\begin{table}%t2 \caption{\label{wat_tab}\label{tab2}Parameters of VLBA 22.2~GHz water maser features.} \small%\centering \par \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}{$V_{x}$} & \multicolumn{1}{c}{$V_{y}$} & \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 & 65.48 & 65.49 (2)& & $ -106.46\pm 0.23 $ & $ 132.43\pm0.44 $ & & $ -17.4\pm6.9 $ & $ 40.8\pm12.9$ & 27\% \\ 2 & 64.85 & 40.19 (4)& & $ -110.94\pm 0.18 $ & $ 142.62\pm0.18 $ & & ... & ... & ... \\ 3 & 65.06 & 27.55 (3)& & $ -108.89\pm 0.12 $ & $ 139.37\pm0.17 $ & & $ -23.3\pm5.5 $ & $ 42.8\pm7.8 $ & 15\% \\ 4 & 60.93 & 22.98 (1)& & $ 0 $ & $ 0 $ & & 0 & 0 & \\ 5 & 60.09 & 15.89 (1)& & $ 107.14\pm 0.10 $ & $ 109.94\pm0.19 $ & & $ -0.1\pm7.0 $ & $ 39.7\pm13.3$ & 33\% \\ 6 & 64.52 & 11.63 (1)& & $ -111.92\pm 0.12 $ & $ 143.40\pm0.11 $ & & $ -3.3\pm4.0 $ & $ 19.7\pm4.4 $ & 22\% \\ 7 & 64.42 & 4.24 (4)& & $ -107.50\pm 0.09 $ & $ 131.83\pm0.11 $ & & $ -10.6\pm5.7 $ & $ 43.1\pm6.6 $ & 15\% \\ 8 & 61.48 & 3.30 (4)& & $ 230.00\pm 0.10 $ & $ 685.88\pm0.18 $ & & $ -7.2\pm7.0 $ & $ 35.4\pm11.7$ & 32\% \\ 9 & 51.36 & 2.70 (4)& & $ 256.26\pm 0.16 $ & $ 695.78\pm0.17 $ & & $ -1.8\pm8.5 $ & $ 55.3\pm8.1 $ & 15\% \\ 10 & 59.25 & 2.56 (1)& & $ 229.96\pm 0.13 $ & $ 685.76\pm0.20 $ & & ... & ... & ... \\ 11 & 62.62 & 1.72 (1)& & $ -111.69\pm 0.09 $ & $ 120.16\pm0.10 $ & & ... & ... & ... \\ 12 & 64.42 & 1.70 (4)& & $ -105.56\pm 0.08 $ & $ 137.21\pm0.10 $ & & ... & ... & ... \\ 13 & 66.11 & 1.67 (3)& & $ -116.31\pm 0.09 $ & $ 156.20\pm0.10 $ & & $ -10.9\pm6.0 $ & $ 43.5\pm8.5 $ & 19\% \\ 14 & 60.84 & 1.48 (3)& & $ 235.32\pm 0.08 $ & $ 673.64\pm0.10 $ & & $ -11.8\pm5.4 $ & $ 19.7\pm6.1 $ & 26\% \\ 15 & 61.26 & 1.31 (2)& & $ 107.55\pm 0.07 $ & $ 111.31\pm0.09 $ & & ... & ... & ... \\ 16 & 60.63 & 1.11 (3)& & $ 0.56\pm 0.14 $ & $ -1.27\pm0.13 $ & & ... & ... & ... \\ 17 & 66.74 & 0.87 (4)& & $ -115.99\pm 0.09 $ & $ 153.86\pm0.21 $ & & ... & ... & ... \\ 18 & 65.06 & 0.80 (3)& & $ -118.02\pm 0.11 $ & $ 153.03\pm0.18 $ & & ... & ... & ... \\ 19 & 61.90 & 0.79 (4)& & $ -108.63\pm 0.13 $ & $ 131.99\pm0.17 $ & & ... & ... & ... \\ 20 & 66.42 & 0.72 (1)& & $ -106.92\pm 0.10 $ & $ 129.23\pm0.18 $ & & ... & ... & ... \\ 21 & 65.48 & 0.71 (4)& & $ 106.92\pm 0.08 $ & $ 110.26\pm0.09 $ & & ... & ... & ... \\ 22 & 59.58 & 0.64 (4)& & $ 152.99\pm 0.09 $ & $ 1.63\pm0.10 $ & & $ 9.3\pm3.5 $ & $ 11.7\pm4.2 $ & 27\% \\ 23 & 67.89 & 0.57 (1)& & $ -115.27\pm 0.09 $ & $ 146.15\pm0.09 $ & & ... & ... & ... \\ 24 & 62.53 & 0.51 (4)& & $ -112.30\pm 0.08 $ & $ 126.55\pm0.09 $ & & ... & ... & ... \\ 25 & 66.74 & 0.49 (2)& & $ -115.84\pm 0.08 $ & $ 157.32\pm0.12 $ & & $ -27.4\pm5.0 $ & $ 113.8\pm7.6 $ & 6\% \\ 26 & 64.10 & 0.46 (1)& & $ -106.47\pm 0.10 $ & $ 137.54\pm0.12 $ & & ... & ... & ... \\ 27 & 66.32 & 0.45 (3)& & $ -117.63\pm 0.08 $ & $ 162.42\pm0.12 $ & & ... & ... & ... \\ 28 & 65.48 & 0.40 (2)& & $ 107.06\pm 0.09 $ & $ 109.40\pm0.10 $ & & ... & ... & ... \\ 29 & 62.74 & 0.39 (3)& & $ -112.00\pm 0.09 $ & $ 118.35\pm0.14 $ & & ... & ... & ... \\ 30 & 60.30 & 0.35 (1)& & $ 6.92\pm 0.09 $ & $ 12.23\pm0.12 $ & & $ 4.9\pm3.6 $ & $ 20.4\pm4.6 $ & 21\% \\ 31 & 60.63 & 0.34 (4)& & $ 107.16\pm 0.11 $ & $ 111.54\pm0.18 $ & & ... & ... & ... \\ 32 & 62.20 & 0.33 (1)& & $ -109.48\pm 0.19 $ & $ 128.05\pm0.20 $ & & ... & ... & ... \\ 33 & 60.84 & 0.25 (4)& & $ 5.81\pm 0.09 $ & $ 10.10\pm0.14 $ & & ... & ... & ... \\ 34 & 60.84 & 0.21 (3)& & $ -8.41\pm 0.09 $ & $ 13.03\pm0.20 $ & & ... & ... & ... \\ 35 & 62.32 & 0.21 (4)& & $ -111.81\pm 0.08 $ & $ 120.87\pm0.12 $ & & ... & ... & ... \\ 36 & 63.46 & 0.18 (1)& & $ -107.52\pm 0.10 $ & $ 131.67\pm0.13 $ & & ... & ... & ... \\ 37 & 60.09 & 0.16 (1)& & $ 106.91\pm 0.10 $ & $ 119.47\pm0.15 $ & & ... & ... & ... \\ 38 & 58.61 & 0.10 (1)& & $ 228.34\pm 0.10 $ & $ -31.43\pm0.18 $ & & $ 12.8\pm4.3 $ & $ 10.4\pm7.0 $ & 34\% \\ 39 & 63.04 & 0.10 (1)& & $ 264.41\pm 0.11 $ & $ 684.83\pm0.15 $ & & ... & ... & ... \\ 40 & 60.00 & 0.10 (3)& & $ 108.53\pm 0.09 $ & $ 113.03\pm0.15 $ & & ... & ... & ... \\ \hline \multicolumn{10}{c}{Reference Feature: Absolute position}\\ \hline \noalign{\smallskip} Feature & \multicolumn{4}{c}{RA(J2000)} & \multicolumn{4}{c}{ Dec(J2000) } & \\ & \multicolumn{4}{c}{(h m s)} & \multicolumn{4}{c}{(\degr $'$ $''$)} & \\ \hline\noalign{\smallskip} 4 &\multicolumn{4}{c}{18:21:09.09211~$\pm$~0.00009}&\multicolumn{4}{c}{$-$14:31.48.6790~$\pm$~0.0023} & \\ \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~\#~4, in the east and north directions, respectively. Columns~6 and~7 report the projected components of the feature proper motion relative the the feature~\#~4, along the east and north directions, respectively. Column~8 shows the relative error of the proper motion amplitude. The absolute position of the reference feature~\#~4 is reported at the bottom of the table.} \end{table}