Kavli Affiliate: Roberto Maiolino
| First 5 Authors: Gareth C. Jones, Andrew J. Bunker, Kseniia Telikova, Santiago Arribas, Stefano Carniani
| Summary:
We present observations of the $zsim5.7$ Lyman-break galaxy HZ10 with the
JWST/NIRSpec IFU in high and low spectral resolution (G395H, $Rsim2700$ and
PRISM, $Rsim100$, respectively), as part of the GA-NIFS program. By spatially
resolving the source, we find evidence for three spatially and spectrally
distinct regions of line emission along with one region of strong continuum
emission, all within a projected distance of $<10$kpc. The R2700 data features
strong detections in H$beta$, [OIII]$lambdalambda4959{,}5007$,
[NII]$lambdalambda6548{,}6584$, H$alpha$, and
[SII]$lambdalambda6716{,}6731$. The R100 data additionally contains a strong
detection of the Ly$alpha$ break, rest-UV continuum, and
[OII]$lambdalambda3726{,}3729$. None of the detected lines present strong
evidence for AGN excitation from line diagnostic diagrams, and no
high-ionisation lines are detected. Using the detected lines, we constrain the
electron density $left( rm log_{10}left( n_e /
cm^{-3}right)sim2.5-3.3right)$ and metallicity ($sim0.5-0.7$ solar) in each
component. Spaxel-by-spaxel fits of each cube reveal a strong east-west
velocity gradient and significant line asymmetries (indicating tidal features
or outflows). The western component features a very red UV slope
($beta_{UV}sim-1$) and significant H$alpha$ emission, suggesting an evolved
population and active star formation. From a comparison to high resolution
[CII]$158mu$m imaging obtained with the Atacama Large Millimetre/submillimetre
Array (ALMA), we find that the continuum emitter is associated with a gas-poor
stellar population. Altogether, these data suggest that HZ10 represents an
ongoing merger, with a complex distribution of stars, gas, and dust $<1$Gyr
after the Big Bang.
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