Green Peas are nearby analogs of high-redshift Lyα-emitting galaxies. To probe their Lyα escape, we study the spatial profiles of Lyα 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 Lyα emission from their 2D COS spectra, and of UV continuum from both the 2D spectra and NUV images. The Lyα emission shows more extended spatial profiles than the UV continuum in most Green Peas. The deconvolved Full Width Half Maximum (FWHM) of the Lyα spatial profile is about 2 to 4 times that of the UV continuum in most cases. Since Green Peas are analogs of high-z LAEs, it suggests that most high-z LAEs likely have larger Lyα sizes than UV sizes. We also compare the spatial profiles of Lyα photons at blueshifted and redshifted velocities in eight Green Peas with sufficient data quality, and find the blue wing of the Lyα line has a larger spatial extent than the red wing in four Green Peas with comparatively weak blue Lyα line wings. We show that Green Peas and MUSE z=3−6 LAEs have similar Lyα and UV continuum sizes, which probably suggests starbursts in both low-z and high-z LAEs drive similar gas outflows illuminated by Lyα light. Five Lyman continuum (LyC) leakers in this sample have similar Lyα to UV continuum size ratios (~1.4-4.3) to the other Green Peas, indicating their LyC emission escape through ionized holes in the interstellar medium.
@article{arxiv.1610.05767,
title = {Ly$\alpha$ and UV Sizes of Green Pea Galaxies},
author = {Huan Yang and Sangeeta Malhotra and James E. Rhoads and Claus Leitherer and Aida Wofford and Tianxing Jiang and Junxian Wang},
journal= {arXiv preprint arXiv:1610.05767},
year = {2017}
}