\begin{table}%t1
\caption{\label{tab1}The basic properties of the 27 combined spectra.
Columns~(1)$-$(6) refer to the counting number, 
the label for the mass bin (marked in Fig.~1), 
the mass bin, the average
{\it EW}([O~{\sc ii}]$\lambda$3727) of the sample galaxies in each
bin, the total number of the galaxies, and
the number of the selected spectra to be combined (about half) in each bin,
respectively.
 }
\small%\centerline
{
\begin{tabular}{llllrr}
\hline
\hline
(1)  & (2) & (3) & (4) & (5) & (6) \\  
No. & Label  & Mass bin      & {\it EW}([O~{\sc ii}]) & Total  & Selected     \\
    &      & (log$~M_*$)     & average (\AA)       & number & number   \\ \hline
1  & m87   & $<$8.7          &  --78.72     &     378        &  149  \\
2  & m871  & 8.7--8.8          &  --73.73     &     339        &  158 \\
3  & m881  & 8.8--8.9          &  --71.53     &     533        &  228  \\
4  & m891  & 8.9--9.0          &  --65.51     &     797        &  341  \\
5  & m901  & 9.0--9.1          &  --62.24     &     1227       &  533   \\
6  & m911  & 9.1--9.2          &  --60.42     &     1470       &  593 \\
7  & m921  & 9.2--9.3          &  --57.76     &     1885       &  766  \\
8  & m931  & 9.3--9.4          &  --55.02     &     2428       & 1029  \\
9  & m9405 & 9.40--9.45        &  --52.80     &     1329       &  552 \\
10 & m94505 & 9.45--9.50       &  --51.31     &     1478       &  627  \\
11 & m9505 & 9.50--9.55        &  --50.41     &     1670       &  705  \\
12 & m95505 & 9.55--9.60       &  --48.14     &     1746       &  751 \\
13 & m9605 & 9.60--9.65        &  --46.58     &     1920       &  814  \\
14 & m96505 & 9.65--9.70       &  --45.11     &     2001       &  837  \\
15 & m9705  & 9.70--9.75       &  --43.72     &     2156       &  906 \\
16 & m97505 & 9.75--9.80       &  --42.17     &     2262       &  951 \\
17 & m9805  & 9.80--9.85       &  --40.21     &     2428       & 1010  \\
18 & m98505 & 9.85--9.90       &  --38.31     &     2841       & 1020 \\
19 & m9905  & 9.90--9.95       &  --35.94     &     2552       & 1025  \\
20 & m99505 & 9.95--10.0       &  --33.59     &     2605       & 1048  \\
21 & m10005 & 10.0--10.05      &  --33.22     &     2750       & 1076  \\
22 & m100505 & 10.05--10.10    &  --31.19     &     2814       & 1120 \\
23 & m1011   & 10.10--10.20    &  --29.12$^a$  &     5860       & 2145  \\
24 & m1021   & 10.20--10.30    &  --26.28$^a$  &     6004       & 1813 \\
25 & m1031   & 10.30--10.40    &  --23.79$^a$  &     6084       & 1417 \\
26 & m1041   & 10.40--10.50    &  --22.18$^a$  &     5973       & 1148 \\
27 & m1051   & 10.50--10.60    &  --20.72$^a$  &     5341       &  846  \\  
\hline
\end{tabular} }
\smallskip
$^a$ For the massive galaxies with log($M_*)>10$.10,
we select those with
stronger [O~{\sc ii}] emission-lines with {\it EW}([O~{\sc ii}]$)< -30$~\AA\
for spectral combination.
\end{table}