Structure of the H2O Maser in NGC 2071 IRS 1 from Observations on the Ground-Space Radio Interferometer RadioAstron

The observational data of an H2О maser at a frequency of 22.2280 GHz in the dark reflection nebula NGC 2071 in the direction of the infrared object IRS 1 at the target coordinates RA(2000) = $${{05}^{{\text{h}}}}{{47}^{{\text{m}}}}04_{.}^{{\text{s}}}758$$ , DEC(2000) = $$00{}^\circ 21' 42_{.}^{'' }700$$ have been processed as part of the scientific program of the ground-space interferometer RadioAstron. The duration of the session on January 11, 2014 was 70 min. The space radio telescope (SRT-10) and three radio telescopes of the ground-based network took part in the observations: RT-32 (Medicina, Italy), RT-32 (Torun, Poland), and RT-64 (Kalyazin, Russia). The following parameters were implemented: angular resolution 70 μs at the ground-space baseline with maximum baseline projections 3.1 ED ( $$ \sim {\kern 1pt} 40{\kern 1pt} {\kern 1pt} 000$$ km); synthesized beam of the ground-based part of the interferometer $$0.006'' \times 0.0006'' $$ (PA = –23°); spectral resolution 7.81 kHz (i.e., 0.11 km/s). A map of the distribution of maser spots with 13 spatial components was obtained. The map has a size $$ \sim {\kern 1pt} 100 \times 100$$ mas (milliarcseconds), which corresponds to $$ \sim 40 \times 40$$ AU at a distance of 390 pc to the nebula. The range of the line-of-sight velocities of the components is 4.7–20.5 km/s with a width of spectral features 0.2–0.6 km/s; the density of the correlated flux at the line maximum varies from $$ \sim {\kern 1pt} 4$$ to $$ \sim {\kern 1pt} 29$$ Jy. There was recorded one spatial component (with a radial velocity of 14.3 km/s) for which there was a correlation at the ground-space baselines SRT–Tr and SRT–Mc at an ultrahigh angular resolution with a reliability level above 6σ. Based on the analysis of the dependence of the visibility function on the baseline projections, a two-component model is proposed for the spatial structure of this component with the angular dimensions of the extended and compact constituents 4 mas and 0.06 mas, i.e., 1.56 AU (with an uncertainty of 10%) and 0.023 AU (with an uncertainty of 50%), respectively.