JWST UNCOVER: the overabundance of ultraviolet-luminous galaxies at z > 9
Nanayakkara, Themiya; van Dokkum, Pieter; Fujimoto, Seiji; Bezanson, Rachel; Price, Sedona H.; Brammer, Gabriel; Greene, Jenny E.; Williams, Christina C.; Leja, Joel; Whitaker, Katherine E.; Goulding, Andy D.; Zitrin, Adi; Atek, Hakim; Wang, Bingjie; Weaver, John R.; Kokorev, Vasily; Labbe, Ivo; Chemerynska, Iryna; Dayal, Pratika; Furtak, Lukas J.; Cutler, Sam E.; Pan, Richard; Weibel, Andrea
France, Israel, United States, Netherlands, Switzerland, Australia, Denmark
Abstract
Over the past year, JWST has uncovered galaxies at record-breaking distances up to z ~ 13. The JWST UNCOVER (ultra-deep NIRSpec and NIRcam observations before the epoch of reionization) program has obtained ultra-deep multiwavelength NIRCam imaging of the massive galaxy cluster A2744 over ~45 arcmin2 down to ~29.5 AB mag. Here, we present a robust ultraviolet (UV) luminosity function derived through lensing clusters at 9 < z < 12. Using comprehensive end-to-end simulations, we account for all lensing effects and systematic uncertainties in deriving both the amplification factors and the effective survey volume. Our results confirm the intriguing excess of UV-bright galaxies (MUV <-20 AB mag) previously reported at z > 9 in recent JWST studies. In particular, a double power-law (DPL) describes better the bright end of the luminosity function compared to the classical Schechter form. The number density of these bright galaxies is 10-100 times larger than theoretical predictions and previous findings based on Hubble Space Telescope (HST) observations. Additionally, we measure a star formation rate density of ρSFR = 10-2.64 M⊙ yr-1 Mpc-3 at these redshifts, which is 4-10 times higher than galaxy formation models that assume a constant star formation efficiency. Future wide-area surveys and accurate modelling of lensing-assisted observations will reliably constrain both the bright and the dim end of the UV luminosity function at z > 9, which will provide key benchmarks for galaxy formation models.