ODIN: Clustering Properties of Ly α Blobs at z ∼ 2.4 and 3.1

Abstract Spatially extended Ly α nebulae, known as Ly α blobs (LABs), are a rare population at z > 2 that are thought to trace protogroups or the progenitors of massive galaxies in the present-day Universe. However, their dark matter halo properties (e.g., halo mass) are still uncertain, due to their rarity and strong field-to-field variation. The One-hundred-deg 2 DECam Imaging in Narrowbands (ODIN) survey has discovered 103 and 112 LABs in the extended (∼9 deg 2 ) COSMOS field at z ∼ 2.4 and 3.1, respectively, enabling the estimation of their bias and host halo masses through clustering analysis. We measure the angular autocorrelation functions (ACFs) of the LABs and derive galaxy bias factors of b = 4.0 ± 0.8 and 3.8 ± 0.7, corresponding to minimum halo masses of 2 . 8 − 1.8 + 3.0 and 0 . 7 − 0.5 + 0.8 × 1 0 12 M ⊙ and median halo masses of 4 . 2 − 2.5 + 3.8 and 1 . 1 − 0.7 + 1.1 × 1 0 12 M ⊙ at z ∼ 2.4 and 3.1, respectively. LABs occupy ∼11 − 8 + 39 % and ∼3 − 2 + 9 % of all dark matter halos above these minimum halo masses. These findings suggest that LABs inhabit massive dark matter halos, likely tracing protogroup environments that evolve into present-day massive halos (∼10 13 M ⊙ ), where massive elliptical galaxies or galaxy groups reside, by z = 0.