\begin{table} \caption{\label{wat_tab}Parameters of VLBA 22.2~GHz water maser features.} \begin{tabular}{ccrcrrcrrr} \hline \hline \noalign{\smallskip} Feature & $V_{\rm LSR}$ & \multicolumn{1}{c}{$F_{\rm peak}$} & & \multicolumn{1}{c}{$\Delta x$} & \multicolumn{1}{c}{$\Delta y$} & & \multicolumn{1}{c}{$V_{\rm x}$} & \multicolumn{1}{c}{$V_{\rm y}$} & \multicolumn{1}{c}{$\Delta|V|/|V| $} \\ & (km s$^{-1}$) & \multicolumn{1}{c}{(Jy beam$^{-1}$)} & & \multicolumn{1}{c}{(mas)} & \multicolumn{1}{c}{(mas)} & & \multicolumn{1}{c}{(km s$^{-1}$)} & \multicolumn{1}{c}{(km s$^{-1}$)} & \\ \hline 1 & 72.58 &202.89 (4)& & $ -64.38 \pm 0.10 $ & $ -60.45 \pm 0.11 $& & $ -10.8 \pm 3.5$ & $ 3.0 \pm 3.6$ & 31\% \\ 2 & 78.48 &22.21 (3)& & $ 437.05 \pm 0.11 $ & $ 74.67 \pm 0.28 $& & $ 11.6 \pm 3.5$ & $-18.1 \pm6.3 $ & 26\% \\ 3 & 79.32 &19.68 (3)& & $ 437.16 \pm 0.10 $ & $ 73.42 \pm 0.14 $& & $ 10.0 \pm 3.5$ & $ -0.0 \pm 5.0$ & 36\% \\ 4 & 75.95 &15.70 (1)& & $ 425.22 \pm 0.10 $ & $ 159.39 \pm 0.12 $& & $ 9.4 \pm 3.4$ & $ -0.1 \pm 4.3$ & 37\% \\ 5 & 73.21 &12.70 (1)& & $ -61.49 \pm 0.26 $ & $ -76.84 \pm 0.14 $& & $ -22.3 \pm11.7$ & $-42.8 \pm 8.1$ & 19\% \\ 6 & 79.32 & 9.44 (3)& & $ -60.71 \pm 0.08 $ & $ -77.23 \pm 0.09 $& & $ -51.0 \pm 4.6$ & $-30.3 \pm 5.1$ & 8\% \\ 7 & 78.26 & 9.21 (1)& & $ 425.12 \pm 0.10 $ & $ 158.45 \pm 0.13 $& & $ 10.5 \pm 3.6$ & $-26.0 \pm 4.5$ & 16\% \\ 8 & 69.00 & 7.75 (1)& & $ -65.47 \pm 0.10 $ & $ -60.76 \pm 0.12 $& & ... & ... & ... \\ 9 & 66.47 & 5.14 (4)& & $ -66.17 \pm 0.13 $ & $ -60.82 \pm 0.12 $& & $ 3.4 \pm 4.2$ & $ -5.3 \pm 3.5$ & 60\% \\ 10 & 61.83 & 5.08 (4)& & $ -53.18 \pm 0.10 $ & $ -54.25 \pm 0.12 $& & $ -26.3 \pm 4.0$ & $ 3.5 \pm 4.1 $ & 15\% \\ 11 & 77.63 & 5.08 (2)& & $ -59.60 \pm 0.12 $ & $ -77.20 \pm 0.12 $& & $ 1.8 \pm 7.0$ & $-45.5 \pm 8.3$ & 18\% \\ 12 & 72.57 & 4.92 (1)& & $ -65.17 \pm 0.10 $ & $ -60.67 \pm 0.14 $& & ... & ... & ... \\ 13 & 76.58 & 4.82 (4)& & $ 425.18 \pm 0.10 $ & $ 158.79 \pm 0.11 $& & $ 5.9 \pm 3.3$ & $ -3.6 \pm 4.4$ & 53\% \\ 14 & 66.05 & 4.76 (3)& & $ -53.84 \pm 0.10 $ & $ -54.65 \pm 0.11 $& & $ -22.3 \pm 3.5$ & $ 4.1 \pm 4.2 $ & 16\% \\ 15 & 76.37 & 4.17 (3)& & $ -53.29 \pm 0.09 $ & $ -30.59 \pm 0.13 $& & ... & ... & ... \\ 16 & 72.58 & 3.86 (1)& & $ -62.93 \pm 0.09 $ & $ -60.06 \pm 0.11 $& & ... & ... & ... \\ 17 & 77.21 & 3.06 (4)& & $ -61.51 \pm 0.08 $ & $ -78.62 \pm 0.09 $& & ... & ... & ... \\ 18 & 74.26 & 2.80 (2)& & $ -59.39 \pm 0.11 $ & $ -77.00 \pm 0.14 $& & $ -4.2 \pm 7.0$ & $-46.0 \pm 9.2$ & 20\% \\ 19 & 78.90 & 2.54 (4)& & $ -55.73 \pm 0.11 $ & $ -102.53 \pm 0.13 $& & ... & ... & ... \\ 20 & 75.10 & 2.37 (3)& & $ 32.66 \pm 0.08 $ & $ -14.48 \pm 0.09 $& & ... & ... & ... \\ 21 & 79.74 & 2.27 (3)& & $ 420.54 \pm 0.10 $ & $ 126.25 \pm 0.12 $& & $ 5.4 \pm 3.6$ & $ -2.5 \pm 3.7$ & 62\% \\ 22 & 56.99 & 2.18 (1)& & $ -52.03 \pm 0.10 $ & $ -53.90 \pm 0.13 $& & ... & ... & ... \\ 23 & 78.69 & 2.10 (1)& & $ -52.17 \pm 0.15 $ & $ -31.90 \pm 0.18 $& & ... & ... & ... \\ 24 & 71.52 & 1.95 (2)& & $ 0 $ & $ 0 $& & $ 0 $ & $ 0 $ & ... \\ 25 & 78.26 & 1.72 (4)& & $ 435.51 \pm 0.10 $ & $ 77.83 \pm 0.13 $& & $ 6.0 \pm 3.6$ & $ -3.4 \pm 4.0$ & 54\% \\ 26 & 65.63 & 1.64 (1)& & $ -66.53 \pm 0.14 $ & $ -60.98 \pm 0.11 $& & $ -29.5 \pm 4.7$ & $12.9 \pm 4.1 $ & 14\% \\ 27 & 68.36 & 1.52 (1)& & $ -64.97 \pm 0.13 $ & $ -60.60 \pm 0.12 $& & ... & ... & ... \\ 28 & 81.21 & 1.43 (3)& & $ -62.98 \pm 0.08 $ & $ -77.14 \pm 0.09 $& & ... & ... & ... \\ 29 & 79.95 & 1.41 (4)& & $ -63.87 \pm 0.13 $ & $ -163.86 \pm 0.10 $& & $ -18.6 \pm 7.3$ & $-35.6 \pm 5.6$ & 15\% \\ 30 & 78.05 & 1.29 (1)& & $ -49.12 \pm 0.14 $ & $ -160.46 \pm 0.11 $& & $ -6.5 \pm 9.1$ & $-14.4 \pm10.9$ & 67\% \\ 31 & 72.37 & 1.09 (1)& & $ -62.09 \pm 0.09 $ & $ -76.67 \pm 0.11 $& & ... & ... & ... \\ 32 & 80.37 & 0.76 (4)& & $ -57.43 \pm 0.09 $ & $ -162.26 \pm 0.11 $& & ... & ... & ... \\ 33 & 79.53 & 0.75 (3)& & $ -32.44 \pm 0.10 $ & $ -29.99 \pm 0.12 $& & $ -4.5 \pm 3.4$ & $-12.4 \pm 3.7$ & 28\% \\ 34 & 80.79 & 0.71 (1)& & $ 425.21 \pm 0.10 $ & $ 158.23 \pm 0.11 $& & ... & ... & ... \\ 35 & 72.16 & 0.67 (1)& & $ -60.58 \pm 0.10 $ & $ -77.28 \pm 0.11 $& & ... & ... & ... \\ 36 & 78.48 & 0.59 (2)& & $ -49.46 \pm 0.08 $ & $ -161.70 \pm 0.13 $& & ... & ... & ... \\ 37 & 66.89 & 0.56 (1)& & $ -66.88 \pm 0.12 $ & $ -61.05 \pm 0.11 $& & ... & ... & ... \\ 38 & 80.58 & 0.55 (1)& & $ 437.41 \pm 0.10 $ & $ 67.80 \pm 0.15 $& & $ 11.4 \pm 7.2$ & $ -6.8 \pm10.8$ & 63\% \\ 39 & 75.32 & 0.49 (2)& & $ -548.55 \pm 0.09 $ & $ -314.11 \pm 0.11 $& & ... & ... & ... \\ 40 & 79.53 & 0.48 (2)& & $ -49.38 \pm 0.09 $ & $ -162.86 \pm 0.17 $& & ... & ... & ... \\ 41 & 76.79 & 0.44 (2)& & $ -548.30 \pm 0.09 $ & $ -314.13 \pm 0.09 $& & ... & ... & ... \\ 42 & 79.32 & 0.43 (4)& & $ -293.32 \pm 0.08 $ & $ -100.02 \pm 0.08 $& & ... & ... & ... \\ 43 & 67.94 & 0.42 (1)& & $ -53.79 \pm 0.09 $ & $ -54.67 \pm 0.11 $& & ... & ... & ... \\ 44 & 80.58 & 0.39 (1)& & $ -287.44 \pm 0.10 $ & $ -98.35 \pm 0.12 $& & $ -18.6 \pm 3.5$ & $ -1.5 \pm 3.8$ & 19\% \\ 45 & 88.59 & 0.38 (1)& & $ -64.55 \pm 0.13 $ & $ -162.29 \pm 0.12 $& & $ -7.6 \pm 8.2$ & $-34.9 \pm10.7$ & 30\% \\ 46 & 63.94 & 0.38 (4)& & $ -54.44 \pm 0.11 $ & $ -54.30 \pm 0.09 $& & ... & ... & ... \\ 47 & 80.16 & 0.36 (1)& & $ 440.10 \pm 0.10 $ & $ 58.11 \pm 0.16 $& & $ 18.7 \pm 7.1$ & $-26.3 \pm10.6$ & 30\% \\ 48 & 62.47 & 0.35 (4)& & $ -64.15 \pm 0.09 $ & $ -60.07 \pm 0.09 $& & ... & ... & ... \\ 49 & 79.32 & 0.33 (3)& & $ -293.50 \pm 0.10 $ & $ -100.37 \pm 0.12 $& & $ -8.8 \pm 3.5$ & $ -8.5 \pm 4.0$ & 31\% \\ 50 & 78.26 & 0.32 (2)& & $ -61.72 \pm 0.08 $ & $ -78.38 \pm 0.17 $& & ... & ... & ... \\ 51 & 62.25 & 0.31 (3)& & $ -54.39 \pm 0.10 $ & $ -54.57 \pm 0.10 $& & ... & ... & ... \\ 52 & 69.42 & 0.31 (1)& & $ -40.40 \pm 0.10 $ & $ -7.34 \pm 0.11 $& & ... & ... & ... \\ 53 & 79.74 & 0.31 (1)& & $ 284.39 \pm 0.10 $ & $ -55.26 \pm 0.12 $& & $ 0.2 \pm 4.0$ & $-18.3 \pm 4.9$ & 27\% \\ 54 & 77.21 & 0.30 (1)& & $ -58.94 \pm 0.10 $ & $ -77.13 \pm 0.13 $& & ... & ... & ... \\ 55 & 80.16 & 0.28 (1)& & $ 437.51 \pm 0.10 $ & $ 67.22 \pm 0.20 $& & ... & ... & ... \\ 56 & 76.16 & 0.27 (1)& & $ -103.16 \pm 0.10 $ & $ -150.22 \pm 0.12 $& & ... & ... & ... \\ 57 & 89.43 & 0.26 (1)& & $ -49.16 \pm 0.12 $ & $ -158.89 \pm 0.12 $& & ... & ... & ... \\ 58 & 71.95 & 0.23 (1)& & $ -67.77 \pm 0.10 $ & $ -61.37 \pm 0.11 $& & ... & ... & ... \\ 59 & 80.58 & 0.22 (4)& & $ -82.16 \pm 0.08 $ & $ -104.88 \pm 0.09 $& & ... & ... & ... \\ 60 & 77.42 & 0.21 (2)& & $ -546.43 \pm 0.08 $ & $ -314.43 \pm 0.10 $& & ... & ... & ... \\ 61 & 70.68 & 0.21 (2)& & $ -65.69 \pm 0.08 $ & $ -60.78 \pm 0.09 $& & ... & ... & ... \\ 62 & 77.21 & 0.20 (1)& & $ 418.75 \pm 0.10 $ & $ 92.99 \pm 0.12 $& & $ 5.8 \pm 3.8$ & $ -1.6 \pm 4.7$ & 64\% \\ 63 & 70.05 & 0.20 (3)& & $ 27.36 \pm 0.09 $ & $ -15.57 \pm 0.12 $& & ... & ... & ... \\ 64 & 59.51 & 0.19 (3)& & $ -57.57 \pm 0.09 $ & $ -63.38 \pm 0.11 $& & ... & ... & ... \\ 65 & 75.74 & 0.17 (3)& & $ -549.28 \pm 0.09 $ & $ -314.97 \pm 0.11 $& & ... & ... & ... \\ 66 & 81.63 & 0.16 (1)& & $ -70.96 \pm 0.10 $ & $ -88.63 \pm 0.13 $& & ... & ... & ... \\ 67 & 79.74 & 0.16 (3)& & $ -53.11 \pm 0.09 $ & $ -105.70 \pm 0.10 $& & ... & ... & ... \\ 68 & 70.89 & 0.16 (4)& & $ -51.85 \pm 0.09 $ & $ -73.26 \pm 0.10 $& & ... & ... & ... \\ 69 & 74.68 & 0.15 (4)& & $ 31.19 \pm 0.09 $ & $ -13.67 \pm 0.09 $& & ... & ... & ... \\ 70 & 70.89 & 0.14 (4)& & $ -38.58 \pm 0.09 $ & $ -53.28 \pm 0.09 $& & ... & ... & ... \\ 71 & 68.57 & 0.14 (4)& & $ -53.90 \pm 0.09 $ & $ -54.56 \pm 0.09 $& & ... & ... & ... \\ 72 & 67.31 & 0.13 (1)& & $ -63.71 \pm 0.10 $ & $ -60.09 \pm 0.14 $& & ... & ... & ... \\ 73 & 75.10 & 0.13 (1)& & $ 442.20 \pm 0.10 $ & $ 98.34 \pm 0.14 $& & ... & ... & ... \\ 74 & 75.74 & 0.12 (1)& & $ -51.19 \pm 0.10 $ & $ -68.44 \pm 0.16 $& & ... & ... & ... \\ 75 & 66.05 & 0.11 (3)& & $ -541.56 \pm 0.10 $ & $ -291.69 \pm 0.12 $& & ... & ... & ... \\ 76 & 79.53 & 0.11 (4)& & $ -51.08 \pm 0.09 $ & $ -160.20 \pm 0.10 $& & ... & ... & ... \\ 77 & 73.21 & 0.10 (1)& & $ -67.84 \pm 0.10 $ & $ -61.58 \pm 0.15 $& & ... & ... & ... \\ 78 & 81.00 & 0.09 (4)& & $ 412.27 \pm 0.09 $ & $ 171.84 \pm 0.10 $& & ... & ... & ... \\ 79 & 73.84 & 0.09 (2)& & $ -68.81 \pm 0.09 $ & $ -61.71 \pm 0.15 $& & ... & ... & ... \\ 80 & 76.16 & 0.09 (3)& & $ -540.64 \pm 0.09 $ & $ -267.93 \pm 0.14 $& & ... & ... & ... \\ 81 & 77.21 & 0.09 (1)& & $ 419.08 \pm 0.10 $ & $ 168.99 \pm 0.13 $& & ... & ... & ... \\ 82 & 71.94 & 0.09 (3)& & $ -99.30 \pm 0.09 $ & $ -173.21 \pm 0.11 $& & ... & ... & ... \\ 83 & 69.42 & 0.09 (1)& & $ -68.13 \pm 0.11 $ & $ -61.87 \pm 0.15 $& & $ -26.8 \pm 8.2$ & $ 8.0 \pm 10.6$ & 30\% \\ 84 & 76.58 & 0.08 (1)& & $ -52.05 \pm 0.10 $ & $ -68.04 \pm 0.16 $& & ... & ... & ... \\ 85 & 63.73 & 0.08 (2)& & $ -53.41 \pm 0.09 $ & $ -54.35 \pm 0.14 $& & ... & ... & ... \\ 86 & 85.85 & 0.07 (4)& & $ -4.96 \pm 0.09 $ & $ -151.45 \pm 0.12 $& & ... & ... & ... \\ \hline \noalign{\smallskip} \multicolumn{10}{c}{Reference Feature: Absolute position \& Proper motion}\\ Feature & \multicolumn{3}{c}{RA(J2000)} & \multicolumn{3}{c}{ Dec(J2000) } & \multicolumn{1}{c}{$V_{\rm x}$} & \multicolumn{1}{c}{$V_{\rm y}$} & \multicolumn{1}{c}{$\Delta|V|/|V| $} \\ & \multicolumn{3}{c}{(h m s)} & \multicolumn{3}{c}{(\degr $'$ $''$)} & \multicolumn{1}{c}{(km s$^{-1}$)} & \multicolumn{1}{c}{(km s$^{-1}$)}& \\ \hline 24 &\multicolumn{3}{c}{18:34:40.28950 $\pm$ 0.00010}&\multicolumn{3}{c}{$-$09:00:38.2044 $\pm$ 0.0015}&$ 5.3 \pm 8.6 $&$ 21.3 \pm 8.6 $& 39\% \\ \hline \end{tabular} \tablefoot{For each identified feature, the label (given in Col.~1) increases with decreasing brightness. Columns~2 and~3 report the LSR velocity and brightness of the brightest spot (for the epoch specified by the number in brackets). Columns~4 and~5 give the position offset relative to the feature~\#24, in the east and north directions, respectively. Columns~6 and~7 report the projected components of the feature proper motion relative to the feature~\#24, along the east and north directions, respectively. Column~8 shows the relative error of the proper motion amplitude. The absolute position and proper motion of the reference feature~\#24 are reported at the bottom of the table.} \end{table}