol masers and extended 4.5-μm emission, are associated with a very early stage in the development of young stellar objects in the regions of the EGOs. However, this sample of EGOs is not uniform. The presence of 44-GHz Class I methanol masers together with EGOs cannot be considered the only sign of early stages of star formation
Добавил в систему: Рудницкий Георгий Михайлович

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Observations of Extended Green Objects in the 1.35-cm H2O Line on the 22-m Pushchino Radio Telescopeстатья

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