C3PO: A Ly alpha Emitting Galaxy at z about 9

We present deep, >10 hr, JWST NIRSpec G140M and G395M observations of a previously known galaxy C3PO-8447 at z=8.99781. Our new NIRSpec data from the Carbon-3 plus Oxygen (C3PO) survey detect Ly α emission with an escape fraction of 1.5 plus or minus0.3% and a velocity offset of 210 plus or minus80 km s-1, making C3PO-8447 the third Ly α emitting galaxy confirmed at z 9. The galaxy has a low stellar mass of 2.2 plus or minus0.1 times 10 7 M, a young stellar age of 1.6 plus or minus0.2 Myr, and a low oxygen abundance of 12+ (O/H) = 7.50 plus or minus0.08. UV diagnostic diagrams incorporating the C IV, O III], and C III] emission lines indicate that the ionization of C3PO-8447 is dominated by the recent starburst. The low Ly α escape fraction of C3PO-8447 implies that C3PO-8447 resides in a small ionized bubble with radius R about 0.07 to 0.20 pMpc, which can be produced by C3PO-8447 alone. We find no evidence for either a large-scale galaxy overdensity around C3PO-8447 or a significant contribution from nearby galaxies to its ionizing photon budget. Taken together, these results suggest that C3PO-8447 likely represents an ionized bubble powered by a single low-mass, vigorously star-forming galaxy during the early stages of cosmic reionization.