\begin{table}%t5
 \caption{Nuclear X-ray absorbing column densities of extragalactic H$_{2}$O~maser galaxies$^{*}$.}\label{coldensity}
%\centering
\par
\begin{tabular}{llclcl}
\hline \hline
 Source &  Type$^{a}$ & Telescope$^{b}$ &  Epoch$^{c}$   & $N_{\rm H}$            & References$^{d}$ \\
        &                 &                     &                    & (10$^{23}$~cm$^{-2}$) &                      \\
\hline
{\it IC~10}                    & X-1               & C & 2003.03.12 & $\rm 0.06^{+0.002}_{-0.0008}$ & BB04               \\
NGC~235A                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\ 
{\it NGC~253}                  & SBG               & B & 1996.11.29 & $\rm  0.12_{-0.04}^{+0.03}$    & Cap99b             \\ 
                                &                   & C & 1999.12.16 & $\rm  2.0^{+1.3}_{-0.9}$       & Wea02              \\
NGC~262 (Mrk~348)             & S2                & A & 1995       & $\rm 1.60_{-0.10}^{+0.20}$     & Ris02              \\
IRAS F01063--8034$^{e}$    & S2                & X & 2003.04.21 & see Sect.~4.2             &                    \\
NGC~449 (Mrk~1)               & S2                & A & 1996.08.06 & see Table 3                & TARTARUS           \\
{\it NGC~598 (M~33)}          &                   & A & 1993.07    & $\rm 0.016^{+0.002}_{-0.002}$  & Tak94              \\
                                & X-8               & X & 2000--2002 & $\rm 0.019^{+0.005}_{-0.005}$  & Fos04              \\
NGC~591                        & S2                & A & 1997.07.28 & see Table 3                & TARTARUS           \\
NGC~613                        & S                 & R & \nodata    & see Table 3                & HEASARC            \\ 
IC~184                         & S2                & R & \nodata    & see Table 3                & HEASARC            \\ 
NGC~1052                       & LINER             & A & 1996.08    & $\rm  2.0_{-0.83}^{+0.79}$     & Ter02              \\
                                &                   & X & 2001.08.15 & $\sim$7                    & Kad06              \\
NGC~1068                       & S2, C             & A & 1993.07.24 & $>$100                     & B99, Iwa97         \\ 
                                &                   & B & 1996, 1998 & $>$100	                  & Mat97, Gua99       \\ 
                                &                   & C & 2000.02.21 & $>$100	                  & Mat04              \\ 
                                &                   & X & 2000.07.29 & $>$100                     & Mat04	\\ 
Mrk~1066                       & S2, C             & A & 1997.07.24 & $>$10	                 & Ris99              \\
NGC~1386                       & S2, C             & B & 1996.12.10 & $>$10	                 & Mai98              \\ 
                                &                   & X & 2002.12.29 & $\geq$22                  & Gua05              \\ 
{\it IC~342}                   &                   & A & 2000.02.24 & $\rm 0.084^{+0.042}_{-0.042}$  & Kub02              \\
                                & X-21              & X & 2001.02.11 & $\rm 0.087^{+0.013}_{-0.025}$  & Kon03              \\
UGC~3255                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\
Mrk~3                          & S2, C             & A & 1993       & $\rm 13^{+22}_{-6}$            & Tur97b             \\
                                &                   & B & 1997.04.16 & $\rm 12.7^{+2.4}_{-2.2}$       & Cap99a, Matt00     \\
                                &                   & X & 2000.10.19 & $\rm 13.6^{+0.3}_{-0.4}$       & Bia05              \\
{\it NGC~2146}                 & SBG               & A & 1997.03.26 & $\rm 0.021^{+0.022}_{-0.011}$  & Del99              \\
VII~ZW 73                      & S2                & R & \nodata    & see Table 3                & HEASARC            \\
{\it NGC~2273}                 & S2, C             & B & 1997.02.12 & $>$100                     & Mai98              \\
                                &                   & X & 2003.09.05 & $\geq$18                  & Gua05              \\  
Mrk~78                         & S2                & R & \nodata    & see Table 3                & HEASARC            \\
Mrk~1210                       & S2, C?            & A & 1995       & $>$10                      & B99                \\
                                &                   & B & 2001.05.05 & $\rm 1.83^{+0.08}_{-0.12}$     & Ohno04             \\
                                &                   & X & 2001.05.05 & $\rm 2.14^{+0.20}_{-0.16}$     & Gua02b             \\
