We investigate what drives the redshift evolution of the typical electron density (n e ) in star-forming galaxies, using a sample of 140 galaxies drawn primarily from KMOS3D (0.6 < z < 2.6) and 471 galaxies from SAMI (z < 0.113). We select galaxies that do not show evidence of active galactic nucleus activity or outflows to constrain the average conditions within H ii regions. Measurements of the [S ii]λ6716/[S ii]λ6731 ratio in four redshift bins indicate that the local n e in the line-emitting material decreases from 187-132+140 cm-3 at z ∼ 2.2 to 32-9+4 cm-3 at z ∼ 0, consistent with previous results. We use the Hα luminosity to estimate the rms n e averaged over the volumes of star-forming disks at each redshift. The local and volume-averaged n e evolve at similar rates, hinting that the volume filling factor of the line-emitting gas may be approximately constant across 0 ≲ z ≲ 2.6. The KMOS3D and SAMI galaxies follow a roughly monotonic trend between n e and star formation rate, but the KMOS3D galaxies have systematically higher n e than the SAMI galaxies at a fixed offset from the star-forming main sequence, suggesting a link between the n e evolution and the evolving main sequence normalization. We quantitatively test potential drivers of the density evolution and find that n e (rms) nH2, suggesting that the elevated n e in high-z H ii regions could plausibly be the direct result of higher densities in the parent molecular clouds. There is also tentative evidence that n e could be influenced by the balance between stellar feedback, which drives the expansion of H ii regions, and the ambient pressure, which resists their expansion.

The KMOS3D Survey: Investigating the Origin of the Elevated Electron Densities in Star-forming Galaxies at 1 ≲ z ≲ 3 / Davies R.L.; Schreiber N.M.F.; Genzel R.; Shimizu T.T.; Davies R.I.; Schruba A.; Tacconi L.J.; Obler H.; Wisnioski E.; Wuyts S.; Fossati M.; Herrera-Camus R.; Lutz D.; Mendel J.T.; Naab T.; Price S.H.; Renzini A.; Wilman D.; Beifiori A.; Belli S.; Burkert A.; Chan J.; Contursi A.; Fabricius M.; Lee M.M.; Saglia R.P.; Sternberg A.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 909:1(2021), pp. 78.1-78.25. [10.3847/1538-4357/abd551]

The KMOS3D Survey: Investigating the Origin of the Elevated Electron Densities in Star-forming Galaxies at 1 ≲ z ≲ 3

Renzini A.;Belli S.;
2021

Abstract

We investigate what drives the redshift evolution of the typical electron density (n e ) in star-forming galaxies, using a sample of 140 galaxies drawn primarily from KMOS3D (0.6 < z < 2.6) and 471 galaxies from SAMI (z < 0.113). We select galaxies that do not show evidence of active galactic nucleus activity or outflows to constrain the average conditions within H ii regions. Measurements of the [S ii]λ6716/[S ii]λ6731 ratio in four redshift bins indicate that the local n e in the line-emitting material decreases from 187-132+140 cm-3 at z ∼ 2.2 to 32-9+4 cm-3 at z ∼ 0, consistent with previous results. We use the Hα luminosity to estimate the rms n e averaged over the volumes of star-forming disks at each redshift. The local and volume-averaged n e evolve at similar rates, hinting that the volume filling factor of the line-emitting gas may be approximately constant across 0 ≲ z ≲ 2.6. The KMOS3D and SAMI galaxies follow a roughly monotonic trend between n e and star formation rate, but the KMOS3D galaxies have systematically higher n e than the SAMI galaxies at a fixed offset from the star-forming main sequence, suggesting a link between the n e evolution and the evolving main sequence normalization. We quantitatively test potential drivers of the density evolution and find that n e (rms) nH2, suggesting that the elevated n e in high-z H ii regions could plausibly be the direct result of higher densities in the parent molecular clouds. There is also tentative evidence that n e could be influenced by the balance between stellar feedback, which drives the expansion of H ii regions, and the ambient pressure, which resists their expansion.
2021
The KMOS3D Survey: Investigating the Origin of the Elevated Electron Densities in Star-forming Galaxies at 1 ≲ z ≲ 3 / Davies R.L.; Schreiber N.M.F.; Genzel R.; Shimizu T.T.; Davies R.I.; Schruba A.; Tacconi L.J.; Obler H.; Wisnioski E.; Wuyts S.; Fossati M.; Herrera-Camus R.; Lutz D.; Mendel J.T.; Naab T.; Price S.H.; Renzini A.; Wilman D.; Beifiori A.; Belli S.; Burkert A.; Chan J.; Contursi A.; Fabricius M.; Lee M.M.; Saglia R.P.; Sternberg A.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - STAMPA. - 909:1(2021), pp. 78.1-78.25. [10.3847/1538-4357/abd551]
Davies R.L.; Schreiber N.M.F.; Genzel R.; Shimizu T.T.; Davies R.I.; Schruba A.; Tacconi L.J.; Obler H.; Wisnioski E.; Wuyts S.; Fossati M.; Herrera-Camus R.; Lutz D.; Mendel J.T.; Naab T.; Price S.H.; Renzini A.; Wilman D.; Beifiori A.; Belli S.; Burkert A.; Chan J.; Contursi A.; Fabricius M.; Lee M.M.; Saglia R.P.; Sternberg A.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/953115
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