The brightness temperature as a function of the (u, v)-distance, D. The green, square shows the minimum T_B and the cyan, triangle shows the limiting T_B. The yellow, square shows the T_B, min from five RadioAstron snapshot survey sessions close to our observation. The blue, horizontal lines show the T_B at model components C (dotted), J3 (dotted-broken), and J4 (broken). Note that a lower limit is reported for C, since its size is smaller than the resolution limit (see Sect. 3.2).