J0804+3607                      & Type 2 Quasar     & R & \nodata    & see Table 3                & HEASARC            \\     
NGC~2639                       & LINER             & A & 1997.04.16 & $\rm 4.2^{+5.6}_{-2.3}$        & B99, Wil98         \\
NGC~2782$^{e}$            & SBG, C            & C & 2002.05.17 & $>$10                      & this paper         \\
NGC~2824 (Mrk~394)            & S2                & R & \nodata    & see Table 3                & HEASARC            \\
NGC~2960 (Mrk~1419)           & LINER             & R & \nodata    & see Table 3                & HEASARC            \\
UGC~5101                       & ULIRG             & C & 2001.05.28 & 0.1 ($<$0.65)              & Ptak03             \\
                                &                   & C,X&2001       & $\rm 13^{+2}_{-2}$             & Arm04              \\
NGC~2979                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\
{\it NGC~3034 (M~82)$^{f}$}& SBG             & B & 1997.12.06 & $\rm 0.058^{+0.014}_{-0.015}$  & Cap99b             \\
                                &                   & X & 2001.05.06 & $\rm 0.017^{+0.018}_{-0.016}$  & Ste03              \\ 
                                &                   & C & 2002       & 0.012                      & Str04              \\ 
NGC~3079                       & S2/LINER, C?      & A & 1993.05.09 & $\rm 0.17^{+0.18}_{-0.12}$     & B99, Ter02         \\
                                &                   & B & 2000.05.26 & $\sim$100                 & Iyo01              \\ 
                                &                   & C & 2001.03.07 & $\rm 0.17^{+0.02}_{-0.02}$     & Cec02              \\   
Mrk~34                         & S2                & A & 1997.11.17 & see Table 3                & TARTARUS           \\
IC~2560                        & S2                & A & 1996.12.19 & $\sim$3                    & Ish01              \\
                                &                   & C & 2000.10.29 & $>$10                      & Iwa02              \\
                                &                   &C  & 2004.02.16 & $\ga$30                    & Mad06              \\
\hline
NGC~3393                         & S2, C             & X & 2003.01.05 & $\rm 44^{+25}_{-11}$           & Gua05              \\
{\it NGC~3556}                   & X-35              & C & 2001.09.08 & $\rm 0.03^{+0.017}_{-0.009}$   & Wang03             \\   
Arp~299 (NGC~3690)            & SBG, C            & X & 2001.05.06 & $\sim$26                  & Ball04             \\
                                &                   & C & 2001.07.13 & $\rm 25^{+4.4}_{-2.5}$         & Zez03              \\  
                                &                   & B & 2001.12.14 & $\rm 25.2^{+1.39}_{-0.56}$     & Del02              \\ 
NGC~3735                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\
{\it NGC~4051}                 & S1/1.5            & A & 1993.04.25 & $\rm 0.045_{-0.035}^{+0.035}$  & Geo98              \\
                                &                   & C & 2000.04.25 & $\sim$0.01                & {\rm Col01}        \\
                                &                   & X & 2001.05.16 & $\sim$3.6                 & Pou04              \\
{\it NGC~4151}                 & S1.5              & A & 1993.12.07 & $\rm 0.635_{-0.035}^{+0.041}$  & Geo98              \\
                                &                   & A,B& 1999-2000 & $\rm 2.0^{+0.1}_{-0.1}$        & Sch02a             \\
NGC~4258                       & S1.9              & A & 1999.05.15 & $\rm 0.95^{+0.21}_{-0.09}$     & Rey00              \\ 
                                &                   & B & 1998.12.19 & $\rm 1.21^{+0.07}_{-0.06}$     & Ris02              \\
                                &                   & C & 2000--2001 & $\sim$0.7                 & You04              \\ 
                                &                   & X & 2000.12.08 & $\rm 0.80^{+0.04}_{-0.04}$     & Pie02              \\
                                &                   &X,C& 2000-2002  & $\sim$1.0                 & Fru05              \\
{\it NGC~4293}                 & LINER             & R & \nodata    & see Table 3                & HEASARC            \\ 
NGC~4388                       & S2                & A & 1995.07.21 & $\rm 3.34^{+1.00}_{-0.90}$     & For99              \\ 
                                &                   & B & 2000.01.03 & $\rm 4.80^{+1.80}_{-0.80}$     & Ris02              \\
                                &                   & X & 2002.12.12 & $\rm 2.79^{+0.07}_{-0.07}$     & Bec04              \\ 
                                &                   & C & 2001.06.08 & $\rm 3.5^{+0.4}_{-0.3}$        & Iwa03              \\
