The Importance Of Star Formation Intensity In LY{alpha} Escape From Green Pea Galaxies And Lyman Break Galaxy Analogs. (arXiv:2002.08961v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kim_K/0/1/0/all/0/1">Keunho 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:+Butler_N/0/1/0/all/0/1">Nathaniel R. Butler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_H/0/1/0/all/0/1">Huan Yang</a>

We have studied ultraviolet images of 40 Green Pea galaxies and 15 local
Lyman Break Galaxy Analogs to understand the relation between Ly$alpha$ photon
escape and central UV photometric properties. We measured star formation
intensity (SFI, star formation rate per unit area) from the central 250 pc
region ($S_{rm 250pc}$) using COS/NUV images from the textit{Hubble Space
Telescope}. The measured $S_{rm 250pc}$ of our sample Green Peas ranges from
2.3–46 $M_{odot} rm{year}^{-1} rm{kpc^{-2}}$, with a geometric mean of
$15 M_{odot} rm{year}^{-1} rm{kpc^{-2}}$ and a standard deviation of
0.266 dex, forming a relatively narrow distribution. The Lyman Break Galaxy
Analogs show a similarly narrow distribution of $S_{rm 250pc}$ (0.271 dex),
though with a larger mean of 28 $M_{odot} rm{year}^{-1} rm{kpc^{-2}}$.
We show that while the Ly$alpha$ equivalent width (EW(Ly$alpha$)) and the
Ly$alpha$ escape fraction ($f^{Lyalpha}_{esc}$) are not significantly
correlated with the central SFI ($S_{rm 250pc}$), both are positively
correlated with the ratio of surface brightness to galaxy stellar mass ($S_{rm
250pc}/M_{rm star}$), with correlation coefficients ($p$-values) of 0.702
($1times 10^{-8}$) and 0.529 ($5times 10^{-4}$) with EW(Ly$alpha$) and
$f^{Lyalpha}_{esc}$, respectively. These correlations suggest a scenario where
intense central star formation can drive a galactic wind in galaxies with
relatively shallow gravitational potential wells, thus clearing channels for
the escape of Ly$alpha$ photons.

We have studied ultraviolet images of 40 Green Pea galaxies and 15 local
Lyman Break Galaxy Analogs to understand the relation between Ly$alpha$ photon
escape and central UV photometric properties. We measured star formation
intensity (SFI, star formation rate per unit area) from the central 250 pc
region ($S_{rm 250pc}$) using COS/NUV images from the textit{Hubble Space
Telescope}. The measured $S_{rm 250pc}$ of our sample Green Peas ranges from
2.3–46 $M_{odot} rm{year}^{-1} rm{kpc^{-2}}$, with a geometric mean of
$15 M_{odot} rm{year}^{-1} rm{kpc^{-2}}$ and a standard deviation of
0.266 dex, forming a relatively narrow distribution. The Lyman Break Galaxy
Analogs show a similarly narrow distribution of $S_{rm 250pc}$ (0.271 dex),
though with a larger mean of 28 $M_{odot} rm{year}^{-1} rm{kpc^{-2}}$.
We show that while the Ly$alpha$ equivalent width (EW(Ly$alpha$)) and the
Ly$alpha$ escape fraction ($f^{Lyalpha}_{esc}$) are not significantly
correlated with the central SFI ($S_{rm 250pc}$), both are positively
correlated with the ratio of surface brightness to galaxy stellar mass ($S_{rm
250pc}/M_{rm star}$), with correlation coefficients ($p$-values) of 0.702
($1times 10^{-8}$) and 0.529 ($5times 10^{-4}$) with EW(Ly$alpha$) and
$f^{Lyalpha}_{esc}$, respectively. These correlations suggest a scenario where
intense central star formation can drive a galactic wind in galaxies with
relatively shallow gravitational potential wells, thus clearing channels for
the escape of Ly$alpha$ photons.

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