We report the properties of the 35 robust candidates of Ly \alpha blobs ( LABs ) , which are larger than 16 arcsec ^ { 2 } in isophotal area and brighter than 0.7 \times 10 ^ { -16 } ergs s ^ { -1 } cm ^ { -2 } , searched in and around the proto-cluster region at redshift z = 3.1 discovered by Steidel et al .
in the SSA22 field , based on wide-field ( 31 ^ { \prime } \times 23 ^ { \prime } ) and deep narrow-band ( NB 497 ; 4977/77 ) and broad-band ( B , V , and R ) images taken with the prime-focus camera on the Subaru telescope .
The two previously known giant LABs are the most luminous and the largest ones in our survey volume of 1.3 \times 10 ^ { 5 } Mpc ^ { 3 } .
We revealed the internal structures of the two giant LABs and discovered some bubble-like features , which suggest that intensive starburst and galactic superwind phenomena occurred in these objects in the past .
The rest 33 LABs have isophotal area of \sim 16–78 arcsec ^ { 2 } and flux of 0.7–7 \times 10 ^ { -16 } ergs s ^ { -1 } cm ^ { -2 } .
These 35 LABs show a continuous distribution of isophotal area and emission line flux .
The distributions of average surface brightness and morphology are widespread from relatively compact high surface brightness objects to very diffuse low surface brightness ones .
The physical origins of these LABs may be ( i ) photo-ionization by massive stars , or active galactic nuclei , or ( ii ) cooling radiation from gravitationally heated gas , or ( iii ) shock heating by starburst driven galactic superwind .
One third of them are apparently not associated with ultra-violet continuum sources that are bright enough to produce Ly \alpha emission , assuming a Salpeter initial mass function .
The 90 \% of these LABs are located inside the high surface density region of the 283 relatively compact and strong Ly \alpha emitters selected in our previous study .
This suggests that these LABs may be the phenomena related to dense environment at high redshift .