We report the discovery of 14 Lyman- \alpha blobs ( LABs ) at z \sim 0.3 , existing at least 4 - 7 billion years later in the Universe than all other LABs known .
Their optical diameters are 20 - 70 kpc , and GALEX data imply Ly \alpha luminosities of ( 0.4 - 6.3 ) \times 10 ^ { 43 } erg s ^ { -1 } .
Contrary to high-z LABs , they live in low-density areas .
They are ionized by AGN , suggesting that cold accretion streams as a power source must deplete between z = 2 and z = 0.3 .
We also show that transient AGN naturally explain the ionization deficits observed in many LABs : Their Ly \alpha and X-ray fluxes decorrelate below \lesssim 10 ^ { 6 } years because of the delayed escape of resonantly scattering Ly \alpha photons .
High Ly \alpha luminosities do not require currently powerful AGN , independent of obscuration . Chandra X-ray data reveal intrinsically weak AGN , confirming the luminous optical nebulae as impressive ionization echoes .
For the first time , we also report mid-infrared thermal echoes from the dusty tori .
We conclude that the AGN have faded by 3 - 4 orders of magnitude within the last 10 ^ { 4 - 5 } years , leaving fossil UV , optical and thermal radiation behind .
The host galaxies belong to the group of previously discovered Green Bean galaxies ( GBs ) . Gemini optical imaging reveals smooth spheres , mergers , spectacular outflows and ionization cones .
Because of their proximity and high flux densities , GBs are perfect targets to study AGN feedback , mode switching and the Ly \alpha escape .
The fully calibrated , coadded optical FITS images are publicly available .