\begin{table}%t1
\caption{H$_2$O maser observations.}\label{rms}
%\centerline
$${
\begin{tabular}{l c c r c c r @{--}l r c c l @{\ } l}
\hline  \hline
Source              & RA       & Dec             & $V_{\rm sys}$    & Type$^{a}$      & $L_{\rm FIR}^{b}$     &  
\multicolumn{2}{c}{$V$--range}   & rms    & Channel & Epoch$^{c}$ & \multicolumn{2}{c}{$N_{\rm H}^{d}$}    \\
                    &            &                  &                  &                      & (log)                      &
\multicolumn{2}{c}{\ }           &                  &    Width         &                      &                      \\
                    &\multicolumn{2}{c}{($J$~2000)}&   (c$z$)         &                      &                            &
\multicolumn{2}{c}{(km~s$^{-1}$)}&  (mJy)          & (km~s$^{-1}$)   & & \multicolumn{2}{c}{($10^{23}$ cm$^{-2}$)}  \\
\hline 
NGC~1667           &04 48 37.1& $-$06 19 12 & 4547 &Sy 2  &  11.0 &   4000&5100 & 10 &1.1& 0205 & $\ge$10            & B; B99    \\
NGC~2273           &06 50 08.7&   +60 50 45 & 1840 &Sy 2  &  10.1 &   1400&2400 &  9 &1.1& 0105 & $\geq$18          & X; Gua05  \\
IRAS~07145--2914   &07 16 31.2& $-$29 19 29 & 1698 &Sy 2  &  10.0 &   1100&2200 & 77 &1.1& 1004 & $\ge$100           & B; B99    \\
                    &          &             &      &      &       &   1050&2200 & 35 &1.1& 0105 &                    &           \\
UGC~5101           &09 35 51.6&   +61 21 11 &11~809 &ULIRG &  11.9 &  10~550&12~800&  2 &4.2& 1004 & $13\pm 2$          & C; Arm04  \\ 
NGC~2992$^{e}$&09 45 42.0& $-$14 19 35 & 2311 &Sy 1.9&\nodata&   1770&2900 & 11 &1.1& 0205 & $\sim$0.1          & B; Gua05  \\
NGC~3393           &10 48 23.4& $-$25 09 43 & 3750 &Sy 2  &  10.4 &   2880&4800 & 14 &4.2& 0105 & $44^{+25}_{-11}$   & X; Gua05  \\
IRAS~11058--1131   &11 08 20.3& $-$11 48 12 &16~437 &Sy 2  &  11.2 &  15~500&17~500&  7 &4.2& 0105 & $>$100             & B; Ris00  \\
NGC~4418           &12 26 54.6& $-$00 52 39 & 2179 &Sy 2  &  10.9 &   1550&2900 & 33 &1.1& 1004 & $>$10              & C; Mai03  \\
Mrk~231            &12 56 14.2&   +56 52 25 &12~642 &ULIRG &  12.2 &  12~050&13~200&  7 &1.1& 0205 & $\sim$20           & X,B; Bra04\\
NGC~4939$^{e}$&13 04 14.4& $-$10 20 23 & 3110 &Sy 2  &  10.3 &   2500&3770 &  8 &1.1& 0105 & $\rm 1.5^{+0.4}_{-0.5}$& X; Gua05  \\
                    &          &             &      &      &       &   2570&3700 & 11 &1.1& 0205 &                    &           \\
NGC~4968           &13 07 06.0& $-$23 40 37 & 2957 &Sy 2  &  10.2 &   2300&3660 & 30 &1.1& 1004 & $\ge$10            & B; B99    \\
NGC~5005$^{e}$&13 10 56.2&   +37 03 33 &  946 &LINER &  10.2 &    400&1550 & 10 &1.1& 0205 & $>$10              & B; Ris99  \\
                    &          &             &      &      &       &\multicolumn{2}{c}{\ }& & &  & $0.3^{+0.2}_{-0.2}$& X; Gua05  \\
Mrk~668            &14 07 00.4&   +28 27 15 &22~957 &RL    &\nodata&  22~340&23~630&  9 &1.1& 1004 & $>$100             & X; Gua04  \\
Arp~220$^{e}$ &15 34 57.1&   +23 30 11 & 5434 &ULIRG &  12.1 &   5250&5720 & 13 &1.1& 0601 & 0.3                & C; Cle02  \\ 
NGC~6552           &18 00 07.3&   +66 36 54 & 7942 &Sy 2  &  11.0 &   7400&8500 &  9 &1.1& 1004 & $6\pm1$            & A; B99    \\
                    &          &             &      &      &       &   7400&8500 &  8 &1.1& 0205 &                    &           \\
TXS~1946+708       &19 45 53.5&   +70 55 49 &30~228 &RL    &\nodata&  29~000&31~650&  5 &4.2& 1004 & $>$28              & B; Ris03  \\
IRAS~20210+1121    &20 23 25.4&   +11 31 35 &16~905 &Sy 2  &  11.7 &  16~650&17~200&  8 &1.1& 0105 & $\le$0.6           & B; Delu04 \\
NGC~7674           &23 27 56.7&   +08 46 45 & 8671 &Sy 2  &  11.5 &   8100&9380 & 19 &1.1& 0105 & $\ge$100           & B; B99    \\
\hline
\end{tabular}}$$

\medskip
$^a$ LINER = Low Ionization Nuclear Emission Line Region; RL~= Radio Loud; Sy~= Seyfert; ULIRG~= UltraLuminous InfraRed Galaxy. \\
$^b$ Infrared flux densities taken from the IRAS Point Source Catalog (Fullmer \& Lonsdale \cite{Ful89}) or from NED were converted into far infrared luminosities following the procedure outlined by Wouterloot \& Walmsley (\cite{Wou86}); $H_0$~= 75~km~s$^{-1}$~Mpc$^{-1}$;  the values given are the logarithms of the infrared luminosity in solar units. \\
$^c$ Month (first two digits) and year (last two digits). \\ 
$^d$ Notes concerning X-ray absorbing hydrogen column densities:  X-ray telescope: A: {\it ASCA}; B: {\it BeppoSAX}; C: {\it Chandra}; X: {\it XMM-Newton};  References: Arm04: Armus et~al. (\cite{Arm04}); B99: Bassani et~al. (\cite{B99}); Bra04: Braito et~al. (\cite{Bra04b}); Cle02: Clements et~al. (\cite{Cle02}); Delu04: Deluit (\cite{Delu04}); Gua04: Guainazzi et~al. (\cite{Guao4a}); Gua05: Guainazzi et~al. (\cite{Gua05a}); Mai03: Maiolino et~al. (\cite{Mai03}); Ris99: Risaliti et~al. (\cite{Ris99}); Ris00: Risaliti et~al. (\cite{Ris00}); Ris03: Risaliti et~al. (\cite{Ris03}). \\
$^e$ NGC~2992: a revived AGN according to Gilli et~al. (\cite{Gil00}); NGC~4939: a~source varying from Compton-thick to Compton-thin, see Gua05;  NGC~5005: a possibly misclassified Compton-thin source from Gua05;  Arp~220: the column density from Cle02 refers to the western nucleus and is highly uncertain. 
\end{table}