%0 Generic %1 hashimoto2016lyalpha %A Hashimoto, Takuya %A Ouchi, Masami %A Shimasaku, Kazuhiro %A Schaerer, Daniel %A Nakajima, Kimihiko %A Shibuya, Takatoshi %A Ono, Yoshiaki %A Rauch, Michael %A Goto, Ryosuke %D 2016 %K EW Lya emitters physical properties %T Ly$\alpha$ Emitters with Very Large Ly$\alpha$ Equivalent Widths, EW$_0$(Ly$\alpha$) $200-400$ \AA, at $z2$ %U http://arxiv.org/abs/1611.00777 %X We present physical properties of spectroscopically confirmed Ly$\alpha$ emitters (LAEs) with very large rest-frame Ly$\alpha$ equivalent widths EW$_0$(Ly$\alpha$). Although the definition of large EW$_\rm 0$(Ly$\alpha$) LAEs is usually difficult due to limited statistical and systematic uncertainties, we identify six LAEs selected from $3000$ LAEs at $z2$ with reliable measurements of EW$_0$ (Ly$\alpha$) $\simeq 200-400$ \AA\ given by careful continuum determinations with our deep photometric and spectroscopic data. These large EW$_0$(Ly$\alpha$) LAEs do not have signatures of AGN, but notably small stellar masses of $M_* = 10^7-8$ $M_ødot$ and high specific star-formation rates (star formation rate per unit galaxy stellar mass) of $100$ Gyr$^-1$. These LAEs are characterized by the median values of $L(Ly\alpha)=3.7\times 10^42$ erg s$^-1$ and $M_UV=-18.0$ as well as the blue UV continuum slope of $= -2.5\pm0.2$ and the low dust extinction $E(B-V)_* = 0.02^+0.04_-0.02$, which indicate a high median Ly$\alpha$ escape fraction of $f_esc^Ly\alpha=0.68\pm0.30$. This large $f_esc^\rm Ly\alpha$ value is explained by the low Hi column density in the ISM that is consistent with FWHM of the Ly$\alpha$ line, $FWHM (Ly\alpha)=212\pm32$ km s$^-1$, significantly narrower than those of small EW$_0$(Ly$\alpha$) LAEs. Based on the stellar evolution models, our observational constraints of the large EW$_0$ (Ly$\alpha$), the small $\beta$, and the rest-frame Heii equivalent width imply that at least a half of our large EW$_0$(Ly$\alpha$) LAEs would have young stellar ages of $20$ Myr and very low metallicities of $Z<0.02 Z_ødot$ regardless of the star-formation history.

@misc{hashimoto2016lyalpha, abstract = {We present physical properties of spectroscopically confirmed Ly$\alpha$ emitters (LAEs) with very large rest-frame Ly$\alpha$ equivalent widths EW$_{\rm 0}$(Ly$\alpha$). Although the definition of large EW$_{\rm 0}$(Ly$\alpha$) LAEs is usually difficult due to limited statistical and systematic uncertainties, we identify six LAEs selected from $\sim 3000$ LAEs at $z\sim 2$ with reliable measurements of EW$_{\rm 0}$ (Ly$\alpha$) $\simeq 200-400$ \AA\ given by careful continuum determinations with our deep photometric and spectroscopic data. These large EW$_{\rm 0}$(Ly$\alpha$) LAEs do not have signatures of AGN, but notably small stellar masses of $M_{\rm *} = 10^{7-8}$ $M_{\rm \odot}$ and high specific star-formation rates (star formation rate per unit galaxy stellar mass) of $\sim 100$ Gyr$^{-1}$. These LAEs are characterized by the median values of $L({\rm Ly\alpha})=3.7\times 10^{42}$ erg s$^{-1}$ and $M_{\rm UV}=-18.0$ as well as the blue UV continuum slope of $\beta = -2.5\pm0.2$ and the low dust extinction $E(B-V)_{\rm *} = 0.02^{+0.04}_{-0.02}$, which indicate a high median Ly$\alpha$ escape fraction of $f_{\rm esc}^{\rm Ly\alpha}=0.68\pm0.30$. This large $f_{\rm esc}^{\rm Ly\alpha}$ value is explained by the low {\sc Hi} column density in the ISM that is consistent with FWHM of the Ly$\alpha$ line, ${\rm FWHM (Ly\alpha)}=212\pm32$ km s$^{-1}$, significantly narrower than those of small EW$_{\rm 0}$(Ly$\alpha$) LAEs. Based on the stellar evolution models, our observational constraints of the large EW$_{\rm 0}$ (Ly$\alpha$), the small $\beta$, and the rest-frame He{\sc ii} equivalent width imply that at least a half of our large EW$_{\rm 0}$(Ly$\alpha$) LAEs would have young stellar ages of $\lesssim 20$ Myr and very low metallicities of $Z<0.02 Z_\odot$ regardless of the star-formation history.}, added-at = {2016-11-04T09:39:36.000+0100}, author = {Hashimoto, Takuya and Ouchi, Masami and Shimasaku, Kazuhiro and Schaerer, Daniel and Nakajima, Kimihiko and Shibuya, Takatoshi and Ono, Yoshiaki and Rauch, Michael and Goto, Ryosuke}, biburl = {https://www.bibsonomy.org/bibtex/2f49df4db3cf867cd3008ed6a9aa8e707/miki}, description = {[1611.00777] Ly$\alpha$ Emitters with Very Large Ly$\alpha$ Equivalent Widths, EW$_{\rm 0}$(Ly$\alpha$) $\simeq 200-400$ \AA, at $z\sim 2$}, interhash = {8387c0ab870b427d14d182e9cdf40816}, intrahash = {f49df4db3cf867cd3008ed6a9aa8e707}, keywords = {EW Lya emitters physical properties}, note = {cite arxiv:1611.00777Comment: Accepted for publication in MNRAS; 23 pages with 16 figures}, timestamp = {2016-11-04T09:39:58.000+0100}, title = {Ly$\alpha$ Emitters with Very Large Ly$\alpha$ Equivalent Widths, EW$_{\rm 0}$(Ly$\alpha$) $\simeq 200-400$ \AA, at $z\sim 2$}, url = {http://arxiv.org/abs/1611.00777}, year = 2016 }