ESO~269-G012$^{e}$        & S2                & C & 2004.01.05 & see Sect. 4.2             &                    \\
NGC~4922           & S2                & C & 2004.11.02 & see Sect. 4.2             &                    \\
NGC~4945                       & S2, C             & A & 1993.08.31 & $\rm 40^{+2.0}_{-1.2}$         & B99, Don96         \\
                                &                   & B & 1999.07.01 & $\rm 22^{+3}_{-4}$             & Gua00              \\
{\it NGC~5194 (M~51)}         & S2, C             & A & 1993.05.11 & $\rm 7.5^{+2.5}_{-2.5}$        & B99,Ter98          \\
                                &                   & B & 2000.01.18 & $\rm 56^{+40}_{-16}$           & Fuk01              \\
NGC~5256 (Mrk~266)            & S2                & A & 1999.05    & $\rm 0.16^{+0.33}_{-0.15}$     & Lev01              \\
NGC~5347                       & S2, C             & A & 1997       & $>$10                      & Ris99              \\
NGC~5495                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\
Circinus                        & S2, C             & A & 1995.08.14 & $>$10                      & B99, Mat96         \\
                                &                   & B & 1998.03.13 & $\rm 43^{+4}_{-7}$             & Mat99              \\
                                &                   & C & 2000.06.06 & $\sim$60                  & Sam01              \\
NGC~5506 (Mrk1376)             & S1?               & B & 1998.01.14 & $\rm 0.37^{+0.05}_{-0.05}$     & Ris02              \\
NGC~5643                       & S2, C             & B & 1997.03.01 & $>$100                     & Mai98, B99         \\
                                &                   & X & 2003.02.08 & 6$-$10                     & Gua04              \\  
NGC~5728$^{e}$            & S2                & C & 2003.05.27 & $\rm 7.7^{+0.55}_{-0.51}$      & this paper         \\
NGC~5793                       & S2                & A & 1998.08.05 & see Table 3                & TARTARUS           \\
NGC~6240                       & ULIRG, C          & A & 1994.03.27 & $>$20                      & Iwa98              \\
                                &                   & B & 1998.08.15 & $\rm 21.8^{+4.0}_{-2.7}$         & Vig99            \\ 
                                &                   & X & 2000.09.22 & $\rm 10.0^{+3.0}_{-3.0}$       & Bol03              \\
                                &                   & X & 2001.07.29 & $\rm 13.0^{+17.0}_{-8.0}$      & Ptak03             \\   
{\it NGC~6300}                 & S2, C?            & RX& 1997.02    & $>$100                     & Lei99              \\
                                &                   & B & 1999.08    & $\rm 2.10^{+0.10}_{-0.10}$     & Gua02a             \\
                                &                   & X & 2001.03.02 & $\rm 2.15^{+0.08}_{-0.09}$     & Mats04             \\ 
NGC~6323                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\  
ESO~103-G035                   & S2                & A & 1996.03.18 & $\rm 2.16^{+0.26}_{-0.25}$     & For99              \\
                                &                   & B & 1997.10.14 & $\rm 2.02^{+0.28}_{-0.28}$     & Wil01              \\
IRAS F19370--0131               & S2                & R & \nodata    & see Table 3                & HEASARC            \\
3C~403                         & FRII              & C & 2002.12.07 & $\rm 4.00^{+0.20}_{-0.20}$     & Kra05              \\
NGC~6926                       & S2                & R & \nodata    & see Table 3                & HEASARC            \\
AM2158-380NED02                 & S2                & R & \nodata    & see Table 3                & HEASARC            \\
TXS~2226-184                   & LINER             & A & 1997.11.21 & see Table 3                & TARTARUS           \\   
\hline
IC~1481                        & LINER             & A & 1997.11.28 & see Table 3                & TARTARUS           \\
\hline
\end{tabular}
\medskip
$^{*}$ {\it Chandra} and {\it XMM-Newton} results are given whenever possible. For sources not observed by these satellites most recent (but usually older) results  are quoted. Sources in italics: kilomaser sources. \\
$^a$ Type of nuclear activity. In the absence of a starburst and a prominent nuclear source, the X-ray source (e.g. X-1 or X-8) is 
given. SBG: StarBurst Galaxy; S2: Seyfert~2; LINER: Low-Ionization Nuclear Emission Line Region; ULIRG: UltraLuminous InfraRed 
Galaxy; FRII: Fanarov-Riley Type~II galaxy; C: Compton-thick, i.e. $N_{\rm H}$~$\ga$ 10$^{24}~{\rm cm}^{-2}$; C?: {possibly varying} between Compton-thick and Compton-thin.
