The Sloan Digital Sky Survey has discovered a z = 2.4917 radio-loud active galactic nucleus ( AGN ) with a luminous , variable , low-polarization UV continuum , H i two-photon emission , and a moderately broad Ly \alpha line ( FWHM \simeq 1430 km s ^ { -1 } ) but without obvious metal-line emission .
SDSS J113658.36+024220.1 does have associated metal-line absorption in three distinct , narrow systems spanning a velocity range of 2710 km s ^ { -1 } .
Despite certain spectral similarities , SDSS J1136+0242 is not a Lyman-break galaxy .
Instead , the Ly \alpha and two-photon emission can be attributed to an extended , low-metallicity narrow-line region .
The unpolarized continuum argues that we see SDSS J1136+0242 very close to the axis of any ionization cone present .
We can conceive of two plausible explanations for why we see a strong UV continuum but no broad-line emission in this ‘ face-on radio galaxy ’ model for SDSS J1136+0242 : the continuum could be relativistically beamed synchrotron emission which swamps the broad-line emission ; or , more likely , SDSS J1136+0242 could be similar to PG 1407+265 , a quasar in which for some unknown reason the high-ionization emission lines are very broad , very weak , and highly blueshifted .