http://arxiv.org/abs/1610.05767
Green Peas are nearby analogs of high-redshift Ly$\alpha$-emitting galaxies. To probe their Ly$\alpha$ escape, we study the spatial profiles of Ly$\alpha$ and UV continuum emission of 24 Green Pea galaxies using the Cosmic Origins Spectrograph (COS) on Hubble Space Telescope (HST). We extract the spatial profiles of Ly$\alpha$ emission from their 2D COS spectra, and of UV continuum from both the 2D spectra and NUV images. The Ly$\alpha$ emission shows more extended spatial profiles than the UV continuum in most Green Peas. The deconvolved Full Width Half Maximum (FWHM) of the Ly$\alpha$ spatial profile is about 2 to 4 times that of the UV continuum in most cases. The Ly$\alpha$ light shows significant offsets from the UV continuum in four galaxies and central absorption in one galaxy. We also compare the spatial profiles of Ly$\alpha$ photons at blueshifted and redshifted velocities in eight Green Peas with sufficient data quality, and find the blue wing of the Ly$\alpha$ line has a larger spatial extent than the red wing in four Green Peas with comparatively weak blue Ly$\alpha$ line wings. These results together indicate that most Ly$\alpha$ photons escape out of Ly$\alpha$-emitting galaxies through many resonant scatterings in the HI gas. Five Lyman continuum (LyC) leakers in this sample have similar Ly$\alpha$ to UV continuum size ratios ($\sim1.4-4.3$) to the other Green Peas, indicating their LyC emission escape through ionized holes in the interstellar medium.
H. Yang, S. Malhotra, J. Rhoads, et. al.
Thu, 20 Oct 16
18/44
Comments: 7 pages, 5 figures. Submitted to ApJ
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