The Nature of Lyα Blobs: Supernova-dominated Primordial Galaxies

Abstract

We consider a forming galaxy undergoing multitudinous supernova (SN) explosions as a possible model of Lyα blobs (LABs). For this purpose, an ultra-high-resolution hydrodynamic simulation is performed using 1024 3 grid points, where SN remnants are resolved with sufficient accuracy. It is found that multiple SN explosions produce kiloparsec-size expanding hot bubbles, which drive cool, dense shells by strong shock. The colliding high-density cooling shells radiate intensive Lyα emission, resulting in a high Lyα luminosity of ∼1043 ergs s -1, comparable to the observed level in LABs. Also, recently discovered bubbly features in some LABs are quite similar to the structure predicted in the present simulation. Furthermore, the result demonstrates that LABs are representative of evolving primordial galaxies; they could hold direct information on the early chemical enrichment of galaxies, contrary to present-day galaxies that have undergone intense recycling of interstellar matter, thus erasing most of the early chemical history. It turns out that the metal mixing proceeds in a very inhomogeneous fashion, so that there appears a large spread of metallicity, that is, [Fe/H] ≈ 0 to -5 or [O/H] ≈ 1 to - 4. Hence, the early galactic chemical evolution may have proceeded in a different manner from that hitherto considered in one-zone models.