Lyα blobs like company: the discovery of a candidate 100 kpc Lyα blob near to a radio galaxy with a giant Lyα halo B3 J2330+3927 at z=3.1

We present the discovery of a candidate of giant radio-quiet Ly alpha blob (RQLAB) in a large-scale structure around a high-redshift radio galaxy (HzRG) lying in a giant Ly alpha halo B3 J2330+3927 at redshift z = 3.087. We obtained narrow- and broad-band imaging around B3 J2330+3927 with Subaru/Suprime-Cam to search for Ly alpha emitters (LAEs) and absorbers (LAAs) at redshift z = 3.09 +/- 0.03. We detected candidate 127 LAEs and 26 LAAs in the field of view of 31 x 24 arcmin(2) (58 x 44 comoving Mpc). We found that B3 J2330+3927 is surrounded by a 130 kpc Ly alpha halo and a large-scale (similar to 60 x 20 comoving Mpc) filamentary structure. The large-scale structure contains one prominent local density peak with an overdensity of greater than 5, which is 8 arcmin (15 comoving Mpc) away from B3 J2330+3927. In this peak, we discovered a candidate 100 kpc RQLAB. The existence of both types of Ly alpha nebulae in the same large-scale structure suggests that giant Ly alpha nebulae need special large-scale environments to form. On smaller scales, however, the location of B3 J2330+3927 is not a significant local density peak in this structure, in contrast to the RQLAB. There are two possible interpretations of the difference of the local environments of these two Ly alpha nebulae. First, RQLAB may need a prominent (delta similar to 5) density peak of galaxies to form through intense starbursts due to frequent galaxy interactions/mergers and/or continuous gas accretion in an overdense environment. On the other hand, Ly alpha halo around HzRG may not always need a prominent density peak to form if the surrounding Ly alpha halo is mainly powered by its radio and active galactic nucleus activities. Alternatively, both RQLAB and Ly alpha halo around HzRG may need prominent density peaks to form but we could not completely trace the density of galaxies because we missed evolved and dusty galaxies in this survey.