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- Title
Extended high-ionization [Mg IV] emission tracing widespread shocks in starbursts seen by JWST/NIRSpec.
- Authors
Pereira-Santaella, Miguel; García-Bernete, Ismael; González-Alfonso, Eduardo; Alonso-Herrero, Almudena; Colina, Luis; García-Burillo, Santiago; Rigopoulou, Dimitra; Arribas, Santiago; Perna, Michele
- Abstract
We report the detection of extended (> 0.5–1 kpc) high-ionization [Mg IV] 4.487 μm (80 eV) emission in four local luminous infrared galaxies observed with JWST/NIRSpec. Excluding the nucleus and outflow of the Type 1 active galactic nucleus (AGN) in the sample, we find that the [Mg IV] luminosity is well correlated with that of H recombination lines, which mainly trace star-forming clumps in these objects, and that the [Ar VI] 4.530 μm (75 eV), usually seen in AGN, is undetected. On 100–400 pc scales, the [Mg IV] line profiles are broader (σ([Mg IV]) = 90 ± 25 km s−1) and shifted (Δv up to ±50 km s−1) compared to those of the H recombination lines and lower ionization transitions (e.g., σ(Hu-12) = 57 ± 15 km s−1). The [Mg IV] kinematics follow the large-scale rotating velocity field of these galaxies, and the broad [Mg IV] profiles are compatible with the broad wings detected in the H recombination lines. Based on these observational results, extended highly ionized gas more turbulent than the ambient interstellar medium, possibly a result of ionizing shocks associated with star formation, is the most likely origin of the [Mg IV] emission. We also computed new grids of photoionization and shock models to investigate where the [Mg IV] line originates. Shocks with velocities of 100–130 km s−1 reproduce the observed line ratios and the [Mg IV] luminosity agrees with that expected from the mechanical energy released by supernove (SNe) in these regions. Therefore, these models support shocks induced by SNe as the origin of the [Mg IV] line. Future studies on the stellar feedback from SNe will benefit from the [Mg IV] line that is little affected by obscuration and, in the absence of an AGN, can only be produced by shocks due to its high ionization-potential.
- Subjects
INTERSTELLAR medium; STAR formation; IONIZED gases; GALACTIC evolution; MECHANICAL energy; ACTIVE galactic nuclei; STARBURSTS
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2024, Vol 685, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/202449982