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Arxiv: The ALPINE-ALMA [CII] Survey: Modelling ALMA and JWST lines to constrain the interstellar medium of z\sim 5 galaxies Published: 11/12/2024 9:06:36 PM Updated: 11/12/2024 9:06:36 PM

Paper abstract: In this work, we devise a model for estimating UV and optical line emission(i.e., CIII] 1909A, H\beta, [OIII] 5007A, H\alpha, [NII] 6583A)tracing HII regions in the interstellar medium (ISM) of galaxies at z~4-6from the ALMA Large Programme ALPINE. The aim is to investigate the impact ofbinary stars in the stellar population along with an abrupt quenching in theStar Formation History (SFH) on line emission. This is crucial forunderstanding the ISM's properties in early galaxies and identifying new starformation tracers in high-z galaxies. The model simulatesHII+Photodissociation Region (PDR) complexes through radiative transfer in 1Dslabs, characterized by gas density (n), ionisation parameter (U), andmetallicity (Z). It considers: (a) heating from star formation (SF),simulated with Starburst99 and BPASS to quantify binary stars impact; (b)constant, exponentially declining, and quenched SFH scenarios. For each galaxy,we select theoretical ratios from CLOUDY models between [CII] line emission,tracing PDRs, and nebular lines from HII regions, using these to deriveexpected optical/UV lines from observed [CII]. We find binary stars stronglyimpact line emission post-quenching, keeping UV photon flux higher for longer,maintaining free electron temperature and ionised column density in HII regionsup to 5 Myr after quenching. We constrain ISM properties of our subsample,finding a low ionisation parameter \log U{~}-3.8\pm 0.2 andmoderate/high densities \log(n/\rm cm^{-3}){~}2.9\pm 0.6. Finally, wederive UV/optical line luminosities-SFR relations for different burstinessparameters (k_s). In the fiducial BPASS model, relations show negligible SFHdependence but depend on k_s, while in the SB99 case, dependence is on SFH.We propose their use for characterising the burstiness of high-z galaxies.