NDLI: Observations of Extended Green Objects in the 1.35-cm H$_{2}$O Line on the 22-m Pushchino Radio Telescope

Content Provider	Springer Nature Link
Author	Rudnitskii, G. M. Lekht, E. E. Bayandina, O. S. Val’tts, I. E. Khan, E. R.
Copyright Year	2016
Abstract	Observations of H$_{2}$O 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. H$_{2}$O 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 H$_{2}$O maser in the W44 region, G34.3+0.2. H$_{2}$O 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 H$_{2}$O line, with 3s upper limits of ~6-7 Jy. Spectra and maser-emission parameters are given for the detected H$_{2}$Omasers, for some of which strong variability of the H$_{2}$O maser emission was observed. The detected H$_{2}$Omasers, 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.
Starting Page	129
Ending Page	144
Page Count	16
File Format	PDF
ISSN	10637729
Journal	Astronomy Reports
Volume Number	60
Issue Number	1
e-ISSN	15626881
Language	English
Publisher	Pleiades Publishing
Publisher Date	2016-01-23
Publisher Place	Moscow
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Astronomy, Observations and Techniques
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
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