J-PLUS: Synthetic galaxy catalogues with emission lines for photometric surveys

Abstract

We present a synthetic galaxy lightcone specially designed for narrow-band optical photometric surveys. To reduce time-discreteness effects, unlike previous works, we directly include the lightcone construction in the L-Galaxies semi-analytic model applied to the subhalo merger trees of the Millennium simulation. Additionally, we add a model for the nebular emission in star-forming regions, which is crucial for correctly predicting the narrow/medium-band photometry of galaxies. Explicitly, we consider, individually for each galaxy, the contribution of 9 different lines: 6583Å), and [S ii] (6717Å, 6731Å). We validate our lightcone by comparing galaxy number counts, angular clustering, and Hα , Hβ , [O ii] and [O iii] 5007 luminosity functions to a compilation of observations. As an application of our mock lightcones, we generate catalogues tailored for J-PLUS, a large optical galaxy survey featuring 5 broad and 7 medium band filters. We study the ability of the survey to correctly identify, with a simple three filter method, a population of emission-line galaxies at various redshifts. We show that the 4000Å break in the spectral energy distribution of galaxies can be misidentified as line emission. However, all significant excess (larger than 0.4 magnitudes) can be correctly and unambiguously attributed to emission line galaxies. Our catalogues are publicly released to facilitate their use in interpreting narrow-band surveys and for quantifying the impact of line emission in broad band photometry.

J-PLUS: The star formation main sequence and rate density at d ≲ 75 Mpc

“…or [O ii] at z ∼ 0.77; see Izquierdo-Villalba et al 2019); and finally, it covers a well defined, non pre-selected area to compute volume densities. The initial selection yielded 109 815 sources.…”

J-PLUS: Unveiling the brightest end of the Lyαluminosity function at 2.0 <z< 3.3 over 1000 deg2

“…Grey-blue dots mark all the J-PLUS detections in the pointing, while red and purple crosses show z ∼ 2.4 QSOs and low-z galaxies from SDSS DR14. Yellow triangles show J-PLUS mock data of z ∼ 2.4 SF LAEs(Izquierdo-Villalba et al 2019). Finally, our Lyα-emitting candidates are shown as green dots.…”

Modelling emission lines in star forming galaxies

“…Orsi et al ( 2014) introduced the GET_EMLINES 12 model of emission lines and implemented this into the SAG semi-analytical galaxy formation model of Gargiulo et al (2015). This model has since been used with other semi-analytic models (SAG, SAGE, Galacticus) by Favole et al (2020) to make predictions for OII emitters and by Izquierdo-Villalba et al (2019) with L-GALAXIES to make mock catalogues.…”

“…This model reproduces the local BPT diagram, but does not evolve with redshift (see Appendix B). This model has also been used to look at the clustering of emission line galaxies in different semi-analytical models (Izquierdo-Villalba et al 2019;Favole et al 2020); a similar approach has also been applied in gas dynamic simulations (Shen et al 2020). Hirschmann et al (2017) used the HII region models of Gutkin et al (2016) to post-process 20 galaxies drawn from a series of cosmological zoom hydrodynamical simulations (see also Hirschmann et al 2019).…”