A Subaru Search for Lyα Blobs in and around the Protocluster Region At Redshift z = 3.1^*

We report the properties of 35 robust candidate Lyα blobs (LABs), which are larger than 16 arcsec² in isophotal area and brighter than 0.7 × 10^-16 ergs s^-1 cm^-2, located in and around the protocluster region at redshift z = 3.1 discovered by Steidel et al. in the SSA22 field, based on wide-field (31' × 23') and deep narrowband (NB497; 4977 Å, FWHM 77 Å) and broadband (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 in our survey volume of 1.3 × 10⁵ Mpc³. We reveal the internal structures of the two giant LABs and discover some bubble-like features, which suggest that intensive starburst and galactic superwind phenomena occurred in these objects in the past. The other 33 LABs have isophotal areas of ∼16–78 arcsec² and flux of (0.7–7) × 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 (1) photoionization by massive stars or active galactic nuclei, or (2) cooling radiation from gravitationally heated gas, or (3) shock heating by starburst-driven galactic superwind. One-third of the LABs are apparently not associated with ultraviolet continuum sources that are bright enough to produce Lyα emission, assuming a Salpeter initial mass function. Of these LABs 90% are located inside the high surface density region of the 283 relatively compact and strong Lyα emitters selected in our previous study. This suggests that these LABs may be phenomena related to a dense environment at high redshift.