ИСТИНА

We report observations of H2O maser emission sources at a wavelength of 1.35 cm associated with regions of extended 4.5-μm emission coded ``green’’ in the Spitzer survey images (Extended Green Objects, EGOs). EGOs are considered as typical signposts of the regions of massive-star formation hosting high-velocity outflows of matter, methanol, water vapour, and hydroxyl masers. The observations were carried out on January 28-30 and February 25-27, 2015, on the 22-metre radio telescope of the Pushchino Radio Astronomy Observatory, Russia (e.g., Lekht et al. 2012, ARep 56, 45). The telescope beamwidth is 2.6’, and the detection limit was about 10 Jy. The sample of the targets included 24 EGOs north from declination -29o taken from the GLIMPSE survey of the Spitzer mission (Cyganowski et al. 2008, AJ 136, 2391) as well as one of the brightest Class I methanol masers G6.05-1.45 (M8E) and Class I methanol maser in the infrared dark cloud (IRDC) G359.94+0.17. The H2O emission was detected toward 11 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. Among them is the well-known H2O maser (G34.3+0.2) in the W44 region that we have been monitoring since 1979 (Lekht et al. 2012, ARep 56, 45). All the detected masers are in the sample of Cyganowski et al. (2013, ApJ 764, 61), who observed them in 2008-2010 on the Nobeyama 45-metre telescope in the H2O and NH3 lines at 22/23 GHz. The source G28.83-0.25 is a new detection. It was not detected in Cyganowski et al.’s observations (F < 0.17 Jy). It is also listed as a negative result (Fpeak < 15.9 Jy) by Palagi et al. (1993, A&Ap 101, 153). We saw H2O emission at 77.6 km/s with a flux density of ~19 Jy in January and ~16 Jy in February. Possibly we have caught the source at an early stage of shock wave propagation. The rest 13 EGOs, Class I methanol masers G359.94+0.17 and G6.05-1.45 (M8E) were not detected with a 3σ upper limit of ~6-7 Jy. For the detected H2O masers spectra and line parameters are presented. We have compared the measured spectra with those of Cyganowski et al., and we have found drastic changes in the H2O profiles since their epochs of observations. One source, G23.01-0.41, strongly changed its H2O line profile between our January and February 2015 observational sessions. Together with Class I methanol masers and extended 4.5-μm emission, H2O masers (if they are far from OH maser emission - see poster of Bayandina et al., this session) trace a very early phase of development of young stellar objects in these regions.