High-velocity outflows in [OIII] emitters at z=2.5-9 from JWST NIRSpec medium-resolution spectroscopy

Ryan A. Cooper, Karina I. Caputi, Edoardo Iani, Pierluigi Rinaldi, Guillaume Desprez, Rafael Navarro-Carrera

First listed 2025-02-25 | Last updated 2025-02-26

Abstract

We identify galaxies hosting ionised-gas high-velocity outflows from the complete sample of medium resolution (R1000) JWST/NIRSpec MSA spectroscopy taken as part of the JWST Advanced Deep Extragalactic Survey (JADES). From a total sample of 1087 [OIII]5007 emitters we identify 40 galaxies with a blue-side broadened [OIII]5007 line at z=2.5-9. Of these, 34 are strong outflow candidates whilst 6 sources have broadening potentially driven by rotating clumps. Our outflow candidate sample is mainly composed of star-forming galaxies, including ~65% starbursts, which span the stellar mass range log10(M*/Msun)=7.5-11.0. It also includes two candidate type-2 active galactic nuclei (AGN) and a 'little red dot' (LRD). We report a median outflow velocity of 531(+146)(-159) km/s and an overall incidence rate of 3.4%. These values are significantly higher and lower respectively than recent similar works, which we accredit to the limiting resolution of the R1000 spectroscopy and a stricter outflow selection criterion. We find no correlation between the outflow velocity and the galaxy stellar mass or star-formation rate. The median ratio between outflow velocity and escape velocity is 0.77(+0.36)(-0.32), indicating that most outflows cannot escape the galaxy gravitational potentials. We do find an anti-correlation between mass loading factor and stellar mass up to M* ~(10^10)Msun, with most lowest stellar-mass M*<(10^9)Msun galaxies reaching values well above unity, as is the case for local starburst galaxies.

Short digest

From the full JADES NIRSpec R~1000 sample of 1087 [O III] 5007 emitters at z=2.5–9, the authors flag 40 galaxies with clear blue-side line broadening, of which 34 are robust ionized outflow candidates and 6 may reflect rotating clumps. The outflows occur mostly in star-forming systems (~65% starbursts) spanning log10(M*/Msun)=7.5–11, and include two type-2 AGN candidates plus one little red dot. They measure a median outflow velocity of 531(+146/−159) km/s and a global incidence of 3.4%, higher velocities and lower incidence than prior work, attributed to R1000 resolution and stricter selection. No v_out–M* or SFR correlations are found; v_out/v_esc has a median 0.77 (generally bound), while mass loading anti-correlates with M* up to ~10^10 Msun, exceeding unity in many M*<10^9 Msun galaxies.

Key figures to inspect

• Figure 3: Inspect the [O III] 5007 profile for JADES-GN+189.11339-62.22768 to see the asymmetric blue wing and how adding a broad Gaussian component reduces residuals—key for understanding the outflow identification and typical broad-component widths/offsets.
• Figure 4: Outflow velocity versus redshift with morphology-coded symbols; check where the two type-2 AGN candidates and the LRD fall relative to the star-forming sample and to literature points (Xu23, Ca24), and whether the highest velocities cluster at any z or morphology.
• Figure 2: S/N distribution of all [O III] emitters versus the outflow subset; use this to gauge completeness and the effective S/N>5 threshold where blue-wing detections become reliable.
• Figure 1: Comparison of [O III] fluxes (MSAEXP vs JADES catalog); verify flux calibration consistency that underpins line-profile fitting and derived outflow velocities/mass-loading estimates.