The Compact UV Size of Green Pea Galaxies As Local Analogs of High-redshift Ly$alpha$-Emitters. (arXiv:2104.08282v3 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Kim_K/0/1/0/all/0/1">Keunho J. Kim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malhotra_S/0/1/0/all/0/1">Sangeeta Malhotra</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rhoads_J/0/1/0/all/0/1">James E. Rhoads</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_H/0/1/0/all/0/1">Huan Yang</a>
We study the dependence of Ly$alpha$ escape from galaxies on UV continuum
size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the
best local analogs of high-redshift Ly$alpha$-emitters (LAEs). We use the
Cosmic Origins Spectrograph near-ultraviolet images from the textit{Hubble
Space Telescope} to measure the UV size and luminosity with $0.047”$ spatial
resolution. Like most galaxies the GPs show a log-normal size distribution.
They also show a positive correlation between size and UV-continuum luminosity.
The slope of the size-continuum luminosity relation for GPs is consistent with
those of continuum-selected star-forming galaxies at low and high redshifts. A
distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a
population spread (1$sigma$) of 0.19 kpc. The peak of the size distribution
and the intercept of the size-luminosity relation of GPs are noticeably smaller
than those of continuum-selected star-forming galaxies at similar redshifts.
There are statistically significant anti-correlations found between the
circularized half-light radius ($r_{rm cir,50}$), the Ly$alpha$ equivalent
width (EW(Ly$alpha$)), and the Ly$alpha$ escape faction
($f^{Lyalpha}_{esc}$), suggesting that small UV-continuum radii are crucial
for Ly$alpha$ emission. GPs and high-redshift LAEs have similar sizes, once
spatial resolution effects are properly considered. Our results show that a
compact/small size is crucial for escape of Ly$alpha$ photons, and that
Ly$alpha$-emitters show constant characteristic size independent of their
redshift.
We study the dependence of Ly$alpha$ escape from galaxies on UV continuum
size and luminosity using a sample of 40 Green Pea (GP) galaxies, which are the
best local analogs of high-redshift Ly$alpha$-emitters (LAEs). We use the
Cosmic Origins Spectrograph near-ultraviolet images from the textit{Hubble
Space Telescope} to measure the UV size and luminosity with $0.047”$ spatial
resolution. Like most galaxies the GPs show a log-normal size distribution.
They also show a positive correlation between size and UV-continuum luminosity.
The slope of the size-continuum luminosity relation for GPs is consistent with
those of continuum-selected star-forming galaxies at low and high redshifts. A
distinctive feature of GPs is a very compact typical radius of 0.33 kpc with a
population spread (1$sigma$) of 0.19 kpc. The peak of the size distribution
and the intercept of the size-luminosity relation of GPs are noticeably smaller
than those of continuum-selected star-forming galaxies at similar redshifts.
There are statistically significant anti-correlations found between the
circularized half-light radius ($r_{rm cir,50}$), the Ly$alpha$ equivalent
width (EW(Ly$alpha$)), and the Ly$alpha$ escape faction
($f^{Lyalpha}_{esc}$), suggesting that small UV-continuum radii are crucial
for Ly$alpha$ emission. GPs and high-redshift LAEs have similar sizes, once
spatial resolution effects are properly considered. Our results show that a
compact/small size is crucial for escape of Ly$alpha$ photons, and that
Ly$alpha$-emitters show constant characteristic size independent of their
redshift.
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