Kavli Affiliate: John Silverman
| First 5 Authors: Seiji Fujimoto, Seiji Fujimoto, , ,
| Summary:
We present a statistical study of spatially resolved chemical enrichment in
18 main-sequence galaxies at $z=4$–6, observed with jwst/NIRSpec IFU as part
of the ALPINE-CRISTAL-jwst survey. Performing an optimized reduction and
calibration procedure, including local background subtraction, light-leakage
masking, stripe removal, and astrometry refinement, we achieve robust
emission-line mapping on kiloparsec scales. Although line-ratio distributions
vary across galaxies in our sample, we generally find mild central enhancements
in [O,textsciii]/H$beta$, [O,textscii]/[O,textsciii],
[S,textscii]$_6732$/[S,textscii]$_6718$, H$alpha$/H$beta$, and
$L_rm Halpha/L_rm UV$, consistent with elevated electron density, dust
obscuration, and bursty star formation accompanied by reduced metallicity and
ionization parameter. These features point to inside-out growth fueled by
recent inflows of pristine gas. Nevertheless, the median metallicity gradient
is nearly flat over a few kpc scale, $Delta log(rm O/H) = 0.02 pm 0.01$
dex kpc$^-1$, implying efficient chemical mixing through inflows, outflows,
and mergers. From pixel-by-pixel stellar and emission-line characterizations,
we further investigate the resolved Fundamental Metallicity Relation (rFMR).
Metallicity is described by a fundamental plane with stellar mass and SFR
surface densities, but with a stronger dependence on $Sigma_rm SFR$ than
seen in local galaxies. Our results indicate that the regulatory processes
linking star formation, gas flows, and metal enrichment were already vigorous
$sim$1 Gyr after the Big Bang, producing the nearly flat metallicity gradient
and a stronger coupling between star formation and metallicity than observed in
evolved systems in the local universe.
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