Star-forming galactic contrails as a source of metal enrichment and ionizing radiation at high redshift★

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A spectroscopically detected Lyman alpha emitting halo at redshift 3.216 in the GOODS-N field is found to reside at the convergence of several Lyman alpha filaments. HST images show that some of the filaments are inhabited by galaxies. Several of the galaxies in the field have pronounced head-tail structures, which are partly aligned with each other. The blue colors of most tails suggest the presence of young stars, with the emission from at least one of the galaxies apparently dominated by high equivalent width Lyman alpha. Faint, more diffuse, and similarly elongated, apparently stellar features, can be seen over an area with a linear extent of at least 90 kpc. The region within several arcseconds of the brightest galaxy exhibits spatially extended emission by HeII, NV and various lower ionization metal lines. The gas-dynamical features present are strongly reminiscent of ram-pressure stripped galaxies, including evidence for recent star formation in the stripped contrails. Spatial gradients in the appearance of several galaxies may represent a stream of galaxies passing from a colder to a hotter intergalactic medium. The stripping of gas from the in-falling galaxies, in conjunction with the occurrence of star formation and stellar feedback in the galactic contrails suggests a mechanism for the metal enrichment of the high redshift intergalactic medium that does not depend on long-range galactic winds, at the same time opening a path for the escape of ionizing radiation from galaxies.