Signature of Galactic Outflows as Absorption-Free Gaps in the Ly-alpha   Forest
  Powerful outflows from star-forming galaxies are expected to push away the neutral intergalactic medium (IGM) around those galaxies, and produce absorption-free gaps in the Ly-alpha forest. We analyze the abundance of gaps of various sizes in three high resolution spectra of quasars at z ~ 3 - 3.5. The gap statistics agrees well with a model in which galactic halos above a minimum mass scale of M_min ~ 10^10 M_sun produce bubbles with a characteristic radius of R_b ~ 0.48 Mpc/h. Both numbers are consistent with naive theoretical expectations, where the minimum galaxy mass reflects the threshold for infall of gas out of a photo-ionized IGM. The observed gaps are typically bounded by deep absorption features as expected from the accumulation of swept-up gas on the bubble walls. 
Taotao Fang (1), Abraham Loeb (2), David Tytler (3), David Kirkman   (3), Nao Suzuki (3) ((1) UC Berkeley, (2) Harvard Unive...