Discovery of an Enormous Ly$alpha$ nebula in a massive galaxy overdensity at $z=2.3$. (arXiv:1609.04021v2 [astro-ph.GA] UPDATED)

Discovery of an Enormous Ly$alpha$ nebula in a massive galaxy overdensity at $z=2.3$. (arXiv:1609.04021v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Cai_Z/0/1/0/all/0/1">Zheng Cai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fan_X/0/1/0/all/0/1">Xiaohui Fan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_Y/0/1/0/all/0/1">Yujin Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bian_F/0/1/0/all/0/1">Fuyan Bian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prochaska_J/0/1/0/all/0/1">J. Xavier Prochaska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zabludoff_A/0/1/0/all/0/1">Ann Zabludoff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McGreer_I/0/1/0/all/0/1">Ian McGreer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zheng_Z/0/1/0/all/0/1">Zhenya Zheng</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Green_R/0/1/0/all/0/1">Richard Green</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cantalupo_S/0/1/0/all/0/1">Sebastiano Cantalupo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Frye_B/0/1/0/all/0/1">Brenda Frye</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hamden_E/0/1/0/all/0/1">Erika Hamden</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jiang_L/0/1/0/all/0/1">Linhua Jiang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kashikawa_N/0/1/0/all/0/1">Nobunari Kashikawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_R/0/1/0/all/0/1">Ran Wang</a>

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
$L_{rm{nebula}}=5.1pm0.1times10^{44}$ erg s$^{-1}$. Above the 2$sigma$
surface brightness limit of SB$_{rm{Lyalpha}}= 4.8times10^{-18}$ 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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