J-PLUS: Unveiling the brightest end of the Lyα luminosity function at 2.0 < z < 3.3 over 1000 deg^2⋆

¹ Centro de Estudios de Física del Cosmos de Aragón, Plaza San Juan 1, planta 2, 44001 Teruel, Spain
e-mail: dspinoso@cefca.es
² PlantTech Research Institute Limited, South British House, 4th Floor, 35 Grey Street, Tauranga 3110, New Zealand
³ Donostia International Physics Center, Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián (Gipuzkoa), Spain
⁴ IKERBASQUE, Basque Foundation for Science, 48013 Bilbao, Spain
⁵ Department of Physics, Lancaster University, Lancaster LA1 4YB, UK
⁶ Institute for Multi-messenger Astrophysics and Cosmology, Department of Physics, Missouri University of Science and Technology, 1315 N. Pine St., Rolla, MO 65409, USA
⁷ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, 05508090 São Paulo, SP, Brazil
⁸ Asociación Astrofísica para la Promoción de la Investigación, Instrumentación y su Desarrollo, 38205 La Laguna, Tenerife, Spain
⁹ Observatório Nacional/MCTIC, Rua José Cristino, 77, CEP 20921-400 São Cristóvão, Rio de Janeiro (RJ), Brazil
¹⁰ Institut de Ciències del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
¹¹ Institució Catalana de Recerca i Estudis Avançats, 08034 Barcelona, Spain
¹² Institute for Advanced Study, Princeton, NJ 08544, USA
¹³ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109-1107, USA
¹⁴ Instituto de Astrofísica de Andalucía – CSIC, Apdo 3004, 18080 Granada, Spain
¹⁵ Departamento de Física, Universidade Federal do Rio Grande do Norte, 59078-970 Natal, RN, Brazil
¹⁶ Instituto Nacional de Pesquisas Espaciais. INPE/CRN, 59076-740 Natal, RN, Brazil

Received: 25 June 2020
Accepted: 8 September 2020

Abstract

We present the photometric determination of the bright end of the Lyα luminosity function (LF; at L_Lyα  ≳  10^43.3 erg s⁻¹) within four redshift windows (Δ z <  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 ∼1000 deg², 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 14 500 hyper-bright (L_Lyα >  10^43.3 erg s⁻¹) 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  ∼  10⁴⁴ erg s⁻¹ and down to densities of ∼10⁻⁸ Mpc⁻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⁻¹) ≲ 44. We measure Φ^* = (3.33 ± 0.19)×10⁻⁶, 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^* ~ 10⁻³ Φ_LAEs^*, with the transition between the two LFs happening at L_Lyα  ∼  10^43.5 erg s⁻¹. This supports the scenario in which Lyα-emitting AGNs/QSOs are the most abundant class of z​ ≳ ​2 Lyα emitters at L_Lyα  ≳  10^43.3 erg s⁻¹. 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.