ODIN: Clustering Properties of Ly$\alpha$ Blobs at $z$ $\sim$ 2.4 and 3.1

Abstract

Spatially extended Ly$\alpha$ nebulae, known as Ly$\alpha$ blobs (LABs), are a rare population at $z>2$ that are thought to trace proto-groups 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 ($\sim$9~\sqdeg) COSMOS field at $z\sim 2.4$ and 3.1, respectively, enabling estimation of their bias and host halo masses through clustering analysis. We measure the angular auto-correlation functions (ACFs) of LABs and derive galaxy bias factors of $b$ = $4.0\pm 0.8$ and $3.8\pm 0.7$, corresponding to minimum halo masses of $2.8_{-1.8}^{+3.0}$ and $0.7_{-0.5}^{+0.8}\times 10^{12}{M}_{\odot }$ and median halo masses of $4.2_{-2.5}^{+3.8}$ and $1.1_{-0.7}^{+1.1}\times 10^{12}{M}_{\odot }$ at $z\sim 2.4$ and 3.1, respectively. LABs occupy $\sim$11${}_{-8}^{+39}$\% and $\sim$3${}_{-2}^{+9}$\% of all dark matter halos above these minimum halo masses. These findings suggest that LABs inhabit massive dark matter halos, likely tracing proto-group environments that evolve into present-day massive halos ($\sim$10${}^{13}{M}_{\odot }$), where massive elliptical galaxies or galaxy groups reside, by $z=0$.

13 pages, 4 figures, Accepted for publication in ApJ