2026/02/20 by Steven Gillman, Kei Ito, Francesco Valentino +24 · 1 voice
Physics and Astronomy · #astro-ph.GA
We present a detailed study of near-infrared (2-4\rm μm) JWST/NIRSpec spectra of 48 high-redshift (z=2.53+1.32-0.70) galaxies detected with ALMA at >3σ. From a multi-wavelength SED analysis we establish the sample has a a median stellar mass of \rmlog10(M_∗/M_\odot)=10.8±0.1 and dust mass of \rmlog10(M\rm d/M_\odot)=8.7±0.1, covering a broad range of far-infrared luminosity \rm (log10(LFIR/L_\odot)=10.9-12.7). The majority of sources show no signs of AGN activity, with 40% having either X-ray counterparts (\rm LXc>1042erg/s), elevated optical line ratios, or broad (FWHM>800 km/s) Hα profiles, although we note this is a lower limit due to the stochastic placement of NIRSpec slits. We establish the sample has a median gas-phase metallicity of 12+log(\rm O/H)=8.71±0.02, as derived from the [NII]/Hα ratio, with the most FIR-luminous galaxies (\rmlog10(L\rm FIR/L_\odot)>12) falling 0.15±0.03dex above the fundamental metallicity relation. From the [SII] emission-line doublet ratio, we measure a median electron density of log10(n\rm e/\rm cm-3)=2.53±0.07 consistent with less-massive, star-forming, galaxies at the same epoch. For nine galaxies with [OII] and Hβ detections (median \rmlog10(L\rm FIR/L_\odot)=11.81±0.15), we derive a median observed (dust-uncorrected) ionisation parameter of \rmlog10(U)=-2.84±0.06. Our results indicate that luminous far-infrared galaxies are massive, chemically evolved systems that appear to deviate from the standard dust and metal production equilibrium observed in less obscured galaxies. This study demonstrates the synergy of JWST and ALMA in unveiling the nature of DSFGs, and highlights the need for a NIRSpec survey of uniformly selected, massive, dust-obscured, galaxies to fully characterise their interstellar medium.