  In order to investigate the physical relationship between strong Ly-alpha
absorbers (logN_HI>20.0 cm^-2) such as damped Ly-alpha absorption systems
(DLAs) and young star-forming galaxies at high redshift, we have conducted
narrow-band observations of Ly-alpha emitters (LAEs) in a concentrated region
of strong Ly-alpha absorbers at z= 2.3, the J1230+34 field. Using a catalog of
Ly-alpha absorbers with logN_HI>20.0 cm^-2 based on the baryon oscillation
spectroscopic survey (BOSS), we found 6 fields where 3 or more absorbers are
concentrated within a (50 Mpc)^3 cubic box in the comoving scale. Among them,
we focus on the J1230+34 field, where 2 DLAs and 2 sub-DLAs present. Our
narrow-band imaging observations with Subaru/Suprime-Cam using a custom-made
filter, NB400 (lambda_c=4003 A and FWHM=92 A) yield a sample of 149 LAEs in
this field. In the large scale (~50 Mpc), we have found no differences between
the obtained Ly-alpha luminosity function and those in the blank fields at
similar redshifts. We also compare the frequency distribution of the Ly-alpha
rest-frame equivalent width (EW_0) in the target field and other fields
including both overdensity region and blank field, but find no differences. On
the other hand, in the small scale (~10 Mpc), we have found a possible
overdensity of LAEs around a DLA with the highest HI column density (N_HI=21.08
cm^-2) in the target field while there are no density excess around the other
absorbers with a lower N_HI.
