High [O iii]/[C ii] surface brightness ratios trace early starburst galaxies. Issue 4 (11th June 2021)

• Record Type: Journal Article
• Authors: Vallini, L; Ferrara, A; Pallottini, A; Carniani, S; Gallerani, S
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 505:Issue 4(2021)
• Page Start: 5543
• Page End: 5553
• Publication Date: 2021-06-11
• Subjects: ISM: evolution -- ISM: photodissociation region -- galaxies: high-redshift -- galaxies: ISM -- galaxies: starburst; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab1674
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We study the impact of deviations from the Kennicutt–Schmidt relation (quantified by the 'burstiness' parameter κs ), gas metallicity ( Z ), and density ( n ) on the observed [O iii ]88 μm/[C ii ]158 μm surface brightness ratios (Σ[O iii ] /Σ[C ii ] ) in nine galaxies at z ≈ 6−9. We first discuss possible biases in the measured Σ[O iii ] /Σ[C ii ] ratios by comparing the data with zoom-in cosmological simulations and then use a Markov Chain Monte Carlo algorithm to derive the best-fitting values of (κs, Z, n ). We find that (i) the strongest dependence of Σ[O iii ] /Σ[C ii ] is on κs ; (ii) high ratios identify starburst galaxies with short gas depletion times ($t_{\rm dep}=6-49\, \rm Myr$ ); (iii) a secondary dependence on density is found, with Σ[O iii ] /Σ[C ii ] anticorrelating with n as a result of the lower [O iii ] critical density; and (iv) the ratio weakly depends only on Z . The nine galaxies are significantly enriched ( Z = 0.2−0.5 Z ⊙ ) and dense n ≈ 10 1−3 cm −3 . This lends further support to the starburst scenario in which a rapid enrichment of the interstellar medium is expected.