A successful broadband survey for giant Lyα nebulae. II. Spectroscopic confirmation

Using a systematic broadband search technique, we have carried out a survey for large Lyα nebulae (or Lyα "blobs") at 2 ≲ z ≲ 3 within 8.5 deg² of the NOAO Deep Wide-Field Survey Boötes field, corresponding to a total survey comoving volume of ≈10⁸ h ^-3 ₇₀ Mpc³. Here, we present our spectroscopic observations of candidate giant Lyα nebulae. Of 26 candidates targeted, 5 were confirmed to have Lyα emission at 1.7 ≲ z ≲ 2.7, 4 of which were new discoveries. The confirmed Lyα nebulae span a range of Lyα equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Lyα nebulae lying within the redshift desert (i.e., 1.2 ≲ z ≲ 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Lyα nebula population across enormous comoving volumes.