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arXiv · 1609.04021

Discovery of an Enormous Ly$\alpha$ nebula in a massive galaxy overdensity at $z=2.3$

Zheng Cai·Xiaohui Fan·Yujin Yang·Fuyan Bian·J. Xavier Prochaska·Ann Zabludoff·Ian McGreer·Zhenya Zheng·Richard Green·Sebastiano Cantalupo·Brenda Frye·Erika Hamden·Linhua Jiang·Nobunari Kashikawa·Ran Wang
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Abstract

Enormous Ly$\alpha$ Nebulae (ELANe), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. Previous successful searches for ELANe have focused on wide-field narrowband surveys, or have targeted known sources such as ultraluminous quasi-stellar-objects (QSOs) or radio galaxies. Utilizing groups of coherently strong Ly$\alpha$ absorptions (CoSLAs), we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, BOSS1441, at $z=2-3$ (Cai et al. 2016a). In its density peak, we discover an ELAN that is associated with a relatively faint continuum. To date, this object has the highest diffuse Ly$\alpha$ nebular luminosity of $L_{\rm{nebula}}=5.1\pm0.1\times10^{44}$ erg s$^{-1}$. Above the 2$\sigma$ surface brightness limit of SB$_{\rm{Ly\alpha}}= 4.8\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$, this nebula has an end-to-end spatial extent of 442 kpc. This radio-quiet source also has extended \civ\ $\lambda1549$ and \heii\ $\lambda1640$ emission on $\gtrsim30$ kpc scales. Note that the Ly$\alpha$, \heii\ and \civ\ emission all have double-peaked line profiles. Each velocity component has a full-width-half-maximum (FWHM) of $\approx700 - 1000$ km s$^{-1}$. We argue that this Ly$\alpha$ nebula could be powered by shocks due to an AGN-driven outflow or/and photoionization by a strongly obscured source.

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Zheng Cai, Xiaohui Fan, Yujin Yang, Fuyan Bian, J. Xavier Prochaska, Ann Zabludoff, Ian McGreer, Zhenya Zheng, Richard Green, Sebastiano Cantalupo, Brenda Frye, Erika Hamden, Linhua Jiang, Nobunari Kashikawa, Ran Wang. 2016-09-13. Discovery of an Enormous Ly$\alpha$ nebula in a massive galaxy overdensity at $z=2.3$. https://doi.org/10.3847/1538-4357/aa5d14

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