The Luminosity-Area Relation of z > 2 Quasars' Ly Nebulae

Cool (T similar to 10(4) K) gas is commonly observed around z > 2 quasars as traced by extended Ly alpha emission. These large-scale nebulae are usually studied using circularly averaged surface-brightness profiles, which suppress information on morphological differences. Here, we revisit the Ly alpha nebulae around 78 z similar to 2-3 quasars to obtain a novel estimate of their area and asymmetry using a common redshift-corrected surface-brightness threshold. We find a luminosity-area relation of the form log (L-Ly alpha(Neb)) = a(1) log (Area (Neb)) + a(0). Most nebulae are symmetric and bright, the most lopsided ones being the faintest and less extended. The enormous Lya nebulae, asymmetric due to the presence of active companions, are the exceptions to this trend. By using simulations able to reproduce z similar to 6 quasars' nebulae, we show that the observed relation should not vary with redshift. Finally, we discuss possible mechanisms that drive the relation and future work needed to constrain them.