2020A&A...643A.149S

We present the photometric determination of the bright end of the Lyα luminosity function (LF; at L_Lyα≥10^43.3erg/s) within four redshift windows (Δz<0.16) in the interval 2.2≤z≤3.3. Our work is based on the Javalambre Photometric Local Universe Survey (J-PLUS) first data release, which provides multiple narrow-band measurements over ∼1000deg², with limiting magnitude r∼22. The analysis of high-z Lyα-emitting sources over such a wide area is unprecedented and allows us to select approximately 14500 hyper-bright (L_Lyα>10^43.3erg/s) Lyα-emitting candidates. We test our selection with two spectroscopic programs at the GTC telescope, which confirm ∼89% of the targets as line-emitting sources, with ∼64% being genuine z∼2.2 quasars (QSOs). We extend the 2.2≤z≤3.3 Lyα LF for the first time above L_Lyα∼10⁴⁴erg/s and down to densities of ∼10^–8Mpc^–3. Our results unveil the Schechter exponential decay of the brightest-end of the Lyα LF in great detail, complementing the power-law component of previous determinations at 43.3≤Log₁₀(L_Lyα/(erg/s)≤44. We measure Φ^*=(3.33±0.19)x10^–6, Log(L^*)=44.65±0.65, and α=-1.35±0.84 as an average over the probed redshifts. These values are significantly different from the typical Schechter parameters measured for the Lyα LF of high-z star-forming Lyman-α emitters (LAEs). This implies that z>2 AGNs/QSOs (likely dominant in our samples) are described by a structurally different LF from that used to describe z>2 star-forming LAEs, namely L_QSOs^*∼100L_LAEs^* and Φ_QSOs^*∼10^–3Φ_LAEs^*, with the transition between the two LFs happening at L_Lyα∼10^43.5erg/s. This supports the scenario in which Lyα-emitting AGNs/QSOs are the most abundant class of z≥2 Lyα emitters at L_Lyα≥10^43.3erg/s. Finally, we suggest that a significant number of these z≥2 AGNs/QSOs (∼60% of our samples) are currently misclassified as stars based on their broad-band colours, but are identified for the first time as high-z line-emitters by our narrow-band-based selection.