 \\
$^b$ A: {\it ASCA}; B: {\it BeppoSAX}; C: {\it Chandra}; R: {\it ROSAT}; RX: {\it RXTE}; X: {\it XMM-Newton}. \\ 
$^c$ Year, month and day. \\
$^d$ Arm04: Armus et~al. (\cite{Arm04});
Ball04: Ballo et~al. (\cite{Ball04}); 
B99: Bassani et~al. (\cite{B99}); 
BB04: Bauer \& Brandt (\cite{BB04}); 
Bec04: Beckmann et~al. (\cite{Bec04});
Bia03: Bianchi et~al. (\cite{Bia03});
Bia05: Bianchi et~al. (\cite{Bia05});
Bol03: Boller et~al. (\cite{Bol03});
Cap99a: Cappi et~al. (1999);
Cap99b: Cappi et~al. (1999); 
Cec02: Cecil et~al. (\cite{Cel02});
Col01: Collinge et~al. (\cite{Col01});
Del99: Della~Ceca et~al. (\cite{Del99});
Del02: Della Ceca et~al. (\cite{Del02}); 
Don96: Done et~al. (\cite{Don96});
For99: Forster et~al. (\cite{For99});
Fos04: Foschini et~al. (\cite{Fos04});
Fru05: Fruscione et~al. (\cite{Fru05})
Fuk01: Fukazawa et~al. (\cite{Fuk01});
Geo98: George et~al. (\cite{Geo98}); 
Gua99: Guainazzi et~al. (\cite{Gua99}); 
Gua00: Guainazzi et~al. (\cite{Gua00});
Gua02a: Guainazzi (\cite{Gua02b}); 
Gua02b: Guainazzi et~al. (\cite{Gua02a}); 
Gua04: Guainazzi et~al. (\cite{Gua04b}); 
Gua05: Guainazzi et~al. (\cite{Gua05a});
Ish01: Ishihara et~al. (\cite{Ish01});
Iwa97: Iwasawa et~al. (\cite{Iwa97});
Iwa98: Iwasawa \& Comastri (\cite{Iwa98});
Iwa02: Iwasawa et~al. (\cite{Iwa02});
Iwa03: Iwasawa et~al. (\cite{Iwa03});
Iyo01: Iyomoto et~al. (\cite{Iyo01}); 
Kad06: Kadler et~al. (2006), in prep.;
Kon03: Kong (\cite{Kon03}); 
Kra05: Kraft et~al. (\cite{Kra05});
Kub02: Kubota et~al. (\cite{Kub02});
Lei99: Leighly et~al. (\cite{Lei99});
Lev01: Levenson et~al. (\cite{Lev01});
Mad06: Madejski et~al. (\cite{Mad06});
Mai98: Maiolino et~al. (\cite{Mai98});
Mat96: Matt et~al. (\cite{Mat96}); 
Mat97: Matt et~al. (\cite{Mat97});
Mat99: Matt et~al. (\cite{Mat99}); 
Mat00: Matt et~al. (\cite{Mat00}); 
Mat04: Matt et~al. (\cite{Mat04});
Mats04: Matsumoto et~al. (\cite{Mats04});
Mil90: Miller \& Goodrich (\cite{Mil90});
Ohno04: Ohno et~al. (\cite{Ohno04});
Per98: Persic et~al. (\cite{Per98}); 
Pie02: Pietsch et~al. (2002);
Pou04: Pounds et~al. (\cite{Pou04}); 
Ptak03: Ptak et~al. (\cite{Ptak03});
Rey00: Reynolds et~al. (\cite{Rey00});
Ris99: Risaliti et~al. (\cite{Ris99}); 
Ris02: Risaliti et~al. (\cite{Ris02});
Sam01: Sambruna et~al. (\cite{Sam01});
Sch02a: Schurch et~al. (\cite{Sch02a}); 
Sch02b: Schurch et~al. (\cite{Scho2b}); 
Smi96: Smith \& Done (\cite{Smi96});
Ste03: Stevens et~al. (\cite{Ste03});
Str04: Strickland et~al. (\cite{Str04}); 
Tak94: Takano et~al. (\cite{Tak94})
Ter98: Terashima et~al. (\cite{Ter98}); 
Ter02: Terashima et~al. (\cite{Ter02}); 
Tur97a: Turner et~al. (\cite{Tur97a}); 
Tur97b: Turner et~al. (\cite{Tur97b}); 
Vig99: Vignati et~al. (\cite{Vig99});
Wang03: Wang et~al. (\cite{Wang03});
Wea02: Weaver et~al. (\cite{Wea02});
Wil01: Wilkes et~al. (\cite{Wil01}); 
Wil98: Wilson et~al. (\cite{Wil98});
You04: Young \& Wilson (\cite{You04});
Zez03: Zezas et~al. (\cite{Zez03}). \\
$^e$ Absorbing column densities were obtained by processing {\it XMM-Newton} and {\it Chandra} Archive data (see Sect.~4.2). \\
$^f$ For NGC~3034 (M~82), lacking a well defined nucleus, the {\it Chandra} data refer to the diffuse halo component. \\
%$^g$ {\it Chandra} archive data have not yet been released.
\end{table}