http://arxiv.org/abs/1506.02885
Star-formation in galaxies generates a lot of Ly$\alpha$ photons. Understanding the escape of Ly$\alpha$ photons from galaxies is a key issue in studying high redshift galaxies and probing cosmic reionization with Ly$\alpha$. To understand Ly$\alpha$ escape, it is valuable to study analogs of high redshift Ly$\alpha$ emitters in nearby universe. However, most nearby analogs have too small a Ly$\alpha$ equivalent width and escape fraction compared to high redshift Ly$\alpha$ emitters. One different group of nearby analogs are “Green Pea” galaxies, selected by their high equivalent width optical emission lines. Here we show that Green Pea galaxies have strong Ly$\alpha$ emission lines and high Ly$\alpha$ escape fraction (see also Henry et al. 2015), providing an opportunity to solve Ly$\alpha$ escape problem. Green Peas have a Ly$\alpha$ equivalent width distribution similar to high redshift Ly$\alpha$ emitters. The Ly$\alpha$ escape fraction correlates with many quantities of Ly$\alpha$ profile, especially the ratio of Ly$\alpha$ blue peak velocity to H$\alpha$ line width. Comparing Ly$\alpha$ profiles with expanding-shell radiative transfer models suggest these correlations are probably caused by column density and kinematics of neutral gas. The Ly$\alpha$ escape fraction also correlates with galactic metallicity and dust extinction. Studying Ly$\alpha$ in Green Peas can reveal how these various factors combine to make Ly$\alpha$ escape.
H. Yang, S. Malhotra, M. Gronke, et. al.
Wed, 10 Jun 15
48/53
Comments: 7 figures, 1 table, submitted to ApJ, comments welcome
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